Development of hafnium-silica solid Lewis acids for γ-valerolactone production from biobased levulinic acid

Abstract

There is growing awareness of the need to expand the γ-valerolactone (GVL) market within the biobased economy, although challenges remain in developing sustainable, green processes. In this work, the biobased top platform chemical, levulinic acid (LA), was converted to GVL under relatively mild conditions, via catalytic transfer hydrogenation (CTH) routes, using solid Lewis acid catalysts consisting of morphologically distinct EPDM and LFS type silicas and hafnium. The catalyst development was based on important requirements for process feasibility and involved several post-synthesis strategies and introduction of Hf-sites via different methods to meet superior performances. Complementary structural and molecular-level characterisation techniques were employed together with catalytic and kinetic modelling/computational studies for studying the influence of the material properties on the catalytic performances for targeting GVL. The developed heterogeneous catalysts contributed to enhanced productivity (up to 87% GVL yield, at 180 °C), were stable in consecutive runs, and also seemed promising in terms of the E factor. EPDM and LFSs were never investigated before for biomass conversion processes or any other catalytic system, to the best of our knowledge.