Effect of the ZnO/SiO2 ratio on the structure and catalytic activity of Cu/SiO2 and Cu/ZnO catalysts in water-containing ester hydrogenation

Abstract

The effects of the ZnO/SiO₂ ratio on the water tolerance of Cu/SiO₂ and Cu/ZnO catalysts were studied by ethyl acetate with 5 wt% water hydrogenation. Notably, the addition of an appropriate amount of ZnO endows Cu/SiO₂ catalysts with satisfactory water-tolerant hydrogenation performance by a decrease in the reaction temperature without sacrificing conversion. At the same time, agglomeration can be alleviated for Cu/ZnO catalysts due to the optimal addition of SiO₂, which is considered as a partition material that effectively hinders the agglomeration of the Cu/ZnO catalyst. However, the addition of ZnO was not favourable for the copper dispersion of Cu/SiO₂. The stability of Cu/SiO₂ catalyst quickly degraded due to excessive ZnO being introduced by sintering. The copper dispersion of Cu/ZnO catalysts initially increased with increasing SiO₂ content, but then decreased. The addition of excess SiO₂ also led to decreased activity and rapid deactivation of the Cu/ZnO catalyst. In our study, the appropriate addition of ZnO (5 wt%) and SiO₂ (5 wt%) had a positive effect on the Cu/SiO₂ and Cu/ZnO catalysts, respectively.