Upcycling lithium mine tailings into hierarchical core-shell catalysts for cascade deoxygenation and aromatization during biomass pyrolysis

ZT@HZ-X core-shell catalysts were synthesized from lithium mine tailings. • Tuning the Si/Al ratio optimizes hierarchical pores and strong acid sites. • ZT@HZ-30 yielded 43.0% monocyclic aromatics with full furan conversion. • Dense acid sites drive cascade furan cycloaddition and lignin demethoxylation. • Synergistic cascade catalysis for efficient biomass pyrolysis vapor upgrading. Catalytic fast pyrolysis (CFP) is a promising route for converting biomass into chemical products, but its industrial application is limited by the high oxygen content of primary pyrolysis vapors and rapid catalyst deactivation. Here, we report a hierarchical core-shell catalyst, ZT@HZ-X, comprising a lithium mine tailings-zirconia composite core uniformly encapsulated by an HZSM-5 zeolite shell with tuneable Si/Al ratios. The catalytic performance was evaluated by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) during rapeseed straw pyrolysis. The high density of strong acid sites within the microporous shell, combined with a hierarchical mesoporous network, promotes a cascade catalytic mechanism: for holocellulose-derived intermediates, the acidic microenvironment destabilises primary furanic compounds, facilitating possible Diels-Alder-type cycloaddition pathways that contribute to increase the relative peak area of monocyclic aromatic hydrocarbons. Concurrently, in the lignin depolymerisation pathway, the acidic sites selectively cleave ether bonds, driving demethoxylation and demethylation that convert complex syringyl and guaiacyl phenols into simpler p -hydroxyphenyl species. This core-shell catalytic system enables deep deoxygenation and aromatic enrichment of the bio-oil whilst providing a sustainable strategy for valorising lithium mine tailings. Download: Download high-res image (424KB) Download: Download full-size image