Depolymerization of lignin to cycloalkanes using Lewis acid-enhanced bifunctional catalyst

Lignin, as a kind of biomacromolecule, plays a crucial role in the development of renewable energy sources. However, achieving excellent catalytic efficiency and selectivity towards expected products over a single catalytic system remains a significant challenge. The adjustment of acidic sites is an effective strategy to enhance hydrodeoxygenation (HDO) activity and product selectivity. This strategy facilitates charge transfer and activates substrate migration with the catalyst. Therefore, it is necessary to understand the relationship between the structure and activity of acid sites in catalysts, and construct synergistic Brønsted-Lewis sites. In this study, the incorporation of Ni@NC active phase derived from metal-organic frameworks (MOFs) significantly enhanced both the strength and quantity of Lewis acid sites (LASs) in the Ni@NC-HZSM-5 composite catalyst. This enhancement facilitated the cleavage of C Ar –OCH 3 bonds in lignin oil. Furthermore, the abundant Brønsted acid sites (BASs) present in HZSM-5 markedly promoted the cleavage of C Ar –OH bonds. Efficient conversion of real lignin oil was achieved through the synergistic action of the dual-acid sites, resulting in the conversion of 98.50 % and the C 6+ cycloalkane selectivity of 95.05 %. This study proposed a novel approach to the efficient upgrading of lignin-based bio-oil into alternative fuels using heterogeneous catalysts.