Preparation of Carbon-Supported Tungsten Carbides: Comparative Determination of Surface Composition and Influence on Cellulose Transformation into Glycols

The chemical valorization of lignocellulosic biomass is of fundamental importance for the sustainable production of chemicals. Among them ethylene and propylene glycols are useful products that can be obtained from lignocellulose using heterogeneous catalysts. It has been reported that catalysts composed of supported Ni and W carbides promote this transformation. We intend in this article to bring new insights by reporting a deep investigation of Ni-WxC/AC (x=1 or 2) materials, including the preparation modes, the comparison of the surface species composition and their impact on the catalytic cellulose hydrogenolysis into ethylene and propylene glycol. The composition of materials obtained by the preparation mode consisting in the co-impregnation of W and Ni on the carbon support was influenced by the amount of W and Ni. It appears that a catalyst composed of 5 wt% Ni and 30 wt% of W allowed the formation of a material presenting only the W2C phase and two alloys Ni3W17 and Ni6W6C. The preparation mode consisting in forming WxC phases on the carbon support before Ni impregnation allowed the selective formation of W2C/AC or WC/AC depending on the carburization conditions. The catalyst prepared by the co-impregnation showed the most important synergetic effect between Ni and W sites leading to high yields into ethylene and propylene glycol from cellulose, hemicellulose or pine wood. In addition, this catalyst showed a much higher stability with a good reusability.