Two-step biodiesel production from crude Jatropha curcas L. oil using ultrasonic irradiation assisted

In this paper, the feasibility of crude Jatropha curcas L. oil (CJCO) as raw material to produce biodiesel under low-frequency ultrasonic irradiation (40 kHz) assisted is examined. A two-step transesterification process (acid catalyzed esterification followed by alkaline catalyzed transesterification) is employed to produce biodiesel. In the first step, the high level of free fatty acid (FFA), 12.5%, of CJCO is successfully reduced to less than 3% by acid catalyzed esterification with 15% w/w methanol to oil ratio, catalyst concentration 3.0% w/w, ultrasonic irradiation time 20 min at under reaction temperature 30°C, which are selected as optimum conditions for the acid catalyzed esterification. Then, the second step, alkaline catalyzed transesterification is carried out as methanol to oil ratio 15% w/w, catalyst concentration 1% w/w, reaction temperature 30°C and ultrasonic irradiation time 30 min. This results to high percentage of conversion to biodiesel about 98%. Comparing the results obtained under the ultrasonic irradiation in this study with those under conventional stirring conditions, ultrasonic irradiation technique significantly illustrated the higher efficiency than the conventional method, especially for the high FFA oil.