Constructing Ru-O-Nb Interfaces in RuOx/NbOPO4 Nanosheets for One-Pot Conversion of lignin-derived Phenol and Benzyl Alcohol to Polycycloalkane Aviation Biofuels

Abstract

To address the challenges of complex separation and high energy consumption in producing high-density biofuels from biomass, developing high-efficiency bifunctional catalyst to integrate carbon-carbon coupling and hydrodeoxygenation processes is highly desired. Herein, a bifunctional catalyst with RuO_x anchored on the edge of NbOPO₄ nanosheets was successfully fabricated through an impregnation-calcination method, enabling one-pot solvent-free conversion of lignin-derived phenol and benzyl alcohol into polycycloalkane perhydrofluorene. The NbOPO₄ nanosheet edges were enriched in oxygen vacancies and were prone to anchoring RuO_x species preferentially. The optimized 3%RuO_x/NbOPO₄ exhibited abundant Ru-O-Nb interfacial species, which synergized with Brønsted acid sites (BASs) to enhance the alkylation performance. The in-situ generated Ru⁰ species from the Ru-O-Nb interfacial species exhibited superior hydrogen dissociation capability, then the synergistic interaction with BASs through hydrogen spillover significantly boosted the hydrodeoxygenation efficiency. 3%RuO_x/NbOPO₄ with more Ru-O-Nb interfacial species exhibited high conversion of benzyl alcohol (98%) and yield towards perhydrofluorene (72%) under mild conditions (160 °C, 3 h) with a low environmental E-factor (≤2.8). Mechanistic studies identified the cyclization hydrogenation of oxygenated intermediates as the rate-determining step, and the product dicyclohexylmethane was mainly formed from the selective ring opening of perhydrofluorene over the synergy metal-acid sites of 3%RuO_x/NbOPO₄. This study provides a deep insight into designing efficient bifunctional catalysts for sustainable aviation fuel production through process integration.