Role of ZnO in Cu/ZnO/Al2O3 catalyst for hydrogenolysis of butyl butyrate

For hydrogenolysis of butyl butyrate (BB), a series of Cu/ZnO/Al2O3 catalysts with different metal compositions were prepared, and characterized by N2O chemisorption for measuring Cu surface area and by chromatographic experiment for determining the heat of BB adsorption. As a result, the presence of ZnO in Cu-based catalysts was found to enhance the catalytic activity of Cu due to dual function of ZnO. The Cu surface area was linearly correlated with the butanol productivity, demonstrating that ZnO exerts the structural function in Cu/ZnO/Al2O3 catalysts. Additionally, the role of ZnO as a chemical contributor was revealed such that its presence leads to lower activation energy of the surface reaction, thus resulting in higher Cu catalytic activity obtained at a low temperature such as 200 °C. Consequently, optimizing the Cu/Zn ratio in Cu/ZnO/Al2O3 catalyst is required to tune its structural and chemical characteristics of Cu metals, and thus to obtain a higher activity on the hydrogenolysis reaction.

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► The presence of ZnO in Cu-based catalysts enhances the Cu activity in the reaction.
► ZnO acts as both a structural and a chemical promoter in Cu/ZnO/Al2O3 catalysts.
► Optimizing the Cu/Zn ratio in the catalyst is required to obtain a higher activity.