Direct aldol condensation of various aromatic, heteroaromatic, α,β-unsaturated aldehydes and aliphatic aldehydes with acyldiazomethane was realized using Mgl2 etherate （Mgl2.（Et2O）n） as a promoter in the presenc...Direct aldol condensation of various aromatic, heteroaromatic, α,β-unsaturated aldehydes and aliphatic aldehydes with acyldiazomethane was realized using Mgl2 etherate （Mgl2.（Et2O）n） as a promoter in the presence of diisopropyl amine （DIPEA） in excellent yields in a short time under mild conditions with high chemoselectivity. Iodide counterion, and a non-coordinating less ploar reaction media （i.e., CH2C12） are among the critical factors for this unique reactivity.展开更多
Regioselective addition reactions of silyl enolates to a, b-unsaturated aldehyde and its acetal catalyzed by MgI2 etherate give aldol adducts (1, 2-addition) preferentially over Michael adducts (1, 4-addition). This ...Regioselective addition reactions of silyl enolates to a, b-unsaturated aldehyde and its acetal catalyzed by MgI2 etherate give aldol adducts (1, 2-addition) preferentially over Michael adducts (1, 4-addition). This unique regioselectivity is distinctly different with other Lewis acidic promoters and may be attributed to the high oxyphilicity of IMg+.展开更多
Herein,one-pot chemocatalytic conversion of xylose to value-added C_(5)/C_(4) cyclic ethers over a novel ZrO_(2)-doped Ni-Pd catalyst supported on H-βzeolite was demonstrated.Optimized catalyst,namely,Ni_(2) Pd_(0.5)...Herein,one-pot chemocatalytic conversion of xylose to value-added C_(5)/C_(4) cyclic ethers over a novel ZrO_(2)-doped Ni-Pd catalyst supported on H-βzeolite was demonstrated.Optimized catalyst,namely,Ni_(2) Pd_(0.5)Zr_(1)/H-β(25),achieved a high xylose transformation(>99%)with high selectivities toward 2-methyltetrahydrofuran(48.6%)and tetrahydropyran(20.2%)under mild reaction conditions(200℃,1.0 MPa H_(2),and 2 h).Systematic investigation of the physicochemical properties of the catalyst revealed that ZrO_(2) doping induced O vacancies,enhanced H_(2) activation,and improved metal dispersion,thereby promoting hydrogenation and hydrodeoxygenation.In situ diffuse reflectance infrared Fourier transform spectroscopy using furfural and furfuryl alcohol probes confirmed preferential adsorption geometries and electronic interactions at metal-ZrO_(2) interfaces.Time-resolved and feedstock variation studies further elucidated the reaction mechanism and highlighted the roles of key intermediates.The proposed catalyst exhibited excellent recyclability with only a minor decline in performance after multiple xylose conversion cycles.This study provides mechanistic insights and design principles for the development of efficient multifunctional catalysts for biomass valorization.展开更多
The structure-performance relationship of Cu/Al_(2)O_(3) catalysts in the hydrogenation of diethyl oxalate(DEO)for the synthesis of alcohol ether esters has been investigated by various characterization techniques inc...The structure-performance relationship of Cu/Al_(2)O_(3) catalysts in the hydrogenation of diethyl oxalate(DEO)for the synthesis of alcohol ether esters has been investigated by various characterization techniques including XRD,XPS,N2O titration,and 27Al MAS-NMR.The results showed that when the crystal configurations of Al_(2)O_(3) were the same,increasing the specific surface area could effectively refine the size of copper nanoparticles(Cu NPs),and ultimately improve the conversion of DEO.Meanwhile,the smaller size ofγ-Al_(2)O_(3)(HSAl and SBAl)loaded Cu NPs promotes the reaction towards the deep hydrogenation to produce ethanol(EtOH)and ethylene glycol(EG).Besides,the larger size of Cu NPs on the surface of amorphous Al_(2)O_(3)(HTAl and SolAl)resulted in a lower conversion rate,where ethyl glycolate(Egly)is the main product.Despite there are differences in Al^(3+)ionic coordination in Al_(2)O_(3) with different crystal structures,the experimental data showed that the differences in Al^(3+)ionic coordination did not significantly affect the catalytic performance in the hydrogenation reaction.The formation of alcohol-ether ester chemicals is critically dependent on the interactions between Cu sites and acidic sites.Among them,EG and EtOH were dehydrated to form 2-ethoxyethanol via the SN2 mechanism,while Egly and EtOH were reacted to form ethyl ethoxyacetate(EEA)via the SN2 mechanism.This study provides a theoretical basis for the optimization of the coal-based glycol processes to achieve a diversified product portfolio.展开更多
The use of fossil fuels significantly contributes to excess CO_(2) emissions.Catalytic hydrogenation of CO_(2) to dimethyl ether(DME)is an effective method for CO_(2) recycling,offering both environmental and economic...The use of fossil fuels significantly contributes to excess CO_(2) emissions.Catalytic hydrogenation of CO_(2) to dimethyl ether(DME)is an effective method for CO_(2) recycling,offering both environmental and economic benefits.Zeolites,known for their efficiency as solid catalysts,are widely utilized in the chemical industries.Bifunctional catalysts based on zeolites have gained attention for their applications in CO_(2) hydrogenation to DME.This review discusses key factors affecting the catalytic performance of zeolites,including topologies,Si/Al ratio,crystal size,and the proximity of metallic species to the zeolite catalysts.Although bifunctional catalytic systems enhance the conversion of CO_(2) to DME,they also lead to high CO selectivity at elevated temperatures,which can limit both DME yield and selectivity.We present recent advancements in the development of bifunctional catalysts for the direct hydrogenation of CO_(2) to DME,providing insights for designing optimized catalysts for tandem reaction systems.展开更多
Catalytic aryl ether C—O bonds hydrogenolysis was an important route to convert lignite into high valueadded chemicals.Solid super acid 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalysts were successfully synthesized and evalua...Catalytic aryl ether C—O bonds hydrogenolysis was an important route to convert lignite into high valueadded chemicals.Solid super acid 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalysts were successfully synthesized and evaluated their performance in catalytic hydrolysis of lignite derivatives.The excellent performance of 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) stems from the synergistic interaction between metallic and acidic sites.Specifically,the acidic sites generated by S_(2)O_(8)^(2-) facilitate the adsorption of O atoms in the substrate,whereas the metal sites optimize the process of hydrogen adsorption and activation and promote the generation of hydrogen radicals,which further enhances the ability to break C—O bonds.Thus,10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) exhibits more significantcatalytic activity compared to 10%Ni-ZrO_(2) prepared from pure ZrO_(2) as a support.Characterization results showed that the 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalyst prepared by sodium borohydride reduction method presented a uniform pore structure,which effectively promoted the dispersion of metal Ni on the catalyst surface.Complete conversion of diphenyl ether(DPE)can be achieved under relatively mild conditions,and excellent hydrogenolysis activity is also demonstrated for other lignite derivatives containing C—O bonds.The possible reaction mechanism of DPE hydrogenolysis in the H_(2)-isopropanol system was investigated.This work represents a significantstep forward in the design of highly efficientsolid super acid catalysts.展开更多
基金the National Natural Science Foundation of China (Nos. 21372203 and 21272076)for the financial support
文摘Direct aldol condensation of various aromatic, heteroaromatic, α,β-unsaturated aldehydes and aliphatic aldehydes with acyldiazomethane was realized using Mgl2 etherate （Mgl2.（Et2O）n） as a promoter in the presence of diisopropyl amine （DIPEA） in excellent yields in a short time under mild conditions with high chemoselectivity. Iodide counterion, and a non-coordinating less ploar reaction media （i.e., CH2C12） are among the critical factors for this unique reactivity.
基金We are grateful for the financial supports from the National Outstanding Youth Fund No.29925204)the Foundation for University Key Teacher by the Ministry of Education of Chinaa Visiting Fund of the National Laboratory of Applied Organic Chemistry.
文摘Regioselective addition reactions of silyl enolates to a, b-unsaturated aldehyde and its acetal catalyzed by MgI2 etherate give aldol adducts (1, 2-addition) preferentially over Michael adducts (1, 4-addition). This unique regioselectivity is distinctly different with other Lewis acidic promoters and may be attributed to the high oxyphilicity of IMg+.
基金supported by the Bio&Medical Technology Development Program(no.RS-2022-NR067354)established by the National Research Foundation(NRF)funded by the Korean Ministry of Science and ICT(MSIT)+2 种基金an NRF grant funded by the Korean MSIT(no.RS-2023-00261322)Additional support from the Korea Institute of Energy Technology Evaluation and Planning(KETEP)the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea(RS-2024-00469587)was also appreciated。
文摘Herein,one-pot chemocatalytic conversion of xylose to value-added C_(5)/C_(4) cyclic ethers over a novel ZrO_(2)-doped Ni-Pd catalyst supported on H-βzeolite was demonstrated.Optimized catalyst,namely,Ni_(2) Pd_(0.5)Zr_(1)/H-β(25),achieved a high xylose transformation(>99%)with high selectivities toward 2-methyltetrahydrofuran(48.6%)and tetrahydropyran(20.2%)under mild reaction conditions(200℃,1.0 MPa H_(2),and 2 h).Systematic investigation of the physicochemical properties of the catalyst revealed that ZrO_(2) doping induced O vacancies,enhanced H_(2) activation,and improved metal dispersion,thereby promoting hydrogenation and hydrodeoxygenation.In situ diffuse reflectance infrared Fourier transform spectroscopy using furfural and furfuryl alcohol probes confirmed preferential adsorption geometries and electronic interactions at metal-ZrO_(2) interfaces.Time-resolved and feedstock variation studies further elucidated the reaction mechanism and highlighted the roles of key intermediates.The proposed catalyst exhibited excellent recyclability with only a minor decline in performance after multiple xylose conversion cycles.This study provides mechanistic insights and design principles for the development of efficient multifunctional catalysts for biomass valorization.
文摘The structure-performance relationship of Cu/Al_(2)O_(3) catalysts in the hydrogenation of diethyl oxalate(DEO)for the synthesis of alcohol ether esters has been investigated by various characterization techniques including XRD,XPS,N2O titration,and 27Al MAS-NMR.The results showed that when the crystal configurations of Al_(2)O_(3) were the same,increasing the specific surface area could effectively refine the size of copper nanoparticles(Cu NPs),and ultimately improve the conversion of DEO.Meanwhile,the smaller size ofγ-Al_(2)O_(3)(HSAl and SBAl)loaded Cu NPs promotes the reaction towards the deep hydrogenation to produce ethanol(EtOH)and ethylene glycol(EG).Besides,the larger size of Cu NPs on the surface of amorphous Al_(2)O_(3)(HTAl and SolAl)resulted in a lower conversion rate,where ethyl glycolate(Egly)is the main product.Despite there are differences in Al^(3+)ionic coordination in Al_(2)O_(3) with different crystal structures,the experimental data showed that the differences in Al^(3+)ionic coordination did not significantly affect the catalytic performance in the hydrogenation reaction.The formation of alcohol-ether ester chemicals is critically dependent on the interactions between Cu sites and acidic sites.Among them,EG and EtOH were dehydrated to form 2-ethoxyethanol via the SN2 mechanism,while Egly and EtOH were reacted to form ethyl ethoxyacetate(EEA)via the SN2 mechanism.This study provides a theoretical basis for the optimization of the coal-based glycol processes to achieve a diversified product portfolio.
基金the National Key Research and Development Program of China(2021YFA1500401)the National Natural Science Foundation of China(22288101)the‘111 Center’(B17020)for supporting this work.
文摘The use of fossil fuels significantly contributes to excess CO_(2) emissions.Catalytic hydrogenation of CO_(2) to dimethyl ether(DME)is an effective method for CO_(2) recycling,offering both environmental and economic benefits.Zeolites,known for their efficiency as solid catalysts,are widely utilized in the chemical industries.Bifunctional catalysts based on zeolites have gained attention for their applications in CO_(2) hydrogenation to DME.This review discusses key factors affecting the catalytic performance of zeolites,including topologies,Si/Al ratio,crystal size,and the proximity of metallic species to the zeolite catalysts.Although bifunctional catalytic systems enhance the conversion of CO_(2) to DME,they also lead to high CO selectivity at elevated temperatures,which can limit both DME yield and selectivity.We present recent advancements in the development of bifunctional catalysts for the direct hydrogenation of CO_(2) to DME,providing insights for designing optimized catalysts for tandem reaction systems.
基金supported by the National Key Research and Development Program of China(2022YFB4101100)the National Natural Science Foundation of China(22178375 and 22478414)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Catalytic aryl ether C—O bonds hydrogenolysis was an important route to convert lignite into high valueadded chemicals.Solid super acid 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalysts were successfully synthesized and evaluated their performance in catalytic hydrolysis of lignite derivatives.The excellent performance of 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) stems from the synergistic interaction between metallic and acidic sites.Specifically,the acidic sites generated by S_(2)O_(8)^(2-) facilitate the adsorption of O atoms in the substrate,whereas the metal sites optimize the process of hydrogen adsorption and activation and promote the generation of hydrogen radicals,which further enhances the ability to break C—O bonds.Thus,10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) exhibits more significantcatalytic activity compared to 10%Ni-ZrO_(2) prepared from pure ZrO_(2) as a support.Characterization results showed that the 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalyst prepared by sodium borohydride reduction method presented a uniform pore structure,which effectively promoted the dispersion of metal Ni on the catalyst surface.Complete conversion of diphenyl ether(DPE)can be achieved under relatively mild conditions,and excellent hydrogenolysis activity is also demonstrated for other lignite derivatives containing C—O bonds.The possible reaction mechanism of DPE hydrogenolysis in the H_(2)-isopropanol system was investigated.This work represents a significantstep forward in the design of highly efficientsolid super acid catalysts.
