Synthesis Of Methyl Ester Sulfonate By The Technology Of Sulfonation-Esterification-Bleaching/Neutralization

At present the way of synthesizing the MES product in laboratory research and industrial exploitation generally took fatty acid as raw material stepping by esterification, sulfonation, and reesterification/bleaching and neutralization-further bleaching. But how to reduce the byproduct ofα-sulfo fatty acid disodium salt (i.e. DSS) was one of the technology difficulties existing. This article proposed a technology route that first fatty acid was sulfonated, and then through esterification and the bleaching/neutralization integration MES product was synthesized in the foundation of summarizing predecessor research. The route could reduce the technique of production flow effectively, and it is possible to obtain MES product with low disodium salt content through once esterification. The main research contents were as follows: Sulfonation of fatty acid was realized through batch sulfonation with chlorosulforic acid to obtainα-sulfo dodecanoic acid intermediate with single carbon distribution and high purity. Optimizing of its following esterification, bleaching and neutralization step was carried on to accomplish the route exploration feasibility and provide certain basis for technology amplification.The main conclusions in the scope of this article were as follows:Influences such as mole ratio, dropping temperature of chlorosulfonic acid and aging tempreture and time on batch sulfonation of dodecanoic acid (i.e. DA) with chlorosulfonic acid were preliminary optimized to getα-sulfo dodecanoic acid (i.e.SDA)intermediate with single carbon distribution and high purity. Through two titrimetric methods, the activeness content of product was determined result in the sulfonation rate. Opimization of process condition batch sulfonation in lab was approached as follows: n (chlorosulfonic acid): n (DA) =1.3:1, the dropping temperature was 60℃, the sulfonation was at 90℃for 60 min and the aging process was at 80℃for 45 min. In the aspect of purification process of SDA, we first carried on the purification of sodium salt ofα-sulfo dodecanoic acid (i.e.MSS) the solubility of which was little in water solution to obtain the white tabular crystal powder. Futhermore, in the way of ionic exchange or direct acidification MSS was transformed to SDA to supply intermediate for succeeding process of exploiting route feasibility and opitimize condition.If the SDA intermediate and methanol were adopted as the raw material to synthesize methylα-sulfo dodecanoic carboxylate (i.e. MS), the self-catalysis of sulfo group in the intermediate was used. The influences of ratio and reaction time on the esterification rate were inspected. Using acid value's change of reacting system has determined the esterification rate in the process The opitimize technology condition was proposed as follows:n (methonal):n (SDA)=30:1, the reaction was at 70℃for 7 h and the esterification rate achieved above 95 %. If MSS and methonal were used with concentrated sulfuric acid adding to synthesize MS, the influences of mole ratio and reaction time to the esterification rate were inspected. With two titrimetric method determinating esterification rate, the best technology conditions were proposed as follows: n (methonal): n (MSS) =80:1, the reaction was at 70℃for 6 h and the esterification rate achieves above 94 %. Finally it was indicated that the process of direct esterification from SDA with self-catalysis and esterification from MSS with adding concentrated sulfuric acid both attained a satisfactory esterification rate. In the process of bleaching and neutralization integration, we selected the temperature of bleaching process, the amount of bleaching agent used, the temperature of neutralization process and the concentration of sodium hydroxide separately as the factors which influence on the luster and content of methyl ester of sodiumα-sulfo fatty acid (i.e. ESS) and DSS of MES product. Through the orthogonal analysis, the possibly best bleaching and the neutralization condition was obtained as follows: bleaching temperature was 50℃, the bleaching agent amount used is 8% mass ratio of MS, neutralization temperature was 40℃and the concentration of sodium hydroxide was 10%. Meanwhile the qualitative and quantitive analysis of ESS and DSS in MES product was carried on through HPLC-ELSD and external reference method. The CMC value of MES product which was purified by alcohol crystallization for several times was determined by method of conductivity and was about 0.01226 mol/L. In addition, through infrared spectrum, mass spectrum and nuclear magnetism MES product's structure appraisal was carried on.Tetradecanoic acid, hexadecanoic acid and octadecane acid were selected as raw material to synthesize C₁₄MES, C₁₆MES and C₁₈MES separately. The structure appraisal was carried on through FT-IR spectrum and the purification of MES products purifyingwas all up to 98 %.