Synthesis Of α-Capricbetaine Surfactant

Synthesis ofα-capricbetaine(α-CB) by the chlorization of dodecanoic acid and aminolysis ofα-chlorinedodecanoic acid(α-CDA) was studied in this paper. Instead of expensive long-chaintrialkylamine, natural reclaimed oil was applied to synthesize betaine surfactant with low-cost andshort-process which will abolish the effect of price on production and application of amphotericsurfactant.α-CB was successfully synthesized with trialkylamine and α-CDA in closed system whichwas not reported up to date.α-CDA was obtained with molecular chlorine and dodecanoic acid and the gas/liquid reactionwas carried out on 1 kg of dodecanoic acid scale. Dodecanoic acid is selectively chlorided withchlorine to the correspondingα-monochloro carboxylic acid in a laboratory scale of semibatchreactor with chlorosulphonic acid as catalyst and molecular oxygen as radical trapper. After 12h theconversion of dodecanic acid can reach 97% at 85℃ with 0.32 L/min of chlorine and 0.16 L/min ofoxygen.α-CB was obtained with trialkylamine andα-CDA in closed system. The optimal conditionwas reaction for 10h at 80℃ with 40g/100mL of α-CDA and a ratio of n(trimethylamine): n(α-chloro carboxylic acid) = 3:1 . The yield ofα-CB reached 88.3%.The method of two-phase titration with mixed indicator was developed to determine α-capricbetaine according to its cationic characteristic in acid circumstance. The recovery of the abovemethod is 101.4% and the relative standard deviation (RSD) is less than 0.3%. The analytic result isnot much influenced by the residue of trimethylamine or long-chain carboxylic acid in α-CB. Themethod to determine dodecanoic acid in α-CB was also developed by two-phase titration withbromcresol green indicator in base circumstance. The recovery of the second method is 98.7% andthe corresponding RSD is less than 0.5%, whereas α-CB almost doesn't exert influence on theanalytic results because it doesn't display anionic surfactant characteristic in base solution.Combining the above two methods can set up a methodology to quantitatively analyze the mainactive components in α-CB.Performance of α-CB such as latherbility, foam stability and lime soap dispersing power wassuperior to BS-12, but its wetting ability inferior to BS-12.