Preparation Of Silicon Oxide Supported Copper Catalyats And Catalytic Performance Of Methanol Dehydrogenation To Methyl Formate

Methyl formate（MF）with aldehyde group and ester group can be used to synthesize many highly valuable chemical products,such as formic acid,ethylene glycol,dimethyl carbonate,formamide.In addition,MF is also used in pharmaceutical,pesticide,leather,dyes and rubber industries.The methanol dehydrogenation to MF is deemed to have great development prospects in the chemical industry on account of important merits including abundant raw materials,simple procedures and pollution-free.Catalyst is the key of this technology.Compared with noble metal-based（Pt,Pd）,Cu-based catalysts are widely used in catalytic reaction due to its low price,simple procedures and high catalytic activity.Nevertheless,low yield and poor stability are problems of catalyst that must be considered in methanol dehydrogenation.Therefore,design and synthesis of Cu-based catalysts with excellent activity and stability is the focus of researchers in this field..In this paper,from the viewpoint of improving the catalytic activity and stability of the catalyst,the hierarchical porous Cu-based catalysts（x-Cu/HPS）and ordered mesoporous Cu-Zn complex catalysts（x-CuZn/SiO₂）were prepared and their catalytic performance in methanol dehydrogenation was studied.And the properties displayed by the various catalysts were explained and the structure-activity was investigated.The main contents and findings of this paper are as follows:（1）Ordered hierarchical porous silica（x-HPS）was prepared by hydrothermal synthesis with F127 as template at different hydrothermal temperature.The results showed that x-HPS supports own large specific surface area(～300-500m²·g^-1)and uniform ordered micro-mesoporous,facilitating for the dispersion of Cu active component.（2）x-Cu/HPS and 130-Cu/HPS-W catalysts were prepared by ammonia-evaporation method and double-solvent impregnation method using x-HPS as supports,respectively.The effects of preparation methods on the structure and surface properties of the catalyst were studied in detail.It could be found that catalysts prepared by ammonia-evaporation method owned higher dispersion of Cu species and better catalytic activity than that by double-solvent impregnation method.Among them,130-Cu/HPS exhibited the best activity,which was ascribed to ordered hierarchical porous and larger specific surface area,promoting to disperse and anchor Cu nanoparticles,reduce Cu crystalline size and increase Cu⁰ content.（3）A series of xCuZn/SiO₂ catalysts were prepared by introducing different amounts of Zn into Cu/SiO₂ obtained by ammonia-evaporation method.The effect of Zn promoter on catalytic performance of methanol dehydrogenation was investigated.It was found that the catalytic activity was enhanced markedly at different degree after introduction of Zn.Among them,20Cu Zn/SiO₂ exhibited the highest catalytic activity with methanol conversion of44.5%and MF selectivity of 92.7%.The main reason lied in the presence of Cu-ZnO interaction in xCuZn/SiO₂ catalysts deduced,which will effectively regulate and increase the content of Cu⁰,thus improving the catalytic activity of methanol dehydrogenation.In addition,it is worth mentioning that the introduction of Zn can also promote the dispersion of active component Cu.（4）The stability of the catalyst was evaluated in methanol dehydrogenation reaction for 60h.Compared with Cu/SiO₂,20CuZn/SiO₂ catalysts exhibited better stability,which is mainly due to Cu-ZnO interaction effectively inhibiting Cu agglomeration and sintering.