Sunday, May 4, 2008
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Biodiesel synthesis  via enzymatic esterification of  feed stock with high content of free fatty acids

Marcella S. Souza1, Monica A. P. Silva1, and Marta A. P. Langone2. (1) Eq, Rio de Janeiro Federal University, EQ/UFRJ-Centro de Tecnologia, BlocoE, Lab I221, Cidade Universitaria - 21949598, Rio de Janeiro, Brazil, (2) Ppgeq, Rio de Janeiro State University, Rua Sao Francisco Xavier 524 / Predio Haroldo Lisboa/ Sala 427, Rio de Janeiro, Brazil

The growing interest for renewable sources of energy is responsible for the worldwide efforts towards the development of biofuels. Biodiesel in particular is synthesized via transesterification of triglycerides from vegetable oils with ethanol or methanol. However the current production costs of biodiesel is not competitive when compared to  petroleum diesel. An alternative route to biodiesel is based on esterification of free fatty acids (FFA) present in high concentration in certain feed stock. In this work, a distillate from soybean oil deodorization - a by-product from the production of soybean oil (FFA  content: 73 wt%) - was used as feed stock for enzymatic synthesis of biodiesel.  The local (Brazil) availability of ethanol from fermentation of sugar cane lead us to use this alcohol in all experiments. The esterification reactions were carried out in a batch reactor. Three commercially available immobilized lipases were used, namely,  Novozyme 435, Lipozyme RM IM and Lipopzyme TL IM, all from Novozymes, in solvent free-media. We searched for optimum reaction parameters: temperature, enzyme concentration, amount of ethanol and its feeding technique to the reactor (stepwise ethanolysis). The enzyme reuse was also evaluated. Reaction was faster with Novozyme 435. The highest conversion (83.5%) was obtained after 90 min using 3 % wt. of Novozyme 435 and two stage stepwise addition of ethanol at 50ºC. Regarding Lipozyme RM IM, the conversion was only 15% after 3 cycles.

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