Selective Demethoxylation of Lignin-Derived Methoxyphenols to Phenols over Lignin-Derived-Biochar-Supported Mo2C Catalysts

Hydrodeoxygenation (HDO) can convert methoxyphenols in lignin-derived bio-oil to phenols, a precursor of biofuels. In this work, Mo2C/C catalysts were prepared with lignin-derived biochar as a carbon source for the HDO reaction of guaiacol. The carburization degree of catalyst precursors was tuned by varying the carburization temperature and activation method, thus affecting the activity of the catalyst. Higher carburization temperatures promoted the formation of active Mo2C species at the expense of inactive MoOx and MoSx species. In addition to the high carburization temperature (800 °C), biochar also needed to be activated by H3PO4, HNO3, or a two-step process to obtain Mo2C species. The use of hydrocarbon solvents could reduce the competitive adsorption of the solvent over reactants while inhibiting the side reactions involving solvents, such as alkylation and etherification. Optimized 12.5Mo2C/C–H3PO4 (800) offered a high guaiacol conversion of 98.7% and a phenol yield of 66.8% under the optimum conditions. The yield of methanol was as high as 39.5%, indicating that the demethoxylation reaction was dominant. The catalytic system also exhibited high activity for the HDO of other lignin-derived methoxyphenols to produce phenols.