Large Amounts Of CO2 Research Articles

Structure dependence of the enhanced sulfur tolerance of core–shell CoMn oxides for benzene oxidation: Discrepant sulfur species and less affected reactant activation

Effective reduction of VOCs emissions in practical gas requires low-temperature catalysts with remarkable SO2 tolerance. Here via simply mixing CoCO3 into the precursors of α-MnO2, a core–shell CoMn composite was developed. The leading one with CoCO3 addition of 3 g (Co3Mn) achieved 100 % C6H6-to-CO2 conversion at ≥250 °C under 120 L/g/h, and still the CO2 yield over the sulfurized Co3Mn (simulated by H2SO3 vapor pretreatment) was maintained 100 %. However, with respect to the case of fresh MnO2, the CO2 production at 250 and 300 °C over the sulfurized MnO2 was decreased by 26 % and 8 %, respectively, and in the meantime, a larger amount of CO was detected. The dominant formation of abundant MnSO4 species due to sulfur poisoning led to the deactivation of pure MnO2, while over Co3Mn the formation of MnSO4 was significantly inhibited because of (i) the electron transfer from Co2+ to Mn4+ restraining that from S4+ to Mn4+ and (ii) the stronger alkalinity of Co species making the acidic H2SO3 preferentially anchor on Co as CoSO4. Along with the sacrificial role, another way cobalt alleviated sulfate toxicity was through transiting the aggregated sulfate deposition into scattered state. Investigations conducted primarily with UV–vis DRS and temperature-programmed techniques further reveal that neither MnO2 nor Co3Mn could escape from the sulfur-induced adversity on activation of O2 and benzene, but the sulfurized Co3Mn was much less affected, thus sustaining the deep benzene oxidation. Finally, reaction routes were unraveled according to the phenol, benzoquinone, maleic acid and acetic acid intermediates.

Sustainable Processing of Ultralow-Cost Petroleum Cokes Into Ultrastable Self-Doped Fe3C@CNT Catalysts for High-Efficiency HER.

Petroleum cokes are largely used as low-cost anodes in aluminum industries and general fuels in cement industries, where large amounts of CO2 are generated. To reduce CO2 release, it is challenging to develop green strategies for processing abundant petroleum cokes into high-value products, because there are abundant hetero-atoms in petroleum cokes. To overcome such issues, a sustainable electrochemical approach is proposed to convert ultralow-cost high sulfur petroleum coke and iron powders into high-efficiency catalysts for hydrogen evolution reaction (HER). During molten-salt electrolysis, raw petroleum cokes are converted into CNTs via heteroatom removal and the catalytic effect of Fe, forming Fe3C nanoparticles on the sulfur and nitrogen co-dopped carbon nanotubes (Fe3C@S, N-CNTs). The electrochemical reaction analysis using the continuum model suggested that the rate-determining step referred to the slow transport of mobile ions inside the porous cathode. Because the self-doped S and N atoms massively alleviated the energy barrier for H* absorption and H2 desorption (i.e., promoting HER kinetics), the as-prepared Fe3C@S, N-CNTs exhibited low overpotentials at 10mAcm-2 in acidic (96mV) and alkaline (106mV) solutions with ultralong-term duration (200h). This study offers a sustainable approach to convert ultralow-cost petroleum cokes into ultrastable catalysts for high-efficiency HER.

Multiple-Win Effects and Beneficial Implications from Analyzing Long-Term Variations of Carbon Exchange in a Subtropical Coniferous Plantation in China

To improve our understanding of the carbon balance, it is significant to study long-term variations of all components of carbon exchange and their driving factors. Gross primary production (GPP), respiration (Re), and net ecosystem productivity (NEP) from the hourly to the annual sums in a subtropical coniferous forest in China during 2003–2017 were calculated using empirical models developed previously in terms of PAR (photosynthetically active radiation), and meteorological parameters, GPP, Re, and NEP were calculated. The calculated GPP, Re, and NEP were in reasonable agreement with the observations, and their seasonal and interannual variations were well reproduced. The model-estimated annual sums of GPP and Re over 2003–2017 were larger than the observations of 11.38% and 5.52%, respectively, and the model-simulated NEP was lower by 34.99%. The GPP, Re, and NEP showed clear interannual variations, and both the calculated and the observed annual sums of GPPs increased on average by 1.04% and 0.93%, respectively, while the Re values increased by 4.57% and 1.06% between 2003 and 2017. The calculated and the observed annual sums of NEPs/NEEs (net ecosystem exchange) decreased/increased by 1.04%/0.93%, respectively, which exhibited an increase of the carbon sink at the experimental site. During the period 2003–2017, the annual averages of PAR and the air temperature decreased by 0.28% and 0.02%, respectively, while the annual average water vapor pressure increased by 0.87%. The increase in water vapor contributed to the increases of GPP, Re, and NEE in 2003–2017. Good linear and non-linear relationships were found between the monthly calculated GPP and the satellite solar-induced fluorescence (SIF) and then applied to compute GPP with relative biases of annual sums of GPP of 5.20% and 4.88%, respectively. Large amounts of CO2 were produced in a clean atmosphere, indicating a clean atmospheric environment will enhance CO2 storage in plants, i.e., clean atmosphere is beneficial to human health and carbon sink, as well as slowing down climate warming.

Applying the internet of things (IoT) for raising black soldier Fly (BSF) in closed system to minimize greenhouse gas emissions

The Black Soldier Fly (BSF), scientifically known as Hermetia Illucens L., effectively reduces organic waste and decreases harmful gas emissions more efficiently than landfill or composting methods. However, it can still produce harmful gases during the rearing of BSF larvae, including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ammonia (NH3), which contribute directly and indirectly to the greenhouse effect. The pH level of the food provided to the larvae affects their biomass and leads to varying levels of gas emissions. This study aims to investigate the impact of greenhouse gas emissions when different pH levels of food are used, utilizing IoT technology to measure greenhouse gases and control the environmental conditions for rearing BSF larvae. The greenhouse gases monitored in this study include carbon dioxide (CO2) and methane (CH4), with environmental factors such as air temperature, humidity, soil moisture, and light intensity being controlled. The experiment tested pH levels ranging from 2.0, 4.0, 6.0, 7.0, and 8.0 to 10.0. The results show that different pH levels in food affect the emission of CO2 and CH4. Initially, a large amount of CO2 is released, gradually decreasing over time, while CH4 emissions steadily increase. In the early days, CH4 emissions are unstable, fluctuating before stabilizing. Food with a pH of 2.0 results in the lowest average CO2 emissions (430.53 PPM) from BSF larvae, and the lowest CH4 emissions (16.11 PPM) are also observed with a pH of 2.0.

Methylotuvimicrobium alcaliphilum 20Z based ectoine production from various industrial CH4 sources: Cultivation optimization and comprehensive analysis

Methanotroph-based CH4 conversion technology is being widely studied due to its advantages of mild operating conditions and environmental friendliness. In this study, operating strategies were investigated for industrial CH4 sources in order to widely disseminate methanotroph-based CH4 conversion technology using the promising strain, Methylotuvimicrobium alcaliphilum 20Z. The optimal O2/CH4 ratio for extremely different CH4 concentrations was explored based on kinetic-based simulation for biological reaction, and experimentally proven using fermenter-scale experiments. As a result, when high CH4 concentration is used, ectoine production rate can be maximized (33.8 mg/L·h) at an O2/CH4 ratio of 1 while favoring the “production of metabolites”. On the other hand, in the low CH4 concentration case, when changing from the general O2/CH4 ratio of 4 to the optimal O2/CH4 ratio (i.e., 1), although the improvement in ectoine concentration was not noticeable (3.9 to 7.5 mg/L·h), the CH4 conversion rate rapidly decreased (50 to 20 %), suggesting that the focus in the low concentration case should be on “removal of CH4”. In the case of biogas, the rapid pH drop caused by the large amount of CO2 in the feed is offset by a buffer solution, and the concentration of Na+ ions increases during the overall reaction time. Therefore, the production of metaboiltes can be maximized while simultaneously controlling pH and Na+ ion through continuous operation with a high dilution rate (19.8 mg/L·h). Furthermore, major performance indicators for each industrial gas were derived through comprehensive comparative analysis, through which the “dual-functions” of methanotrophs could be emphasized. This study provides a practical and strategic approach for methanotrophs that can flexibly respond to diverse industrial CH4 sources.

Feasibility of CO2 storage and enhanced gas recovery in depleted tight sandstone gas reservoirs within multi-stage fracturing horizontal wells

Injecting CO2 when the gas reservoir of tight sandstone is depleted can achieve the dual purposes of greenhouse gas storage and enhanced gas recovery (CS-EGR). To evaluate the feasibility of CO2 injection to enhance gas recovery and understand the production mechanism, a numerical simulation model of CS-EGR in multi-stage fracturing horizontal wells is established. The behavior of gas production and CO2 sequestration is then analyzed through numerical simulation, and the impact of fracture parameters on production performance is examined. Simulation results show that the production rate increases significantly and a large amount of CO2 is stored in the reservoir, proving the technical potential. However, hydraulic fractures accelerate CO2 breakthrough, resulting in lower gas recovery and lower CO2 storage than in gas reservoirs without fracturing. Increasing the length of hydraulic fractures can significantly increase CH4 production, but CO2 breakthrough will advance. Staggered and spaced perforation of hydraulic fractures in injection wells and production wells changes the fluid flow path, which can delay CO2 breakthrough and benefit production efficiency. The fracture network of massive hydraulic fracturing has a positive effect on the CS-EGR. As a result, CH4 production, gas recovery, and CO2 storage increase with the increase in stimulated reservoir volume.

Effect of ball milling activation on CO2 mineralization performance in fly ash and fire resistance capabilities of mineralized product

Coal-fired power generation has always been a major energy supply source globally. However, a large amount of CO2 is emitted with the combustion of coal resources, and fly ash, a by-product of coal combustion, is also accumulated in large quantities. The application of CO2 mineralization in fly ash can not only reduce CO2 emission but also effectively manage industrial waste, thereby promoting environmental sustainability. This paper used the mechanical ball milling method to activate fly ash and investigated the effects of ball milling time and speed on the CO2 sequestration in fly ash. At 30 min ball milling time and 400 r/min ball milling speed, the modified fly ash achieves a good CO2 sequestration capacity of 81.70 gCO2/kgFA. Compared with raw fly ash, the CO2 consumption of treated fly ash is higher at 75.41 mmol/mL. The specific surface area and pore volume of treated fly ash are larger at 1.57 m2/g and 4.33 cm3/kg respectively, which is beneficial for enhancing mass transfer capacity and the carbonation effect. As the ratio of mineralized product/coal increases from 0.5 to 4, the crossing-point temperature increases from 157.20 °C to 165.15 °C. Based on the experimental results, the paper discussed the mechanism of ball milling activation to enhance the carbonation effect of fly ash. This study provides theoretical references for the environmentally friendly utilization of fly ash.

Sustainable conversion of agricultural waste into solid fuel (Charcoal) via gasification and pyrolysis treatment

Managing agricultural waste by burning it in the fields is a straightforward method, but leads to significant pollution. One promising alternative is to convert agricultural waste into solid fuel, such as charcoal, to support renewable energy from biomass. The quality of barbecue charcoal depends upon selecting suitable materials and employing heating methods to ensure efficient transformation. This research aims to study the charcoal conversion process from agricultural waste using two types of kilns: 1) direct heating (gasification kiln: GK) and 2) indirect heating (pyrolysis kiln: PK) designed to recirculate syngas from wood as fuel for the pyrolysis process. The study tested three types of agricultural waste materials, including coconut shells (CS), cassava rhizome (CR), and acacia wood (AW), to examine the differences in charcoal produced by the two heating methods. The tests revealed that the maximum temperatures inside the kilns were 792.45 ± 127.18 °C, 907.67 ± 37.3 °C, and 980.07 ± 110.56 °C for the GK, and 921.88 ± 57.84 °C, 801.93 ± 10.16 °C, and 937.82 ± 95.85 °C for the PK. The charcoal from the PK exhibited higher calorific values than the GK, with 7474.68 ± 36.62, 6429.04 ± 72.22, and 7268.33 ± 52.86 calories per gram. The charcoal yield was also higher in the PK, at 31.29 ± 4.39, 34.33 ± 3.39, and 17.58 ± 2.09 percent for coconut shells charcoal (CSC), cassava rhizome charcoal (CRC), and acacia wood charcoal (AWC), respectively. However, the PK required more fuel and longer ignition times. The resulting charcoal from the slow pyrolysis process in the PK is suitable as barbecue fuel due to its size, which is similar to the original material. In contrast, the charcoal from the GK, which tends to shrink or break into smaller pieces, is more suitable for grinding into briquettes. This study provides a guideline for producing high-quality barbecue charcoal, offering commercial benefits including the gasification and pyrolysis processes that improve combustion efficiency and reduce pollution by producing high-quality gas for fuel, unlike traditional kilns that emit a large amount of CO during the conversion of wood to charcoal and enabling the selection of appropriate raw materials for different heating methods to maximise the utility of the products. This approach adds value to agricultural raw materials and helps effectively manage agricultural waste (zero waste) for further utilisation and development.

Large-Scale Experimental Investigation of Hydrate-Based Carbon Dioxide Sequestration

Hydrate-based CO2 sequestration is a novel approach that can not only realize permanent CO2 sequestration but can also form an artificial cap to prevent its upward migration. In this work, a self-developed large-scale 3D apparatus was employed to investigate hydrate formation characteristics in hydrate-based CO2 sequestration at a constant liquid CO2 injection rate through a vertical well for the first time. Temperature and pressure evolutions in the sediment were analyzed in detail. Key indicators, including cumulative sequestered CO2, CO2 in hydrate and liquid phases, the instantaneous hydrate conversion, and liquid CO2 retention rates, were calculated. The results show that hydrate continuously forms with increased CO2 injection and exhibits strong heterogeneity due to the variation in hydrate formation rate and quantity. Severe liquid CO2 heterogeneous figuring phenomena occur since hydrate deteriorates the effective pore structure and topology, resulting in relatively small cumulative sequestered CO2 when a large amount of CO2 is released from the outlet. Meanwhile, the instantaneous hydrate conversion and liquid CO2 retention rates have large fluctuations owing to water consumption and variation in the effective contact area between liquid CO2 and water. However, hydrate formation does not cause blockage of wellbore and formation nearby under given experimental conditions, which is beneficial for hydrate formation in deeper sediment. This study provides insights into hydrate formation and liquid CO2 immigration regularity during hydrate-based CO2 sequestration and demonstrates its feasibility at a field scale.

Effect of high temperature on mechanical properties of lithium slag concrete

As the main gel material of concrete, cement is used in an astonishing amount every year in the construction industry. However, a large amount of CO2 is emitted into the atmosphere while producing cement. Therefore, it is the general trend to look for substitutes for cement and develop new green concrete. Lithium slag (LS) is the industrial waste discharged from lithium salt plants. Through testing, it is found that the chemical composition of LS has a high degree of coincidence with ordinary Portland cement (OPC) Therefore, LS can be incorporated into concrete as supplementary cementations material (SCM) to prepare lithium slag concrete (LSC). The pollution of the natural environment caused by a large number of piled-up and landfilled LS is immeasurable. Consuming and using LS in large quantities and with high efficiency not only eliminates the pollution of lithium slag to the natural environment, but also helps to reduce the amount of cement used in green concrete and truly reuse waste resources. In order to study the mechanical properties of post-heated LSC, the test were carried out for LSC specimens after high-temperature. The main influence factors were considered, including the temperatures of 20℃, 100 ℃, 300 ℃, 500 ℃ and 700 ℃, the contents of lithium slag in LSC of 0%, 10%, 20% and 30%, cooling method of LSC after exposure high temperature. The results showed that the mechanical properties of LS concrete specimens were slightly improved at 100 ℃, and when the temperature was 300 ℃ or higher, the damage to the specimens was huge and irreversible. An appropriate amount of LS (20% lithium slag content) could improve the strength of LSC. This paper also studied the relationship between lithium slag content and strengths of LS concrete. The research results show that adding an appropriate amount of LS to concrete improves the mechanical properties of concrete. When the LS replacement rate is 20%, the mass loss rate of LSC after different high temperature treatments was the minimum. The cubic compressive strength, axial compressive strength, and flexural strength of specimens with 20% LS substitution can be increased by 8.16%, 8.33%, and 13.46% after high temperature. The cubic compressive strength, axial compressive strength, and flexural strength of specimens with 20% LS substitution can be increased by 8.16%, 8.33%, and 13.46% after high temperature.

Pressure-assisted vacuum filtration fabrication of polymer membranes with enhanced selectivity for the separation of an ethanol/carbon dioxide mixture

The membrane performance and effectiveness of fabrication are significant factors that determine the industrialization of membranes. In this study, a pressure-assisted vacuum filtration method was proposed to fabricate a sub-100 nm thin composite membrane using a homemade polyamide for the separation of an ethanol/carbon dioxide (CO2) mixture. Because during bioethanol fermentation, a large amount of CO2 can be produced, forming fermentation tail gas with vaporized ethanol, which should be separated to recover ethanol and reduce greenhouse CO2 emissions. The fabrication conditions, including the size of the polymer coil and feed pressure, were investigated in detail. Characterization using a dynamic laser scatterometer and low-field nuclear magnetic resonance (NMR) was conducted to reveal the membrane properties. The membrane performance obtained by the pressure-assisted vacuum filtration method was compared with that obtained by the solution casting method, which was demonstrated to be 40 % higher. Meanwhile, when a smaller pore size of the substrate was used, a 56 nm thick composite membrane was obtained with an ethanol/CO2 selectivity of 18 and an ethanol permeance of approximately 35000 GPU (1960 Barrer). Finally, the effects of the operating parameters, such as the feed concentration and stability, on the membrane performance were investigated. This study provides a valuable reference for the fabrication of ultrathin polymer membranes.

Corrosion behaviors of Inconel 617 and Incoloy 800H in impure helium with different CO contents at high temperatures

The helium coolant of the very high-temperature gas-cooled reactor (VHTR) is expected to contain trace impurities, which will cause corrosion to superalloys at high temperatures. The high-temperature corrosion behaviors of Inconel 617 and Incoloy 800H were investigated in the impure helium with various CO levels. For Inconel 617, the microclimate reaction occurred at high temperatures, releasing large amounts of CO and destroying the oxide layer. The corrosion model was established according to the chemical thermodynamics theory, showing that the reaction temperature is related to the CO content. However, this corrosion behavior was not observed for Incoloy 800H. The corrosion difference between these alloys was analyzed in this study, indicating that the silicon oxide interlayer of Incoloy 800H may inhibit the microclimate reaction. Although the interlayer could attenuate the chemical destruction of the oxide layer, the adhesion may be reduced leading to thermal damage, which was proved by the experiment in this study. This research clarified the different corrosion mechanisms of these two alloys and provided guidance for the control scheme of CO content in the primary circuit of HTGR.

CO2 capture and hydrogen generation from a solar-assisted and integrated fluid catalytic cracking process: Energy, exergy, and economic analysis

The fluid catalytic cracking (FCC) process transforms heavy wastes into lighter, more valuable (naphtha, light olefins and gases) products. However, the unit's byproducts contain a large quantity of CO2, which contributes to global warming. As a result, the purpose of this research was to increase the production of valuable products such as light olefins, naphtha, and hydrogen while reducing environmental impacts using the water gas shift reaction, with sensitivity analysis for three parameters (riser height, FCC feed temperature, and inlet naphtha mass flow). As a result of increasing the riser height, the output of light olefins (45%) and gases (32%) increased. Furthermore, the amount of hydrogen produced increases with a decrease in riser height (about 6%) and an increase in inlet naphtha mass flow (about 8%). Energy and exergy assessments were also carried out. It was determined that FCC had the lowest exergy destruction with a contribution of 23 MW when compared to its energy usage of 172 MW. The cooler, on the other hand, was one of the process's most energy-consuming (25%) and damaging (26%). As a result, this technique can lessen environmental effects by absorbing 125 tons of CO2 every hour and producing 3484 kg/h of hydrogen. Economic evaluations were also undertaken, and the results revealed that the cooler has the lowest exergoeconomic factor (1%) while the FCC unit contributes the most (95%). The fractionator column is also the most expensive device in the whole process.

Numerical Simulation Study of Hydrogen Blending Combustion in Swirl Pulverized Coal Burner

Hydrogen blending of pulverized coal in boilers is a promising technology. However, there are few studies on hydrogen blending in coal-fired boilers. In order to reduce CO2 emissions from coal-fired boilers, this study investigates the co-combustion of pulverized coal and hydrogen in a swirl pulverized coal burner by numerical simulation. Itis shown that the burnout rate of fuel is 5.08% higher than that of non-hydrogen blended coal when the percentage of hydrogen blended is 5%. The water vapor generated by hydrogen blending not only leads to the formation of a low-temperature zone near the burner outlet; it also results in a prolonged burnout time of moist pulverized coal and a high-temperature zone near the furnace outlet. The greater the amount of hydrogen for blending, the higher the water produced. When 1–3% hydrogen is blended, the water vapor in the furnace reacts with the carbon to produce a large amount of CO. When the amount of hydrogen added to the furnace is more than 3%, the water content in the furnace rises, resulting in a lower temperature at the burner outlet and a decrease in the amount of CO produced. When 1–3% hydrogen is blended, the CO2 emission rises. The CO2 emission decreased by 1.49% for 5% hydrogen blending compared to non-hydrogen blending and by 3.22% compared to 1% hydrogen blending.

(Invited) Electrochemical CO2 Reduction to Chemical Feedstocks: System Capacity and Specifications for Carbon Neutrality

The transition of an energy system that realizes net-zero CO2 emission requires both energy saving and electrification of energy demands, coupled with the use of CO2-free fuel such as hydrogen and synthetic hydrocarbons derived from captured CO2. In addition, carbon feedstocks for chemical products must originate from biomass, recycled plastics, and captured carbon from both factory effluent and air. In this regard, the electrochemical reduction of CO2 to chemical feedstocks is a promising and indispensable technology for the realization of carbon neutrality.To secure the social implementation of this technology, it is important to quantify the amount of CO2 that needs to be processed by a back-casting approach from an entire picture of a carbon-neutral energy system. Furthermore, the electricity input for CO2 reduction must be counted in reference to the total electricity demand of the energy system. The improvement in the energy efficiency of CO2 reduction is of crucial importance because the large amount of CO2 that needs to be processed may require electricity that exceeds the total electricity demand for direct use. When the CO2 footprint on electricity is not zero, the intensive use of electricity for CO2 reduction will result in the system with positive CO2 emission: the amount of CO2 converted into chemical feedstocks will be smaller than the emitted CO2 upon the generation of electricity which is necessary for electrochemical reduction.Therefore, it is significant to think about the role of electrochemical CO2 reduction from the viewpoint of the energy transition scenario towards net-zero CO2 emission and to analyze the process in terms of life-cycle assessment (LCA). In this presentation, we will focus on the net-zero energy scenario in Japan as an example and will quantify the amount of CO2 that needs to be either sequestered or, more hopefully, converted to chemical feedstocks. Our scenario analysis indicates that the electricity demand in Japan that realizes net-zero CO2 emission will be ca. 1500 TWh, which is ca. 1.5 times larger than the existing value due to the electrification of the existing fossil fuel usage. The amount of CO2 emission will be 84 million tons, which is ca. 8 % of the existing value. As an ideal case, the total amount, 84 million tons of CO2, is assumed to be converted to ethylene by electrochemical reduction rather than being sequestered into the ground. Then, ca. 700 TWh of electricity is required in addition to the electricity demand for direct use, 1500 TWh. The electricity demand for CO2 electrochemical reduction depends on system specifications. Here, the operation voltage of 3 V is assumed.The LCA of a CO2 electrochemical reduction system clarifies the specifications for negative CO2 emission from the system, which is a prerequisite of CO2 recycling. The life-cycle CO2 emission is dependent on the system configuration, and we found that CO2 recycling from a CO2 electrolysis reactor is of crucial importance for the realization of negative CO2 emission. With such a configuration, the most impactful factors on the CO2 balance (fixation versus emission) are the operation voltage and the Faradaic efficiency of CO2 reduction. For negative CO2 emission, they must be below 4 V and above 50%, respectively, assuming the CO2 footprint of electricity as 32 g/kWh corresponding to the existing level for renewable electricity. For 1.5 tons of CO2 fixation upon 1 ton of ethylene production, they must be below 3 V and above 80%, respectively. This analysis highlights the importance of setting targets for research and development from the viewpoint of LCA.

Machine Learning-Based Qualitative Identification of Four-Phase Fluid in Reservoir.

The identification of fluid types has always been the focus of oil and gas field exploration and development research. At this stage, a large amount of CO2 has been found in many basins during exploration and development, which greatly affects the accuracy of reservoir understanding and evaluation, so it is very important to accurately identify the fluid type of the CO2-bearing reservoirs. However, methods utilizing multiple logging data are greatly affected by physical changes in the formation, resulting in methods that are only applicable to the area and layer under study, are poorly generalized, and require multiple instruments and experimental support. Existing nuclear logging methods that primarily utilize logging curve stacking and intersection map methods fail to take full advantage of logging. In this study, taking advantage of the fact that the neutron gamma technique of nuclear logging measurement can provide multiparameter information with the characteristics of machine learning to deal with multidimensional data, comparing the classification results of different ware learning methods under different classification strategies and selecting a method of identifying fluids in logging while drilling was based on the idea of dichotomy and the use of the support vector machine as a meta-model. This solved the problem of identifying fluids in the CO2-bearing reservoirs, providing new ideas for the design and fabrication of logging instruments. These instruments can assist with the exploration and development of oil and gas fields and has a broad application prospect in CO2-EOR and CCUS.

Synthesis, characterization, and CO2 adsorption performance of UiO-66-(OH)2/GO composite

The flue gas produced by fossil fuel combustion contains a large amount of CO2, and the greenhouse effect caused by CO2 emissions is becoming increasingly serious. There is an urgent need to develop adsorbents with excellent CO2 adsorption performance. In this study, a new composite graphene oxide (GO) -metal-organic framework (MOF) (UiO-66-(OH)2/GO) was synthesized using UiO-66-(OH)2 as a precursor. Structural analysis of the parent materials and composites found that pore structures and Brunauer–Emmett–Teller (BET) surface area could be adjusted by adding GO, and GO was tested as a carbon dioxide adsorbent at 273 K and 298 K. The maximum CO2 adsorption of the composites was 5.03 mmol/g and 4.34 mmol/g, which was 36.7% and 36.9% higher than that of the parent materials at 1 bar, respectively. Dynamic breakthrough experiments were used to study the CO2/N2 separation capability of the composites. The stability of composites was studied by chemical stability experiments and several adsorption/desorption experiments. The results showed that the composites had good acid resistance and cycle stability. The separation performance of CO2/N2 in the presence of water vapor was investigated, and the composites showed good water stability. Therefore, UiO-66-(OH)2/GO has latent applications in CO2 capture technology to mitigate global warming.

Experimental Study on CO2 Geochemical Reaction Characteristics in Marine Weakly Consolidated Sandstone Saline Aquifers

Geological storage is one of the most important measures to reduce carbon emissions. The newly developed oilfield A in the Pearl River Mouth Basin of the South China Sea is associated with a large amount of CO2 with a purity of up to 95%. Two weakly consolidated sandstone saline aquifers located above the oil reservoir can be used for CO2 storage, but the CO2 geochemical reaction characteristics in the aquifers should be investigated clearly, which may cause significant damage to the physical properties of the reservoirs and caprocks of the aquifers. In this paper, static CO2 geochemical reaction experiments and rock thin section identifications were carried out using drill cuttings and sidewall cores, respectively. A numerical simulation was conducted according to the reactor conditions to explore the equilibrium state of the CO2 geochemical reaction. Through these studies, the characteristics of the geochemical reaction, its impact on the physical properties of the formation, and the CO2 storage potential by mineral trapping in the target aquifers were revealed. The results show that the two saline aquifers have similar physical properties. The reservoirs are mostly made up of fine-to-medium-grained sandstones as quartz arenite with a considerable amount of feldspar, which can provide favorable pore space for CO2 storage, while the caprocks are fine-grained felsic sedimentary rocks that can have a good sealing effect. However, both the reservoirs and caprocks contain a certain amount of carbonate and clay minerals. Mineral dissolution dominates in the CO2 geochemical reaction process, and more Ca2+ and Mg2+ is released into the formation water. The theoretical maximum CO2 mineral trapping capacity in the aquifers is 0.023–0.0538 mol/100 g rock, but due to the dynamic equilibrium of the geochemical reaction, the amount of mineralized CO2 in most of the rock samples is negative, and the average utilization factor is only −55.43%. As a result, the contribution of mineral trapping to the CO2 storage capacity takes −0.32%, which can be ignored. In the future, it is necessary to conduct detailed research to reveal the effect of a CO2 geochemical reaction on storage safety, especially in offshore weakly consolidated sandstone saline aquifers, which could be important sites for large-scale CO2 storage in China.

Study on acoustic properties of hydrate-bearing sediments with reconstructed CO2 hydrate in different layers during CH4 hydrate mining

Natural gas hydrate (NGH), a clean energy source with huge reserves in nature, and its safe and efficient exploitation fits perfectly with the UN Sustainable Development Goals (SDG-7). However, large-scale NGH decomposition frequently results in subsea landslides, reservoir subsidence, and collapse. In this work, in order to achieve safe and efficient exploitation of NGHs, the stability variation of different reservoir layers by depressurization/intermittent CO2/N2 injection (80:20 mol%, 50:50 mol%) was investigated using acoustic properties (P-wave velocity, elastic modulus), as well as reservoir subsidence under an overburden stress of 10 MPa. The P-wave velocity increased from 1282 m/s to 2778 m/s in the above-reservoir and from 1266 m/s to 2564 m/s in the below-reservoir, significantly increasing reservoir strength after CO2 hydrate formation. The P-wave velocity and elastic modulus in the top reconstructed reservoir were continually decreased by the shear damage of the overlying stress, while they remained stable in the bottom reconstructed reservoir during hydrate mining. However, due to superior pressure-bearing ability of the top CO2 hydrate reservoir, which was lacking in the bottom CO2 hydrate reservoir, the reservoir subsidence was relieved greatly. Despite the stiffness strength of reconstructed reservoir was ensured with CO2/N2 sweeping, the skeletal structure of CH4 hydrate reservoir was destroyed, and only the formation of CO2 hydrate could guarantee the stability of P-wave velocity and elastic modulus which was most beneficial to relieve reservoir subsidence. A large amount of CO2 was used in reservoir reconstruction and CH4 hydrate mining, which achieved the geological storage of CO2 (SDG-13). This work provided a new idea for safe and efficient NGHs mining in the future, and the application of acoustic properties served as a guide for the efficient construction of reconstructed reservoirs and offers credible technical assistance for safe exploitation of NGHs.

Mechanical energy-driven triboelectric plasma catalytic CO2 reduction over oxygen-vacancy-introduced In2O3 nanoparticles

As the single electron transfer of CO2 to CO2− ions is the critical step in the CO2 activation, it is very important to develop appropriate strategies to construct efficient catalytic systems. Herein, we constructed a coupled catalytic system consisting of mechanical-energy-driven triboelectric plasma and indium oxide rich in oxygen vacancies to achieve CO2 reduction to CO at room temperature and atmospheric pressure. At the discharge distance of 0.6 mm, the indium oxide with more oxygen vacancies exhibited an optimal catalytic activity of 0.20 mmol·g−1·h−1 for CO evolution rate, and the conversion efficiency from electrical to chemical energy was 10.8 %. Electron paramagnetic resonance experiments showed that a large amount of CO2− ions were generated in the triboelectric plasma. The introduction of oxygen vacancies could increase the density of states near the Fermi level of indium oxide catalysts, stabilize highly active CO2− ions, and reduce the energy barrier of CO2− decomposition.