Comparative Study of the Effect of Water on Cu/SiO2Catalysts Prepared by Different Methods: Structure, Hydrogenation Performance and the Promotion of Reduction Cu+to Cu0

The effect of water on the performance of Cu/SiO(2)catalysts prepared by four different methods was investigated by ethyl acetate (AcOEt) hydrogenation to ethanol (EtOH). The catalysts were characterized using XRD, FT-IR, TPR, N2O titration, TEM and XPS to understand the structure-catalytic efficiency relationships. The results showed high copper species dispersion and strong interaction between copper and silica were responsible for water-tolerant hydrogenation performance of catalysts. Interestingly, although water oxidized slightly Cu(0)or Cu(+)to Cu(2+)in the reaction, it maybe promote the reduction of Cu(+)to Cu-0. Notably, the Cu(+)content of spent catalysts at condition with water decreased in comparison with that of spent catalysts at condition without water. This might be because that water formed film on Cu2O surface by adsorbing, which enhanced the spillover of dissociated H from Cu(0)to Cu(+)sites and then promoted its reduction.