Production of ethyl lactate by activated carbon-supported Sn and Zn oxide catalysts utilizing lignocellulosic side streams

Abstract

In this study, activated carbon-supported Sn and Zn oxide catalysts were prepared from hydrolysis lignin and used for the conversion of model solutions of trioses, hexoses, and lignocellulosic biomass hydrolysates to ethyl lactate. Both catalysts, SnO2@AC and ZnO@AC, were able to produce ethyl lactate in high yields. SnO2@AC was a more active and selective catalyst in triose (dihydroxyacetone) conversion, providing 99% yield to ethyl lactate. ZnO@AC, by contrast, was more selective in glucose and hydrolysate conversion, with a yield of 60% and 85%, respectively. The ethyl lactate yields were significantly higher than those from the optimized model solution experiments when using ZnO@AC catalyst. These findings indicate that milder acidity of the ZnO@AC catalyst together with Na+ and SO42- in hydrolysate favored ethyl lactate production, preventing byproduct, furan derivatives and acetal, formation. Moreover, the catalysts were able to maintain their catalytic activity in recycling experiments.