High dispersed Mo2C/AC for gas-phase catalytic direct deoxygenation during lignin pyrolysis

Abstract

Lignin pyrolysis can efficiently produce renewable aromatic hydrocarbons, but the selective cleavage of lignin C-O bonds and the inhibition of intermediate polycondensation in solvent-free systems remain significant challenges. This work proposes a strategy coupling gas-phase lignin pyrolysis with online hydrodeoxygenation, employing high dispersed Mo2C to achieve targeted deoxygenation of lignin toward aromatics. Mo2C/AC exhibits high direct deoxygenation selectivity over a wide temperature range (300-500 ℃), which facilitates selective C-O bond cleavage while inhibiting catalyst coking and aromatic ring cracking. The aromatic hydrocarbon yield from guaiacol reached as high as 93 mol%, with 100% selectivity. Specifically, Mo2C effectively mitigates the high-temperature condensation of guaiacol by removing oxygen-containing groups, thereby inhibiting the formation of oligomers. Compared with traditional zeolite-catalysed lignin pyrolysis at the same temperature, the yield of monocyclic aromatic hydrocarbons increased by 344%, while coke formation was reduced to only 20% of the original level. After birch lignin pyrolysis coupled with hydrodeoxygenation, the yield of monomeric aromatic hydrocarbons can reach up to 11.3 wt.%. This study achieves selective deoxygenation of lignin in the gas phase at low temperature while significantly suppressing catalyst coking, offering a viable strategy for efficient solvent-free lignin conversion.