Enhanced Targeted Deoxygenation Catalytic Pyrolysis of Lignin to Aromatic Hydrocarbons over Oxygen Vacancies Pt-MoOx/TiO2

Abstract

Catalytic pyrolysis technology has been widely used in the conversion of lignin to aromatics, but the catalysts still suffer from poor stability and low product yields due to the lack of oxygen vacancy design. In this study, we report a multi-active site synergistic strategy to enhance the cleavage of lignin aryl carbon-oxygen bonds. Pt-MoO_x/TiO₂ has a large specific surface area and pore volume, showing a significant medium mesopore size, which was favorable for trapping macromolecular oxides. Meanwhile, a significant synergistic effect was found between hydrogen-activated metallic Pt and molybdenum oxide, which both inhibited the hydrogenation of the aryl ring and promoted the dissociation of hydrogen, thus providing more active sites. More importantly, the defective oxygen vacancies played a key role in the adsorption and activation of oxygen-containing groups, facilitating the absorption of active hydrogen formed by hydrogen spillover. Under the conditions of atmospheric pressure and 400 °C, the high efficiency conversion (100%) of m-cresol was achieved, and guaranteed a high yield of aromatics (98%) and high selectivity (98%). Extending to lignin, the yield of aromatics can reach 5 wt.%. The catalyst remained highly active after 6 h of continuous operation, and there was no significant decrease in yield after two regenerations.