SO3H-functionalized ionic liquids as efficient catalysts for the synthesis of bioadditives

Three kinds of SO3H-functionalized Brønsted-acidic ionic liquids with different acidities were applied to the etherification of glycerol with tert-butyl alcohol. High conversion and good selectivity were obtained under mild conditions. Among the ionic liquids investigated, those having a HSO4− anion afforded the highest glycerol conversion and those having a F3CSO3− anion afforded the largest head product selectivity for glycerol etherification. The minimum-energy geometries and experimental results show that acidities and catalytic activities of ionic liquids are not only related to their structures but also to their immiscibility.