(636a) High Yield Epoxidation of Fatty Acid Methyl Esters with Performic Acid Generated In-Situ

In recent years, a worldwide interest in renewable resources from the biomass, has spurred the manufacture of biodiesel as a more benign fuel, capable of lower environmental impact. It is customarily produced by transesterification of the vegetable oil triglycerides usually with methanol, employing sodium methoxide (or hydroxide) as homogeneous catalyst. The resulting product is referred to as FAME (fatty acid methyl ester). Thus, FAMEs have become widely available commodities which, in view of the stringent requirements of the automobile industry, are produced with great purity. This, in turn, has reopened new avenues to oleochemicals synthesis. One of these alternatives involves transforming the double bonds of the fatty acid molecules into oxirane (epoxide) groups. Epoxides have a high commercial importance and are widely utilized in plastics manufacture, lubricants, detergents and –more recently- as intermediates in chemical reactions.

In this study soybean FAME was employed to analyze in detail the epoxidation reaction network when performic acid (PFA) is used as oxygen carrier. The epoxidation reaction and the parallel, deleterious reactions linked to the oxirane ring-opening. The influence of several process variables (viz., degree of mixing, temperature, mol ratio of FAME double bonds/hydrogen peroxide/formic acid and solvent addition) on the system was studied, seeking reaction conditions capable of achieving high epoxide yields. Concentrated H₂O₂ (60 wt%) was used throughout the study. Also, the relevant kinetic rate constants pertaining to this reacting system were found.

The reaction temperature has a high impact in the yield and selectivity of the system, but employing 40 ºC it is possible to achieve high conversions and high yield as well. The epoxide yield is a strong function of the available amount of FA in the system. Formic acid is indeed crucial for producing enough PFA in the aqueous phase –which then passes to the organic phase to deliver an oxygen atom to the double bonds- but, also, is the main responsible for the opening of the oxirane rings. Also the H₂O₂-to-double bonds molar ratio was found to decrease the oxirane selectivity by ring-opening as said molar ratio was increased.