A Novel Approach to Synthesis Ethoxylated Alkyl Sulfonates in Microemulsion Microreactor

A novel approach to synthesis ethoxylated alkyl sulfonates in microemulsion microreactor

Ji Chen, Ming Yang, Yun Fang*

The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education; School of Chemical & Material Engineering, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P. R. China

Abstract: Alkyl ethoxylated sulfates (AES) is one of the commercial anionic surfactants with excellent properties in wetting ability, dispersing ability, emulsification and electrolyte resistance. However, the unstable sulfate ester bond in the molecule of AES makes it easily decomposed at high temperature or in strong acidic or alkaline conditions, which hinders it being used more widely in certain extreme environments. Ethoxylated alkyl sulfonates (EAS) contain a chemical stable sulfonate group in the molecule in stead of unstable sulfate group in AES, which can be widely used in various harsh environments such as high temperature, high salinity, strong acids or strong alkalis. In this work, the nucleophilic substitution reaction between AES and Na₂SO₃ to produce EAS is run in micellar and microemulsion microreactors, respectively. The effect of reaction times, temperatures, the reactant concentrations and the mole ratio of oil/water on the conversion of AES to EAS are determined. By comparison, an optimum AES concentration is found at which the maximum sulfonation yield of EAS is obtained in microemulsion microreactors is 82.1%. This is because that the distance of the adjacent AES ionic heads becomes larger in microemulsion microreactor than that in micellar microreactor due to co-existing of co-surfactant and oil phase,. Therefore, the electrostatic repulsion between AES ionic heads and the attack ion SO₃^2- becomes weaker in microemulsion microreactor, which could great improve the sulfonation yield of EAS.

Key word: Ethoxylated alkyl sulfonates, Alkyl ethoxylated sulfates, micelle, microemulsion, sulfonation