Enhancing the conversion of ethyl levulinate to gamma-valerolactone over Ru/UiO-66 by introducing sulfonic groups into the framework

摘要

The conversion of ethyl levulinate (EL) to gamma-valerolactone (GVL) is an important reaction in biomass conversion. This process undergoes two consecutive reactions: hydrogenation and transesterification of the intermediate compound, i.e. ethyl 4-hydroxypentanoate, which are catalyzed by metal nanoparticles and acid sites, respectively. In this study, we explored the catalytic activity of Ru supported on metal organic frameworks aiming to develop efficient metal-acid bifunctional catalysts for this green process. UiO-66 and its analogues with various substituted groups (-SO3H, -NH2 and -NO2) were employed in this study. The Ru particle size, oxidation state and reducibility were characterized by TEM, H-2-TPR, and XPS. The results suggest that the introduction of functional groups reduces the hydrogenation activity of pristine Ru/UiO-66 to various extents. Catalyst modified with -SO3H group shows much higher acidic catalytic performance while showing hydrogenation activity towards C=O bonds, thus improving the overall transformation of EL to GVL due to the presence of strong Bronsted acid sites.