Ionic Liquid Antioxidant [X][C6H2(OH)3COO] of Biodiesel and Its Theory Antioxidant Mechanism

Abstract

ABSTRACT In this study, three ionic liquid antioxidants were synthesized using a one-step method from gallic acid (C6H7O5) and choline, 1-methylimidazole (MI), and 1-ethylimidazole (EI). The antioxidant activity of ionic liquid antioxidants, corrosion, and oil solubility properties of Jatropha biodiesel were also studied. The results show that the three ionic liquid antioxidants improved the oxidation resistance of Jatropha biodiesel. In addition, 3‰ [MI] [C6H2(OH)3COO] increased the induction period of Jatropha biodiesel by 238%. The solubility of three antioxidants decreases in the following order: [MI] [C6H2(OH)3COO] > [EI] [C6H2(OH)3COO] > [Ch] [C6H2(OH)3COO] > C6H7O5. The surface corrosion of copper sheet decreases in the following order: Jatropha Biodiesel > [Ch] [C6H2(OH)3COO] + Jatropha Biodiesel > [EI] [C6H2(OH)3COOC6H5COO] + Jatropha Biodiesel > [MI] [C6H5COO] + Jatropha Biodiesel. The infrared absorption spectra, NBO charge, and frontier orbital of three ionic liquids were calculated using density functional theory, B3LYP/6-311G(d,p). The antioxidant mechanism of three antioxidants was elucidated.