Selective synthesis of γ-valerolactone from levulinic and formic acid over ZnAl mixed oxide

Abstract

After testing different mixed oxides, a very promising catalyst to obtain γ-valerolactone from levulinic acid and formic acid is proposed in this work: a ZnAl hydrotalcite-derived material. Optimum conditions (T = 140 °C, FA/LA = 5/1, aqueous phase stirred batch reactor) excel results previously proposed in the literature, combining high activity (>87%) and selectivity (90% GVL yield) with remarkable stability, the reaction being performed at mild conditions and using a highly available and cheap catalyst.A detailed mechanistic with its kinetic study was accomplished for this optimum catalyst, considering that formic acid decomposition is the limiting step following a second–order kinetic, and the FA dehydration to AL is a pseudo-first–order reversible step. Angelica-lactone is identified as the main by–product and the precursor for the formation of light organic deposits, the main responsible for the slight deactivation observed during the experiments in absence of reactivation procedure.