Hierarchical beta zeolites assisted aromatics production from lignin via catalytic fast pyrolysis

Abstract

Converting lignin waste into aromatics is a challenging but crucial aspect of lignin valorization. Although ZSM-5 zeolite is extensively used in lignin deoxygenation, its 10-membered ring (MR) channels limit the diffusion of bulky phenols and tend to produce coke. Herein, a series of 12-MR beta zeolites with varying acidity and hierarchical porosity were synthesized for lignin catalytic fast pyrolysis (CFP). An optimal lignin pyrolysis temperature of 600 °C was initially selected. Subsequently, lignin CFP demonstrated that beta zeolite with medium acidity facilitated aromatics production, with Beta(36) even outperforming ZSM-5(36). The introduction of mesopores further enhanced lignin deoxygenation and the hierarchical B36-0.3-24 increased aromatics selectivity to 56.0 area%, which was 1.5 times that of Beta(36). Combined with the CFP of model compounds (vanillin and catechol), it was inferred that the mesopores and weak acidity played a key role in heavy phenols conversion and aromatics production. In addition, B36-0.3-24 exhibited outstanding reusability in pyrolysis regeneration cycles, underscoring its potential for practical application in lignin valorization.