Direct valorization of biomass waste to gamma-valerolactone

Abstract

Biomass is the only renewable hydrocarbon resource on Earth and therefore plays an essential role in a future sustainable society. Nevertheless, biomass is underutilized for production of chemicals, and is instead burned for energy or left for compost. Derived from biogenic carbohydrates, gamma-valerolactone (GVL) holds pivotal potential as a green fuel, solvent, and platform compound. Converting carbohydrate-rich biomass waste directly to GVL is therefore highly attractive but also very challenging owing to the inert nature and high complexity of biomass, necessitating a versatile and selective catalytic system. Developing benign and complexity-preserving biomass valorization processes would not only allow for sustainable methods to synthesize valuable commodity chemicals, but also provide access to highly attractive carbon-negative procedures. Therefore, producing GVL, that preserves five out of six C–C bonds in hexoses and all the C–C bonds in pentoses, has a high potential. We describe the first direct conversion of raw lignocellulose, starch, and chitin biomass to GVL. Using 1.8 wt% of the homogeneous catalyst Ru-MACHO-BH in 10.9 M H3PO4(aq) with 30 bar of H2 at 140 °C for 24-120 hours provides GVL in excellent yields (10-26 wt%) from twelve different biogenic or industrially processed biowaste sources, either as individual substrates or a combined pool. This corresponds to 26-48mol% yields, or an average of approximately 80-90 mol% yield in each reaction step.