Study On Green Synthesis Of Vinyltrimethoxysilane

Silicone material has been widely used in various industries due to its unique properties. Silane coupling agent is a distinctive class of organosilicon compounds, which can ehance the interface adhesion between inorganic and organic substances through chemical bond. The hydrosilylation is one of the most important reactions for the synthesis of silane coupling agents, silicon monomers and polymers containing functional groups.In this paper, the synthesis of vinyltrimethoxy silane by hydrosilylation of acetylene with trimethoxysilane was systematically studied in lab test and pilot test. Two kinds of homogeneous catalysts, chloroplatinic acid/isopropyl alcohol-phenothiazine (Cat.1) and chloroplatinic acid/V4 (Cat.2), were prepared. The catalytic activity and selectivity of this two catalysts were compared. Effects of reaction temperature, acetylene flow rate, the Pt content of the catalysts and the dropping speed of trimethoxysilane on product yield were examined. The results showed that the activity and selectivity of Cat.1 were higher than Cat.2, the most appropriate temperature was between 80 and 90℃. The yield reached the maximum when the acetylene flow rate was 80 ml/min, the platinum content was 6.45 ppm and dropping speed of trimethoxysilane was 1/5-1/7 drop/s. Meanwhile, Pt supported on SiO2, activated carbon and SB A-15 zeolite catalysts were prepared by impregnation method. The activity, selectivity and the reusable properties of three supported catalysts were also discussed. It was showed that the catalytic activity and selectivity of Pt supported on SiO2 catalyst was higher than the others, and the activity of three catalysts did not change significantly after four reuse cycles.In pilot test, the synthetic process was optimized and innovated for the drawbacks of bubble method:1, Because the entire reaction volume is reduced, so,trial production were carried out in the low-pressure reactor tower in closed system, compared with the bubbling method, this technology have no emissions, avoiding the silane-containing acetylene recovery problems, and high utilization of raw materials, environmental protection.2. The reaction time was reduced greatly by increasing the reaction area and designing the cycle tower reactor based on the features of gas-liquid reaction.3. The production capacity was inceased significantly by using outer loop cooling process to control reaction temperature based on the problem of transferring the reaction heat.In the pilot test, the effects of the reaction process parameters including catalyst type, catalyst concentration, reaction temperature and the charging rate of trimethoxysilane on the product yield were investigated. It was indicated that the activity and selectivity of Cat.1 were higher than Cat.2. The most suitable reaction temperature was 80-90℃, the product yield can reach the maximum when the platinum content of reaction system was 4 ppm and the charging rate of trimethoxysilane was 100 L/h. The production process characteristics of traditional alcoholysis process and hydrosilylation process were compared. The safety, environmental protection issues and related coping strategies were also considered. The pilot-scale product have been tested and qualified to get the praise of customers.