Biodiesel made from waste cooking oil is a popular substitute for petroleum diesel. However, due to its high content of free fatty acids (FFA), waste oil must undergo an initial acid catalyzed esterification. This process typically employs concentrated H2SO4 but we chose a milder Lewis acid, tin (II) bromide, as our catalyst. Our investigation is part of a larger project which uses oleic acid as a model FFA, and the tin(II) halides (SnF2, SnCl2, SnBr2, and SnI2) as catalysts. Our investigation primarily focuses on the tin(II) halides SnCl2 and SnBr2, because previous research suggests that these two halides are most appropriate for the methylation of oleic acid. Methanol-D was substituted for methanol in order to assess the role of this species in the overall mechanism. Through the use of NMR, we have determined that methanol-D does eventually make methyl ester, but it takes substantially more time for the reaction to occur and it also occurs best at 60?C. Our investigation is done at 55?C and 60?C with both the SnCl2 and SnBr2 halides compare the percent methyl ester created from the different temperature of the two different tin(II) halides. This poster will present our interpretation of the data, how it relates to potential mechanisms, involved in determining the rate limiting steps and the broader impact for the series of tin(II) halides.

Investigation of the kinetic isotope effect with tin(II) bromide for the esterification of oleic acid

245th National Meeting (2013)

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