Study On Methylation And Redistribution Reactions And Their Integration Technology

The paper is concerned with transforming methyltrichlorosilane(Ml) into dimethyldichlorosilane(M2) or trimethylchlorosilane(M3). The methylation and redistribution reactions of methyltrichlorosilane and their integration technology are investigated.The methylation reactions of methyltrichlorosilane can be occurred with methyl chloride in a fixed bed reactor in the presence of aluminum, which serves as a halogen acceptor. The optimum reaction conditions are obtained : reaction temperature is 310~330#, molar ratio of methyl chloride and methyltrichlorosilane is 2.5~3.0 and reaction pressure is 0.06mpa.The conversion of methyltrichlorosilane can be above 50%.It is found that methyltrichlorosilane is more reactive in an agitated bed reactor. Based on the experimental data, the reaction temperature and the height of aluminum bed are key factors of conversion of methyltrichlorosilane. The methylation are consecutive reactions which include the reaction of methylating Ml into M2, then the reactions of methylating M2 into M3 and methylating M3 into tetramethylsilane(M4). Molar ratio of methyl chloride and methyltrichlorosilane has great influence on the composition of reaction products. While M2 and M3 are main products and the molar ratio of M2 and M3 is about 0.1~0.3 when the ratio is under 1.5, the conversion of Ml goes down to less than 60%. Though the conversion can be above 80% by increasing the ratio to above 2.5, the utilization of MeCl and the yield of M2 and M3 goes down sharply. And the main product is M4 whose content is above 75%. The optimum reaction conditions are obtained : reaction temperature is 260~290# molar ratio of methyl chloride and methyltrichlorosilane is 2.0~2.5 and rotate speed is 78 r/min. Generally, the conversion of methyltrichlorosilane is above 80%. There is no M4 in the products, and the molar ratio of M2 and M3 is about 0.2~0.4.The products are analyzed by GC-MS and some byproducts of the reaction are realized, such as methyldichlorosilane and dimethylchlorosilane and hydrocarbons.The mechanism of the methylation reactions is also investigated. The kinetic equation is set up:The redistribution reaction of methyltrichlorosilane and trimethylchlorosilane utilizing aluminum trichloride supported catalysts is discussed in the paper. Based on the experimental data, the quantity of catalyst and the reaction temperature are key factors. The optimum reaction conditions are obtained : the quantity of catalyst is 3%, reaction temperature is 300#, molar ratio of Ml and M3 is 1:1, rotate speed is 200-250 r/min, and reaction time is 3 hour. Generally, the yield of M2 is about 60.6%.In the end, the integration technology of methylation and redistribution reactions is discussed. The optimum reaction conditions are obtained : the methylation reactions temperature is about 250-280#, the redistribution reactions temperature is about 280-300#, molar ratio of MeCl and Ml is 2.1:1, and rotate speed is 78 r/min. Compare to the technology of methylation occurred in agitated reactor, the conversion of Ml increases above 10% and the molar ratio of M2 and M3 increases to 0.5~0.8, utilizing the integration technology. There is no M4 in products.