Showing papers in "Energy & Fuels in 2015"
TL;DR: Deep eutectic solvents (DESs) have been considered as alternatives to ILs that maintain most of their relevant properties, such as task-specific character, and at the same time avoid some of their problems, mainly from economic and environmental viewpoints as discussed by the authors.
Abstract: Sustainable technologies applied to energy-related applications should develop a pivotal role in the next decades. In particular, carbon dioxide capture from flue gases emitted by fossil-fueled power plants should play a pivotal role in controlling and reducing the greenhouse effect. Therefore, the development of new materials for carbon capture purposes has merged as central research line, for which many alternatives have been proposed. Ionic liquids (ILs) have emerged as one of the most promising choices for carbon capture, but in spite of their promising properties, some serious drawbacks have also appeared. Deep eutectic solvents (DESs) have recently been considered as alternatives to ILs that maintain most of their relevant properties, such as task-specific character, and at the same time avoid some of their problems, mainly from economic and environmental viewpoints. DES production from low-cost and natural sources, together with their almost null toxicity and total biodegradability, makes these sol...
719 citations
TL;DR: In this paper, the authors explored the mechanism leading to improved oil recovery in carbonate rock and showed that brine composition and (somewhat reduced) salinity can have a positive impact on oil recovery.
Abstract: The low-salinity effect (LSE) in carbonate rock has been less explored in comparison to sandstone rock. Laboratory experiments have shown that brine composition and (somewhat reduced) salinity can have a positive impact on oil recovery in carbonates. However, the mechanism leading to improved oil recovery in carbonate rock is not well understood. Several studies showed that a positive low-salinity flooding (LSF) effect might be associated with dissolution of rock; however, because of equilibration, dissolution may not contribute at reservoir scale, which would make LSF for carbonate rock less attractive for field applications. This raises now the question whether calcite dissolution is the primary mechanism of the LSF effect. In this paper, we aim to first demonstrate the positive response of carbonate rock to low salinity and then to gain insight into the underlying mechanism(s) specific to carbonate rock. We followed a similar methodology as in sandstone rock [Mahani, H.; Berg, S.; Ilic, D.; Bartels, W....
374 citations
TL;DR: In this paper, the heat capacity in the ideal gas state is predicted to increase as a function of temperature, as obtained from quantum mechanics at the semi-empirical level (MOPAC-PM7).
Abstract: Molecular modeling is applied to a representative array of kerogens for the purpose of obtaining quantitative predictions of thermodynamic properties from quantum mechanics and volumetric properties from molecular dynamics. The kerogen model units (175–260 carbon atoms) have been built in the MedeA environment from the sole consideration of the elemental analysis and functional group analysis documented in the work of Exxon and IFP-EN scientists [Kelemen, S. R., et al., Energy Fuels, 2007, 21 (3), pp 1548–1561]. The density results are in good agreement with the well-documented trends of kerogen density with thermal maturity and organic type. The heat capacity in the ideal gas state is predicted to increase as a function of temperature, as obtained from quantum mechanics at the semiempirical level (MOPAC-PM7). This result is in quantitative agreement with experimental heat capacity data on type I kerogen and on coal. This behavior appears clearly as a nonclassical feature, because of the quantization of e...
342 citations
TL;DR: In this article, the impacts of different nanofluids of zirconium dioxide (ZrO2), calcium carbonate (CaCO3), titanium dioxide (TiO 2 ), silicon dioxide (SiO 2), magnesium oxide (MgO), aluminum oxide (Al2O3), cerium oxide (CeO2) and carbon nanotube (CNT) on the wettability of carbonate rocks were investigated.
Abstract: Nanofluids have been recently proposed as new chemical agents for enhanced oil recovery from oil reservoirs. Various nanofluids have been studied in that regard and reported in the literature, verifying the capability of nanostructured materials in enhancing the oil recovery through alteration of rock wettability. In this study, the impacts of different nanofluids of zirconium dioxide (ZrO2), calcium carbonate (CaCO3), titanium dioxide (TiO2), silicon dioxide (SiO2), magnesium oxide (MgO), aluminum oxide (Al2O3), cerium oxide (CeO2), and carbon nanotube (CNT) on the wettability of carbonate rocks were investigated. A series of preliminary contact angle evaluations were performed to screen the nanoparticles. The performances of the selected nanofluids were evaluated by spontaneous imbibition and core flooding experiments. Results of spontaneous imbibition tests and coreflooding experiments confirm the active roles of CaCO3 and SiO2 nanoparticles for enhancing oil recovery. In addition, the effect of nanofl...
217 citations
TL;DR: In this article, the authors investigated the synergistic effects of using a blend of silica nanoparticles (NPs) and anionic surfactants on foam stability in both bulk and porous media.
Abstract: Surfactant-stabilized foams have been used in the past for vertical conformance and mobility control in gas-enhanced oil recovery processes. Lack of stability of these foams often limits their application. The goal of this study is to investigate the synergistic effects of using a blend of silica nanoparticles (NPs) and anionic surfactants on foam stability in both bulk and porous media. First, the stability of static foams was studied using surfactants and surfactant–NP mixtures with and without the presence of a crude oil. Second, the foam drainage behavior and thickness of the foam lamella were studied by fluorescence microscopy. Third, the mobility of foams was measured by coinjecting the surfactant or surfactant–NP solution with nitrogen gas through a Berea sandstone core at a fixed foam quality (gas volume fraction). Finally, oil displacement experiments were conducted in Berea cores using these foams. Static foam tests indicated a stabilization effect of nanoparticles on surfactant–NP-stabilized fo...
195 citations
TL;DR: In this article, the authors present a review of adsorption-based removal of SOx/NOx impuritie, showing that significant energy and cost savings can potentially be realized by using advanced adsorbent materials.
Abstract: One of the main challenges in the power and chemical industries is to remove generated toxic or environmentally harmful gases before atmospheric emission. To comply with stringent environmental and pollutant emissions control regulations, coal-fired power plants must be equipped with new technologies that are efficient and less energy-intensive than status quo technologies for flue gas cleanup. While conventional sulfur oxide (SOx) and nitrogen oxide (NOx) removal technologies benefit from their large-scale implementation and maturity, they are quite energy-intensive. In view of this, the development of lower-cost, less energy-intensive technologies could offer an advantage. Significant energy and cost savings can potentially be realized by using advanced adsorbent materials. One of the major barriers to the development of such technologies remains the development of materials that are efficient and productive in removing flue gas contaminants. In this review, adsorption-based removal of SOx/NOx impuritie...
178 citations
TL;DR: In this article, the porosity of the Union Springs (Shamokin) Member of the Marcellus Formation from a core drilled in Centre County, PA, USA, using ultrasmall-angle neutron scattering (USANS), small-angle neut scattering (SANS), focused ion beam scanning electron microscopy (FIB-SEM), and nitrogen gas adsorption.
Abstract: The production of natural gas has become increasingly important in the United States because of the development of hydraulic fracturing techniques, which significantly increase the permeability and fracture network of black shales. The pore structure of shale is a controlling factor for hydrocarbon storage and gas migration. In this work, we investigated the porosity of the Union Springs (Shamokin) Member of the Marcellus Formation from a core drilled in Centre County, PA, USA, using ultrasmall-angle neutron scattering (USANS), small-angle neutron scattering (SANS), focused ion beam scanning electron microscopy (FIB-SEM), and nitrogen gas adsorption. The scattering of neutrons by Marcellus shale depends on the sample orientation: for thin sections cut in the plane of bedding, the scattering pattern is isotropic, while for thin sections cut perpendicular to the bedding, the scattering pattern is anisotropic. The FIB-SEM observations allow attribution of the anisotropic scattering patterns to elongated pore...
173 citations
TL;DR: In this paper, the pore size distribution and architecture in gas shales were studied using a combination of small-angle neutron scattering (SANS), mercury injection capillary pressure (MICP), and helium ion microscopy (HIM).
Abstract: The pore size distribution and architecture in gas shales were studied using a combination of small-angle neutron scattering (SANS), mercury injection capillary pressure (MICP), and helium ion microscopy (HIM). SANS analysis shows that the pore size population is not a power-law distribution across many length scales, typical of sedimentary rocks, but contains an anomalous population of pores on-the-order ∼2 nm, housed primarily in the organic matter. A model is presented showing how a “foamy porosity” with such a characteristic size is a direct result of diagenetic evolution of kerogen. Cross-linking of the kerogen combined with phase separation of gas/oil, leads to arrested coarsening with a length scale set by the cross-length density. These pore populations determined by the scattering model are directly supported by HIM images. Pore connectivity determined through pore-size-to-pore-throat analysis, suggests that interpore connections are also distinct from typical sedimentary rocks. The pore/throat r...
171 citations
TL;DR: In this paper, the Sandia National Laboratories LDRD program was used to support the University of Wyoming Enhanced Oil Recovery Institute (UEHI). But the Wold Chair was not involved in this work.
Abstract: Funding from the Sandia National Laboratories LDRD program is appreciated. A.N.U. thanks the member companies of the DigiCore Consortium and Wettability Satellite for funding. Support at UW was provided by Chevron, BP, and Statoil, the Wold Chair, and the University of Wyoming Enhanced Oil Recovery Institute.
166 citations
TL;DR: In this article, the authors investigated the changes in biomass physicochemical characteristics during torrefaction and its influence on the resulting pyrolysis behavior and found that the main reactions occurring during torification were dehydration, deacetylation, and cleavage of ether linkages.
Abstract: This study investigated the changes in biomass physicochemical characteristics during torrefaction and its influence on the resulting pyrolysis behavior. Torrefaction reduced biomass hemicellulose content and increased the high heating value and the mass energy density. Two-dimensional perturbation correlation analysis, based on diffuse reflectance infrared Fourier transform spectroscopy, showed that the main reactions occurring during torrefaction were dehydration, deacetylation, and cleavage of ether linkages. A distributed activation energy model with three Gaussian functions and weighting factors was used to study the pyrolysis kinetics, and it was found that as the torrefaction temperature increased, the contribution of lower activation energy parallel reactions to devolatilization decreased, while condensation became more important. The yields of acids and furans from the pyrolysis of torrefied biomass also decreased. The lignin side branches were cleaved during high temperature torrefaction, result...
159 citations
TL;DR: In this paper, the physicochemical characterization of common lignocellulosic agricultural residues available in India was carried out by higher heating value, crystallinity index, thermal properties, CHNS/O analysis, FTIR, metal analysis, and compositional analysis.
Abstract: Lignocellulosic material (LCM) has been considered as a potent feedstock for biofuel production either as gaseous, liquid, and/or solid fuel to meet the energy demands. Conversion of lignocellulosic materials to biofuels is possible mainly by two processes, i.e., thermochemical and biochemical. For overall efficiency of processes designed to convert the lignocellulosic materials into the desired biofuel, it is important to understand the characteristics of these lignocellulosic components. The present study aims for physicochemical characterization of common lignocellulosic agricultural residues available in India, i.e., rice straw, rice husk, cotton stalk, wheat straw, bagasse, corn stover, sorghum stalk, mustard stalk, corn cob, and jatropha pruning. Physical and chemical characterization of lignocellulosic samples is carried out by higher heating value, crystallinity index, thermal properties, CHNS/O analysis, FTIR, metal analysis, and compositional analysis. Among all of the biomass samples analyzed, ...
TL;DR: The European consortium SOLARJET has experimentally demonstrated the first ever production of jet fuel via a thermochemical H2O/CO2-splitting cycle using simulated concentrated solar radiation.
Abstract: The European consortium SOLARJET has experimentally demonstrated the first ever production of jet fuel via a thermochemical H2O/CO2-splitting cycle using simulated concentrated solar radiation. The key component of the production process of sustainable “solar kerosene” is a high-temperature solar reactor containing a reticulated porous ceramic (RPC) foam structure made of pure CeO2 undergoing a 2-step redox cyclic process. During the first endothermic reduction step at 1450–1600 °C, the RPC was directly exposed to concentrated thermal radiation with power inputs ranging from 2.8 to 3.8 kW and mean solar flux concentration ratios of up to 3000 suns. In the subsequent exothermic oxidation step at 700–1200 °C, the reduced ceria was stoichiometrically reoxidized with CO2 and/or H2O to generate CO and/or H2. The RPC featured dual-scale porosity: millimeter-size pores for volumetric radiation absorption during reduction and micrometer-size pores within its struts for enhanced oxidation rates. For a cycle durati...
TL;DR: In this paper, the authors examined the correlation between the fundamental properties of foam and the scalable parameters of the porous medium and found that the value of fmdry decreases with increasing permeability.
Abstract: Accurate modeling of foam rheology on the field scale requires detailed understanding of the correlation between the fundamental properties of foam and the scalable parameters of the porous medium. It has been experimentally observed that foam experiences an abrupt coalescence when the capillary pressure in the porous medium approaches a certain value referred to as the “limiting capillary pressure”, Pc*. Current foam models that treat foam texture implicitly mimic this fundamental behavior with a so-called dry-out function, which contains adjustable parameters like fmdry and epdry (in the STARS foam simulator). Parameter fmdry (called Sw* in other models) represents the water saturation corresponding to the limiting capillary pressure, Pc*, and epdry determines the abruptness of foam coalescence as a function of water saturation. In this paper, using experimental data, we examine the permeability dependence of these parameters. We find that the value of fmdry decreases with increasing permeability. We also find that, for the data examined in this paper, the transition from the high-quality regime to low-quality regime is more abrupt in lower-permeability rocks. This implies that in high-permeability rocks foam might not collapse abruptly at a single water saturation; instead, there is a range of water saturation over which foam weakens. In addition, we address the question of whether Pc* is dependent on formation permeability. We estimate Pc* from data for foam mobility versus foam quality and find, as did Khatib et al. (SPE Reservoir Eng., 1988, 3 (3), 919–926), who introduced the limiting capillary pressure concept, that Pc* can vary with permeability. It increases as permeability decreases, but not enough to reverse the trend of increasing foam apparent viscosity as permeability increases.
TL;DR: In this article, the structural and morphological properties of hexagonal CeO2 nanoparticles have been made using X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and TEM analyses.
Abstract: Hexagonal CeO2 nanoparticles have been prepared through the hydrothermal method using cetyltrimethylammonium bromide (CTAB) as the surfactant. The structural and morphological studies have been made using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. The electrochemical behavior of CeO2 nanoparticles was investigated using cyclic votammetry (CV), charge–discharge (CHDH) studies, and alternating current (AC) impedance spectroscopy in different neutral electrolytes, such as NaCl, KCl, Na2SO4, and K2SO4. Maximum specific capacitance of 523 F g–1 was attained with the NaCl electrolyte at 2 mV s–1. The capacitance values obtained with various electrolytes are in the order of NaCl > Na2SO4 > KCl > K2SO4. CHDH and impedance analyses further confirm this behavior. After 2000 cycles of charging and discharging, only 18% degradation in the specific capacitance could be observed. All of the electrochem...
TL;DR: In this article, the authors reviewed historical models for cellulose pyrolysis and mathematical approaches to kinetic analysis with the objective of identifying the correct global chemical kinetic models and parameters.
Abstract: Historical models for cellulose pyrolysis and mathematical approaches to kinetic analysis are reviewed with the objective of identifying the correct global chemical kinetic models and parameters for cellulose pyrolysis. In most recent experiments, cellulose pyrolysis clearly has sigmoidal reaction character, which is consistent with one of a sequential, nucleation–growth, or random-scission global model. The apparent activation energy of ∼47 kcal/mol is consistent with mechanistic modeling if one allows catalytic acceleration of the concerted initiation reaction. There is a possibility that part of the sigmoidal character is due to adsorption effects at low pyrolysis temperatures, but further work is required to resolve this issue. Reasons are given for why fitting data at a single heating rate to a first-order reaction model gives incorrect results.
TL;DR: In this article, molecular dynamics simulations were employed to investigate the aggregation anti orientation behaviors of asphaltene molecules in a vacuum and at various water surfaces, and the results obtained in this work will be of significance in guiding the development of demulsification technology.
Abstract: It is well known that asphaltene molecules play a significant role in stabilizing emulsions of water in crude oil or diluted bitumen solutions: Molecular dynamics simulations were employed to investigate the aggregation anti orientation behaviors of asphaltene molecules in a vacuum and at various water surfaces. Two different continental model asphaltene molecules were employed in this work. It was found that the initially disordered asphaltenes quickly self-assembled into ordered hanoaggregates consisting of several molecules, in which the aromatic rings in asphaltenes were reoriented to form a face-to-face stacked structure. More importantly, statistical analysis indicates that most of the stacked polycyclic aromatic planes of asphaltene nanoaggregates tend to be perpendicular to the water surface. Tithe asphaltene molecules are considered as "stakes", then the asphaltene nanoaggregate can be regarded as a "fence". All the fence,like nanoaggregates were twined and knitted together, which pinned them perpendicularly on the water surface to form a steady protective ail wrapping the water droplets. The mechanism of stabilization Of the water/oil emulsions is thereby well understood. Demulsification processes using a chemical demulsifier were also studied. It was observed that the asphaltene protective film was destroyed by a demulsifier of ethyl cellulose molecules, leading to exposure of the water droplet. The results obtained in this work will be of significance in guiding the development of demulsification technology.
TL;DR: In this paper, a hydrothermal carbonization technique was employed to generate a high heating value (HHV) hydrochar, which showed that its HHV increased 47% after treatment at 230 °C for 1.5 h.
Abstract: Upgrading corncob residues (CCR) to a high quality energy resource is an effective utilization of an underutilized industrial lignocellulose waste. A hydrothermal carbonization technique was therefore employed to generate a high heating value (HHV) hydrochar. Results showed that its HHV increased 47% after treatment at 230 °C for 1.5 h. Decreases in H/C and O/C verified that reductions in C and O reactions were occurring following hydrothermal carbonization. The chemical and thermal properties of the final hydrochar as analyzed by FT-IR, TG/DTG, and XRD analyses indicated that dehydration and decarboxylation were the predominant pathways for the C and O reductions. The present hydrothermal carbonization process is offered as a promising approach to upgrade CCR to a high heating value hydrochar under mild conditions.
TL;DR: In this article, an amphiphilic material, graphene oxide (GO) nanosheets, was introduced as a versatile demulsifier to break up the oil-in-water emulsion at room temperature.
Abstract: Seeking highly efficient, rapid, universal, and low-cost demulsification materials to break up the crude/heavy oil-in-water emulsion and emulsified oily wastewater at ambient conditions has been the goal of the petroleum industry. In this work, an amphiphilic material, graphene oxide (GO) nanosheets, Was introduced as a versatile demulsifier to break up the oil-in-water emulsion at room temperature. It was encouraging to find that the small oil droplets in the emulsion quickly coalesced to form the oil phase and separated with the water within a few minutes. The demulsification tests indicated that the residual oil in separated water samples was as low as similar to 30 mg/L, corresponding to a demulsification efficiency over 99.9% at an optimum GO dosage. More importantly, GO not only is useful for ordinary crude oil emulsion but also can be used to break up the extra heavy oil emulsion. The effect of the emulsion pH on the demulsification was also investigated. It was interesting to find that the. distribution of GO either in oil or in water phase after demulsification was dependent on the pH value of the solution, which was attributed to the pH-dependent amphiphilicity of GO. The prominent demulsification ability of GO was attributed to the strong adsorption between the GO nanosheets and molecules of asphaltenes/resins driven by pi-pi interactions and/or n-pi interactions. The findings in this work indicate that the GO nanosheets are a simple, highly efficient, and universal demulsifier to separate the oil from the crude/heavy oil-in-water emulsions at ambient conditions, which shows a good application prospect in the oil industry.
TL;DR: In this article, the use of fast pyrolysis bio-oil (FPBO) has been demonstrated to be a viable option to replace heavy fuel oil in district heating applications.
Abstract: Fast pyrolysis of woody biomass is close to full maturity, with first-of-its-kind commercial size installations for fuel production being commissioned in Finland (Fortum) and in The Netherlands (Empyro), and in the design phase in Brazil (Ensyn). In the industrial-scale combustion tests, the use of fast pyrolysis bio-oil (FPBO) has been demonstrated to be a viable option to replace heavy fuel oil in district heating applications. Commercially usable district heating boilers and burners suitable for FPBO are available. There is research on diesel-engine and gas-turbine applications but, so far, no proven demonstrations. FPBO is completely different from mineral oils; hence, standards are needed. Analytical methods have been systematically validated and modifications to the standards as well as completely new methods have been made. Two ASTM burner fuel standards already exist and European boiler fuel grades are being developed under CEN. The focus on CEN standardization is on boiler use, because of its com...
TL;DR: In this article, the authors investigated the behavior of low concentration of TiO2 nanoparticles in core plug porous media and the mechanism of increasing oil recovery, and showed that the presence of only 0.5% of injected nanoparticles indicated high affinity of the nanoparticles for deposition in porous media.
Abstract: Although application of nanoparticles in enhanced oil recovery has been reported, understanding the transport and retention of nanoparticles in the oilfield reservoir is still a crucial issue. In this research, behavior of low concentration of TiO2 nanoparticles in core plug porous media and the mechanism of increasing oil recovery were investigated. Flooding test with a concentration of 0.01% TiO2 nanoparticles showed improvement in sweeping heavy oil from 41% to 55%. Inductively coupled plasma results on the exiting effluent of the flooding test with a concentration of 0.05% TiO2 nanoparticles showed the presence of only 0.5% of injected nanoparticles, which indicates high affinity of the nanoparticles for deposition in porous media. The total amount of deposited TiO2 extracted from different cross sections of the core plug was consistent with the difference of injected and exited TiO2 material. At the entrance side, the amount of deposited TiO2 was high but decreased significantly in 0.1 cm depth, and ...
TL;DR: In this article, an in-depth investigation was carried out on five Chinese coals using a range of advanced analytical techniques focused specifically on extracting structural parameters, which indicated that FTIR spectroscopy coupled with appropriate data analysis can be successfully used to determine aromaticity and coal rank.
Abstract: An in-depth investigation was carried out on five Chinese coals using a range of advanced analytical techniques focused specifically on extracting structural parameters. Detailed investigations were carried out using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray diffraction followed by peak deconvolution and data analysis. Correlations were established for parameters determined from different techniques. The FTIR data showed good linear relationships between the apparent aromaticity (fa(FTIR)) and (R/C)u with the H/C atomic ratio for all coals under investigation. These results indicate that FTIR spectroscopy coupled with appropriate data analysis can be successfully used to determine aromaticity and the coal rank. Raman spectroscopy data showed a negative linear relationship between the GL fraction and H/C ratio; no well-defined relationship was observed between other band fractions and the H/C ratio. The decrease of AD/AG with increasing H/C ratio indicates the growth of ...
TL;DR: In this paper, the thermodynamics of thermochemical fuel production using a CeO2 redox cycle are studied, with both sweep gas and vacuum pumping considered as methods of achieving this.
Abstract: In this work the thermodynamics of thermochemical fuel production using a CeO2 redox cycle are studied. The need to reduce the oxygen partial pressure in order to improve efficiency is investigated, with both sweep gas and vacuum pumping considered as methods of achieving this. At ambient pressure the cycles can be maximized with respect to the temperature swing, the minimum oxygen partial pressure, and the extent of the oxidation reaction. For reduction at 1500 °C the maximum efficiency was found to be 4.5%, which is significantly lower than the values found in previous studies. In addition isothermal operation had very low efficiency (less than 2%) under all of the conditions considered. If the system is operated at lower than ambient pressure, the pumping efficiency will depend on the pressure. From an investigation of commercially available pumps the pressure dependence was given an analytical expression. The results showed the cycles have an optimal operating pressure and that using sweep gas, as wel...
TL;DR: In this article, the authors investigated the interactions of the saturate, aromatic, resin, and asphaltene (SARA) four fractions and the correlation between fractions and atomic force microscopy in asphalts.
Abstract: Molecular dynamics provides a powerful tool to understand the elusive structure–performance relationship of asphalts. The combined molecular models were selected to investigate the interactions of the saturate, aromatic, resin, and asphaltene (SARA) four fractions and the correlation between fractions and the “bee-like structures” by atomic force microscopy in asphalts. The results showed that van der Waals was the main force to control intermolecular interactions. The arrangement of SARA fractions largely conformed to the modern colloid theory. However, some alkanes, sulfides, and condensed aromatics had different behaviors. Long-chain alkanes inserted into layers of asphaltenes, and small sulfides without long alkyl chains adhered to large sulfides or asphaltenes; nevertheless, counterpart condensed aromatics became much closer to those molecules. Strong interactions between the dispersed phase and continuous phase generated a larger size and greater number of “bee structures”. Asphaltenes played as a c...
TL;DR: In this article, the effects of the initial IFT values, the dynamic reduction rate of IFT, and the surfactant concentration and emulsification on oil recovery through core flooding experiments were investigated.
Abstract: Surfactant flooding as a potential enhanced oil recovery technology in depleted reservoirs after water flooding has attracted extensive attention. In this study, 12 surfactants belonging to five different types of surfactants and their compounded formulations were investigated for surfactant flooding under 90–120 °C and 20 × 104 mg/L salinity. Two surfactant formulations obtained a stable ultralow interfacial tension (IFT) level (≤10–3 mN/m) with crude oil after aging for 125 days. The surfactant formulations were used to further investigate the effects of the initial IFT values, the dynamic reduction rate of IFT, and the surfactant concentration and emulsification on oil recovery through core flooding experiments. The results indicated that oil recovery increased with the decrease of the initial IFT values and the increase of the dynamic reduction rate of IFT. The 10–3 mN/m IFT level yielded an additional oil recovery of approximately 7% compared with the 10–1 mN/m IFT level. However, under the same IFT ...
TL;DR: In this article, the structural characteristics of bitumen and type I kerogen were compared using quantitative Fourier transform infrared (IR) spectroscopy, and it was shown that bitumen has a structure intermediate between that of kerogen and generated petroleum.
Abstract: A series of artificial maturation (anhydrous, semi-open pyrolysis) experiments on Green River oil shale have been performed to simulate the thermal maturation of type I kerogen. The goals of this program were to develop a kinetic model of petroleum generation from oil shale and to characterize the yield and composition of petroleum as a function of artificial thermal maturity. The thermal maturity level (EASY%Ro = 0.48–1.28%) is based upon the kinetic model of kerogen degradation and is equivalent to vitrinite reflectance maturity. Here, we compare the structural characteristics of kerogen and bitumen during artificial maturation of oil shale using quantitative Fourier transform infrared (IR) spectroscopy. Quantitative comparison was enabled by a novel method for the preparation of bitumen for IR spectroscopy. Bitumen can be a reaction intermediate during maturation of kerogen, and the IR data indicate that bitumen has a structure intermediate between that of kerogen and generated petroleum. Moreover, the...
TL;DR: In this article, the effect of torrefaction severity on structure changes of hemicellulose, cellulose, lignin and their subsequent catalytic fast pyrolysis (CFP) behavior was performed in a tubular reactor with different reaction temperatures (210-300 °C) and residence times (20-60 min).
Abstract: To understand the effect of torrefaction severity on structure changes of hemicellulose, cellulose, lignin and their subsequent catalytic fast pyrolysis (CFP) behavior, torrefaction of lignin, hemicellulose, and cellulose was performed in a tubular reactor with different reaction temperatures (210–300 °C) and residence times (20–60 min). The experimental results show that the rank order of thermal stability during torrefaction was cellulose > lignin > hemicellulose. The torrefied hemicelulose, cellulose, and lignin were subsequently catalytic-fast-pyrolyzed over HZSM-5 in a semi-batch pyroprobe reactor. The effects of the torrefaction temperature and residence time on aromatic yields and selectivity from CFP of torrefied hemicellulose, cellulose, and lignin were investigated. The experimental results showed that torrefaction can cause the reduction in the aromatic yield and increase in benzene, toluene, and xylenes (BTX) selectivity from CFP of torrefied hemicellulose and lignin. It has little impact on C...
TL;DR: In this paper, the results of ES-MS, NMR, FTIR, and elemental analyses were used to construct average molecular representations of IAA and RA molecules, which were used in molecular dynamics (MD) simulation to study interfacially active subfraction of asphaltenes.
Abstract: After successful isolation of the most interfacially active subfraction of asphaltenes (IAAs) reported in the first part of this series of publications, comprehensive chemical analyses including ES-MS, elemental analysis, Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectrometry were used to determine how the molecular fingerprint features of IAAs are different from those of the remaining asphaltenes (RAs). Compared with the RAs, the IAA molecules were shown to have higher molecular weight and higher contents of heteroatoms (e.g., three times higher oxygen content). The analysis on the elemental content and FTIR spectroscopy suggested that IAAs contained higher contents of high-polarity sulfoxide groups than the RAs. The results of ES-MS, NMR, FTIR, and elemental analyses were used to construct average molecular representations of IAA and RA molecules. These structures were used in molecular dynamics (MD) simulation to study interfacial and aggregation behaviors of ...
TL;DR: In this article, the authors investigated the preferred orientation of a model asphaltene molecule at the oil-water interface (monomer) using dissipative particle dynamics (DPD).
Abstract: In the present work, we investigate, by means of theoretical simulation, the preferred orientation of a model asphaltene molecule at the oil–water interface (monomer). The coarse-grained model molecules at the mesoscale level, using dissipative particle dynamics (DPD), are adopted. The central polycyclic aromatic hydrocarbon (PAH) core and the peripheral alkanes in the asphaltene are considered. The asphaltene model construction by coarse grain mapping is proposed and analyzed, as well as the effect of using different solubility parameters in the construction of the potential interaction of the beads in the coarse grained asphaltene model. Also, the effect of surface coverage for a structure where steric effects dominate is presented as well as the effect of asphaltene coarse-grain nanoaggregates at the oil–water region. Finally, the orientation at the oil–water interface of an asphaltene with peripheral oxygen moieties is studied. Toluene is used as a model of oil. Three different orientations of the asp...
TL;DR: In this article, a modified Coats-Redfern method was used to study the decomposition kinetics of virgin and waste polypropylene (PP) and low-density polyethylene (LDPE).
Abstract: Study of the decomposition kinetics, pyrolysis products, and even reaction mechanisms plays an important role for the development of polymer recycling. In the present research, the kinetics of virgin and waste polypropylene (PP) and low-density polyethylene (LDPE) were studied by a modified Coats–Redfern method. Afterward, thermal cracking of them in a semibatch reactor under atmospheric pressure in nitrogen has been investigated. Both virgin and waste plastics are decomposed at 420–460 °C, and the products have been characterized using GC, FT-IR, 1H NMR, and GC-MS. The reaction path and the degradation mechanism for the thermal cracking of polymer in this study were also discussed. The lower activation energy of waste PP and LDPE indicates that waste plastics degrade at lower initial temperature and may favor mild conditions. Due to the short residence time, the higher gaseous and liquid yields were obtained for virgin PP and LDPE. A large amount of residues for waste polymer indicates that it is a favor...
TL;DR: Results show that the gelation behaviors of the gel system were greatly affected by the concentration of HAP and that of PEI, and the apparent viscosity of the HAP/PEI gel system in core was obviously reduced.
Abstract: A gel system has been widely used in many mature oilfields for water shut-off treatment. In the present study, the hydrophobically associating polymer (HAP) was cross-linked with the polyethylenimine (PEI) to form a HAP/PEI gel system which contains 0.35 wt % HAP and 0.60 wt % PEI. Gelation behaviors of the HAP/PEI gel formed in bottle and in core were studied, respectively. Results show that the gelation behaviors of the gel system were greatly affected by the concentration of HAP and that of PEI. The addition of the sodium chloride or calcium chloride generally resulted in a decrease of the apparent viscosity and an extension of the gelation time. However, a low concentration of sodium chloride led to a slight increase of the gel viscosity in bottle due to the intensification of the hydrophobic association. The rock skeleton of the core had a great effect on the gelation behavior. Compared with the results obtained in bottle, the apparent viscosity of the HAP/PEI gel system in core was obviously reduced...