Efficient production of ethyl levulinate from cassava over Al2(SO4)3 catalyst in ethanol–water system

Abstract

One-pot achievement of ethyl levulinate from cassava was conducted in ethanol–water system over several simple sulfate salt catalysts. Al2(SO4)3 catalyst had the best performance in synthesizing ethyl levulinate comparing with those of a series of sulfate salts. The highest yields of ethyl levulinate was up to 39.27% as well as 7.78% levulinate acid when cassava was catalyzed in ethanol medium by adding 10wt% water. 13C and 1H NMR spectroscopic investigations confirmed that isomerization of glucose to fructose over Al2(SO4)3 catalyst is an important step in producing ethyl levulinate and levulinate acid. Due to aggregations of Al3+ under hydrothermal conditions, tiny amount of Al3+ were detected in filtrate at the percentage of 0.32% even if in absolute water. Brønsted and Lewis acids could improve the yield of ethyl levulinate and levulinate acid by synergistic effect. All results suggested that Al2(SO4)3 was a simple and efficient catalyst for ethyl levulinate and levulinate acid production.