Homogeneous borotungstic acid and heterogeneous micellar borotungstic acid catalysts for biodiesel production by esterification of free fatty acid.

Abstract A highly negatively charged borotungstic acid H 5 BW 12 O 40 had been tested as homogeneous catalyst in esterification. Compared with common used H 3 PW 12 O 40 , it displayed a higher conversion (98.7%) and excellent efficiency (96.2%) due to its high amount of protons in methanol. In order to overcome the drawbacks of homogeneous heteropolyacid H 5 BW 12 O 40 , a Bronsted-surfactant-combined (C 16 TA)H 4 BW 12 O 40 (C 16 TA = cetyltrimethyl ammonium) had been fabricated with strong acidity and nano-size micellar structure resulting in enhanced activity and stability during the reaction, which exhibited consistent activity during recycling in esterification reaction.