Bimetal Oxide Catalysts Selectively Catalyze Cellulose to Ethylene Glycol

Abstract

Cellulose is an attractive and potential biomass material in nature. It has been studied for decades to convert it into high value-added chemical materials. In this article, we prepared a unique structure of a yolk–shell catalyst with uniform-sized Pd nanoparticles as the core and easily modified mesoporous silica as the shell, and the shell was modified by alumina and tungsten oxide. The modified Pd@W/Al-MSiO2 yolk–shell-structured nanosphere (YSNS) catalyst showed good catalytic activity in the conversion of cellulose to ethylene glycol: the conversion of cellulose was 96.1%, and the selectivity of ethylene glycol reached 56.5%. From XRD, XPS, and 27Al MAS NMR spectral analysis, it can be seen that the existence of tungsten species would lead to the formation of more extra framework aluminum, which increased the acid strength; meanwhile, aluminum made the tungsten oxide oligomer increase, which increased the dispersion of tungsten species on the catalyst. The interaction of the two metal oxides increased the acidity and the increase in tungsten oxide oligomers were the reasons for the higher selectivity of ethylene glycol. Due to the protective effect of the shell on the Pd nanoparticles, there was no sintering and serious loss of Pd during the reaction, and only small amounts of tungsten and aluminum distributed in the pores and surface were lost. Therefore, the Pd@W/Al-MSiO2 YSNS catalyst maintained 48.5% ethylene glycol selectivity after five cycles.