Methyl Ester Sulfonate Production

The process under analysis comprises three major sections: (1) Transesterification; (2) Sulfonation; and (3) Finishing.

Transesterification. In the transesterification reaction, triglyceride (palm oil) reacts with methanol to form of glycerine and methyl ester in ratio 1:3. The triglyceride is sequentially converted into diglyceride, monoglyceride and glycerine. Transesterification equilibrium is shifted towards ME formation by adding methanol in excess, and the reaction is carried out in the presence of alkaline catalysts, in a two-stage mixer/settler unit. After the methyl ester produced is separated (as light phase) from the glycerine and water (heavy phase). The methyl ester is then purified from glycerine and methanol in a counter current scrubber, while the glycerine by-product, dissolved in the excess methanol, is recovered in a rectification column. Unreacted methanol is recycled to the transesterification.

Sulfonation. The methyl ester, along with a mixture of sulfur trioxide gas in dry air, is fed to an annular falling film reactor where the ME rapidly reacts with two molecules of SO3 to form an adduct. Subsequently, the adduct is rearranged forming MESA in a digester, completing the sulfonation at elevated temperatures.

Finishing. The digested MESA is mixed with a controlled flow of methanol and with hydrogen peroxide bleach in a bleaching system, in order to reduce MESA color to a commercially acceptable level and to prevent MESA degradation into di-salt by-products. The bleached MESA is then neutralized by a 50% caustic soda solution, originating a uniform concentrated paste composed of Methyl Ester Sulfonate. Finally, after a drying step in which methanol and excess process water are removed, powdered MES product is obtained.