Abstract:

In this investigation,a two-step catalysis process was developed to prepare the biodiesel from the waste lard. First,under the irradiation of 40 kHz ultrasonic,the pre-esterification of the lard with methanol is carried out by using concentrated sulfuric acid as the catalyst. Then,the solid base catalyst CaO/NaA was prepared by means of the isovolumetric impregnation. Finally,the solid base catalyst prepared in optimal conditions was employed to
catalyze the transesterification of the pre-esterified lard with methanol in a 40 kHz ultrasonic field,thus obtaining the biodiesel. The results show that, for the pre-esterification of lard with an initial acid value of 13. 82mg KOH/g,optimal conditions are a ultrasonic power of 150W,a methanol-to-oil molar ratio of 8: 1,a reaction temperature of 50℃ and a concentrated sulfuric acid dosage of 2. 5%,and under such conditions,the acid value of lard can be
reduced to 1. 91mg KOH/g in 30min,that the optimal preparation conditions of the solid base catalyst CaO/NaA,which are obtained by the orthogonal experiments,are a CaO loading amount of 15%,a roasting temperature of 700℃ and a roasting time of 6 h; and that the conversion of methyl ester reaches about 95.8% in 120min in optimal preparation conditions of the biodiesel,namely,a ultrasonic power of 150W,a methanol-to-oil molar ratio of 9: 1,a temperature of 55℃ and a solid base catalyst dosage of 4%,and the solid base catalyst is still of high activity after being used three times.

Key words: biodiesel, ultrasonic, lard, CaO/NaA catalyst, transesterification