Catalytic fast pyrolysis of enzymatic hydrolysis lignin over Lewis-acid catalyst niobium pentoxide and mechanism study

Lewis-acid catalyst Nb2O5 is first applied in catalytic fast pyrolysis (CFP) of enzymatic hydrolysis lignin (EHL) to produce aromatic hydrocarbons (AHs) that can be used as alternative liquid fuels. The catalyst exhibits a good talent to convert lignin into AHs with quite little polycyclic aromatic hydrocarbons (PAHs) formation. The yield of AHs reaches 11.2 wt% and monocyclic aromatic hydrocarbons (MAHs) takes up 94% under the optimized condition (Catalyst to Lignin ratio 9:1, 650 degrees C). No coke is generated during the reactions. The reaction sequence is proposed and verified by model compound reactions. Furthermore, DFT calculations are performed to understand the mechanisms of limitation of PAHs or char/coke formation and the efficient deoxygenation ability over catalyst. Nb2O5 with Lewis acid sites is proved to be a promising catalyst for the production of AHs from lignin. This work provides a new idea on choice of catalysts for CFP of lignin in future.