Novel Bronsted-Lewis Acid Heterogeneous Catalyst: Functionalized Imidazolium Ferric Salts@SBA-15 for Efficient Production of Biodiesel

Bronsted-Lewis acid heterogeneous catalyst functionalized imidazolium ferric salts@SBA-15 ([DSIM][FeCl4]/SBA-15) with large specific surface and mesoporous structure was designed and prepared to catalyze the esterification of oleic acid with methanol for yielding biodiesel (fatty acid methyl ester). The as-prepared catalyst showed good catalytic performance with 98.2% conversion of oleic acid under the optimal reaction conditions: the molar ratio of methanol and oleic acid was 10:1 and the amount of catalyst was 5% of oleic acid mass, 4 h and 70 degrees C. The samples were characterized by X-ray diffraction, FT-IR, N-2 adsorption-desorption, Pyridine-adsorbed FT-IR, Thermogravimetric analysis, Energy dispersive X-ray spectroscopy, scanning electronic microscopy (SEM) and transmission electron microscopy (TEM). The results demonstrated that imidazolium ferric salt was successfully loaded onto the surface of SBA-15 and the catalyst retained the mesoporous structure of the support. The catalyst [DSIM][FeCl4]/SBA-15 still performed over 85.5% of conversion after 5 reaction cycles, which indicated its good stability and reusability.