Abstract:

Using a self-made 1-propylsulfonic acid-3-methylimidazolium-p-toluenesulfonic acid ionic liquid([MIMPS] [C₇H₇O₃S]) as catalyst, the esterification and deacidification of acidified oil with high acid value was carried out with self-designed equipment as reaction device. The effects of amount of methanol, amount of catalyst, reaction temperature, reaction time on the conversion of acidified oil and acid value of pre-esterified oil were investigated, and then the recyclability of catalyst was studied. The infrared spectrum analysis results showed that the synthesized ionic liquid accorded with its structural characteristics. The ionic liquid had good thermal stability under 200℃. The optimum process conditions determined by single factor and orthogonal tests were as follows:acidified oil 50 g, methanol 0.99 mL/min, catalyst dosage 2.5%, reaction time 3 hours, reaction temperature 105℃. Under these conditions, the conversion rate could reach 98.42%, and the acid value changed from 120 mg/g to 1.9 mg/g. After esterification, the acid value of the acidified oil met the requirement of the acid value for preparing biodiesel (less than 4 mg/g). As the ionic liquid catalyst was reused for 9 times, the conversion rate remained above 75%, indicating that[MIMPS] [C₇H₇O₃S] ionic liquid catalyst had good catalytic activity and good stability for deacidification and esterification of acidified oil with high acid value.

Key words: biodiesel, esterification, acidified oil, deacidification, ionic liquid