Catalysis Today, Vol.351, 125-132, 2020
Reduced oxygen-deficient CuWO4 with Ni catalyzed selective hydrogenolysis of cellulose to ethylene glycol
The effective and selective conversion of cellulose to valuable fuels and chemicals is highly attractive. In this paper, we prepared a catalyst with the adjacent surface Cu degrees and oxygen-deficient WOx (2 < x < 3) species by reduction of CuWO4 precursor, and such catalyst coupled with Ni/activated carbon (AC) attained high yield (71 wt%) and good cycling performances in catalyzing one-step hydrothermal conversion of cellulose to ethylene glycol (EG), highly superior to the performances on physically mixed Ni/C, Cu/C and WO3. The increased Cu doping amounts led to a higher ratio of the lower valence state W (V or IV) to the high valence W(VI) as indicated by XPS, XRD, and TPR-H2 analyses. The oxygen vacancies on the hydrogen-reduced CuWO4 sample dramatically increased, probably due to the benefits from the substantial dissociated H_ on the neighboring Cu degrees center. The EG yields from cellulose are shown to be proportional to the concentrations of oxygen vacancies on WOx, which catalyzes the important elementary retro-aldol step reaction via adsorbing C6 sugar intermediates in a specific way. It is inferred that Cu introduction is mainly used to create more oxygen vacancies on the WOx surface that helps adsorbing oxygenates, while Ni fast hydrogenates of hydroxyacetaldehyde to EG and avoids coking, constructing a multi-functional synergistic catalytic process from converting of cellulose to EG in the high-temperature water.