Biodiesel production by esterification of oleic acid over brønsted acidic ionic liquid supported onto Fe-incorporated SBA-15

The esterification of oleic acid with short-chain alcohols using Brønsted acidic ionic liquid supported onto Fe-incorporated SBA-15 (Fe-SBA-15) was studied to develop a green method for biodiesel production. This catalyst was prepared by immobilization of Brønsted acidic ionic liquid 1-(propyl-3-sulfonate)-3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate ([SO₃H-PIm-CPMS][HSO₄]) onto Fe-SBA-15 (IL/Fe-SBA-15). The structure of the catalyst was characterized by XRD, N₂ adsorption-desorption measurement, FT-IR and TEM. The results demonstrated that Fe was incorporated into the framework of SBA-15, bringing Lewis acidic site. After the ionic liquid was successfully immobilized onto the surface of Fe-SBA-15, the structure of the catalyst remained intact. This catalyst displayed relatively high catalytic activity in esterification of oleic acid with short-chain alcohols because of the synergistic effect of Lewis and Brønsted acidic sites. Under the optimum reaction conditions (reaction temperature 363 K, molar ratio of methanol to oleic acid 6: 1, catalyst amount 5 wt %, and reaction time 3 h), the conversion of oleic acid reached to 87.7% when methanol was used as reactant.