Hollow and mesoporous M@aluminosilicate (M = Rh, Pd and Pt) bifunctional catalytic nanoreactors for the hydrodeoxygenation of lignin-derived phenols

Abstract

Hydrodeoxygenation of lignin-derived phenolic compounds to produce alkanes is a promising method used for mitigating fossil energy consumption, but they often require high temperature and high pressure, resulting in their poor catalytic stability and durability. In this study, we encapsulated ∼3.9 nm active metal Rh nanoparticles (NPs) into ∼40 nm hollow mesoporous aluminosilicate nanospheres (HMANs) to synthesize M@Al_x–mSiO₂ nanoreactors with adjustable Al contents for guaiacol hydrodeoxygenation. The optimized Rh@Al_2.0–mSiO₂ catalyst displayed significantly enhanced guaiacol activity and cyclohexane selectivity relative to the Rh@mSiO₂ catalyst under mild reaction conditions. According to the characterization results, the high hydrodeoxygenation activity of Rh@Al_2.0–mSiO₂ could be attributable to the synergistic effect between the metallic Rh and Lewis and Brønsted acid sites, and the introduction of Al species greatly facilitated the adsorption of 2-methylcyclohexanol, thereby enhancing cyclohexane selectivity. The confinement effect of Rh NPs inside the hollow cavities effectively prevents the leaching and aggregation of Rh NPs, thereby improving their catalytic durability and stability.