Constructing Ru–O–Nb interfaces in RuOx/NbOPO4 nanosheets for the 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 the production of high-density biofuels from biomass, developing high-efficiency bifunctional catalysts 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 the one-pot solvent-free conversion of lignin-derived phenol and benzyl alcohol to polycycloalkane perhydrofluorene. The NbOPO₄ nanosheet edges were rich in oxygen vacancies and were prone to preferentially anchoring the RuO_x species. 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, and 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 a high conversion of benzyl alcohol (98%) and a high yield of 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 via the selective ring-opening of perhydrofluorene over the synergistic 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.