Synergistic regulation of oxygen vacancy and Lewis acid sites by Ru loading in LaMnOx catalysts for boosting 2-butanol production from levulinic acid and levulinates

The conversion of biomass-derived levulinic acid (LA) into 2-butanol offers a promising route to produce valuable secondary alcohols under sustainable conditions. In this study, a series of Ru-LaMnOx catalysts with varied Ru loadings were synthesized and their structural, electronic, and acidic properties were systematically characterized. Increasing Ru loading enhanced the surface Ru⁰/Ru⁴⁺ ratio and promoted the reduction of Mn species. These modifications led to an increased concentration of surface oxygen vacancies (Ov) and a higher density of Lewis acid sites, both of which are critical for the Meerwein–Ponndorf–Verley (MPV) reduction and subsequent hydrogenolysis of LA. Catalytic performance tests revealed that the optimized Ru₃LaMnOx catalyst achieved a 2-butanol yield of 99.1 % at 200 °C under 5 MPa H₂ and 8 h, along with good recyclability. This study identified the ring-opening of γ-valerolactone as the rate-determining step, with Ru⁰ sites and adjacent Ov facilitating hydrogen transfer and selective C–C bond cleavage. Density functional theory calculations confirmed that surface Ov enhanced LA and isopropanol adsorption and promote essential electron transfer processes. These findings demonstrate that tuning Ru loading to synergistically control electronic and acidic properties is a promising strategy for efficient biomass conversion.