Study On Cu-ZnO Catalysts For The Hydrogenation Of Methyl Acetate To Ethanol

As a new alternative energy,ethanol attracts more and more attention since it can be a make-up for the petroleum resources to some externd and fulfill the demand of the environmental benign technology.According to the current energy status of China,developing a technology for the synthesis of ethanol from coal is of great significance for maintaining energy security and realizing the diversification of energy resources.As one of the technical routes for the synthesis alcohol from coal,the synthesis route via the carbonylation of dimethyl ether（DME）to methyl acetate（MA）and the subsequent hydrogenation of MA to ethanol has a good industrial prospect because of its high atomic economy and the features of environmentally friendly.At present,Cu-ZnO catalyst is the main catalyst for the hydrogenation of MA to ethanol,which shows high catalytic performance and stability.However,how to further improve the activity of the catalyst by increasing the dispersion of Cu and Zn species is still a difficult challenge.Besides that,the discussion on the interaction between Cu and ZnO species is still not enough in the hydrogenation of MA.Based on the above research status,this work proposed an effective CuZn-SiO₂ catalyst prepared by hydrolysis precipitation（HP）method,which has achieved the high dispersion of Cu and ZnO species,and the Cu-ZnO interaction has also been discussed.What’s more,a nanoflower-like Cu-ZnO catalyst has also proposed and prepared by hydrothermal method,which exhibited improved catalytic performance.These results provided a new way to design highly effective Cu-ZnO catalysts.Compared to Cu-SiO₂ catalyst,the dispersion of the Cu species on the CuZn-SiO₂ bimetallic catalyst prepared by HP method has an obvious improvement,which is ascribed to the strong interaction between metal species and silica support caused by the pseudo-homogeneous reaction during the mixing process.Besides that,the CuZn-SiO₂ bimetallic catalyst with 30 wt.%Cu and a Cu/Zn ratio of 9:1 achieved the highest activity,which is 1.3 times the activity of best Cu/ZnO catalyst reported in literature.Moreover,the results provide a new idea for the design of highly dispersed bimetallic catalysts.By modulating the proportion of Cu and Zn in CuZn-SiO₂ catalyst,it was found that the addition of ZnO impeded the formation of copper phyllosilicate and promoted the production of more Cu-ZnO_x species.The cooperative effect of the two aspects changed the valence distribution of copper species on the surface of catalyst.Besides that,the linear correlation between the TOF（Cu⁺）and Zn/Cu ratio indicated that the Cu⁺site derived from the strong interaction between copper and zinc species has higher activity in ester hydrogenation.This work has also proposed a new nanoflower-like Cu-ZnO catalyst prepared by hydrothermal method.Compared to the Cu-ZnO catalysts prepared by coprecipitation and ammonia evaporation method,nanoflower-like Cu-ZnO catalyst exhibited higher catalytic performance.The specific hydrothermal condition of nanoflower-like Cu-ZnO catalyst not only promoted the dispersion of Cu species,but also enhanced the strong interaction between Cu and ZnO species.Thus,the formation of copper species with appropriate Cu⁺/Cu⁰ ratio was prompted,which contributed to the superior catalytic performance of the catalyst.