Study On The Green Synthesis And Properties Of Methyl Polysulfide

Green chemical synthesis has gradually become an important research content with the increasing awareness of environmental protection, and the development and application of raw materials with low toxicity and non-pollution is becoming more and more important. Methyl polysulfide has important applications in oil refining, ethylene cracking process, and often used as curing ingredient of hydrogenation and inhibitor of ethylene cracking and coking. Methyl polysulfide includes dimethyl disulfur, dimethyl trisulfur, dimethyl tetrasulfur, in which dimethyl disulfur has the most widely applications.At present, the synthesis method of dimethyl disulfur is still using the traditional method of dimethyl sulfate, and dimethyl sulfate is methylation reagent. The dimethyl sulfate has a very serious impact on the environment and human because of its toxicity. Therefore, the research has great significance to replace the highly toxic dimethyl sulfate with new type of methylation reagent, which is non-toxic and environmentally friendly.The feasibility of dimethyl carbonate as methylating reagent to producing methyl polysulfide was analyzed in thermodynamics. The influence factors and the reaction conditions of sodium polysulfide and methyl polysulfide were investigated. The content of reaction product was measured by trace water analyzer and gas chromatograph. The structure of the product was characterized by FT-IR.Thermodynamic analysis show that dimethyl carbonate can be used as methylating reagent to prepare dimethyl disulfide when the reaction condition of dimethyl carbonate and sodium disulfide was liquid phase. It is proved that synthesis process of dimethyl disulfide is simple, easy to operare when the sodium disulfide, sulfur and green dimethyl carbonate are used as raw materials.The optimum conditions of synthesis of sodium disulfide are as follows: Molar ratio of sodium sulfide and sulfur is 1.2. The reaction temperature is 60 ℃. The reaction time is 1hour. The yield is more than 98%. The optimum reaction conditions of synthesis of sodium trisulfide are as follows: Molar ratio of sodium sulfide and sulfur is 2.1. The reaction temperature is 70 ℃. The reaction time is 1.5hours. The yield is 97%. The ideal reaction conditions of synthesis of sodium tetrasulfide are as follows: Molar ratio of sodium sulfide and sulfur is 3.2. The reaction temperature is 80 ℃. The reaction time is 2 hours. The yield is 93%.Dimethyl disulfide can obtained with dimethyl carbonate as methylating reagent and the self-made sodium polysulfide. The optimum reaction conditions are as follows: Mole ratio of dimethyl carbonate with sodium disulfide is 7:1. The concentration of sodium disulfide solution is 30% and the reaction temperature is 160 ℃. The reaction time is 6 hours. Addition of alkali catalyst is 2%, which is the mass ratio of accounting for sodium disulfide solution. The yield of dimethyl disulfide is 80%.