Sustainable aromatic production from catalytic pyrolysis of lignin mediated by a novel solid Lewis acid catalyst

Abstract

Lignin catalytic pyrolysis for sustainable aromatic production is a promising approach for reducing the overwhelming dependence on fossil resources while mitigating CO2 emissions. The key to achieving the efficient catalytic pyrolysis of lignin lies in the rational design of advanced catalysts with excellent deoxygenation capacity. In this study, we develop a novel mixed metal oxide (WOx-TiO2-Al2O3) as efficient solid Lewis acid catalysts for the catalytic pyrolysis of lignin. We demonstrate that WOx-TiO2-Al2O3 exhibits the best catalytic ability at a pyrolysis temperature of 600 °C with a catalyst-to-lignin weight ratio of 2. The yields of bio-oil and monocyclic aromatic hydrocarbons (benzene, toluene, and xylene) can respectively reach 30.2 wt% and 1.6 wt%, which is slightly lower than those of the commercial HZSM-5 catalyst (31.7 wt% and 1.9 wt%). We also prove that the M−O−M bonds formed between oxygenophilic metals can generate electron holes as the temperature increasing. Those holes may combine with C-O bonds of phenolic compounds to generate metal–oxygen–carbon (M−O−C) bonds, facilitating the deoxygenation of lignin-derived pyrolysis vapours. These findings may provide guidance for the design of novel solid Lewis acid catalysts for the direct deoxygenation of lignin for the preparation of aromatic compounds.