Catalytic conversion of levulinic acid or furfural alcohol into ethyl levulinate using a sulfonic acid-functionalized coffee biochar

Abstract

A series of sulfonic acid functionalized coffee biochar (SFCB-x) with high acid density and strength were prepared by using sulfuric acid as the sulfating agent. The obtained catalysts could be directly used for esterification of levulinic acid (LA) and alcoholysis of furfural alcohol (FA) affording ethyl levulinate (EL). Further activity tests and characterization confirmed the linear correlation between the catalytic activity and -SO3H density of the catalyst, SFCB-4 holds the highest -SO3H density and thus exhibits the highest catalytic activity towards the production of EL. Under mild conditions, about 97.6% and 81.7% yield of EL could be obtained for LA esterification and alcoholysis of FA, respectively. The catalyst also shows high stability during consecutive catalytic recycles. Furthermore, hot filtration testing suggested that the leaching of the active species was not observed during catalytic recycles, which could be attributed to the covalently linked -SO3H groups on SFCB-4 skeleton. The rational design and construction of SFCB-4 will drive the development of solid acid catalyst derived from natural biomass for the production of bio-based chemicals.