Catalytic transfer hydrogenation of ethyl levulinate to γ-valerolactone over supported MoS2 catalysts

Abstract

The hydrogenation of levulinate esters to γ-valerolactone (GVL) is an important step in the transformation of biomass into biofuels. It is attractive to develop new efficient systems for the catalytic transfer hydrogenation (CTH) of levulinate esters to value-added GVL. In this work, a series of MoS₂-based supported catalysts were prepared via an impregnation method for the CTH of biomass-derived ethyl levulinate (EL) to GVL. By comprehensive characterization and catalytic measurements, we found that the CTH activity of EL to GVL is closely related to the MoS₂ morphology and acid distribution on the support. Among the catalysts with different supports, the AC support with abundant Lewis acid sites and large surface area facilitated the high dispersion of low stacked MoS₂ slabs, and the MoS₂-acid synergistic catalysis contributed to the superior activity and selectivity. The conversion of EL and the selectivity of GVL reached 97.2% and 91.2% under optimized conditions over the MoS₂/AC catalyst (230 °C, 1 MPa H₂, 1.5 h), respectively. We also conducted reaction kinetic experiments to reveal the relationship between the active site of the MoS₂/AC catalyst and its catalytic performance, and the plausible reaction pathway and mechanism over MoS₂/AC was proposed. The catalytic performance gradually declined during recycling tests due to the oxidation of MoS₂ and can be easily recovered by resulfuration.