Comparison of epoxidation methods for biobased oils: dioxirane intermediates generated from Oxone versus peracid derived from hydrogen peroxide

A study was carried out to compare the epoxidation of unsaturated vegetable oils using dioxirane intermediates generated in situ using Oxone to that by the peracid/hydrogen peroxide method. Epoxidized oils are typically synthesized using hydrogen peroxide, as well as acetic or formic acid. This synthesis requires heating and catalysts and generates acidic waste. Recently, advances have been made in the process of using Oxone (potassium peroxymonosulfate) and ketones to generate in situ dioxiranes to epoxidize alkenes. The dioxirane method allows for room temperature reactions and eliminates the use of peroxides and acids. Epoxidation of soybean oil, hempseed oil and sucrose soyate using in situ generated dioxiranes was carried out and parameters such as molar ratios and addition rates were studied. The data show that optimum reaction conditions are reached when molar ratios of Oxone and unsaturation are 1.6:1 and the Oxone addition rate is 1 mL min(-1). As a comparison, epoxidations using the acetic acid/hydrogen peroxide method were carried out and cured materials were prepared from the epoxidized compounds. Negligible differences were identified in the materials prepared from both synthetic pathways. An environmental sustainability assessment using green chemistry principles was also conducted for both methods to evaluate their safety and efficiency with respect to multiple criteria including minimizing waste generation and energy consumption. The analysis shows that, although the peracid method is atom economic and generates less waste, the dioxirane method offers better occupational safety and requires less energy, demonstrating the tradeoffs involved with either pathway if one is to be selected. (c) 2021 Society of Chemical Industry