Synthesis Of3-mercaptopropionic With Refining By-product Hydrogen Sulfide

3-mercaptopropionic acid(3-MPA) has received widespread attention because it was used as inportant industrial materials, drug intermediates and has multiple usages. At present, the synthesis of3-MPA is usually using acrylonitrile and sodium hydrosulfide as raw materials. The technological process is very complex and the reaction temperature is demanded strictly compared to other methods. Synthesis technology using acrylic acid(AA) and refining by-product H2S as materials is becoming a focus in Petrochemical Enterprises, especially with the enhancement of resources recycling ideas and the attention to development of refining by-product hydrogen sulfide downstream products. The synthesis of3-MPA with refining by-product H2S not only could elevate the value of hydrogen sulfide but also has a cost advantage compared to other synthesis technology.Few study on acrylic acid and refining by-product hydrogen sulfide as raw materials for synthesis of3-MPA’s technological process was found until now. Based on the present problems and status, this paper conducted a series of systematic studies on heterogeneous reaction system and homogeneous reaction system synthesis processes. The various factors of the two reaction systems were discussed in detail. The main research work and conclusions are as follows.1.Solid metal catalysts of heterogeneous synthesis of3-MPA were investigated systematically. Using Mg(CH3COO)2and H2C2O4as precursors, catalyst for synthesis of3-MPA was prepared by the chemical precipitation method. Liquid bases of homogeneous synthesis of3-MPA were also investigated in detail. Triethylamine was chosen as a system for research, which gave the best results.2. Reaction products of synthesis of3-MPA were qualitatively analyzed, composition and formation of the by-products were identified by GC-MS, HPLC and IR. 3. An external standard HPLC method was used to analyze products. According to the yield of3-MPA, the optimum synthesis conditions of3-MPA preparation in heterogeneous reaction system is as follows:1,4-dioxane as solvent, temperature80℃, hydrogen sulfide pressure0.5MPa, reaction time5h,n(catalyst):n(acrylic acid)=0.2:1, and V(l,4-dioxane):V(acrylic acid)=5:0.2.Under the optimized conditions, the conversion of acrylic acid and selectivity of3-MPA were100%and35.6%, respectively. The optimum reaction conditions of3-MPA preparation in homogeneous reaction system is as follows:acrylic acid was added to reactor after triethylamine reacted with H2S, n(triethylamine):n(acrylic acid)=2.08:1, temperature80℃, reaction time6h, hydrogen sulfide’s first pressure0.1MPa, hydrogen sulfide’s second pressure0.6MPa.Under the optimized conditions, the conversion of acrylic acid and selectivity of3-MPA were99.95%and60.03%, respectively. In general, the conversion of acrylic acid of two reaction systems were much the same,and selectivity of3-MPA of homogeneous reaction system was far better than heterogeneous reaction system.4. The reaction mechanisms of preparation of3-MPA from acrylic acid and H2S were investigated on the basis of others’ research.