Support effects in the de-methoxylation of lignin monomer 4-propylguaiacol over molybdenum-based catalysts

Abstract De-methoxylation of lignin-derived 4-propylguaiacol over molybdenum oxide catalysts on five common supports (SiO2, CeO2, Al2O3, TiO2 and active carbon (AC)) is investigated in a flow system. TEM, H2-TPR and TGA characterizations are conducted to understand the structural features of these Mo catalysts. Positive correlations between electronegativity of the cation in the support and catalyst activity is established, i.e., catalyst support with high cation electronegativity such as Si best promote the conversion of 4-propyiguaicaol into 4-propylphenol. Following this discovery, we further investigated the effect MoO3 loading on SiO2 and the reaction conditions to identify the most suitable parameters for the de-methoxylation of 4-propylguaiacol. The optimized MoO3/SiO2 catalyst constantly afforded >80% selectivity towards 4-propylphenol at >60% conversion for >10 h, and the lost activity could be regenerated by removing coke via simple high temperature calcination.