Green catalytic process for γ-valerolactone production from levulinic acid and formic acid

A highly efficient and environmentally friendly process for the hydrogenation of biomass-derived levulinic acid (LA) using formic acid (FA) as a hydrogen donor to produce γ-valerolactone (GVL) has been developed. This method achieves a remarkable 99% yield of GVL in an aqueous medium under mild, additive-free conditions (150 °C, 1.5 hours, 0.5 mol% [Ru]). These conditions represent the best reported so far for producing GVL from LA and FA using a ruthenium bifunctional catalyst (MO-Ru: Ru-Mg/Al, MO: mixed oxide). A significant synergy between Ru and Mg/Al was observed, enhancing the selective activation of formic acid and the subsequent hydrogenation of levulinic acid. This effect is attributed to the combined catalytic action of Ru species and the medium-strength acidic and basic sites found on the MO-Ru surface, which together promote selective reaction steps in the FA activation and LA hydrogenation processes. The production of GVL from levulinic acid and formic acid, both derived from cellulose hydrolysis, is a key reaction in the valorization of biomass into renewable fuels and chemicals. The application of this methodology not only enhances the economic viability of the process but also eliminates the need for energy-intensive separation of levulinic acid from the aqueous mixture of levulinic acid and formic acid. Additionally, a possible reaction mechanism for the hydrogenation of levulinic acid was proposed.