The fundamental insights of the reaction mechanism,especially the synergistic effect between oxygen vacancies and basic sites,are highly promising yet challenging for Ru-based catalysts during carbon dioxide(CO_(2))me...The fundamental insights of the reaction mechanism,especially the synergistic effect between oxygen vacancies and basic sites,are highly promising yet challenging for Ru-based catalysts during carbon dioxide(CO_(2))methanation.Herein,a series of Rubased catalysts were employed to study the mechanism of CO_(2) methanation.It is found that Ru/CeO_(2) catalyst exhibits a much higher CO_(2) conversion(86%)and CH4 selectivity(100%),as well as excellent stability of 30 h due to the existence of abundant oxygen vacancies and weak basic sites.Additionally,the in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and density functional theory(DFT)calculations reveal that the formate formation step dominated the hydrogenation route on Ru/CeO_(2) catalyst,and the b-HCOO^(*)could be the key intermediate due to b-HCOO^(*)is more easily hydrogenated to methane than m-HCOO^(*).The systematic study marks the significance of precise tailoring of the synergistic relationship between oxygen vacancies and basic sites for achieving the desired performance in CO_(2) methanation.展开更多
As a typical process-intensive strategy,a tandem reaction driven by a multifunctional catalyst is a paragon of the green catalytic process.Two or more active sites are usually required and their rational spatial distr...As a typical process-intensive strategy,a tandem reaction driven by a multifunctional catalyst is a paragon of the green catalytic process.Two or more active sites are usually required and their rational spatial distribution is critical for the multi-functional catalyst to act independently or synergistically.Here,we present a simple and stepwise method to construct a trifunctional integrated catalyst simultaneously with spatially intimate acidic(phosphotungstic acid(HPW)),basic(amino)and metal(Pd nanoparticles(NPs))sites in hierarchically porous UiO-66-NH_(2).Through fine controlling the ratio of immobilized HPW and amino groups,we can easily tune its accessible acidic and basic properties,and the anchored HPW molecules can be effectively used to mediate the catalytic performance of Pd NPs and further stabilize the Pd sites.This well-designed integrated catalyst showed excellent catalytic activity and yield(>97%)towards onepot three-step Deacetalization-Knoevenagel-Hydrogenation(D-K-H)catalysis reactions owing to the synergetic catalysis and the intimate spatial arrangement of the acid,basic and metal sites.More importantly,the trifunctional catalyst could be recycled at least five times without significantly losing its activity due to the strong interaction between the MOF and the vip molecules.This work provides some important insights into the construction of multifunctional integrated catalysts,especially for the application in challenging tandem catalysis.展开更多
Ca/SBA-15 solid bases with different Ca/Si atomic ratios were prepared by a one-pot route and employed as catalysts for the production of poly（isosorbide carbonate） （PIC） from diphenyl carbonate and isosorbide via...Ca/SBA-15 solid bases with different Ca/Si atomic ratios were prepared by a one-pot route and employed as catalysts for the production of poly（isosorbide carbonate） （PIC） from diphenyl carbonate and isosorbide via a transesterification polymerization process. The relationship between physicochemical properties and catalytic performance for Ca/SBA-15 in this melt process was investigated by means of various characterization techniques. It was found that basic site amount and strength were responsible for this transesterification process; the weak and medium basic sites inclined to promote polycondensation reaction. It was worth noting that strong basic sites could favor the decomposition of the resultant P/C, resulting in the decrease of weight-average molecular weight （Mw） and yield, and the sample with Ca/Si atomic ratio of 0.4 exhibited the best catalytic performance, giving PIC with Mw of 4.88 × 10^4 g/mol and Tg of 169 ℃ at the optimal conditions. This excellent activity can be ascribed to the presence of rich basic sites and specific basic strength on the surface of 0.4Ca/SBA-15.展开更多
Mg-A1 mixed oxides with different Mg/A1 molar ratio were prepared by thermal decomposition of hydrotalcite-like precursors at 500℃for 5.0 h and used as catalysts for the transesterification of diphenyl carbonate with...Mg-A1 mixed oxides with different Mg/A1 molar ratio were prepared by thermal decomposition of hydrotalcite-like precursors at 500℃for 5.0 h and used as catalysts for the transesterification of diphenyl carbonate with 1,4-butanediol to synthesize high-molecular-weight poly(butylene carbonate)(PBC).The structure-activity correlations of these catalysts in this transesterification process were discussed by means of various characterization techniques.It was found that the chain growth for the formation of PBC can only be obtained through connecting-OH and-OC(C)OC6H5 end-group upon removing the generated phenol,and the sample with Mg/A1 molar ratio of 4.0 exhibited the best catalytic performance,giving PBC with Mw of 1.64×105 g/mol at 210℃for 3.0 h.This excellent activity depended mainly on the specific surface area and basicity rather than pore structure or crystallite size of MgO.展开更多
The Co3O4 and Zr-,Ce-,and La-Co3O4 catalysts were prepared,characterized,and applied to produce CH4 from CO_(2) catalytic hydrogenation in low temperature as 140–220℃.The results indicated that the addition of Zr,Ce...The Co3O4 and Zr-,Ce-,and La-Co3O4 catalysts were prepared,characterized,and applied to produce CH4 from CO_(2) catalytic hydrogenation in low temperature as 140–220℃.The results indicated that the addition of Zr,Ce,or La to the Co3O4 decreased the crystallite sizes of Co and the outer-shell electron density of Co^3+,and increased the specific surface area,which would provide more active sites for the CO_(2) methanation.Especially,the addition of Zr also changed the reducing state of Co3O4 via an obvious change in the interaction between Co3O4 and ZrO2.Furthermore,Zr doped into the Co3O4 increased the basic intensity of the weak and medium basic sites,as well as the amount of Lewis acid sites,and Bronsted acid sites were also found on the Zr-Co3O4 surface.The introduction of Zr,Ce,or La favored the production of CH4,and the Zr-Co3O4catalyst exhibited the highest CO_(2) conversion(58.2%)and CH4 selectivity(100%)at 200℃,and 0.5 MPa with a gaseous hourly space velocity of 18,000 ml·g^-1(cat)·h^-1,and the catalytic activity of CO_(2) methanation for the Zr-,Ce-,and La-Co3O4 exhibited more stable than Co3O4 in a 20-h reaction.展开更多
A polyhedral metal-organic framework(MOF)JLU-Liu40-In based on dual secondary building units(SBUs)of mononuclear and binuclear paddlewheel indium has been prepared with a nitrogen-rich tetracarboxylic acid ligand unde...A polyhedral metal-organic framework(MOF)JLU-Liu40-In based on dual secondary building units(SBUs)of mononuclear and binuclear paddlewheel indium has been prepared with a nitrogen-rich tetracarboxylic acid ligand under solvothermal conditions.Since the framework possesses large surface areas with multiple polyhedral cages,abundant open metal sites(OMSs)and Lewis basic sites(LBSs),it exhibits high performance for gas adsorption.In addition,through post-synthetic metal-ion metathesis in a single-crystal-to-single-crystal(SCSC)process,JLU-Liu40-In/Cu has been obtained by selectively substituting the paddlewheel In(Ⅲ)ions with Cu(Ⅱ)ions without replacing the mononuclear In(Ⅲ).The framework remains in the form of a single crystal throughout the process.It is worth noting that the metal-ion metathesis approach constructs JLU-Liu40-In/Cu with a significant improvement in thermal stability and gas sorption and separation.展开更多
Solid strong base catalysts have received considerable attention in various organic reactions due to their facile separation,neglectable corrosion,and environmental friendliness.Although great progress has been made i...Solid strong base catalysts have received considerable attention in various organic reactions due to their facile separation,neglectable corrosion,and environmental friendliness.Although great progress has been made in the preparation of solid strong base catalysts,it is still challenging to avoid basic sites aggregation on support and active sites loss in reaction system.Here,we report a tandem redox strategy to prepare Na single atoms on graphene,producing a new kind of solid strong base catalyst(Na1/G).The base precursor NaNO_(3)was first reduced to Na2O by graphene(400℃)and successively to single atoms Na anchored on the graphene vacancies(800℃).Owing to the atomically dispersed of basicity,the resultant catalyst presents high activity toward the transesterification of methanol and ethylene carbonate to synthesize dimethyl carbonate(turnover frequency(TOF)value:125.7 h^(−1)),which is much better than the conventional counterpart Na2O/G and various reported solid strong bases(TOF:1.0-90.1 h^(−1)).Furthermore,thanks to the basicity anchored on graphene,the Na1/G catalyst shows excellent durability during cycling.This work may provide a new direction for the development of solid strong base catalysts.展开更多
基金the National Natural Science Foundation of China(No.22102215)the Fundamental Research Funds for the Central Universities(Nos.21CX06013A and 22CX03001A)the State Key Laboratory of Heavy Oil Processing and the Key Project of China National Key R&D Plan(No.2018YFE0118200).
文摘The fundamental insights of the reaction mechanism,especially the synergistic effect between oxygen vacancies and basic sites,are highly promising yet challenging for Ru-based catalysts during carbon dioxide(CO_(2))methanation.Herein,a series of Rubased catalysts were employed to study the mechanism of CO_(2) methanation.It is found that Ru/CeO_(2) catalyst exhibits a much higher CO_(2) conversion(86%)and CH4 selectivity(100%),as well as excellent stability of 30 h due to the existence of abundant oxygen vacancies and weak basic sites.Additionally,the in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and density functional theory(DFT)calculations reveal that the formate formation step dominated the hydrogenation route on Ru/CeO_(2) catalyst,and the b-HCOO^(*)could be the key intermediate due to b-HCOO^(*)is more easily hydrogenated to methane than m-HCOO^(*).The systematic study marks the significance of precise tailoring of the synergistic relationship between oxygen vacancies and basic sites for achieving the desired performance in CO_(2) methanation.
基金supported by the National Natural Science Foundation of China(21706199,U1662134 and 51861135313)the National Key R&D Program of China(2017YFC1103800)the NRC(Nanostructure Research Centre),Wuhan University of Technology,Wuhan,430070,PR China.
文摘As a typical process-intensive strategy,a tandem reaction driven by a multifunctional catalyst is a paragon of the green catalytic process.Two or more active sites are usually required and their rational spatial distribution is critical for the multi-functional catalyst to act independently or synergistically.Here,we present a simple and stepwise method to construct a trifunctional integrated catalyst simultaneously with spatially intimate acidic(phosphotungstic acid(HPW)),basic(amino)and metal(Pd nanoparticles(NPs))sites in hierarchically porous UiO-66-NH_(2).Through fine controlling the ratio of immobilized HPW and amino groups,we can easily tune its accessible acidic and basic properties,and the anchored HPW molecules can be effectively used to mediate the catalytic performance of Pd NPs and further stabilize the Pd sites.This well-designed integrated catalyst showed excellent catalytic activity and yield(>97%)towards onepot three-step Deacetalization-Knoevenagel-Hydrogenation(D-K-H)catalysis reactions owing to the synergetic catalysis and the intimate spatial arrangement of the acid,basic and metal sites.More importantly,the trifunctional catalyst could be recycled at least five times without significantly losing its activity due to the strong interaction between the MOF and the vip molecules.This work provides some important insights into the construction of multifunctional integrated catalysts,especially for the application in challenging tandem catalysis.
基金financially supported by the National Key R&D Program of China(No.2016YFB0301900)the Science and Technology Support Program of Sichuan Province(No.2015GZ0065)
文摘Ca/SBA-15 solid bases with different Ca/Si atomic ratios were prepared by a one-pot route and employed as catalysts for the production of poly（isosorbide carbonate） （PIC） from diphenyl carbonate and isosorbide via a transesterification polymerization process. The relationship between physicochemical properties and catalytic performance for Ca/SBA-15 in this melt process was investigated by means of various characterization techniques. It was found that basic site amount and strength were responsible for this transesterification process; the weak and medium basic sites inclined to promote polycondensation reaction. It was worth noting that strong basic sites could favor the decomposition of the resultant P/C, resulting in the decrease of weight-average molecular weight （Mw） and yield, and the sample with Ca/Si atomic ratio of 0.4 exhibited the best catalytic performance, giving PIC with Mw of 4.88 × 10^4 g/mol and Tg of 169 ℃ at the optimal conditions. This excellent activity can be ascribed to the presence of rich basic sites and specific basic strength on the surface of 0.4Ca/SBA-15.
基金financially supported by the National Key Technology Pillar Program(No.2013BAC11B05)Key Research and Innovation Program of Jiangsu Province(No.BE2015055)the Science&Technology Pillar Program in Sichuan Province(No.2016GZ0228)
文摘Mg-A1 mixed oxides with different Mg/A1 molar ratio were prepared by thermal decomposition of hydrotalcite-like precursors at 500℃for 5.0 h and used as catalysts for the transesterification of diphenyl carbonate with 1,4-butanediol to synthesize high-molecular-weight poly(butylene carbonate)(PBC).The structure-activity correlations of these catalysts in this transesterification process were discussed by means of various characterization techniques.It was found that the chain growth for the formation of PBC can only be obtained through connecting-OH and-OC(C)OC6H5 end-group upon removing the generated phenol,and the sample with Mg/A1 molar ratio of 4.0 exhibited the best catalytic performance,giving PBC with Mw of 1.64×105 g/mol at 210℃for 3.0 h.This excellent activity depended mainly on the specific surface area and basicity rather than pore structure or crystallite size of MgO.
基金Supported by the National Natural Science Foundation of China(21366004)Guangxi Natural Science Foundation(2016GXNSFFA380015)the Dean Project of Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology(2016Z003)
文摘The Co3O4 and Zr-,Ce-,and La-Co3O4 catalysts were prepared,characterized,and applied to produce CH4 from CO_(2) catalytic hydrogenation in low temperature as 140–220℃.The results indicated that the addition of Zr,Ce,or La to the Co3O4 decreased the crystallite sizes of Co and the outer-shell electron density of Co^3+,and increased the specific surface area,which would provide more active sites for the CO_(2) methanation.Especially,the addition of Zr also changed the reducing state of Co3O4 via an obvious change in the interaction between Co3O4 and ZrO2.Furthermore,Zr doped into the Co3O4 increased the basic intensity of the weak and medium basic sites,as well as the amount of Lewis acid sites,and Bronsted acid sites were also found on the Zr-Co3O4 surface.The introduction of Zr,Ce,or La favored the production of CH4,and the Zr-Co3O4catalyst exhibited the highest CO_(2) conversion(58.2%)and CH4 selectivity(100%)at 200℃,and 0.5 MPa with a gaseous hourly space velocity of 18,000 ml·g^-1(cat)·h^-1,and the catalytic activity of CO_(2) methanation for the Zr-,Ce-,and La-Co3O4 exhibited more stable than Co3O4 in a 20-h reaction.
基金financial support from the National Natural Science Foundation of China(No.21771078 and 21621001)the 111 Project(B17020)+2 种基金the National Key Research and Development Program of China(2016YFB0701100)the Fundamental Research Funds for the Central Universities of Ocean University of China(201813031)the Shandong Province Natural Foundation of China(ZR2019BB033).
文摘A polyhedral metal-organic framework(MOF)JLU-Liu40-In based on dual secondary building units(SBUs)of mononuclear and binuclear paddlewheel indium has been prepared with a nitrogen-rich tetracarboxylic acid ligand under solvothermal conditions.Since the framework possesses large surface areas with multiple polyhedral cages,abundant open metal sites(OMSs)and Lewis basic sites(LBSs),it exhibits high performance for gas adsorption.In addition,through post-synthetic metal-ion metathesis in a single-crystal-to-single-crystal(SCSC)process,JLU-Liu40-In/Cu has been obtained by selectively substituting the paddlewheel In(Ⅲ)ions with Cu(Ⅱ)ions without replacing the mononuclear In(Ⅲ).The framework remains in the form of a single crystal throughout the process.It is worth noting that the metal-ion metathesis approach constructs JLU-Liu40-In/Cu with a significant improvement in thermal stability and gas sorption and separation.
基金the National Science Fund for Distinguished Young Scholars(No.22125804)the National Natural Science Foundation of China(Nos.22078155 and 22178163)the Jiangsu Funding Program for Excellent Postdoctoral Talent.
文摘Solid strong base catalysts have received considerable attention in various organic reactions due to their facile separation,neglectable corrosion,and environmental friendliness.Although great progress has been made in the preparation of solid strong base catalysts,it is still challenging to avoid basic sites aggregation on support and active sites loss in reaction system.Here,we report a tandem redox strategy to prepare Na single atoms on graphene,producing a new kind of solid strong base catalyst(Na1/G).The base precursor NaNO_(3)was first reduced to Na2O by graphene(400℃)and successively to single atoms Na anchored on the graphene vacancies(800℃).Owing to the atomically dispersed of basicity,the resultant catalyst presents high activity toward the transesterification of methanol and ethylene carbonate to synthesize dimethyl carbonate(turnover frequency(TOF)value:125.7 h^(−1)),which is much better than the conventional counterpart Na2O/G and various reported solid strong bases(TOF:1.0-90.1 h^(−1)).Furthermore,thanks to the basicity anchored on graphene,the Na1/G catalyst shows excellent durability during cycling.This work may provide a new direction for the development of solid strong base catalysts.
