Study On The Synthesis Of Beta-mercaptopropionic Acid

Beta-mercaptopropionic acid is an important chemical intermediate and industrial raw material, which has extensive application because there are both sulfhydryl group and carboxylic group in its molecular, so it has received widespread attention and has a very broad market prospect. At present, the synthesis of β-mercaptopropionic acid is mainly by the reaction of thiol reagents such as thiourea, sodium hydrosulfide, hydrogen sulfide and sodium thiosulfate with acrylonitrile or acrylic acid which has double bond, or with β-chloropropionic acid. Thereinto, using sodium hydrosulfide and acrylonitrile as raw material to synthesize β-mercaptopropionic acid is the main method used in industrial production at present. However, few studies on the influence law of the synthesis process were found until now. Therefore, the influence factors on the synthesis of β-mercaptopropionic acid with sodium hydrosulfide were studied in this paper. In addition, a new process to convert by-product DTDPA to β-mercaptopropionic acid by electrochemical reduction was studied in this paper, which has great economic and environmental benefits.In order to analyze the product and raw material rapidly and accurately, the analysis method of determination of β-mercaptopropionic acid and acrylonitrile by HPLC is established. This method has good accuracy and repeatability and it is suitable for the determination of β-mercaptopropionic acid and acrylonitrile in related research.In this study, β-mercaptopropionic acid was synthesized with sodium hydrosulfide and acrylonitrile as the main raw material. The influences of several factors(the mole ratio of the raw materials, the addition reaction temperature, the addition reaction time, the powdered sulfur usage, the hydrolysis time, the powdered zinc usage, the reduction reaction temperature and so on) on the yield were optimized through the orthogonal test and single factor experiment. Under the optimum conditions, the yield of the β-mercaptopropionic acid was 81.75%.To avoid the “zinc mud” pollution caused by traditional zinc powder reduction process of by-product DTDPA, electrochemical reduction process was adopted in this study, and factors such as quantity of electric charge, current efficiency and electrolytic temperature were investigated with a homemade plate and frame electrolyzer. Under the optimized conditions, compared with zinc powder reduction method the relative conversion of DTDPA can be 103.25%, and the yield of β-mercaptopropionic acid was 82.79%, current efficiency was 44.60%. This technological process has good repeatability and is reliable, so it has good prospects for industrial application.Extraction is an important step to separate and purify β-mercaptopropionic acid aqueous solution, and is one of the key factor to get high purity product. The extraction effects of different extractants was investigated in this study, and found that ethyl acetate has better extraction effect. Based on this, extraction conditions were optimized, and found that under the conditions of acidizing fluid p H value is 1~2, the ratio of extractant volume and acidizing fluid weight is 1.0 and repeat extraction three times, the extraction yield of β-mercaptopropionic acid reached 99%.