Acetalization of carbonyl compounds catalyzed by acidic ionic liquid immobilized on silica gel

Imidazolium-silica heterogeneous catalyst (SG-[(CH₂) ₃SO₃H-HIM]HSO₄) was prepared by immobilization of acidic ionic liquid 1-(propyl-3-sulfonate) imidazolium hydrosulfate ([(CH₂)₃SO₃H-HIM]HSO₄) on silica-gel using tetraethoxysilane (TEOS) as silica source in this study. The properties of the samples were characterized by FT-IR, SEM and TG/DSC. The results suggested that [(CH₂)₃SO₃H-HIM]HSO₄ had been successfully immobilized on the surface of silica-gel and the immobilized ionic liquid catalyst SG-[(CH₂)₃SO ₃H-HIM]HSO₄ had good thermal stability. The original smooth surface of silica-gel was covered with [(CH₂) ₃SO₃H-HIM]HSO₄ and a rough surface of SG-[(CH₂)₃SO₃H-HIM]HSO₄ was formed, but the size of particles had no obvious change. Moreover, SG-[(CH ₂)₃SO₃H-HIM]HSO₄ exhibited high catalytic activity for a series of acetalization and could be recovered easily. After reused for 10 times in the synthesis of benzaldehyde ethanediol acetal, the catalyst could still give satisfactory catalytic activity.