Effect Of Supercritical CO Research Articles

Effects of Supercritical CO2 on the Pore Structure Complexity of High-Rank Coal with Water Participation and the Implications for CO2 ECBM.

To reveal how mineral changes affect a coal pore structure in the presence of water, an autoclave was used to carry out the supercritical CO2 (ScCO2)-H2O-coal interaction process. To reveal the changes in pore complexity, mercury intrusion capillary pressure (MICP), low-pressure nitrogen adsorption, CO2 adsorption, and field emission scanning electron microscopy (FESEM) experiments were combined with fractal theory. The experimental data of MICP show that the MICP data are meaningful only for the pore fractal dimension with pore sizes >150 nm. Therefore, the pores were classified into the classes >150, 2-150, and <2 nm. The results show that the pore volume and specific surface area of the coal increased significantly after the reaction. ScCO2-H2O can cause the formation of many new pores and fractures in the coal. The presence of H2O may increase the potential for the injection of CO2 into the coal seam. The complete dissolution of calcite surfaces caused a significant increase in the pore volume and specific surface area of the pores >150 nm. The morphologies of these pores are controlled by the morphologies of the complete dissolution carbonate particles. The pore morphologies were relatively uniform, and the fractal dimensions decreased. However, the incomplete dissolution of calcite leads to irregular variations in the morphologies for the pores in the 2-150 nm pore size range. The pore morphologies that are produced by incompletely dissolved calcite particles are more complex, which increases the fractal dimensions after the reaction. The fractal dimensions of the pores <2 nm decreased after the reaction, indicating that the newly generated micropores were more uniform and had regular pore morphologies.

Effects of Supercritical CO2 Injection on the Shale Pore Structures and Mass Transport Rates

Characterizing the pore structures and transport properties of low-permeability shales is critical for evaluating these formations as potential seals or storage sites for geological CO2 sequestration. Here, we use low-pressure gas adsorption in conjunction with nuclear magnetic resonance (NMR) to characterize the pore-size distribution of shales before and after injection of supercritical CO2. Nitrogen gas was used as the detecting phase for the adsorption experiments and pentane liquid was used for the NMR experiments. We also performed time-resolved NMR and gravimetric microbalance measurements to observe mass transport during desaturation. We use these data to estimate the self-diffusion coefficient of pentane and changes in the saturation state of the pore network. We analyzed samples with a range of compositions from the Wolfcamp shale before and after exposure to supercritical CO2 for 3 days. Integrating the gas adsorption and NMR data shows how supercritical CO2 injection alters the pore-size distribution for pore sizes <1 nm to 1 mm. Our results provide insights on how the pore structure and mass transport properties of different shale lithologies may evolve during storage of supercritical CO2.

Pore-Scale Experimental Investigation of the Effect of Supercritical CO2 Injection Rate and Surface Wettability on Salt Precipitation

Injectivity is one of the most important factors to evaluate the feasibility of CO2 geological storage. Salt precipitation due to the mass of dry CO2 injected into a saline reservoir may cause a significant decrease in injectivity. However, the coupling effect of injection parameters and reservoir conditions on salt precipitation is not clear. Here, we conducted pore-scale visualization experiments to study the morphology and distribution of salt precipitation in porous structures and their effects on permeability reduction. The experimental results are achieved by controlling the supercritical CO2 injection rate and the surface wettability at the reservoir temperature and pressure. It is found that for hydrophilic and neutral porous surfaces, ex situ precipitation occurs and blocks the entirety of pore throats and bodies, which results in a significant reduction in permeability. Increasing the CO2 injection rate can suppress the capillary reflow and prevent the permeability reduction. For a hydrophobic porous surface, in situ precipitation occurs and occupies much smaller pore volume, which has a slight effect on permeability reduction compared to the hydrophilic samples at the same injection rate. Increasing the CO2 injection rate and dewetting the injection well and formation nearby reduce the possibility of salt accumulation, which has less effect on CO2 injectivity.

Synergistic effect of supercritical CO2 and organic solvent on exfoliation of graphene: experiment and atomistic simulation studies

In this work, experiments and molecular dynamics (MD) simulations are carried out to explore the synergistic effect of supercritical CO2 (scCO2) and organic solvent on intercalation and exfoliation of graphene. Experimental characterizations via transmission electron microscopy, atomic force microscopy and Raman spectroscopy indicate that by combining scCO2 and organic solvent (N-methylpyrrolidone, NMP), few-layer graphene is successfully exfoliated from graphite, among which over 30% is 1-4 layers, and 55% is 5-8 layers. Systematic experiments have shown that compared with pure scCO2 or NMP, the mixed scCO2 and NMP can significantly increase the amount of graphene and the rate of few-layer graphene, and the optimum volume fraction of NMP is 25%. Parallel MD simulations indicate that the scCO2 molecules first diffuse into the interlayer of graphite, and then the larger NMP molecules insert as wedges and further expand interlayer spacing, promoting intercalation and exfoliation. The iteration of scCO2 diffusion and the NMP wedge can generate positive feedback to improve the exfoliation productivity and efficiency. This work explores the synergistic effect of scCO2 and NMP on the exfoliation of graphene, which may provide useful insights for exfoliation of other two dimensional materials.

Coupling Effects of Supercritical CO2 Sequestration in Deep Coal Seam

CO2 sequestration in deep unminable coal seams is currently identified as a research hot spot to reduce CO2 emissions, due to the potential large-scale storage capacity and complicated physical and chemical reactions, especially for supercritical CO2 (scCO2). Hitherto, the interaction mechanisms between scCO2 and coal mass in situ conditions are still unclear. Therefore, the main objective of this study is to fully address the coupling effects of scCO2 sequestration on coal mass and provide a comprehensive evaluation of the interrelation of these variations. Five cycles of helium and scCO2 injection were replicated on a subbituminous coal sample to investigate the permeability variation with scCO2 saturation time. Meanwhile, gas chromatography–mass spectrometry (GC–MS), gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), proximate analysis, and low-pressure–temperature nitrogen (N2) isotherm analyses were employed to characterize the transformation in coal mass. The test result shows ...

Effect of Supercritical CO2 as Reaction Medium for Selective Hydrogenation of Acetophenone to 1-Phenylethanol.

1-Phenylethanol (PhE) is widely employed in the pharmaceutical industry as an anti-inflammatory and analgesic drug, as well as in chewing gums and yogurts as a food additive. In this work, we have investigated the selective synthesis of 1-phenylethanol (PhE) by hydrogenation of acetophenone using supercritical CO2 as a solvent. Supercritical carbon dioxide (scCO2) replaces organic solvent because it is inexpensive, nontoxic, nonflammable, inert, and environmentally benign. Polyurea-based encapsulated mono- and bimetallic catalysts were synthesized and characterized using different characterization techniques. The effects of various reaction parameters, such as co-solvent, catalyst loading, hydrogen pressure, total scCO2 pressure, and temperature, were studied to determine the reaction kinetics.

Effects of Supercritical CO2 Treatment on the Stability of Water-in-Heavy-Oil Emulsion and Their Mechanisms

With the gradual popularization and application of CO2 flooding technology in oilfields, the physical properties of produced fluid, including the stability of the emulsion formed by crude oil and produced water, may be changed, consequently influencing the surface gathering and dewatering processes. In order to investigate the stability changes of heavy oil emulsions and their mechanisms after supercritical CO2 (scCO2) flooding, a device that could simulate the scCO2 treatment condition in the oil reservoir was first designed and used to pretreat the heavy oil. Then, the effects of scCO2 treatment on the stability of heavy oil emulsion were investigated by means of a bottle test and microscopic observation. The results revealed that the stability of the emulsion formed by scCO2-treated degassed heavy oil was improved. The reason for the stability improvement was then deeply explored from two aspects, i.e., the bulk viscosity and the structural strength of the water–oil interface. On the one hand, it was f...

Effect of supercritical CO&lt;sub align="right"&gt;2 on various rank coals: implications for CO&lt;sub align="right"&gt;2 sequestration in coal seams with enhanced coalbed methane recovery

Effect of supercritical CO&lt;sub align="right"&gt;2 on various rank coals: implications for CO&lt;sub align="right"&gt;2 sequestration in coal seams with enhanced coalbed methane recovery

Effects of Supercritical CO2 Fluids on Pore Morphology of Coal: Implications for CO2 Geological Sequestration

A systematic knowledge of the pore morphology of coal treated with supercritical CO2 (ScCO2) is critical for the process of CO2 geological sequestration. To better understand the desorption mechanism and to evaluate the storage capacity of target coal seams, the changes in pore volume, pore size distribution, fractal dimension, pore shape, and connectivity in high-, middle-, and low-rank coals were analyzed using N2/CO2 adsorption and mercury intrusion porosimetry. The results indicate that micropores of high- and middle-rank coals decreased after ScCO2 treatment, whereas an increasing trend was found in low-rank coals, and ScCO2 promoted the accessibility of the macropore spaces for all coals. With ScCO2 treatment, the roughness of smaller pores in both high- and middle-rank coals decreased, whereas larger pores became more complex for high-rank coals. Although no significant change was observed in the pore shapes, ScCO2 facilitated the development of effective pore spaces and improved the connectivity o...

Effect of supercritical CO2 on the copolymerization behavior of cyclohexene oxide/CO2 and copolymer properties with DMC/Salen‐Co(III) catalyst system

ABSTRACTThe copolymerization of cyclohexene oxide (CHO) and carbon dioxide (CO2) was carried out under supercritical CO2 (scCO2) conditions to afford poly (cyclohexene carbonate) (PCHC) in high yield. The scCO2 provided not only the C1 feedstock but also proved to be a very efficient solvent and processing aid for this copolymerization system. Double metal cyanide (DMC) and salen‐Co(III) catalysts were employed, demonstrating excellent CO2/CHO copolymerization with high yield and high selectivity. Surprisingly, our use of scCO2 was found to significantly enhance the copolymerization efficiency and the quality of the final polymer product. Thermally stable and high molecular weight (MW) copolymers were successfully obtained. Optimization led to excellent catalyst yield (656 wt/wt, polymer/catalyst) and selectivity (over 96% toward polycarbonate) that were significantly beyond what could be achieved in conventional solvents. Moreover, detailed thermal analyses demonstrated that the PCHC copolymer produced in scCO2 exhibited higher glass transition temperatures (Tg ∼ 114 °C) compared to polymer formed in dense phase CO2 (Tg ∼ 77 °C), and hence good thermal stability. Additionally, residual catalyst could be removed from the final polymer using scCO2, pointing toward a green method that avoids the use of conventional volatile organic‐based solvents for both synthesis and work‐up. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2785–2793

Effect of supercritical CO2 on carbonates: Savonnières sample case study

ABSTRACTCO2 geosequestration is an efficient way to reduce greenhouse gas emissions into the atmosphere. Carbonate rock formations are one of the possible targets for CO2 sequestration due to their relative abundance and ability to serve as a natural trapping reservoir. The injected supercritical CO2 can change properties of the reservoir rocks such as porosity, permeability, tortuosity, and specific surface area due to dissolution and precipitation processes. This, in turn, affects the reservoir characteristics, i.e., their elastic properties, storage capacity, stability, etc.The tremendous progresses made recently in both microcomputed X‐ray tomography and high‐performance computing make numerical simulation of physical processes on actual rock microstructures feasible. However, carbonate rocks with their extremely complex microstructure and the presence of microporosity that is below the resolution of microcomputed X‐ray tomography scanners require novel, quite specific image processing and numerical simulation approaches.In the current work, we studied the effects of supercritical CO2 injection on microstructure and elastic properties of a Savonnières limestone. We used microtomographic images of two Savonnières samples, i.e., one in its natural state and one after injection and residence of supercritical CO2. A statistical analysis of the microtomographic images showed that the injection of supercritical CO2 led to an increase in porosity and changes of the microstructure, i.e., increase of the average volume of individual pores and decrease in the total number of pores. The CO2 injection/residence also led to an increase in the mean radii of pore throats, an increase in the length of pore network segments, and made the orientation distribution of mesopores more isotropic. Numerical simulations showed that elastic moduli for the sample subjected to supercritical CO2 injection/residence are lower than those for the intact sample.

Therapeutic Effect of Supercritical CO2 Extracts of Curcuma Species with Cancer Drugs in Rhabdomyosarcoma Cell Lines.

Synergistic effect of supercritical CO2 extracts of Curcuma species with conventional chemotherapeutic drugs was investigated in human alveolar (SJRH30) and embryonal (RD) rhabdomyosarcoma cell lines. The Curcuma amada (mango ginger) (CA) extract showed the highest levels of cytotoxicity with inhibitory concentration IC50 values of 7.133 µg/ml and 7.501 µg/ml for SJRH30 and RD cell lines, respectively, as compared with Curcuma longa (turmeric) and Curcuma xanthorrhiza (Javanese turmeric) extracts. CA showed synergistic cytotoxic effects with vinblastine (VBL) and cyclophosphamide (CP) as indicated by the combination index values of <1 for VBL + CA, CP + CA, and VBL + CP + CA combinations in both embryonal and alveolar rhabdomyosarcomas. When lower doses of CA (0.1-0.2 µg/ml) were combined with cancer drugs like CP and VBL, caspase-3 activity increased significantly compared with individual agents and correlated with the percentage of apoptotic cells. CA in combination with VBL and CP induced a higher percentage of apoptosis than single agents in both cell lines. CA also modulated the expression of genes associated with intrinsic pathway of apoptosis (Bcl-2, Bax, Bak, and p53) and also inhibited the expression of genes associated with inflammation such as COX-2 and NF-κB. Xenograft studies with SJRH30 tumors in nude mice showed that CA treatment inhibited tumor growth rate with and without VBL and increased the survival rate significantly. These results suggest that CA can be evaluated further as an adjuvant with cancer drugs for the treatment of rhabdomyosarcoma patients. Copyright © 2015 John Wiley & Sons, Ltd.

MODIFIKASI WARNA, TEKTUR DAN AROMA TEMPE SETELAH DIPROSES DENGAN KARBON DIOKSIDA SUPERKRITIK [The Modification of Color, Texture, and Aroma of Tempe Processed with Supercritical Carbon Dioxide

Supercritical carbon dioxide technology was a non thermal processing which might be applied on tempe to preserve its freshness. The aim of the research was to study the effect of supercritical CO 2 on the color and texture of tempe, and to identify the aroma of tempe after processed with supercritical CO 2 . The experiment was carried out using CompletelyRandomized Block Design with three replications. The experimental factors were pressure treatmentat supercritic (Ps) and liquid (Pc), and treatment time (T) at T 1 , T 2 , T 3 , T 4 of 5, 10, 15, and 20 minutes, respectively. The results showed that the treatment of pressures, time and their interactions significantly affected the color of ∆L*, ∆a*, ∆b*, ∆E*, but not significantly affected the textures.The best treatment was PcT 1 producing the tempe with the value of ∆L*-2.13; ∆a*0.28; ∆b*0.97 dan ∆E*0.77 . Several volatile aromas of tempe were extracted due to the supercritical CO 2 treatment, but it also caused the formation of new volatile aroma compounds.

Effect of supercritical CO2plasticization on the degradation and residual crystallinity of melt-extruded spironolactone

Immediate-release solid dispersions of a slowly dissolving active pharmaceutical ingredient, spironolactone, were prepared by supercritical-CO2-assisted melt extrusion (a solvent-free and continuous manufacturing technology) using Eudragit E as matrix. Through optimizing process parameters (i.e. temperature, melt throughput, pressure and CO2 flow), stable foams with high porosity, homogeneous structure and thin (even submicronic) walls could be prepared, as revealed by scanning electron microscopy. The samples were found to be rigid enough to mill, enabling further processing, as is necessary to formulate tablets. The influence of extrusion temperature and melt throughput on residual drug crystallinity was measured using non-invasive confocal Raman mapping coupled with chemometric analysis, while the influence on the degree of drug degradation was determined using high performance liquid chromatography. The plasticizing effect of supercritical CO2 was shown to reasonably improve the purity of the prepared solid dispersions by enabling high-yield production at lower temperature ranges. At the same time, shorter residence time and lower temperature slightly increased residual drug crystallinity. The obtained foamy structures ensured immediate drug dissolution in an acidic medium. Copyright © 2014 John Wiley & Sons, Ltd.

The influence of water and supercritical CO2 on the failure behavior of chalk

Abstract Reduction of compressive strength by injection of water into chalk is a well-known mechanism responsible for increased compaction in chalk reservoirs. This raises the question of whether such effects might be enhanced in the context of long-term storage of CO 2 or of CO 2 injection for enhanced oil and gas recovery (EOR/EGR) purposes. Therefore, data regarding the effect of supercritical CO 2 on the mechanical behavior of chalk are needed. The effect of supercritical CO 2 on the short-term failure behavior of wet chalk was accordingly investigated by means of conventional triaxial deformation experiments, performed on Maastrichtian chalk cores under dry conditions, in the presence of saturated chalk solution and using CO 2 -saturated solution at temperatures simulating reservoir conditions (20–80 °C) and effective confining pressures up to 7 MPa. Increasing temperature from 20 to 80 °C did not show any significant effects on the strength of the dry samples. Addition of aqueous solution to the samples led to drastic weakening of the chalk, the effect being more pronounced at high effective confining pressures (Peff > 3 MPa). Addition of 10 MPa supercritical CO 2 to wet samples did not produce any significant additional effect in comparison with the wet samples. All samples showed a yield strength envelope characterized by shear failure at low effective mean stresses giving way to a compaction cap at high mean stresses. The weakening effect of aqueous solution was explained in terms of a reduction in frictional resistance of the material, due to water-enhanced grain-contact cracking, and perhaps pressure solution, with a possible contribution by disjoining pressure effects caused by water adsorption. While CO 2 does not seem to reduce short-term failure strength of wet chalk, processes such as intergranular pressure solution have to be considered for assessing mechanical stability of chalk in the context of long-term CO 2 storage or EOR/EGR operations.

Research on Permeability of Coal Samples with and without the Effect of Supercritical CO&lt;sub&gt;2&lt;/sub&gt;

To improve the low-permeability coal seam gas drainage and gas prevention and to seek the methods to improve the permeability of low-permeability coal, the experimental study on supercritical CO2 on coal was conducted in the laboratory conditions, and the experiment on pseudo-triaxial permeability testing for coal samples, with and without supercritical CO2, was conducted. The results show that due to the effect of supercritical CO2 on coal like physi-chemistry, the porosity of coal was changed, which markedly varied the permeability of coal samples before and after the effect of supercritical CO2; the permeability of the experimented coal samples was significantly higher than before, and average permeability increased by nearly an order of magnitude under the same volume-stress.

Research on Permeability of Coal Samples with and without the Effect of Supercritical CO&lt;sub&gt;2&lt;/sub&gt;

To improve the low-permeability coal seam gas drainage and gas prevention and to seek the methods to improve the permeability of low-permeability coal, the experimental study on supercritical CO2 on coal was conducted in the laboratory conditions, and the experiment on pseudo-triaxial permeability testing for coal samples, with and without supercritical CO2, was conducted. The results show that due to the effect of supercritical CO2 on coal like physi-chemistry, the porosity of coal was changed, which markedly varied the permeability of coal samples before and after the effect of supercritical CO2; the permeability of the experimented coal samples was significantly higher than before, and average permeability increased by nearly an order of magnitude under the same volume-stress.

Effect of supercritical CO 2 flux, temperature and processing time on physicochemical and morphological properties of commercial reverse osmosis membranes

Coupling supercritical CO 2 (SC-CO 2) extraction with membrane separation leads to energy savings by recycling CO 2 at supercritical state while separating extract components. However, high pressure operating conditions may cause physicochemical and morphological changes in polymer membranes, which in turn can adversely affect membrane performance. In this study, the effect of different flux (50 and 200 kg/m 2 h), temperature (40 and 80 °C) and time (0–8 h) levels were investigated at 120 bar on two commercial reverse osmosis membranes, AK and SG using contact angle, ATR-FTIR and FE-SEM measurements. Contact angle of AK increased substantially with high flux and high temperature processing unlike SG. The peaks assigned to N–H and carbonyl groups at 1541, 1609 and 1663 cm −1 showed the highest decrease in absorbance with high flux processing while high temperature was more effective on O–H groups between 2700 and 3700 cm −1. AK membrane exhibited the formation of bead-like structures at different processing times and conditions. The effect of SC-CO 2 processing on the membranes varied depending on their chemical structure, which is important to understand for further process development.

Chitosan templated synthesis of porous metal oxide microspheres with filamentary nanostructures

This work describes a versatile strategy for fabricating highly porous and nanofibrous titania, zirconia, alumina and tin oxide. Taking advantage from chitosan polysaccharide microspheres as nano-assembling system during sol–gel mineralization of monomeric alkoxides and the beneficial effect of supercritical CO 2 drying to avoid the collapse of the transient hybrid material network, all targeted metal oxides were created, after calcinations, as fibrous filaments featuring dual meso- and macro-porous network with surface areas ranging from 110 to 310 m 2g −1. Chitosan alcogels were found to be the best mould for this replication alleviating the problems associated with the rapid kinetic growth encountered with hydrogels and those of diffusion limitations in dried aerogels. From mechanistic point of view, amino-metal coordination NH 2 → M (M = Ti, Zr, Al, Sn) and hydrogen bonding between hydroxyl group and oligomeric metal oxide play a pivotal role during the mineralization process.

Effect of supercritical CO2 on three‐dimensional colloid arrays of PS‐MA–EGDMA

AbstractUsing emulsifier‐free emulsion polymerization method, monodispersed crosslinked poly(styrene‐co‐methacrylic acid‐co‐ethylene glycol dimethacrylate) colloid microspheres were synthesized. The microspheres were treated in supercritical carbon dioxide (SCCO2) after they have self‐assembled into ordered three‐dimensional (3D) colloid arrays. The CO2 absorbed into the polymer microspheres enhances chain segments mobility and reduces the glass transition temperature (Tg) of polymer, which induce the microspheres coalesce at the relatively low temperature. The coalescence degree of microspheres was studied by varying the experimental temperature, pressure, and exposure time in SCCO2. The results were shown by scanning electron microscopy (SEM). Further, the lattice spacing of the assembled 3D colloid microspheres was calculated from the SEM images. It was illustrated that the coalescence degree enhanced with the increase of CO2 pressure; however, this tendency became weak when CO2 pressure reached a certain value. Extending exposure time in SCCO2 or elevating temperature can also increase coalescence degree, and the effect of temperature is more significant. It is believed that these results will make sense when the polymer microspheres are considered to be used as templates in SCCO2; meanwhile, it raises a new method about tuning the final morphology of the stabilized colloidal crystals and porous materials via controlling the coalescence degree with the assistance of SCCO2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011