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One-Pot Synthesis of Menthol Starting from Citral over Ni Supported on Attapulgite-H-Beta-38 Extrudates in a Continuous Flow: Effect of Metal Location
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Kinetics, Catalysis, and Reaction Engineering

One-Pot Synthesis of Menthol Starting from Citral over Ni Supported on Attapulgite-H-Beta-38 Extrudates in a Continuous Flow: Effect of Metal Location
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  • Irina L. Simakova
    Irina L. Simakova
    Boreskov Institute of Catalysis, pr. Ak. Lavrentieva 5, Novosibirsk, Russia 630090
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    Orcidhttps://orcid.org/0000-0002-5138-4847
  • Päivi Mäki-Arvela
    Päivi Mäki-Arvela
    Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
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    Orcidhttps://orcid.org/0000-0002-7055-9358
  • Mark Martínez-Klimov
    Mark Martínez-Klimov
    Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
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  • Joseph Muller
    Joseph Muller
    Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
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  • Zuzana Vajglová
    Zuzana Vajglová
    Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
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  • Markus Peurla
    Markus Peurla
    Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
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  • Kari Eränen
    Kari Eränen
    Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
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  • Dmitry Yu. Murzin*
    Dmitry Yu. Murzin
    Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0003-0788-2643
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Cite this: Ind. Eng. Chem. Res. 2022, 61, 35, 12998–13010
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https://doi.org/10.1021/acs.iecr.2c02345
Published August 25, 2022

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Abstract

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The one-pot synthesis of menthol from citral in a continuous mode was investigated over three different types of extrudates, namely Ni supported on H-Beta-38 and extruded with attapulgite, Ni supported on attapulgite and extruded with H-Beta-38, and the extrudates, which were shaped after deposition of Ni on both H-Beta-38 and attapulgite in the powder form. These composite catalysts were characterized by X-ray diffraction, transmission and scanning electron microscopy, temperature-programmed reduction of H2, mechanical strength, and pyridine adsorption desorption. These three types of extrudates exhibited different metal particle sizes and acidity. The most promising catalyst in the one-pot menthol synthesis was Ni supported first on H-Beta-38 and then extruded with attapulgite giving a 45% yield of menthols in a trickle bed reactor. This catalyst exhibited 10 nm nickel particles and a rather high amount of strong Brønsted acid sites.

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1. Introduction

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Menthol is an important product used in pharmaceuticals including mouthwash, toothpaste, chewing gum, tobacco, candy, and cosmetics. (1) It is obtained from peppermint and cornmint oil, and it is also produced synthetically starting from thymol or myrcene. (2) The one-pot synthesis of menthol from citronellal has been intensively investigated using both supported noble (3−9) and transition metal catalysts. (10−13) The highest yields of menthols in a batch reactor have been obtained over Ni/Zr-Beta catalysts giving the menthol yield of 86–97%. (11) In ref (11), citronellal transformations to isopulegol were performed first under helium atmosphere, followed by hydrogenation. An analogous strategy was used in ref (13) reporting 86% yield of menthol under 1 bar hydrogen at 90 °C starting from citronellal. Menthol synthesis from citral (Figure 1), which is also a naturally occurring compound, obtained especially from lemongrass oil, has been scarcely studied. (2,14−19) Mainly such a one-pot synthesis of menthol from citral has been investigated in batch reactors with the best results reported for Ni-supported catalysts. (2) The highest menthol yield, 94%, was obtained in a batch reactor over 8 wt % Ni/Al-MCM-41 at 70 °C and 20.2 bar hydrogen. (14) In the previous work of the authors, it was demonstrated that Ru containing catalysts in the form of extrudates can be used in the one-pot synthesis of menthol in a trickle bed reactor. (17,18) These catalysts were not, however, selective toward menthol formation. For example, Ru-MCM-41 and Ru-H-Y-80 gave maximally 6% menthol yields, while defunctionalized menthane derivatives were the major products. (17,18)

Figure 1

Figure 1. Reaction scheme for citral transformation to menthol. Legend: A – citral, B – citronellal, C – isopulegol isomers, D – menthol isomers, E – acyclic hydrogenation products, F – defunctionalization products, dimeric ethers, and heavy components.

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Encouraged by the promising results in a batch reactor with supported bifunctional nickel catalysts, (2,14) the aim in this work was to demonstrate menthol production in a trickle bed reactor over Ni extrudates. The authors have recently demonstrated the suitability of Ni-H-Beta-38 sepiolite extrudates (the number denotes the Si/Al ratio) as catalysts in the one-pot synthesis of menthol starting from citronellal and citral. (20) This Ni-H-Beta-38-sepiolite catalyst prepared by impregnation of extrudates and subsequently having Ni located both on H-Beta-zeolite and sepiolite gave a 49% yield of menthols and 72–74% stereoselectivity. Furthermore, continuous transformation of citral over Ni supported on a mesoporous aluminosilicate using sepiolite as a binder at 70 °C was reported giving 75% selectivity to menthols. (21)
In the current work, Ni containing extrudates composed of H-Beta-38 zeolite and attapulgite clay as a binder alternative to sepiolite (20) were prepared, characterized, and tested in one-pot transformation of citral to menthol in a trickle bed reactor. A bifunctional catalyst with suitable acidity and a metal particle size is required for selective synthesis of menthol from citral as follows from data generated in a batch reactor. (14) Beta zeolite with the Si/Al ratio of 25 has been a promising support for Ni in citral transformations to menthol in that study; (14) thus, a commercially available acidic H-Beta-38 was selected as a support together with attapulgite as a binder for citral transformation to menthols. Attapulgite, a naturally occurring magnesium aluminum silicate clay mineral with the chemical formula [(Mg,Al)4Si8(O, OH, H2O)24·nH2O], (22) exhibits a chain layered crystal structure and a large specific surface area. (23) Attapulgite being typically mildly acidic is often applied as a binder for extrusion and has been also successfully used as a support per se for nickel in the hydrogenation of maleic anhydride (24) and vegetable oil. (25)
Although clays have been used as binders in extrudates with the main purpose to ensure the mechanical strength and stability of the extrudates, different binders exhibit different Si/Al ratios, hydrophobicity, and textural properties, being not necessarily inert in terms of their catalytic behavior. (29) Furthermore, it was shown in ref (29) that different optimum amounts of water are required to make extrudates from various clays. Taking into account all these parameters, it cannot be predicted beforehand how exactly a composite material comprising Ni supported on attapulgite-H-Beta-38 will work in a complex reaction, citral transformation to menthol.
The aim of this work was to prepare composite catalysts in the extrudate form using three different methods: loading on extrudates prepared from a mixture of H-Beta-38 and attapulgite or alternatively depositing Ni either on attapulgite and extruded with H-Beta-38 or loading of Ni on H-Beta-38 and extruding it with attapulgite. The importance of metal location in extrudates has been earlier emphasized especially in citral transformation to menthol, (20) and the hydroisomerization reaction in refs (26−28) and the close proximity of a metal and an acid site have been found to be of crucial importance in selective hydroisomerization. Furthermore, it was recently observed in citral transformations to menthols that even with the same catalyst in the powder and in extrudate forms different product distributions were obtained in batch and continuous reactors. (18) There is apparently a lack of experimental data for other reactions of a similar type involving the central metal and acid, such as the one-pot synthesis of menthol in a continuous reactor with extruded catalysts, and it is difficult to predict the product distribution in advance for the bifunctional extrudates, because several physicochemical processes occur during production of extrudates including the mechanical impact already during preparation of a suspension for extrusion.
Ni-H-Beta-38-sepiolite composite catalysts have been already tested in citral transformation to menthols. (20) In the current work, Ni-H-Beta-38-attapulgite composite catalysts were investigated in the same reaction under comparative conditions in a trickle bed reactor. The main differences in attapulgite and sepiolite are the higher amount of magnesium and traces of K in the latter one, while on the other hand, attapulgite contained various impurities, such as K, Fe, P, and Ca. Both clays exhibited a fibrous structure; however, the fibers in sepiolite were slightly longer and thicker in comparison to attapulgite fibers. (29) The Ni-H-Beta-H-attapulgite composite catalysts in the current work were characterized by determining their structure, acidity, and specific surface area of the metal particle size distribution to find a correlation between the catalyst properties and their performance in the one-pot synthesis of menthol. Furthermore, mechanical strength of the prepared extrudates containing attapulgite as a binder was also determined showing promising results.

2. Experimental Section

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2.1. Synthesis of Catalysts

Three different modes of Ni introduction by the incipient wetness impregnation were implemented: deposition on H-Beta-38 followed by extrusion with attapulgite, introduction of attapulgite followed by extrusion with H-Beta-38, or nickel deposition on the extrudates prepared from a suspension of H-Beta-38 and attapulgite. For preparation of Ni-bearing extrudates where Ni is deposited on both H-Beta-38 and attapulgite, the commercial H-Beta-38 (SiO2/Al2O3 = 38) zeolite (Zeolyst International) as an active phase and attapulgite as a binder were ground, dried overnight at 100 °C, and mixed in the mass ratio = 70/30, e.g., 4.2 and 1.8 g, respectively. Methylcellulose (1.0 wt %, e.g., 0.06 g) as an organic binder (viscosity: 4000 cP, Sigma-Aldrich) was dissolved in 3 mL of water and added into the mixture to control the rheological properties of the final slurry. Distilled water was added gradually into the suspension under constant stirring at room temperature until a soft elastic paste was prepared. The extrudates were fabricated in a cylindrical shape with a diameter of 1.4 mm using the extruder (TBL-2, Tianjin Tianda Beiyang Chemical Co. Ltd., China) at an ca. 12 cm/min extrusion rate driven by the rotational velocity of 1400 rpm. Subsequently, the extrudates were dried in an oven at 100 °C overnight, calcined at 500 °C for 4 h in a muffle oven, and cut to a length of ca. 0.6–1.0 cm. The obtained extrudates were impregnated by a nickel nitrate Ni(NO3)2·6H2O (CJSC Souzchimprom) aqueous solution to achieve the nominal nickel loading 5 wt %. Thereafter, Ni-bearing extrudates were dried overnight at 100 °C followed by calcination at 450 °C for 6 h in a muffle oven.
For the preparation of Ni-containing extrudates where Ni was deposited on H-Beta-38 or on attapulgite, the ground and dried zeolite or the binder, respectively, in the powder form was impregnated with the nickel nitrate Ni(NO3)2·6H2O aqueous solution to achieve the nominal metal loading 5 wt % Ni in the final catalyst. Thereafter, the suspension was dried at 100 °C overnight and calcined at 450 °C for 6 h in a muffle oven to decompose nickel nitrate. Then, the calculated amounts of attapulgite or H-Beta-38, respectively, as well as methylcellulose (1.0 wt %, 0.06 g) dissolved in 3 mL of water were mixed with a Ni-containing powder at a room temperature. Distilled water was added gradually under constant stirring at room temperature until a soft elastic paste was prepared for extrudate fabrication according to the above-mentioned procedure. The extrudates were dried overnight at 100 °C and then calcined at 500 °C for 4 h in a muffle oven.
Before each catalytic experiment, all Ni catalysts were reduced in situ in a 100 mL/min hydrogen flow at 350 °C during 2.5 h with the 2 °C/min temperature ramp.

2.2. Characterization of Catalysts

Textural properties of the catalysts were determined using nitrogen physisorption (Micrometrics 3Flex-3500). The specific surface area and pore volumes were determined using Dubinin–Radushkevich or Brunauer–Emmett–Teller (BET) and density functional theory (DFT) methods, respectively. Prior to measurements, the catalysts were outgassed ex situ under vacuum at 180 °C for 20–24 h in a Micromeritics VacPrep 061 Sample Degas System followed by in situ outgassing for 4 h at 180 °C.
The amount and strength of Brønsted and Lewis acid sites were determined by Fourier transform infrared spectroscopy using pyridine (≥99.5%) as the probe molecule (with ATI Mattson FTIR Infinity Series spectrometer). The catalyst used in acidity measurements was calcined. The quantification of acid sites was performed using the molar extinction parameters reported by Emeis. (30)
Powder XRD patterns were obtained on a Bruker D8 Advance diffractometer (Cu Kα radiation, λ = 0.15418 nm) equipped with a LynxEye position sensitive detector. The data were collected in the 2θ range of 5°–65° with a step of 0.05° and a collection time of 3 s. The phase identification was performed using the ICDD PDF-2 database. (31) The average crystallite size of phases was calculated by the line broadening analysis according to the Scherrer equation. Scanning electron microscopy (SEM) was utilized to obtain information on the morphology of the binder, H-Beta-38, and the extruded catalysts. A Zeiss Leo Gemini 1530 microscope combined with secondary electron and backscattered electron detectors was applied. The X-ray analysis was performed with an acceleration voltage of 15 kV.
Transmission electron microscopy (TEM) was utilized to determine the metal particle size and study morphology and porosity. The equipment used for analysis was a JEM-1400Plus (JEOL, Japan) with a maximal acceleration voltage of 120 kV. The ImageJ program was used to interpret TEM images and determine particles sizes of the fresh and spent catalysts. Prior to the TEM measurements, the extrudates were ground and suspended in ethanol. A drop of a suspension was mounted on a copper grid coated with a carbon film, and the solvent evaporated. For calculation of the metal particle size distribution, the diameter (d) of more than 300 particles was determined in TEM micrographs.
Ni content was determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) using PerkinElmer Optima 5300 DV.
Hydrogen TPR experiments were performed with a Micromeritics Belcat II instrument. For a measurement, the catalyst was dried prior to an experiment under an argon flow using a temperature program of 25 °C-2 °C/min-120 °C (60 min). Thereafter, it was reduced using 5 vol % hydrogen in argon with the following temperature program: 25 °C-2 °C/min-350 °C (150 min). Hydrogen was analyzed using the thermal conductivity detector, and water was removed using a molecular sieve trap.
The mechanical strength of the extruded samples was estimated by the crush tester (SE 048, Lorentzen & Wettre) both in horizontal and vertical positions as it was described in our previous publications. (32) For, e.g., the vertical crushing test, the cylindrical extrudate with a diameter of 1.4 mm and a length of 10 mm was inserted in between the two anvils of the crush tester, and then the load was applied along the vertical direction of the extrudate until it exhibited a failure. The maximum applied load was recorded, and after 10 extrudates were measured, the average value of their maximum applied loads was calculated as the sample mechanical strength.

2.3. Catalyst Testing

The experiments were carried out in a continuous trickle bed reactor (the internal diameter 1.25 cm, the reactor volume ∼ ca. 15 cm3). (18) Quartz wool was placed at the bottom of the reactor followed by 1 g of extrudates. The inert quartz beads of the size 0.2–0.8 mm (∼15 g) were placed into the voids completely filling the reactor. The citronellal (Sigma-Aldrich, ≥95.0 wt %) and citral (cis/trans isomer ∼1/1, ≥95.0%, Sigma-Aldrich) solution in cyclohexane (0.086 M) was fed into the reactor with a feeding rate varying in the range of 0.2–0.4 mL min–1, while the hydrogen flow rate was 100 mL min–1.
Analysis of the reaction components was carried out using an Agilent GC 6890 N supplied with a DB-1 column (30 m × 250 μm × 0.5 μm), FID (340 °C). The temperature program included two steps: 1) from 110 to 130 °C with the temperature ramp of 0.4 °C min–1 and 2) from 130 to 200 °C with a temperature ramp of 13 °C min–1. Identification of the reaction compounds was carried out by GC/MS with an Agilent GC/MS 6890 N/5973 using the same temperature program and column. Before analysis, the samples were diluted with cyclohexane (solvent) according to the procedure described in ref (18).

3. Results and Discussion

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3.1. Catalyst Characterization

Attapulgite exhibits according to the elemental analysis the SiO2/Al2O3 ratio of 9 with the following amounts of different elements: 22 wt % Si, 5 wt % Al, and 6 wt % Mg as well as 2 wt % Fe, 1 wt % Ca, 0.2 wt % P, and 0.5 wt % K. This is in accordance with the results of ref (29) also reporting that attapulgite typically contains besides silica also rather large amounts of Mg(II), Al(III), and Fe(III).
The results from Ni content determination by ICP in the fresh and spent extrudates showed that Ni leaching was 5.9% from the initial Ni content in the spent [(Ni/H-Beta-38)+Att.], while it was 12.5% from the spent [(Ni/Att)+H-Beta-38] catalyst indicating weaker interactions of Ni with attapulgite in comparison to H-Beta-38 (Table 1).
Table 1. Ni Content for Fresh and Spent Composite Catalysts Determined by ICP Analysis and Textural Properties of Powder Clay and Extrudatesc
   extrudates
entrysampleNi content [wt %]SBET [m2/g]SDR [m2/g]V [cm3/g]Vm/VμDpore [nm]
1H-Beta-38 (20)n.d.n.a.5900.310.350.67
2attapulgite (powder)n.d.1031170.256n.d.
 attapulgite (extrudate)n.d.971160.3712n.d.
3[Ni/(H-Beta-38+Att.)]5.14045280.390.73n.d.
4[Ni/(H-Beta-38+Att.)] spentan.a.2062670.231.07n.d.
5[(Ni/H-Beta-38)+Att.]5.13044070.310.800.66
6[(Ni/H-Beta-38)+Att.] spentb4.81932460.221.200.63
7[(Ni/Att.)+H-Beta-38]4.83554600.320.630.66
8[(Ni/Att.)+H-Beta-38] spentb4.21772190.181.10.63
a

This catalyst was used first in citronellal transformation; thereafter, it was reduced in situ and used in citral transformation.

b

These catalysts were only used in citral transformation.

c

A – specific surface area (BET: Brunauer–Emmett–Teller, DR: Dubinin-Radushkevich), V – pore volume (m: meso, μ: micro). n.d. not determined, n.a. not available.

The specific surface areas and the pore sizes were determined for H-Beta and attapulgite as well as for three composite catalysts (Table 1). The BET specific surface area of attapulgite is 103 m2/gcat which is quite close to the one reported in ref (33). Furthermore, the ratio between its meso- and micropores was 12, while it was 16.8 in ref (33). In addition, the Dubinin–Radushkevich method (DR) method was also used to estimate the specific surface area and the pore size (Table 1). The BET specific surface area of attapulgite in ref (23) was slightly higher, 188 m2/gcat; however, the origin of attapulgite was not given.
In Ni extrudates, a fully comparative analysis of the fresh and spent catalysts was done for [(Ni/H-Beta-38)+Att.] and [(Ni/Att.)+H-Beta-38] which were both applied in citronellal and citral transformations. The former spent catalyst exhibited 60% of the specific surface area of the fresh one determined by the DR method, while for [(Ni/Att.)+H-Beta-38], the corresponding value was only 48%. Analogous trends were observed for a decrease in the pore volume. These results indicate clearly that the catalyst with weaker interactions between the metal and the acid sites, when Ni is loaded on attapulgite, was deactivated more extensively than the one with Ni located on H-Beta-38. This result is also in accordance with the catalytic results for citral transformation (see below).
The amount of Brønsted and Lewis acid sites as well as their strengths is given in Table 2. Attapulgite exhibits only mild acidity, and no strong acid sites were present (Table 2). The absence of strong acid sites in the clay material can be attributed to the weak framework interactions of tetrahedral aluminum species. On the contrary, 6-fold more Lewis than Brønsted acid sites were observed for attapulgite. When calculating the acidity for 70% H-Beta-38–30 wt % attapulgite and comparing these values with the measured sample (Table 2, entries 3 and 4), it can be seen that although the total acidities were close to each other, the amount of Brønsted acid sites was decreased, and the opposite was observed for Lewis acid site concentration in the real sample showing that the acidity is not a linear function on composition. The most acidic extrudates were [Ni/(Beta-38+Att.)] followed by [(Ni/Beta-38+Att.)], and the lowest total acidity was obtained for [(Ni/Att.)+Beta-38]. When, however, the Ni precursor was first loaded on H-Beta-38 and then extruded, it exhibited a lower BAS/LAS ratio than the one in which Ni was loaded simultaneously on both H-Beta-38 and attapulgite. This result indicates that Ni blocked some acidic sites on H-Beta-zeolite. Interestingly also the BAS/LAS ratio was enhanced in the spent catalyst. It should be pointed out here that the measured amount of Lewis acid sites might be slightly higher in the calcined catalysts than those reduced and used in the reaction in the presence of metallic nickel, because it is known that metal oxides exhibit Lewis acidity. (34,35) However, for the comparative purposes, the same type of methodology was used for determination of acidity as in ref (20).
Table 2. Brønsted and Lewis Acid Sites of Clay Materials
  BAS [μmol/g]LAS [μmol/g]  
no.samplewms∑Wms∑TAS [μmol/g]BAS/LAS
1attapulgite1506278034400.2
2H-Beta-38174022127819102313099
370 wt % H-Beta-38 + 30 wt % Att.a12291551962191311866
470 wt % H-Beta-38 + 30 wt % Att.b15454210239209681701.5
5[Ni/(H-Beta-38+Att.)]131935679633261552220.43
6[(Ni/H-Beta-38)+Att.]2522681159727431672820.69
7[(Ni/Att.)+H-Beta-38]94844101623891092100.93
8[Ni/(H-Beta-38+Att.)] spent10617917381152060.79
9[(Ni/Att.)+H-Beta-38] spent14721710344315801831.29
a

Theoretical value calculated as the weight-average.

b

Measured.

The most acidic catalyst was the one in which Ni was first supported on H-Beta-38 and then extruded with 30 wt % attapulgite followed by the catalyst when Ni was deposited on a composite extrudate [Ni/(H-Beta-38+Att.)], while the lowest acidity was recorded for [(Ni/Att.)+H-Beta-38]. On the other hand, the highest Brønsted to Lewis acid ratio (BAS/LAS) was observed for the latter catalyst with a small amount of H-Beta-38.
Calcined, freshly reduced, and spent [Ni/(H-Beta-38+Att.)], [(Ni/H-Beta-38)+Att.], and [(Ni/Att.)+H-Beta-38] extrudates were studied by powder X-ray diffraction (Figure S2, Figure 2).

Figure 2

Figure 2. XRD patterns of a) the calcined (c.), freshly reduced (r), and spent (s) [Ni/(H-Beta-38+Att.)] extrudates compared to the initial H-Beta-38 zeolite and b) the spent [Ni/(H-Beta-38+Att.)], [(Ni/H-Beta-38)+Att.], and [(Ni/Att.)+H-Beta-38] extrudates compared to the initial H-Beta-38 zeolite. Notation: spent [Ni/(H-Beta-38+Att.)] was used first in citronellal transformation; thereafter, it was reduced in situ and used in citral transformation, while spent [(Ni/H-Beta-38)+Att.] and [(Ni/Att.)+H-Beta-38] extrudates were only used in citral transformation.

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The XRD patterns of the reduced and spent [Ni/(H-Beta-38+Att.)] compared to the XRD patterns of the zeolite and calcined nonreduced [Ni/(H-Beta-38+Att.)] are depicted in Figure 2a.
The XRD pattern of the reduced [Ni/(H-Beta-38+Att.)] catalyst contains peaks from the phase of metallic nickel Ni0 (PDF No. 04-0850, a = b = c = 3.524 Å) with an average CSD size DNi = 14.5 nm (Table 3, entry 2); the determined value of the lattice parameter is a = 3.524 Å. The XRD pattern of the sample also contains peaks from the nickel oxide phase NiO (PDF No. 047-1049, a = b = c = 4.177 Å) with an average CSD size DNiO = 11.5 nm; the determined value of the lattice parameter is a = b = c = 4.181 Å. This lattice parameter is slightly larger than the one for the corresponding calcined sample (Table 3, entries 1, 2) which has also a smaller NiO particle size. This result is in accordance with thermodynamics, because the lattice size increases with a decreasing particle size due to the combined higher interfacial energy and mutual surface tension attractions of the smaller particles. (36) Additional peaks in the region of 2θ = 20 and 35° are attributed to the presence of magnesium silicate phases, characteristic for attapulgite Mg4Si6O15(OH)2(H2O)6 (PDF No. 04-016-3203) and mixed silicate MgAlSi4O10 (OH)(H2O)4 (PDF No. 04-013-5980). It is worth noting that the spent [Ni/(H-Beta-38+Att.)] catalyst contains only the Ni0 phase with the CSD size DNi = 13.0 nm (Table 3, entry 3), while the presence of the nickel oxide phase is not observed indicating that in situ reduction of surface nickel species into the zero valence state was efficient.
Table 3. NiO and Ni Particle Sizes Determined by XRD and TEMb
  XRDTEM
entrysampleDNiO (nm)a (Å)DNi0 (nm)a (Å)D (nm)
1[Ni/(H-Beta-38+Att.)] calcined18.04.180n.d.n.d.n.d.
2[Ni/(H-Beta-38+Att.)] reduced11.54.18114.53.524n.d.
3[Ni/(H-Beta-38+Att.)] spentn.d.n.d.13.03.523n.d.
4[(Ni/H-Beta-38)+Att.] calcined19.04.180n.d.n.d.n.d.
5[(Ni/H-Beta-38)+Att.] reducedn.d.n.d.n.d.n.d.9.8
6[(Ni/H-Beta-38)+Att.] spentn.d.n.d.18.03.524n.d.
7[(Ni/Att.)+H-Beta-38] calcined12.04.178n.d.n.d.n.d.
8[(Ni/Att.)+H-Beta-38] reducedn.d.n.d.n.d.n.d.6.2a
9[(Ni/Att.)+H-Beta-38] spent10.04.1829.03.524n.d.
a

Difficult to separate nickel and impurity particles in attapulgite.

b

Spent [Ni/(H-Beta-38+Att.)] was used first in citronellal transformation; thereafter, it was reduced in situ and used in citral transformation, while the spent [(Ni/H-Beta-38)+Att.] and [(Ni/Att.)+H-Beta-38] extrudates were only used in citral transformation. n.d. not determined.

The powder XRD patterns of all spent catalysts, [Ni/(H-Beta-38+Att.)], [(Ni/H-Beta-38)+Att.], and [(Ni/Att.)+H-Beta-38] extrudates, and that of the initial H-Beta-38 zeolite are shown in Figure 2b. According to XRD data, all samples contain the characteristic peaks of the H-Beta-38 zeolite. A narrow maximum at 2θ = 26.6° observed for [Ni/(H-Beta-38+Att.)] and [(Ni/Att.)+H-Beta-38] extrudates was also present in XRD patterns of the corresponding calcined samples (Figure S2), which can be related to the SiO2 quartz phase (PDF No. 00-046-1045) with the CSD size DSiO2 > 100 nm. The zeolite material in the spent samples undergoes minor structural changes during the reaction as indicated by a slight decrease in the intensity of the peaks at 2θ at 7.7 and 13.4°. Additional peaks in the 2θ region of 20° and 35° in the spent [Ni/(H-Beta-38+Att.)] and [(Ni/H-Beta-38)+Att.] similar to that observed in the corresponding nonreduced calcined extrudates are attributed to the presence of magnesium silicate phases. In the spent catalysts where nickel was supported on the zeolite or the zeolite was mixed with attapulgite, [Ni/(H-Beta-38+Att.)], and [(Ni/H-Beta-38)+Att.], only the metallic nickel phase Ni0 was recorded with the corresponding CSD size DNi = 13.0 nm and DNi = 18.0 nm (Table 3, entries 3 and 6), respectively, indicating rather high resistance of the active metal sites to oxidation under reaction conditions. The determined values of the Ni0 lattice parameters for [Ni/(H-Beta-38+Att.)] and [(Ni/H-Beta-38)+Att.] are 3.523 and 3.524 Å, respectively. In the XRD pattern of the sample where Ni was supported on attapulgite [(Ni/Att.)+H-Beta-38], weak peaks from the phase of metallic nickel Ni0 (PDF No. 04-0850) are observed with the estimated CSD size DNi = 9.0 nm (Table 3, entry 9) and the determined value of the lattice parameter of 3.524 Å. Along with metallic nickel Ni0 there is also the nickel oxide phase NiO (PDF No. 047-1049) with the determined value of the lattice parameter a = b = c = 4.182 Å and an average CSD size DNiO = 10.0 nm. The larger lattice parameter of the NiO phase in the spent [(Ni/Att.)+H-Beta-38] together with its smaller NiO size in comparison to the one detected in thermodynamics analogously is observed for the NiO phase in calcined and reduced [(Ni/H-Beta-38)+Att.]. The fraction of the nickel oxide phase in [(Ni/Att.)+H-Beta-38] noticeably dominates over the metallic nickel phase (Figure 5) which can result in its lower hydrogenation ability compared to [Ni/(H-Beta-38+Att.)] and [Ni/H-Beta-38+Att.] characterized by the presence of only the metallic nickel phase.
TEM images of attapulgite, H-Beta-38 and the three different Ni-H-Beta-attapulgite extrudates are shown in Figure 3. Attapulgite has a typical fibrous structure, with some metal particles as impurities (Figure 3a). Attapulgite fibers have a diameter of ca. 25 nm with their lengths varying from 115 to 1200 nm. The size of the metal particles in pure attapulgite is ca. 45 nm. H-Beta-38 has round shaped crystals with the size of 125 nm (Figure 3b). Because pure commercial attapulgite has also metal particles, it is challenging to determine Ni particle size distribution in [Ni/(H-Beta-38+Att.)] and in [(Ni/Att.)+H-Beta-38] (Figure 3c, e). On the other hand, when Ni was first introduced on H-Beta-38, the average Ni particle size can be reliably determined as being 9.8 nm (Figure 3b, Table 3, entry 5).

Figure 3

Figure 3. TEM images of a) attapulgite, b) H-Beta-38, c) [Ni/(H-Beta-38+Att.)], d) [(Ni/H-Beta-38)+Att.], and e) [(Ni/Att.)+H-Beta-38].

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The Ni particle size distribution can be correctly calculated from TEM only for [(Ni/H-Beta-38)+Att.], because Ni was only loaded on round shaped H-Beta particles (Figure 4a) and thereafter dried, calcined, extruded with attapulgite, and reduced. On the other hand, when Ni was loaded for both Beta-30 and attapulgite, Ni particle size distribution cannot be reliably calculated on the attapulgite phase, because Ni particles cannot be clearly differentiated with the impurities present in attapulgite phase. In this case, the particles on attapulgite can be either Ni and other impurities present in attapulgite. The average Ni particle size for reduced [(Ni/H-Beta-38)+Att.] was 9.8 nm (Table 3, entry 5, Figure 4a). The average particle size of Ni for the spent [(Ni/H-Beta-38)+Att.] determined by XRD was 18 nm indicating that some sintering might occur (Table 3, entry 6). However, typically the metal particle size determined by XRD can be larger than determined by TEM, because XRD cannot detect clearly particles below ca. 3 nm.

Figure 4

Figure 4. Metal particle size distribution determined by TEM for a) [(Ni/H-Beta-38)+Att.] and b) [(Ni/Att.)+H-Beta-38].

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SEM images of fresh, reduced [(Ni/H-Beta-38)+Att.] and [(Ni/Att.)+H-Beta-38] show that when Ni was first loaded on H-Beta-38 and thereafter extruded with attapulgite, the fibers were more clearly separated (Figure 5a), while in the latter catalyst, attapulgite fibers are more bound together (Figure 5b).

Figure 5

Figure 5. SEM images of the fresh, reduced a) [(Ni/H-Beta-38)+Att.] and b) [(Ni/Att.)+H-Beta-38] catalysts.

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Hydrogen temperature-programmed reduction was performed to reveal hydrogen consumption dependency on temperature. Two different Ni extrudate catalysts, [(Ni/H-Beta-38)+Att.] and [(Ni/Att.)+H-Beta-38], were reduced similarly prior to the experiment, i.e., 2 °C/min ramping rate up to 350 °C and holding at that temperature for 150 min. The results from the temperature-programmed reduction revealed that the maximum hydrogen uptake for both catalysts occurs at 350 °C (Figure 6). For the former catalyst, a rapid hydrogen consumption started already at 305 °C, while for [(Ni/Att.)+H-Beta-38], reduction of NiO started more rapidly at 348 °C. Furthermore, the total area from hydrogen consumption was 4.2-fold higher for [(Ni/H-Beta-38)+Att.] in comparison to the one where Ni was deposited on attapulgite. This result indicates that it is easier to reduce nickel deposited on Beta-zeolite. As a comparison with the literature, Ni/H-Beta with the Ni particle size of 19.1 nm exhibited the lowest hydrogen consumption at 405 °C, when the TPR heating rate of 10 °C/min was used. (37) Furthermore, for Ni/attapulgite calcined at 500 °C, the reduction of NiO started already at 328 °C indicating reduction of isolated, free NiO particles exhibiting weak interactions with the support. (38)

Figure 6

Figure 6. Hydrogen TPR of a) [(Ni/H-Beta-38)+Att.] and b) [(Ni/Att.)+H-Beta-38].

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The mechanical strength of extrudates consisting of Beta-38 and attapulgite before Ni deposition was determined to be 3.3 ± 0.5 and 2.6 ± 0.1 MPa in the vertical and horizontal positions, respectively (Table 4, entry 1). After Ni introduction, the mechanical strength was slightly increased to 4.5 ± 0.5 and 3.3 ± 0.1 MPa in the vertical and horizontal positions, respectively (Table 4, entry 2). A slightly higher value for [Ni/(H-Beta-38+Att.)] extrudates compared to the metal-free composite (H-Beta-38+Att.) can be attributed to the reinforcing effect of the metallic Ni on the extrudate structure. These values are relatively high compared to the mechanical strength of Ni supported on mesoporous alumino silicate-sepiolite extrudates earlier applied for citral hydrogenation (20) (3.2 ± 0.7 and 0.4 ± 0.1 MPa in the vertical and horizontal positions, respectively). It should be noted that pure attapulgite extrudates exhibited higher mechanical strength of 16.3 ± 1.6 and 7.7 ± 0.8 MPa in vertical and horizontal positions, (29) respectively (Table 4, entry 3), than neat sepiolite extrudates (5.6 ± 0.6 and 3.5 ± 0.4 MPa in vertical and horizontal positions, (29) respectively) (Table 4, entry 4) indicating higher intrinsic endurance of attapulgite-containing extrudates.
Table 4. Average Mechanical Strength of Extrudates in Vertical and Horizontal Positions
no.samplemechanical strength (vertical), MPamechanical strength (horizontal), MPa
1Beta-38 + attapulgite3.3 ± 0.52.6 ± 0.8
2Ni/(Beta-38 + attapulgite)spent4.5 ± 0.53.3 ± 0.9
3attapulgite (29)16.3 ± 1.67.7 ± 0.8
4sepiolite (29)5.6 ± 0.63.5 ± 0.4

3.2. Catalytic Results on Menthol Synthesis

Citronellal transformations were initially performed with the catalyst where Ni was deposited on both the zeolite and the binder, [Ni/(H-Beta-38+Att.)]. During the first 240 min, TOS citronellal disappeared from the bulk liquid either because of the reaction or strong adsorption on the catalyst surface giving citronellal conversion of ca. 95–98%. The liquid phase mass balance closure, which is the sum of the unconverted reactant and products visible in GC analysis of the liquid phase, was only between 20 and 40% within this time period. When using a higher liquid flow rate of 0.3 mL/min, the liquid mass balance increased to 92%. Thus, for citral transformations at a higher liquid flow rate, 0.3 mL/min was used (see below).
The main products initially up to 108 min TOS were p-menthanes, which were formed by dehydration of menthols due to too high Brønsted acidity of the catalyst analogous to dehydration of 1-phenylethanol. (39) When the most acids sites were, however, deactivated, the yield of menthols still remained constant when using the low liquid flow rate of 0.2 mL/min (Figure 7b). When, however, the liquid flow rate was increased to 0.3 mL/min, both the liquid phase mass balance closure and the yields of menthol and acyclic hydrogenation products increased. Maximally, the menthol yield of 53% was obtained at TOS of 240 min over [Ni/(H-Beta-38+Att.)]. Stereoselectivity to menthols was in the range of 70–75% remaining rather constant with increasing time-on-stream. As a comparison, the menthol yield from citronellal over [Ni/(H-Beta-38+Sep.)] was 44% in a trickle bed reactor, (20) which is lower than in the current case with [(Ni/H-Beta-38+Att.)]. On the other hand, stereoselectivity to menthol over both catalysts was ca. 71–76% being thus unaffected by the BAS/LAS ratio. Ni extrudates exhibited also selectivity to menthol in citronellal transformations in a trickle bed reactor higher than several Pt- and Ru-H-Beta-zeolite-bentonite extruded catalysts studied previously also in a fixed bed continuous reactor. (5)

Figure 7

Figure 7. a) Conversion of citronellal (■) and liquid phase mass balance (●) and b) concentration of menthols (●), acyclic hydrogenation products (■), and defunctionalized products (o) and stereoselectivity to menthol (Δ) in citronellal transformation over [Ni/(H-Beta-38+Att.)] as a function of TOS. The liquid flow rate was 0.2 mL/min during 215 min TOS; thereafter, it was 0.3 mL/min.

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Citral transformations over three different Ni-H-Beta-38-attapulgite extrudates, in which Ni is located on Beta-38 [(Ni/H-Beta-38)+Att.], on attapulgite [(Ni/Att.)+H-Beta-38], and on both of them [Ni/(H-Beta-38+Att.)], demonstrated the highest conversion when Ni was supported on the acidic Beta-38 zeolite with attapulgite as a binder (Figure 8a). The composite catalyst [Ni/(H-Beta-38+Att.)] used in citronellal transformation was reduced in situ at 350 °C for 2.5 h with hydrogen, while the two others were freshly reduced catalysts. This apparently should be taken into account while comparing catalytic behavior of these materials.

Figure 8

Figure 8. a) Conversion of citral, b) cis/trans ratio of citral, c) yield of menthols, d) stereoselectivity to menthol, e) yield of pulegols, f) acyclic hydrogenation products, g) 3,7-dimethyloctanol, h) defunctionalized products, (i) menthenes, and j) menthanes as a function of time-on-stream in citral transformation to menthols over different types of Ni extrudates. Notation: (■) [(Ni/H-Beta-38)+Att.], (●) [Ni/(H-Beta-38+Att.)], and (▲) [(Ni/Att.)+H-Beta-38].

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A slightly lower conversion was obtained when nickel was located both on Beta-38 and attapulgite in comparison to [(Ni/H-Beta-38)+Att.], while the lowest conversion was detected when nickel was deposited on attapulgite indicating that the proximity of the acid and metal sites is essential for efficient catalytic behavior. When the pressure was decreased after 180 min time-on-stream to 15 bar, citral conversion decreased linearly with the two most active catalysts (Figure 8a). No sintering occurred for [Ni/(H-Beta-38+Att.)] based on XRD measurements (Table 3) indicating that Ni is more strongly bound on Beta-38 than on attapulgite. On the other hand, activity decline with nickel deposited on attapulgite being significant at 20 bar during 180 min TOS was much less pronounced at 15 bar total pressure.
The reactant is supplied as a mixture of cis and trans isomers with potentially different reactivity. The cis/trans ratio of citral was rather constant with time-on-stream at different pressures. It was, however, the highest with the most acidic catalyst and the lowest one over the catalyst in which Ni is located on mildly acidic attapulgite (Figure 8b). With the most acidic catalyst, the cis/trans ratio increased rapidly with TOS under 20 bar to 1.47; thereafter, it was ca. 1.2–1.3. This result indicated that trans-citral reacted faster under mass transfer limitations, which is in line with the results obtained previously in a trickle bed reactor for Ru-/H-Y extrudates. (17) However, in that case, (17) this ratio decreased with increasing time-on-stream. In a study performed in a batch reactor under kinetic regime over Ni/MCM-41, (14) it was observed that cis-citral reacted initially faster than trans-citral. On the other hand, the cis/trans ratio decreased from the initial value of 0.33 to 0.23 and remained unchanged after a 15 min reaction time indicating that trans-citral reacted faster upon catalyst deactivation, which might be due to the limited adsorption of the cis isomer on the coked surface.
Menthol yields increased with increasing TOS under 20 bar showing the slow reactor dynamics, when the steady state conditions were approaching during 180 min (Figure 8c). Thereafter, when the pressure was decreased to 15 bar, the menthol yields remained at about the same level for the subsequent 120 min TOS, while slightly lower menthol yields were obtained under 10 bar of total pressure at 360 min TOS. According to Nie et al., (15) higher menthol yields were achieved under low total pressures in a batch reactor. In the current case, however, the most acidic sites of the catalyst have already been deactivated increasing the menthol selectivity at high TOS. Such an increase came at the expense of defunctionalized products (see below) formed by dehydration of menthol. (37,39)
The highest yields of menthols were obtained with Ni extrudates which exhibited the highest acidity, i.e., [(Ni/H-Beta-38)+Att.] (45%) and [Ni/(H-Beta-38+Att.)] (44%), respectively, while the lowest ones were demonstrated for [(Ni/Att.)+H-Beta-38] (Figure 8c). These two catalysts exhibited rather high amounts of strong Lewis acid sites (Table 2) which, according to Chuah et al., (40) along with weak Brønsted acidity are beneficial for cyclization of citronellal. Menthol formation remained stable over [(Ni/H-Beta-38)+Att.] after 360 min TOS, while with the two other catalysts, it decreased continuously. Stereoselectivity to the desired menthol isomer was stable as a function of TOS being in the range of 68–78% (Figure 8d). Note that Ni particle size for [(Ni/H-Beta-38)+Att.] is 9.8 nm giving menthol selectivity of 44%, while it was 8 nm for Ni supported on a mesoporous alumino-silicate-sepiolite composite catalyst (21) with the corresponding maximum menthol selectivity of 75%. This result shows that although Ni particle sizes were quite close to each other, the maximum menthol selectivity was much higher in the latter case. This catalyst, the Ni supported on mesoporous alumino-silicate-sepiolite composite catalyst, exhibited no strong Brønsted acid sites, while [(Ni/H-Beta-38)+Att.] contained 68 μmol/gcat them (Table 2, entry 6) indicating the undesired effect of strong Brønsted acid sites on menthol selectivity. The yields of pulegols were higher over [(Ni/Att.)+H-Beta-38] in comparison with the two more active catalysts, [Ni/(H-Beta-38+Att.)] and [(Ni/H-Beta-38)+Att.]. Selectivity to the desired menthol isomer increased with decreasing conversion (Figure 8a), which declined with TOS due to catalyst deactivation. However, at a certain TOS, menthol selectivity decreased for [(Ni/Att.)+H-Beta-38] as well as for [Ni/(Beta-38+Att.)] with decreasing conversion, while for [(Ni/H-Beta-38)+Att.], it remained constant. It is also clearly visible in Figure 8a that at the same conversion level [(Ni/Att.)+H-Beta-38] exhibited the lowest selectivity to the desired menthol also suffering from rapid deactivation, because the metallic nickel was easily oxidized in this catalyst based on XRD measurements (Figure 5). As a comparison to the literature, the highest menthol yield in a batch reactor was reported over 15 wt % Ni/Zr/MCM-41 when using a pressure ramp from 0.2–20 bar at 80 °C in tert-butanol as a solvent. (15) On the other hand, under isobaric conditions, the best performance was observed for 8 wt % Ni/H-MCM-41 giving a 94% menthol yield at 2 bar and 70 °C in toluene. (2) This catalyst contained only weak acid sites according to ammonia TPD. In addition, 75% selectivity of menthols at 98% citral conversion over 5 wt % Ni/mesoporous aluminosilicate-sepiolite extrudates [Ni/(MAS+sepiolite)] was reported in ref (21). When comparing the current results with [Ni/(Beta-38+Att.)] with 44–45% menthol yields, it can be observed that this catalyst contains a 2.23-fold higher amount of Brønsted acid sites (21) than (Ni/(MAS+sepiolite)). Furthermore, comparing the performance of [Ni/(H-Beta-38+Att.)] with that of [Ni/(H-Beta-38+Sep.)] in a trickle bed reactor under the same conditions, it can be stated that the maximum menthols were about the same, i.e., a 44% menthol yield was achieved in the current work, while the latter one in ref (20) gave the maximum menthol yield of 49%. Despite relatively high amounts of impurities in attapulgite, it was equally good as a binder as sepiolite with a much lower amount of impurities. (33) The corresponding Brønsted to Lewis acid ratio in [Ni/(H-Beta-38+Att.)] was 0.43, while for [Ni/(H-Beta-38+Sep.)], it was 0.63. (20) Moreover, the menthol yield decreased with increasing time-on-stream over [Ni/(H-Beta-38+Att.)] only by 19%, while for [Ni/(H-Beta-38+Sep.)], a corresponding decrease was ca. 30% due to its higher BAS/LAS ratio, showing the importance of the BAS/LAS ratio on catalyst stability. These results clearly show that the preparation method of the Ni-H-Beta-38-attapulgite composite catalyst is very important for menthol synthesis, and especially the metal location close to the acidic sites of zeolite is important. When Ni was originally loaded on mildly acidic attapulgite, it was not efficient, and the metallic nickel was not stable under reaction conditions.
The yield of acyclic hydrogenation products, citronellol and 3,7-dimethyloctanol, followed the patterns observed also for menthol formation indicating parallel formation of both menthols and acyclic hydrogenation products for all catalysts with different metal locations (Figures S3, S4). The lowest formation of acyclic hydrogenation products was observed for [(Ni/Att.)+H-Beta-38]. The yield of citronellol remained low, because it was hydrogenated rapidly to 3,7-dimethyloctanol. The amount of 3,7-dimethyloctanol was very high in the current work, especially for [(Ni/H-Beta-38)+Att.], which is opposite from those results obtained over Ni-MCM-41 in refs (14and16) in a batch reactor, where either no hydrogenation products and only traces of them were produced. In Ni-MCM-41, the BAS/LAS ratio was 0.52, while for [(Ni/H-Beta-38)+Att.], it was 0.69.
The highest yield of defunctionalized products (DFP), maximally 42% at 120 min TOS, was obtained over [(Ni/Att.)+H-Beta-38] (Figure 8h), which exhibited the lowest acidity, while the two other catalysts were active in hydrogenation. The yields of DFP decreased with increasing TOS due to catalyst deactivation. The main DFP products were menthanes (Figure 8j), which were formed in the second step after dehydration of menthol forming menthenes, followed by their hydrogenation. It can also be noticed that menthenes are not further hydrogenated on [(Ni/Att.)+H-Beta-38] due to severe catalyst deactivation (Figure 8i). As a comparison to the literature, maximally 22% DFP products were obtained over mildly acidic Ru/H-Y-80 extrudates using bindzil as a binder in a trickle bed reactor. (17) Analogously Ru-MCM-41 gave in a batch reactor an ca. 24% yield of DFP, (18) while an ca. 40% DFP yield was obtained over Ni-H-MCM-41. (16) As a comparison, the yield of DFP products over [Ni/(H-Beta-38+Att.)] was initially ca. 30%, while for [Ni/(H-Beta-38+Sep.)] with a higher BAS/LAS ratio, it was substantially higher 49%. However, with both catalysts, as expected, the DFP yield decreased to ca. 8% with increasing time-on-stream due to catalyst deactivation.

4. Conclusions

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The one-pot synthesis of menthol was demonstrated in the current work in a continuous trickle bed reactor using three different types of Ni containing extrudates prepared on the basis of the H-Beta-38 zeolite and attapulgite as a binder with varying Ni locations. In the first catalyst, Ni is located both on Beta-38 and attapulgite [Ni/(H-Beta-38+Att.)], while in the two other catalysts, Ni was deposited on attapulgite [(Ni/Att.)+H-Beta-38] and on Beta-38 [(Ni/H-Beta-38)+Att.], respectively. These extrudates exhibited different acidity and metal dispersion, which was correlated with its catalytic performance. Maximally a 45% yield of menthol was obtained at 70 °C under 15 bar total pressure over Ni supported on H-Beta-38 followed by extrusion with attapulgite clay. In this catalyst, the proximity of Ni and acid sites facilitated the formation of menthol requiring a bifunctional catalyst. Citral conversion decreased slightly with increasing time-on-stream; however, the best catalyst exhibited also the lowest deactivation rate. The other main products under these conditions were 3,7-dimethyloctanol and menthanes with the yields of 20% and 22%, respectively. These products were formed, because the [(Ni/H-Beta-38)+Att.] catalyst exhibited suitable Ni particle size, ca. 10 nm, and rather high amounts of strong Brønsted acid sites. As a comparison, it can be stated that the [(Ni/H-Beta-38)+Att.] composite catalyst exhibited a similar performance as Ni-H-Beta-38 extruded with sepiolite clay, although the former clay contains also a higher amount of impurities. Furthermore, mechanical strength of [(Ni/H-Beta-38)+Att.] extrudates was rather high. As a comparison, very high initial selectivity to menthols was obtained in a previous work over Ni supported on mesoporous alumino-silicate sepiolite extrudates, which, however, was suffering rapid deactivation.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.iecr.2c02345.

  • Catalyst characterization: pore size distribution, XRD of extrudates. Catalytic data: selectivity to desired menthol as function of conversion, concentration of menthol vs concentration of 3,7-dimethyloctanol and their ratio vs conversion (PDF)

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Author Information

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  • Corresponding Author
  • Authors
    • Irina L. Simakova - Boreskov Institute of Catalysis, pr. Ak. Lavrentieva 5, Novosibirsk, Russia 630090;  Orcidhttps://orcid.org/0000-0002-5138-4847
    • Päivi Mäki-Arvela - Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland;  Orcidhttps://orcid.org/0000-0002-7055-9358
    • Mark Martínez-Klimov - Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
    • Joseph Muller - Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
    • Zuzana Vajglová - Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
    • Markus Peurla - Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
    • Kari Eränen - Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Henriksgatan 2, 20500 Turku/Åbo, Finland
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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The authors are grateful to the Academy of Finland for funding through the following project: Synthesis of spatially controlled catalysts with superior performance. Electron microscopy samples were processed and analyzed in the Electron Microscopy Laboratory, Institute of Biomedicine, University of Turku, which receives financial support from Biocenter Finland. I.S. is grateful for the support from the Ministry of Science and Higher Education of the Russian Federation under the governmental order for the Boreskov Institute of Catalysis (project AAAA-A21-121011390055-8).

References

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    Azkaar, Muhammad; Maki-Arvela, Paivi; Vajglova, Zuzana; Fedorov, Vyacheslav; Kumar, Narendra; Hupa, Leena; Hemming, Jarl; Peurla, Markus; Aho, Atte; Murzin, Dmitry Yu
    Reaction Chemistry & Engineering (2019), 4 (12), 2156-2169CODEN: RCEEBW; ISSN:2058-9883. (Royal Society of Chemistry)
    One-pot menthol synthesis from citronellal in a trickle bed reactor was investigated using Ru/H-beta-300 zeolite extrudates without any binder and Pt- and Ru-extrudates contg. 70 wt% H-beta-25 zeolites and 30 wt% bentonite binder using different methods of metal loading on the extrudates. The catalytic results were correlated with the physico-chem. properties of bifunctional zeolite-based extrudates. The conversion of citronellal to menthol was nearly the same for Pt extrudates being independent of catalyst acidity or the metal particle size. Ru extrudates also exhibited similar conversion levels as a function of time-onstream, except for very mildly acidic Ru/beta-300 extrudates, which gave much lower conversion. Pt extrudates showed better stability with time on stream in comparison with Ru extrudates. The best catalyst giving the highest menthol yield and a low amt. of acyclic hydrogenation products was Ru-beta-bentonite extrudates where Ru was located randomly in the mixt. of 70% H-beta-25 and 30% bentonite binder. Hydrogenation was more prominent for Pt than for Ru catalysts, most probably due to their higher hydrogenation ability. Stereoselectivity to menthol varied in the trickle bed reactor in the range of 67 to 73%. In a batch reactor for Ru- and Pt-catalysts independent of support acidity, it was in the range of 70-71%. The reuse of Ru/H-beta-300 extrudates was successfully demonstrated.
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  6. 6
    Balu, A. M.; Campelo, J. M.; Luque, R.; Romero, A. A. One-step microwave-assisted asymmetric cyclisation/hydrogenation of citronellal to menthols using supported nanoparticles on mesoporous materials. Org. Biomol. Chem. 2010, 8, 2845– 2849,  DOI: 10.1039/c003600e
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    6
    One-step microwave-assisted asymmetric cyclization/hydrogenation of citronellal to menthols using supported nanoparticles on mesoporous materials
    Balu, Alina Mariana; Campelo, Juan Manuel; Luque, Rafael; Romero, Antonio Angel
    Organic & Biomolecular Chemistry (2010), 8 (12), 2845-2849CODEN: OBCRAK; ISSN:1477-0520. (Royal Society of Chemistry)
    The selective conversion of citronellal to menthols, with good diastereoselectivities to (-)-menthol for the case of (+)-citronellal as starting material, can effectively be carried out in a one-step reaction under microwave irradn. catalyzed by supported nanoparticles on mesoporous materials. 2% Pt/Ga-MCM-41 was found to be the optimum catalyst for the reaction, with a quant. conversion of starting material and selectivities above 85% to menthols obtained in short reaction times (typically 15 min). These results constitute the first report of a simple microwave-assisted one-step cyclization/hydrogenation process for the prodn. of menthols.
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  7. 7
    Mertens, P.; Verpoort, F.; Parvulescu, A. N.; De Vos, D. Pt/H-beta zeolites as productive bifunctional catalysts for the one-step citronellal-to-menthol conversion. J. Catal. 2006, 243, 7– 13,  DOI: 10.1016/j.jcat.2006.06.017
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    7
    Pt/H-beta zeolites as productive bifunctional catalysts for the one-step citronellal-to-menthol conversion
    Mertens, Pascal; Verpoort, Francis; Parvulescu, Andrei-Nicolae; De Vos, Dirk
    Journal of Catalysis (2006), 243 (1), 7-13CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Ltd.)
    Pt-loaded H-beta zeolite was identified as a highly active catalyst for the bifunctional transformation of citronellal to menthol, with isopulegol as the intermediate. With a 2 wt% Pt-loaded catalyst, citronellal is fully converted within 12 h, with only 2.5 wt% catalyst with respect to citronellal, and with a citronellal to Pt molar ratio of 2500. 1,4-Dioxane is the best reaction solvent, because it minimizes the unwanted direct hydrogenation of citronellal and promotes its stereoselective cyclization to isopulegol, leading to high menthol yields. The stereoselectivity can be improved moderately by using a Zr-impregnated support and more substantially by performing high-temp. (750 °C) treatment of the calcined and reduced catalyst. This treatment presumably creates extra Lewis acidity on the catalyst and results in 88% stereoselectivity for the desired menthol. Overall, an 85% yield of (-)-menthol was obtained.
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  8. 8
    da Silva Rocha, K. A.; Robles-Dutenhefner, P. A.; Sousa, E. M. B.; Kozhevnikova, E. F.; Gusevskaya, E. Pd-heteropoly acid as a bifunctional heterogeneous catalyst for one-pot conversion of citronellal to menthol. Appl. Catal. A: Gen. 2007, 317, 171– 174,  DOI: 10.1016/j.apcata.2006.10.019
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    8
    Pd-heteropoly acid as a bifunctional heterogeneous catalyst for one-pot conversion of citronellal to menthol
    Da Silva Rocha, Kelly A.; Robles-Dutenhefner, Patricia A.; Sousa, Edesia M. B.; Kozhevnikova, Elena F.; Kozhevnikov, Ivan V.; Gusevskaya, Elena V.
    Applied Catalysis, A: General (2007), 317 (2), 171-174CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    Pd-H3PW12O40/SiO2 catalyzes the one-pot transformation of (+)-citronellal to menthol via acid-catalyzed cyclization followed by Pd-catalyzed hydrogenation, with 92% yield of menthol at 100% citronellal conversion and 85% stereoselectivity for the desired (-)-menthol.
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  9. 9
    Milone, C.; Gangemi, C.; Neri, G.; Pistone, A.; Galvagno, S. Selective one step synthesis of (−)-menthol from (+)-citronellal on Ru supported on modified SiO2. Appl. Catal. A: Gen. 2000, 199, 239– 244,  DOI: 10.1016/S0926-860X(99)00560-8
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    9
    Selective one step synthesis of (-)-menthol from (+)-citronellal on Ru supported on modified SiO2
    Milone, C.; Gangemi, C.; Neri, G.; Pistone, A.; Galvagno, S.
    Applied Catalysis, A: General (2000), 199 (2), 239-244CODEN: ACAGE4; ISSN:0926-860X. (Elsevier Science B.V.)
    The isomerization of (+)-citronellal (I) has been performed under mild conditions on ZnX2 (X=Cl, Br, NO3) supported on high surface area silica. The influence of the Zn loading, counter anion and temp. of pretreatment of the catalyst on the activity and selectivity to (-)-isopulegol (II) was investigated. The catalytic activity increases with the Zn loading. The selectivity to (-)-isopulegol (II) also increases reaching the max. value (86%) on ZnBr2/SiO2 for a Zn content ≥4.0 mmol/g SiO2 ZnBr2/SiO2 is more active than ZnCl2/SiO2, while the selectivity to (-)isopulegol (II) is similar. Zn(NO3)2/SiO2 is far less active and selective. An increase of the temp. of pretreatment increases the selectivity to (-)-isopulegol (II) . A bifunctional catalyst was formulated, namely Ru-ZnBr2/SiO2, on which the one step hydrogenation of (+)-citronellal (I) to (-)-menthol (III) occurs with a yield >85%.
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  10. 10
    Adilina, I. B.; Pertiwi, R.; Sulaswatty, A. Conversion of (±) -citronellal and its derivatives to (−) -menthol using bifunctional. Biopropal Industri 2015, 6, 1– 6,  DOI: 10.36974/jbi.v6i1.828
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  11. 11
    Nie, Y.; Chuah, G. K.; Jaenicke, S. Domino-cyclisation and hydrogenation of citronellal to menthol over bifunctional Ni/Zr-Beta and Zr-beta/Ni-MCM-41 catalysts. Chem. Commun. 2006, 790– 792,  DOI: 10.1039/b513430g
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    11
    Domino-cyclisation and hydrogenation of citronellal to menthol over bifunctional Ni/Zr-Beta and Zr-beta/Ni-MCM-41 catalysts
    Nie, Yuntong; Chuah, Gaik-Khuan; Jaenicke, Stephan
    Chemical Communications (Cambridge, United Kingdom) (2006), (7), 790-792CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    The one-pot conversion of (±)-citronellal to menthol can be selectively catalyzed by either a bifunctional Ni/Zr-zeolite beta catalyst or a dual catalyst system of Zr-beta and Ni/MCM-41, giving a high diastereoselectivity to (±)-menthol of 90-94%.
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  12. 12
    Cortés, C. B.; Galván, V. T.; Pedro, S. S.; García, T. V. One pot synthesis of menthol from (±)-citronellal on nickel sulfated zirconia catalysts. Catal. Today 2011, 172, 21– 26,  DOI: 10.1016/j.cattod.2011.05.005
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    12
    One pot synthesis of menthol from (±)-citronellal on nickel sulfated zirconia catalysts
    Cortes, Cesar Barrales; Galvan, Victoria Tamayo; Pedro, Smid Santiago; Garcia, Tomas Viveros
    Catalysis Today (2011), 172 (1), 21-26CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
    The one-pot synthesis of menthol from (±)-citronellal was carried out using two catalysts: nickel supported on sol-gel sulfated zirconia (Ni/ZrS) and nickel added during the synthesis of sulfated zirconia (NiZrS). The supported catalyst was prepd. by impregnation of nickel on the sulfated zirconia support, whereas NiZrS was prepd. by the co-gellation of nickel and the sulfated zirconia by the sol-gel method. Two sets of catalytic tests were carried out. In both tests the catalysts were previously treated in He stream. First, the liq. phase cyclization of (±)-citronellal was carried out with both ZrS and NiZrS catalysts. The results showed that both ZrS and NiZrS catalysts are highly active and selective towards isopulegols (100% of selectivity) and highly stereoselective towards (±)-isopulegol (∼70% of selectivity). A second reaction test was the synthesis of menthol. The catalysts were evaluated in a batch reactor at 1.4 MPa of H2 and 100 °C. The results showed that the catalysts allow to obtain a high catalytic activity and selectivity towards stereoisomers of menthol (100% selectivity of menthols) and a high selectivity towards (-)-menthol.
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  13. 13
    Iftitah, E. D.; Muchalal, M.; Trisunaryanti, W.; Armunanto, R.; Psaro, R.; Ravasio, N.; Santoro, F.; Sordelli, L. One pot transformation of citronellal to menthol over Ni/γ-Al2O3. J. Appl. Sci. Res. 2011, 7, 680– 689
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    Trasarti, A. F.; Marchi, A. J.; Apesteguía, C. R. Design of catalyst systems for the one-pot synthesis of menthols from citral. J. Catal. 2007, 247 (2), 155– 165,  DOI: 10.1016/j.jcat.2007.01.016
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    Design of catalyst systems for the one-pot synthesis of menthols from citral
    Trasarti, A. F.; Marchi, A. J.; Apesteguia, C. R.
    Journal of Catalysis (2007), 247 (2), 155-165CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Ltd.)
    Stable, active, and highly selective bifunctional Ni/Al-MCM-41 catalysts were developed for the one-pot synthesis of menthols from citral. The liq.-phase hydrogenation of citral to citronellal was studied on silica-supported noble (Pt, Pd, Ir) and nonnoble (Ni, Co, Cu) metals. It was found that citronellal is selectively formed at the beginning of the reaction only on Pd and Ni catalysts. The consecutive ene-cyclization of citronellal to isopulegols was investigated on solid acids contg. exclusively Lewis (ZnO/SiO2) or strong Broensted (CsHPA) acid sites, and also on catalysts contg. both Lewis and Broensted acid sites of either strong (zeolites, SiO2-Al2O3) or moderate (Al-MCM-41) strength. The isopulegol formation rate was higher on samples exhibiting dual Lewis/Broensted acidity, such as SiO2-Al2O3, Al-MCM-41, and zeolite HBEA. Based on these previous results, bifunctional catalysts contg. Pd or Ni supported on SiO2-Al2O3, Al-MCM-41, or zeolite HBEA were prepd. and tested for citral conversion to menthols. The catalyst stability and the effect of hydrogen pressure and metal loading on menthol productivity were also investigated. The best catalyst was Ni(8%)/Al-MCM-41, which yielded more than 90% menthols at 2026.0 kPa and showed no significant deactivation after two consecutive catalytic tests.
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  15. 15
    Nie, Y.; Jaenicke, S.; Chuah, G. K. Zr-zeolite beta: A new heterogeneous catalyst system for the highly selective cascade transformation of citral to (±)-menthol. Chem.─Eur. J. 2009, 15 (8), 1991– 1999,  DOI: 10.1002/chem.200801776
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    15
    Zr-zeolite beta: a new heterogeneous catalyst system for the highly selective cascade transformation of citral to (±)-menthol
    Nie, Yuntong; Jaenicke, Stephan; Chuah, Gaik-Khuan
    Chemistry - A European Journal (2009), 15 (8), 1991-1999CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The transformation of citral to menthols involves hydrogenation steps as well as cyclization of the intermediate, citronellal. The ability of Zr-zeolite beta to catalyze the cyclization with high diastereoselectivity to (±)-isopulegol is the crit. step in this cascade transformation. Bifunctional catalysts contg. nickel or rhodium supported on Zr-zeolite beta gave menthols in yields of 87-89% and an excellent diastereoselectivity of 94% for the desired (±)-menthol. Dual catalyst systems of Zr-zeolite beta and nano-dispersed Ni on an MCM-41 support were equally effective and have the added advantage that the rates of the acid and hydrogenation-catalyzed steps can be independently varied. By applying a pressure ramp of 0.2-2 MPa, the yield of menthols could be increased to 95%, with 94% diastereoselectivity for (±)-menthol. The low initial pressure minimizes the rates of competing hydrogenation reactions to byproducts such as citronellol and 3,7-dimethyloctanol.
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  16. 16
    Mäki-Arvela, P.; Kumar, N.; Kubička, D.; Nasir, A.; Heikkilä, T.; Lehto, V. P.; Sjöholm, R.; Salmi, T.; Murzin, D. Y. One-pot citral transformation to menthol over bifunctional micro-and mesoporous metal modified catalysts: Effect of catalyst support and metal. J. Mol. Catal. A: Chem. 2005, 240 (1–2), 72– 81,  DOI: 10.1016/j.molcata.2005.06.023
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    Vajglová, Z.; Navas, M.; Mäki-Arvela, P.; Eränen, K.; Kumar, N.; Peurla, M.; Murzin, D. Y. Transformations of citral over bifunctional Ru-HY-80 extrudates in a continuous reactor. Chem. Eng. J. 2022, 429, 132190,  DOI: 10.1016/j.cej.2021.132190
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    17
    Transformations of citral over bifunctional Ru-H-Y-80 extrudates in a continuous reactor
    Vajglova, Zuzana; Navas, Marisa; Maki-Arvela, Paivi; Eranen, Kari; Kumar, Narendra; Peurla, Markus; Murzin, Dmitry Yu.
    Chemical Engineering Journal (Amsterdam, Netherlands) (2022), 429 (), 132190CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    One-pot transformations of citral were investigated over Ru-catalysts in a batch and a continuous mode over a powder catalyst and extrudates, resp. Ru/H-Y-80 catalysts were prepd. by different impregnation methods to obtain different particle sizes of Ru. The highest yield of isopulegols was 15% and yield of menthols was 3% with stereoselectivity to the desired (±)-menthol isomer of 42% after 5 h over the Ru/H-Y-80 powder catalyst with the smallest metal particles prepd. by the incipient wetness impregnation method with six impregnation steps using Ru(NO)(NO3)3 as a precursor. This catalyst was synthesized with the Bindzil binder and shaped by extrusion. For comparison, also a catalyst with Ru deposited on the binder was prepd. Addn. of 30 wt% Bindzil binder to Ru/H-Y-80 catalyst caused significant catalyst deactivation. Z/E-citral ratio decreased with increasing Ru particle size. Citral conversion and the yield of acyclic hydrogenation products were higher over the powder catalysts contg. a mixt. of zeolite and binder with a larger distance between the metal and the acid sites, i.e. with Ru deposited on the Bindzil binder. Long-term expts. in the continuous mode revealed comparable catalytic behavior of both Ru-extrudates with the controlled metal location due to the presence of diffusion regime. The max. yield of menthols, 6%, with stereoselectivity to the desired (±)-menthol of 73% was obtained during the transient state, below 2 h of time-onstream. The reuse of Ru/H-Y-80 extrudates was successfully demonstrated.
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    Vajglová, Z.; Mäki-Arvela, P.; Eränen, K.; Kumar, N.; Peurla, M.; Murzin, D. Y. Catalytic transformations of citral in a continuous flow over bifunctional Ru-MCM-41 extrudates. Catal. Sci. Techn. 2021, 11 (8), 2873– 2884,  DOI: 10.1039/D1CY00066G
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    Negoi, A.; Teinz, K.; Kemnitz, E.; Wuttke, S.; Parvulescu, V. L.; Coman, S. M. Bifunctional nanoscopic catalysts for the one-pot synthesis of (±)-menthol from citral. Top. Catal. 2012, 55 (7), 680– 687,  DOI: 10.1007/s11244-012-9850-y
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    Bifunctional Nanoscopic Catalysts for the One-Pot Synthesis of (±)-Menthol from Citral
    Negoi, Alina; Teinz, Katharina; Kemnitz, Erhard; Wuttke, Stefan; Parvulescu, Vasile I.; Coman, Simona M.
    Topics in Catalysis (2012), 55 (7-10), 680-687CODEN: TOCAFI; ISSN:1022-5528. (Springer)
    Active and selective bifunctional Me(Ir, Pd)/beta zeolite and doped nanoscopic hydroxylated fluorides (0.1 % Pd (or Pt)/AlF3) catalysts were developed for the one-pot synthesis of menthols from citral. In the case of fluoride catalysts, the strong electron-withdrawing effect of the dominating fluoride environment depletes the metal surface from electrons and hence, favors the hydrogenation of the C=C bond to citronellal on both Pd and Pt-based catalysts.
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  20. 20
    Simakova, I.; Mäki-Arvela, P.; Martínez-Klimov, M.; Muller, J.; Vajglová, Z.; Peurla, M.; Eränen, K.; Murzin, D. Yu. Continuous synthesis of menthol from citronellal and citral over Ni-Beta-zeolite-sepiolite composite catalyst. Appl. Catal. A: Gen. 2022, 636, 118586,  DOI: 10.1016/j.apcata.2022.118586
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    20
    Continuous synthesis of menthol from citronellal and citral over Ni-beta-zeolite-sepiolite composite catalyst
    Simakova, Irina; Maki-Arvela, Paivi; Martinez-Klimov, Mark; Muller, Joseph; Vajglova, Zuzana; Peurla, Markus; Eranen, Kari; Murzin, Dmitry Yu.
    Applied Catalysis, A: General (2022), 636 (), 118586CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60-70°C under 10-29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71-76% and 72-74% were obtained from citronellal and citral resp. at the contact time 4.2 min, 70°C and 20 bar. Citral conversion noticeably decreased with time-onstream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amt. of defunctionalization products obsd. during citral conversion, esp. at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepd. by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N2 physisorption and FTIR techniques to perceive the interrelation between the physico-chem. and catalytic properties.
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  21. 21
    Simakova, I. L.; Vajglová, Z.; Mäki-Arvela, P.; Eränen, K.; Hupa, L.; Peurla, M.; Mäkilä, E. M.; Wärnå, J.; Murzin, D. Yu. Citral-to-menthol transformations in a continuous reactor over Ni/mesoporous aluminosilicate extrudates containing a sepiolite clay binder. Org. Proc. Res. 2022, 26, 387– 403,  DOI: 10.1021/acs.oprd.1c00435
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    21
    Citral-to-Menthol Transformations in a Continuous Reactor over Ni/Mesoporous Aluminosilicate Extrudates Containing a Sepiolite Clay Binder
    Simakova, Irina L.; Vajglova, Zuzana; Maki-Arvela, Paivi; Eranen, Kari; Hupa, Leena; Peurla, Markus; Makila, Ermei M.; Warna, Johan; Murzin, Dmitry Yu.
    Organic Process Research & Development (2022), 26 (2), 387-403CODEN: OPRDFK; ISSN:1083-6160. (American Chemical Society)
    One-pot continuous synthesis of menthols from citral was performed over 5 wt % Ni supported on a mesoporous aluminosilicate catalyst with sepiolite as a binder at 70°C with a selectivity of 75% to menthols. Catalyst deactivation with time-onstream resulted in a decrease of the conversion and selectivity to menthol at the expense of higher selectivity to isopulegols. Stereoselectivity to isopulegols and menthols only slightly changed with conversion and TOS. A kinetic model capable of describing exptl. data for transformations of citral to menthol in a continuous mode was developed. It was based on a detailed reaction network and also comprised deactivation on both metal and acid sites. Numerical data fitting confirmed a good correspondence between the exptl. data and calcns.
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    Nefzi, H.; Abderrabba, M.; Ayadi, S.; Labidi, J. Formation of palygorskite clay from treated diatomite and its application for the removal of heavy metals from aqueous solution. Water 2018, 10 (9), 1257,  DOI: 10.3390/w10091257
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    22
    Formation of palygorskite clay from treated diatomite and its application for the removal of heavy metals from aqueous solution
    Nefzi, Houwaida; Abderrabba, Manef; Ayadi, Sameh; Labidi, Jalel
    Water (Basel, Switzerland) (2018), 10 (9), 1257/1-1257/15CODEN: WATEGH; ISSN:2073-4441. (MDPI AG)
    Environmental contamination by toxic heavy metals is a serious worldwide phenomenon. Thus, their removal is a crucial issue. In this study, we found an efficient adsorbent to remove Cu2+ and Ni2+ from aq. soln. using two materials. Chem. modification was used to obtain palygorskite clay from diatomite. The adsorbents were characterized using X-ray florescence, Fourier transform IR spectroscopy and X-ray diffraction. The effects of contact time, initial concn., temp. and pH on the adsorption process were investigated. Our results showed that the (%) of max. adsorption capacity of diatomite was 78.44% for Cu2+ at pH 4 and 77.3% for Ni2+ at pH 7, while the (%) of the max. adsorption on palygorskite reached 91% for Cu2+ and 87.05% for Ni2+, in the same condition. The results indicate that the pseudo-second-order model can describe the adsorption process. Furthermore, the adsorption isotherms could be adopted by the Langmuir and the Freundlich models with good correlation coeff. (R2). Thus, our results showed that palygorskite prepd. from Tunisian diatomite is a good adsorbent for the removal of heavy metals from water.
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    Xie, A.; Zhou, X.; Huang, X.; Ji, L.; Zhou, W.; Luo, S.; Yao, C. Cerium-loaded MnOx/attapulgite catalyst for the low-temperature NH3-selective catalytic reduction. J. Ind. Eng. Chem. 2017, 49, 230– 241,  DOI: 10.1016/j.jiec.2017.01.034
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    23
    Cerium-loaded MnOx/attapulgite catalyst for the low-temperature NH3-selective catalytic reduction
    Xie, Aijuan; Zhou, Xingmeng; Huang, Xiaoyan; Ji, Liang; Zhou, Wenting; Luo, Shiping; Yao, Chao
    Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2017), 49 (), 230-241CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
    A series of MnO2/attapulgite (ATP) and n(Ce):n(Mn)/ATP (molar ratios) catalysts were prepd. and investigated for the selective catalytic redn. of NO by NH3 (NH3-SCR) at low temp. The results showed that the 7 wt % MnO2/ATP exhibited the best NOx conversion (85% at 300°C) among all MnO2/ATP catalysts of different mass ratios. The introduction of cerium enhanced the NOx conversion at low temp., and so Ce-MnOx/ATP can reach the highest NOx conversion (95% at 300°C). Meanwhile, the as-prepd. catalysts were characterized by XRD, TEM, BET, H2-TPR, NH3-TPD, and XPS. It can be deduced from TEM, XRD, and BET, MnOx nanorods in this work mainly existed in the β-MnO2, and cerium highly dispersed on the surface of ATP to form porous structure and thus improved the deNOx performance. Moreover, the study of SO2 tolerance demonstrated that cerium can effectively inhibit SO2 poison. XPS results illustrated that Ce could enhance Mn4+ content on the surface of the catalyst and thus lead to high SCR activity. Therefore Mn(1):Ce(0.25)/ATP was proved to be an excellent catalyst for NH3-SCR.
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  24. 24
    Guo, S.; Shi, L. Synthesis of succinic anhydride from maleic anhydride on Ni/diatomite catalysts. Catal. Today 2013, 212, 137– 141,  DOI: 10.1016/j.cattod.2012.10.004
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    Synthesis of succinic anhydride from maleic anhydride on Ni/diatomite catalysts
    Guo, Shaofei; Shi, Li
    Catalysis Today (2013), 212 (), 137-141CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
    The characteristics and catalytic properties of Ni(5%)/diatomite, Ni(5%)/γ-Al2O3, Ni(5% wt)/Bentonite clay and Ni(5%)/attapulgite clay were investigated and compared in terms of catalytic activities for liq.-phase hydrogenation of maleic anhydride (MA). The results showed that the diatomite support exhibited the highest activity and selectivity. Using Ni(7%)/diatomite catalyst, the 100% conversion of MA and 96.20% selectivity to SA were obtained for MA hydrogenation at 190°. The x-ray diffraction (x-ray diffraction) studies showed that there is only NiO on the support and no elemental nickel (Ni0) and Ni2O3 was detected in unreduced samples. X-ray diffraction and H2 temp.-programmed redn. (TPR) studies also showed that NiO species were all converted to metallic nickel (Ni0) after redn. at 350°.
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  25. 25
    Anderson, J. A.; Rodrigo, M. T.; Daza, L.; Mendioroz, S. Influence of the support in the selectivity of nickel/clay catalysts for vegetable oil hydrogenation. Langmuir 1993, 9 (10), 2485– 2490,  DOI: 10.1021/la00034a001
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    Influence of the support in the selectivity of nickel/clay catalysts for vegetable oil hydrogenation
    Anderson, J. A.; Rodrigo, M. T.; Daza, L.; Mendioroz, S.
    Langmuir (1993), 9 (10), 2485-90CODEN: LANGD5; ISSN:0743-7463.
    Two naturally occurring clays of Spanish origin, bentonite and palygorskite, have been used as support material for nickel hydrogenation catalysts in which the active phase has been deposited by means of the pptn. method. The structural and textural characteristics of the supports have been studied by XRD, N2 adsorption/desorption, and mercury porosimetry and the acid sites detd. by thermogravimetry and IR studies of adsorbed pyridine. The Ni phases present were characterized by XRD, TEM, XPS, FTIR of adsorbed CO, and the degree of redn. detd. thermogravimetrically. XRD and TEM indicate Ni particle size to be equiv. for both supports although the detection by FTIR of a high proportion of bridging CO for the bentonite support suggests the presence of addn. small particles for this support which may be located between lamellae. These smaller particles are consistent with the more difficult redn. of Ni in this support. Although activity for the hydrogenation of sunflower oil was similar for both catalysts, significant differences regarding the selectivity have been obsd. which may be attributed to the differences in morphol. of the support materials. Mass transport limitations resulting from reaction of linoleic acid at Ni sites between lamellae of bentonite leads to consecutive hydrogenation through to stearic acid, whereas the palygorskite supported catalyst remained highly selective to oleic acid even at high conversion levels.
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    Zecevic, J.; Vanbutsele, G.; de Jong, K. P.; Martens, J. A. Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons. Nature 2015, 528 (7581), 245– 248,  DOI: 10.1038/nature16173
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    Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons
    Zecevic, Jovana; Vanbutsele, Gina; de Jong, Krijn P.; Martens, Johan A.
    Nature (London, United Kingdom) (2015), 528 (7581), 245-248CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
    The ability to control nanoscale features precisely is increasingly being exploited to develop and improve monofunctional catalysts. Striking effects might also be expected in the case of bifunctional catalysts, which are important in the hydrocracking of fossil and renewable hydrocarbon sources to provide high-quality diesel fuel. Such bifunctional hydrocracking catalysts contain metal sites and acid sites, and for >50 years the so-called intimacy criterion has dictated the max. distance between the two types of site, beyond which catalytic activity decreases. A lack of synthesis and material-characterization methods with nanometer precision has long prevented in-depth exploration of the intimacy criterion, which has often been interpreted simply as the closer the better for positioning metal and acid sites. Here the authors show for a bifunctional catalyst-comprising an intimate mixt. of zeolite Y and alumina binder, and with platinum metal controllably deposited on either the zeolite or the binder-that closest proximity between metal and zeolite acid sites can be detrimental. Specifically, the selectivity when cracking large hydrocarbon feedstock mols. for high-quality diesel prodn. is optimized with the catalyst that contains platinum on the binder, i.e., with a nanoscale rather than closest intimacy of the metal and acid sites. Thus, cracking of the large and complex hydrocarbon mols. that are typically derived from alternative sources, such as gas-to-liq. technol., vegetable oil or algal oil, should benefit esp. from bifunctional catalysts that avoid locating platinum on the zeolite (the traditionally assumed optimal location). More generally, the authors anticipate that the ability demonstrated here to spatially organize different active sites at the nanoscale will benefit the further development and optimization of the emerging generation of multifunctional catalysts.
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    Harmel, J.; Roberts, T.; Zhang, Z.; Sunley, G.; de Jongh, P.; de Jong, K. P. Bifunctional molybdenum oxide/acid catalysts for hydroisomerization of n-heptane. J. Catal. 2020, 390, 161– 169,  DOI: 10.1016/j.jcat.2020.08.004
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    Bifunctional molybdenum oxide/acid catalysts for hydroisomerization of n-heptane
    Harmel, Justine; Roberts, Tegan; Zhang, Zhaorong; Sunley, Glenn; de Jongh, Petra; de Jong, Krijn P.
    Journal of Catalysis (2020), 390 (), 161-169CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Inc.)
    Numerus research studies focus on replacing scarce noble metals by nonnoble transition metals in solid catalysts. The (de)hydrogenation function in bifunctional catalysts for hydroisomerization and hydrocracking of alkanes is usually performed by a precious metal such as Pt, or a metal sulfide such as MoS2. The authors studied the possibility of replacing Pt with a nonsulfided MoOx catalyst in combination with a mesoporous solid acid for the hydroisomerization of n-heptane. MoOx particles size as well as the prepn. techniques were varied to identify the Mo active phase for (de)hydrogenation. An optimized nonprecious metal MoOx catalyst can perform similarly to its Pt counterpart in the n-heptane conversion when used in combination with a mesoporous solid acid.
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    Vajglová, Z.; Kumar, N.; Peurla, M.; Hupa, L.; Semikin, K.; Sladkovskiy, D. A.; Murzin, D. Yu. Effect of the preparation of Pt-modified zeolite beta-bentonite extrudates on their catalytic behavior in n-hexane hydroisomerization. Ind. Eng. Chem. Res. 2019, 58 (25), 10875– 10885,  DOI: 10.1021/acs.iecr.9b01931
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    28
    Effect of the Preparation of Pt-Modified Zeolite Beta-Bentonite Extrudates on Their Catalytic Behavior in n-Hexane Hydroisomerization
    Vajglova, Zuzana; Kumar, Narendra; Peurla, Markus; Hupa, Leena; Semikin, Kirill; Sladkovskiy, Dmitry A.; Murzin, Dmitry Yu.
    Industrial & Engineering Chemistry Research (2019), 58 (25), 10875-10885CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
    Four different types of shaped catalysts with controlled deposition of Pt and the same compn. were prepd. by extrusion of beta zeolite agglomerated with bentonite as an aluminosilicate clay binder. The catalysts were characterized using mech. strength tests; SEM for morphol.; TEM for porosity and periodicity; N physisorption for surface area, pore vol., and pore size distribution; and FTIR spectroscopy using pyridine as a probe mol. to elucidate the presence, strength, and amt. of Broensted and Lewis acid sites. Elemental anal. was carried out using energy-dispersive x-ray microanal. Activity and selectivity of catalysts in the isomerization of n-hexane were evaluated using a fixed bed reactor at 200-350°. At low temp., the performance of metal/acid bifunctional shaped catalysis was strongly affected by the metal-to-acid site ratio. This ratio and the total acidity were strongly influenced by the prepn. method of the shaped catalysts, while the textural properties were comparable. The highest conversion of n-hexane and selectivity to C6 isomers (comprising all branched isomers, such as Me pentane and dimethylbutane) was obtained with extrudates prepd. via in situ synthesis with Pt located on the zeolite. The extrudates prepd. in this way have the highest metal-to-acid site ratio and their closest proximity, albeit the lowest mech. strength.
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  29. 29
    Vajglová, Z.; Simakova, I. L.; Eränen, K.; Mäki-Arvela, P.; Kumar, N.; Peurla, M.; Tolvanen, S.; Efimov, A.; Hupa, L.; Peltonen, J.; Murzin, D. Yu. The physicochemical and catalytic properties of clay extrudates in cyclization of citronellal. Appl. Catal. A: Gen. 2022, 629, 118426,  DOI: 10.1016/j.apcata.2021.118426
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    The physicochemical and catalytic properties of clay extrudates in cyclization of citronellal
    Vajglova, Zuzana; Simakova, Irina L.; Eranen, Kari; Maki-Arvela, Paivi; Kumar, Narendra; Peurla, Markus; Tolvanen, Stiina; Efimov, Alexander; Hupa, Leena; Peltonen, Jouko; Murzin, Dmitry Yu.
    Applied Catalysis, A: General (2022), 629 (), 118426CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    Four clay materials, namely, bentonite, bleaching earth, attapulgite and sepiolite, were shaped into the cylindrical body by extrusion. Clays were characterized in depth by TEM, SEM-EDX, N2 physisorption, pyridine FTIR, pH measurements, contact angle measurements, 27Al MAS NMR, and the crush test. Catalytic properties were investigated in the citronellal cyclization as a model reaction. The reaction was performed in the trickle-bed reactor at 70°C, 10 bar of Ar with 0.086 M initial citronellal concn. in cyclohexane. The best results were obtained over attapulgite with isopulegols yield of 24% and stereoselectivity to the desired isopulegol isomer of 61%. Attapulgite had the highest meso-to-micropore vol. ratio, the highest basicity, a low Bronsted-to-Lewis acid sites ratio, and the lowest amt. of Bronsted acid sites compared to other extrudates. In addn., same clay exhibited the highest mech. strength of extrudates.
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    Emeis, C. A. Determination of integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on solid acid catalysts. J. Catal. 1993, 141, 347– 354,  DOI: 10.1006/jcat.1993.1145
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    Determination of integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on solid acid catalysts
    Emeis, C. A.
    Journal of Catalysis (1993), 141 (2), 347-54CODEN: JCTLA5; ISSN:0021-9517.
    Integrated molar extinction coeffs. were detd. for IR absorption bands of pyridine adsorbed on acid sites in Si/Al-based catalysts. The IR spectra of five zeolites and two amorphous silica-aluminas were recorded during quant. dosing of pyridine gas at 150°. The integrated mol. extinction coeffs. were calcd. assuming that they did not depend on the catalyst or the strength of the acid site. The resulting values were 1.67 cm/μmol for the 1545-cm-1 band characteristic of pyridine on a Broensted acid site and 2.22 cm/μmol for the 1455-cm-1 band of pyridine on a Lewis acid site. The 95% confidence limits were estd. at ±15%. Subsequent anal. of the data provided no evidence for a dependence of the integrated coeffs. on the catalyst or the strength of the site. The measurements gave indications for differences between the rates of reaction of Broensted and Lewis acid sites with pyridine.
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    Powder Diffraction File database PDF-2; International Centre for Diffraction Data: USA, 2009.
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    Vajglova, Z.; Kumar, N.; Mäki-Arvela, P.; Eränen, K.; Peurla, M.; Hupa, L.; Nurmi, M.; Toivakka, M.; Murzin, D. Y. Synthesis and physicochemical characterization of shaped catalysts of β and Y zeolites for cyclization of citronellal. Ind. Eng. Chem. Res. 2019, 58 (39), 18084– 18096,  DOI: 10.1021/acs.iecr.9b02829
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    Synthesis and Physicochemical Characterization of Shaped Catalysts of β and Y Zeolites for Cyclization of Citronellal
    Vajglova, Zuzana; Kumar, Narendra; Maki-Arvela, Paivi; Eranen, Kari; Peurla, Markus; Hupa, Leena; Nurmi, Maristiina; Toivakka, Martti; Murzin, Dmitry Yu
    Industrial & Engineering Chemistry Research (2019), 58 (39), 18084-18096CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
    Continuous cyclization of citronellal over zeolite-based extrudates was performed in a trickle-bed reactor at 35-70 °C and 10 bar of argon. Catalytic results were correlated with the physicochem. properties of the shaped catalyst prepd. by extrusion of β or Y zeolites with binders. Rheol. tests were used to elucidate the flow properties of a catalytic slurry and relate them with the extrusion performance. This study revealed that application of methylcellulose and bentonite binder modified the textural and acidic properties of the final extrudates. The main product was (-)-isopulegol at all temps. with selectivity remaining quite const. with time-onstream. The results illustrated that a binder such as bentonite cannot be considered inert. The mass-transfer limitations obsd. in extrudates did not significantly influence selectivity to the desired pulegols. This study also showed that a direct transfer of the batch reactor data to industrial continuous operation in citronellal cyclization is not straightforward.
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    Boudriche, L.; Chamayou, A.; Calvet, R.; Hamdi, B.; Balard, H. Influence of different dry milling processes on the properties of an attapulgite clay, contribution of inverse gas chromatography. Powder technology 2014, 254, 352– 363,  DOI: 10.1016/j.powtec.2014.01.041
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    Influence of different dry milling processes on the properties of attapulgitic clay, contribution of inverse gas chromatography
    Boudriche, L.; Chamayou, A.; Calvet, R.; Hamdi, B.; Balard, H.
    Powder Technology (2014), 254 (), 352-363CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)
    The effect of dry milling processes on the surface properties of an attapulgitic clay, also called palygorskite, was investigated by carrying out expts. with different types of grinding devices. Ground products were then characterized by size measurement, SEM, X-ray diffraction, adsorption-desorption of N2 and inverse gas chromatog. at infinite diln. (IGC-ID) as well as finite concn. conditions (IGC-FC). These analyses were performed to evaluate the changes in particle size distribution, morphol., crystallinity and surface properties of attapulgite powder, resp. Among the tested dry grinding devices, grinding in an air jet mill (Alpine 50 AS) and a vibratory ball mill (Pulverisette 0) led to the most significant particle size redn. SEM photomicrographs showed that a breakage of the fibrous structure took place during dry grinding. Moreover, long grinding in Pulverisette 0 resulted in the complete destruction of fiber morphol. followed by agglomeration. XRD anal. showed that whatever the grinding process, the microstructure of the attapulgite was not affected. IGC confirmed that only grinding in Pulverisette 0 affected the surface properties notably. In this case, the most significant decreases were obsd. in the dispersive component of the surface energy (164 to 116 mJ/m2) and in the sp. surface area obtained with the octane probe (114.5 m2/g to 62.6 m2/g) by IGC-ID and IGC-FC, resp. At the same time, a modification of the distribution functions of the adsorption energies (DFAE), giving information about surface heterogeneity, was noticed.
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    Nugraha, R. E.; Prasetyoko, D.; Bahruji, H.; Suprapto, S.; Asikin-Mijan, N.; Oetami, T. P.; Dai-Veit, N. Vo.; Taufiq-Yap, Y. H. Lewis acid Ni/Al-MCM-41 catalysts for H2-free deoxygenation of Reutealis trisperma oil to biofuels. RSC Adv. 2021, 11 (36), 21885– 21896,  DOI: 10.1039/D1RA03145G
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    Lewis acid Ni/Al-MCM-41 catalysts for H2-free deoxygenation of Reutealis trisperma oil to biofuels
    Nugraha, Reva Edra; Prasetyoko, Didik; Bahruji, Hasliza; Suprapto, Suprapto; Asikin-Mijan, Nurul; Oetami, Titie Prapti; Jalil, Aishah Abdul; Vo, Dai-Viet N.; Taufiq-Yap, Yun Hin
    RSC Advances (2021), 11 (36), 21885-21896CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    The activity of mesoporous Al-MCM-41 for deoxygenation of Reutealis trisperma oil (RTO) was enhanced via modification with NiO nanoparticles. Deoxygenation at atm. pressure and under H2 free conditions required acid catalysts to ensure the removal of the oxygenated fragments in triglycerides to form liq. hydrocarbons. NiO at different wt. loadings was impregnated onto Al-MCM-41 and the changes of Lewis/Bronsted acidity and mesoporosity of the catalysts were investigated. The activity of Al-MCM-41 was enhanced when impregnated with NiO due to the increase of Lewis acidity originating from NiO nanoparticles and the mesoporosity of Al-MCM-41. Increasing the NiO loading enhanced the Lewis acidity but not Bronsted acidity, leading to a higher conversion toward liq. hydrocarbon yield. Impregnation with 10% of NiO on Al-MCM-41 increased the conversion of RTO to hydrocarbons via the deoxygenation pathway and reduced the products from cracking reaction, consequently enhancing the green diesel (C11-C18) hydrocarbon products.
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    Yang, L.; Huang, J.; Cen, J.; Chen, D. L.; Zeng, H.; Rui, Z.; Luque, R.; Duan, P. Lewis acid (Ni 2+, Co 2+/3+ or Zn 2+) modified electron-deficient Ir 4+ in IrO 2/CuO for promoting methane oxidation to ethanol and methanol. J. Mater. Chem. A 2021, 9 (11), 7094– 7101,  DOI: 10.1039/D0TA10842A
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    Lewis acid (Ni2+, Co2+/3+ or Zn2+) modified electron-deficient Ir4+ in IrO2/CuO for promoting methane oxidation to ethanol and methanol
    Yang, Le; Huang, Jinxu; Cen, Jie; Chen, De-Li; Zeng, Hui; Rui, Zebao; Luque, Rafael; Duan, Peigao
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2021), 9 (11), 7094-7101CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    This work delineates the first attempt to tune the product distribution between methanol and ethanol in the direct oxidn. of methane reaction by incorporating Lewis acids Ni2+, Co2+/3+ or Zn2+ into IrO2/CuO. The electrophilicity of Ir4+ and the (LAS-BAS)/LAS ratio (LAS: Lewis acid sites, BAS: Bronsted acid sites) are demonstrated to be two reactivity descriptors motivating CH4 activation and ethanol formation, resp. Electron-deficient Ir4+ motivates enriched *CH3 concn. and subsequent C-C coupling for C2H4 formation, while the Lewis acid promotes ethanol formation from C2H4 involving lattice O and H2O. The ethanol selectivity presents a quasi-linear relationship with (LAS-BAS)/LAS.
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    Wei, Z.; Xia, T.; Ma, J.; Feng, W.; Dai, J.; Wang, Q.; Yan, P. Investigation of the lattice expansion for Ni nanoparticles. Mater. Charact. 2007, 58 (10), 1019– 1024,  DOI: 10.1016/j.matchar.2006.08.004
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    Investigation of the lattice expansion for Ni nanoparticles
    Wei, Zhiqiang; Xia, Tiandong; Ma, Jun; Feng, Wangjun; Dai, Jianfeng; Wang, Qing; Yan, Pengxun
    Materials Characterization (2007), 58 (10), 1019-1024CODEN: MACHEX; ISSN:1044-5803. (Elsevier B.V.)
    Nickel nanoparticles with various grain sizes were successfully prepd. by anodic arc discharge plasma method. The samples prepd. by this method were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected-area electron diffraction (SAED) to det. the crystal structure, lattice parameter, morphol. and particle size. The expt. results indicate that the crystal structure of the samples is fcc. structure as same as the bulk materials. The lattice parameters for Ni nanoparticles are always larger than the equil. values of the perfect single crystal lattice resp., the lattice parameter increase significantly with the decrease of the grain size, the lattice expansion was found, and the expansion quantity of the lattice parameter is in direct proportion to the reciprocal of grain size. The values of the unit cell vol. increase remarkably with the decrease of the grain size. The lattice expansion is the result of the interfacial energy and surface tension mutual attraction of Ni nanoparticles, this phenomenon can be explained according to the thermodn. theory.
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    Quindimil, A.; De-La-Torre, U.; Pereda-Ayo, B.; Gonzalez-Marcos, J. A.; Gonzalez-Velasco, J. R. Ni catalysts with La as promoter supported over Y-and Beta-zeolites for CO2 methanation. Appl. Catal. B: Env. 2018, 238, 393– 403,  DOI: 10.1016/j.apcatb.2018.07.034
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    Ni catalysts with La as promoter supported over Y- and BETA- zeolites for CO2 methanation
    Quindimil, Adrian; De-La-Torre, Unai; Pereda-Ayo, Benat; Gonzalez-Marcos, Jose A.; Gonzalez-Velasco, Juan R.
    Applied Catalysis, B: Environmental (2018), 238 (), 393-403CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    The hydrogenation of CO2 into methane is considered a plausible process to storage renewable energy in form of methane and reducing CO2 anthropogenic emissions. Microporous solids such as zeolites have been scarcely studied yet for this application. This study aims to evaluate and compare the catalytic performance of zeolite (Y and BETA) supported Ni catalysts for CO2 methanation. The physicochem. properties of the prepd. catalysts were characterized by XRD, BET, CO2-TPD, H2-TPR and XPS, and CO2 methanation was carried out in a tubular reactor at conditions of H2/CO2 = 4, GHSV = 10,000 h-1 and temps. from 200 to 500 C. Neutralization of both zeolites by Na+ ion exchange enhanced the CO2 conversion as weaker CO2 adsorption sites and reducibility are promoted. BETA resulted in a better support than Y zeolite due to the presence of more easily reducible Ni2+, which acts as precursor of active Ni° accessible under reaction conditions. Indeed, the surface basicity and Ni dispersion of Ni/BETA catalysts were considerably promoted by impregnation of different loads of La2O3, which increase the amt. of CO2 adsorption sites and even active hydrogenation sites resulting in a significant increase of activity and selectivity towards CH4. The optimal Ni-10%La2O3/Na-BETA formulation resulted in T50 of 320°C, CO2 conversion of 65% at 350 °C, with almost total selectivity to CH4 and maintaining stability for more than 24 h.
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    Wang, Y.; Liang, D.; Wang, C.; Chen, M.; Tang, Z.; Hu, J.; Yang, Z.; Zhang, H.; Wang, J.; Liu, S. Influence of calcination temperature of Ni/attapulgite on hydrogen production by steam reforming ethanol. Renew. Energy 2020, 160, 597– 611,  DOI: 10.1016/j.renene.2020.06.126
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    Influence of calcination temperature of Ni/Attapulgite on hydrogen production by steam reforming ethanol
    Wang, Yishuang; Liang, Defang; Wang, Chunsheng; Chen, Mingqiang; Tang, Zhiyuan; Hu, Jiaxin; Yang, Zhonglian; Zhang, Han; Wang, Jun; Liu, Shaomin
    Renewable Energy (2020), 160 (), 597-611CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
    Sustainable hydrogen prodn. can be realized by steam reforming ethanol (SRE) derived from renewable biomass, but develop high-efficiency and sixpenny catalyst is a major challenge. Attapulgite-supported nickel catalyst (Ni/ATP) exhibits promising potential for SRE for hydrogen prodn. The influence of calcination temp. (CT) on the microscopic morphol. and physicochem. properties of Ni/ATP was investigated by various technologies. The results revealed that increasing CT could improve metal-support interaction (MSI) and surface Ni active species content. However, extortionate CT (>700°C) significantly led to catalyst structure collapse and crystal phase transfer accompanied with the formation of new species, which enhanced the MSI and reduced the surface Nio species content. The outcomes of SRE expts. demonstrated that Ni/ATP-C600 presented maximal activity and H2 yield due to its higher surface contents of the Nio active component and Ni/ATP-C900 exhibited unique stability owing to its stronger MSI. Hence, the coordination between active species distribution and MSI in Ni/ATP can be adjusted by CT. Addnl. coke deposits on spent Ni/ATP-C300 were identified with quite arom. species, which strongly attract to the surface of catalyst and encapsulate active site, while that on used Ni/ATP-C900 had higher degrees of graphitization, but did not affect the stability.
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    Bertero, N. M.; Trasarti, A. F.; Apesteguía, C. R.; Marchi, A. J. Liquid-phase dehydration of 1-phenylethanol on solid acids: Influence of catalyst acidity and pore structure. Appl. Catal. A: Gen. 2013, 458, 28– 38,  DOI: 10.1016/j.apcata.2013.03.018
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    38
    Liquid-phase dehydration of 1-phenylethanol on solid acids: Influence of catalyst acidity and pore structure
    Bertero, Nicolas M.; Trasarti, Andres F.; Apesteguia, Carlos R.; Marchi, Alberto J.
    Applied Catalysis, A: General (2013), 458 (), 28-38CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    The liq.-phase dehydration of 1-phenylethanol (PHE) over different solid acids was studied at 363 K using cyclohexane as solvent. It was found that the catalyst activity and selectivity strongly depended on: (1) the nature, strength and d. of acid sites and (2) the textural properties of the catalyst. Catalysts contg. mainly surface Bronsted acid sites of medium-high strength, such as Amberlyst 15, HPA/SiO2, and HMOR zeolite, showed low initial styrene (STY) selectivity because the PHE dehydrated to alpha-methylbenzyl ether (AME) at higher or similar rates than to STY. Both primary products, STY and AME, were consecutively transformed to other heavy products (HP). Catalysts contg. predominantly Lewis acid sites, such as ZnO/SiO2, Al-MCM-41 and SiO2-Al2O3, selectively transformed PHE to AME. The ether can be sequentially converted to STY and HP, depending on the solid acidity. Solid acids having strong surface Lewis sites, e.g. SiO2-Al2O3, showed high dehydration rate and HP prodn. Samples contg. exclusively weak Lewis acid sites, e.g. γ-Al2O3, were not active in the PHE dehydration at 363 K. Only zeolites HZSM-5, HBEA and HY, with similar surface d. of Bronsted and Lewis acid sites, converted selectively PHE into STY, giving initial STY selectivities between 83 and 96%. However, HY zeolite was rapidly deactivated due to the blockage of its microporous structure by bulky compds. formed inside the large cages of 13 Å. Instead, on HBEA, STY was converted to HP that can diffuse through the solid microporous structure. Then, the selectivity to STY was drastically reduced with time. A const. and high STY selectivity at total PHE conversion was only obtained with HZSM-5. The pore size of this zeolite is enough to allow the diffusion and conversion of PHE into STY, but it is not adequate to form the surface intermediates leading to AME and HP. Thus, it was proved that: (1) the surface Bronsted to Lewis ratio strongly influences the initial selectivity in the liq.-phase PHE dehydration; (2) a similar Bronsted to Lewis ratio on the solid acid surface is necessary to obtain high initial selectivity to STY; and (3) the right porous structure is crucial to avoid HP prodn. and keep const. the STY selectivity at high PHE conversion. From the exptl. results obtained in this work, a mechanistic approach was proposed in order to explain the influence of both acid site nature and pore size on the selective PHE dehydration in liq. phase.
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    Chuah, G. K.; Liu, S. H.; Jaenicke, S.; Harrison, L. J. Cyclisation of citronellal to isopulegol catalysed by hydrous zirconia and other solid acids. J. Catal. 2001, 200 (2), 352– 359,  DOI: 10.1006/jcat.2001.3208
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    Cyclization of Citronellal to Isopulegol Catalyzed by Hydrous Zirconia and Other Solid Acids
    Chuah, G. K.; Liu, S. H.; Jaenicke, S.; Harrison, L. J.
    Journal of Catalysis (2001), 200 (2), 352-359CODEN: JCTLA5; ISSN:0021-9517. (Academic Press)
    A review with 29 refs. The cyclization of citronellal to isopulegol is an important step in the synthesis of menthol. Several zirconia-based catalysts were evaluated for this reaction. Zirconium hydroxides and phosphated zirconia had very good activity and selectivity. Ammonia TPD and pyridine IR studies indicate the presence of strong Lewis together with weak Bronsted acid sites. Other strong acids like sulfated zirconia, Amberlyst, and Nafion were very active but the selectivity toward isopulegol was poor. They catalyzed side reactions such as dehydration, cracking, and etherification of isopulegol. Silica, with only weak Lewis acidity, showed very low activity. The presence of both Lewis and Bronsted sites is therefore essential for the reaction. A reaction mechanism is proposed where the citronellal mol. binds to a zirconium Lewis acid site via the aldehyde oxygen and the π-electrons of the double bond so that the right configuration is attained for cyclization. Subsequent protonation of the aldehyde via a neighboring Bronsted acid site initiates the cyclization to isopulegol. (c) 2001 Academic Press.
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  1. Irina L. Simakova, Zuzana Vajglová, Mark Martínez-Klimov, Kari Eränen, Markus Peurla, Päivi Mäki-Arvela, Dmitry Yu. Murzin. One-Pot Synthesis of Menthol from Citral over Ni/H-β-38 Extrudates Containing Bentonite Clay Binder in Batch and Continuous Reactors. Organic Process Research & Development 2023, 27 (2) , 295-310. https://doi.org/10.1021/acs.oprd.2c00337
  2. Jie Dong, Wei Ding, Jinfei Wei, Ning Tian, Xueli Nan, Junping Zhang. Preparation of Food Grade Superhydrophobic Coatings Based on Attapulgite Nanorods. ACS Sustainable Chemistry & Engineering 2023, 11 (4) , 1405-1413. https://doi.org/10.1021/acssuschemeng.2c05915
  3. Päivi Mäki-Arvela, Irina Simakova, Zuzana Vajglová, Dmitry Yu. Murzin. One-Pot Synthesis of Menthol from Citral and Citronellal Over Heterogeneous Catalysts. Catalysis Surveys from Asia 2023, 27 (1) , 2-19. https://doi.org/10.1007/s10563-022-09376-6
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  • Abstract

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    Figure 1

    Figure 1. Reaction scheme for citral transformation to menthol. Legend: A – citral, B – citronellal, C – isopulegol isomers, D – menthol isomers, E – acyclic hydrogenation products, F – defunctionalization products, dimeric ethers, and heavy components.

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    Figure 2

    Figure 2. XRD patterns of a) the calcined (c.), freshly reduced (r), and spent (s) [Ni/(H-Beta-38+Att.)] extrudates compared to the initial H-Beta-38 zeolite and b) the spent [Ni/(H-Beta-38+Att.)], [(Ni/H-Beta-38)+Att.], and [(Ni/Att.)+H-Beta-38] extrudates compared to the initial H-Beta-38 zeolite. Notation: spent [Ni/(H-Beta-38+Att.)] was used first in citronellal transformation; thereafter, it was reduced in situ and used in citral transformation, while spent [(Ni/H-Beta-38)+Att.] and [(Ni/Att.)+H-Beta-38] extrudates were only used in citral transformation.

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    Figure 3

    Figure 3. TEM images of a) attapulgite, b) H-Beta-38, c) [Ni/(H-Beta-38+Att.)], d) [(Ni/H-Beta-38)+Att.], and e) [(Ni/Att.)+H-Beta-38].

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    Figure 4

    Figure 4. Metal particle size distribution determined by TEM for a) [(Ni/H-Beta-38)+Att.] and b) [(Ni/Att.)+H-Beta-38].

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    Figure 5

    Figure 5. SEM images of the fresh, reduced a) [(Ni/H-Beta-38)+Att.] and b) [(Ni/Att.)+H-Beta-38] catalysts.

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    Figure 6

    Figure 6. Hydrogen TPR of a) [(Ni/H-Beta-38)+Att.] and b) [(Ni/Att.)+H-Beta-38].

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    Figure 7

    Figure 7. a) Conversion of citronellal (■) and liquid phase mass balance (●) and b) concentration of menthols (●), acyclic hydrogenation products (■), and defunctionalized products (o) and stereoselectivity to menthol (Δ) in citronellal transformation over [Ni/(H-Beta-38+Att.)] as a function of TOS. The liquid flow rate was 0.2 mL/min during 215 min TOS; thereafter, it was 0.3 mL/min.

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    Figure 8

    Figure 8. a) Conversion of citral, b) cis/trans ratio of citral, c) yield of menthols, d) stereoselectivity to menthol, e) yield of pulegols, f) acyclic hydrogenation products, g) 3,7-dimethyloctanol, h) defunctionalized products, (i) menthenes, and j) menthanes as a function of time-on-stream in citral transformation to menthols over different types of Ni extrudates. Notation: (■) [(Ni/H-Beta-38)+Att.], (●) [Ni/(H-Beta-38+Att.)], and (▲) [(Ni/Att.)+H-Beta-38].

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  • References

    This article references 40 other publications.

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      For the first time the selective synthesis of menthols from citral in a one-step process is reported. Bifunctional metal/acid catalysts active and selective for menthol synthesis were developed by studying the individual steps involved in the reaction pathway leading to menthols from citral. The metallic component was selected by testing silica-supported metals for citral hydrogenation to citronellal. Acid site requirements to efficiently isomerize citronellal to isopulegols were investigated on different solid acids. Potential bifunctional metal/acid catalysts were then prepd. and tested for citral conversion to menthols. The best catalyst was Ni/Al-MCM-41, which yielded about 90% menthols and gave 70-75% of racemic (±)-menthol in the menthol mixt.
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      Azkaar, Muhammad; Maki-Arvela, Paivi; Vajglova, Zuzana; Fedorov, Vyacheslav; Kumar, Narendra; Hupa, Leena; Hemming, Jarl; Peurla, Markus; Aho, Atte; Murzin, Dmitry Yu
      Reaction Chemistry & Engineering (2019), 4 (12), 2156-2169CODEN: RCEEBW; ISSN:2058-9883. (Royal Society of Chemistry)
      One-pot menthol synthesis from citronellal in a trickle bed reactor was investigated using Ru/H-beta-300 zeolite extrudates without any binder and Pt- and Ru-extrudates contg. 70 wt% H-beta-25 zeolites and 30 wt% bentonite binder using different methods of metal loading on the extrudates. The catalytic results were correlated with the physico-chem. properties of bifunctional zeolite-based extrudates. The conversion of citronellal to menthol was nearly the same for Pt extrudates being independent of catalyst acidity or the metal particle size. Ru extrudates also exhibited similar conversion levels as a function of time-onstream, except for very mildly acidic Ru/beta-300 extrudates, which gave much lower conversion. Pt extrudates showed better stability with time on stream in comparison with Ru extrudates. The best catalyst giving the highest menthol yield and a low amt. of acyclic hydrogenation products was Ru-beta-bentonite extrudates where Ru was located randomly in the mixt. of 70% H-beta-25 and 30% bentonite binder. Hydrogenation was more prominent for Pt than for Ru catalysts, most probably due to their higher hydrogenation ability. Stereoselectivity to menthol varied in the trickle bed reactor in the range of 67 to 73%. In a batch reactor for Ru- and Pt-catalysts independent of support acidity, it was in the range of 70-71%. The reuse of Ru/H-beta-300 extrudates was successfully demonstrated.
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      The selective conversion of citronellal to menthols, with good diastereoselectivities to (-)-menthol for the case of (+)-citronellal as starting material, can effectively be carried out in a one-step reaction under microwave irradn. catalyzed by supported nanoparticles on mesoporous materials. 2% Pt/Ga-MCM-41 was found to be the optimum catalyst for the reaction, with a quant. conversion of starting material and selectivities above 85% to menthols obtained in short reaction times (typically 15 min). These results constitute the first report of a simple microwave-assisted one-step cyclization/hydrogenation process for the prodn. of menthols.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXmvVWktbw%253D&md5=bba1f1128bba182ba3d67e193a9d4f34
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      Pt/H-beta zeolites as productive bifunctional catalysts for the one-step citronellal-to-menthol conversion
      Mertens, Pascal; Verpoort, Francis; Parvulescu, Andrei-Nicolae; De Vos, Dirk
      Journal of Catalysis (2006), 243 (1), 7-13CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Ltd.)
      Pt-loaded H-beta zeolite was identified as a highly active catalyst for the bifunctional transformation of citronellal to menthol, with isopulegol as the intermediate. With a 2 wt% Pt-loaded catalyst, citronellal is fully converted within 12 h, with only 2.5 wt% catalyst with respect to citronellal, and with a citronellal to Pt molar ratio of 2500. 1,4-Dioxane is the best reaction solvent, because it minimizes the unwanted direct hydrogenation of citronellal and promotes its stereoselective cyclization to isopulegol, leading to high menthol yields. The stereoselectivity can be improved moderately by using a Zr-impregnated support and more substantially by performing high-temp. (750 °C) treatment of the calcined and reduced catalyst. This treatment presumably creates extra Lewis acidity on the catalyst and results in 88% stereoselectivity for the desired menthol. Overall, an 85% yield of (-)-menthol was obtained.
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      da Silva Rocha, K. A.; Robles-Dutenhefner, P. A.; Sousa, E. M. B.; Kozhevnikova, E. F.; Gusevskaya, E. Pd-heteropoly acid as a bifunctional heterogeneous catalyst for one-pot conversion of citronellal to menthol. Appl. Catal. A: Gen. 2007, 317, 171– 174,  DOI: 10.1016/j.apcata.2006.10.019
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      Pd-heteropoly acid as a bifunctional heterogeneous catalyst for one-pot conversion of citronellal to menthol
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      Pd-H3PW12O40/SiO2 catalyzes the one-pot transformation of (+)-citronellal to menthol via acid-catalyzed cyclization followed by Pd-catalyzed hydrogenation, with 92% yield of menthol at 100% citronellal conversion and 85% stereoselectivity for the desired (-)-menthol.
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      The isomerization of (+)-citronellal (I) has been performed under mild conditions on ZnX2 (X=Cl, Br, NO3) supported on high surface area silica. The influence of the Zn loading, counter anion and temp. of pretreatment of the catalyst on the activity and selectivity to (-)-isopulegol (II) was investigated. The catalytic activity increases with the Zn loading. The selectivity to (-)-isopulegol (II) also increases reaching the max. value (86%) on ZnBr2/SiO2 for a Zn content ≥4.0 mmol/g SiO2 ZnBr2/SiO2 is more active than ZnCl2/SiO2, while the selectivity to (-)isopulegol (II) is similar. Zn(NO3)2/SiO2 is far less active and selective. An increase of the temp. of pretreatment increases the selectivity to (-)-isopulegol (II) . A bifunctional catalyst was formulated, namely Ru-ZnBr2/SiO2, on which the one step hydrogenation of (+)-citronellal (I) to (-)-menthol (III) occurs with a yield >85%.
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      Nie, Y.; Chuah, G. K.; Jaenicke, S. Domino-cyclisation and hydrogenation of citronellal to menthol over bifunctional Ni/Zr-Beta and Zr-beta/Ni-MCM-41 catalysts. Chem. Commun. 2006, 790– 792,  DOI: 10.1039/b513430g
      11
      Domino-cyclisation and hydrogenation of citronellal to menthol over bifunctional Ni/Zr-Beta and Zr-beta/Ni-MCM-41 catalysts
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      The one-pot conversion of (±)-citronellal to menthol can be selectively catalyzed by either a bifunctional Ni/Zr-zeolite beta catalyst or a dual catalyst system of Zr-beta and Ni/MCM-41, giving a high diastereoselectivity to (±)-menthol of 90-94%.
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      Cortés, C. B.; Galván, V. T.; Pedro, S. S.; García, T. V. One pot synthesis of menthol from (±)-citronellal on nickel sulfated zirconia catalysts. Catal. Today 2011, 172, 21– 26,  DOI: 10.1016/j.cattod.2011.05.005
      12
      One pot synthesis of menthol from (±)-citronellal on nickel sulfated zirconia catalysts
      Cortes, Cesar Barrales; Galvan, Victoria Tamayo; Pedro, Smid Santiago; Garcia, Tomas Viveros
      Catalysis Today (2011), 172 (1), 21-26CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
      The one-pot synthesis of menthol from (±)-citronellal was carried out using two catalysts: nickel supported on sol-gel sulfated zirconia (Ni/ZrS) and nickel added during the synthesis of sulfated zirconia (NiZrS). The supported catalyst was prepd. by impregnation of nickel on the sulfated zirconia support, whereas NiZrS was prepd. by the co-gellation of nickel and the sulfated zirconia by the sol-gel method. Two sets of catalytic tests were carried out. In both tests the catalysts were previously treated in He stream. First, the liq. phase cyclization of (±)-citronellal was carried out with both ZrS and NiZrS catalysts. The results showed that both ZrS and NiZrS catalysts are highly active and selective towards isopulegols (100% of selectivity) and highly stereoselective towards (±)-isopulegol (∼70% of selectivity). A second reaction test was the synthesis of menthol. The catalysts were evaluated in a batch reactor at 1.4 MPa of H2 and 100 °C. The results showed that the catalysts allow to obtain a high catalytic activity and selectivity towards stereoisomers of menthol (100% selectivity of menthols) and a high selectivity towards (-)-menthol.
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      Iftitah, E. D.; Muchalal, M.; Trisunaryanti, W.; Armunanto, R.; Psaro, R.; Ravasio, N.; Santoro, F.; Sordelli, L. One pot transformation of citronellal to menthol over Ni/γ-Al2O3. J. Appl. Sci. Res. 2011, 7, 680– 689
      There is no corresponding record for this reference.
    14. 14
      Trasarti, A. F.; Marchi, A. J.; Apesteguía, C. R. Design of catalyst systems for the one-pot synthesis of menthols from citral. J. Catal. 2007, 247 (2), 155– 165,  DOI: 10.1016/j.jcat.2007.01.016
      14
      Design of catalyst systems for the one-pot synthesis of menthols from citral
      Trasarti, A. F.; Marchi, A. J.; Apesteguia, C. R.
      Journal of Catalysis (2007), 247 (2), 155-165CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Ltd.)
      Stable, active, and highly selective bifunctional Ni/Al-MCM-41 catalysts were developed for the one-pot synthesis of menthols from citral. The liq.-phase hydrogenation of citral to citronellal was studied on silica-supported noble (Pt, Pd, Ir) and nonnoble (Ni, Co, Cu) metals. It was found that citronellal is selectively formed at the beginning of the reaction only on Pd and Ni catalysts. The consecutive ene-cyclization of citronellal to isopulegols was investigated on solid acids contg. exclusively Lewis (ZnO/SiO2) or strong Broensted (CsHPA) acid sites, and also on catalysts contg. both Lewis and Broensted acid sites of either strong (zeolites, SiO2-Al2O3) or moderate (Al-MCM-41) strength. The isopulegol formation rate was higher on samples exhibiting dual Lewis/Broensted acidity, such as SiO2-Al2O3, Al-MCM-41, and zeolite HBEA. Based on these previous results, bifunctional catalysts contg. Pd or Ni supported on SiO2-Al2O3, Al-MCM-41, or zeolite HBEA were prepd. and tested for citral conversion to menthols. The catalyst stability and the effect of hydrogen pressure and metal loading on menthol productivity were also investigated. The best catalyst was Ni(8%)/Al-MCM-41, which yielded more than 90% menthols at 2026.0 kPa and showed no significant deactivation after two consecutive catalytic tests.
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    15. 15
      Nie, Y.; Jaenicke, S.; Chuah, G. K. Zr-zeolite beta: A new heterogeneous catalyst system for the highly selective cascade transformation of citral to (±)-menthol. Chem.─Eur. J. 2009, 15 (8), 1991– 1999,  DOI: 10.1002/chem.200801776
      15
      Zr-zeolite beta: a new heterogeneous catalyst system for the highly selective cascade transformation of citral to (±)-menthol
      Nie, Yuntong; Jaenicke, Stephan; Chuah, Gaik-Khuan
      Chemistry - A European Journal (2009), 15 (8), 1991-1999CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The transformation of citral to menthols involves hydrogenation steps as well as cyclization of the intermediate, citronellal. The ability of Zr-zeolite beta to catalyze the cyclization with high diastereoselectivity to (±)-isopulegol is the crit. step in this cascade transformation. Bifunctional catalysts contg. nickel or rhodium supported on Zr-zeolite beta gave menthols in yields of 87-89% and an excellent diastereoselectivity of 94% for the desired (±)-menthol. Dual catalyst systems of Zr-zeolite beta and nano-dispersed Ni on an MCM-41 support were equally effective and have the added advantage that the rates of the acid and hydrogenation-catalyzed steps can be independently varied. By applying a pressure ramp of 0.2-2 MPa, the yield of menthols could be increased to 95%, with 94% diastereoselectivity for (±)-menthol. The low initial pressure minimizes the rates of competing hydrogenation reactions to byproducts such as citronellol and 3,7-dimethyloctanol.
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    16. 16
      Mäki-Arvela, P.; Kumar, N.; Kubička, D.; Nasir, A.; Heikkilä, T.; Lehto, V. P.; Sjöholm, R.; Salmi, T.; Murzin, D. Y. One-pot citral transformation to menthol over bifunctional micro-and mesoporous metal modified catalysts: Effect of catalyst support and metal. J. Mol. Catal. A: Chem. 2005, 240 (1–2), 72– 81,  DOI: 10.1016/j.molcata.2005.06.023
      There is no corresponding record for this reference.
    17. 17
      Vajglová, Z.; Navas, M.; Mäki-Arvela, P.; Eränen, K.; Kumar, N.; Peurla, M.; Murzin, D. Y. Transformations of citral over bifunctional Ru-HY-80 extrudates in a continuous reactor. Chem. Eng. J. 2022, 429, 132190,  DOI: 10.1016/j.cej.2021.132190
      17
      Transformations of citral over bifunctional Ru-H-Y-80 extrudates in a continuous reactor
      Vajglova, Zuzana; Navas, Marisa; Maki-Arvela, Paivi; Eranen, Kari; Kumar, Narendra; Peurla, Markus; Murzin, Dmitry Yu.
      Chemical Engineering Journal (Amsterdam, Netherlands) (2022), 429 (), 132190CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      One-pot transformations of citral were investigated over Ru-catalysts in a batch and a continuous mode over a powder catalyst and extrudates, resp. Ru/H-Y-80 catalysts were prepd. by different impregnation methods to obtain different particle sizes of Ru. The highest yield of isopulegols was 15% and yield of menthols was 3% with stereoselectivity to the desired (±)-menthol isomer of 42% after 5 h over the Ru/H-Y-80 powder catalyst with the smallest metal particles prepd. by the incipient wetness impregnation method with six impregnation steps using Ru(NO)(NO3)3 as a precursor. This catalyst was synthesized with the Bindzil binder and shaped by extrusion. For comparison, also a catalyst with Ru deposited on the binder was prepd. Addn. of 30 wt% Bindzil binder to Ru/H-Y-80 catalyst caused significant catalyst deactivation. Z/E-citral ratio decreased with increasing Ru particle size. Citral conversion and the yield of acyclic hydrogenation products were higher over the powder catalysts contg. a mixt. of zeolite and binder with a larger distance between the metal and the acid sites, i.e. with Ru deposited on the Bindzil binder. Long-term expts. in the continuous mode revealed comparable catalytic behavior of both Ru-extrudates with the controlled metal location due to the presence of diffusion regime. The max. yield of menthols, 6%, with stereoselectivity to the desired (±)-menthol of 73% was obtained during the transient state, below 2 h of time-onstream. The reuse of Ru/H-Y-80 extrudates was successfully demonstrated.
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    18. 18
      Vajglová, Z.; Mäki-Arvela, P.; Eränen, K.; Kumar, N.; Peurla, M.; Murzin, D. Y. Catalytic transformations of citral in a continuous flow over bifunctional Ru-MCM-41 extrudates. Catal. Sci. Techn. 2021, 11 (8), 2873– 2884,  DOI: 10.1039/D1CY00066G
      There is no corresponding record for this reference.
    19. 19
      Negoi, A.; Teinz, K.; Kemnitz, E.; Wuttke, S.; Parvulescu, V. L.; Coman, S. M. Bifunctional nanoscopic catalysts for the one-pot synthesis of (±)-menthol from citral. Top. Catal. 2012, 55 (7), 680– 687,  DOI: 10.1007/s11244-012-9850-y
      19
      Bifunctional Nanoscopic Catalysts for the One-Pot Synthesis of (±)-Menthol from Citral
      Negoi, Alina; Teinz, Katharina; Kemnitz, Erhard; Wuttke, Stefan; Parvulescu, Vasile I.; Coman, Simona M.
      Topics in Catalysis (2012), 55 (7-10), 680-687CODEN: TOCAFI; ISSN:1022-5528. (Springer)
      Active and selective bifunctional Me(Ir, Pd)/beta zeolite and doped nanoscopic hydroxylated fluorides (0.1 % Pd (or Pt)/AlF3) catalysts were developed for the one-pot synthesis of menthols from citral. In the case of fluoride catalysts, the strong electron-withdrawing effect of the dominating fluoride environment depletes the metal surface from electrons and hence, favors the hydrogenation of the C=C bond to citronellal on both Pd and Pt-based catalysts.
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    20. 20
      Simakova, I.; Mäki-Arvela, P.; Martínez-Klimov, M.; Muller, J.; Vajglová, Z.; Peurla, M.; Eränen, K.; Murzin, D. Yu. Continuous synthesis of menthol from citronellal and citral over Ni-Beta-zeolite-sepiolite composite catalyst. Appl. Catal. A: Gen. 2022, 636, 118586,  DOI: 10.1016/j.apcata.2022.118586
      20
      Continuous synthesis of menthol from citronellal and citral over Ni-beta-zeolite-sepiolite composite catalyst
      Simakova, Irina; Maki-Arvela, Paivi; Martinez-Klimov, Mark; Muller, Joseph; Vajglova, Zuzana; Peurla, Markus; Eranen, Kari; Murzin, Dmitry Yu.
      Applied Catalysis, A: General (2022), 636 (), 118586CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60-70°C under 10-29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71-76% and 72-74% were obtained from citronellal and citral resp. at the contact time 4.2 min, 70°C and 20 bar. Citral conversion noticeably decreased with time-onstream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amt. of defunctionalization products obsd. during citral conversion, esp. at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepd. by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N2 physisorption and FTIR techniques to perceive the interrelation between the physico-chem. and catalytic properties.
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    21. 21
      Simakova, I. L.; Vajglová, Z.; Mäki-Arvela, P.; Eränen, K.; Hupa, L.; Peurla, M.; Mäkilä, E. M.; Wärnå, J.; Murzin, D. Yu. Citral-to-menthol transformations in a continuous reactor over Ni/mesoporous aluminosilicate extrudates containing a sepiolite clay binder. Org. Proc. Res. 2022, 26, 387– 403,  DOI: 10.1021/acs.oprd.1c00435
      21
      Citral-to-Menthol Transformations in a Continuous Reactor over Ni/Mesoporous Aluminosilicate Extrudates Containing a Sepiolite Clay Binder
      Simakova, Irina L.; Vajglova, Zuzana; Maki-Arvela, Paivi; Eranen, Kari; Hupa, Leena; Peurla, Markus; Makila, Ermei M.; Warna, Johan; Murzin, Dmitry Yu.
      Organic Process Research & Development (2022), 26 (2), 387-403CODEN: OPRDFK; ISSN:1083-6160. (American Chemical Society)
      One-pot continuous synthesis of menthols from citral was performed over 5 wt % Ni supported on a mesoporous aluminosilicate catalyst with sepiolite as a binder at 70°C with a selectivity of 75% to menthols. Catalyst deactivation with time-onstream resulted in a decrease of the conversion and selectivity to menthol at the expense of higher selectivity to isopulegols. Stereoselectivity to isopulegols and menthols only slightly changed with conversion and TOS. A kinetic model capable of describing exptl. data for transformations of citral to menthol in a continuous mode was developed. It was based on a detailed reaction network and also comprised deactivation on both metal and acid sites. Numerical data fitting confirmed a good correspondence between the exptl. data and calcns.
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    22. 22
      Nefzi, H.; Abderrabba, M.; Ayadi, S.; Labidi, J. Formation of palygorskite clay from treated diatomite and its application for the removal of heavy metals from aqueous solution. Water 2018, 10 (9), 1257,  DOI: 10.3390/w10091257
      22
      Formation of palygorskite clay from treated diatomite and its application for the removal of heavy metals from aqueous solution
      Nefzi, Houwaida; Abderrabba, Manef; Ayadi, Sameh; Labidi, Jalel
      Water (Basel, Switzerland) (2018), 10 (9), 1257/1-1257/15CODEN: WATEGH; ISSN:2073-4441. (MDPI AG)
      Environmental contamination by toxic heavy metals is a serious worldwide phenomenon. Thus, their removal is a crucial issue. In this study, we found an efficient adsorbent to remove Cu2+ and Ni2+ from aq. soln. using two materials. Chem. modification was used to obtain palygorskite clay from diatomite. The adsorbents were characterized using X-ray florescence, Fourier transform IR spectroscopy and X-ray diffraction. The effects of contact time, initial concn., temp. and pH on the adsorption process were investigated. Our results showed that the (%) of max. adsorption capacity of diatomite was 78.44% for Cu2+ at pH 4 and 77.3% for Ni2+ at pH 7, while the (%) of the max. adsorption on palygorskite reached 91% for Cu2+ and 87.05% for Ni2+, in the same condition. The results indicate that the pseudo-second-order model can describe the adsorption process. Furthermore, the adsorption isotherms could be adopted by the Langmuir and the Freundlich models with good correlation coeff. (R2). Thus, our results showed that palygorskite prepd. from Tunisian diatomite is a good adsorbent for the removal of heavy metals from water.
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    23. 23
      Xie, A.; Zhou, X.; Huang, X.; Ji, L.; Zhou, W.; Luo, S.; Yao, C. Cerium-loaded MnOx/attapulgite catalyst for the low-temperature NH3-selective catalytic reduction. J. Ind. Eng. Chem. 2017, 49, 230– 241,  DOI: 10.1016/j.jiec.2017.01.034
      23
      Cerium-loaded MnOx/attapulgite catalyst for the low-temperature NH3-selective catalytic reduction
      Xie, Aijuan; Zhou, Xingmeng; Huang, Xiaoyan; Ji, Liang; Zhou, Wenting; Luo, Shiping; Yao, Chao
      Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2017), 49 (), 230-241CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
      A series of MnO2/attapulgite (ATP) and n(Ce):n(Mn)/ATP (molar ratios) catalysts were prepd. and investigated for the selective catalytic redn. of NO by NH3 (NH3-SCR) at low temp. The results showed that the 7 wt % MnO2/ATP exhibited the best NOx conversion (85% at 300°C) among all MnO2/ATP catalysts of different mass ratios. The introduction of cerium enhanced the NOx conversion at low temp., and so Ce-MnOx/ATP can reach the highest NOx conversion (95% at 300°C). Meanwhile, the as-prepd. catalysts were characterized by XRD, TEM, BET, H2-TPR, NH3-TPD, and XPS. It can be deduced from TEM, XRD, and BET, MnOx nanorods in this work mainly existed in the β-MnO2, and cerium highly dispersed on the surface of ATP to form porous structure and thus improved the deNOx performance. Moreover, the study of SO2 tolerance demonstrated that cerium can effectively inhibit SO2 poison. XPS results illustrated that Ce could enhance Mn4+ content on the surface of the catalyst and thus lead to high SCR activity. Therefore Mn(1):Ce(0.25)/ATP was proved to be an excellent catalyst for NH3-SCR.
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    24. 24
      Guo, S.; Shi, L. Synthesis of succinic anhydride from maleic anhydride on Ni/diatomite catalysts. Catal. Today 2013, 212, 137– 141,  DOI: 10.1016/j.cattod.2012.10.004
      24
      Synthesis of succinic anhydride from maleic anhydride on Ni/diatomite catalysts
      Guo, Shaofei; Shi, Li
      Catalysis Today (2013), 212 (), 137-141CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
      The characteristics and catalytic properties of Ni(5%)/diatomite, Ni(5%)/γ-Al2O3, Ni(5% wt)/Bentonite clay and Ni(5%)/attapulgite clay were investigated and compared in terms of catalytic activities for liq.-phase hydrogenation of maleic anhydride (MA). The results showed that the diatomite support exhibited the highest activity and selectivity. Using Ni(7%)/diatomite catalyst, the 100% conversion of MA and 96.20% selectivity to SA were obtained for MA hydrogenation at 190°. The x-ray diffraction (x-ray diffraction) studies showed that there is only NiO on the support and no elemental nickel (Ni0) and Ni2O3 was detected in unreduced samples. X-ray diffraction and H2 temp.-programmed redn. (TPR) studies also showed that NiO species were all converted to metallic nickel (Ni0) after redn. at 350°.
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    25. 25
      Anderson, J. A.; Rodrigo, M. T.; Daza, L.; Mendioroz, S. Influence of the support in the selectivity of nickel/clay catalysts for vegetable oil hydrogenation. Langmuir 1993, 9 (10), 2485– 2490,  DOI: 10.1021/la00034a001
      25
      Influence of the support in the selectivity of nickel/clay catalysts for vegetable oil hydrogenation
      Anderson, J. A.; Rodrigo, M. T.; Daza, L.; Mendioroz, S.
      Langmuir (1993), 9 (10), 2485-90CODEN: LANGD5; ISSN:0743-7463.
      Two naturally occurring clays of Spanish origin, bentonite and palygorskite, have been used as support material for nickel hydrogenation catalysts in which the active phase has been deposited by means of the pptn. method. The structural and textural characteristics of the supports have been studied by XRD, N2 adsorption/desorption, and mercury porosimetry and the acid sites detd. by thermogravimetry and IR studies of adsorbed pyridine. The Ni phases present were characterized by XRD, TEM, XPS, FTIR of adsorbed CO, and the degree of redn. detd. thermogravimetrically. XRD and TEM indicate Ni particle size to be equiv. for both supports although the detection by FTIR of a high proportion of bridging CO for the bentonite support suggests the presence of addn. small particles for this support which may be located between lamellae. These smaller particles are consistent with the more difficult redn. of Ni in this support. Although activity for the hydrogenation of sunflower oil was similar for both catalysts, significant differences regarding the selectivity have been obsd. which may be attributed to the differences in morphol. of the support materials. Mass transport limitations resulting from reaction of linoleic acid at Ni sites between lamellae of bentonite leads to consecutive hydrogenation through to stearic acid, whereas the palygorskite supported catalyst remained highly selective to oleic acid even at high conversion levels.
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    26. 26
      Zecevic, J.; Vanbutsele, G.; de Jong, K. P.; Martens, J. A. Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons. Nature 2015, 528 (7581), 245– 248,  DOI: 10.1038/nature16173
      26
      Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons
      Zecevic, Jovana; Vanbutsele, Gina; de Jong, Krijn P.; Martens, Johan A.
      Nature (London, United Kingdom) (2015), 528 (7581), 245-248CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
      The ability to control nanoscale features precisely is increasingly being exploited to develop and improve monofunctional catalysts. Striking effects might also be expected in the case of bifunctional catalysts, which are important in the hydrocracking of fossil and renewable hydrocarbon sources to provide high-quality diesel fuel. Such bifunctional hydrocracking catalysts contain metal sites and acid sites, and for >50 years the so-called intimacy criterion has dictated the max. distance between the two types of site, beyond which catalytic activity decreases. A lack of synthesis and material-characterization methods with nanometer precision has long prevented in-depth exploration of the intimacy criterion, which has often been interpreted simply as the closer the better for positioning metal and acid sites. Here the authors show for a bifunctional catalyst-comprising an intimate mixt. of zeolite Y and alumina binder, and with platinum metal controllably deposited on either the zeolite or the binder-that closest proximity between metal and zeolite acid sites can be detrimental. Specifically, the selectivity when cracking large hydrocarbon feedstock mols. for high-quality diesel prodn. is optimized with the catalyst that contains platinum on the binder, i.e., with a nanoscale rather than closest intimacy of the metal and acid sites. Thus, cracking of the large and complex hydrocarbon mols. that are typically derived from alternative sources, such as gas-to-liq. technol., vegetable oil or algal oil, should benefit esp. from bifunctional catalysts that avoid locating platinum on the zeolite (the traditionally assumed optimal location). More generally, the authors anticipate that the ability demonstrated here to spatially organize different active sites at the nanoscale will benefit the further development and optimization of the emerging generation of multifunctional catalysts.
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    27. 27
      Harmel, J.; Roberts, T.; Zhang, Z.; Sunley, G.; de Jongh, P.; de Jong, K. P. Bifunctional molybdenum oxide/acid catalysts for hydroisomerization of n-heptane. J. Catal. 2020, 390, 161– 169,  DOI: 10.1016/j.jcat.2020.08.004
      27
      Bifunctional molybdenum oxide/acid catalysts for hydroisomerization of n-heptane
      Harmel, Justine; Roberts, Tegan; Zhang, Zhaorong; Sunley, Glenn; de Jongh, Petra; de Jong, Krijn P.
      Journal of Catalysis (2020), 390 (), 161-169CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Inc.)
      Numerus research studies focus on replacing scarce noble metals by nonnoble transition metals in solid catalysts. The (de)hydrogenation function in bifunctional catalysts for hydroisomerization and hydrocracking of alkanes is usually performed by a precious metal such as Pt, or a metal sulfide such as MoS2. The authors studied the possibility of replacing Pt with a nonsulfided MoOx catalyst in combination with a mesoporous solid acid for the hydroisomerization of n-heptane. MoOx particles size as well as the prepn. techniques were varied to identify the Mo active phase for (de)hydrogenation. An optimized nonprecious metal MoOx catalyst can perform similarly to its Pt counterpart in the n-heptane conversion when used in combination with a mesoporous solid acid.
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    28. 28
      Vajglová, Z.; Kumar, N.; Peurla, M.; Hupa, L.; Semikin, K.; Sladkovskiy, D. A.; Murzin, D. Yu. Effect of the preparation of Pt-modified zeolite beta-bentonite extrudates on their catalytic behavior in n-hexane hydroisomerization. Ind. Eng. Chem. Res. 2019, 58 (25), 10875– 10885,  DOI: 10.1021/acs.iecr.9b01931
      28
      Effect of the Preparation of Pt-Modified Zeolite Beta-Bentonite Extrudates on Their Catalytic Behavior in n-Hexane Hydroisomerization
      Vajglova, Zuzana; Kumar, Narendra; Peurla, Markus; Hupa, Leena; Semikin, Kirill; Sladkovskiy, Dmitry A.; Murzin, Dmitry Yu.
      Industrial & Engineering Chemistry Research (2019), 58 (25), 10875-10885CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
      Four different types of shaped catalysts with controlled deposition of Pt and the same compn. were prepd. by extrusion of beta zeolite agglomerated with bentonite as an aluminosilicate clay binder. The catalysts were characterized using mech. strength tests; SEM for morphol.; TEM for porosity and periodicity; N physisorption for surface area, pore vol., and pore size distribution; and FTIR spectroscopy using pyridine as a probe mol. to elucidate the presence, strength, and amt. of Broensted and Lewis acid sites. Elemental anal. was carried out using energy-dispersive x-ray microanal. Activity and selectivity of catalysts in the isomerization of n-hexane were evaluated using a fixed bed reactor at 200-350°. At low temp., the performance of metal/acid bifunctional shaped catalysis was strongly affected by the metal-to-acid site ratio. This ratio and the total acidity were strongly influenced by the prepn. method of the shaped catalysts, while the textural properties were comparable. The highest conversion of n-hexane and selectivity to C6 isomers (comprising all branched isomers, such as Me pentane and dimethylbutane) was obtained with extrudates prepd. via in situ synthesis with Pt located on the zeolite. The extrudates prepd. in this way have the highest metal-to-acid site ratio and their closest proximity, albeit the lowest mech. strength.
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    29. 29
      Vajglová, Z.; Simakova, I. L.; Eränen, K.; Mäki-Arvela, P.; Kumar, N.; Peurla, M.; Tolvanen, S.; Efimov, A.; Hupa, L.; Peltonen, J.; Murzin, D. Yu. The physicochemical and catalytic properties of clay extrudates in cyclization of citronellal. Appl. Catal. A: Gen. 2022, 629, 118426,  DOI: 10.1016/j.apcata.2021.118426
      29
      The physicochemical and catalytic properties of clay extrudates in cyclization of citronellal
      Vajglova, Zuzana; Simakova, Irina L.; Eranen, Kari; Maki-Arvela, Paivi; Kumar, Narendra; Peurla, Markus; Tolvanen, Stiina; Efimov, Alexander; Hupa, Leena; Peltonen, Jouko; Murzin, Dmitry Yu.
      Applied Catalysis, A: General (2022), 629 (), 118426CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      Four clay materials, namely, bentonite, bleaching earth, attapulgite and sepiolite, were shaped into the cylindrical body by extrusion. Clays were characterized in depth by TEM, SEM-EDX, N2 physisorption, pyridine FTIR, pH measurements, contact angle measurements, 27Al MAS NMR, and the crush test. Catalytic properties were investigated in the citronellal cyclization as a model reaction. The reaction was performed in the trickle-bed reactor at 70°C, 10 bar of Ar with 0.086 M initial citronellal concn. in cyclohexane. The best results were obtained over attapulgite with isopulegols yield of 24% and stereoselectivity to the desired isopulegol isomer of 61%. Attapulgite had the highest meso-to-micropore vol. ratio, the highest basicity, a low Bronsted-to-Lewis acid sites ratio, and the lowest amt. of Bronsted acid sites compared to other extrudates. In addn., same clay exhibited the highest mech. strength of extrudates.
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    30. 30
      Emeis, C. A. Determination of integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on solid acid catalysts. J. Catal. 1993, 141, 347– 354,  DOI: 10.1006/jcat.1993.1145
      30
      Determination of integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on solid acid catalysts
      Emeis, C. A.
      Journal of Catalysis (1993), 141 (2), 347-54CODEN: JCTLA5; ISSN:0021-9517.
      Integrated molar extinction coeffs. were detd. for IR absorption bands of pyridine adsorbed on acid sites in Si/Al-based catalysts. The IR spectra of five zeolites and two amorphous silica-aluminas were recorded during quant. dosing of pyridine gas at 150°. The integrated mol. extinction coeffs. were calcd. assuming that they did not depend on the catalyst or the strength of the acid site. The resulting values were 1.67 cm/μmol for the 1545-cm-1 band characteristic of pyridine on a Broensted acid site and 2.22 cm/μmol for the 1455-cm-1 band of pyridine on a Lewis acid site. The 95% confidence limits were estd. at ±15%. Subsequent anal. of the data provided no evidence for a dependence of the integrated coeffs. on the catalyst or the strength of the site. The measurements gave indications for differences between the rates of reaction of Broensted and Lewis acid sites with pyridine.
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    31. 31
      Powder Diffraction File database PDF-2; International Centre for Diffraction Data: USA, 2009.
      There is no corresponding record for this reference.
    32. 32
      Vajglova, Z.; Kumar, N.; Mäki-Arvela, P.; Eränen, K.; Peurla, M.; Hupa, L.; Nurmi, M.; Toivakka, M.; Murzin, D. Y. Synthesis and physicochemical characterization of shaped catalysts of β and Y zeolites for cyclization of citronellal. Ind. Eng. Chem. Res. 2019, 58 (39), 18084– 18096,  DOI: 10.1021/acs.iecr.9b02829
      32
      Synthesis and Physicochemical Characterization of Shaped Catalysts of β and Y Zeolites for Cyclization of Citronellal
      Vajglova, Zuzana; Kumar, Narendra; Maki-Arvela, Paivi; Eranen, Kari; Peurla, Markus; Hupa, Leena; Nurmi, Maristiina; Toivakka, Martti; Murzin, Dmitry Yu
      Industrial & Engineering Chemistry Research (2019), 58 (39), 18084-18096CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
      Continuous cyclization of citronellal over zeolite-based extrudates was performed in a trickle-bed reactor at 35-70 °C and 10 bar of argon. Catalytic results were correlated with the physicochem. properties of the shaped catalyst prepd. by extrusion of β or Y zeolites with binders. Rheol. tests were used to elucidate the flow properties of a catalytic slurry and relate them with the extrusion performance. This study revealed that application of methylcellulose and bentonite binder modified the textural and acidic properties of the final extrudates. The main product was (-)-isopulegol at all temps. with selectivity remaining quite const. with time-onstream. The results illustrated that a binder such as bentonite cannot be considered inert. The mass-transfer limitations obsd. in extrudates did not significantly influence selectivity to the desired pulegols. This study also showed that a direct transfer of the batch reactor data to industrial continuous operation in citronellal cyclization is not straightforward.
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    33. 33
      Boudriche, L.; Chamayou, A.; Calvet, R.; Hamdi, B.; Balard, H. Influence of different dry milling processes on the properties of an attapulgite clay, contribution of inverse gas chromatography. Powder technology 2014, 254, 352– 363,  DOI: 10.1016/j.powtec.2014.01.041
      33
      Influence of different dry milling processes on the properties of attapulgitic clay, contribution of inverse gas chromatography
      Boudriche, L.; Chamayou, A.; Calvet, R.; Hamdi, B.; Balard, H.
      Powder Technology (2014), 254 (), 352-363CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)
      The effect of dry milling processes on the surface properties of an attapulgitic clay, also called palygorskite, was investigated by carrying out expts. with different types of grinding devices. Ground products were then characterized by size measurement, SEM, X-ray diffraction, adsorption-desorption of N2 and inverse gas chromatog. at infinite diln. (IGC-ID) as well as finite concn. conditions (IGC-FC). These analyses were performed to evaluate the changes in particle size distribution, morphol., crystallinity and surface properties of attapulgite powder, resp. Among the tested dry grinding devices, grinding in an air jet mill (Alpine 50 AS) and a vibratory ball mill (Pulverisette 0) led to the most significant particle size redn. SEM photomicrographs showed that a breakage of the fibrous structure took place during dry grinding. Moreover, long grinding in Pulverisette 0 resulted in the complete destruction of fiber morphol. followed by agglomeration. XRD anal. showed that whatever the grinding process, the microstructure of the attapulgite was not affected. IGC confirmed that only grinding in Pulverisette 0 affected the surface properties notably. In this case, the most significant decreases were obsd. in the dispersive component of the surface energy (164 to 116 mJ/m2) and in the sp. surface area obtained with the octane probe (114.5 m2/g to 62.6 m2/g) by IGC-ID and IGC-FC, resp. At the same time, a modification of the distribution functions of the adsorption energies (DFAE), giving information about surface heterogeneity, was noticed.
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    34. 34
      Nugraha, R. E.; Prasetyoko, D.; Bahruji, H.; Suprapto, S.; Asikin-Mijan, N.; Oetami, T. P.; Dai-Veit, N. Vo.; Taufiq-Yap, Y. H. Lewis acid Ni/Al-MCM-41 catalysts for H2-free deoxygenation of Reutealis trisperma oil to biofuels. RSC Adv. 2021, 11 (36), 21885– 21896,  DOI: 10.1039/D1RA03145G
      34
      Lewis acid Ni/Al-MCM-41 catalysts for H2-free deoxygenation of Reutealis trisperma oil to biofuels
      Nugraha, Reva Edra; Prasetyoko, Didik; Bahruji, Hasliza; Suprapto, Suprapto; Asikin-Mijan, Nurul; Oetami, Titie Prapti; Jalil, Aishah Abdul; Vo, Dai-Viet N.; Taufiq-Yap, Yun Hin
      RSC Advances (2021), 11 (36), 21885-21896CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      The activity of mesoporous Al-MCM-41 for deoxygenation of Reutealis trisperma oil (RTO) was enhanced via modification with NiO nanoparticles. Deoxygenation at atm. pressure and under H2 free conditions required acid catalysts to ensure the removal of the oxygenated fragments in triglycerides to form liq. hydrocarbons. NiO at different wt. loadings was impregnated onto Al-MCM-41 and the changes of Lewis/Bronsted acidity and mesoporosity of the catalysts were investigated. The activity of Al-MCM-41 was enhanced when impregnated with NiO due to the increase of Lewis acidity originating from NiO nanoparticles and the mesoporosity of Al-MCM-41. Increasing the NiO loading enhanced the Lewis acidity but not Bronsted acidity, leading to a higher conversion toward liq. hydrocarbon yield. Impregnation with 10% of NiO on Al-MCM-41 increased the conversion of RTO to hydrocarbons via the deoxygenation pathway and reduced the products from cracking reaction, consequently enhancing the green diesel (C11-C18) hydrocarbon products.
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    35. 35
      Yang, L.; Huang, J.; Cen, J.; Chen, D. L.; Zeng, H.; Rui, Z.; Luque, R.; Duan, P. Lewis acid (Ni 2+, Co 2+/3+ or Zn 2+) modified electron-deficient Ir 4+ in IrO 2/CuO for promoting methane oxidation to ethanol and methanol. J. Mater. Chem. A 2021, 9 (11), 7094– 7101,  DOI: 10.1039/D0TA10842A
      35
      Lewis acid (Ni2+, Co2+/3+ or Zn2+) modified electron-deficient Ir4+ in IrO2/CuO for promoting methane oxidation to ethanol and methanol
      Yang, Le; Huang, Jinxu; Cen, Jie; Chen, De-Li; Zeng, Hui; Rui, Zebao; Luque, Rafael; Duan, Peigao
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2021), 9 (11), 7094-7101CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      This work delineates the first attempt to tune the product distribution between methanol and ethanol in the direct oxidn. of methane reaction by incorporating Lewis acids Ni2+, Co2+/3+ or Zn2+ into IrO2/CuO. The electrophilicity of Ir4+ and the (LAS-BAS)/LAS ratio (LAS: Lewis acid sites, BAS: Bronsted acid sites) are demonstrated to be two reactivity descriptors motivating CH4 activation and ethanol formation, resp. Electron-deficient Ir4+ motivates enriched *CH3 concn. and subsequent C-C coupling for C2H4 formation, while the Lewis acid promotes ethanol formation from C2H4 involving lattice O and H2O. The ethanol selectivity presents a quasi-linear relationship with (LAS-BAS)/LAS.
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    36. 36
      Wei, Z.; Xia, T.; Ma, J.; Feng, W.; Dai, J.; Wang, Q.; Yan, P. Investigation of the lattice expansion for Ni nanoparticles. Mater. Charact. 2007, 58 (10), 1019– 1024,  DOI: 10.1016/j.matchar.2006.08.004
      36
      Investigation of the lattice expansion for Ni nanoparticles
      Wei, Zhiqiang; Xia, Tiandong; Ma, Jun; Feng, Wangjun; Dai, Jianfeng; Wang, Qing; Yan, Pengxun
      Materials Characterization (2007), 58 (10), 1019-1024CODEN: MACHEX; ISSN:1044-5803. (Elsevier B.V.)
      Nickel nanoparticles with various grain sizes were successfully prepd. by anodic arc discharge plasma method. The samples prepd. by this method were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected-area electron diffraction (SAED) to det. the crystal structure, lattice parameter, morphol. and particle size. The expt. results indicate that the crystal structure of the samples is fcc. structure as same as the bulk materials. The lattice parameters for Ni nanoparticles are always larger than the equil. values of the perfect single crystal lattice resp., the lattice parameter increase significantly with the decrease of the grain size, the lattice expansion was found, and the expansion quantity of the lattice parameter is in direct proportion to the reciprocal of grain size. The values of the unit cell vol. increase remarkably with the decrease of the grain size. The lattice expansion is the result of the interfacial energy and surface tension mutual attraction of Ni nanoparticles, this phenomenon can be explained according to the thermodn. theory.
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    37. 37
      Quindimil, A.; De-La-Torre, U.; Pereda-Ayo, B.; Gonzalez-Marcos, J. A.; Gonzalez-Velasco, J. R. Ni catalysts with La as promoter supported over Y-and Beta-zeolites for CO2 methanation. Appl. Catal. B: Env. 2018, 238, 393– 403,  DOI: 10.1016/j.apcatb.2018.07.034
      37
      Ni catalysts with La as promoter supported over Y- and BETA- zeolites for CO2 methanation
      Quindimil, Adrian; De-La-Torre, Unai; Pereda-Ayo, Benat; Gonzalez-Marcos, Jose A.; Gonzalez-Velasco, Juan R.
      Applied Catalysis, B: Environmental (2018), 238 (), 393-403CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      The hydrogenation of CO2 into methane is considered a plausible process to storage renewable energy in form of methane and reducing CO2 anthropogenic emissions. Microporous solids such as zeolites have been scarcely studied yet for this application. This study aims to evaluate and compare the catalytic performance of zeolite (Y and BETA) supported Ni catalysts for CO2 methanation. The physicochem. properties of the prepd. catalysts were characterized by XRD, BET, CO2-TPD, H2-TPR and XPS, and CO2 methanation was carried out in a tubular reactor at conditions of H2/CO2 = 4, GHSV = 10,000 h-1 and temps. from 200 to 500 C. Neutralization of both zeolites by Na+ ion exchange enhanced the CO2 conversion as weaker CO2 adsorption sites and reducibility are promoted. BETA resulted in a better support than Y zeolite due to the presence of more easily reducible Ni2+, which acts as precursor of active Ni° accessible under reaction conditions. Indeed, the surface basicity and Ni dispersion of Ni/BETA catalysts were considerably promoted by impregnation of different loads of La2O3, which increase the amt. of CO2 adsorption sites and even active hydrogenation sites resulting in a significant increase of activity and selectivity towards CH4. The optimal Ni-10%La2O3/Na-BETA formulation resulted in T50 of 320°C, CO2 conversion of 65% at 350 °C, with almost total selectivity to CH4 and maintaining stability for more than 24 h.
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    38. 38
      Wang, Y.; Liang, D.; Wang, C.; Chen, M.; Tang, Z.; Hu, J.; Yang, Z.; Zhang, H.; Wang, J.; Liu, S. Influence of calcination temperature of Ni/attapulgite on hydrogen production by steam reforming ethanol. Renew. Energy 2020, 160, 597– 611,  DOI: 10.1016/j.renene.2020.06.126
      40
      Influence of calcination temperature of Ni/Attapulgite on hydrogen production by steam reforming ethanol
      Wang, Yishuang; Liang, Defang; Wang, Chunsheng; Chen, Mingqiang; Tang, Zhiyuan; Hu, Jiaxin; Yang, Zhonglian; Zhang, Han; Wang, Jun; Liu, Shaomin
      Renewable Energy (2020), 160 (), 597-611CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
      Sustainable hydrogen prodn. can be realized by steam reforming ethanol (SRE) derived from renewable biomass, but develop high-efficiency and sixpenny catalyst is a major challenge. Attapulgite-supported nickel catalyst (Ni/ATP) exhibits promising potential for SRE for hydrogen prodn. The influence of calcination temp. (CT) on the microscopic morphol. and physicochem. properties of Ni/ATP was investigated by various technologies. The results revealed that increasing CT could improve metal-support interaction (MSI) and surface Ni active species content. However, extortionate CT (>700°C) significantly led to catalyst structure collapse and crystal phase transfer accompanied with the formation of new species, which enhanced the MSI and reduced the surface Nio species content. The outcomes of SRE expts. demonstrated that Ni/ATP-C600 presented maximal activity and H2 yield due to its higher surface contents of the Nio active component and Ni/ATP-C900 exhibited unique stability owing to its stronger MSI. Hence, the coordination between active species distribution and MSI in Ni/ATP can be adjusted by CT. Addnl. coke deposits on spent Ni/ATP-C300 were identified with quite arom. species, which strongly attract to the surface of catalyst and encapsulate active site, while that on used Ni/ATP-C900 had higher degrees of graphitization, but did not affect the stability.
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    39. 39
      Bertero, N. M.; Trasarti, A. F.; Apesteguía, C. R.; Marchi, A. J. Liquid-phase dehydration of 1-phenylethanol on solid acids: Influence of catalyst acidity and pore structure. Appl. Catal. A: Gen. 2013, 458, 28– 38,  DOI: 10.1016/j.apcata.2013.03.018
      38
      Liquid-phase dehydration of 1-phenylethanol on solid acids: Influence of catalyst acidity and pore structure
      Bertero, Nicolas M.; Trasarti, Andres F.; Apesteguia, Carlos R.; Marchi, Alberto J.
      Applied Catalysis, A: General (2013), 458 (), 28-38CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      The liq.-phase dehydration of 1-phenylethanol (PHE) over different solid acids was studied at 363 K using cyclohexane as solvent. It was found that the catalyst activity and selectivity strongly depended on: (1) the nature, strength and d. of acid sites and (2) the textural properties of the catalyst. Catalysts contg. mainly surface Bronsted acid sites of medium-high strength, such as Amberlyst 15, HPA/SiO2, and HMOR zeolite, showed low initial styrene (STY) selectivity because the PHE dehydrated to alpha-methylbenzyl ether (AME) at higher or similar rates than to STY. Both primary products, STY and AME, were consecutively transformed to other heavy products (HP). Catalysts contg. predominantly Lewis acid sites, such as ZnO/SiO2, Al-MCM-41 and SiO2-Al2O3, selectively transformed PHE to AME. The ether can be sequentially converted to STY and HP, depending on the solid acidity. Solid acids having strong surface Lewis sites, e.g. SiO2-Al2O3, showed high dehydration rate and HP prodn. Samples contg. exclusively weak Lewis acid sites, e.g. γ-Al2O3, were not active in the PHE dehydration at 363 K. Only zeolites HZSM-5, HBEA and HY, with similar surface d. of Bronsted and Lewis acid sites, converted selectively PHE into STY, giving initial STY selectivities between 83 and 96%. However, HY zeolite was rapidly deactivated due to the blockage of its microporous structure by bulky compds. formed inside the large cages of 13 Å. Instead, on HBEA, STY was converted to HP that can diffuse through the solid microporous structure. Then, the selectivity to STY was drastically reduced with time. A const. and high STY selectivity at total PHE conversion was only obtained with HZSM-5. The pore size of this zeolite is enough to allow the diffusion and conversion of PHE into STY, but it is not adequate to form the surface intermediates leading to AME and HP. Thus, it was proved that: (1) the surface Bronsted to Lewis ratio strongly influences the initial selectivity in the liq.-phase PHE dehydration; (2) a similar Bronsted to Lewis ratio on the solid acid surface is necessary to obtain high initial selectivity to STY; and (3) the right porous structure is crucial to avoid HP prodn. and keep const. the STY selectivity at high PHE conversion. From the exptl. results obtained in this work, a mechanistic approach was proposed in order to explain the influence of both acid site nature and pore size on the selective PHE dehydration in liq. phase.
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    40. 40
      Chuah, G. K.; Liu, S. H.; Jaenicke, S.; Harrison, L. J. Cyclisation of citronellal to isopulegol catalysed by hydrous zirconia and other solid acids. J. Catal. 2001, 200 (2), 352– 359,  DOI: 10.1006/jcat.2001.3208
      39
      Cyclization of Citronellal to Isopulegol Catalyzed by Hydrous Zirconia and Other Solid Acids
      Chuah, G. K.; Liu, S. H.; Jaenicke, S.; Harrison, L. J.
      Journal of Catalysis (2001), 200 (2), 352-359CODEN: JCTLA5; ISSN:0021-9517. (Academic Press)
      A review with 29 refs. The cyclization of citronellal to isopulegol is an important step in the synthesis of menthol. Several zirconia-based catalysts were evaluated for this reaction. Zirconium hydroxides and phosphated zirconia had very good activity and selectivity. Ammonia TPD and pyridine IR studies indicate the presence of strong Lewis together with weak Bronsted acid sites. Other strong acids like sulfated zirconia, Amberlyst, and Nafion were very active but the selectivity toward isopulegol was poor. They catalyzed side reactions such as dehydration, cracking, and etherification of isopulegol. Silica, with only weak Lewis acidity, showed very low activity. The presence of both Lewis and Bronsted sites is therefore essential for the reaction. A reaction mechanism is proposed where the citronellal mol. binds to a zirconium Lewis acid site via the aldehyde oxygen and the π-electrons of the double bond so that the right configuration is attained for cyclization. Subsequent protonation of the aldehyde via a neighboring Bronsted acid site initiates the cyclization to isopulegol. (c) 2001 Academic Press.
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.iecr.2c02345.

    • Catalyst characterization: pore size distribution, XRD of extrudates. Catalytic data: selectivity to desired menthol as function of conversion, concentration of menthol vs concentration of 3,7-dimethyloctanol and their ratio vs conversion (PDF)


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