Synthesis of isopropyl levulinate from furfural: Insights on a cascade production perspective

The present work explores the production of isopropyl levulinate from furfural by a two-step microwave assisted cascade process. Furfural is a versatile biomass-derived industrial feedstock with high annual production volume. Alkyl levulinates are promising bio-based molecules with several applications in many sectors, in particular, as biofuels, blended with transportation fuels including biodiesel, these compounds can significantly reduce the formation of soot in engines. Thus, in the first step, the catalytic transfer hydrogenation of furfural to furfuryl alcohol was studied employing a simply ad hoc synthesized magnetically recoverable Cu catalyst and 2-propanol as H-donor. Subsequently, the alcoholysis of the previously obtained liquors rich in furfuryl alcohol or of neat furfuryl alcohol solutions to isopropyl levulinate was investigated using commercial solid acid catalysts such as niobium phosphate and Amberlyst sulfonic resins (A15 and A70). The cascade process resulted feasible leading to good furfuryl alcohol yields in the transfer hydrogenation process with Cu-Fe3O4 magnetic catalyst using much lower Cu to furfural molar ratios than commonly reported. The subsequent alcoholysis step of furfuryl alcohol-rich liquors was highly efficient with A70 resin even in presence of unreacted furfural from the first step.