Synthesis of immobilized heteropolyanion-based ionic liquids on mesoporous silica SBA-15 as a heterogeneous catalyst for alkylation

Abstract

Phosphotungstic acid (H₃PW₁₂O₄₀) has been successfully loaded onto sulfonate-functionalized ionic liquid-modified mesoporous silica SBA-15 by total anion-exchange. The immobilized catalysts were characterized by XRD, N₂ adsorption, TEM, and FTIR spectroscopy. Characterization results show that the mesopore structure of SBA-15 was maintained well even after surface modification and the subsequent anion-exchange step of [PW₁₂O₄₀]³⁻ (PW). In comparison with the task-specific basic ionic liquid (1-(propyl-3-sulfonate) 3-methyl-imidazolium phosphotungstate), the obtained catalyst showed much higher efficiency in alkylation of o-xylene with styrene. More importantly, such an immobilized task-specific basic ionic liquid could be reused without significant loss of catalytic activity even after recycling six times.