Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existin...Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existing catalyst is limited due to the poor activity and stability,which hinders its industrialization.Herein,we design the finned Zn-MFI zeolite encapsulated noble metal nanoparticles(NPs)as bifunctional catalysts(NPs@Zn-MFI)for CO_(2)-ODP.Characterization results reveal that the Zn2+species are coordinated with the MFI zeolite matrix as isolated cations and the NPs of Pt,Rh,or Rh Pt are highly dispersed in the zeolite crystals.The isolated Zn2+cations are very effective for activating the propane and the small NPs are favorable for activating the CO_(2),which synergistically promote the selective transformation of propane and CO_(2)to propylene and CO.As a result,the optimal 0.25%Rh0.50%Pt@Zn-MFI catalyst shows the best propylene yield,satisfactory CO_(2)conversion,and long-term stability.Moreover,considering the tunable synergetic effects between the isolated cations and NPs,the developed approach offers a general guideline to design more efficient CO_(2)-ODP catalysts,which is validated by the improved performance of the bifunctional catalysts via simply substituting Sn4+cations for Zn2+cations in the MFI zeolite matrix.展开更多
We propose a new strategy to make an active and stable Ni-based catalyst which can be operated in a wide range of reaction temperatures. The ordered mesoporous alumina(OMA) with confined Ni in the pore wall(Ni-OMA) wa...We propose a new strategy to make an active and stable Ni-based catalyst which can be operated in a wide range of reaction temperatures. The ordered mesoporous alumina(OMA) with confined Ni in the pore wall(Ni-OMA) was prepared via the one-pot evaporation induced self-assembly method. By using the incipient impregnation method, different amounts of free Ni were loaded over Ni-OMA(Ni/NiOMA) at a fixed total NiO content of 15 wt%. Characterization results confirmed the formation of wellstructured Ni-OMA, and the ordered structure was still well preserved even after impregnating NiO at a content of as high as 12 wt%. The catalysts were evaluated for the CO methanation as a model reaction under varied conditions. Importantly, the activity and stability of Ni/Ni-OMA for the titled reaction were significantly regulated by simply changing the ratio of the confined to free Ni. Over the optimum catalyst of NiO(2 wt%)/NiO(13 wt%)-OMA, the high activity at a temperature of as low as 300 ℃ was achieved with the space-time yield of methane over 7.6 g gcat-1 h-1 while a long-term stability for a time-onstream of 400 h was confirmed without an observable deactivation under the conditions of 600 ℃ and an extremely high gas hourly space velocity of 120,000 mL g-1 h-1. The results were well explained as the integrated merits of the free Ni for a high dispersion and the confined Ni in OMA for the anti-sintering property.展开更多
Developing hydroscopic actuators with simultaneous high elasticity,shape programmability and tunable actuating behaviors are highly desired but still challenging.In this study,we propose an orthogonal composite design...Developing hydroscopic actuators with simultaneous high elasticity,shape programmability and tunable actuating behaviors are highly desired but still challenging.In this study,we propose an orthogonal composite design to develop such a material.The developed composite elastomer comprises carboxyl group-grafted polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene(SEBS-g-COOH)as the elastic substrate,and a synthesized azobenzene derivative as the functional filler(Azo12).By surface treatment using acidic and base solutions,the carboxyl groups on the surface can reversibly transform into carboxylate groups,which render the composite tunable hygroscopic actuating functionality.On another aspect,the added filler undergoes trans-to-cis isomerization when exposed to UV light irradiation,leading to liquefaction of the crystalline aggregates formed by Azo12 molecules.The liquefied Azo12 molecules can autonomously resotre their trans form and reform the crystalline structure.This reversible change in crystralline structure is utilized to realize the shape memory property,and 5 wt%of Azo12addition is adequate for the composite to exhibit photo-responsive shape memory behavior without compromising much of the elasricity.The regualtion of external geometry by shape memory effect is effective in altering the actuating behavior.The proposed method can be extend to designing different composites with the demonstrated functionalities.展开更多
CO_(2)-assisted oxidative dehydrogenation of propane(CO_(2)-ODHP)is an attractive strategy to offset the demand gap of propylene due to its potentiality of reducing CO_(2)emissions,especially under the demands of peak...CO_(2)-assisted oxidative dehydrogenation of propane(CO_(2)-ODHP)is an attractive strategy to offset the demand gap of propylene due to its potentiality of reducing CO_(2)emissions,especially under the demands of peaking CO_(2)emissions and carbon neutrality.The introduction of CO_(2)as a soft oxidant into the reaction not only averts the over-oxidation of products,but also maintains the high oxidation state of the redox-active sites.Furthermore,the presence of CO_(2)increases the conversion of propane by coupling the dehydrogenation of propane(DHP)with the reverse water gas reaction(RWGS)and inhibits the coking formation to prolong the lifetime of catalysts via the reverse Boudouard reaction.An effective catalyst should selectively activate the C–H bond but suppress the C–C cleavage.However,to prepare such a catalyst remains challenging.Chromium-based catalysts are always applied in industrial application of DHP;however,their toxic properties are harmful to the environment.In this aspect,exploring environment-friendly and sustainable catalytic systems with Cr-free is an important issue.In this review,we outline the development of the CO_(2)-ODHP especially in the last ten years,including the structural information,catalytic performances,and mechanisms of chromium-free metal-based catalyst systems,and the role of CO_(2)in the reaction.We also present perspectives for future progress in the CO_(2)-ODHP.展开更多
A betaine-type styrene monomer with the quaternary ammonium-borate anion inner-salt pair was synthesized through the quatemization reaction and polymerized to afford the target polybetaine of poly(4-vinylbenzyl methy...A betaine-type styrene monomer with the quaternary ammonium-borate anion inner-salt pair was synthesized through the quatemization reaction and polymerized to afford the target polybetaine of poly(4-vinylbenzyl methyl-diethanol ammonium borate) (PVMAB). The chemical structures of the monomer and polymer were well demonstrated with 1H-NMR and llB-NMR spectra analysis. The thermal-sensitive experiment showed that PVMAB in water afforded gradually well- defined sigmoidal transmittance-temperature (T-t) curves along with the increasing polymer concentration. However, the phase transition temperatures at the bottom of the S-shaped curves were always below l0 ~C due to the very weak zwitterionic association of the ammonium-borate inner-salt pairs. The UCST phase transition could also be tuned by changing the ethanol content in the ethanol/water mixture. And the cytotoxicity experiment demonstrated the good biomimetic property of PVMAB. This study enriches the toolbox of polybetaines by introducing the quaternary ammonium- borate anion zwitterionic pair in the repeat units, therefore broadens the scope of synthetic polybetaines.展开更多
基金supported by the National Natural Science Foundation of China(21902097,21636006 and 21761132025)the China Postdoctoral Science Foundation(2019M653861XB)+1 种基金the Natural Science Foundation of Shaanxi Province(2020JQ-409)the Fundamental Research Funds for the Central Universities(GK201901001 and GK202003035)。
文摘Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existing catalyst is limited due to the poor activity and stability,which hinders its industrialization.Herein,we design the finned Zn-MFI zeolite encapsulated noble metal nanoparticles(NPs)as bifunctional catalysts(NPs@Zn-MFI)for CO_(2)-ODP.Characterization results reveal that the Zn2+species are coordinated with the MFI zeolite matrix as isolated cations and the NPs of Pt,Rh,or Rh Pt are highly dispersed in the zeolite crystals.The isolated Zn2+cations are very effective for activating the propane and the small NPs are favorable for activating the CO_(2),which synergistically promote the selective transformation of propane and CO_(2)to propylene and CO.As a result,the optimal 0.25%Rh0.50%Pt@Zn-MFI catalyst shows the best propylene yield,satisfactory CO_(2)conversion,and long-term stability.Moreover,considering the tunable synergetic effects between the isolated cations and NPs,the developed approach offers a general guideline to design more efficient CO_(2)-ODP catalysts,which is validated by the improved performance of the bifunctional catalysts via simply substituting Sn4+cations for Zn2+cations in the MFI zeolite matrix.
基金the National Natural Science Foundation of China(U1862116)the National Key Research and Development Program of China(2018YFB0604600-04)the Fundamental Research Funds for the Central Universities(GK201901001)。
文摘We propose a new strategy to make an active and stable Ni-based catalyst which can be operated in a wide range of reaction temperatures. The ordered mesoporous alumina(OMA) with confined Ni in the pore wall(Ni-OMA) was prepared via the one-pot evaporation induced self-assembly method. By using the incipient impregnation method, different amounts of free Ni were loaded over Ni-OMA(Ni/NiOMA) at a fixed total NiO content of 15 wt%. Characterization results confirmed the formation of wellstructured Ni-OMA, and the ordered structure was still well preserved even after impregnating NiO at a content of as high as 12 wt%. The catalysts were evaluated for the CO methanation as a model reaction under varied conditions. Importantly, the activity and stability of Ni/Ni-OMA for the titled reaction were significantly regulated by simply changing the ratio of the confined to free Ni. Over the optimum catalyst of NiO(2 wt%)/NiO(13 wt%)-OMA, the high activity at a temperature of as low as 300 ℃ was achieved with the space-time yield of methane over 7.6 g gcat-1 h-1 while a long-term stability for a time-onstream of 400 h was confirmed without an observable deactivation under the conditions of 600 ℃ and an extremely high gas hourly space velocity of 120,000 mL g-1 h-1. The results were well explained as the integrated merits of the free Ni for a high dispersion and the confined Ni in OMA for the anti-sintering property.
基金financially supported by the National Natural Science Foundation of China(Nos.51803115 and 21636006)the Fundamental Research Funds for the Central Universities(Nos.GK201901001,2021CSLY008,2021CSZL003 and GK202103032)the Innovation Capability Support Program of Shaanxi(No.2020TD-024)。
文摘Developing hydroscopic actuators with simultaneous high elasticity,shape programmability and tunable actuating behaviors are highly desired but still challenging.In this study,we propose an orthogonal composite design to develop such a material.The developed composite elastomer comprises carboxyl group-grafted polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene(SEBS-g-COOH)as the elastic substrate,and a synthesized azobenzene derivative as the functional filler(Azo12).By surface treatment using acidic and base solutions,the carboxyl groups on the surface can reversibly transform into carboxylate groups,which render the composite tunable hygroscopic actuating functionality.On another aspect,the added filler undergoes trans-to-cis isomerization when exposed to UV light irradiation,leading to liquefaction of the crystalline aggregates formed by Azo12 molecules.The liquefied Azo12 molecules can autonomously resotre their trans form and reform the crystalline structure.This reversible change in crystralline structure is utilized to realize the shape memory property,and 5 wt%of Azo12addition is adequate for the composite to exhibit photo-responsive shape memory behavior without compromising much of the elasricity.The regualtion of external geometry by shape memory effect is effective in altering the actuating behavior.The proposed method can be extend to designing different composites with the demonstrated functionalities.
基金financially supported by the National Natural Science Foundation of China (Nos. 21978160, 22078182 and 21908139)the Key Industrial Innovation Project of Shaanxi Provincial Science and Technology Department (No. 2019ZDLGY06-04)+1 种基金the Project Supported by Natural Science Basic Research Plan in Shaanxi Province of China (No. 2019JLM-16)the Key Project of Education Department of Shaanxi Province (No. 21JY005)
文摘CO_(2)-assisted oxidative dehydrogenation of propane(CO_(2)-ODHP)is an attractive strategy to offset the demand gap of propylene due to its potentiality of reducing CO_(2)emissions,especially under the demands of peaking CO_(2)emissions and carbon neutrality.The introduction of CO_(2)as a soft oxidant into the reaction not only averts the over-oxidation of products,but also maintains the high oxidation state of the redox-active sites.Furthermore,the presence of CO_(2)increases the conversion of propane by coupling the dehydrogenation of propane(DHP)with the reverse water gas reaction(RWGS)and inhibits the coking formation to prolong the lifetime of catalysts via the reverse Boudouard reaction.An effective catalyst should selectively activate the C–H bond but suppress the C–C cleavage.However,to prepare such a catalyst remains challenging.Chromium-based catalysts are always applied in industrial application of DHP;however,their toxic properties are harmful to the environment.In this aspect,exploring environment-friendly and sustainable catalytic systems with Cr-free is an important issue.In this review,we outline the development of the CO_(2)-ODHP especially in the last ten years,including the structural information,catalytic performances,and mechanisms of chromium-free metal-based catalyst systems,and the role of CO_(2)in the reaction.We also present perspectives for future progress in the CO_(2)-ODHP.
基金financially supported by the National Natural Science Foundation of China(No.21374056)the Program for Changjiang Scholars and Innovative Research Team in Universities(IRT 14R33)+3 种基金the Natural Science Basic Research Plan in Shaanxi Province of China(NSBRP-SPC 2014JM2051)the Program of Introducing Talents of Discipline to Universities(B14041)Shaanxi Innovative Research Team for Key Science and Technology(2012KCT-21,2013KCT-17)the One Hundred Plan of Shaanxi Province
文摘A betaine-type styrene monomer with the quaternary ammonium-borate anion inner-salt pair was synthesized through the quatemization reaction and polymerized to afford the target polybetaine of poly(4-vinylbenzyl methyl-diethanol ammonium borate) (PVMAB). The chemical structures of the monomer and polymer were well demonstrated with 1H-NMR and llB-NMR spectra analysis. The thermal-sensitive experiment showed that PVMAB in water afforded gradually well- defined sigmoidal transmittance-temperature (T-t) curves along with the increasing polymer concentration. However, the phase transition temperatures at the bottom of the S-shaped curves were always below l0 ~C due to the very weak zwitterionic association of the ammonium-borate inner-salt pairs. The UCST phase transition could also be tuned by changing the ethanol content in the ethanol/water mixture. And the cytotoxicity experiment demonstrated the good biomimetic property of PVMAB. This study enriches the toolbox of polybetaines by introducing the quaternary ammonium- borate anion zwitterionic pair in the repeat units, therefore broadens the scope of synthetic polybetaines.