Peroxotungstate-Based Ionic Hybrid as a Triphase Heterogeneous Catalyst for Efficient Benzyl Alcohol Oxidation Under Mild Conditions

Abstract

Supported ionic-liquid-phases (SILPs) were synthesized via reaction of 1-methyl-3-(3-triethoxysilylpropyl)imidazolium hexafluorophosphate (ImCl-PF6) with SBA-15 and then peroxotungstate molecules were immobilized on SILPs. The resulting material (W-ImCl-PF6-SBA-15) was characterized via 29Si MAS NMR to detect the chemical environment around Si and its textural and thermogravimetric behavior were determined. To obtain insight into the role of ImCl-PF6 during catalysis, an ImCl-PF6-free catalyst (W/SBA-15) was also synthesized. W-ImCl-PF6-SBA-15 and W/SBA-15 were investigated as catalysts for benzyl alcohol oxidation, as a model reaction, under solvent-free conditions with H2O2.The presence of ImCl-PF6 was crucial for obtaining excellent catalytic activity, and W-ImCl-PF6-SBA-15 showed higher activity and stability than these of W/SBA-15. Optimized reaction conditions were employed to several selected alcohols oxidation and, remarkably, excellent aldehydes selectivity was achieved. The importance of ImCl-PF6-functionalized SBA-15 was evidenced via recycling experiments of benzyl alcohol oxidation, and W-ImCl-PF6-SBA-15 was recycled for ten reaction runs without significant change in benzyl alcohol conversion, benzaldehyde selectivity, and tungsten content.