Pt-based catalysts are widely used in propane dehydrogenation reaction for the production of propylene.Suppressing irreversible deactivation caused by the sintering of Pt particles under harsh conditions and regenerat...Pt-based catalysts are widely used in propane dehydrogenation reaction for the production of propylene.Suppressing irreversible deactivation caused by the sintering of Pt particles under harsh conditions and regeneration process is a significant challenge in this catalyst.Herein,a series of highly ordered mesoporous Al_(2)O_(3) supports with different levels of Al3+penta sites,are fabricated and used as the support to disperse Pt-Sn_(2) clusters.Characterizations of Pt-Sn_(2)/meso-Al_(2)O_(3) with XRD,NMR,CO-IR,STEM,TG,and Raman techniques along with propane dehydrogenation-regeneration cycles test reveal the structure-stability-re generability relationship.The coordinatively unsaturated pentacoordinate Al_(Al3+penta)^(3+)can strongly anchor Pt atoms via a formation of Al-O-Pt bond,and thus stabilize the Pt-based particles at the surface of Al_(2)O_(3).The stability and regenerability of Pt-Sn2/meso-Al_(2)O_(3) are strongly dependent on the content of Al3+penta sites in the Al_(2)O_(3) structure,and a high level of Al3+penta sites can effectively prevent the agglomeration of Pt-Sn2 clusters into large Pt nanoparticles in the consecutive dehydrogenation-regeneration cycles.The Pt-Sn2/meso-Al_(2)O_(3)-600 with the highest level of Al_(penta)^(3+) (50.8%)delivers the best performance in propane dehydrogenation,which exhibits propane conversion of 40%and propylene selectivity above 98%at 570℃ with 10 vol%C_(3)H_(8) and 10 vol% H_(2) feed.A slow deactivation in this catalyst is ascribed to the formation of coke,and the catalytic performance can be fully restored in the consecutive dehydrogenation-regeneration cycles via a simple calcination treatment.展开更多
The FTP200 flake tantalum powder was introduced.The microstructures of the powder with leaf-like primary particles having an average flakiness of 2 to 20 and porous agglomerated particles were observed.The chemical co...The FTP200 flake tantalum powder was introduced.The microstructures of the powder with leaf-like primary particles having an average flakiness of 2 to 20 and porous agglomerated particles were observed.The chemical composition,physical properties,and electrical properties of the FTP200 powder were compared with those of the FTW300 nodular powder.The FTP200 powder is more sinter-resistant,and the surface area of the flake tantalum powder under sintering at high temperature has less loss than that of the nodular tantalum powder.The specific capacitance of the flake tantalum powder is higher than that of the nodular tantalum powder with the same surface area when anodized at high voltage.Thus,the flake tantalum powder is suitable for manufacturing tantalum solid electrolytic capacitors in the range of median and high（20-63 V） voltages.展开更多
Exploring cost-effective catalysts with high catalytic performance and long-term stability has always been a general concern for environment protection and energy conversion.Here,Au nanoparticles(NPs)embedded CuOx-CeO...Exploring cost-effective catalysts with high catalytic performance and long-term stability has always been a general concern for environment protection and energy conversion.Here,Au nanoparticles(NPs)embedded CuOx-CeO2 core/shell nanospheres(Au@CuOx-CeO2 CSNs)have been successfully prepared through a versatile one-pot method at ambient conditions.The spontaneous auto-redox reaction between HAuCl4 and Ce(OH)3 in aqueous solution triggered the self-assembly growth of micro-/nanostructural Au@CuOx-CeO2 CSNs.Meanwhile,the CuOx clusters in Au@CuOx-CeO2 CSNs are capable of improving the anti-sintering ability of Au NPs and providing synergistic catalysis benefits.As a result,the confined Au NPs exhibited extraordinary thermal stability even at a harsh thermal condition up to 700℃.In addition,before and after the severe calcination process,Au@CuOx-CeO2 CSNs can exhibit enhanced catalytic activity and excellent recyclability towards the hydrogenation of p-nitrophenol compared to previously reported nanocatalysts.The synergistic catalysis path between Au/CuOx/CeO2 triphasic interfaces was revealed by density functional theory(DFT)calculations.The CuOx clusters around the embedded Au NPs can provide moderate adsorption strength of p-nitrophenol,while the adjacent CeO2-supported Au NPs can facilitate the hydrogen dissociation to form H*species,which contributes to achieve the efficient reduction of p-nitrophenol.This study opens up new possibilities for developing high-efficient and sintering-resistant micro-/nanostructural nanocatalysts by exploiting multiphasic systems.展开更多
基金Financial supports of the National Natural Science Foundation of China(21878050,91934301)the State Key Laboratory of Coal Conversion(J21-22-620)the 111 Project(D17005)。
文摘Pt-based catalysts are widely used in propane dehydrogenation reaction for the production of propylene.Suppressing irreversible deactivation caused by the sintering of Pt particles under harsh conditions and regeneration process is a significant challenge in this catalyst.Herein,a series of highly ordered mesoporous Al_(2)O_(3) supports with different levels of Al3+penta sites,are fabricated and used as the support to disperse Pt-Sn_(2) clusters.Characterizations of Pt-Sn_(2)/meso-Al_(2)O_(3) with XRD,NMR,CO-IR,STEM,TG,and Raman techniques along with propane dehydrogenation-regeneration cycles test reveal the structure-stability-re generability relationship.The coordinatively unsaturated pentacoordinate Al_(Al3+penta)^(3+)can strongly anchor Pt atoms via a formation of Al-O-Pt bond,and thus stabilize the Pt-based particles at the surface of Al_(2)O_(3).The stability and regenerability of Pt-Sn2/meso-Al_(2)O_(3) are strongly dependent on the content of Al3+penta sites in the Al_(2)O_(3) structure,and a high level of Al3+penta sites can effectively prevent the agglomeration of Pt-Sn2 clusters into large Pt nanoparticles in the consecutive dehydrogenation-regeneration cycles.The Pt-Sn2/meso-Al_(2)O_(3)-600 with the highest level of Al_(penta)^(3+) (50.8%)delivers the best performance in propane dehydrogenation,which exhibits propane conversion of 40%and propylene selectivity above 98%at 570℃ with 10 vol%C_(3)H_(8) and 10 vol% H_(2) feed.A slow deactivation in this catalyst is ascribed to the formation of coke,and the catalytic performance can be fully restored in the consecutive dehydrogenation-regeneration cycles via a simple calcination treatment.
文摘The FTP200 flake tantalum powder was introduced.The microstructures of the powder with leaf-like primary particles having an average flakiness of 2 to 20 and porous agglomerated particles were observed.The chemical composition,physical properties,and electrical properties of the FTP200 powder were compared with those of the FTW300 nodular powder.The FTP200 powder is more sinter-resistant,and the surface area of the flake tantalum powder under sintering at high temperature has less loss than that of the nodular tantalum powder.The specific capacitance of the flake tantalum powder is higher than that of the nodular tantalum powder with the same surface area when anodized at high voltage.Thus,the flake tantalum powder is suitable for manufacturing tantalum solid electrolytic capacitors in the range of median and high（20-63 V） voltages.
基金The authors are grateful for the financial support of the National Natural Science Foundation of China(Nos.21590791,21771005,21931001,and 21927901)Ministry of Science and Technology(MOST)of China(Nos.2014CB643803,2017YFA0205101,and 2017YFA0205104)+1 种基金The computational work was supported by the High-performance Computing Platform of Peking University.K.W.specifically thanks the National Postdoctoral Program for Innovative Talents under grant No.BX20190005the China Postdoctoral Science Foundation(No.2019M660293).
文摘Exploring cost-effective catalysts with high catalytic performance and long-term stability has always been a general concern for environment protection and energy conversion.Here,Au nanoparticles(NPs)embedded CuOx-CeO2 core/shell nanospheres(Au@CuOx-CeO2 CSNs)have been successfully prepared through a versatile one-pot method at ambient conditions.The spontaneous auto-redox reaction between HAuCl4 and Ce(OH)3 in aqueous solution triggered the self-assembly growth of micro-/nanostructural Au@CuOx-CeO2 CSNs.Meanwhile,the CuOx clusters in Au@CuOx-CeO2 CSNs are capable of improving the anti-sintering ability of Au NPs and providing synergistic catalysis benefits.As a result,the confined Au NPs exhibited extraordinary thermal stability even at a harsh thermal condition up to 700℃.In addition,before and after the severe calcination process,Au@CuOx-CeO2 CSNs can exhibit enhanced catalytic activity and excellent recyclability towards the hydrogenation of p-nitrophenol compared to previously reported nanocatalysts.The synergistic catalysis path between Au/CuOx/CeO2 triphasic interfaces was revealed by density functional theory(DFT)calculations.The CuOx clusters around the embedded Au NPs can provide moderate adsorption strength of p-nitrophenol,while the adjacent CeO2-supported Au NPs can facilitate the hydrogen dissociation to form H*species,which contributes to achieve the efficient reduction of p-nitrophenol.This study opens up new possibilities for developing high-efficient and sintering-resistant micro-/nanostructural nanocatalysts by exploiting multiphasic systems.
基金supported by the National Science Fund for Distinguished Young Scholars of China(21825801)the National Natural Science Foundation of China(21972019,21978051).
