Uniformly Dispersed Cu Nanoparticles over Mesoporous Silica as a Highly Selective and Recyclable Ethanol Dehydrogenation Catalyst

Abstract

Selective dehydrogenation of ethanol to acetaldehyde has been considered as an important pathway to produce acetaldehyde due to the atom economy and easy separation of acetaldehyde and hydrogen. Copper catalysts have attracted much attention due to the high activity of Cu species in O-H and C-H bonds oxidative cleavage, and low process cost; however, the size of the Cu nanoparticle is difficult to control since it is easily suffers from metal sintering at high temperatures. In this work, the Cu/KIT-6 catalyst exhibited an ultra-high metal dispersion of 62.3% prepared by an electrostatic adsorption method, due to the advantages of the confinement effect of mesoporous nanostructures and the protective effect of ammonia water on Cu nanoparticles. The existence of an oxidation atmosphere had a significant effect on the valence state of copper species and enhancing moderate acid sites. The catalyst treated by reduction and then oxidation possessed a moderate/weak acid site ratio of ~0.42 and a suitable proportion of Cu+/Cu0 ratio of ~0.53, which conceivably rendered its superior ethanol conversion of 96.8% and full acetaldehyde selectivity at 250 °C. The catalyst also maintained a high selectivity of >99% to acetaldehyde upon time-on-stream of 288 h.