Operando Determination of the Thermal Decomposition of Supported Ionic Liquids by a Radio-Frequency-Based MethodClick to copy article linkArticle link copied!
- Marie-Luise Anke*Marie-Luise Anke*E-mail: [email protected]Department of Chemical Engineering and Department of Functional Materials, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, GermanyMore by Marie-Luise Anke
- Martin HämmerleMartin HämmerleDepartment of Functional Materials, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, GermanyMore by Martin Hämmerle
- Ralf MoosRalf MoosDepartment of Functional Materials, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, GermanyMore by Ralf Moos
- Andreas JessAndreas JessDepartment of Chemical Engineering, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, GermanyMore by Andreas Jess
Abstract
The analysis of the thermal stability of supported ionic liquids (ILs) is of great interest for their application in catalysis. However, thermogravimetric (TG) measurements are very time-consuming, destructive, and cannot be conducted operando. Therefore, a new radio-frequency (RF)-based method is presented that analyzes the electrical properties of supported ILs in the microwave range and can detect a possible IL mass loss caused by evaporation or decomposition. In this study, the decomposition of supported 1-butyl-3-methylimidazolium dimethylphosphate ([BMIM][DMP]) with and without palladium (as an active metal) is investigated operando during the selective hydrogenation of 1,3-butadiene. In addition to volatile decomposition products, solid products are formed, which remain on the carrier. These solid products impair the activity of the Pd catalyst. Using the RF-based method, a distinction can be made between “intact” IL and the solid decomposition products because the electrical properties of both substances differ substantially. In contrast, the destructive TG analysis only measures the mass loss by the formation of gaseous decomposition products and thus cannot distinguish between “intact” IL and the solid decomposition products of [BMIM][DMP]. In addition, a model of the thermal decomposition which depicts the measured mass losses well is presented.
Introduction
Results and Discussion
RF Measurements of Supported [BMIM][DMP] with and without Palladium
Analysis of the Thermal Decomposition of the IL by Thermogravimetric Investigation
RF-Based Analysis of the Thermal Decomposition of the Supported IL without Pd
Simulation of the Thermal Decomposition Supported [BMIM][DMP]
k1 (175 °C) | 6.7 × 10–6 s–1 |
k2 (175 °C) | 4.8 × 10–6 s–1 |
k3 (175 °C) | 1.7 × 10–7 s–1 |
EA,1 | 78 kJ mol–1 |
EA,2 | 131 kJ mol–1 |
EA,3 | 112 kJ mol–1 |
k0,1 | 9.1 × 103 s–1 |
k0,2 | 9.2 × 109 s–1 |
k0,3 | 1.7 × 106 s–1 |
Influence of Thermal Decomposition of [BMIM][DMP] on Activity and Selectivity of the Pd-SCILL-Catalyst
NMR Measurements
(a) | [BMIM][DMP] supported on silica | ||||
(b) | [BMIM][DMP] supported on silica, with the IL partially leached out from the support with DCM (the IL could not be completely removed) | ||||
(c) | [BMIM][DMP] supported on silica, thermally aged at 175 °C for 60 h | ||||
(d) | [BMIM][DMP] supported on silica, thermally aged at 175 °C for 60 h and then partially leached out from the support with DCM (the IL could not be completely removed) |
Conclusions
Experimental Section
Measurement Setup and Calculation of the Complex Permittivity
Preparation and Characterization of Samples
silica 150 Å powder | |
---|---|
pore surface ABET | 308 m2 g–1 |
specific pore volume Vpore,0 | 1.05 cm3 g–1 |
mean pore diameter dpore,m | 14 nm |
diameter of the particles dp | 250 μm |
1-butyl-3-methylimidazolium dimethylphosphate ([BMIM][DMP]) | |
---|---|
density ρIL | 1.18 g cm–1 (20) |
molar mass MIL | 264 g mol–1 (20) |
vapor pressure (taken from [DMIM][DMP]) pvap,IL | 6.7 × 10–6 Pa (373 K) (20) |
0.2 mPa (410 K) (20) | |
decomposition temperature Tdecomposition (mass loss 1%/month) | 137 °C (20) |
water content | <1 wt % |
porous carrier | silica 150 Å |
precursor | palladium(II)nitrate hydrate |
solvent | acetone |
calcination parameter | air |
1 K min–1 | |
θmax = 350 °C | |
4 h | |
parameter of reduction | 10% H2 in N2 |
2 K min–1 | |
θmax = 350 °C | |
4 h |
Analysis of Thermal Decomposition
temperature of decomposing | 175 °C |
temperature of RF measurements | 20 °C |
time of decomposition | 60 h (35 h, measurement with Pd) |
nitrogen volume stream | 20 L h–1 (STP) |
length/diameter of the fixed bed | 18 mm/10 mm |
pressure | 1 bar |
Selective Hydrogenation of 1,3-Butadiene to Butene
temperature | 50 °C |
total pressure | 1 bar |
partial pressure butadiene | 5 mbar |
partial pressure hydrogen | 100 mbar |
palladium content | 0.3 wt % |
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b02421.
Diagram of a TG analysis with the carrier gases nitrogen and helium to distinguish between mass loss due to evaporation or due to thermal decomposition (PDF)
Terms & Conditions
Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.
Acknowledgments
The authors are indebted to the German Research Foundation (DFG) for financial support (Je 257/21-1 and Mo 1060/27-1). The authors thank Jörg Gerchau for help with the measurement setup, Birgit Brunner for the ICP–OES analysis, Beate Bojer for the 31P-solid state NMR, and Ulrike Lacher for the 1H NMR measurements.
[BMIM][DMP] | 1-butyl-3-methylimidazolium dimethylphosphate |
[DMIM][DMP] | 1,3-dimethylimidazolium dimethylphosphate |
[EMIM][NTf2] | 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide |
IL | ionic liquid |
Pd | palladium |
RF | radio frequency |
SCILL | solid catalyst with ionic liquid layer |
SCR | selective catalytic reduction |
SILP | supported ionic liquid phase |
TG | thermogravimetry/thermogravimetric |
References
This article references 28 other publications.
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- 7Kernchen, U.; Etzold, B.; Korth, W.; Jess, A. Solid Catalyst with Ionic Liquid Layer (SCILL) - A New Concept to Improve Selectivity Illustrated by Hydrogenation of Cyclooctadiene. Chem. Eng. Technol. 2007, 30, 985– 994, DOI: 10.1002/ceat.200700050Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXpt12qur0%253D&md5=9faa375aa5e622c4406b1d3acbc00294Solid catalyst with ionic liquid layer (SCILL) - a new concept to improve selectivity illustrated by hydrogenation of cyclooctadieneKernchen, Uwe; Etzold, Bastian; Korth, Wolfgang; Jess, AndreasChemical Engineering & Technology (2007), 30 (8), 985-994CODEN: CETEER; ISSN:0930-7516. (Wiley-VCH Verlag GmbH & Co. KGaA)A new concept of a solid catalyst with ionic liq. layer (SCILL) as a novel method to improve the selectivity of heterogeneous catalysts is presented. The sequential hydrogenation of cyclooctadiene (COD) to cyclooctene (COE) and cyclooctane on a com. Ni catalyst coated with the ionic liq. [BMIM] [n-C8H17OSO3] was tested as first model system. Compared to the original catalyst, the coating of the internal surface with the ionic liq. (IL) strongly enhances the max. intrinsic COE yield from 40 to 70%. This effect is already achieved for a pore filling degree of only 10% and cannot be explained by pore diffusion, as shown by expts. with different particle sizes and theor. considerations. The IL layer is very robust and no leaching into the org. phase was detectable.
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- 13Müller, N.; Reiß, S.; Fremerey, P.; Jess, A.; Moos, R. Initial tests to detect quantitatively the coke loading of reforming catalysts by a contactless microwave method. Chem. Eng. Process. 2011, 50, 729– 731, DOI: 10.1016/j.cep.2011.07.002Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVagt73L&md5=bb1ba7ea1585a156e2cb8507b40af727Initial tests to detect quantitatively the coke loading of reforming catalysts by a contactless microwave methodMueller, Norbert; Reiss, Sebastian; Fremerey, Peter; Jess, Andreas; Moos, RalfChemical Engineering and Processing (2011), 50 (8), 729-731CODEN: CENPEU; ISSN:0255-2701. (Elsevier B.V.)Coke formation affects the activity of catalysts and the product spectra in refinery and petrochem. processes. In previous works, it was shown that the coke content in heterogeneous catalysts can be monitored in-situ by measuring the elec. impedance of single catalyst pellets. In this initial study it should be clarified whether in principle it is possible to apply a contactless microwave-based measuring method to quant. detect coke in heterogeneous catalysts. The advantage would be that a contactless method is more suitable for an industrial application since only one elec. insulated feed-through is necessary to det. the coke load in situ in a reactor with its rough reaction conditions (up to 500 °C, 30-50 bar, high H2 partial pressure).
- 14Rauch, D.; Fremerey, P.; Jess, A.; Moos, R. In situ detection of coke deposits on fixed-bed catalysts by a radio frequency-based method. Sens. Actuators, B 2013, 181, 681– 689, DOI: 10.1016/j.snb.2013.01.022Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXlt1ChsL4%253D&md5=ff36285c0673c16514f407d80d16a2cdIn situ detection of coke deposits on fixed-bed catalysts by a radio frequency-based methodRauch, Dieter; Fremerey, Peter; Jess, Andreas; Moos, RalfSensors and Actuators, B: Chemical (2013), 181 (), 681-689CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)The aim of this work is to study whether a contactless radio frequency-based method is suitable to monitor both coking and regeneration (coke burn-off) of industrial fixed-bed catalysts directly and in operando. The tubular steel reactor serves as an electromagnetic cavity and two waveguide feeds (coaxial antennas) are used to impress and receive electromagnetic waves between 1 and 20 GHz. Shifts of the resonance frequencies mirror the coke loading in the lowly loaded state and strongly decreasing power transmission over the entire frequency range goes along with increasing coke load at higher coke loadings. Both the locally homogeneously distributed coking process and the coke burn-off process that starts in the reactor front and moves through the reactor can be obsd. by the radio frequency-based method.
- 15Dietrich, M.; Hagen, G.; Reitmeier, W.; Burger, K.; Hien, M.; Grass, P.; Kubinski, D.; Visser, J.; Moos, R. Radio-Frequency-Controlled Urea Dosing for NH3-SCR Catalysts: NH3 Storage Influence to Catalyst Performance under Transient Conditions. Sensors 2017, 17, 2746, DOI: 10.3390/s17122746Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsFeksrjI&md5=e2dec8f81778c324c9394ced69cde237Radio-frequency-controlled urea dosing for NH3-SCR Catalysts: NH3 storage influence to catalyst performance under transient conditionsDietrich, Markus; Hagen, Gunter; Reitmeier, Willibald; Burger, Katharina; Hien, Markus; Grass, Philippe; Kubinski, David; Visser, Jaco; Moos, RalfSensors (2017), 17 (12), 2746/1-2746/17CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)Current developments in exhaust gas aftertreatment led to a huge mistrust in diesel driven passenger cars due to their NOx emissions being too high. The selective catalytic redn. (SCR) with ammonia (NH3) as reducing agent is the only approach today with the capability to meet upcoming emission limits. Therefore, the radio-frequency-based (RF) catalyst state detn. to monitor the NH3 loading on SCR catalysts has a huge potential in emission redn. Recent work on this topic proved the basic capability of this technique under realistic conditions on an engine test bench. In these studies, an RF system calibration for the serial type SCR catalyst Cu-SSZ-13 was developed and different approaches for a temp. dependent NH3 storage were detd. This paper continues this work and uses a fully calibrated RF-SCR system under transient conditions to compare different directly measured and controlled NH3 storage levels, and NH3 target curves. It could be clearly demonstrated that the right NH3 target curve, together with a direct control on the desired level by the RF system, is able to operate the SCR system with the max. possible NOx conversion efficiency and without NH3 slip.
- 16Moos, R.; Rauch, D.; Votsmeier, M.; Kubinski, D. Review on Radio Frequency Based Monitoring of SCR and Three Way Catalysts. Top. Catal. 2016, 59, 961– 969, DOI: 10.1007/s11244-016-0575-1Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xnslahsr0%253D&md5=6abea23607aab556b9b2c7a176bb6202Review on Radio Frequency Based Monitoring of SCR and Three Way CatalystsMoos, R.; Rauch, D.; Votsmeier, M.; Kubinski, D.Topics in Catalysis (2016), 59 (10-12), 961-969CODEN: TOCAFI; ISSN:1022-5528. (Springer)A review. Knowledge of the actual catalyst state plays a key role in automotive exhaust gas aftertreatment. The oxygen loading degree of three-way catalysts (TWC), the amt. of stored ammonia in selective redn. catalysts (SCR), or the NOx loading degree in NOx storage catalysts (NSC) are important parameters. Today, they are detd. indirectly and/or model-based, applying models that are typically calibrated by gas sensors installed up- and/or downstream of the catalysts. A novel approach to det. directly the catalyst state by microwaves (radio frequencies, rf) emerged recently. For this method, the catalyst housing serves as an elec. cavity resonator. As "sensor", one or two simple antennas are mounted in the canning. The elec. properties of the honeycomb include coating change with gas loading, affecting either the resonance frequencies or the power transmission. Such contactless-obtained information is strongly correlated with the catalyst state as will be discussed here for TWC and SCR systems. This contribution reviews the progress in the past 3 years that exceeds by far the status of initial studies.
- 17Fremerey, P.; Jess, A.; Moos, R. Why does the Conductivity of a Nickel Catalyst Increase during Sulfidation? An Exemplary Study Using an In Operando Sensor Device. Sensors 2015, 15, 27021– 27034, DOI: 10.3390/s151027021Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitFKnsL4%253D&md5=016401a27a785e98555eae74396ae9f4Why does the conductivity of a nickel catalyst increase during sulfidation? An exemplary study using an in operando sensor deviceFremerey, Peter; Jess, Andreas; Moos, RalfSensors (2015), 15 (10), 27021-27034CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)In order to study the sulfidation of a catalyst fixed bed, an in operando single pellet sensor was designed. A catalyst pellet from the fixed bed was elec. contacted and its elec. response was correlated with the catalyst behavior. For the sulfidation tests, a nickel catalyst was used and was sulfidized with H2S. This catalyst had a very low cond. in the reduced state. During sulfidation, the cond. of the catalyst increased by decades. A reaction from nickel to nickel sulfide occurred. This cond. increase by decades during sulfidation had not been expected since both nickel and nickel sulfides behave metallic. Only by assuming a percolation phenomenon that originates from a vol. increase of the nickel contacts when reacting to nickel sulfides, this effect can be explained. This assumption was supported by sulfidation tests with differently nickel loaded catalysts and it was quant. estd. by a general effective media theory. The single pellet sensor device for in operando investigation of sulfidation can be considered as a valuable tool to get further insights into catalysts under reaction conditions.
- 18Anke, M.-L.; Hämmerle, M.; Gerchau, J.; Moos, R.; Jess, A. Radio Frequency-Based In Situ Determination of the Mass Loss of Supported Ionic Liquids. Chem. Eng. Technol. 2017, 40, 1660– 1665, DOI: 10.1002/ceat.201700190Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXpt1ynsLo%253D&md5=4e0d7055319098496be0e0fae28c3351Radio frequency-based in situ determination of the mass loss of supported ionic liquidsAnke, Marie-Luise; Haemmerle, Martin; Gerchau, Joerg; Moos, Ralf; Jess, AndreasChemical Engineering & Technology (2017), 40 (9), 1660-1665CODEN: CETEER; ISSN:1521-4125. (Wiley-VCH Verlag GmbH & Co. KGaA)For tech. applications of supported ionic liqs. (ILs), the stability of the IL layers both with regard to thermal decompn. and to losses by evapn. is of great importance. An innovative radio frequency-based method is presented to det. the pore filling degree of supported ILs in situ and in a contactless way. As an example, the IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, which was supported on the internal surface of porous silica, was selected. The complex permittivity of the porous solid coated with the IL increases linearly with the IL pore filling degree. Therefore, the evapn. rate of the IL in a fixed bed could be measured in situ in the reactor.
- 19Anke, M.-L.; Hämmerle, M.; Jess, A.; Moos, R. Radio frequency- and impedance-based sensing of ionic liquids supported on porous carriers and their limitations. Sens. Actuators, B 2018, 273, 1564– 1571, DOI: 10.1016/j.snb.2018.07.036Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtlClu7bN&md5=d2b606a8300f37a90ed467e332b5ac9bRadio frequency- and impedance-based sensing of ionic liquids supported on porous carriers and their limitationsAnke, Marie-Luise; Haemmerle, Martin; Jess, Andreas; Moos, RalfSensors and Actuators, B: Chemical (2018), 273 (), 1564-1571CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)The anal. of the pore filling degree of supported ionic liqs. (ILs) is essential for industrial applications. In this study, two methods to detect the loading of IL supported on solid carriers are presented, a radio frequency-based one and one using impedance spectroscopy. With the radio frequency-based method, the pore filling degree can be detd. contactless and in operando. Some unexpected deviations at non-relevant high pore filling degrees occur. They can be explained by the combination of the results from the radio frequency-based method (at 1.2 GHz) and the impedance spectroscopy (at 1 Hz to 2 MHz). A transition from low polarization losses to high conduction losses occurs with increasing ionic liq. loading of the porous carrier.
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- 21Jess, A.; Wasserscheid, P. Chemical Technology; John Wiley & Sons: Weinheim, 2013; pp 200– 216.Google ScholarThere is no corresponding record for this reference.
- 22Tourillon, G.; Cassuto, A.; Jugnet, Y.; Massardier, J.; Bertolini, J. C. Buta-1,3-diene and but-1-ene chemisorption on Pt(111), Pd(111), Pd(110) and Pd50Cu50(111) as studied by UPS, NEXAFS and HREELS in relation to catalysis. J. Chem. Soc., Faraday Trans. 1996, 92, 4835– 4841, DOI: 10.1039/ft9969204835Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXktVaqug%253D%253D&md5=d0f4a4fb43db8ef244c6e441ac2d759c1,3-Butadiene and 1-butene chemisorption on Pt(111), Pd(111), Pd(110) and Pd50Cu50(111) as studied by UPS, NEXAFS and HREELS in relation to catalysisTourillon, G.; Cassuto, A.; Jugnet, Y.; Massardier, J.; Bertolini, J. C.Journal of the Chemical Society, Faraday Transactions (1996), 92 (23), 4835-4841CODEN: JCFTEV; ISSN:0956-5000. (Royal Society of Chemistry)Chemisorption of both 1,3-butadiene (I) and 1-butene (II) on Pt(111), Pd(111), Pd(110) and Pd50Cu50(111) samples was characterized by near-edge x-ray absorption fine structure (NEXAFS), UPS and high-resoln. electron energy loss spectroscopy (HREELS). I hydrogenation, studied on the same surfaces of Pd and Pd50Cu50, displays a very good selectivity in butenes and a higher activity compared to Pt(111). The Pd activity greatly depends on the surface cryst. orientation and is also influenced by alloying effects. The origin of these effects was sought in differences of chemisorption modes of I and II on the various surfaces: at 95 K, I and II are physisorbed on the different Pd-based single crystals. On Pt(111), I is π-bonded while II is di-σ-bonded. At 300 K, II either dehydrogenates into I on Pd(110) and Pd50Cu50(111) or very probably transforms into butylidyne on Pt(111) and on Pd(111) by analogy to C2H4 adsorbed on these (111) surfaces. I leads to a di-σ mode on Pt(111) and to a di-π one on the different Pd surfaces. The NEXAFS expts. reveal that the π1*-π2* splitting variations [2.0 eV on Pd(111), ∼2.4 eV on Pd(110) and Pd50Cu50(111), ∼2.7 eV on the condensed multilayer] agree with a decrease in the hydrocarbon-substrate interaction in the order Pd(111) > Pd(110) > Pd50Cu50(111). The activity would therefore obey the reverse sequence in agreement with the reactivity results.
- 23Kuhlmann, E.; Himmler, S.; Giebelhaus, H.; Wasserscheid, P. Imidazolium dialkylphosphates-a class of versatile, halogen-free and hydrolytically stable ionic liquids. Green Chem. 2007, 9, 233– 242, DOI: 10.1039/B611974CGoogle Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXitlKltLY%253D&md5=89be0321eed9465abd02942e15269568Imidazolium dialkylphosphates-a class of versatile, halogen-free and hydrolytically stable ionic liquidsKuhlmann, Esther; Himmler, Simone; Giebelhaus, Heidi; Wasserscheid, PeterGreen Chemistry (2007), 9 (3), 233-242CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)A systematic and detailed study on the synthesis and the properties of dialkylphosphate ionic liqs. is presented. This class of halogen-free ionic liqs. is easily available in high quality and great variability by direct alkylation of nucleophiles, such as 1-methylimidazole, 1-ethylimidazole, 1-butylimidazole and 1-(2-methoxyethyl)-imidazole with different trialkylphosphates, such as trimethylphosphate, triethylphosphate or tributylphosphate. In general, these dialkylphosphate ionic liqs. display very attractive physicochem. properties with great tech. potential, esp. in low temp. (<200°) applications with H2O present. For this specific application area, the materials described here clearly show superior properties compared with alkylsulfate ionic liqs. due to their obviously much higher hydrolytic stability.
- 24Kohli, P.; Blanchard, G. J. Probing Interfaces and Surface Reactions of Zirconium Phosphate/Phosphonate Multilayers Using 31P NMR Spectrometry. Langmuir 2000, 16, 695– 701, DOI: 10.1021/la990668vGoogle Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXmvVCjsrg%253D&md5=32ab4759226f803e0988823e25842922Probing Interfaces and Surface Reactions of Zirconium Phosphate/Phosphonate Multilayers Using 31P NMR SpectrometryKohli, P.; Blanchard, G. J.Langmuir (2000), 16 (2), 695-701CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)NMR 31P magic angle spinning (MAS) methods were used in characterization of zirconium phosphate/phosphonate (ZP) multilayer assemblies grown on SiOx. The reaction of silica with excess POCl3 and treatment with collidine results in both physisorbed and chemisorbed HxPO4(x-3) at the SiOx surface. The 31P NMR spectrum of zirconium phosphate grown from silica shows no residual Cl-contg. species, indicating essentially complete hydrolysis. The phosphate 31P resonances are broadened substantially upon complexation with Zr4+, and T1 data demonstrate the broadening to be inhomogeneous in nature. Data on maleimide-vinyl ether copolymer layers [Langmuir 1999, 15, 1418] confirm that hydrolysis/deprotection by bromotrimethylsilane is efficient in converting phosphoesters to the corresponding phosphorus oxyacid in the synthesis of multilayers. Comparison of polymer multilayers with the relatively more ordered bisphosphonic acid-based multilayers indicates that essentially the same interlayer bonding chem. is seen for both systems, with subtle differences arising as a consequence of the greater available free vol. and more extensive disorder within the polymer.
- 25Chen, L. F.; Ong, C. K.; Neo, C. P.; Varaden, V. V.; Varaden, V. K. Microwave Electronics: Measurements and Materials Characterisation; John Wiley & Sons: West Sussex, 2004; pp 11– 16.Google ScholarThere is no corresponding record for this reference.
- 26Slocombe, D.; Porch, A.; Bustarret, E.; Williams, O. A. Microwave properties of nanodiamond particles. Appl. Phys. Lett. 2013, 102, 244102, DOI: 10.1063/1.4809823Google ScholarThere is no corresponding record for this reference.
- 27Dietrich, M.; Rauch, D.; Porch, A.; Moos, R. A laboratory test setup for in situ measurements of the dielectric properties of catalyst powder samples under reaction conditions by microwave cavity perturbation: set up and initial tests. Sensors 2014, 14, 16856– 16868, DOI: 10.3390/s140916856Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitFSmsrs%253D&md5=ca2bcde30becb1e6d49360d1cf65c679A laboratory test setup for in situ measurements of the dielectric properties of catalyst powder samples under reaction conditions by microwave cavity perturbation: set up and initial testsDietrich, Markus; Rauch, Dieter; Porch, Adrian; Moos, RalfSensors (2014), 14 (9), 16856-16868CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)The catalytic behavior of zeolite catalysts for the ammonia-based selective catalytic redn. (SCR) of nitrogen oxides (NOX) depends strongly on the type of zeolite material. An essential precondition for SCR is a previous ammonia gas adsorption that occurs on acidic sites of the zeolite. In order to understand and develop SCR active materials, it is crucial to know the amt. of sorbed ammonia under reaction conditions. To support classical temp.-programmed desorption (TPD) expts., a correlation of the dielec. properties with the catalytic properties and the ammonia sorption under reaction conditions appears promising. In this work, a lab. test setup, which enables direct measurements of the dielec. properties of catalytic powder samples under a defined gas atm. and temp. by microwave cavity perturbation, has been developed. Based on previous investigations and computational simulations, a resonator cavity and a heating system were designed, installed and characterized. The resonator cavity is designed to operate in its TM010 mode at 1.2 GHz. The first measurement of the ammonia loading of an H-ZSM-5 zeolite confirmed the operating performance of the test setup at const. temps. of up to 300 °C. It showed how both real and imaginary parts of the relative complex permittivity are strongly correlated with the mass of stored ammonia.
- 28Dietrich, M.; Rauch, D.; Simon, U.; Porch, A.; Moos, R. Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: Correlation of dielectric properties with ammonia storage. J. Sens. Sens. Syst. 2015, 4, 263– 269, DOI: 10.5194/jsss-4-263-2015Google ScholarThere is no corresponding record for this reference.
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- Vladimir Malashchuk, Andreas Jess, Ralf Moos. Operando monitoring of gas drying by adsorption on supported ionic liquids: Determination of velocity of adsorption front by microwaves. Sensors and Actuators B: Chemical 2023, 380 , 133291. https://doi.org/10.1016/j.snb.2023.133291
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- 1Wasserscheid, P.; Keim, W. Ionic Liquids-New ″Solutions″ for Transition Metal Catalysis. Angew. Chem., Int. Ed. 2000, 39, 3772– 3789, DOI: 10.1002/1521-3773(20001103)39:21<3772::aid-anie3772>3.0.co;2-51https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXotFyqtLk%253D&md5=f2c9e3d403c8e2fbde6483f86b27db03Ionic liquids - new "solutions" for transition metal catalysisWasserscheid, Peter; Keim, WilhelmAngewandte Chemie, International Edition (2000), 39 (21), 3772-3789CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)A review with 98 refs. Ionic liqs. are salts that are liq. at low temp. (<100°C), which represent a new class of solvents with nonmol., ionic character. Even though the first representative has been known since 1914, ionic liqs. have only been investigated as solvents for transition metal catalysis in the past ten years. Publications to date show that replacing an org. solvent by an ionic liq. can lead to remarkable improvements in well-known processes. Ionic liqs. form biphasic systems with many org. product mixts. This gives rise to the possibility of a multiphase reaction procedure with easy isolation and recovery of homogeneous catalysts. In addn., ionic liqs. have practically no vapor pressure which facilitates product sepn. by distn. There are also indications that switching from a normal org. solvent to an ionic liq. can lead to novel and unusual chem. reactivity. This opens up a wide field for future investigations into this new class of solvents in catalytic applications.
- 2Holbrey, J. D.; Rogers, R. D. Physicochemical Properties of Ionic Liquids: Melting Points and Phase Diagrams. In Ionic Liquids in Synthesis; Wasserscheid, P., Welton, T., Eds.; John Wiley & Sons: Weinheim, 2008; pp 57– 72.There is no corresponding record for this reference.
- 3Welton, T. Room-Temperature Ionic Liquids. Solvents for Synthesis and Catalysis. Chem. Rev. 1999, 99, 2071– 2084, DOI: 10.1021/cr980032t3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXkt1artrw%253D&md5=e17d4c2a7f45438755b34161e86f24e6Room-Temperature Ionic Liquids. Solvents for Synthesis and CatalysisWelton, ThomasChemical Reviews (Washington, D. C.) (1999), 99 (8), 2071-2083CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review with 124 refs. covering org. reactions in alkylhalo- and haloaluminate ionic liqs.
- 4Wasserscheid, P. Outlook - the Thechnikal Prospect of Supported Ionic Liquid Materials. In Supported Ionic Liquids; Fehrmann, R., Riisager, A., Haumann, M., Eds.; John Wiley & Sons: Weinheim, 2013; pp 459– 465.There is no corresponding record for this reference.
- 5Heym, F.; Korth, W.; Thiessen, J.; Kern, C.; Jess, A. Evaporation and Decomposition Behavior of Pure and Supported Ionic Liquids under Thermal Stress. Chem. Ing. Tech. 2015, 87, 791– 802, DOI: 10.1002/cite.2014001395https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXlt1CgsLc%253D&md5=ce6c1e963cbaa5250ad81c95e6a3ebd6Evaporation and Decomposition Behavior of Pure and Supported Ionic Liquids under Thermal StressHeym, Florian; Korth, Wolfgang; Thiessen, Johannes; Kern, Christoph; Jess, AndreasChemie Ingenieur Technik (2015), 87 (6), 791-802CODEN: CITEAH; ISSN:0009-286X. (Wiley-VCH Verlag GmbH & Co. KGaA)Ionic liqs. (ILs) are widely discussed as alternative, sustainable solvents not only because of their unique chem. properties, but also because of their extremely low vapor pressure and - at least in some cases - relatively high thermal stability. In this work the vapor pressure data and kinetics of decompn. are presented for some selected pure and supported ionic liqs. Based on these results general strategies to det. the volatility and stability of pure and supported ILs as well as criteria for the max. operation temp. with regard to decompn. and evapn. are introduced.
- 6Riisagera, A.; Fehrmanna, R.; Haumannb, M.; Wasserscheidb, P. Supported ionic liquids: versatile reaction and separation media. Top. Catal. 2006, 40, 91– 102, DOI: 10.1007/s11244-006-0111-9There is no corresponding record for this reference.
- 7Kernchen, U.; Etzold, B.; Korth, W.; Jess, A. Solid Catalyst with Ionic Liquid Layer (SCILL) - A New Concept to Improve Selectivity Illustrated by Hydrogenation of Cyclooctadiene. Chem. Eng. Technol. 2007, 30, 985– 994, DOI: 10.1002/ceat.2007000507https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXpt12qur0%253D&md5=9faa375aa5e622c4406b1d3acbc00294Solid catalyst with ionic liquid layer (SCILL) - a new concept to improve selectivity illustrated by hydrogenation of cyclooctadieneKernchen, Uwe; Etzold, Bastian; Korth, Wolfgang; Jess, AndreasChemical Engineering & Technology (2007), 30 (8), 985-994CODEN: CETEER; ISSN:0930-7516. (Wiley-VCH Verlag GmbH & Co. KGaA)A new concept of a solid catalyst with ionic liq. layer (SCILL) as a novel method to improve the selectivity of heterogeneous catalysts is presented. The sequential hydrogenation of cyclooctadiene (COD) to cyclooctene (COE) and cyclooctane on a com. Ni catalyst coated with the ionic liq. [BMIM] [n-C8H17OSO3] was tested as first model system. Compared to the original catalyst, the coating of the internal surface with the ionic liq. (IL) strongly enhances the max. intrinsic COE yield from 40 to 70%. This effect is already achieved for a pore filling degree of only 10% and cannot be explained by pore diffusion, as shown by expts. with different particle sizes and theor. considerations. The IL layer is very robust and no leaching into the org. phase was detectable.
- 8Barth, T.; Korth, W.; Jess, A. Selectivity-Enhancing Effect of a SCILL Catalyst in Butadiene Hydrogenation. Chem. Eng. Technol. 2016, 40, 395– 404, DOI: 10.1002/ceat.201600140There is no corresponding record for this reference.
- 9Mangartz, T.; Häcker, L.; Korth, W.; Kern, C.; Jess, A. Improving the Selectivity to Butene Using a Solid Pd-Catalyst with an Ionic Liquid Laye (SCILL). Oil Gas Eur. Mag. 2014, 130, 84– 90There is no corresponding record for this reference.
- 10Supported Ionic Liquids; Fehrmann, R., Riisager, A., Haumann, M., Eds.; John Wiley & Sons: Weinheim, 2013.There is no corresponding record for this reference.
- 11Heym, F.; Kern, C.; Thiessen, J.; Jess, A. Transport Phenomena, Evaporation, and Thermal Stability of Supported Ionic Liquids. In Supported Ionic Liquids; Fehrmann, R., Riisager, A., Haumann, M., Eds.; John Wiley & Sons: Weinheim, 2013; pp 105– 143.There is no corresponding record for this reference.
- 12Bottom, R. Thermogravimetric Analysis. In Principles and Applications of Thermal Analysis; Gabbott, P., Ed.; Blackwell Publishing: Oxford, 2008; pp 87– 118.There is no corresponding record for this reference.
- 13Müller, N.; Reiß, S.; Fremerey, P.; Jess, A.; Moos, R. Initial tests to detect quantitatively the coke loading of reforming catalysts by a contactless microwave method. Chem. Eng. Process. 2011, 50, 729– 731, DOI: 10.1016/j.cep.2011.07.00213https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVagt73L&md5=bb1ba7ea1585a156e2cb8507b40af727Initial tests to detect quantitatively the coke loading of reforming catalysts by a contactless microwave methodMueller, Norbert; Reiss, Sebastian; Fremerey, Peter; Jess, Andreas; Moos, RalfChemical Engineering and Processing (2011), 50 (8), 729-731CODEN: CENPEU; ISSN:0255-2701. (Elsevier B.V.)Coke formation affects the activity of catalysts and the product spectra in refinery and petrochem. processes. In previous works, it was shown that the coke content in heterogeneous catalysts can be monitored in-situ by measuring the elec. impedance of single catalyst pellets. In this initial study it should be clarified whether in principle it is possible to apply a contactless microwave-based measuring method to quant. detect coke in heterogeneous catalysts. The advantage would be that a contactless method is more suitable for an industrial application since only one elec. insulated feed-through is necessary to det. the coke load in situ in a reactor with its rough reaction conditions (up to 500 °C, 30-50 bar, high H2 partial pressure).
- 14Rauch, D.; Fremerey, P.; Jess, A.; Moos, R. In situ detection of coke deposits on fixed-bed catalysts by a radio frequency-based method. Sens. Actuators, B 2013, 181, 681– 689, DOI: 10.1016/j.snb.2013.01.02214https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXlt1ChsL4%253D&md5=ff36285c0673c16514f407d80d16a2cdIn situ detection of coke deposits on fixed-bed catalysts by a radio frequency-based methodRauch, Dieter; Fremerey, Peter; Jess, Andreas; Moos, RalfSensors and Actuators, B: Chemical (2013), 181 (), 681-689CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)The aim of this work is to study whether a contactless radio frequency-based method is suitable to monitor both coking and regeneration (coke burn-off) of industrial fixed-bed catalysts directly and in operando. The tubular steel reactor serves as an electromagnetic cavity and two waveguide feeds (coaxial antennas) are used to impress and receive electromagnetic waves between 1 and 20 GHz. Shifts of the resonance frequencies mirror the coke loading in the lowly loaded state and strongly decreasing power transmission over the entire frequency range goes along with increasing coke load at higher coke loadings. Both the locally homogeneously distributed coking process and the coke burn-off process that starts in the reactor front and moves through the reactor can be obsd. by the radio frequency-based method.
- 15Dietrich, M.; Hagen, G.; Reitmeier, W.; Burger, K.; Hien, M.; Grass, P.; Kubinski, D.; Visser, J.; Moos, R. Radio-Frequency-Controlled Urea Dosing for NH3-SCR Catalysts: NH3 Storage Influence to Catalyst Performance under Transient Conditions. Sensors 2017, 17, 2746, DOI: 10.3390/s1712274615https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsFeksrjI&md5=e2dec8f81778c324c9394ced69cde237Radio-frequency-controlled urea dosing for NH3-SCR Catalysts: NH3 storage influence to catalyst performance under transient conditionsDietrich, Markus; Hagen, Gunter; Reitmeier, Willibald; Burger, Katharina; Hien, Markus; Grass, Philippe; Kubinski, David; Visser, Jaco; Moos, RalfSensors (2017), 17 (12), 2746/1-2746/17CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)Current developments in exhaust gas aftertreatment led to a huge mistrust in diesel driven passenger cars due to their NOx emissions being too high. The selective catalytic redn. (SCR) with ammonia (NH3) as reducing agent is the only approach today with the capability to meet upcoming emission limits. Therefore, the radio-frequency-based (RF) catalyst state detn. to monitor the NH3 loading on SCR catalysts has a huge potential in emission redn. Recent work on this topic proved the basic capability of this technique under realistic conditions on an engine test bench. In these studies, an RF system calibration for the serial type SCR catalyst Cu-SSZ-13 was developed and different approaches for a temp. dependent NH3 storage were detd. This paper continues this work and uses a fully calibrated RF-SCR system under transient conditions to compare different directly measured and controlled NH3 storage levels, and NH3 target curves. It could be clearly demonstrated that the right NH3 target curve, together with a direct control on the desired level by the RF system, is able to operate the SCR system with the max. possible NOx conversion efficiency and without NH3 slip.
- 16Moos, R.; Rauch, D.; Votsmeier, M.; Kubinski, D. Review on Radio Frequency Based Monitoring of SCR and Three Way Catalysts. Top. Catal. 2016, 59, 961– 969, DOI: 10.1007/s11244-016-0575-116https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xnslahsr0%253D&md5=6abea23607aab556b9b2c7a176bb6202Review on Radio Frequency Based Monitoring of SCR and Three Way CatalystsMoos, R.; Rauch, D.; Votsmeier, M.; Kubinski, D.Topics in Catalysis (2016), 59 (10-12), 961-969CODEN: TOCAFI; ISSN:1022-5528. (Springer)A review. Knowledge of the actual catalyst state plays a key role in automotive exhaust gas aftertreatment. The oxygen loading degree of three-way catalysts (TWC), the amt. of stored ammonia in selective redn. catalysts (SCR), or the NOx loading degree in NOx storage catalysts (NSC) are important parameters. Today, they are detd. indirectly and/or model-based, applying models that are typically calibrated by gas sensors installed up- and/or downstream of the catalysts. A novel approach to det. directly the catalyst state by microwaves (radio frequencies, rf) emerged recently. For this method, the catalyst housing serves as an elec. cavity resonator. As "sensor", one or two simple antennas are mounted in the canning. The elec. properties of the honeycomb include coating change with gas loading, affecting either the resonance frequencies or the power transmission. Such contactless-obtained information is strongly correlated with the catalyst state as will be discussed here for TWC and SCR systems. This contribution reviews the progress in the past 3 years that exceeds by far the status of initial studies.
- 17Fremerey, P.; Jess, A.; Moos, R. Why does the Conductivity of a Nickel Catalyst Increase during Sulfidation? An Exemplary Study Using an In Operando Sensor Device. Sensors 2015, 15, 27021– 27034, DOI: 10.3390/s15102702117https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitFKnsL4%253D&md5=016401a27a785e98555eae74396ae9f4Why does the conductivity of a nickel catalyst increase during sulfidation? An exemplary study using an in operando sensor deviceFremerey, Peter; Jess, Andreas; Moos, RalfSensors (2015), 15 (10), 27021-27034CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)In order to study the sulfidation of a catalyst fixed bed, an in operando single pellet sensor was designed. A catalyst pellet from the fixed bed was elec. contacted and its elec. response was correlated with the catalyst behavior. For the sulfidation tests, a nickel catalyst was used and was sulfidized with H2S. This catalyst had a very low cond. in the reduced state. During sulfidation, the cond. of the catalyst increased by decades. A reaction from nickel to nickel sulfide occurred. This cond. increase by decades during sulfidation had not been expected since both nickel and nickel sulfides behave metallic. Only by assuming a percolation phenomenon that originates from a vol. increase of the nickel contacts when reacting to nickel sulfides, this effect can be explained. This assumption was supported by sulfidation tests with differently nickel loaded catalysts and it was quant. estd. by a general effective media theory. The single pellet sensor device for in operando investigation of sulfidation can be considered as a valuable tool to get further insights into catalysts under reaction conditions.
- 18Anke, M.-L.; Hämmerle, M.; Gerchau, J.; Moos, R.; Jess, A. Radio Frequency-Based In Situ Determination of the Mass Loss of Supported Ionic Liquids. Chem. Eng. Technol. 2017, 40, 1660– 1665, DOI: 10.1002/ceat.20170019018https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXpt1ynsLo%253D&md5=4e0d7055319098496be0e0fae28c3351Radio frequency-based in situ determination of the mass loss of supported ionic liquidsAnke, Marie-Luise; Haemmerle, Martin; Gerchau, Joerg; Moos, Ralf; Jess, AndreasChemical Engineering & Technology (2017), 40 (9), 1660-1665CODEN: CETEER; ISSN:1521-4125. (Wiley-VCH Verlag GmbH & Co. KGaA)For tech. applications of supported ionic liqs. (ILs), the stability of the IL layers both with regard to thermal decompn. and to losses by evapn. is of great importance. An innovative radio frequency-based method is presented to det. the pore filling degree of supported ILs in situ and in a contactless way. As an example, the IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, which was supported on the internal surface of porous silica, was selected. The complex permittivity of the porous solid coated with the IL increases linearly with the IL pore filling degree. Therefore, the evapn. rate of the IL in a fixed bed could be measured in situ in the reactor.
- 19Anke, M.-L.; Hämmerle, M.; Jess, A.; Moos, R. Radio frequency- and impedance-based sensing of ionic liquids supported on porous carriers and their limitations. Sens. Actuators, B 2018, 273, 1564– 1571, DOI: 10.1016/j.snb.2018.07.03619https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtlClu7bN&md5=d2b606a8300f37a90ed467e332b5ac9bRadio frequency- and impedance-based sensing of ionic liquids supported on porous carriers and their limitationsAnke, Marie-Luise; Haemmerle, Martin; Jess, Andreas; Moos, RalfSensors and Actuators, B: Chemical (2018), 273 (), 1564-1571CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)The anal. of the pore filling degree of supported ionic liqs. (ILs) is essential for industrial applications. In this study, two methods to detect the loading of IL supported on solid carriers are presented, a radio frequency-based one and one using impedance spectroscopy. With the radio frequency-based method, the pore filling degree can be detd. contactless and in operando. Some unexpected deviations at non-relevant high pore filling degrees occur. They can be explained by the combination of the results from the radio frequency-based method (at 1.2 GHz) and the impedance spectroscopy (at 1 Hz to 2 MHz). A transition from low polarization losses to high conduction losses occurs with increasing ionic liq. loading of the porous carrier.
- 20Barth, T. Selektivhydrierung von 1,3-Butadien an mit ionischen Fluiden beschichteten heterogenen Katalysatoren. PhD Thesis, Universität Bayreuth, Bayreuth, 2016.There is no corresponding record for this reference.
- 21Jess, A.; Wasserscheid, P. Chemical Technology; John Wiley & Sons: Weinheim, 2013; pp 200– 216.There is no corresponding record for this reference.
- 22Tourillon, G.; Cassuto, A.; Jugnet, Y.; Massardier, J.; Bertolini, J. C. Buta-1,3-diene and but-1-ene chemisorption on Pt(111), Pd(111), Pd(110) and Pd50Cu50(111) as studied by UPS, NEXAFS and HREELS in relation to catalysis. J. Chem. Soc., Faraday Trans. 1996, 92, 4835– 4841, DOI: 10.1039/ft996920483522https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXktVaqug%253D%253D&md5=d0f4a4fb43db8ef244c6e441ac2d759c1,3-Butadiene and 1-butene chemisorption on Pt(111), Pd(111), Pd(110) and Pd50Cu50(111) as studied by UPS, NEXAFS and HREELS in relation to catalysisTourillon, G.; Cassuto, A.; Jugnet, Y.; Massardier, J.; Bertolini, J. C.Journal of the Chemical Society, Faraday Transactions (1996), 92 (23), 4835-4841CODEN: JCFTEV; ISSN:0956-5000. (Royal Society of Chemistry)Chemisorption of both 1,3-butadiene (I) and 1-butene (II) on Pt(111), Pd(111), Pd(110) and Pd50Cu50(111) samples was characterized by near-edge x-ray absorption fine structure (NEXAFS), UPS and high-resoln. electron energy loss spectroscopy (HREELS). I hydrogenation, studied on the same surfaces of Pd and Pd50Cu50, displays a very good selectivity in butenes and a higher activity compared to Pt(111). The Pd activity greatly depends on the surface cryst. orientation and is also influenced by alloying effects. The origin of these effects was sought in differences of chemisorption modes of I and II on the various surfaces: at 95 K, I and II are physisorbed on the different Pd-based single crystals. On Pt(111), I is π-bonded while II is di-σ-bonded. At 300 K, II either dehydrogenates into I on Pd(110) and Pd50Cu50(111) or very probably transforms into butylidyne on Pt(111) and on Pd(111) by analogy to C2H4 adsorbed on these (111) surfaces. I leads to a di-σ mode on Pt(111) and to a di-π one on the different Pd surfaces. The NEXAFS expts. reveal that the π1*-π2* splitting variations [2.0 eV on Pd(111), ∼2.4 eV on Pd(110) and Pd50Cu50(111), ∼2.7 eV on the condensed multilayer] agree with a decrease in the hydrocarbon-substrate interaction in the order Pd(111) > Pd(110) > Pd50Cu50(111). The activity would therefore obey the reverse sequence in agreement with the reactivity results.
- 23Kuhlmann, E.; Himmler, S.; Giebelhaus, H.; Wasserscheid, P. Imidazolium dialkylphosphates-a class of versatile, halogen-free and hydrolytically stable ionic liquids. Green Chem. 2007, 9, 233– 242, DOI: 10.1039/B611974C23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXitlKltLY%253D&md5=89be0321eed9465abd02942e15269568Imidazolium dialkylphosphates-a class of versatile, halogen-free and hydrolytically stable ionic liquidsKuhlmann, Esther; Himmler, Simone; Giebelhaus, Heidi; Wasserscheid, PeterGreen Chemistry (2007), 9 (3), 233-242CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)A systematic and detailed study on the synthesis and the properties of dialkylphosphate ionic liqs. is presented. This class of halogen-free ionic liqs. is easily available in high quality and great variability by direct alkylation of nucleophiles, such as 1-methylimidazole, 1-ethylimidazole, 1-butylimidazole and 1-(2-methoxyethyl)-imidazole with different trialkylphosphates, such as trimethylphosphate, triethylphosphate or tributylphosphate. In general, these dialkylphosphate ionic liqs. display very attractive physicochem. properties with great tech. potential, esp. in low temp. (<200°) applications with H2O present. For this specific application area, the materials described here clearly show superior properties compared with alkylsulfate ionic liqs. due to their obviously much higher hydrolytic stability.
- 24Kohli, P.; Blanchard, G. J. Probing Interfaces and Surface Reactions of Zirconium Phosphate/Phosphonate Multilayers Using 31P NMR Spectrometry. Langmuir 2000, 16, 695– 701, DOI: 10.1021/la990668v24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXmvVCjsrg%253D&md5=32ab4759226f803e0988823e25842922Probing Interfaces and Surface Reactions of Zirconium Phosphate/Phosphonate Multilayers Using 31P NMR SpectrometryKohli, P.; Blanchard, G. J.Langmuir (2000), 16 (2), 695-701CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)NMR 31P magic angle spinning (MAS) methods were used in characterization of zirconium phosphate/phosphonate (ZP) multilayer assemblies grown on SiOx. The reaction of silica with excess POCl3 and treatment with collidine results in both physisorbed and chemisorbed HxPO4(x-3) at the SiOx surface. The 31P NMR spectrum of zirconium phosphate grown from silica shows no residual Cl-contg. species, indicating essentially complete hydrolysis. The phosphate 31P resonances are broadened substantially upon complexation with Zr4+, and T1 data demonstrate the broadening to be inhomogeneous in nature. Data on maleimide-vinyl ether copolymer layers [Langmuir 1999, 15, 1418] confirm that hydrolysis/deprotection by bromotrimethylsilane is efficient in converting phosphoesters to the corresponding phosphorus oxyacid in the synthesis of multilayers. Comparison of polymer multilayers with the relatively more ordered bisphosphonic acid-based multilayers indicates that essentially the same interlayer bonding chem. is seen for both systems, with subtle differences arising as a consequence of the greater available free vol. and more extensive disorder within the polymer.
- 25Chen, L. F.; Ong, C. K.; Neo, C. P.; Varaden, V. V.; Varaden, V. K. Microwave Electronics: Measurements and Materials Characterisation; John Wiley & Sons: West Sussex, 2004; pp 11– 16.There is no corresponding record for this reference.
- 26Slocombe, D.; Porch, A.; Bustarret, E.; Williams, O. A. Microwave properties of nanodiamond particles. Appl. Phys. Lett. 2013, 102, 244102, DOI: 10.1063/1.4809823There is no corresponding record for this reference.
- 27Dietrich, M.; Rauch, D.; Porch, A.; Moos, R. A laboratory test setup for in situ measurements of the dielectric properties of catalyst powder samples under reaction conditions by microwave cavity perturbation: set up and initial tests. Sensors 2014, 14, 16856– 16868, DOI: 10.3390/s14091685627https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitFSmsrs%253D&md5=ca2bcde30becb1e6d49360d1cf65c679A laboratory test setup for in situ measurements of the dielectric properties of catalyst powder samples under reaction conditions by microwave cavity perturbation: set up and initial testsDietrich, Markus; Rauch, Dieter; Porch, Adrian; Moos, RalfSensors (2014), 14 (9), 16856-16868CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)The catalytic behavior of zeolite catalysts for the ammonia-based selective catalytic redn. (SCR) of nitrogen oxides (NOX) depends strongly on the type of zeolite material. An essential precondition for SCR is a previous ammonia gas adsorption that occurs on acidic sites of the zeolite. In order to understand and develop SCR active materials, it is crucial to know the amt. of sorbed ammonia under reaction conditions. To support classical temp.-programmed desorption (TPD) expts., a correlation of the dielec. properties with the catalytic properties and the ammonia sorption under reaction conditions appears promising. In this work, a lab. test setup, which enables direct measurements of the dielec. properties of catalytic powder samples under a defined gas atm. and temp. by microwave cavity perturbation, has been developed. Based on previous investigations and computational simulations, a resonator cavity and a heating system were designed, installed and characterized. The resonator cavity is designed to operate in its TM010 mode at 1.2 GHz. The first measurement of the ammonia loading of an H-ZSM-5 zeolite confirmed the operating performance of the test setup at const. temps. of up to 300 °C. It showed how both real and imaginary parts of the relative complex permittivity are strongly correlated with the mass of stored ammonia.
- 28Dietrich, M.; Rauch, D.; Simon, U.; Porch, A.; Moos, R. Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: Correlation of dielectric properties with ammonia storage. J. Sens. Sens. Syst. 2015, 4, 263– 269, DOI: 10.5194/jsss-4-263-2015There is no corresponding record for this reference.
Supporting Information
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b02421.
Diagram of a TG analysis with the carrier gases nitrogen and helium to distinguish between mass loss due to evaporation or due to thermal decomposition (PDF)
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