Preparation of Epoxidized Fatty Acid Methyl Ester with in situ Auto-Catalyzed Generation of Performic Acid and the Influence of Impurities on Epoxidation

Epoxidized fatty acid methyl ester (EFAME) is a renewable and biodegradable plasticizer that can be produced from various vegetable oils and even waste oils. In this work, refined soybean oil (RSO) was first converted to fatty acid methyl ester (FAME) by enzymatic transesterification, followed by epoxidation with performic acid in situ generated via auto-catalyzed reaction of formic acid with hydrogen peroxide. Effects of several factors on epoxidation of RSO FAME were investigated, and the conditions were optimized by response surface methodology. Impacts of several potential impurities on epoxidation were further investigated. It was found that the effects of triglyceride (RSO), glycerol and free fatty acid could be negligible. However, mineral acid such as sulfuric acid could significantly improve the rate of epoxidation, but the cleavage of epoxy group was also strengthened, resulting in lower epoxy value of the EFAME product. Surfactants showed significant negative effects on epoxidation. The feasibility of producing EFAME from waste cooking oil was further investigated. Compared with RSO, waste oil needed a second-stage epoxidation to epoxidize most of the double bonds, but obtained poorer epoxy value with lower degree and selectivity of epoxidation and EFAME yield.