Synthesis of an immobilized Bronsted acidic ionic liquid catalyst on chloromethyl polystyrene grafted silica gel for esterification

A chloromethyl polystyrene grafted silica gel (PS-SG) supported 1-(propyl-3-sulfonate) imidazolium hydrosulfate ([(CH2)(3)SO3H-HIM]HSO4) Bronsted acidic ionic liquid catalyst ([(CH2)(3)SO3H-HIM]HSO4/PS-SG) was prepared in this study. After characterization through elemental analysis, BET, SEM and FT-IR, it was found that chloromethyl polystyrene had grafted on the surface of silica gel, and [(CH2)(3)SO3H-HIM]HSO4 had been immobilized on PS-SG. [(CH2)(3)SO3H-HIM]HSO4/PS-SG showed high catalytic activity for a series of esterifications and could be recovered easily. After being reused for 9 times in the synthesis of methyl propionate, [(CH2)(3)SO3H-HIM]HSO4/PS-SG could still give satisfactory catalytic activity.