Synthesis of γ-valerolactone from different biomass-derived feedstocks: Recent advances on reaction mechanisms and catalytic systems

As a natural renewable resource, the catalytic conversion of lignocellulosic biomass is considered to be an important strategy to alleviate the tremendous dependence on fossil resources. The synthesis of gamma-valerolactone (GVL), which is hailed as a new-generation of biomass-based platform molecule, is one of the pivotal steps in the transformation of biomass resources into liquid fuels and high-value chemicals. The catalytic routes for the synthesis of GVL from lignocellulosic feedstocks have been continuously enriched and improved in recent years. Herein, our principal focus is the reaction mechanisms and catalytic systems of GVL from various biomass-derived feedstocks. The specific reaction routes and catalytic performances of GVL synthesis based on the traditional basic raw materials such as levulinic acid (LA) and alkyl levulinates (AL) were discussed and compared, and one-pot processes with cascade steps of cellulosic and hemicellulosic derivatives such as furfural (Fur), furfuryl alcohol (FAL) as well as cellulosic carbohydrates into GVL were also summarized and analyzed in detail. A more intuitive and comprehensive retrospection of the up-to-date literatures on GVL synthesis through multiple pathways was presented, and practical suggestions on improving the cost, stability and efficiency of the overall catalytic systems were also proposed.