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

• First example to efficiently catalyzed by H5BW12O40 attributing to its high acidity.
• First assembly of micellar nanocatalyst (C16TA)H4BW12O40 had amphiphilic components.
• Water-tolerant property available for esterification reaction.
• The retrieved HPAs could be repeated without appreciable losing high performance.

A highly negatively charged borotungstic acid H5BW12O40 had been tested as homogeneous catalyst in esterification. Compared with common used H3PW12O40, 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 H5BW12O40, a Brønsted-surfactant-combined (C16TA)H4BW12O40 (C16TA = 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.

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