Nonbleach process for the purification of palm C16–18 methyl ester sulfonates

There has long been interest in methyl ester sulfonates (MES) derived from natural or renewable sources, such as palm oil, with considerable effort focused on process development. A major drawback with current process technology is the formation of dark brown impurities that create aesthetic and odor issues in the final product. These issues are usually addressed by bleaching rather than by chemical purification. This paper reports on a simple yet highly effective nonbleach, two-step process for purifying palm C16–18 potassium methyl ester sulfonates. The first step comprises addition of water to the impure surfactant mixture. Preferably, the temperature of the system is maintained above the Krafft point of the surfactant, thereby completely solubilizing the surfactant and associated impurities. Once completely dissolved, the surfactant mixture is allowed to cool, and the potassium-neutralized methyl ester sulfonate precipitates out selectively. In the second step, the purified surfactant is recovered by gravity- or pressure-filtration or by centrifugation, followed by drying. The process significantly improves C16–18 MES analytical purity and color without raising safety or environmental concerns. It also allows for the purification of products derived from lower-grade methyl esters, resolves odor issues, and does not require use of substantial amounts of solvent such as methanol.