Optimization Of The Synthesis Of Alfa-Long Alkyl Betaine Zwitterionic Surfactant

Betains are increasingly attracting the interest of researchers both in industrial applications and within academic fields owing to their unique properties, such as excellent water solubility, insensitivity to the presence of salts and to temperature, good biodegradability, biological safety due to the mildness to the skin and eyes, high foam stability, and a synergistic effect with a wide variety of ionic and nonionic surfactants. An effective an economic two step of route was investigated to synthesize the long alkyl chain betaine zwitterionic surfactant directly. First step,α-chlorododecanoic acid was prepared by natural fatty acid with chlorosulfuric acid as catalyst and oxygen as a scavenger. Second step,α- long alkyl chain betaine zwitterionic surfactant was synthesized byα-chlorododecanoic acid and short-chain trertiary amine, trimethylamine.Alpha-chloro fatty acid is an important intermediate for synthesis of alpha- hydroxy acid, alpha- amino acid, alpha- alkyl betain and some drugs,also can be applied to rare earth metal extraction. In this paper, a new method, Gas Chromatography(GC)-Relative Density(RD) coupling method, was studied for alpha-Chloro reaction depth on-line monitoring. Set alpha-Chloro reaction of dodecanoic acid(DA) as an example, we established the relationship of alpha-chlorododecanoic acid(α-CDA) content and relative density(RD) , measuring each compound content of alpha-Chloro reaction by GC and the corresponding RD. Only needed to measure RD, we established an simple and rapid On-line monitoring alpha-Chloro reaction method by GC-RD coupling figure.Solvent-free system of quaternary amination was investigated. The effect of the ratio of initial substances, reaction temperature and reaction time on quaternary amination ofα-CDA with trimethylamine was studied in orthogonal design. Optimization of process condition was approached as follows, n(trimethylamine):n(α-CDA) = 6:1, reacted for 10 hours at 80℃. The yield ofα-CB reached 92.6%.Dodecyl betaine, tetradecyl betaine and hexadecyl betaine were successfully prepared by dodecanoic acid, myristic acid, hexadecyl acid and stearic acid respectively.