Main observation and conclusion By a strategy of fine-tuning of packing mode between the adjacent layers in a 2D net metal-organic frameworks(MOFs)through ligand changing,two 2D sql-type MOFs with highly selective CO_...Main observation and conclusion By a strategy of fine-tuning of packing mode between the adjacent layers in a 2D net metal-organic frameworks(MOFs)through ligand changing,two 2D sql-type MOFs with highly selective CO_(2)uptake,CuHIN and CuHPB,were successfully synthesized.Compared with the precursor MOF-2,the fine-tuning structure of CuHIN shows selective adsorption of CO_(2)over N_(2)and CH_(4)with the CO_(2)uptake amounts as high as 4.7 wt%at 0.15 bar and at 298 K,and CO_(2)selectivity towards N_(2)and CH_(4)is 165.8 and 10.22 at 1 bar and at 298 K,respectively.In addition,for the 2D MOFs,the dynamic porous structure depends on the interaction of the adjacent layers.The suitable interaction is good for gliding smoothly and gas adsorption.展开更多
There are more and more researches on heat transfer characteristics and prediction of supercritical CO_(2).The method of adding adiabatic section before and after heating section is usually adopted in these researches...There are more and more researches on heat transfer characteristics and prediction of supercritical CO_(2).The method of adding adiabatic section before and after heating section is usually adopted in these researches to ensure that the fluid entering the heating section is no longer affected by boundary layer,but the appropriate length range of adiabatic section and the influence of entrance effect are not discussed.However,some studies show that the entrance effect would affect the heat transfer in mini tubes.This paper uses the commercial CFD code FLUENT 19.0 to numerically study the heat transfer of supercritical CO_(2) in a mini tube under different working conditions(such as Re_(in),P_(in),q_(w) and flow direction)and the lengths of the adiabatic section(l_(as)/d).The entrance effects on heat transfer is more pronounced when Re_(in) is within the transition state and wall heat flux is relatively high,the resulting heat transfer deterioration causes T_(w,x) and h_(w,x) to rise sharply.As the adiabatic section increases,the location at which the heat exchange deteriorates moves to the entrance of the heating section and eventually leaves.The buoyancy effect and flow acceleration effect caused by the sharp change of physical properties are analyzed,and the dimensionless velocity distribution at the inlet of the heating section in different adiabatic sections is compared.It is proved that the entrance effect has an influence on the convection heat transfer of supercritical CO_(2) in mini tubes.The interaction reflected by wall shear stress between boundary layer development and drastic changes in physical properties is the cause of heat transfer deterioration.展开更多
CO_(2) drilling is a promising underbalance drilling technology with great advantages,such as lower cutting force,intense cooling and excellent lubrication.However,in the underbalance drilling,the mechanism of the cou...CO_(2) drilling is a promising underbalance drilling technology with great advantages,such as lower cutting force,intense cooling and excellent lubrication.However,in the underbalance drilling,the mechanism of the coupling CO_(2) jet and polycrystalline-diamond-compact(PDC)cutter are still unclear.Whereby,we established a coupled smoothed particle hydrodynamics/finite element method(SPH/FEM)model to simulate the composite rock-breaking of high-pressure CO_(2) jet&PDC cutter.Combined with the experimental research results,the mechanism of composite rock-breaking is studied from the perspectives of rock stress field,cutting force and jet field.The results show that the composite rock-breaking can effectively relieve the influence of vibration and shock on PDC cutter.Meanwhile,the high-pressure CO_(2) jet has a positive effect on carrying rock debris,which can effectively reduce the temperature rising and the thermal wear of the PDC cutter.In addition,the effects of CO_(2) jet parameters on composite rock-breaking were studied,such as jet impact velocity,nozzle diameter,jet injection angle and impact distance.The studies show that when the impact velocity of the CO_(2) jet is greater than 250 m/s,the CO_(2) jet could quickly break the rock.It is found that the optimal range of nozzle diameter is 1.5–2.5 mm,the best injection angle of CO_(2) jet is 60,the optimal impact distance is 10 times the nozzle diameter.The above studies could provide theoretical supports and technical guidance for composite rock-breaking,which is useful for the CO_(2) underbalance drilling and drill bit design.展开更多
Rechargeable lithium-carbon dioxide(Li-CO_(2))batteries have attracted much attention due to their high theoretical energy densities and capture of C0_(2).However,the electrochemical reaction mechanisms of rechargeabl...Rechargeable lithium-carbon dioxide(Li-CO_(2))batteries have attracted much attention due to their high theoretical energy densities and capture of C0_(2).However,the electrochemical reaction mechanisms of rechargeable Lo-CO_(2) batteries,particularly the decomposition mechanisms of the discharge product Li_(2)CO_(3) are still unclear,impeding their practical applications.Exploring electrochemistry of Li_(2)CO_(3) is critical for improving the performance of Li-C0_(2) batteries.Herein,in-situ environmental transmission electron microscopy(ETEM)technique was used to study electrochemistry of Li_(2)CO_(3) in Li-C0_(2) batteries during discharge and charge processes.During discharge,Li_(2)CO_(3) was nucleated and accumulated on the surface of the cathode media such as carbon nanotubes(CNTs)and Ag nanowires(Ag NWs),but it was hard to decompose during charging at room temperature.To promote the decomposition of Li2C03,the charge reactions were conducted at high temperatures,during which Li_(2)CO_(3) was decomposed to lithium with release of gases.Density functional theory(DFT)calculations revealed that the synergistic effect of temperature and biasing facilitates the decomposition of Li_(2)CO_(3).This study not only provides a fundamental understanding to the high temperature Li-C0_(2) nanobatteries,but also offers a valid technique,i.e.,discharging/charging at high temperatures,to improve the cyclability of Li-CO_(2) batteries for energy storage applications.展开更多
Elevated CO_(2) level in the atmosphere is expected and intrinsic water-use efficiency(iWUE).Although current found the tree growth decline in water-limited area,it is st to improve the tree growth rates results infer...Elevated CO_(2) level in the atmosphere is expected and intrinsic water-use efficiency(iWUE).Although current found the tree growth decline in water-limited area,it is st to improve the tree growth rates results inferring from tree rings unclear whether spruce trees in humid southwestern China benefit from the increasing 002.In this study,tree-ring width data were used to investigate the tree radial growth rate of Chuanxi spruce(Picea likiangensis var.balfouriana).Moreover,combining with the tree-ring carbon isotope date,we analyzed the physiological responses of Chuanxi spruce to rising CO_(2) concentrations in the atmosphere(C_(a))associated with climatic change in southwestern China.From 1851 to 2009,iWUE of Chuanxi spruce rose by approximately 30.4%,and the ratio of atmospheric CO_(2) to leaf in-tercellular CO_(2) concentration(C_(j)/C_(a))showed no significant trend in the study area.The result suggested that Chuanxi spruce used an active response strategy when C_(a) was significantly increased,iWUE showed a significant increasing trend in parallel with tree radial growth,indicating that the increasing iWUE resulted in an increase in radial growth.These results suggest that spruce forests in southwestern China have not shown declining trends under increasing Ca and climate change scenarios,in contrast to trees growing in water-limited areas.Therefore,spruce forests benefit from the increasing CO_(2) in the atmosphere in the humid areas of southwestern China.展开更多
Carbonate-modified metal-support interfaces allow Ru/MnCO_(3) catalyst to exhibit over 99% selectivity,great specific activity and long-term anti-CO poisoning stability in atmospheric CO_(2) methanation.As a contrast,...Carbonate-modified metal-support interfaces allow Ru/MnCO_(3) catalyst to exhibit over 99% selectivity,great specific activity and long-term anti-CO poisoning stability in atmospheric CO_(2) methanation.As a contrast,Ru/MnO catalyst with metal-oxide interfaces prefers reverse water-gas shift rather than methanation route,along with a remarkably lower activity and a less than 15% CH_(4) selectivity.The carbonatemodified interfaces are found to stabilize the Ru species and activate CO_(2) and H_(2) molecules.Ru-CO^(4) species are identified as the reaction intermediates steadily formed from CO_(2) dissociation,which show moderate adsorption strength and high reactivity in further hydrogenation to CH_(4),Furthermore,carbonates of Ru/MnCO_(3) are found to be consumed by hydrogenation to form CH_(4) and replenished by exchange with CO_(2),which are in a dynamic equilibrium during the reaction.Modification with surface carbonates is proved as an efficient strategy to endow metal-support interfaces of Ru-based catalysts with unique catalytic functions for selective CO_(2) hydrogenation.展开更多
In the past two decades,research on C_(2)storage in coal seams and simultaneously enhanced coalbed methane recovery(ECBM)has attracted a lot of attention due to its win–win effect between greenhouse gas(C_(2))emissio...In the past two decades,research on C_(2)storage in coal seams and simultaneously enhanced coalbed methane recovery(ECBM)has attracted a lot of attention due to its win–win effect between greenhouse gas(C_(2))emission reduction and coalbed methane recovery enhancement.This paper presents an overview on the current status of research on C_(2)-ECBM in the past two decades,which involves C_(2)storage capacity evaluations,laboratory investigations,modelings and pilot tests.The current status shows that we have made great progress in the ECBM technology study,especially in the understanding of the ECBM mechanisms.However,there still have many technical challenges,such as the definition of unmineable coal seams for C_(2)storage capacity evaluation and storage site characterization,methods for C_(2)injectivity enhancement,etc.The low injectivity of coal seams and injectivity loss with C_(2)injection are the major technique challenges of ECBM.We also search several ways to promote the advancement of ECBM technology in the present stage,such as integrating ECBM with hydraulic fracturing,using a gas mixture instead of pure C_(2)for injection into coal seams and the application of ECBM to underground coal mines.展开更多
As an important part of carbon neutralization,carbon dioxide electroreduction reaction(CO_(2)RR)can convert CO_(2)into high value-added chemicals and fuels to realize the recycling of carbon resources and solve the pr...As an important part of carbon neutralization,carbon dioxide electroreduction reaction(CO_(2)RR)can convert CO_(2)into high value-added chemicals and fuels to realize the recycling of carbon resources and solve the problem of environmental pollution.Therefore,exploring the element species and surface structure of the catalyst plays a central role in improving the performance of the catalyst,enhancing the CO_(2)conversion efficiency and forming C1 and C_(2+)products.Here,we summarize the recent progress in the selective regulation of CO_(2)RR reaction products by different elements.In particular,we emphasize the structure-property relationship of CO_(2)RR by the microenvironment of metal center and substrate,heteroatom doping,hydrogen bond network of metal-free polymer,and construction of heterogeneous catalytic system.At the same time,the recent advances for the identification of CO_(2)RR active sites and mechanistic studies on the process of reducing CO_(2)conversion to different products are reviewed,as well as a comprehensive review to the final products.Finally,we outline the inevitable challenges faced by CO_(2)RR and present our own recommendations aimed at contributing to CO_(2)resource utilization.展开更多
基金supported by the National Natural Science Foundation of China(21890383 and 21901135)the China Postdoctoral Science Foundation(2020M680536)the State Key Laboratory of Coordination Chemistry(SKLCC2106).
文摘Main observation and conclusion By a strategy of fine-tuning of packing mode between the adjacent layers in a 2D net metal-organic frameworks(MOFs)through ligand changing,two 2D sql-type MOFs with highly selective CO_(2)uptake,CuHIN and CuHPB,were successfully synthesized.Compared with the precursor MOF-2,the fine-tuning structure of CuHIN shows selective adsorption of CO_(2)over N_(2)and CH_(4)with the CO_(2)uptake amounts as high as 4.7 wt%at 0.15 bar and at 298 K,and CO_(2)selectivity towards N_(2)and CH_(4)is 165.8 and 10.22 at 1 bar and at 298 K,respectively.In addition,for the 2D MOFs,the dynamic porous structure depends on the interaction of the adjacent layers.The suitable interaction is good for gliding smoothly and gas adsorption.
文摘There are more and more researches on heat transfer characteristics and prediction of supercritical CO_(2).The method of adding adiabatic section before and after heating section is usually adopted in these researches to ensure that the fluid entering the heating section is no longer affected by boundary layer,but the appropriate length range of adiabatic section and the influence of entrance effect are not discussed.However,some studies show that the entrance effect would affect the heat transfer in mini tubes.This paper uses the commercial CFD code FLUENT 19.0 to numerically study the heat transfer of supercritical CO_(2) in a mini tube under different working conditions(such as Re_(in),P_(in),q_(w) and flow direction)and the lengths of the adiabatic section(l_(as)/d).The entrance effects on heat transfer is more pronounced when Re_(in) is within the transition state and wall heat flux is relatively high,the resulting heat transfer deterioration causes T_(w,x) and h_(w,x) to rise sharply.As the adiabatic section increases,the location at which the heat exchange deteriorates moves to the entrance of the heating section and eventually leaves.The buoyancy effect and flow acceleration effect caused by the sharp change of physical properties are analyzed,and the dimensionless velocity distribution at the inlet of the heating section in different adiabatic sections is compared.It is proved that the entrance effect has an influence on the convection heat transfer of supercritical CO_(2) in mini tubes.The interaction reflected by wall shear stress between boundary layer development and drastic changes in physical properties is the cause of heat transfer deterioration.
基金This work was supported by the National Natural Science Foundation of China(No.52004236)Sichuan Science and Technology Program(No.2021JDRC0114)+4 种基金the Starting Project of Southwest Petroleum University(No.2019QHZ009)the China Postdoctoral Science Foundation(No.2020M673285)the Open Project Program of Key Laboratory of Groundwater Resources and Environment(Jilin University)Ministry of Education(No.202005009KF)the Chinese Scholarship Council(CSC)funding(No.202008515107).
文摘CO_(2) drilling is a promising underbalance drilling technology with great advantages,such as lower cutting force,intense cooling and excellent lubrication.However,in the underbalance drilling,the mechanism of the coupling CO_(2) jet and polycrystalline-diamond-compact(PDC)cutter are still unclear.Whereby,we established a coupled smoothed particle hydrodynamics/finite element method(SPH/FEM)model to simulate the composite rock-breaking of high-pressure CO_(2) jet&PDC cutter.Combined with the experimental research results,the mechanism of composite rock-breaking is studied from the perspectives of rock stress field,cutting force and jet field.The results show that the composite rock-breaking can effectively relieve the influence of vibration and shock on PDC cutter.Meanwhile,the high-pressure CO_(2) jet has a positive effect on carrying rock debris,which can effectively reduce the temperature rising and the thermal wear of the PDC cutter.In addition,the effects of CO_(2) jet parameters on composite rock-breaking were studied,such as jet impact velocity,nozzle diameter,jet injection angle and impact distance.The studies show that when the impact velocity of the CO_(2) jet is greater than 250 m/s,the CO_(2) jet could quickly break the rock.It is found that the optimal range of nozzle diameter is 1.5–2.5 mm,the best injection angle of CO_(2) jet is 60,the optimal impact distance is 10 times the nozzle diameter.The above studies could provide theoretical supports and technical guidance for composite rock-breaking,which is useful for the CO_(2) underbalance drilling and drill bit design.
基金supported by the the National Natural Science Foundation of China(Nos.52022088,51971245,51772262,21406191,U20A20336,and 21935009)Beijing Natural Science Foundation(No.2202046)+3 种基金Selective funding for provincial postdoctoral research projects(No.B2019003018)Fok Ying-Tong Education Foundation of China(No.171064)Natural Science Foundation of Hebei Province(Nos.B2020203037,and B2018203297)Hunan Innovation Team(No.2018RS3091).
文摘Rechargeable lithium-carbon dioxide(Li-CO_(2))batteries have attracted much attention due to their high theoretical energy densities and capture of C0_(2).However,the electrochemical reaction mechanisms of rechargeable Lo-CO_(2) batteries,particularly the decomposition mechanisms of the discharge product Li_(2)CO_(3) are still unclear,impeding their practical applications.Exploring electrochemistry of Li_(2)CO_(3) is critical for improving the performance of Li-C0_(2) batteries.Herein,in-situ environmental transmission electron microscopy(ETEM)technique was used to study electrochemistry of Li_(2)CO_(3) in Li-C0_(2) batteries during discharge and charge processes.During discharge,Li_(2)CO_(3) was nucleated and accumulated on the surface of the cathode media such as carbon nanotubes(CNTs)and Ag nanowires(Ag NWs),but it was hard to decompose during charging at room temperature.To promote the decomposition of Li2C03,the charge reactions were conducted at high temperatures,during which Li_(2)CO_(3) was decomposed to lithium with release of gases.Density functional theory(DFT)calculations revealed that the synergistic effect of temperature and biasing facilitates the decomposition of Li_(2)CO_(3).This study not only provides a fundamental understanding to the high temperature Li-C0_(2) nanobatteries,but also offers a valid technique,i.e.,discharging/charging at high temperatures,to improve the cyclability of Li-CO_(2) batteries for energy storage applications.
基金National Basic Research Program of China‘973’,No.2012CB956201Key Program of National Natural Science Foundation of China,No.41630529
文摘Elevated CO_(2) level in the atmosphere is expected and intrinsic water-use efficiency(iWUE).Although current found the tree growth decline in water-limited area,it is st to improve the tree growth rates results inferring from tree rings unclear whether spruce trees in humid southwestern China benefit from the increasing 002.In this study,tree-ring width data were used to investigate the tree radial growth rate of Chuanxi spruce(Picea likiangensis var.balfouriana).Moreover,combining with the tree-ring carbon isotope date,we analyzed the physiological responses of Chuanxi spruce to rising CO_(2) concentrations in the atmosphere(C_(a))associated with climatic change in southwestern China.From 1851 to 2009,iWUE of Chuanxi spruce rose by approximately 30.4%,and the ratio of atmospheric CO_(2) to leaf in-tercellular CO_(2) concentration(C_(j)/C_(a))showed no significant trend in the study area.The result suggested that Chuanxi spruce used an active response strategy when C_(a) was significantly increased,iWUE showed a significant increasing trend in parallel with tree radial growth,indicating that the increasing iWUE resulted in an increase in radial growth.These results suggest that spruce forests in southwestern China have not shown declining trends under increasing Ca and climate change scenarios,in contrast to trees growing in water-limited areas.Therefore,spruce forests benefit from the increasing CO_(2) in the atmosphere in the humid areas of southwestern China.
基金the National Key R&D Program of China(2018YFE0122600)the National Natural Science Foundation of China(21802070).
文摘Carbonate-modified metal-support interfaces allow Ru/MnCO_(3) catalyst to exhibit over 99% selectivity,great specific activity and long-term anti-CO poisoning stability in atmospheric CO_(2) methanation.As a contrast,Ru/MnO catalyst with metal-oxide interfaces prefers reverse water-gas shift rather than methanation route,along with a remarkably lower activity and a less than 15% CH_(4) selectivity.The carbonatemodified interfaces are found to stabilize the Ru species and activate CO_(2) and H_(2) molecules.Ru-CO^(4) species are identified as the reaction intermediates steadily formed from CO_(2) dissociation,which show moderate adsorption strength and high reactivity in further hydrogenation to CH_(4),Furthermore,carbonates of Ru/MnCO_(3) are found to be consumed by hydrogenation to form CH_(4) and replenished by exchange with CO_(2),which are in a dynamic equilibrium during the reaction.Modification with surface carbonates is proved as an efficient strategy to endow metal-support interfaces of Ru-based catalysts with unique catalytic functions for selective CO_(2) hydrogenation.
基金Supported by the National Natural Science Foundation of China(51104143).
文摘In the past two decades,research on C_(2)storage in coal seams and simultaneously enhanced coalbed methane recovery(ECBM)has attracted a lot of attention due to its win–win effect between greenhouse gas(C_(2))emission reduction and coalbed methane recovery enhancement.This paper presents an overview on the current status of research on C_(2)-ECBM in the past two decades,which involves C_(2)storage capacity evaluations,laboratory investigations,modelings and pilot tests.The current status shows that we have made great progress in the ECBM technology study,especially in the understanding of the ECBM mechanisms.However,there still have many technical challenges,such as the definition of unmineable coal seams for C_(2)storage capacity evaluation and storage site characterization,methods for C_(2)injectivity enhancement,etc.The low injectivity of coal seams and injectivity loss with C_(2)injection are the major technique challenges of ECBM.We also search several ways to promote the advancement of ECBM technology in the present stage,such as integrating ECBM with hydraulic fracturing,using a gas mixture instead of pure C_(2)for injection into coal seams and the application of ECBM to underground coal mines.
基金the National Natural Science Foundation of China(No.22171157).
文摘As an important part of carbon neutralization,carbon dioxide electroreduction reaction(CO_(2)RR)can convert CO_(2)into high value-added chemicals and fuels to realize the recycling of carbon resources and solve the problem of environmental pollution.Therefore,exploring the element species and surface structure of the catalyst plays a central role in improving the performance of the catalyst,enhancing the CO_(2)conversion efficiency and forming C1 and C_(2+)products.Here,we summarize the recent progress in the selective regulation of CO_(2)RR reaction products by different elements.In particular,we emphasize the structure-property relationship of CO_(2)RR by the microenvironment of metal center and substrate,heteroatom doping,hydrogen bond network of metal-free polymer,and construction of heterogeneous catalytic system.At the same time,the recent advances for the identification of CO_(2)RR active sites and mechanistic studies on the process of reducing CO_(2)conversion to different products are reviewed,as well as a comprehensive review to the final products.Finally,we outline the inevitable challenges faced by CO_(2)RR and present our own recommendations aimed at contributing to CO_(2)resource utilization.
