Effect of various functional groups on biodiesel synthesis from soybean oils by acidic ionic liquids

Preparation of biodiesel from soybean oils catalyzed by five acidic ionic liquids with three cationic functional groups was investigated. The improvement of the catalytic activities was affected by various functional groups including pyridine group, N-methylimidazole group, triethylamine group. Among them, C₄SO₃Hpy]HSO₄ with pyridine group showed better catalytic activity with the biodiesel yield of 94.5%, and still yielded more than 90% after six successive uses. The possible mechanism was also discussed by two reaction paths in detail.