Relevant aspects of the conversion of guaiacol as a model compound for bio-oil over supported molybdenum oxycarbide catalysts

Abstract

Molybdenum supported over activated carbon has been carburized under carbothermal hydrogen reduction conditions at different temperatures in order to modify the carburization degree. The resulting catalysts were characterized by N₂ physisorption, CO chemisorption, XPS, TPR, and TPD-NH₃ and compared in the hydrodeoxygenation of guaiacol in a batch reactor as a lignin-derived model compound. The results have shown that the CO produced during the TPR could be related to the CO chemisorbed and the carburization degree of the material. The carburization degree was shown to increase with the final temperature, and under such conditions, two different Mo species, Mo⁴⁺ and Mo³⁺, were identified in the oxycarbide phase. Catalytic results showed that the Mo₂C is less active than the oxycarbide MoO_xC_y phase. Mo₂C showed to improvement in the transalkylation reactions while in the case of MoO_xC_y, Mo⁴⁺ promotes the hydrogenolysis of catechol to benzene while the Mo³⁺ species was shown to activate hydrogenation reactions.