Bifunctionality of Cu/ZnO catalysts for alcohol-assisted low-temperature methanol synthesis from syngas: Effect of copper content

摘要

Alcohol-assisted low-temperature methanol synthesis was conducted over Cu/ZnO_X catalysts while varying the copper content (X).Unlike conventional methanol synthesis,ethanol acted as both solvent and reaction intermediate in this reaction,creating a different reaction pathway.The formation of crystalline phases and characteristic morphology of the co-precipitated precursors during the co-precipitation step were important factors in obtaining an efficient Cu/ZnO catalyst with a high dispersion of metallic copper,which is one of the main active sites for methanol synthesis.The acidic properties of the Cu/ZnO catalyst were also revealed as important factors,since alcohol esterification is considered the rate-limiting step in alcohol-assisted low-temperature methanol synthesis.As a consequence,bifunctionality of the Cu/ZnO catalyst such as metallic copper and acidic properties was required for this reaction.In this respect,the copper content (X) strongly affected the catalytic activity of the Cu/ZnO_X catalysts,and accordingly,the Cu/ZnO_0.5 catalyst with a high copper dispersion and sufficient acid sites exhibited the best catalytic performance in this reaction.