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Showing papers in "Energy & Fuels in 2014"


Journal ArticleDOI
TL;DR: In this article, the authors present the properties of modern solid polymer electrolytes (SPEs) for proton exchange membrane (PEM) fuel cells (FCs) and compare them with Nafion membranes.
Abstract: The scientific community is focused on the development of inexpensive and high-performing membrane materials for proton exchange membrane (PEM) fuel cells (FCs). The major approach to reducing the cost of FCs, which is crucial for the widespread acceptance of FCs as energy sources for various practical applications, is reducing the cost of the membrane. Efforts are being made in the development of advanced polymeric materials, which will satisfy the technical and economic demands of the consumers. Because most alternative membranes are outperformed by Nafion membranes over an entire set of important properties, it may be worthwhile to compromise on certain parameters to develop alternative specialized membranes. This review presents the properties (mainly conductivity and chemical and mechanical stability) of modern solid polymer electrolytes (SPEs) for PEM FCs.

545 citations


Journal ArticleDOI
TL;DR: In this article, the chemical and physical properties of asphaltenes and sorbents related to asphalte adsorption are discussed and a review of their properties is provided.
Abstract: Asphaltene adsorption at solid surfaces is a ubiquitous phenomenon that begins within the production well and continues through the entire production chain. It is generally an undesirable phenomenon that causes damage within reservoirs, fouling of pipelines and transportation equipment, and fouling of refining and upgrading equipment. However, by virtue of this phenomenon, problematic asphaltenes may also be selectively removed from petroleum streams to produce partially upgraded petroleum, which has significantly improved handling, processing, and upgrading qualities. This review covers many basic aspects regarding the chemical and physical nature of asphaltenes and sorbents related to asphaltene adsorption.

417 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present the results of imbibition tests using a reservoir crude oil and a reservoir brine solution with a high salinity and a suitable nanofluid that displaces crude oil from Berea sandstone (water-wet) and single-glass capillaries.
Abstract: This paper presents the results of imbibition tests using a reservoir crude oil and a reservoir brine solution with a high salinity and a suitable nanofluid that displaces crude oil from Berea sandstone (water-wet) and single-glass capillaries. The Illinois Institute of Technology (IIT) nanofluid is specially formulated to survive in a high-salinity environment and is found to result in an efficiency of 50% for Berea sandstone, compared to 17% using the brine alone at a reservoir temperature of 55 °C. We also present a direct visual evidence of the underlying mechanism based on the structural disjoining pressure for the crude oil displacement using IIT nanofluid from the solid substrate in high-salinity brine. These results aid our understanding of the role of the nanofluid in displacing crude oil from the rock, especially in a high-salinity environment containing Ca2+ and Mg2+ ions. Results are also reported using Berea sandstone and a nanofluid containing silica nanoparticles.

336 citations


Journal ArticleDOI
TL;DR: In this paper, the porosities and pore characteristics of bulk shales and isolated kerogens were determined for immature, oil-window, and gas-window mature samples from the Lower Toarcian Posidonia shale formation.
Abstract: Sorption capacities and pore characteristics of bulk shales and isolated kerogens have been determined for immature, oil-window, and gas-window mature samples from the Lower Toarcian Posidonia shale formation. Dubinin–Radushkevich (DR) micropore volumes, sorption pore volumes, and surface areas of shales and kerogens were determined from CO2 adsorption isotherms at −78 and 0 °C, and from N2 adsorption isotherms at −196 °C. Mercury injection capillary pressure porosimetry, grain density measurements, and helium pycnometry were used to determine shale and kerogen densities and total pore volumes. Total porosities decrease through the oil-window and then increase into the gas-window. High-pressure methane isotherms up to 14 MPa were determined at 45, 65, and 85 °C on dry shale and at 45 and 65 °C on kerogen. Methane excess uptakes at 65 °C and 11.5 MPa were in the range 0.056–0.110 mmol g–1 (40–78 scf t–1) for dry Posidonia shales and 0.36–0.70 mmol g–1 (253–499 scf t–1) for the corresponding dry kerogens. A...

332 citations


Journal ArticleDOI
Qian Sun1, Zhaomin Li1, Songyan Li1, Lei Jiang1, Jiqian Wang1, Peng Wang1 
TL;DR: In this paper, partially hydrophobic modified SiO2 nanoparticles with an anionic surfactant, sodium dodecyl sulfate (SDS), were used together to increase foam stability.
Abstract: Nitrogen foam flooding is a promising technique for enhanced oil recovery, but instability of the foam limits its application. In this article, partially hydrophobic modified SiO2 nanoparticles with an anionic surfactant, sodium dodecyl sulfate (SDS), were used together to increase foam stability. Micromodel flooding and sandpack flooding were adopted to assess the stability and effect on enhanced oil recovery of the SiO2 stabilized foam (SiO2/SDS foam). The experimental data showed that the foam stability was decreased with an increase in temperature, while the foam volume was increased first and then decreased. SiO2/SDS foam showed better temperature tolerance than the SDS foam (foam stabilized by SDS) due to the adsorption of nanoparticles on the surface of the bubble. Almost all of the bubbles maintained spherical or ellipsoidal shape with prolonged time due to the enhanced surface dilational viscoelasticity, which was different from that of SDS foam. According to the micromodel flooding results, SiO2...

301 citations


Journal ArticleDOI
TL;DR: In this paper, aluminum oxide, titanium dioxide (TiO2), and silicon dioxide (SiO2) were selected for EOR purposes from an intermediate-wet limestone sample at 26, 40, 50, and 60 °C.
Abstract: Recently, researchers have proved the application of nanoparticles (NPs) for enhanced oil recovery (EOR) in ambient temperature. However, to our knowledge no attempt has been undertaken experimentally to investigate the influence of NPs on EOR at higher temperatures. In this study, aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2) were selected for EOR purposes from an intermediate-wet limestone sample at 26, 40, 50, and 60 °C. These metal NPs were dispersed in deionized water at concentration of 0.005 wt %. First, transportation of the NPs through limestone was evaluated. It was found that Al2O3 (8.2%) had the lowest and TiO2 (27.8%) and SiO2 (43.4%) had the highest adsorption on the limestone. Consequently, wettability of the limestone was changed into water-wet through NPs adsorption. The contact angle in the presence of Al2O3, TiO2, and SiO2 nanofluids was measured as 71° ± 2°, 57° ± 2°, and 26° ± 2°, respectively. Interfacial tension was also noticeably reduced with these na...

252 citations


Journal ArticleDOI
TL;DR: In this paper, the pore size distributions of 10 samples from the Lower Cambrian Niutitang Formation in northwestern Hunan were investigated using field emission scanning electron microscopy (FE-SEM), high-pressure mercury intrusion (HPMI), low-pressure nitrogen gas adsorption (LP-N2GA), and carbon dioxide gas adaption(LP-CO2GA).
Abstract: Nanostructure morphology and pore size distributions (PSDs) of 10 samples from the Lower Cambrian Niutitang Formation in northwestern Hunan were investigated using field emission scanning electron microscopy (FE-SEM), high-pressure mercury intrusion (HPMI), low-pressure nitrogen gas adsorption (LP-N2GA), and carbon dioxide gas adsorption (LP-CO2GA). In combination with the geochemical parameters and mineral composition, the factors influencing the nanoscale pore structure were analyzed. The results indicate that the pores in the shale reservoirs are generally nanoscale and can be classified into four types: organic pores, intraparticle pores, interparticle pores, and microfractures, of which the most common are organic nanopores and interparticle pores between clay particles. The nanoscale pores primarily consist of slit-shaped pores with parallel plates and ink-bottle-type pores. The combination of the HPMI, LP-N2GA, and LP-CO2GA curves enabled the creation of the PSD for micro-, meso-, and macroporositi...

230 citations


Journal ArticleDOI
TL;DR: In this article, anatase and amorphous TiO2 nanoparticles were used to improve recovery of heavy oil from sandstone cores, and contact angle measurements were performed on the rock surface before and after treatment with the nanoparticle solution.
Abstract: Anatase and amorphous TiO2 nanoparticles were used to improve recovery of heavy oil from sandstone cores. Before performing core floods, the stability of nanoparticles at different salinities was tested using ζ potential and ultraviolet–visible (UV–vis) methods. While water recovered only 49% of the oil in the core flood experiments, 0.01% anatase structure solution recovered 80% of the oil after injecting two pore volumes at optimum conditions. To understand the mechanism responsible for improved recovery, contact angle measurements were performed on the rock surface before and after treatment with the nanoparticle solution. Contact angle measurements showed that the rock wettability changed from oil-wet to water-wet conditions after treatment with nanoparticles. In 0.01% concentration, scanning electron microscopy (SEM) results showed homogeneous deposition of nanoparticles onto the core plug surface and a few nanorods with a diameter about 60 nm were observed. Energy-dispersive spectrometry (EDS) confi...

227 citations


Journal ArticleDOI
TL;DR: In this article, a set of model compounds (cornstarch and cellulose as model polysaccharides, soy protein and albumin as model proteins, sunflower oil and castor oil as model lipids) were subjected to the processing conditions and product recovery protocol commonly used for hydrothermal liquefaction (HTL) of algal biomass to make crude bio-oil.
Abstract: We subjected a set of model compounds (cornstarch and cellulose as model polysaccharides, soy protein and albumin as model proteins, sunflower oil and castor oil as model lipids) to the processing conditions and product recovery protocol commonly used for hydrothermal liquefaction (HTL) of algal biomass to make crude bio-oil. The model compounds were treated individually and in mixtures at 300 and 350 °C for batch holding time ranging from 10 min to 90 min. The model lipids produced the highest yield (>90 wt %) of biocrude (operationally defined as material soluble in dichloromethane), followed by the model proteins (∼30–35 wt %) and then the model polysaccharides (∼10–15 wt %). The production of biocrude at 350 °C occurred fully within the first 10 min of treatment, and the biocrude yield changed very little at longer times. Liquefaction at 350 °C and 60 min nearly doubled the biocrude yields from polysaccharides, relative to those obtained at 300 °C and 20 min. Otherwise, the yields from the different m...

190 citations


Journal ArticleDOI
TL;DR: In this paper, Biochar (BC) derived from bamboo pyrolysis and its modified forms were treated with chemical methods (oxidation either by KMnO4 or HNO3 and base treatment with NaOH) and heat method.
Abstract: Biochar (BC) derived from bamboo pyrolysis and its modified forms were treated with chemical methods (oxidation either by KMnO4 or HNO3 and base treatment with NaOH) and heat method. BC and modifie...

188 citations


Journal ArticleDOI
TL;DR: In this article, the demulsification mechanism of asphaltene-stabilized water-in-toluene emulsions by an EO-PO-based polymeric demulsifier was studied.
Abstract: The demulsification mechanism of asphaltene-stabilized water-in-toluene emulsions by an ethylene-oxide–propylene oxide (EO–PO) based polymeric demulsifier was studied. Demulsification efficiency was determined by bottle tests and correlated to the physicochemical properties of asphaltene interfacial films after demulsifier addition. From bottle tests and droplet coalescence experiments, the demulsifier showed an optimal performance at 2.3 ppm (mass basis) in toluene. At high concentrations, the demulsification performance deteriorated due to the intrinsic stabilizing capacity of the demulsifier, which was attributed to steric repulsion between water droplets. Addition of demulsifier was shown to soften the asphaltene film (i.e., reduce the viscoelastic moduli of asphaltene films) under both shear and compressional interfacial deformations. Study of the macrostructures and the chemical composition of asphaltene film at the toluene–water interface after demulsifier addition demonstrated gradual penetration ...

Journal ArticleDOI
TL;DR: In this article, the authors measured and compared spontaneous imbibition of oil and water into the crushed packs of the similar shales and found that the intact samples consistently imbibe more oil than water.
Abstract: Recent experiments show the strong water uptake of gas shales which are strongly oil-wet based on contact angle measurements.1,2 Clay hydration, microfracture induction, lamination, and osmotic effect are collectively responsible for the excess water uptake. However, the previous measurements are not sufficient to isolate the above factors nor to explain why the bulk of shale samples can hardly imbibe the oil which completely spreads on their surface. To answer the remaining questions, we measure and compare spontaneous imbibition of oil and water into the crushed packs of the similar shales. In contrast to the intact samples, the crushed samples consistently imbibe more oil than water. The comparative study suggests that the connected pore network of the intact samples is water wet while the majority of rock including poorly connected pores is oil-wet. This argument is backed by complete spreading of oil on fresh surfaces of the rock. In contrast to the artificial pores of crushed rock, the existing pore...

Journal ArticleDOI
TL;DR: In this paper, a magnetic composite poly(styrene-methacrylic acid) microsphere, was prepared using oleic acid-coated magnetic nanoparticles as seeds by microemulsion copolymerization of styrene (St) and methacric acid (MAA), and the lipase from Candida rugosa was then covalently bound to the magnetic polymercoated microspheres by using 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride (EDAC) as an activation re
Abstract: A magnetic composite poly(styrene-methacrylic acid) microsphere, was prepared using oleic acid-coated magnetic nanoparticles as seeds by microemulsion copolymerization of styrene (St) and methacrylic acid (MAA). The lipase from Candida rugosa was then covalently bound to the magnetic polymer-coated microspheres by using 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride (EDAC) as an activation reagent. The immobilization of lipase could enhance the thermal and pH stability of lipase activity when compared to free lipase. The immobilized lipase microspheres were characterized by lipase activity assays, Fourier transform infrared spectroscopy, powder X-ray diffraction, transmission electron microscopy, and vibrating-sample magnetometer techniques. The bound lipase showed high activities to soybean oil transesterification with methanol to produce biodiesel. It was found that the oil conversion of 86% was attained at a reaction temperature of 35 °C for 24 h. The immobilized lipase is stable with re...

Journal ArticleDOI
Huiyan Zhang1, Shanshan Shao1, Rui Xiao1, Dekui Shen1, Jimin Zeng1 
TL;DR: In this article, the authors used Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC), scanning electron microscopy (SEM), transmission electron microscope (TEM), and thermogravimetric analysis (TGA) to study the coke-depositing behaviors of zeolite catalysts.
Abstract: Coke deposition on the zeolite catalysts in the conversion of furan (a main intermediate of biomass fast pyrolysis) is of serious concern for catalyst deactivation and product distribution. It is important to find out the nature and composition of coke on the spent ZSM-5 catalyst to study the coke-depositing behaviors. In this work, spent ZSM-5 catalysts obtained from furan catalytic conversion for chemicals at different reaction times and pyrolysis temperatures were characterized. The spent catalysts were first treated with hydrofluoric acid, and then the organics were extracted with CH2Cl2. The characterization of the origin coke and the treated insoluble coke were analyzed by the combination of some analytical techniques, including Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The extracted organics were analyzed by HPLC to determine the chem...

Journal ArticleDOI
Mo Zheng1, Xiaoxia Li1, Jian Liu1, Ze Wang1, Xiaomin Gong1, Li Guo1, Wenli Song1 
TL;DR: Liulin coal pyrolysis using GPU-enabled high-performance computing with cheminformatics analysis in ReaxFF MD has been investigated in this paper, where the amount of six-membered ring structures was observed to decrease with time and temperature.
Abstract: In this study, the first GPU-enabled ReaxFF MD program with significantly improved performance, surpassing CPU implementations, was employed to explore the initial chemical mechanisms and product distributions in pyrolysis of Liulin coal, a bituminous coal from Shanxi, PRC. The largest coal model ever used in simulation via ReaxFF MD, the Liulin coal molecular model consisting of 28 351 atoms was constructed based on a combination of experiments and classical coal models. The ReaxFF MD simulations at temperatures of 1000-2600 K were performed for 250 Ps to investigate the temperature effects on the product profile and the initial chemical reactions of the Liulin coal model pyrolysis. The generation rates of C-14-C-40 compounds and gas tend to equilibrate within 150-250 ps, indicating that the simulation should allow most of the thermal decomposition reactions complete and the simulated product profiles are reasonable for understanding the chemical reactions of the Liulin coal pyrolysis. The product (gas, tar, and char) evolution tendencies with time and temperature observed in the simulations are fairly in agreement with the experimental tendency reported in the literature. In particular, the evolution trends of three representative products (naphthalene, methyl-naphthalene and dimethyl-naphthalene) with temperature are very consistent with Py-GC/MS experiments. The detailed chemical reactions of the pyrolysis simulation have been generated using VARMD (Visualization and Analysis of Reactive Molecular Dynamics), which was newly created to examine the complexity of the chemical reaction network in ReaxFF MD simulation. The generation and consumption of HO center dot and H3C. radicals with time and temperature are reasonable and consistent both with the evolution of H2O and CH4, and with the detailed chemical reactions obtained as well. The amount of six-membered ring structures was observed to decrease with time and temperature, because of their conversion into 5-membered rings or 7-9-membered rings or even-larger-membered ring structures that will further open and decompose into small fragments. This work demonstrates a new methodology for investigating coal pyrolysis mechanism by combining GPU-enabled high-performance computing with cheminformatics analysis in ReaxFF MD.

Journal ArticleDOI
TL;DR: In this paper, the authors present an overview of the commonly used analytical methods and procedures for the characterization of the liquid pyrolysis products of biomass and discuss the capabilities and limitations of these methods.
Abstract: Biomass is a renewable energy source with great potential. One of the promising ways for the conversion of biomass into more suitable forms of energy is its pyrolysis. Liquid products of the biomass pyrolysis—pyrolysis oils (or bio-oils)—could be used in the future as biofuel or as feedstock for valuable chemicals. Detailed knowledge about their chemical composition is crucial, as it can facilitate the design of processes for the necessary upgrading of bio-oils. This paper outlines current knowledge about the composition of bio-oils and presents an overview of the commonly used analytical methods and procedures for the characterization of the liquid pyrolysis products of biomass. The capabilities and limitations of these methods are discussed as well.

Journal ArticleDOI
TL;DR: The pyrolysis kinetics of charring materials plays an important role in understanding material combustions especially for construction materials with complex degradation chemistry as mentioned in this paper, especially for composite materials.
Abstract: The pyrolysis kinetics of charring materials plays an important role in understanding material combustions especially for construction materials with complex degradation chemistry. Thermogravimetri...

Journal ArticleDOI
TL;DR: In this article, the structural and physical properties of the organic matter present in type II shales in the middle of the oil generation window were determined by using molecular simulations, and consistent results on density, diffusion, and specific adsorption were found between simulated and experimental data.
Abstract: In this work, we use molecular simulations to determine the structural and physical properties of the organic matter present in type II shales in the middle of the oil generation window. The construction of molecular models of organic matter constrained by experimental data is discussed. Using a realistic molecular model of organic matter, we generate, by molecular dynamics simulations, structures that mimic bulk organic matter under typical reservoir conditions. Consistent results on density, diffusion, and specific adsorption are found between simulated and experimental data. These structures enable us to provide information on the fluid distribution within the organic matter, the pore size distributions, the isothermal compressibility, and the dynamic of the fluids within the kerogen matrix. This study shows that a consistent description at the molecular level combined with molecular simulations can be useful, in complement of experiments, to investigate the organic matter present in shales.

Journal ArticleDOI
TL;DR: The marine black shale formations on the Upper Yangtze Platform, South China, are currently exploration targets for shale gas as mentioned in this paper, and they report on the mineralogy, lithofacies, petrophysics, and rock structures.
Abstract: The marine black shale formations on the Upper Yangtze Platform, South China, are currently exploration targets for shale gas. Here, we report on the mineralogy, lithofacies, petrophysics, and rock...

Journal ArticleDOI
TL;DR: In this paper, a morphology-controlling protocol involving hydrothermal preprocessing before pyrolysis is presented to convert cellulosic waste in the form of sugarcane bagasse into three-dimensional (3D) interconnected, conducting, and high surface area carbon nanochannels.
Abstract: A unique morphology-controlling protocol involving hydrothermal preprocessing before pyrolysis is presented to convert cellulosic waste in the form of sugarcane bagasse into three-dimensional (3D) interconnected, conducting, and high surface area carbon nanochannels. The large buffer spaces in such a porous carbon sample yield impressive electrochemical capacitance (Csp) of 280 F/g at a current density of 1 A/g (and 275 F/g at 5 mV/s), with 72% retention even at a very high current density of 20 A/g. In contrast, the non-hydrothermally treated sample exhibits a Csp value of 180 F/g at 1 A/g and only 52% retention at 20 A/g. The much better performance of the hydrothermally preprocessed bagasse-derived carbon (BHAC) can be ascribed to the solvent retention inside the buffer spaces created, negating the diffusional limitations of pore inaccessibility at higher scan rates. The BHAC has a high surface area of 1260 m2/g with a fairly good (11 wt %) concentration of oxygen functionality. The material renders a ...

Journal ArticleDOI
TL;DR: In this paper, an electrically heated vertical tube (2 mm inner diameter) was applied to carry out thermal cracking of supercritical pressure n-decane at various pressures, temperatures, and resident times.
Abstract: The flow and heat-transfer behavior of thermal cracking n-decane was investigated experimentally and numerically. An electrically heated vertical tube (2 mm inner diameter) was applied to carry out thermal cracking of supercritical pressure n-decane at various pressures, temperatures, and resident times. The results showed that the second-order reactions increase the formation rates of the light products (especially CH4 and C2H4) for conversions greater than 13%, while the heavy product (C5–C9) formation rates are decreased. A global reaction model is given for n-decane conversions less than 13%, including 18 main product species. A computational fluid dynamics (CFD) model was developed using the real thermal properties and coupled with fuel flow, heat transfer, and wall thermal conduction. Three turbulence models were tried out and then compared to the experimental results. The “SST k–ω model” can better predict the wall temperature than other turbulence models. The predicted fuel and wall temperatures a...

Journal ArticleDOI
TL;DR: In this article, a co-pyrolysis of pine sawdust and polystyrene was conducted in a fluidized-bed reactor to improve the yields of aromatics and olefins.
Abstract: Biomass catalytic fast pyrolysis can produce aromatics and olefins, which are used as petrochemicals. However, the yields of aromatics and olefins are still very low. In this work, catalytic co-pyrolysis of pine sawdust and plastics (polyethylene, polypropylene, and polystyrene) was conducted in a fluidized-bed reactor to improve the yields of aromatics and olefins. The effects of different temperatures, polyethylene/pine sawdust ratios, different catalysts, and plastics on the product distributions were studied. The results show there are some positive synergistic effects between the two feedstocks. The maximum carbon yield of petrochemicals (71%) was obtained at 600 °C with a spent fluidized catalytic cracking (FCC) catalyst and polyethylene/pine sawdust ratio of 4:1. LOSA-1 presents better catalytic performances than Al2O3 and spent FCC catalysts. The petrochemical carbon yield with LOSA-1 is almost 2 times that without catalyst. Catalytic co-pyrolysis of polystyrene and pine sawdust produced the highe...

Journal ArticleDOI
TL;DR: In this paper, the most interfacially active asphaltene (IAA) subfraction was extracted as an interfacial material from emulsified water droplets in a solution of the solution, and its removal had a profound effect on interfacial and thin emulsion film properties.
Abstract: The asphaltene fraction of crude oil is commonly considered to be responsible for the formation of highly undesirable, stable water-in-crude oil emulsions and rag layers. We developed a new procedure for subfractionation of asphaltenes based on their interfacial activity. The most interfacially active asphaltene (IAA) subfraction was extracted as an interfacial material from emulsified water droplets in asphaltene solution. The IAA subfraction represents less than 2 wt % of whole asphaltenes (WA), but its removal had a profound effect on interfacial and thin emulsion film properties. It was found that the IAA subfraction is a main contributor to emulsion stabilization and formation of rigid oil−water interfaces. IAA adsorbed irreversibly at the oil−water interface and formed interfacial layers of low compressibility. Thin emulsion films of toluene stabilized by IAA were thicker and exhibited severe aging effects in contrast to the films stabilized with remaining asphaltene fractions, which were thin and l...

Journal ArticleDOI
TL;DR: In this paper, the authors evaluate nanoparticle-stabilized CO2 foam stability and effectiveness in enhanced oil recovery at the pore and micromodel scales, and show that the nanoparticles maintain excellent stability within microconfined media and continue to be stable after 10 days, compared to less than 1 day for surfactant foam.
Abstract: In this paper, we evaluate nanoparticle-stabilized CO2 foam stability and effectiveness in enhanced oil recovery at the pore and micromodel scales. The nanoparticle-stabilized CO2 gas-in-brine foams maintain excellent stability within microconfined media and continue to be stable after 10 days, as compared to less than 1 day for surfactant foam. The nanoparticle-stabilized CO2 foams are shown to generate a 3-fold increase in oil recovery (an additional 15% initial oil in place), as compared to an otherwise similar CO2 gas flood. Fluorescence imaging is applied to quantify emulsion size distribution (down to 1 μm) in both CO2 and nanoparticle-stabilized CO2 foam flood cases. Nanoparticle-stabilized CO2 foam flooding results in significantly smaller oil-in-water emulsion sizes with an average size of 1.7 μm (∼80% smaller than a CO2 gas flood), with negligible impact on water-in-oil emulsions. The effectiveness of nanoparticle-stabilized CO2 foam is compared for representative light, medium, and heavy oils. ...

Journal ArticleDOI
TL;DR: In this paper, the effects of both low and high salinity water on the surface properties of crude oil-brine/solid surfaces were investigated and two main surface properties including contact angle and interfacial tension were measured using a pendant drop apparatus.
Abstract: It has been already well established that adjusting the salinity of displacing fluid critically affects the oil recovery efficiency during secondary and tertiary oil recovery processes. In this investigation, systematic experiments are designed and conducted to find the effects of both low and high salinity water on the surface properties of crude oil–brine/solid surfaces. In this respect, the effects of the major salts including NaCl, CaCl2, and MgCl2 are tested in the concentration range of 0–45 000 ppm on fluid/solid and fluid/fluid interactions for a crude oil/water/rock system. Two main surface properties including contact angle and interfacial tension (IFT) are measured using a pendant drop apparatus. The obtained results demonstrate the critical effects of heavy oil components on the interfacial properties. High film stability in some cases resulted in small contact angle changes, mostly in the range of the strongly water wet condition, for different brine salinity.

Journal ArticleDOI
TL;DR: In this article, the pore size distribution is independent of the coal rank but varies with the vitrinite content, and channel-like and interconnected pore structures are observed for both high and low-volatile bituminous coals.
Abstract: Coal is a porous medium with complex pore structures. The characteristics of the pore structure play an important role in various aspects of coal use, including extraction of methane from coal seams, CO2 sequestration in coal, and water purification by activated carbon. To describe comprehensively the pore structure of coal, we apply transmission electron microscopy (TEM) and synchrotron small-angle X-ray scattering (SAXS) measurements to six coal samples from medium to high rank. The positive deviation of SAXS data from Porod’s law was observed. The positive deviation correction of SAXS data was carried out to quantitatively obtain the pore size distribution and specific surface area. We find that the pore size distribution is independent of the coal rank but varies with the vitrinite content; pores in vitrinite-rich coals are smaller than those in vitrinite-poor coals for the same rank. Channel-like and interconnected pores are observed for both high- and low-volatile bituminous coals. Among all coal sa...

Journal ArticleDOI
TL;DR: In this article, the authors investigated the release of chlorine and sulfur during biomass torrefaction and pyrolysis via experiments in two laboratory-scale reactors: a rotating reactor and a fixed bed reactor.
Abstract: The release of chlorine (Cl) and sulfur (S) during biomass torrefaction and pyrolysis has been investigated via experiments in two laboratory-scale reactors: a rotating reactor and a fixed bed reactor. Six biomasses with different chemical compositions covering a wide range of ash content and ash-forming elements were torrefied/pyrolyzed in the temperature range of 150–500 °C. The relative release of chlorine and sulfur was calculated based on mass balance and analysis of the biomass before and after torrefaction. In selected cases, measurement of methyl chloride (CH3Cl) in the gas from straw torrefaction has furthermore been conducted. The release of chlorine from straw was first observed at 250 °C and peaked with about 60–70% at 350 °C. Analysis of the released gas showed that most of the chlorine was released as methyl chloride. Increasing the straw content in the reactor resulted in a lower fractional release of Cl, probably due to more reactive sites in contact with gas phase Cl species leading to se...

Journal ArticleDOI
TL;DR: In this article, the recovery performance of immiscible and miscible CO2 huff-and-puff processes for enhanced oil recovery (EOR) in a light crude oil sample was experimentally investigated.
Abstract: The recovery performance of immiscible and miscible CO2 huff-and-puff processes for enhanced oil recovery (EOR) in a light crude oil sample was experimentally investigated. The minimum miscibility pressure (MMP) of the original light crude oil–CO2 system was determined by means of the vanishing interfacial tension technique and found to be MMP = 9.18 MPa. Then, the solubility of the CO2 in the light crude oil and oil swelling factor due to the CO2 dissolution in the oil phase were determined at T = 30 °C and various equilibrium pressures ranging from atmospheric pressure to Peq = 12.55 MPa. Later, series of immiscible and miscible CO2 huff-and-puff tests were designed and carried out at various operating pressures (i.e., Pop = 5.38–10.34 MPa). The results of the experiments showed that for secondary CO2 huff-and-puff tests performed at the operating pressures below the MMP, the ultimate oil recovery factor is quite low. It was also found that in immiscible CO2 huff-and-puff (i.e., Pop < MMP) scenarios, th...

Journal ArticleDOI
TL;DR: In this paper, the evolution of the structure and reducibility of a CeO2-Fe2O3 oxygen carrier during the chemical-looping steam methane reforming (CL-SMR) was investigated.
Abstract: Chemical-looping steam methane reforming (CL-SMR) is a promising method for the co-generation of pure hydrogen and syngas on the basis of redox cycles via a gas–solid reaction using an oxygen carrier. The performance and life of the oxygen carrier play pivotal roles in determining the feasibility and economy of the CL-SMR process. The present research was focused on the evolution of the structure and reducibility of a CeO2–Fe2O3 oxygen carrier during the CL-SMR redox process to further understand the sustainability of the oxygen carrier. The investigated CeO2–Fe2O3 complex oxide exhibited satisfactory performance in the CL-SMR process because of the chemical interaction between Ce and Fe species. A Ce–Fe–O phase equilibrium based on a stable composition of CeO2, Fe3O4, and CeFeO3 formed in the recycled samples. Surface oxygen was removed, which was accompanied by an increase in the concentration of oxygen vacancies and a decrease in the surface area of the recycled samples; these effects resulted in an in...

Journal ArticleDOI
TL;DR: In this paper, the characteristics of chars from low-temperature pyrolysis of two lignite coals have been investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR).
Abstract: Low-temperature pyrolysis offers a potential way of upgrading lignite and producing chars to replace thermal or pulverized coal injection (PCI) coals in combustion or being used as inert components in a blend for coking. In this study, the characteristics of chars from low-temperature pyrolysis of two lignite coals have been investigated. The changes in char morphology and chemical structures were investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The combustion reactivity of chars was analyzed in a thermogravimetric analyer (TGA) using non-isothermal techniques. The results show that chars from low-temperature pyrolysis of lignite coal below 450 °C were more reactive than higher temperature chars. Higher reactivity of low-temperature chars was attributed to the higher concentration of active sites and lower degree of structural order compared to that of high-temperature chars. Indonesian (YN) lignite showed a higher weight loss rate compared to Hulun...