Synthesis of an immobilized Brønsted 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) ₃SO₃H-HIM]HSO₄) Brønsted acidic ionic liquid catalyst ([(CH₂)₃SO₃H-HIM]HSO ₄/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) ₃SO₃H-HIM]HSO₄ had been immobilized on PS-SG. [(CH₂)₃SO₃H-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)₃SO₃H-HIM]HSO₄/PS-SG could still give satisfactory catalytic activity.