Renewable phenol production from lignin with acid pretreatment and ex-situ catalytic pyrolysis

A novel pathway to clean production of phenol-rich bio-oil and syngas by catalytic pyrolysis of pretreated lignin was investigated for the first time. The process integrated pretreatment and catalysis. The results revealed that the optimal condition for phenol selectivity (95.5%) from unpretreated lignin pyrolysis was achieved at a pyrolytic temperature of 550 °C with catalyst/lignin ratio of 0.7. Lignin pretreatment boosted the volatile production as well as syngas formation. A significant increase in the phenol concentration (from 0.6 to 7.0 mg/mL) for pretreated lignin was achieved at pretreated temperature of 50 °C for 60 min. During the deactivation test, the catalyst exhibited a benign catalytic performance for phenol selectivity after using four times. Further, the “phenol pool” and free radical were proposed to uncover the mechanism of phenol generation from catalytic conversion of pretreated lignin. These findings pave a new and clean route to produce high-purity phenol, which could ultimately advance the utilization of lignin through facile fix-bed catalytic pyrolysis technology.