Numerical tools are essential for the prediction and evaluation of conventional hydrocarbon reservoir performance. Gas hydrates represent a vast natural resource with a significant energy potential. The numerical codes/tools describing processes involved during the dissociation (induced by several methods) for gas production from hydrates are powerful, but they need validation by comparison to empirical data to instill confidence in their predictions. In this study, we successfully reproduce experimental data of hydrate dissociation using the TOUGH+HYDRATE (T+H) code. Methane (CH4) hydrate growth and dissociation in partially water- and gas-saturated Bentheim sandstone were spatially resolved using Magnetic Resonance Imaging (MRI), which allows the in situ monitoring of saturation and phase transitions. All the CH4 that had been initially converted to gas hydrate was recovered during depressurization. The physical system was reproduced numerically, using both a simplified 2D model and a 3D grid involving complex Voronoi elements. We modeled dissociation using both the equilibrium and the kinetic reaction options in T+H, and we used a range of kinetic parameters for sensitivity analysis and curve fitting. We successfully reproduced the experimental results, which confirmed the empirical data that demonstrated that heat transport was the limiting factor during dissociation. Dissociation was more sensitive to kinetic parameters than anticipated, which indicates that kinetic limitations may be important in short-term core studies and a necessity in such simulations. This is the first time T+H has been used to predict empirical nonmonotonic dissociation behavior, where hydrate dissociation and reformation occurred as parallel events.

Coalbed methane (CBM) reservoirs are notoriously difficult to characterize for the existence of heterogeneity at several length scales. These length scales affect processes of desorption at the grain scale (<nm), diffusion at the micropore scale (nm), gas seepage at the mesopore (μm) and cleat (mm) scales, and production at scales of meters to kilometers. We report pore properties for 14 coal sublayers from three continuous coal seams (numbers 3, 5, and 11) from southeastern Ordos Basin, China. Semi-bright and semi-dull coals are the main coal types. Characterization and analysis across the scales is by X-ray computed topography (CT), mercury intrusion porosimetry (MIP), N2 adsorption/desorption [Brunauer–Emmett–Teller (BET)], and nuclear magnetic resonance (NMR). Proximate and maceral group composition analyses show that the ash yield correlates negatively with the vitrinite content. CT scanning results reflect that strong heterogeneity is developed in the coal between scanned slices at scales of only ∼0.5 mm in thickness, which is coincident with the difference between proximate and maceral groups of each sublayer (∼10 cm scale). A total of 14 samples are classified into three types of mercury intrusion/extrusion curves, indicative of pores with a well-developed adsorption–seepage structure, with poor connection, and alternately those that are adsorption-dominated. The proportion of macro (>1000 nm) and meso (100–1000 nm) pores shows an apparent decrease with an increase in coal burial depth, which is also confirmed by transverse relaxation time (T2) spectra from NMR analyses. The water saturating the macropores is generally removable, while the water in the mesopores is only partially removable, and the abnormal increase in centrifuged T2 amplitudes reflects poor connectivity between pores. Three kinds of N2 adsorption/desorption (BET) curves are recovered and interpreted to be slit-like/plate-like pores, narrow slit-like pores, and ink-bottle (narrow throat and wide body) pores (∼10 nm). Results, using the same source samples throughout, show strong heterogeneity at the microscopic scale for the pore distribution characteristics, even for a single coal seam, and emphasize the utility of using multiple methods of characterization to infer heterogeneity and the textures and connectivity of pore structures.

Methanolysis of an extraction residue (ER) from Xianfeng lignite was carried out to obtain extracts 1–4 (E1–E4). The molecular compositions (MCs) of oxygen-containing species (OCSs) in E1–E4 were characterized using negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). In addition, solid-state 13C nuclear magnetic resonance and X-ray photoelectron spectrometry were used to analyze the carbon types and oxygen functional groups (OFGs) in the ER. The results show that the carbon skeleton structures in the ER are dominated by aliphatic (50.2%) and aromatic (44.9%) carbons. Methylene and methoxy carbons are the most abundant among the aliphatic carbons. Each aromatic cluster contains three rings on average with two substituent groups on each ring. The OFGs in the ER include hydroxy, ether, carbonyl, and carboxyl groups, among which the hydroxy group is the most abundant. The ESI FT-ICR MS analysis shows that the molecular mass distributions of E1–E4 range from 150 to 500 u. The On (n = 1–6) class species are the predominant OCSs in E1–E4, with 0–14 double bond equivalent (DBE) values and 9–34 carbon numbers (CNs). The most abundant On class species in E1–E4 are O2, O2, O2–O3, and O3, respectively. The OCSs in E4 contain low abundances of O1 and O2 class species but relatively high abundances of O4–O6 class species. In addition, the On class species in E4 have narrower ranges of DBE values and CNs than those in E1–E3. A series of acidic species with different DBE values and CNs are assigned to alkanoic acids, alkanedioic acids, alkanetricarboxylic acids, alkylarenols, alkylarenediols, alkylarenetriols, and alkylarenoic acids. With high resolving power and mass accuracy, ESI FT-ICR MS is an effective technique for characterizing MC of the soluble portion from lignites, which will facilitate producing important chemicals from lignites.

The lipopeptide biosurfactant produced by Bacillus subtilis strain W19 was investigated for the potential to maintain additional oil recovery at different dilutions and concentrations and in combination with synthetic chemical surfactant or alkali. The effect of salinity on the biosurfactant performance and the effect of biosurfactant on permeability reduction were also studied, at reservoir conditions. Core-flooding experiments were conducted to quantify the biosurfactant dosage for optimized enhanced oil recovery. Berea sandstone cores with respective average gas permeability and porosity of 223 mD and 21.5%, crude oil of American Petroleum Institute (API) gravity of 32°, and formation brine with salinities ranging from 7 to 9% were used. Biosurfactant reduced the interfacial tension (IFT) between the aqueous phase and crude oil from 20.9 to 1.8 mN/m. In core flood tests with cell-free biosurfactant broth at different dilutions (undiluted, 2.5×, 5×, 10×, and 20× diluted) and using crude biosurfactant powder (1 and 0.4 g/L), we observed additional 15 and 13% oil recovery over residual water-flood oil saturation, respectively. These results confirmed that a minimal biosurfactant concentration required for effective oil recovery was 0.4–0.5 g/L. Because biosurfactant broth is more economical then extracting biosurfactant, we have used it for further experiments. Salinity effect studies on oil recovery showed that this biosurfactant can maintain an additional recovery of 20% even at up to 20% (w/v) salinity. A mixture of 10× diluted biosurfactant with chemical surfactant to the ratio of “75:25”, respectively, resulted in 28% additional recovery, which was better than using either alone. Mixing of biosurfactant with alkaline (Na2CO3 at 0.5 and 1.0% concentrations) resulted in further reduction of IFT by a factor of 10, but no further improvement of oil recovery was observed. Diluted biosurfactant also showed very minimal reduction in permeability of sandstone cores. This study showed that the biosurfactant would produce an appreciable amount of additional oil after water-flooded residual oil at a low concentration, without much formation damage, and its performance can be improved even further by mixing it with chemical surfactants.

The oxidation characteristics of chars from low-temperature pyrolysis of two lignite coals have been systematically investigated using a dual fixed-bed quartz reactor and a thermogravimetric analyzer (TGA). During oxidation experiments, the temperature profiles of coal and char samples were recorded and CO2 and CO gases evolved were analyzed using gas chromatography. The physical and chemical structures of coals and chars were analyzed using Brunauer–Emmett–Teller (BET) adsorption isotherms and Fourier transform infrared spectroscopy (FTIR). During oxidation, the temperature of the coal sample may increase noticeably, exceeding the crossing point temperature (CPT). Chars prepared at 400 °C showed the lowest CPT, indicating the highest oxidation reactivity compared to that of parent coals and chars prepared at other temperatures. During oxidation, gaseous products are released, implying that oxygen-containing functional groups and solid oxygenated complexes decomposed and the yields increased with increasing the oxidation temperature. The amount of CO2 generation was proportional to that of CO with the molar ratio of CO2/CO at around 4.15 under the present experimental conditions. During non-isothermal oxidation, the concentration of OH and other oxygen-containing functional groups increased with increasing the oxidation temperature for char samples but decreased in the case of oxidized coal. During isothermal oxidation, the concentration of oxygen functional groups in coal decreased with increasing the oxidation temperature above 250 °C. Pre-oxidation of chars decreased their combustion reactivity measured on the TGA.

This paper proposes an environment-friendly method to load ferrous ion (Fe2+) to lignite with water, iron metal and carbon dioxide (CO2) but without mineral acids or iron salts containing potentially harmful components. Iron metal was dissolved into 25 °C water that had been saturated with CO2 at its gaseous pressure of 4.0 MPa. The solubility of ferrous iron was 1 070 mg-Fe/L-water. This solubility was much higher than that predicted from the solubility product (Ksp) of FeCO3 with an assumption that Fe2+ represented the dissolved ferrous iron. Rather, another assumption of coexistence of Fe2+, FeHCO3+, and Fe(HCO3)2 reasonably explained the measured solubility of ferrous iron. The dissolved ferrous iron was loaded to a Victorian lignite by ion exchange. The iron-loaded lignites with different iron concentrations (0.3–6.7 wt %-dry-lignite) were subjected to a sequence of pyrolysis and steam gasification to produce synthesis gas in a thermogravimetric analyzer. The gasification was catalyzed by the loaded iron regardless of its concentration, while the quickest at 1.0 wt % where dispersion of iron-derived catalytic species in the char matrix was maintained until its complete gasification with steam.

The upper Triassic Yanchang shale in Southeast Ordos Basin (SOB) is a main potential source rock for conventional petroleum fields and has been recently recognized as an important unconventional reservoir. Here, we report on the hydrocarbon potential of this lacustrine shale using bulk and quantitative pyrolysis techniques. The rock samples were taken from the Chang7 and Chang9 intervals of upper Triassic-aged cores. The analytical program included total organic carbon (TOC), Rock-Eval, pyrolysis gas chromatography (Py–GC), source rock analyzer (SRA), and microscale sealed vessel (MSSV) pyrolysis. Phase kinetic modeling was also employed on the basis of these data sets. The results were used to determine the petroleum-type organofacies, bulk hydrocarbon composition during maturation, bulk and compositional kinetics, and phase behavior of fluids generated in the Yanchang shales. The shales proved to contain type II2 kerogen with organic matter in high abundance and generate paraffinic–naphthenic–aromatic (PNA) low wax oils when mature, whereas samples with increasing maturity show a potential for gas condensate generation. Bulk kinetic parameters of the immature Yanchang shale reveal a relatively broad distribution of activation energies and indicate lower stabilities than marine Cambrian type II shale in south China. Hydrocarbon generation could be characterized by a frequency factor A = 2.20 × 1012 S–1 and a main activation energy at 50 kcal/mol. Extrapolation to the geological heating rate of 1.0 °C/Ma in SOB, the onset (transformation ratio = 10%) and peak generation temperatures were 115 and 124 °C, respectively. Compositional kinetic modeling predicts that the generated gas fraction mainly consists of C1, C2, and C3, while the liquid phase is predominated by compound groups of C7–15 and C16–25. Furthermore, the gas/oil ratio (GOR) varies between 83.6 Sm3/Sm3 (97.1 m3/t) and 168.2 Sm3/Sm3 (195.3 m3/t). The saturation pressure (Psat) and formation volume factor (Bo) display a linear correlation as a function of the transformation ratio (TR). The property of the generated hydrocarbons is in agreement with naturally occurring petroleum fluids. Using the pressure–temperature (P–T) envelope defined from these experiments, only a single liquid phase (black oil) is predicted at different TRs (10–70%). This research provides the first case study with respect to phase kinetics description of Yanchang shale oil and shale gas in the study area.

Efficient utilization of the low-rank coal has been a headachy problem, especially when firing the high alkali-containing coal in a typical pulverized fuel boiler, where severe slagging and fouling originating from the alkali metal vapors may occur. The additives injection technology has been proved to be a promising method in combating these problems. In this study, the alkali capture mechanism of kaolin was investigated by burning a kind of high-sodium lignite in a laboratory-scale drop tube furnace. The effects of kaolin content, reaction temperature, and particle sizes of both kaolin and fuel on the sodium capture efficiency of kaolin were also investigated. It was found that kaolin could chemically adsorb NaCl, the primary sodium species proved in the flue gas, to form high-melting sodium aluminosilicates such as nepheline and albite, and the nepheline-forming reaction dominated the sorption mechanism. More kaolin addition led to more sodium fixed into the ash. However, the promotion was not that pronounced in high kaolin dosages. The sodium capture efficiency decreased as temperature was increased or larger kaolin particles were injected. Effect of the coal size on the sodium capture efficiency could be neglected in the tested size range. The sodium retention with 6 wt % kaolin addition of the fuel at 1200 °C could attain 70% of the total sodium in the combusted coal, which can considerably reduce the ash-related problems and facilitate the safe firing of high alkali coal in boilers.

The formation of sediments is a serious instability problem in the storage of fossil fuels. Reactions that lead to sediment formation can be linked to the oxidation of certain fuel components that contain oxygen, nitrogen, or sulfur. To study the oxidation reactions that occur during aging of fuels, we doped a model fuel with several representatives of such compound types. The compounds used were 2,6-dimethylphenol, 2-naphthol, 2,5-dimethylpyrrole, 2-methylindole, dibenzothiophene, and pentamethylene sulfide. After an artificial aging of the samples according to the DGMK-714 protocol, the formed sediments were analyzed by electrospray ionization mass spectrometry (Orbitrap, ESI-MS), elemental analysis, infrared measurements, and mass analysis. Mass spectrometry indicated monomeric and dimeric oxidation products with two to nine oxygen atoms as well as products with different hydrocarbon structures (different C/H ratios) from 2,6-dimethylphenol. 2-Naphthol led to oligomers consisting of up to six monomer units and showing different degrees of oxidation. The first ever recorded cross-coupling between 2,6-dimethylphenol and 2-methylindole and between 2-naphthol and 2,5-dimethylpyrrole is also shown. In general, the tested nitrogen compounds and especially the phenols tended to form oxidized oligomers, whereas the sulfur compounds led to sulfoxides and sulfones.

In order to formulate mitigation strategies before the onset of oil pipeline and topside deposition problems caused by so-called calcium naphthenates or chelates of “ARN” acids, it is necessary to develop an analytical technique suitable for the quantification of the constituent C80 tetraacids in small samples (∼1 g) of crude oils at low parts per million (ppm) concentrations. Here we report a method for the (semi)quantitative determination of tetraacids in crude oils using a relevant C80 8-ring acid as an internal standard. After addition of the internal standard, an “acid” fraction is isolated from the oil using sequential ion exchange solid-phase extraction (SPE) and the acids converted to their per-methylated esters before further SPE refinement to obtain a “tetraacid” fraction. Tetraacids are analyzed as the ammoniated adducts of their per-methyl esters using liquid chromatography coupled with electrospray ionization-mass spectrometry. This method has a limit of quantitation (LOQ) of approximately 0.1 ppm for individual tetraacids in crude oils. As an example, the use of this method for the determination of the individual and total tetraacid contents of five crude oils is shown.

The subject of the presented work was the development of a two-dimensional GC×GC–time-of-flight mass spectrometric method (GC×GC-TOFMS) for the complete group-type quantification of petroleum middle distillates. The development of this method was possible due to the inherent features of GC×GC-TOFMS, namely the structured arrangement of compound groups and the mass fragmentation pattern, which provide the possibility of using Visual Basic Scripts as an analytical tool and thereby the classification of several thousand different compounds. The analysis method was focused on common petroleum based fuels from light to heavier middle distillation fractions. For the implementation of an absolute quantification method, a set of standard substances representing the main substance classes and carbon numbers within middle distillates and well-separated and recognizable internal standards were thoroughly chosen in order to obtain individual response factors and group specific response curves. The results of the qualitative and quantitative analysis were compared to well-established standard methods used in the petrochemical industry. The quantification of aromatic hydrocarbons was compared to EN 12916, a high performance liquid chromatography (HPLC) method that provides a rough separation between mono-, di-, and higher aromatics. Further, the quantification of the fatty acid methyl ester (FAME) content in diesel fuel was compared to EN 14078 and the distribution of single FAMEs was compared to EN 14103. It could be stated that an absolute quantification as the here presented method has not been reported before and the results were in good agreement with the reference methods. Furthermore, the here presented GC×GC-TOFMS quantification method is able to itemize according substance classes and carbon number. The detection limit of the method allows accurate and sensitive quantification for different limiting values of middle distillates with a single method.

The devolatilization process has important influence on the formation of PM10 (particulate matter with an aerodynamic diameter of ≤10.0 μm) in oxy-fuel combustion of pulverized coal but has been explored little. A bituminous coal was devolatilized in either CO2 or N2 at 1573 K on a drop-tube furnace (DTF) to produce CO2-char and N2-char. Coal and its char samples were burned at 1573 K and in 29 vol % O2/71 vol % CO2. PM10 was collected and segregated into 13 size fractions, which were subjected to subsequent analysis. The results show that the particle mass size distributions of PM10 from coal and chars have similar peak and trough sizes, suggesting that the devolatilization process has insignificant influence on the major pathways of PM10 formation. Three particle modes can be identified, i.e., ultrafine mode (<0.5 μm, PM0.5), central mode (0.5–2.5 μm, PM0.5–2.5), and coarse mode (2.5–10 μm, PM2.5–10). Coal combustion produces more PM0.5 and PM0.5–2.5 than char combustion, suggesting that the devolatilization process has important influence on the production of PM0.5 and PM0.5–2.5. In contrast, the PM2.5–10 yield is insignificantly affected by the devolatilization process under the investigated conditions. In addition, the combustion of CO2-char generates more PM0.5 and PM0.5–2.5 than that of N2-char, indicating that the devolatilization in CO2 favors the formation of PM0.5 and PM0.5–2.5.

We have recently proposed a degradative solvent extraction method to upgrade and fractionate various types of low-rank coals by a nonpolar solvent at temperatures below 350 °C. The main products obtained are solvent-soluble fractions (extracts) and an insoluble fraction, which we call “upgraded coal (UC)”. The UC samples were prepared from eight low-rank coals and one bituminous coal in this work. It was found that the gasification reactivities of the UC chars prepared from seven coals of the eight low-rank coals were larger than those of the raw coal chars. The CO2 gasification rates of the UC chars prepared from an Australian brown coal, Loy Yang (LY/UC), and an Australian bituminous coal, Gregory (GR/UC), were surprisingly larger than the gasification rates of the corresponding raw coal chars by 2.4–1.9 times. The mechanism of gasification reactivity enhancement was examined from the viewpoints of the catalytic effect of coal inherent minerals, pore surface area, and carbon structure of the chars. The reactivity enhancement of GR/UC was well-explained by the increase of the pore surface area through the degradative solvent extraction. On the other hand, neither the catalytic effect of minerals nor the pore surface area was responsible for the gasification reactivity enhancement for LY/UC. X-ray diffraction (XRD) measurement and elemental analysis showed that LY/UC had a more disordered carbon structure than raw coal char. The reactive surface area estimated by the transient gasification method was judged to be a good index to explain the significant gasification enhancement for LY/UC. Although more detailed examination is required to elucidate the mechanism of the gasification enhancement, the proposed degradative solvent extraction method of low-rank coal can be one of the ways to enhance the gasification reactivity of coal char without using a catalyst.

A group-type analysis of hydrocarbons in a complex jet fuel may be more useful than attempting to analyze every component because the latter inevitably leaves a large portion of the fuel unidentified. While it may be difficult to accurately determine the identity of a particular compound, that compound can often be classified as belonging to a group or compound class because of its chromatographic retention and mass spectral properties. Compound class quantitation is often capable of relating compositional information to fuel properties. Two-dimensional gas chromatography (GC × GC) is a technique capable of providing this group-type separation and quantitation in jet fuels. This technique was used to examine a large set of fuels (Jet A, Jet A-1, JP-5, and JP-8, primarily) from petroleum sources and non-petroleum alternative sources, such as synthetic paraffinic kerosene (SPK). By comparing results from GC × GC analysis to established techniques and model compound studies, we have found that the accuracy of GC × GC for group-type analysis is excellent. Quantitation of group types for alternative fuel sources were also investigated and compared to conventional techniques. The possible uses and applications of group-type measurements using GC × GC for fuels and fuel-related materials are discussed.

The physical properties of bitumen (i.e., asphalt) are a topic of consistent interest in the fields of oil, gas, and mining. In this study, the relationship between bitumen viscosity and the rotation of asphaltene clusters was empirically explored via broadband dielectric spectroscopy (BDS). Cluster size was found to be independent of the concentration, and BDS was found to be a reliable means to predict viscosity in neat bitumen and concentrated solutions. Because of the simplicity and portability of modern impedance analyzers, this technique offers a unique method for estimating a wide range of oil viscosities in the field (from <101 to >105 cP) and even offers the possibility of in situ oil viscosity monitoring in pipelines or oil-lubricated mechanical systems.

Hydrophobically modified methacryl- and acrylamide polymers are well-known kinetic hydrate inhibitors (KHIs). Polymers of N-isopropylmethacrylamide (IPMAM) are now commercially available. However, both polyIPMAM and N-isopropylacrylamide homopolymer (polyIPAM) have low cloud and deposition points, making it difficult to use them in the field because of precipitation problems. Comonomers that are more hydrophilic can be copolymerized with IPMAM or IPAM to raise the cloud point. In this work, we have synthesized and investigated a series of new copolymers of IPAM and a new dimethylhydrazidoacrylamide monomer (DMHAM) as KHIs for the first time using high-pressure gas hydrate rocker rig equipment. The novel polymers have high cloud points in deionized water and also in brine solutions compared to polyIPAM. A 1:2 copolymer of DMHAM/IPAM gave the highest KHI performance for this class of copolymer with a cloud point at 58 °C in deionized water. A 1:1 copolymer gave only a small reduction in performance but has a cloud point of 83 °C in 3.6% NaCl and no cloud point in deionized water. Tests were carried out using high-pressure slow constant cooling rocking cell experiments with a structure-II-forming natural gas mixture at approximately 80 bar.

Six coals with carbon contents ranging from 69 to 80 wt % dry ash-free (daf) were rapidly pyrolyzed at 1300 °C under a stream of high purity He in a free fall-type graphite reactor incorporating a graphite filter to control the residence time of coal particles. In this manner, the effects of both residence time and inherent mineral contents on N2 formation from char-N following devolatilization were examined. At a residence time of zero, 20–30% of the coal-N was released as volatile-N species, such as tar-N, HCN and NH3, while <15% was transitioned to N2 and the remainder (60–80%) was retained in the char. When the residence time was increased to 120 s, the yields of tar-N, HCN and NH3 were almost unchanged, irrespective of the coal type, although the N2 yield increased and the char-N decreased with increasing residence times, with the changes in yields of both species being roughly equal. When an Indonesian char sample already devolatilized at 1000 °C was pyrolyzed again by applying a slow heating rate of 10 °C/min to 1300 °C, the nitrogen in the 1000 °C char was converted almost exclusively to N2. These observations demonstrate that char-N and/or its precursors are the main source of the N2 in pyrolysis products. The enhancement in N2 yield observed on increasing the residence time from zero to 120 s increased with increasing inherent Ca or Fe contents in the range of ≤0.3 wt % (dry), although the data were somewhat scattered. Thus, small amounts of naturally occurring Ca and Fe appear to promote N2 formation from the devolatilized char-N. It appears likely that Ca- or Fe-containing minerals in the coal are partly transformed into CaO or α-Fe, respectively, under the present rapid pyrolysis conditions, both of which enhance the conversion of char-N to N2 as well as the transition of amorphous carbon to crystallized carbon with turbostratic structures. A linear relationship was observed between the N2 yield and the proportion of crystallized carbon formed, which may indicate that the yield of one may be predicted from the yield of the other. The catalysis of N2 formation from char-N without volatile materials through the presence of mineral-derived CaO or α-Fe is discussed herein in terms of solid–solid reactions of these metal particles with heterocyclic nitrogen species in the char.

The pore size distribution, pore shape and connectivity, and fractal characteristics are investigated to determine the pore characteristics of three different samples of middle–high rank coal. Pores of more than and less than 10 nm were measured using mercury intrusion porosimetry (MIP) and gas adsorption, respectively. The pore size distribution was verified with the initial methane diffusion rate and CH4 desorption. Fractal dimensions of seepage pores and adsorption pores were counted using the results from MIP and gas adsorption, respectively. First, the results show that micropores and transition pores occupy the most volume and specific surface area. Micropores and transition pores, as well as porosity, gradually increase as coal rank increases. Second, the fractal dimensions of seepage pores and adsorption pores gradually increase with increasing coal rank, which shows that coalification makes pore structure more complex and pore surface rougher. Additionally, the fractal dimensions of bigger pores are greater than those of smaller pores, implying that the surface and structure of bigger pores is rougher and more complex than those of smaller pores, respectively. Finally, the connectivity of coal has a close relationship with macropores rather than coal rank.

The results of numerical studies of heavy oil production by radio frequency–electromagnetic heating (RF–EM) from hydraulically fractured low-permeability reservoirs are presented. The fluid flow to a single vertical high-conductivity fracture is considered assuming that electrical and thermal properties of the reservoir rock and fluid-saturated fracture are the same. Comparative analysis is performed for the cases of heavy oil recovery by RF–EM radiation with hydraulic fracturing and “cold” production. Modeling of the combined multi-stage method and economic analysis for different RF–EM generator powers, differential pressure between the well and formation, and the fracture conductivity showed that the method is most effective for wells with “short” and low-conductivity hydraulic fractures.

Membrane absorption is a novel method for acid gas removal compared to conventional separation techniques. The current study presents the simulation results using a computational fluid dynamics (CFD) method for biogas purification. A comprehensive two-dimensional (2D) mass-transfer model was developed and solved in a hollow fiber membrane contactor (HFMC) under a non-wetted condition. H2O, triethanolamine (TEA), diethanolamine (DEA), monoethamolamine (MEA), and potassium argininate (PA) were used as the absorbent liquids. The effects of gas–liquid parameters and membrane characteristics on the CO2 removal efficiency and absorption flux and CH4 recovery were systematically examined and evaluated. The comparisons between model predictions and experimental data with various gas–liquid parameters were in good agreement. An increase of gas velocity and CO2 content caused an increase of CO2 flux and a decrease of CO2 removal efficiency and CH4 recovery; however, an increase of absorbent velocity and concentration caused an increase in the above three values. In addition, a smaller fiber inner diameter and membrane thickness and a longer module were good for the biogas upgrading process. It should be noted that the highest CO2 flux coincided with the original module dimensions. The simulation predictions also showed that PA provided better membrane module performance than other absorbents. The order for CO2 absorption efficiency and CH4 recovery was PA > MEA > DEA > TEA > H2O. Overall, the developed model provides the guidelines for selecting the optimum module properties and fluid conditions. The membrane gas absorption technique has shown great potential in biogas upgrading.

This research investigated the effect of the furnace temperature on ash deposition behavior using digital image techniques and combined chemical equilibrium calculations with the improved model to calculate ash deposit viscosities at different temperatures. Three different furnace temperatures were selected: 1473, 1523, and 1573 K. In addition, the chemical components of the deposit samples were analyzed by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectrometry (EDX). The results revealed that the growth process of the ash deposit at 1573 K was significantly different from those at 1523 and 1473 K. Meanwhile, it revealed that a low temperature can facilitate an increase in deposit thickness. The chemical equilibrium calculations indicated that the main crystalline phases in the three deposits were anorthite and hematite. The calculated results for ash deposit viscosity revealed that the viscosity of ash deposits decreased with increasing the temperature.

A comprehensive two-dimensional multiphase model was developed to describe the gasification of three large available Portuguese biomasses in a pilot scale fluidized bed gasifier within the computational fluid dynamics Fluent framework. An Eulerian–Eulerian approach was implemented to handle both the gas and the dispersed phases. The kinetic theory of granular flows was used to evaluate the constitutive properties of the dispersed phase, and the gas-phase behavior was simulated employing the k–ε turbulent model. Devolatilization phenomenon was also modeled. Results from the numerical model were later compared with experimental data also gathered for the three Portuguese biomasses. The simulated syngas compositions are in good agreement with the experimental results with maximum deviations of 20% (considering all simulations and biomasses). The effect of the gasification temperature and steam-to-biomass ratio on the syngas composition was evaluated as well as the cold gas efficiency, H2/CO ratio, CH4/H2 ratio, and carbon conversion. From this analysis, it was possible to define which biomass has the greater potential to be used concerning the selected application. Among the three biomasses, it was concluded that coffee husks and vine-pruning residues show better H2/CO ratios, while the higher CH4/H2 ratios are obtained by using the forest residues. The highest cold gas efficiencies were obtained by using the vine-pruning residues. These data are crucial to describe scenarios concerning the potential use of biomass as a source of energy in Portugal.

Enhancing the contact or interaction between cellulose and solid catalyst is a significant aspect in its efficient catalytic conversion. Herein, mixed ball milling of cellulose and solid catalyst was presented to achieve this goal, and the promotion effect was measured by hydrolytic hydrogenation of cellulose to sugar alcohols (the platform compounds for biogasoline) with solid acid and commercial 5 wt % Ru/C in water. The effects of ball-milling modes, time, and reaction parameters were studied. The properties of cellulose and solid acid catalyst before and after treatment were also analyzed. The yield of sugar alcohols reached 90.3% at 463 K with amorphous zirconium phosphate and Ru/C (mixed ball-milling time of 2 h). This high yield of sugar alcohols achieved in the mixed ball-milling time of 2 h was 12 times faster than that by the single ball milling of 24 h under the same reaction conditions. It is ascribed to the enhanced contact between cellulose and catalyst, resulting in promoting cellulose depolymerization. The high concentration of sugar alcohols up to 67 mg/mL was obtained by augmenting the mass ratio of cellulose/catalyst.

The fuel properties of fast pyrolysis bio-oils differ significantly from those of fossil fuels. As transportation fuel, bio-oil is not suitable without upgrading because of its relatively low energy content, high water content, acidity, and poor storage stability. Upgrading of bio-oil has usually been done by treating the whole oil in a reactor. The problem with this treatment is that pyrolysis oil is a mixture of different compound groups, which all need different conditions and catalysts to react in a desirable way. Therefore, an efficient fractionation of bio-oil before upgrading may be a more efficient way of producing liquid fuels than treating the whole oil. In this work, the target was to compare two industrially relevant fractionation concepts. In the first concept, most of the water was removed during liquid recovery by adjusting the scrubber temperature. When the scrubber temperature was increased from 36 to 66 °C, the water content in the bio-oil decreased from 24 to 7 wt %. In the second concept, fast pyrolysis was carried out with wet feedstock. This would reduce the drying cost in the plant. By this means, a spontaneous phase separation was generated after liquid condensation. In the experiments, the moisture content of the raw material was increased up to 25 wt %, but even with this moisture content, the oily bottom phase still contained 22 wt % water-soluble compounds. However, if the target is to produce transportation fuels from bio-oil, fractionation by phase separation is a better concept for dividing the bio-oil into different compound groups.

The microalgae Phaeodactylum tricornutum was processed by hydrothermal liquefaction in order to assess the influence of reaction temperature and reaction time on the product and elemental distribution. The experiments were carried out at different reaction times (5 and 15 min) and over a wide range of temperatures (275–420 °C) using a batch reactor system. All fractions were quantified and analyzed in terms of specific elemental concentrations. The highest bio-oil yield (39%) was obtained at 350 °C when using a reaction time of 15 min. Under these conditions, 82% of the algal calorific value was recovered in the bio-oil fraction. The higher heating value of the bio-oil increased with reaction temperature and reaction time. The elemental analysis was used to map the distribution of elements in the obtained fractions with increasing temperature. Generally, most of the potassium, sodium, nitrogen, phosphorus, and sulfur were recovered in the aqueous fraction. The solid residue was found to primarily consist of a calcium phosphate compound.

Pretreatment of corncobs using torrefaction was performed in a tubular reactor with varying reaction temperature (210, 240, 270, or 300 °C) and residence time (20, 40, or 60 min). The torrefied corncobs were subsequently catalytically fast pyrolyzed over nanosized HZSM-5 in a semibatch pyroprobe reactor. The torrefied corncobs were characterized by elemental analysis, thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (FTIR), and FTIR. The aromatic production was online analyzed by gas chromatography mass spectroscopy. The effect of torrefaction severity on product distribution and aromatic selectivity from catalytic fast pyrolysis of torrefied corncobs was investigated. The experimental results show that torrefaction can serve as an effective thermal pretreatment for improving the selectivity of BTX (benzene, toluene, and xylenes). Light and mild torrefaction (torrefaction at 210 and 240 °C) has little impact on the aromatic yield. However, severe torrefaction (torrefaction at 270 or 300 °C) can lead to the sharp increase of coke yield and reduction of aromatic yield. The results could be explained by the serious cross-linking and charring of corncob under severe torrefaction conditions. The optimal torrefaction condition is 210–240 °C with residence time of 40 min.

An entrained-flow flat-flame burner reactor was used to measure apparent CO2 gasification rates of near-spherical biomass chars of poplar sawdust, switchgrass, and corn stover using particle residence times <270 ms at total pressures of 10 and 15 atm. The gas temperature and bulk CO2 partial pressure ranges in these gasification experiments were 1258–1891 K and 6.1–13.5 atm, respectively. A new method was developed to produce near-spherical particles from nonspherical biomass chars. The apparent CO2 gasification rates for the three biomass chars with mean diameters near 100 μm were fit to a global first-order model, and the optimal kinetic parameters are reported. The measured gasification rate of poplar sawdust was about 3.9 times faster than that of switchgrass char, but only about 20% faster than that of the corn stover char.

HCl emission characteristics during the combustion of eucalyptus bark were carried out at various temperatures. The influence of the various additives on the HCl emission was investigated by the experiment, FactSage, and X-ray diffraction. The results showed that the HCl emission could be divided into two stages at 500 °C. The totality of the HCl emission at 500 °C was an order of magnitude higher than that at 600 °C. The peak value of the HCl emission curves increased initially and then decreased with the temperature between 500 and 900 °C, while the totality of the HCl emission decreased with the temperature. Calcium oxide and aluminum oxide could reduce the HCl emission during the combustion process. However, the removal effect of the HCl emission decreased with increasing the temperature. Unlike calcium oxide and aluminum oxide, the addition of kaolin to the bark could increase the HCl emission. The deviation between the simulation and practical results increased at a low temperature. Moreover, all of the additives could retain potassium in the residue of the eucalyptus bark, but the effect of kaolin to retain potassium was more significant than the effect of the other additives.

The esterification of lauric and stearic acids, tall oil fatty acid, and a commercial oleic acid with methanol was investigated using an acid-activated standard montmorillonite (AASM) as a catalyst. Reaction variables such as the methanol:fatty acid molar ratio, catalyst content, and temperature were evaluated. Comparative reactions were performed with K10 catalyst, and similar or even better results were obtained with AASM, indicating that this could be employed as a suitable Lewis/Brönsted esterification catalyst. The experimental results obtained for the esterification of lauric acid with methanol were compared to a thermodynamic model. For this purpose, the UNIFAC model was used for the activity coefficient calculation for components in the nonideal mixture. This model has shown that the catalytic system was able to drive the reaction to equilibrium within 2 h, and this was confirmed by comparing the experimental results with thermodynamic predictions.

Large amounts of thermal energy are required for different unit operations in the pulp and paper industry. Typically, this energy is distributed by means of steam. In this study, introduction of in-situ-generated syngas as an energy carrier in parallel to the predominant steam has been investigated. The examined systems use dual fluidized-bed gasification integrated with a solid fuel boiler of a paper mill together with impingement drying in combination with cylinder drying, a concept enabling higher specific drying rates. The studied systems exhibit reduced overall energy use when compared to the present situation with conventional steam-heated cylinder drying. Cold tar cleaning by condensation/absorption and firing of the syngas in a gas turbine followed by utilization of the exhaust gases for drying are interesting options because this results in reduced biomass consumption with maintained power production.

Biodiesel (rapeseed oil methyl ester) was aged in a Rancimat device at a temperature of 110 °C and an air flow of 10 L/h. Time-resolved analyses applying gas chromatography–flame ionization detection, gas chromatography–mass spectrometry, and ion-exchange chromatography on the formation of aging products were performed. Formic and acetic acid, fatty acids with chain lengths from 5 to 18 carbon atoms, fatty acid methyl esters, and epoxides were quantified. After 12 h of aging, the concentrations of formic and acetic acid were 5600 ± 80 and 1360 ± 80 mg/kg, respectively. Fatty acid concentrations were in the range of <18–4200 mg/kg after 18 h of aging. Linoleic acid methyl ester and linolenic acid methyl ester (19 and 9.1 mass % of the non-aged fuel) were shown to be fully decomposed after 24 and 18 h of aging, respectively. After 51 h of aging, the concentration of oleic acid methyl ester (63 mass % of the non-aged fuel) decreased to 2.2 mass % and trans-epoxy stearic acid methyl ester and cis-epoxy stearic acid methyl ester reached concetrations of 5.9 and 0.7 mass %, respectively. The fuel composition shows only minor changes in early stages of aging, and a strong timely correlation of the formation of aging products with the end of the induction period of fuel was observed.

The properties of biomass directly result in the quality of bio-oil. Torrefaction pretreatment is an alternative and promising approach for biomass updating to produce high-quality bio-oil. The effects of torrefaction on the pyrolysis of rice husk were investigated using thermogravimetry–Fourier transform infrared spectroscopy (TG-FTIR), a pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and a fast pyrolysis device. The results show that with increasing torrefaction temperature, the weight loss decreases and the shoulder peaks of torrefied rice husk in DTG curves fade away. The pyrolysis characteristics and kinetics analysis of torrefied rice husk at 290 °C are unique. Three-dimensional FTIR analysis of the evolved gases clearly shows the generation properties of individual volatile components. Fast pyrolysis of torrefied rice husk produces improved bio-oil low moisture content and high heat value. Py-GC/MS analysis shows that the acidic content does not increase, while the content of many highly valued products (e.g., levoglucose) increases greatly.

The utilization of vegetable oils as a source of renewable fuels has attracted much attention. However, the high viscosity of vegetable oils limits their long-term application. The microemulsion technique of vegetable oils has the advantages of viscosity reduction and environment-friendly properties. In this study, the phase behavior of the microemulsion and the solubilization mechanism of water and castor oil in diesel were researched to evaluate the solubilization capacity of water and castor oil in diesel under given conditions. The proper concentration of rhamnolipid (RL) was 50 g/L. N-octanol was certified as an ideal co-surfactant with the optimal co-surfactant/surfactant (C/S) mass ratio (w/w) of 0.60. The optimum castor oil/diesel (V/D) volume ratio (v/v) was 0.18. Moreover, fuel properties of water-containing castor oil/diesel (WCD) microemulsion were identified, including density, dynamic viscosity, cloud point, pour point, water content, corrosivity, heating value, and elemental composition. The thermal and storage stability of WCD microemulsion were also conducted. Compared with castor oil, WCD microemulsion has lower viscosity, which presents similar fuel characteristics as diesel.

This study reports the hydrodeoxygenation (HDO) of stearic acid (SA) into paraffinic biofuel with synthesized palladium-oxalate zeolite supported catalyst (PdOx/Zeol). The PdOx/Zeol was synthesized via the functionalization of dihydrogen tetrachloropalladate (II) with aqueous oxalic acid (OxA) to form the polynuclear palladium(II) oxalate (PdOx), which was supported on zeolite. The SEM and XRD characterization results showed that the zeolite support is highly crystalline but loss some degree of crystallinity in the PdOx/Zeol sample after PdOx incorporation. The activity of the PdOx/Zeol tested on the HDO of SA showed that temperature, pressure, gas flow rate, and PdOx/Zeol loading have significant effects on the HDO process, and their best observed conditions were 360 °C, 20 bar, 100 mL/min, and 25 mg, respectively to achieve 92% biofuel production from 35 g SA. The biofuel product distribution showed 71% n-C18H38, 18% iso-C18H38, and 3% C17H36. The presence of iso-C18H38, which is an excellent biofuel value-added-component due to its low freezing point, was ascribed to the functionalization of Pd with OxA, which increases PdOx/Zeol acidity. The results showed that PdOx/Zeol is a prospective catalyst toward further research and commercialization of HDO process of SA.

Fixed-bed pyrolysis of Norway spruce wood previously subjected to torrefaction at temperatures between 533 and 583 K and retention times between 8 and 25 min was studied. Although the thermal pretreatment always results in an increased production of char at the expense of volatile products, appropriate torrefaction conditions give rise to maximum percentages of anhydrosugars, guaiacols possessing a carbonyl group, and phenols in the liquid fraction. Other carbohydrates (e.g., acetic acid, formic acid, hydroxyacetaldehyde, hydroxypropanone, furfural, and furfuryl alcohol) and the large majority of guaiacols show continuously decreasing values. The percentages of carbon monoxide and carbon dioxide in the gas product remain approximately the same, but that of methane slightly increases. The pyrolysis temperatures of torrefied wood are lower than those of the raw material, mainly because of the partial or complete absence of the exothermic contribution associated with extractives and hemicellulose degradation.

Biomass gasification produces a wide range of species, from permanent gases to condensable hydrocarbons, with different composition and boiling points. This complicates the mass balance of the system, as multiple techniques are needed to quantify the various components of the produced raw gas. In this study, a high-temperature reactor for thermal conversion of raw gas at 1700 °C was developed to generate a gas stream that consisted primarily of CO, CO2, H2, and H2O. The reactor was experimentally evaluated and subsequently used for measurements of the raw gas from the Chalmers 2-4–MW dual fluidized bed gasifier. The gas stream that exits the reactor is analyzed to obtain the total elemental flows of C, H, O, and N, which facilitate determinations of the fuel conversion and oxygen transport in a dual fluidized bed reactor. The proposed system was operated in parallel with a gas-cleaning system, to determine the yield of condensable species, including tar and GC-undetectable species. A simplified approach is proposed for quantifying the average energy content of the condensable species, thereby allowing the wet raw gas efficiency and lower heating value (LHV) to be calculated.

There have been considerable studies on char gasification under catalysis of inherent or extraneous metallic species, while underlying non-catalytic gasification has not necessarily received attention, despite the importance to clarify the intrinsic kinetics and its correlation with the structural parameters, such as surface area. The present authors investigated the non-catalytic steam gasification of chars from the pyrolysis of seven types of biomass and lignite. The chars, which were nearly free from catalytic metals, showed reactivities similar to one another with the activation energy within a range from 228 to 241 kJ mol–1. The specific rates of reaction were steady over the entire range of the conversion. In contrast, the specific surface areas of the chars increased with the conversion from around 500 to even beyond 2000 m2 g–1. The results demonstrated that the chars underwent the gasification obeying the first-order kinetics, which was independent of the specific surface area.

Hot-vapor-filtered bio-oils were produced from two different biomass feedstocks, oak and switchgrass, and the oils were evaluated in hydroprocessing tests for the production of liquid hydrocarbon products. Hot-vapor filtering reduced bio-oil yields and increased gas yields. The yields of fuel carbon as bio-oil were reduced by 10% by hot-vapor filtering for both feedstocks. The unfiltered bio-oils were evaluated alongside the filtered bio-oils using a fixed-bed catalytic hydrotreating test. These tests showed good processing results using a two-stage catalytic hydroprocessing strategy. Equal-sized catalyst beds, sulfided Ru on a C catalyst bed operated at 220 °C and sulfided CoMo on an Al2O3 catalyst bed operated at 400 °C were used with the entire reactor at 10 MPa operating pressure. The products from the four tests were similar. The light-oil-phase product was fully hydrotreated, so that nitrogen and sulfur were below the level of detection, while the residual oxygen ranged from 0.3 to 2.0%. The density of the products varied from 0.80 to 0.86 g/mL over the period of the test with a correlated change of the hydrogen/carbon atomic ratio from 1.79 to 1.57, suggesting some loss of catalyst activity through the test. These tests provided the data needed to assess the suite of liquid fuel products from the process and the activity of the catalyst in the relationship to the existing catalyst lifetime barrier for the technology.

Several emulsions consisting of biomass pyrolysis oil (bio-oil) in diesel fuel were produced and analyzed for stability over time. An ultrasonic probe was used to generate microscopic droplets of bio-oil suspended in diesel fuel, and this emulsion was stabilized using surfactant chemicals. The most stable emulsion was produced using a polyethylene glycol dipolyhydroxystearate (PEG-DPHS) surfactant, with a hydrophilic–lipophilic balance (HLB) number of 4.75 and a 32:8:1 ratio of diesel to bio-oil to surfactant, i.e., 20% utilization of bio-oil. This emulsion consisted of uniformly sized droplets with an average diameter of 0.48 μm, with no observed coalescence of droplets after 1 week. If left undisturbed, these droplets would slowly settle to the bottom of the mixture at a rate of only 2.4 mm/day, but this settling can be eliminated with slight mechanical agitation. This level of stability facilitates utilization of 20 wt % raw bio-oil in diesel as a renewable liquid fuel for spray combustion without the need for costly and energy-intensive upgrading. Additionally, GC/MS analysis was used to investigate the relative concentrations of various bio-oil components in the emulsions. This analysis identified levoglucosan as a bio-oil component that may be responsible for the instability of the emulsions. Experiments with bio-oil produced by catalytic fast pyrolysis over HZSM-5 (CFP oil) revealed that the major components of this oil are directly miscible with diesel fuel without the need for an emulsion.

Hydrogen sulfide was oxidatively absorbed by iron-containing ionic liquids, which were synthesized in different molar ratios of FeCl3·6H2O to 1-butyl-3-methylimidazolium chloride. It was found 1-butyl-3-methylimidazolium tetrachloroferrate ([bmim]Fe(III)Cl4), being highly reactive toward H2S, was the dominating iron(III) species independent of molar ratios, but the concentration of iron and chloride as well as the acidic strength lowered with the decrease of molar ratio from 2 to 0.3. Moreover, the acidity and iron(III) concentration had important influence on oxidation of H2S, but their significance varied with the temperature. HCl emissions were also discovered in the oxidation of H2S to S8 and the reduction of [bmim]Fe(III)Cl4 to [bmim]Fe(II)Cl4H. A way for controlling HCl emissions was proposed, involving the decrease in the chloride concentration of iron-containing ionic liquids in the presence of water.

Precombustion CO2 separation is considered to be the most efficient method of carbon removal for fossil fuels. Solid sorbents are promising for CO2 separation because of lower sensible heats, higher CO2 sorption capacities, and favorable adsorption/desorption temperatures. The work reported here continues an effort to develop a Mg(OH)2-based sorbent that adsorbs CO2 at IGCC fuel gas temperatures of 150–200 °C and at 280 psig. One novelty of the sorbent is that the CO2 can also be released near 300 °C at 280 psig reducing downstream compression costs of CO2 capture and storage. This work details thermodynamic equilibrium data that illustrates the optimal regeneration temperature and pressure, Fourier transform infrared data that shows the adsorbed species on the surface of the sorbents, fixed-bed performance testing, and the effect of moisture on regeneration. Additional information on potential heat integration during regeneration is also reported. These findings further demonstrate the ability of the Mg(OH)2 sorbent to capture CO2 from fuel gas streams in an IGCC plant efficiently.

Carbon capture and storage (CCS) can be used to mitigate climate change. Chemical-looping combustion (CLC) is an innovative carbon-capture technology with potential to drastically reduce the capture cost. In CLC, oxygen is transported from combustion air to fuel by means of metal-oxide particles, called oxygen carrier. This work presents findings from a 100 kW CLC reactor system, which is designed as interconnected fluidized beds. The 100 kW unit was operated with ilmenite as the oxygen carrier. Swedish wood char and Mexican petcoke, both having low volatile content, were used as fuel. High gas conversion was achieved with both fuels. The carbon capture efficiency was high with wood char, but not as high with petcoke. The duration of operation was 34.5 h with fuel, of which the majority, 31 h, was achieved with wood char. Oxygen demand was strongly correlated with the solids inventory in the fuel reactor, as has been observed in previous works. Using wood char as fuel, gas conversion was 90–95.3%, except during high fuel power, and carbon capture efficiency was 93–97%, except during high fuel power. The gas conversion should be compared to what has previously been observed in the 100 kW unit, where the highest gas conversion was 84%, using a bituminous coal. Furthermore, comparatively high solid fuel conversion was seen in many tests with wood char—the highest value was 89%. Using petcoke as fuel, high gas conversion was achieved even when employing very high fuel power, 148 kW. The highest gas conversion for petcoke was 89%. The carbon capture efficiency was, however, much lower than what has been observed with pulverized coal and wood char. In summary, this study shows that important improvements can be achieved regarding gas conversion in the 100 kW unit by using low-volatile fuels.

Reduction of carbon dioxide (CO2) emissions into the atmosphere is a key challenge to mitigate the anthropogenic greenhouse effect. CO2 emissions cause lots of problems for the health of humans and increase global warming, in which CO2 uptake decreases these environmental issues. The mineral carbonation process is an alternative method during which industrial wastes rich in calcium (Ca) or magnesium (Mg) react with CO2 to form a stable carbonate mineral. In this research, the feasibility of CO2 mineral carbonation by the use of red gypsum, as a Ca-rich source, was evaluated using an autoclave mini reactor. Wide-range conditions of procedure variables, such as reaction temperature, reaction time, CO2 pressure, and liquid/solid ratio, on the rate of mineral carbonation were studied. The results showed that the maximum conversion of Ca (98.8%) is obtained at the condition that has an optimum amount of these variables. Moreover, the results confirmed that red gypsum has high potential to form calcium carbonate (CaCO3) during the process of CO2 mineral carbonation. It was concluded that the mineral carbonation process using red gypsum can be considered to be an interesting, applicable, and low-cost method in industry to mitigate a considerable amount of CO2 from the atmosphere, which is the main issue in the current and coming years.

In a urea selective catalytic reduction (SCR) system, the urea solution is injected into hot exhaust gas, after which the urea solution becomes ammonia that acts as a reducing agent for de-NOx through evaporation, thermolysis, and hydrolysis. The formation of the reducing agent from urea decomposition is closely connected with thermofluid dynamics as well as various chemical reactions. An experimental study was performed to investigate urea decomposition in a low-temperature environment that is similar to the emission gas temperature of a large marine diesel engine. Also, this study investigated urea decomposition in conjunction with thermofluid dynamics related to the urea SCR system driving conditions. The modeled exhaust pipe was designed to control the inflow gas temperature and velocity. The urea solution injector was chosen to obtain almost identical spray performance, regardless of the urea solution flow rate, to exclude the effect of the spray on urea decomposition. A multicomponent Fourier transform infrared spectroscopy gas analyzer was used to measure the concentrations of ammonia and isocyanic acid (HNCO) in the modeled exhaust pipe. This study showed that the conversion efficiencies of ammonia and HNCO were different under the experimental conditions of this study, although there is no difference between the conversion efficiencies of ammonia and HNCO in theoretical urea thermolysis. Also, it showed that there is no need for a long residence time to improve the total conversion efficiency at a low temperature.

Phase-change ionic liquids, or PCILs, are salts that are solids at normal flue gas processing temperatures (e.g., 40–80 °C) and that react stoichiometrically and reversibly with CO2 (one mole of CO2 for every mole of salt at typical postcombustion flue gas conditions) to form a liquid. Thus, the melting point of the PCIL–CO2 complex is below that of the pure PCIL. A new concept for CO2 separation technology that uses this key property of PCILs offers the potential to significantly reduce parasitic energy losses incurred from postcombustion CO2 capture by utilizing the heat of fusion (ΔHfus) to provide part of the heat needed to release CO2 from the absorbent. In addition, the phase transition yields almost a step-change absorption isotherm, so only a small pressure or temperature swing is required between the absorber and the stripper. Utilizing aprotic heterocyclic anions (AHAs), the enthalpy of reaction with CO2 can be readily tuned, and the physical properties, such as melting point, can be adjusted by modifying the alkyl chain length of the tetra-alkylphosphonium cation. Here, we present data for four tetrabutylphosphonium salts that exhibit PCIL behavior, as well as detailed measurements of the CO2 solubility, physical properties, phase transition behavior, and water uptake for tetraethylphosphonium benzimidazolide ([P2222][BnIm]). The process based on [P2222][BnIm] has the potential to reduce the amount of energy required for the CO2 capture process substantially compared to the current technology that employs aqueous monoethanolamine (MEA) solvents.

A fuel reactor with a fuel-injection system for liquid fuels was designed and built for a chemical-looping reactor system with the nominal fuel input of 10 kWth. The gas velocities in the riser section and at the gas-distribution nozzles of this unit are comparable to those of industrial circulating fluidized-bed boilers. Proof-of-concept experiments were performed with a calcium manganite-based oxygen carrier and a fuel oil with low sulfur content. Fuel conversion was high but not complete, and most of the fuel carbon was converted to CO2 in the fuel reactor. Long-term experiments were performed using an ilmenite oxygen-carrier. The oxygen carrier was exposed to fluidization at hot conditions (more than 600 °C) for about 204 h, out of which fuel was injected during a total of 66.6 h. The parameters temperature, fuel flow, steam flow in the fuel reactor, fluidization medium in the fuel reactor, and air flow in the air reactor were varied to observe trends in fuel conversion. Most of the experiments were carried out with a fuel flow corresponding to 4 kWth and an oxygen carrier-to-fuel ratio of about 2100 kg/MWth. At 1050 °C the fuel could be oxidized to about 87%, and up to 88% of all carbon leaving the fuel reactor was in the form of CO2. No defluidization or agglomeration problems were experienced over the course of the experimental campaign.

The recent expansion of unconventional natural gas production in the United States has enabled a steady increase of its use in all consumption sectors, including transportation. In this study, the environmental footprints of three natural gas-based personal mobility options are examined from a life cycle perspective: battery electric vehicles (BEVs), compressed natural gas vehicles (CNGVs), and fuel cell vehicles (FCVs). The results suggest that natural gas-powered vehicles have the potential to considerably reduce the overall environmental impact associated with driven miles in comparison to conventional petroleum-powered internal combustion engine vehicles (PICVs). BEVs and FCVs in particular offer significant reductions in greenhouse gas emissions, especially if carbon capture and sequestration (CCS) technologies are implemented at the fuel conversion facilities. It was furthermore determined that the use phase dominates the life cycle impacts of all of the vehicles considered, although the manufacture of power sources for BEVs and FCVs significantly contributes to their respective environmental burdens. Efforts presently being exerted for the greener manufacture and more efficient powertrain design of BEVs and FCVs are likely to further extend their environmental advantages over CNGVs for the utilization of natural gas as a transportation energy resource.

Waste water resulted from polymer flooding oil recovery generally has a bad impact on the subsequent process of enhanced oil recovery. Separating residual oil from oil/water (O/W) emulsion with suitable kinds of demulsifier is one strategy generally adopted by oil companies. Because of the existence of large amounts of ultrafine oil droplets with the average diameter less than 2 μm, the emulsions can be extremely difficult to break up. To solve this problem, an amine-based dendrimer demulsifier PAMAM (polyamidoamine) was synthesized in this study, and the efficiency of the demulsifier in dealing with O/W emulsions with ultrafine oil droplets was investigated. Because of its strong interfacial activity and relatively good solubility in water, the dendrimer-based demulsifier can easily attach to emulsified oil droplets in a stable diesel-in-water emulsion. The influences of temperature, settling time, and concentration of the demulsifier used on the efficiency of the demulsifier were investigated in detail. The optimal operating condition under which more than 90% oil was removed from the original emulsion by the demulsifier was found. In contrast, less than 2% oil was removed from the emulsion without applying the demulsifier under the same conditions. Micrographs showed that the PAMAM demulsifier could lead to the breakup of diesel-in-water emulsions with ultrafine oil droplets by flocculation and coalescence. The surface tension and interfacial tension at the diesel–water interface were also measured to give a basic understanding of the demulsification mechanism. Though not perfect in dealing with emulsions with the average oil droplets less than 2 μm due to the relatively high demulsifier dosage, its relatively simple synthetic procedure and mild operating conditions showed a great promise in industrial applications with unique advantages over traditional physical methods.

The transesterification reaction employing supercritical methanol and carbon dioxide used as a co-solvent in the presence of several heterogeneous solid acid catalysts was investigated. The solid acid catalysts were prepared by impregnation methods, with appropriate precursors over magnesium aluminum silicate (cordierite). The catalysts tested were CeO2, WO3, ZnO, ZrO2, ZrO2–SO42–, mixed oxides (50–50%, w/w) WO3– ZrO2, CeO2–ZrO2, ZnO–La2O3, and Al2O3. Reaction tests were conducted at 200 °C and 20 MPa under the condition of 25:1 methanol/oil ratio at a space velocity of 4 min with a fixed-bed continuous flow reactor containing ca. 5 g of catalyst. The best catalytic performance was obtained over ZrO2–SO42– with a yield toward fatty acid methyl esters (FAMEs) of 98%. This value is better to that obtained over the commercial catalyst Nafion SAC-13 (94%). The direct correlation between the conversion and catalyst total acidity was non-existent, but a positive effect of strong acid sites is evidenced.

The improved deactivation kinetic model over mesoporous LaFeO3/MCM-41 sorbents for hot coal gas desulfurization was established with mass-transfer correlation based on elementary stoichiometric equation, which consisted of both the spatial and the time partial differential equations. MATLAB software was used to solve partial differential equations by means of forward finite differential method and to estimate kinetic parameters via nonlinear least-squares fitting. The rate constants ka and kd were obtained via aforementioned kinetic model over different LaFeO3/MCM-41 sorbents. The calculated results were in accordance with experimental data under various operating conditions. The kinetic model can be used successfully to predict the distributions of H2S concentration at different times and spatial positions within fixed-bed layers, compared to unreacted shrinking core model, random pore model, or grain model. It is of very great significance to obtain basical chemical engineering data for the design of new reactor. For 50%LF2/MCM-41 sorbent, the calculated apparent activation energy (Ea) and deactivation energy (Ed) for chemical reaction of LaFeO3 active sites are 32.1 and 15.1 kJ·mol–1, respectively, based on the experimental data of desulfurization process.

The pyrolysis mechanism of fuel under supercritical conditions is an important concern for developing regenerative cooling technology of advanced aircraft using hydrocarbon fuel as the primary coolant. n-Decane as a component of some jet fuels was studied at the temperature range from 773 to 943 K in a flow reactor under the pressure of 3, 4, and 5 MPa. Gas chromatograph/mass spectrometry was used to analyze the pyrolysis products, which were mainly alkanes from C1–C9 and alkenes from C2–C9. A kinetic model containing 164 species and 842 reactions has been developed and validated by the experimental results including the distributions of products and the chemical heat sink of fuel. The decomposition pathways of n-decane were illustrated through the reaction flux analysis. It is concluded that the C4–C9 alkanes are mainly generated by the recombinations of alkyls, while the small alkanes (C1–C3) are formed by H-abstraction reactions by C1–C3 alkyl radicals. The applicability at supercritical pressure and high fuel concentration condition of previous models was discussed, and the performance of the present model in reproducing the experimental data is reasonably good.

In this study, a dynamic model of oil sludge pyrolysis in a rotary kiln with a solid heat carrier was developed. In the proposed model, both the particle motion in the rolling mode and oil sludge pyrolysis were taken into consideration. Saeman’s model and a multiple-reaction model were involved to simulate the bed depth profile inside the rotary kiln based on the solid motion and the volatile evolution, respectively. Furthermore, the temperature profiles of three phases (solid carrier, oil sludge, and gaseous phase) in diverse conditions were predicated by combining pyrolysis kinetics, heat transfer, and motion equations. In the proposed model, the yields of CxHy, H2, CO, and CO2 were successfully stimulated and predicted. The validity of the model was verified from both aspects of solid axial velocity and gas yields by comparing numerical values to literature reports and experimental data, respectively. This simulation practice was expected to provide an alternative approach to obtain helpful parameters for the designing of an industry-scale rotary kiln pyrolyzer.

The catalytic activity of a clay catalyst was studied through the degradation of high-density polyethylene (HDPE) using a thermogravimetric (TG) and fixed bed batch reactor and comparison of that with other catalysts (HZSM-5, all-silica MCM-41, Al2O3, and CaO). The results of TG experiments showed that clay had the same catalytic effects on degradation temperature as Al2O3 and CaO, while HZSM-5 and MCM-41 were able to shift the degradation reaction to lower temperatures. The catalytic degradation results of HDPE with a fixed bed batch reactor showed that the major product over HZSM-5 was fuel gases, all-silica MCM-41 produced the highest fuel oil yield, and the clay catalyst produced the highest yield of liquid products, including wax and oil. Compared with the composition of the gaseous products and fuel oil, that of the clay catalyst was favorable to the formation of alkanes, which indicated that the intermolecular hydrogen transfer reaction was enhanced while the β-scission reaction of radicals was inhibited over a clay catalyst. The results further verified that the catalytic cracking performance of HDPE and the product distributions were related to the textural properties of clay.

Moderate or Intense Low oxygen Dilution (MILD) combustion is a promising technology that offers high thermal efficiency and low pollutant emissions. This study investigates the MILD combustion characteristics of pulverized coal in a laboratory-scale self-recuperative furnace. High-volatile Kingston brown coal and low-volatile Bowen basin black coal with particle sizes in the range of 38–180 μm were injected into the furnace using either CO2 or N2 as a carrier gas. A water-cooled sampling probe was used to conduct in-furnace gas sampling. Measurements of in-furnace gas concentration of O2, CO, and NO, as well as exhaust gas emissions and in-furnace temperatures, are presented. The results suggest major differences between the two coals and minor differences associated with the carrier gas. It was found that the measured CO level of brown coal cases was 10 times higher than that of black coal cases. However, NO emission for brown coal was only 37% of that measured for black coal at an equivalence ratio of Φ = 0.88. Ash content analysis showed that black coal was not burnt effectively, which is thought to be due to the particle residence times being insufficient for complete combustion in the furnace. To augment the experimental measurements, computational fluid dynamic modeling was used to investigate the effects of coal particle size and inlet air momentum on furnace dynamics and global CO emissions. It is found that coal particle size affects the coal penetration depth within the furnace and the location of the particle’s stagnation point. The effects of air inlet momentum are tested in two ways: first, by raising the inlet temperature at a constant mass flow rate, and, second, by increasing the mass flow rate at a constant temperature. In both cases, increasing the air jet momentum broadens the reaction zone and facilitates MILD combustion, but also lowers reaction rates and increases CO emissions.

There is a need to develop feasible PM reduction methods for small-scale biomass combustion installations due to their high PM emissions. In this work, we evaluated the potential of a novel prototype small-scale heat exchanger (PHX) designed for high particle emission reduction. In addition, the role of the different deposition mechanisms in such an application was studied. The PHX was connected to a wood-fired unit, and both particle and gas emissions and thermal efficiencies were evaluated. In addition, a scrubbing system, for keeping the PHX walls clean, was connected to the system. The thermal efficiency reached over 100% due to the recovered heat by water condensation, when operating the PHX at temperatures typical for floor heating. The usage of the scrubber for cleaning the PHX increased the PM1 emissions, compared to the heat exchanger (HX) reference case, but prevented fouling of the PHX tubes. The PHX was found to have fine particle precipitation efficiencies of 45% and 48%, depending on applied water temperatures. The particle reduction was mainly a result of thermophoretic deposition in the heat exchanger tubes.

Chemical looping combustion (CLC) is a kind of efficient combustion technology to capture CO2. In this paper, the reaction characteristics of CO and sintering ore used as an oxygen carrier (OC) in CLC were investigated through thermogravimetric experiments. The effects of the reaction temperature, particle size, and CO concentration on reduction conversions of sintering ore were experimentally studied. The experimental data with high final conversions, obtained during the temperature range of 900 °C, were chosen to analyze the reaction kinetics with diverse models and to have an insight of reduction reaction parameters of sintering ore. In addition, the economy of the circulation of sintering ore was theoretically discussed. The tests of 30 redox cycles were conducted at 900 °C to investigate the recyclability of sintering ore. The sintering ore samples during the cycling tests were morphologically characterized for better understanding of the reaction mechanism.

This study utilized three-dimensional direct numerical simulations (DNS) in order to analyze the effects of turbulent velocity fluctuation, equivalence ratio based on volatile primary fuel in the particulate phase, and the concentration of primary volatile fuel in the background gas on early stages of combustion following successful localized ignition of turbulent pulverized monodispersed coal particle-laden mixtures. For this analysis, coal particles have been treated as point sources and tracked in a Lagrangian manner. It has been found that combustion takes place both in premixed and nonpremixed modes but the extent of premixed (nonpremixed) combustion is stronger (weaker) in turbulent cases than in quiescent laminar cases. The cases with high values of particle equivalence ratio Φp (defined based on total amount of primary volatile fuel available in the particulate phase) have been found to be more susceptible to flame extinction than the cases considered here with small values of Φp. The presence of primary volatile fuel in the background gas is detrimental to the self-sustained combustion for cases with Φp ≥ 2.0, whereas an increase in primary volatile fuel in the background gas acts to decrease the extent of burning for cases with small values of Φp (e.g., Φp = 0.25 and 0.5 cases) within the parameter range considered here(i.e., 0.25 ≤ Φp ≤ 3). Turbulent mixing helps to mix the devolatilized fuel with the surrounding air; thus, an increase in the extent of burning has been observed for small values of turbulent velocity fluctuation, in comparison with the corresponding quiescent laminar mixtures. However, heat transfer from the hot gas kernel overcomes the chemical heat release for high values of turbulent velocity fluctuation, which eventually leads to a failure to obtain self-sustained combustion that is unassisted by external heat addition.

A gas-fired coal preheating (GFCP) technology, offering a flexible method to reduce NOx, could be used with other de-NOx combustion technology such as air staging to seek maximum NOx reduction. The preheating chamber key apparatus of GFCP was investigated with the help of infrared camera. The results show that devolatilization and partial oxidation (combustion) of coal occurred in the preheating chamber, and this may prove the main heat source of preheating chamber is combustion of coal volatiles and gas is only used to prevent flameout. A self-sustaining combustion drop furnace was used to investigate the NOx reduction potential of GFCP with air staging. Gas species concentrations along furnace are plotted for several runs, offering details to further study and analyze the GFCP. With GFCP, much HCN, CiHj, and soot were produced in the preheating chamber, so under the similar air staging condition, the NO destructed by HCN and soot was stronger than that without. NOx reduction could archive up to 72% with GFCP and air staging, if the residence time in the combustion zone could be prolonged, the NOx reduction will be even higher.

A series of electrically heated circular tube experiments was conducted to investigate the influences of physical factors to supercritical RP-3 thermal oxidation coking. The flowing RP-3 kerosene is stressed from 3 to 7 MPa and heated to different bulk temperatures below 450 °C in a stainless tube (1.8 mm inner diameter and 2.2 mm outer diameter, 1Cr18Ni9Ti) with various heat fluxes. Tube surface and liquid-space coking were both collected and weighed using different methods to evaluate the coking characteristics. Besides, some test tube coking compositions were analyzed for the future investigation of chemical reactions. The experimental results show that the fuel temperature is a generated dominant influence factor for tube RP-3 coking, and its influence is greater than the wall temperature. The system pressure has no obvious effect for RP-3 with a high distillation range (C9–C12), and the wall coking quantity also gradually increases with the mass velocity. The average coking rate is proportional to Rein. Moreover, the inlet temperature has little effect on the liquid-space coking, and the coking particles basically have no threat to the fuel path and nozzle.

An experimental and modeling study of the influence of pressure on the oxidation of methyl formate (MF) has been performed in the 1–60 bar pressure range, in an isothermal tubular quartz flow reactor in the 573–1073 K temperature range. The influence of stoichiometry, temperature, pressure, and presence of NO on the conversion of MF and the formation of the main products (CH2O, CO2, CO, CH4, and H2) has been analyzed. A detailed kinetic mechanism has been used to interpret the experimental results. The results show that the oxidation regime of MF differs significantly from atmospheric to high-pressure conditions. The impact of the NO presence has been considered, and results indicate that no net reduction of NOx is achieved, even though, at high pressure, the NO–NO2 interconversion results in a slightly increased reactivity of MF.

The corrosion behavior of a FeCrAl alloy (Kanthal APMT) was investigated in 5% O2 with 40% H2O plus 300 ppm of SO2 at 600 °C in the presence or absence of KCl, and the results were also compared to exposures performed without SO2 and KCl. The influence of preoxidation was also examined. The kinetics was followed using mass gain measurements, and the formed corrosion products were examined using XRD, SEM/EDX, AES, IC, and SIMS. The oxidation rate of Kanthal APMT was very low in O2/N2/H2O + 300 ppm of SO2, and the outward alumina growth appeared to be suppressed. Interestingly, no sulfur was detected at the scale/metal interface. KCl strongly accelerated the corrosion of Kanthal APMT in O2/H2O/N2 at 600 °C, forming K2CrO4 and gaseous HCl. Chromate formation depletes the protective scale in Cr, triggering the formation of a fast growing iron-rich scale. Adding SO2 suppressed the corrosion due to the conversion of the corrosive KCl to the stable K2SO4. If any K2CrO4 was formed on the surface of the material initially, it was also rapidly converted to K2SO4. Preoxidation of Kanthal APMT had a strong beneficial effect on the subsequent exposure at 600 °C in the presence of KCl and SO2, resulting in the formation of K2SO4 and the evaporation of HCl and KCl. In summary, the alumina-forming FeCrAl material Kanthal APMT is not completely inert to KCl in an oxidizing SO2-containing atmosphere at 600 °C. However, the corrosion rate is significantly lower than that of the commonly used chromia-forming alloy, 304L. Preoxidation decreases the corrosion rate even further, making Kanthal APMT a promising candidate material for combustion plant components, particularly from a corrosion point of view.

The pyrolysis kinetics of charring materials plays an important role in understanding material combustions especially for construction materials with complex degradation chemistry. Thermogravimetric analysis (TGA) is frequently used to study the heterogeneous kinetics of solid fuels; however, there is no agreed method to determine the pyrolysis scheme and kinetic parameters for charring polymers with multiple components and competing reaction pathways. This study develops a new technique to estimate the possible numbers of species and sub-reactions in pyrolysis by analyzing the second derivatives of thermogravimetry (DDTG) curves. The pyrolysis of a medium-density fiberboard (MDF) in nitrogen is studied in detail, and the DDTG curves are used to locate the temperature of the peak mass-loss rate for each sub-reaction. Then, on the basis of the TG data under multiple heating rates, Kissinger’s method is used to quickly find the possible range of values of the kinetic parameters (A and E). These ranges are used to accelerate the optimization of the inverse problem using a genetic algorithm (GA) for the kinetic and stoichiometric parameters. The proposed method and kinetic scheme found are shown to match the experimental data and are able to predict accurately results at different heating rates better than Kissinger’s method. Moreover, the search method (K–K method) is highly efficient, faster than the regular GA search alone. Modeling results show that, as the TG data available increase, the interdependence among kinetic parameters becomes weak and the accuracy of the first-order model declines. Furthermore, conducting TG experiment under multiple heating rates is found to be crucial in obtaining good kinetic parameters.

In the absence of prior drying, dewatered sewage sludge (DSS) was directly converted to hydrochars with superior fuel characteristics in subcritical water. Hydrochar derived at 320 °C and 12.0 MPa (SHC-320) was screened for systematic cocombustion with different-rank coals. The results suggest that SHC-320 reduced the activation energy of the blends and altered the main combustion profiles. Meanwhile, blending of SHC-320 induced greater heat loss for higher-rank coals, whereas a higher portion of SHC-320 further improved the ignition reactivity of high-rank coal blends. In the high-temperature region, the value of the pre-exponential factor increased with increasing coal/SHC-320 ratio, resulting in more intense synergistic effects in blends. At a low coal/SHC-320 ratio (30:70), intense antisynergistic effects occurred in cocombustion with low- or high-rank coals. As a result of distinct synergistic interactions, cocombustion with moderate-rank coal achieved the best combustion efficiency among the blends. These findings benefit efficient utilization of DSS as a hydrochar solid fuel in existing cofiring power plants.

Chemical treatment of aromatic heavier hydrocarbons are traditionally done by using cyclic aromatic nonpolar solvents, such as benzene, xylene, and toluene, which have the capability to dissolve asphaltenes. However, these aromatic solvents are volatile and hazardous and hence not advisable to use. Alternatively, lighter hydrocarbons, such as heptane, hexane, etc., show lesser solubility. It is, therefore, crucial that these problems require intelligent, cost-effective, and innovative solutions. The present work investigates the possible solution for the dissolution of heavy crude oil using the application of eight aliphatic ionic liquids (ILs) along with five solvents, namely, toluene, heptane, decane, ethyl acetate, and hexane. Ionic liquids (ILs) based on [CH3COO]−, [BF4]−, [H2PO4]−, and [HSO4]− as anions and with various cations, such as di- and tri-alkyl ammonium, are considered. The enhancement in the solubility of heavy crude oil in solvent + ILs mixture is investigated using Ultraviolet–visible (UV–vis) spectrophotometry, Fourier transform-infrared spectroscopy (FT-IR), and 13C-nuclear magnetic resonance (NMR) spectroscopic techniques. The absorbance of the sample solution (heavy crude oil + solvent + IL) is compared with the standard solution (heavy crude oil in neat solvent alone). It is observed that the dissolution of heavy crude oil is more in the solution with IL than with the solvent alone. Solubility of heavy crude oil in solvents increases to about 70% in the presence of ILs. Hold-time study is also performed to understand the maximum time required for efficient dissolution of heavy crude oil. The hold-time study reveals that solubility of heavy crude oil in heptane increased to about 61–222% in the presence of ILs, as compared to 11–16% in the case of standard solution for a prolonged period of 30 days.

Capillary rise tests were performed to investigate the influences that the structure of the modifier and layer charge of clay had on wetting properties of organoclays, which were prepared by ion exchange using bispyridinium dibromides (BPs) with different spacer length and the reduced-charge montmorillonites (RCMs). Their structures were examined by Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nitrogen adsorption–desorption isotherms. The results indicated that BPs had been successfully intercalated into interlayers and lay in the monolayer. The d001 basal spacing of organo-RCMs increased with the spacer length of BPs increasing, whereas it decreased gradually as the layer charge of the RCMs was decreased, independent of the type of BPs. Whether the organic modification made the Brunauer–Emmett–Teller (BET) surface area increase or decrease depended upon the size of the organic cations and the layer charge of the clays. The wettability alterations of the organo-RCMs for deionized water and cyclohexane were also compared. Both the spacer length of BPs and the layer charge of RCMs had important effects on the relative wettability of organo-RCMs. The hydrophilicity of organo-RCMs was increased with the spacer length of BPs increasing, namely, in the order as follows: C2-2Py-RCMs < C6-2Py-RCMs < C10-2Py-RCMs. In addition, the hydrophobicity was increased with a decrease in the layer charge. The results of this work were supposed to provide some reference information for regulating the wettability of the organo-RCMs by simultaneously controlling the type of modifiers along with the layer charge characteristics, to provide theoretical guidance for the favorable change in reservoir wettability.

Oleic acid (OA)-coated magnetite (Fe3O4) nanoparticles, denoted Fe3O4@OA, were synthesized by co-precipitation in the presence of varying contents of OA. The Fe3O4@OA nanoparticles were characterized by X-ray diffraction, transmission and scanning electron microscopies, Fourier transform infrared spectroscopy, thermogravimetric–differential thermogravimetric analyses, and vibrating sample magnetometry. Increasing the OA content during preparation resulted in an increase of the OA-coating amount (AO, in units of g of OA/g of Fe3O4) on the Fe3O4 surface, before reaching an equilibrium value. The resulting magnetic nanoparticles were nearly spherical with a size of ∼12–14 nm. OA molecules formed a single layer coating on the Fe3O4 surface. The AO and area occupied by a single OA molecule at saturation coating were estimated to be 0.11 g g–1 (1.22 mg m–2) and 0.37 nm2, respectively. The Fe3O4@OA nanoparticles were applied in the demulsification of a cyclohexane-in-water nanoemulsion, under an external magnetic field. The effects of AO, demulsifier dosage, pH, and electrolytes on the demulsification efficiency (ED) were investigated. The ED increased and then decreased with increasing AO, which was attributed to a change in wettability of the magnetic nanoparticles. A maximum ED of ∼98% was observed at a ∼90° contact angle between water and the magnetic nanoparticles. The ED was independent of pH and electrolyte (NaCl or CaCl2) concentration, under the studied conditions. The magnetic demulsifier exhibited excellent stability after reuse over 6 cycles. Fe3O4@OA nanoparticles are effective for oil–water multiphase separation and treating oily wastewater.