Direct air capture(DAC)of CO_(2)plays an indispensable role in achieving carbon-neutral goals as one of the key negative emission technologies.Since large air flows are required to capture the ultradilute CO_(2)from t...Direct air capture(DAC)of CO_(2)plays an indispensable role in achieving carbon-neutral goals as one of the key negative emission technologies.Since large air flows are required to capture the ultradilute CO_(2)from the air,lab-synthesized adsorbents in powder form may cause unacceptable gas pressure drops and poor heat and mass transfer efficiencies.A structured adsorbent is essential for the implementation of gas-solid contactors for cost-and energy-efficient DAC systems.In this study,efficient adsorbent poly(ethyleneimine)(PEI)-functionalized Mg-Al-CO_(3)layered double hydroxide(LDH)-derived mixed metal oxides(MMOs)are three-dimensional(3D)printed into monoliths for the first time with more than 90%adsorbent loadings.The printing process has been optimized by initially printing the LDH powder into monoliths followed by calcination into MMO monoliths.This structure exhibits a 32.7%higher specific surface area and a 46.1%higher pore volume,as compared to the direct printing of the MMO powder into a monolith.After impregnation of PEI,the monolith demonstrates a large adsorption capacity(1.82 mmol/g)and fast kinetics(0.7 mmol/g/h)using a CO_(2)feed gas at 400 ppm at 25℃,one of the highest values among the shaped DAC adsorbents.Smearing of the amino-polymers during the post-printing process affects the diffusion of CO_(2),resulting in slower adsorption kinetics of pre-impregnation monoliths compared to post-impregnation monoliths.The optimal PEI/MeOH ratio for the post-impregnation solution prevents pores clogging that would affect both adsorption capacity and kinetics.展开更多
The utilization of supported amines as adsorbents in direct air capture(DAC)has been demonstrated to be a promising strategy for the reduction of CO_(2)emissions.To improve the performance of amine-based adsorbents,th...The utilization of supported amines as adsorbents in direct air capture(DAC)has been demonstrated to be a promising strategy for the reduction of CO_(2)emissions.To improve the performance of amine-based adsorbents,the incorporation of additives has been widely adopted.In the present study,we conduct a comprehensive comparison of seven additives on tetraethylenepentamine-impregnated mesoporous silica as a representative amine-based adsorbent.The results indicate thatminor molecularweight additiveswith hydroxyl groups show improved adsorption-desorption performance and increase oxidative stability.A proposed mechanism for these improvements is the combined physical and chemical promotion effects of hydroxyl groups.Through a comprehensive review of existing literature,it is found that the effects of additives on amine-based adsorbents are dependent on factors,such as additive type,pristine adsorbent properties,incorporation method,and testing conditions.Based on these findings,it is recommended that future DAC systems prioritize the use of hydroxyl-containing additives,whereas higher CO_(2)concentration and temperature capture may benefit from the incorporation of additives without hydroxyl groups.These conclusions are expected to contribute to the design of efficient adsorbents for CO_(2)capture.展开更多
基金supported by the Shanghai Agricultural Science and Technology Program (2022-02-08-00-12-F01176)he National Natural Science Foundation of China (52006135)
文摘Direct air capture(DAC)of CO_(2)plays an indispensable role in achieving carbon-neutral goals as one of the key negative emission technologies.Since large air flows are required to capture the ultradilute CO_(2)from the air,lab-synthesized adsorbents in powder form may cause unacceptable gas pressure drops and poor heat and mass transfer efficiencies.A structured adsorbent is essential for the implementation of gas-solid contactors for cost-and energy-efficient DAC systems.In this study,efficient adsorbent poly(ethyleneimine)(PEI)-functionalized Mg-Al-CO_(3)layered double hydroxide(LDH)-derived mixed metal oxides(MMOs)are three-dimensional(3D)printed into monoliths for the first time with more than 90%adsorbent loadings.The printing process has been optimized by initially printing the LDH powder into monoliths followed by calcination into MMO monoliths.This structure exhibits a 32.7%higher specific surface area and a 46.1%higher pore volume,as compared to the direct printing of the MMO powder into a monolith.After impregnation of PEI,the monolith demonstrates a large adsorption capacity(1.82 mmol/g)and fast kinetics(0.7 mmol/g/h)using a CO_(2)feed gas at 400 ppm at 25℃,one of the highest values among the shaped DAC adsorbents.Smearing of the amino-polymers during the post-printing process affects the diffusion of CO_(2),resulting in slower adsorption kinetics of pre-impregnation monoliths compared to post-impregnation monoliths.The optimal PEI/MeOH ratio for the post-impregnation solution prevents pores clogging that would affect both adsorption capacity and kinetics.
基金Science and Technology Commission of Shanghai Municipality(STCSM),Grant/Award Number:21DZ1206200National Natural Science Foundation of China,Grant/Award Numbers:72140008,52006135。
文摘The utilization of supported amines as adsorbents in direct air capture(DAC)has been demonstrated to be a promising strategy for the reduction of CO_(2)emissions.To improve the performance of amine-based adsorbents,the incorporation of additives has been widely adopted.In the present study,we conduct a comprehensive comparison of seven additives on tetraethylenepentamine-impregnated mesoporous silica as a representative amine-based adsorbent.The results indicate thatminor molecularweight additiveswith hydroxyl groups show improved adsorption-desorption performance and increase oxidative stability.A proposed mechanism for these improvements is the combined physical and chemical promotion effects of hydroxyl groups.Through a comprehensive review of existing literature,it is found that the effects of additives on amine-based adsorbents are dependent on factors,such as additive type,pristine adsorbent properties,incorporation method,and testing conditions.Based on these findings,it is recommended that future DAC systems prioritize the use of hydroxyl-containing additives,whereas higher CO_(2)concentration and temperature capture may benefit from the incorporation of additives without hydroxyl groups.These conclusions are expected to contribute to the design of efficient adsorbents for CO_(2)capture.
