Relay catalysis of lignin depolymerization to hydrocarbons over Pt-loaded ferroelectric heterojunction catalyst driven by combined ultrasound-microwave excitation

A relay catalysis strategy driven by ultrasound-microwave excitation was proposed. • Pt/BT/ZnO ferroelectric heterojunction is applied to lignin depolymerization. • Hydrocarbon selectivity of 57.62% achieved via combined ultrasound-microwave excitation. • Cβ–O bond cleavage and deep hydrodeoxygenation pathway were elucidated. • Catalyst retained >50% hydrocarbon selectivity after five cycles. Lignin, as an abundant aromatic polymer, represents a promising renewable feedstock for producing high-quality liquid fuels. However, efficient cleavage of C–O bonds and subsequent hydrodeoxygenation (HDO) of phenolic intermediates into hydrocarbons remain significant challenges. Herein, a Pt-loaded ferroelectric heterojunction catalyst, Pt/BT/ZnO, was constructed and applied to lignin depolymerization. For the first time, a relay catalysis pathway driven by combined ultrasound-microwave excitation was developed. It was found that microwave-driven depolymerization alone suffered from insufficient exposure of active sites, resulting in inefficient conversion of phenolic intermediates. In contrast, the relay catalysis driven by ultrasound-microwave excitation promoted the deep HDO of phenols to hydrocarbons, with the hydrocarbon selectivity reaching 57.62%. Using 2-phenoxy-1-phenylethanol as a model compound, the selectivities of methylcyclohexane and cyclohexane after relay catalysis were enhanced to 36.48% and 18.45%, respectively. Combined with product analysis and DFT calculations, the mechanistic pathway was elucidated, revealing that the major route involves cleavage of the C β –O bond to form phenoxy radicals, followed by deep HDO to produce cycloalkanes. The synergistic effect of spontaneous polarization in Pt/BT/ZnO, ultrasonic cavitation, and microwave dielectric heating endowed the catalyst with excellent cycling stability, with hydrocarbon selectivity remaining above 50% after five runs. This work provides new insights into the application of ferroelectric heterojunction catalysts for lignin valorization and offers a novel route for producing aviation fuel components from renewable biomass. Download: Download high-res image (237KB) Download: Download full-size image