Preparation Of Copper-Palladium Bimetallic Catalyst And Study On Catalytic Hydrogenation-Dehydrogenation Coupling Reaction

In recent years,the increasing depletion of resources and environmental degradation caused by the massive use of fossil energy has accelerated the speed of human research in searching for renewable alternative energy sources.Biomass energy has become a research hotspot in recent years because the advantages of widely available and cheap.Among them,the catalytic hydrogenation and dehydrogenation reactions of related derivatives play a very important position in the chemical industry.However,the separate furfural hydrogenation and cyclohexanol dehydrogenation processes there are some disadvantages in above derivatives.For examples,traditional furfural hydrogenation process consumes relatively high hydrogen energy and alone cyclohexanol dehydrogenation reaction also has some problems such as the limitation of thermodynamic equilibrium and the higher temperature required for the reaction.Therefore,given the above-mentioned series of problems,the development of a new coupling reaction process that combines dehydrogenation and hydrogenation reactions has important scientific significance and economic value for promoting the development of our country’s fine chemical industry and green chemistry.In this work,the silica-copper gel was prepared by the sol-gel method,and the Cu O/SiO₂ composite oxide was obtained by drying and roasting.Then,the metal palladium was loaded on the composite oxide by the isometric impregnation method,and finally in a hydrogen atmosphere.Pd-Cu/SiO₂ catalyst was obtained by lower reduction.Various characterization methods were used to investigate the structural characteristics of the Pd-Cu/SiO₂ catalyst.At the same time,we systematically investigated the influences of various factors on the coupled dehydrogenation-hydrogenation reaction and determined the optimal conditions for the reaction.In this work,the Pd-Cu/SiO₂ catalyst was investigated through a variety of analysis and characterization methods.The results said that the catalyst prepared with citric acid as the template has the largest pore size and a higher specific surface area.The Cu species and Pd species in the catalyst are uniformly dispersed on the SiO₂ support in a random block shape.The catalyst is weakly acidic as a whole.The Cu species in the catalyst coexist in the form of Cu⁰ and Cu⁺,and there is a Si-O-Cu structure,which confirms that there is a strong interaction between the active component Cu and the support SiO₂.The introduction of Pd can enhance the interaction and also enhance the active hydrogen transfer ability form Cu⁰to Cu⁺.Thereby Pd can improve the catalytic activity of the catalyst.The various parameters of the catalyst can reach the goal designed during its synthesis.In this work,we systematically investigated some factors’effect on the dehydrogenation hydrogenation coupling reaction.Such as the active metal component load in catalyst,catalyst quality,different noble metal species loaded on the catalyst,different templates,different reaction solvents,different hydrogen sources,reaction temperature,reaction time and different ratio of furfural and cyclohexanol.Experimental exploration shows that in the best coupling reaction conditions are 0.5%Pd-15%Cu/SiO₂ is used as the catalyst,cyclohexanol is used as hydrogen source,the methanol is used as solvent,the temperature is 195℃,the reaction time is 10 h,the molar ratio of furfural and cyclohexanol is 1:3.In addition,it is found through the catalyst cycle experiment that the catalyst has relatively excellent repeatability and stability.This work combines the two industrially important reactions of furfural hydrogenation and cyclohexanol dehydrogenation to form a new dehydrogenation-hydrogenation coupling reaction process,which is suitable for hydrogenation without external hydrogen as a hydrogen source.The research of hydrogen reaction has certain reference value.