| Five novel acidic dication ionic liquids, imidazolium and pyrimidinium, were synthesized and their catalytic performances in the transesterification of waste cooking oil to prepare biodiesel were studied. The results showed that imidazolium acidic dication ionic liquids exhibited good catalytic activity, in which the catalytic activity of ［MIM］2C3［HSO4］2 was the best. With ［MIM］2C3［HSO4］2 as catalyst, the influences of molar ratio of methanol to oil, reaction time, reaction temperature and catalyst dosage on the transesterification were investigated by single factor experiment and orthogonal experiment, and the stability of the acidic dication ionic liquid was also researched. The results showed that the optimal reaction conditions were obtained as follows: ratio of methanol to oil 45∶1, reaction temperature 170 ℃, reaction time 2 h, catalyst dosage 8%(based on the mass of waste cooking oil ),under these conditions,the yield of biodiesel was up to 95.8%. Moreover, the acidic dication ionic liquid had good stability and no obvious decrease in catalytic activity after being reused for six times. |
