Insight into the deactivation mechanism of water on active Cu species for ester hydrogenation: Experimental and theoretical study

Abstract

Water is inevitably existed in the industrial production and counted as a critical issue; however, the effect of water on Cu/SiO2 catalysts was often ignored and the relation between of water and deactivation mechanism in the hydrogenation reaction is rarely studied. In this work, the effect of water on ester hydrogenation was investigated experimentally and theoretically. The hydrogenation of ethyl acetate was chosen as probe reaction and the reagent containing water was used to simulate industrial feedstock. The obtained experimental results of the hydrogenation and the in-situ DRIFT and DFT calculation have demonstrated that the presence of water is hardly affected ethanol selectivity but decreased the catalytic activity. The main reason for the showed catalyst deactivation is the competitive adsorption (reversible) mechanism of water and ethyl acetate molecules. More precisely, the active species of Cu+ surface is preferred the adsorption of H2O over ethyl acetate molecule consequently leads to a rapidly decreasing in the conversion ratio of ethyl acetate. Although the adsorption of water molecule is only occupied the Cu+ sites in the catalyst and could also release at reaction temperature, the conversion was partially recovered due to the growth, leaching and oxidation of copper species caused by water when water was removed.