Preparation of biodiesel from waste oil catalyzed with brønsted acid ionic liquid

The preparation of biodiesel from waste oil and methanol catalyzed by a Brønsted acidic ionic liquid with an alkane sulfonic acid group as catalyst was studied under different reaction conditions. When the molar ratio of methanol to waste oil is 12 and the mass ratio of ionic liquid to oil is 0.02, 86.8% fatty acid methyl ester is obtained in the products after the reaction has taken place at 140°C for 5 h. Under the same reaction conditions, the ionic liquid has no obvious change of catalytic activity after using 9 times. So the catalyst shows great reusability and good catalytic activity for preparation of biodiesel from waste oil.