Synergistic effect of Mo–W carbides on selective hydrodeoxygenation of guaiacol to oxygen-free aromatic hydrocarbons

Abstract

Mo–W carbide was synthesized via temperature-programmed reduction to generate a β-Mo₂C phase with bulk morphology. The catalyst was characterized using X-ray diffraction (XRD), N₂ physisorption, X-ray photoelectron spectroscopy (XPS), H₂-chemisorption, and ammonia temperature programmed desorption (NH₃-TPD) to investigate the synergistic effect of the combination of molybdenum and tungsten in carbide. Due to the interaction of Mo–W, the bimetallic carbide exhibited a significantly higher density of H₂-activating sites than the corresponding monometallic carbides prepared using the same method. In the HDO of guaiacol at 350 °C, MoWC exhibited the highest hydrodeoxygenation (HDO) activity and produced completely deoxygenated products with a selectivity of 92 mol% in which the benzene selectivity was ∼70 mol%. The superior catalytic activity is attributed to the presence of H₂-activating sites and oxophilic sites. Under the testing conditions, the HDO of guaiacol over monometallic molybdenum carbide followed both direct deoxygenation (DDO) and hydrogenation–dehydration (HYD) pathways, while MoWC strongly favored the DDO route. Over 8 h on stream, the catalyst still retained a high catalytic stability.