Synthesis Of α-Chloro-Fatty Acids

α-Chloro-fatty acids are important intermediates employed for synthesizing fine chemicals such asα-amino acids and betaine-like amphoteric surfactants. Improving the synthesis process ofα-chloro-fatty acids will extend the applicable field of biomass fatty acids to replace petroleum resource. In this paper, the catalysts used in the chlorination of dodecanoic acid were selected to investigate the catalytic mechanism. With chlorosulphonic acid as catalyst, oxygen as a scavenger, the prosessing condition of chlorination of dodecanoic acid was also investigated. The main points were as follows:The effects of different catalyst combinations on the synthesis ofα-chloro-dodecanoic acid (α-CDA) were investigated. Cerium sulfate as a solid acid catalyst had no effect on synthesizingα-CDA. A series of acyl chlorides (such as 4-toluene sulfonyl chloride, dodecanoyl chloride, chlorosulphonic acid, etc.) , proton acids (such as H type cation exchange resin, chlorosulphonic acid, 4-toluene sulfonic acid, acetic acid, etc.) and their combinations were tested with acetic anhydride as a reference. The catalytic system with acyl chloride and strong proton acid moieties will be good for chlorination of dodecanoic acid. Chlorosulphonic acid was found to be the best among the assayed catalysts due to its acyl chloride and strong proton acid moieties.With chlorosulphonic acid as catalyst, oxygen as a scavenger, some processing parameters such as moisture in the reaction system, dosage of chlorosulphonic acid, reaction time, reaction temperature, flow rate of chlorine, rotate speed, ratio of vO2 : vCl2 and chlorosulphonic acid addition policy were investigated. With the guarantee of catalytic activity of chlorosulphonic acid, the yield ofα-CDA had a direct proportion with dosage of chlorosulphonic acid and flow rate of chlorine. Dosage of chlorosulphonic acid w(chlorosulphonic acid) : w(dodecanoic acid)=2% could be more reasonable in industry, and 120℃was the right temperature. Rotate speed not only accelerated the reaction, but also accelerated the escape of chlorine, and the seemly value was 300 rpm(linear speed 47⁴9 m/min). Reducing the proportion of vO₂ : vCl₂ less than 1:2 will produce poly-chlorinated fatty acids. Addition of chlorosulphonic acid at the beginning or many times at intervals had the same yield ofα-CDA. Antioxidant BHT and VE could not eliminate all the chlorin free group. Adding someα-CDA beforehand had no effect on accelerating the yield ofα-CDA. PTFE muddler was better than magnetic force and homogeneous machine.With chlorosulphonic acid as catalyst, oxygen as a scavenger, w(chlorosulphonic acid) : w(dodecanoic acid)=2%, 120℃, vO₂ : vCl₂=1:2, vO₂=22.6 L/h, 700 rpm,α-chloro-myristic acid,α-chloro-hexadecanoic acid,α-chloro-stearic acid andα-chloro-SA-18640,α-chloro-SA-1865 were prepared.