Chemico-biological conversion of carbon dioxide

The unabated carbon dioxide(CO_(2))emission into the atmosphere has exacerbated global climate change,resulting in extreme weather events,biodiversity loss,and an intensified greenhouse effect.To address these challenges and work toward carbon(C)neutrality and reduced CO_(2)emissions,the capture and utilization of CO_(2)have become imperative in both scientific research and industry.One cutting-edge approach to achieving efficient catalytic performance involves integrating green bioconversion and chemical conversion.This innovative strategy offers several advantages,including environmental friendliness,high efficiency,and multi-selectivity.This study provides a comprehensive review of existing technical routes for carbon sequestration(CS)and introduces two novel CS pathways:the electrochemicalbiological hybrid and artificial photosynthesis systems.It also thoroughly examines the synthesis of valuable Cnproducts from the two CS systems employing different catalysts and biocatalysts.As both systems heavily rely on electron transfer,direct and mediated electron transfer has been discussed and summarized in detail.Additionally,this study explores the conditions suitable for different catalysts and assesses the strengths and weaknesses of biocatalysts.We also explored the biocompatibility of the electrode materials and developed novel materials.These materials were specifically engineered to combine with enzymes or microbial cells to solve the biocompatibility problem,while improving the electron transfer efficiency of both.Furthermore,this review summarizes the relevant systems developed in recent years for manufacturing different products,along with their respective production efficiencies,providing a solid database for development in this direction.The novel chemical-biological combination proposed herein holds great promise for the future conversion of CO_(2)into advanced organic compounds.Additionally,it offers exciting prospects for utilizing CO_(2)in synthesizing a wide range of industrial products.Ultimately,the present study provides a unique perspective for achieving the vital goals of“peak shaving”and C-neutrality,contributing significantly to our collective efforts to combat climate change and its associated challenges.

Effects of drip and flood irrigation on carbon dioxide exchange and crop growth in the maize ecosystem in the Hetao Irrigation District,China

Drip irrigation and flood irrigation are major irrigation methods for maize crops in the Hetao Irrigation District,Inner Mongolia Autonomous Region,China.This research delves into the effects of these irrigation methods on carbon dioxide(CO_(2))exchange and crop growth in this region.The experimental site was divided into drip and flood irrigation zones.The irrigation schedules of this study aligned with the local commonly used irrigation schedule.We employed a developed chamber system to measure the diurnal CO_(2)exchange of maize plants during various growth stages under both drip and flood irrigation methods.From May to September in 2020 and 2021,two sets of repeated experiments were conducted.In each experiment,a total of nine measurements of CO_(2)exchange were performed to obtain carbon exchange data at different growth stages of maize crop.During each CO_(2)exchange measurement event,CO_(2)flux data were collected every two hours over a day-long period to capture the diurnal variations in CO_(2)exchange.During each CO_(2)exchange measurement event,the biological parameters(aboveground biomass and crop growth rate)of maize and environmental parameters(including air humidity,air temperature,precipitation,soil water content,and photosynthetically active radiation)were measured.The results indicated a V-shaped trend in net ecosystem CO_(2)exchange in daytime,reducing slowly at night,while the net assimilation rate(net primary productivity)exhibited a contrasting trend.Notably,compared with flood irrigation,drip irrigation demonstrated significantly higher average daily soil CO_(2)emission and greater average daily CO_(2)absorption by maize plants.Consequently,within the maize ecosystem,drip irrigation appeared more conducive to absorbing atmospheric CO_(2).Furthermore,drip irrigation demonstrated a faster crop growth rate and increased aboveground biomass compared with flood irrigation.A strong linear relationship existed between leaf area index and light utilization efficiency,irrespective of the irrigation method.Notably,drip irrigation displayed superior light use efficiency compared with flood irrigation.The final yield results corroborated these findings,indicating that drip irrigation yielded higher harvest index and overall yield than flood irrigation.The results of this study provide a basis for the selection of optimal irrigation methods commonly used in the Hetao Irrigation District.This research also serves as a reference for future irrigation studies that consider measurements of both carbon emissions and yield simultaneously.

Carbon dioxide enrichment affected flower numbers transiently and increased successful post-pollination development stably but without altering final acorn production in mature pedunculate oak (Quercus robur L.)

Acorn production in oak(Quercus spp.)shows considerable inter-annual variation,known as masting,which provides a natural defence against seed predators but a highly-variable supply of acorns for uses such as in commercial tree planting each year.Anthropogenic emissions of greenhouse gases have been very widely reported to influence plant growth and seed or fruit size and quantity via the‘fertilisation effect’that leads to enhanced photosynthesis.To examine if acorn production in mature woodland communities will be affected by further increase in CO_(2),the contents of litter traps from a Free Air Carbon Enrichment(FACE)experiment in deciduous woodland in central England were analysed for numbers of flowers and acorns of pedunculate oak(Quercus robur L.)at different stages of development and their predation levels under ambient and elevated CO_(2) concentrations.Inter-annual variation in acorn numbers was considerable and cyclical between 2015 and 2021,with the greatest numbers of mature acorns in 2015,2017 and 2020 but almost none in 2018.The numbers of flowers,enlarged cups,immature acorns,empty acorn cups,and galls in the litter traps also varied amongst years;comparatively high numbers of enlarged cups were recorded in 2018,suggesting Q.robur at this site is a fruit maturation masting species(i.e.,the extent of abortion of pollinated flowers during acorn development affects mature acorn numbers greatly).Raising the atmospheric CO_(2) concentration by 150μL L^(−1),from early 2017,increased the numbers of immature acorns,and all acorn evidence(empty cups+immature acorns+mature acorns)detected in the litter traps compared to ambient controls by 2021,but did not consistently affect the numbers of flowers,enlarged cups,empty cups,or mature acorns.The number of flowers in the elevated CO_(2) plots’litter traps was greater in 2018 than 2017,one year after CO_(2) enrichment began,whereas numbers declined in ambient plots.Enrichment with CO_(2) also increased the number of oak knopper galls(Andricus quercuscalicis Burgsdorf).We conclude that elevated CO_(2) increased the occurrence of acorns developing from flowers,but the putative benefit to mature acorn numbers may have been hidden by excessive pre-and/or post-dispersal predation.There was no evidence that elevated CO_(2) altered masting behaviour.

CAS-ESM2.0 Dataset for the Carbon Dioxide Removal Model Intercomparison Project(CDRMIP)

Understanding the response of the Earth system to varying concentrations of carbon dioxide(CO_(2))is critical for projecting possible future climate change and for providing insight into mitigation and adaptation strategies in the near future.In this study,we generate a dataset by conducting an experiment involving carbon dioxide removal(CDR)—a potential way to suppress global warming—using the Chinese Academy of Sciences Earth System Model version 2.0(CASESM2.0).A preliminary evaluation is provided.The model is integrated from 200–340 years as a 1%yr^(−1) CO_(2) concentration increase experiment,and then to~478 years as a carbon dioxide removal experiment until CO_(2) returns to its original value.Finally,another 80 years is integrated in which CO_(2) is kept constant.Changes in the 2-m temperature,precipitation,sea surface temperature,ocean temperature,Atlantic meridional overturning circulation(AMOC),and sea surface height are all analyzed.In the ramp-up period,the global mean 2-m temperature and precipitation both increase while the AMOC weakens.Values of all the above variables change in the opposite direction in the ramp-down period,with a delayed peak relative to the CO_(2) peak.After CO_(2) returns to its original value,the global mean 2-m temperature is still~1 K higher than in the original state,and precipitation is~0.07 mm d^(–1) higher.At the end of the simulation,there is a~0.5°C increase in ocean temperature and a 1 Sv weakening of the AMOC.Our model simulation produces similar results to those of comparable experiments previously reported in the literature.

Simultaneous Degradation, Dehalogenation, and Detoxification of Halogenated Antibiotics by Carbon Dioxide Radical Anions

Despite the extensive application of advanced oxidation processes(AOPs)in water treatment,the efficiency of AOPs in eliminating various emerging contaminants such as halogenated antibiotics is constrained by a number of factors.Halogen moieties exhibit strong resistance to oxidative radicals,affecting the dehalogenation and detoxification efficiencies.To address these limitations of AOPs,advanced reduction processes(ARPs)have been proposed.Herein,a novel nucleophilic reductant—namely,the carbon dioxide radical anion(CO_(2)^(·-))—is introduced for the simultaneous degradation,dehalogenation,and detoxification of florfenicol(FF),a typical halogenated antibiotic.The results demonstrate that FF is completely eliminated by CO_(2)^(·-),with approximately 100%of Cland 46%of Freleased after 120 min of treatment.Simultaneous detoxification is observed,which exhibits a linear response to the release of free inorganic halogen ions(R^(2)=0.97,p<0.01).The formation of halogen-free products is the primary reason for the superior detoxification performance of this method,in comparison with conventional hydroxyl-radical-based AOPs.Products identification and density functional theory(DFT)calculations reveal the underlying dehalogenation mechanism,in which the chlorine moiety of FF is more susceptible than other moieties to nucleophilic attack by CO_(2)^(·-).Moreover,CO_(2)^(·-)-based ARPs exhibit superior dehalogenation efficiencies(>75%)in degrading a series of halogenated antibiotics,including chloramphenicol(CAP),thiamphenicol(THA),diclofenac(DLF),triclosan(TCS),and ciprofloxacin(CIP).The system shows high tolerance to the pH of the solution and the presence of natural water constituents,and demonstrates an excellent degradation performance in actual groundwater,indicating the strong application potential of CO_(2)^(·-)-based ARPs in real life.Overall,this study elucidates the feasibility of CO_(2)^(·-)for the simultaneous degradation,dehalogenation,and detoxification of halogenated antibiotics and provides a promising method for their regulation during water or wastewater treatment.

Experimental investigation on pyrolysis products and pore structure characteristics of organic-rich shale heated by supercritical carbon dioxide

The efficient pyrolysis and conversion of organic matter in organic-rich shale,as well as the effective recovery of pyrolysis shale oil and gas,play a vital role in alleviating energy pressure.The state of carbon dioxide(CO_(2))in the pyrolysis environment of shale reservoirs is the supercritical state.Its unique supercritical fluid properties not only effectively heat organic matter,displace pyrolysis products and change shale pore structure,but also achieve carbon storage to a certain extent.Shale samples were made into powder and three sizes of cores,and nitrogen(N_(2))and supercritical carbon dioxide(ScCO_(2))pyrolysis experiments were performed at different final pyrolysis temperatures.The properties and mineral characteristics of the pyrolysis products were studied based on gas chromatography analysis,Xray diffraction tests,and mass spectrometry analysis.Besides,the pore structure characteristics at different regions of cores before and after pyrolysis were analyzed using N_(2) adsorption tests to clarify the impact of fracturing degree on the pyrolysis effect.The results indicate that the optimal pyrolysis temperature of Longkou shale is about 430℃.Compared with N_(2),the oil yield of ScCO_(2) pyrolysis is higher.The pyrolysis oil obtained by ScCO_(2) extraction has more intermediate fractions and higher relative molecular weight.The ScCO_(2) can effectively improve the pore diameter of shale and its effect is better than that of N_(2).The micropores are produced in shale after pyrolysis,and the macropores only are generated in ScCO_(2) pyrolysis environments with temperatures greater than 430℃.The pore structure has different development characteristics at different pyrolysis temperatures,which are mainly affected by the pressure holding of volatile matter and products blocking.Compared to the surface of the core,the pore development effect inside the core is better.With the decrease in core size,the pore diameter,specific surface area,and pore volume of cores all increase after pyrolysis.

The AVO Effect of Formation Pressure on Time-Lapse Seismic Monitoring in Marine Carbon Dioxide Storage

The phase change of CO_(2) has a significant bearing on the siting, injection, and monitoring of storage. The phase state of CO_(2) is closely related to pressure. In the process of seismic exploration, the information of formation pressure can be response in the seismic data. Therefore, it is possible to monitor the formation pressure using time-lapse seismic method. Apart from formation pressure, the information of porosity and CO_(2) saturation can be reflected in the seismic data. Here, based on the actual situation of the work area, a rockphysical model is proposed to address the feasibility of time-lapse seismic monitoring during CO_(2) storage in the anisotropic formation. The model takes into account the formation pressure, variety minerals composition, fracture, fluid inhomogeneous distribution, and anisotropy caused by horizontal layering of rock layers(or oriented alignment of minerals). From the proposed rockphysical model and the well-logging, cores and geological data at the target layer, the variation of P-wave and S-wave velocity with formation pressure after CO_(2) injection is calculated. And so are the effects of porosity and CO_(2) saturation. Finally, from anisotropic exact reflection coefficient equation, the reflection coefficients under different formation pressures are calculated. It is proved that the reflection coefficient varies with pressure. Compared with CO_(2) saturation, the pressure has a greater effect on the reflection coefficient. Through the convolution model, the seismic record is calculated. The seismic record shows the difference with different formation pressure. At present, in the marine CO_(2) sequestration monitoring domain, there is no study involving the effect of formation pressure changes on seismic records in seafloor anisotropic formation. This study can provide a basis for the inversion of reservoir parameters in anisotropic seafloor CO_(2) reservoirs.

Solubility of iron(Ⅲ) and nickel(Ⅱ) acetylacetonates in supercritical carbon dioxide

As a common precursor for supercritical CO_(2)(scCO_(2))deposition techniques,solubility data of organometallic complexes in scCO_(2)is crucial for the preparation of nanocomposites.Recently,metal acetylacetonates have shown great potential for the preparation of single-atom catalytic materials.In this study,the solubilities of iron(Ⅲ)acetylacetonate(Fe(acac)3)and nickel(Ⅱ)acetylacetonate(Ni(acac)2)were measured at the temperature from 313.15 to 333.15 K and in the pressure range of 9.5–25.2 MPa to accumulate new solubility data.Solubility was measured using a static weight loss method.The semi-empirical models proposed by Chrastil and Sung et al.were used to correlate the solubility data of Fe(acac)3 and Ni(acac)2.The equations obtained can be used to predict the solubility of the same system in the experimental range.

Simulation Modelling and Techno-Economics of Supercritical Carbon Dioxide Recompression Closed Brayton Cycle

In recent years, there has been global interest in meeting targets relating to energy affordability and security while taking into account greenhouse gas emissions. This has heightened major interest in potential investigations into the use of supercritical carbon dioxide (sCO2) power cycles. Climate change mitigation is the ultimate driver for this increased interest;other relevant issues include the potential for high cycle efficiency and a circular economy. In this study, a 25 MWe recompression closed Brayton cycle (RCBC) has been assessed, and sCO2 has been proposed as the working fluid for the power plant. The methodology used in this research work comprises thermodynamic and techno-economic analysis for the prospective commercialization of this sCO2 power cycle. An evaluated estimation of capital expenditure, operational expenditure, and cost of electricity has been considered in this study. The ASPEN Plus simulation results have been compared with theoretical and mathematical calculations to assess the performance of the compressors, turbine, and heat exchangers. The results thus reveal that the cycle efficiency for this prospective sCO2 recompression closed Brayton cycle increases (39% - 53.6%) as the temperature progressively increases from 550˚C to 900˚C. Data from the Aspen simulation model was used to aid the cost function calculations to estimate the total capital investment cost of the plant. Also, the techno-economic results have shown less cost for purchasing equipment due to fewer components being required for the cycle configuration as compared to the conventional steam power plant.

Optimization of Supercritical Carbon dioxide Extraction of Ginger Essential Oil by Response Surface Method

[Objective] Ginger essential oil （GEO） is widely used in food production and medical field in recent years due to its prominent biological functions, and this study was conducted to obtain high-quality and high-purity ginger essential oil from the fresh ginger. [Method] GEO was extracted from ginger roots by supercritical fluid extraction （SFE） method. The effects of flow rate of CO2, mesh size of ginger powder and volume of entrainer were investigated by single-factor experiments and response surface method. The content and extraction rate of 6-gingerol represented the extraction index of GEO. [Result] The conditions were optimized as follows： flow rate of CO2 at 25 L/h, mesh size of ginger power of 80 mesh, and volume of anhydrous ethanol as entrainer of 92.46 ml. The optimal extraction rate of 6-gingerol was 3.21%, which was predicted by RSM. [Conclusion] The optimal process of supercritical carbon dioxide extraction of ginger essential oil was identified by singlefactor experiments and response surface method. The present study provides a satisfactory method for purifying GEO from ginger for industrial purpose.

Vapor-Liquid Equilibrium Data of Carbon Dioxide＋Methyl Propionate and Carbon Dioxide＋Propyl Propionate Systems

High-pressure vapor-liquid equilibrium data for the binary systems of methyl propionate＋carbon dioxide and propyl propionate＋carbon dioxide were measured at pressure from 1.00 MPa to 12.00 MPa and temperature in the range from 313 K to 373 K. Experimental results were correlated with the Peng-Robinson equation of state with the two-parameter van der Waals mixing rule. At the same time, the Henry＇s coefficient, partial molar enthalpy change and partial molar entropy change of CO2 during dissolution at different temperature were also calculated.

Extraction of Perilla Seed Oil Using Supercritical Carbon Dioxide and GC-MS Analysis

[Objective] This study was aimed to determine the optimal parameters for the extraction of perilla seed oil to obtain high-quality perilla seed oil and analyze its compositions. [Method] In this study, perilla seed oil was extracted using supercritical CO2 （SC-CO2）. The effects of extraction time, temperature and pressure were investigated by single-factor experiments and orthogonal array testing （ORT）. The chemical compositions of extracted perilla seed oil were investigated by GC-MS. [Result] The optimal conditions for the extraction of perilla seed oil using SC-CO2 were extraction time of 4 h, extraction temperature at 40 ℃, and extraction pressure at 23 MPa. Under these conditions, the extraction yield of perilla seed oil was maximized to 12.43%. GC-MS analysis revealed that perilla seed oil was a complex mixture containing 76.183% α-linolenic acid. [Conclusion] Supercritical CO2 extraction was proven to be an effective technology to extract oil from perilla seed, and GCMS was also a satisfactory method for analyzing the compositions of perilla seed oil.

Progress in carbon dioxide separation and capture: A review

This article reviews the progress made in CO2 separation and capture research and engineering. Various technologies, such as absorption, adsorption, and membrane separation, are thoroughly discussed. New concepts such as chemical-looping combustion and hydrate-based separation are also introduced briefly. Future directions are suggested. Sequestration methods, such as forestation, ocean fertilization and mineral carbonation techniques are also covered. Underground injection and direct ocean dump are not covered.

Killing Effect of Mixed Fumigation of Phosphine and Carbon Dioxide on Eggs of Lasioderma serricorne F.

[Objective] This study aimed to investigate the killing effect of mixed fumi- gation of phosphine and carbon dioxide on eggs of Lasioderma serricorne F. [Method] The outside-storage phosphine generator was placed in a tabernacled smoke box, and the mortality rates of L. serricome F. eggs in the smoke box under conditions of different aluminium phosphide usage amount and different fumigation time were studied. In addition, the times needed by tabernacle and smoke box cen- ter to reach the phosphine concentration peak were recorded. [Result] The optimum conditions for killing the eggs of L. serricorne were as follows： temperature of （27± 2） ℃, relatively humidity of （45±5）%, aluminium phosphide usage amount of 1.5 g/m3 and effective exposure time of 96 h. The killing effect of mixed fumigation of phos- phine and carbon dioxide was increased with the extension of fumigation time. The increased usage amount of aluminium phosphide showed no significant effect on killing effect. The tabernacle space and smoke box center all required relatively short time to reach the phosphine concentration peak. If the tabernacle had a good airtightness, the overall fumigation time could be shortened. [Conclusion] The fumi- gation method is reliable, and it can be used for the control of L. serricorne F. in tobacco storage.

Syngas Production by Methane Reforming with Carbon Dioxide on Noble Metal Catalysts

A series of noble metal catalysts （Ru, Rh, Ir, Pt, and Pd） supported on alumina-stabilized magnesia （Spinel） were used to produce syngas by methane reforming with carbon dioxide. The synthesized catalysts were characterized using BET, TPR, TPO, TPH, and H2S chemisorption techniques. The activity results showed high activity and stability for the Ru and Rh catalysts. The TPO and TPH analyses indicated that the main reason for lower activity and stability of the Pd catalyst was the formation of the less reactive deposited carbon and sintering of the catalyst.

Regeneration of 2-amino-2-methyl-1-propanol used for carbon dioxide absorption

To improve the efficiency of the carbon dioxide cycling process and to reduce the regeneration energy consumption, a sterically hindered amine of 2-amino-2-methyl-1- propranol （AMP） was investigated to determine its regeneration behavior as a CO2 absorbent. The CO2 absorption and amine regeneration characteristics were experimentally examined under various operating conditions. The regeneration efficiency increased from 86.2% to 98.3% during the temperature range of 358 to 403 K. The most suitable regeneration temperature for AMP was 383 K, in this experiment condition, and the regeneration efficiency of absorption/regeneration runs descended from 98.3% to 94.0%. A number of heat-stable salts （HSS） could cause a reduction in CO2 absorption capacity and regeneration efficiency. The results indicated that aqueous AMP was easier to regenerate with less loss of absorption capacity than other amines, such as, monoethanolamine （MEA）, diethanolamine （DEA）, diethylenetriamine （DETA）, and N-methyldiethanolamine （MDEA）.

Preparation of calcium carbonate particles coated with titanium dioxide

The preparation of a new mineral composite material, calcium carbonate particles coated with titanium dioxide, was studied. The mechanism of the preparation process was proposed. The new mineral composite material was made by the mechanoehemieal method under the optimum condition that the mass ratio of calcium carbonate particles to titanium dioxide was 6.5：3.5. The mass ratios of two different types of titanium dioxide （anatase to rutile） and grinding media to grinded materials were 8：2 and 4：1 respectively, and the modified density was 60%. Under this condition, the new material was capable of forming after 120-min modification. The hiding power and oil absorption of this new material were 29.12 g/m^2 and 23.30%, respectively. The results show that the modification is based on surface hydroxylation. After coating with titanium dioxide, the hiding power of calcium carbonate can be improved greatly. The new mineral composite materials can be used as the substitute for titanium dioxide.

Extraction of methane hydrate energy by carbon dioxide injection-key challenges and a paradigm shift

Significant effort including field work has been devoted to develop a natural gas extraction technology from natural gas hydrate reservoirs through the injection of carbon dioxide. Natural gas hydrate is practically methane hydrate. The hypothesis is that carbon dioxide will be stored as hydrate owing to its favorable stability conditions compared to methane hydrate. Although the dynamics of the CO2/CH4 exchange process are not entirely understood it is established that the exchange process is feasible. The extent is limited but even if the CH4 recovery is optimized there is a need for a CH4/CO2 separation plant to enable a complete cyclic sequence of CO2 capture, injection and CH4 recovery. In this paper we propose an alternative paradigm to the Inject(CO2)/Exchange with(CH4)/Recover(CH4) one namely Recover(CH4) first and then Inject(CO2) for Storage.

Effect of CeO_2 addition on Ni/Al_2O_3 catalysts for methanation of carbon dioxide with hydrogen

The Ni-CeO2/Al2O3 catalysts with a nickel content of 15 wt% prepared via impregnating boehmite were found to be highly active and stable for methanation of carbon dioxide with hydrogen at a H2/CO2 molar ratio of 4. The effects of CeO2 content and reaction temperature on the performance of the Ni-CeO2/Al2O3 catalysts were studied in detail. The results showed that the catalytic performance was strongly dependent on the CeO2 content in Ni-CeO2/Al2O3 catalysts and that the catalysts with 2 wt% CeO2 had the highest catalytic activity among the tested ones at 350 ℃. The XRD and H2-TPR characterizations revealed that the addition of CeO2 decreased the reduction temperature by altering the interaction between Ni and Al2O3, and improved the reducibility of the catalyst. Preliminary stability test of 120 h on stream over the Ni-2CeO2/Al2O3 catalyst at 350 ℃ revealed that the catalyst was much better than the unpromoted one.

A study of the mechanism of enhancing oil recovery using supercritical carbon dioxide microemulsions

Supercritical carbon dioxide （scCO2） microemulsion was formed by supercritical CO2, H20, sodium bis（2-ethylhexyl） sulfosuccinate （AOT, surfactant） and C2HsOH （co-surfactant） under pressures higher than 8 MPa at 45 ℃. The fundamental characteristics of the scCO2 microemulsion and the minimum miscibility pressure （MMP） with Daqing oil were investigated with a high-pressure falling sphere viscometer, a high-pressure interfacial tension meter, a PVT cell and a slim tube test. The mechanism of the scCO2 microemulsion for enhancing oil recovery is discussed. The results showed that the viscosity and density of the scCO2 microemulsion were higher than those of the scCO2 fluid at the same pressure and temperature. The results of interfacial tension and slim tube tests indicated that the MMP of the scCO2 microemulsion and crude oil was lower than that of the scCO2 and crude oil at 45 ℃. It is the combined action of viscosity, density and MMP which made the oil recovery efficiency of the scCO2 microemulsion higher than that of the scCO2 fluid.