Utilization of chlorosilane high-boiling compounds
Thread Content
Recently, siloxanes with high boiling points have been esterified to produce silicone oils; however, due to the many impurities in these high-boiling-point compounds, the resulting silicone oils turn black in color. And at present, it is also unknown what uses the resulting silicone oil will have, as well as the optimization strategies. Have any of you sea friends carried out any related processing? How to make use of the high-boiling substances in silicone. The sources of high-boiling substances are trichlorosilane produced by the reaction of silicon powder with hydrogen chloride, and the residues collected from the bottom of the reactor after the distillation and purification of silicon tetrachloride.
Previously, a process was also tried in which high-boiling substances were directly hydrolyzed to produce metasilicic acid, which was then dissolved in liquid alkali to yield sodium metasilicate; however, the yield obtained in this case was not good either. First, no obvious sodium metasilicate crystals can be seen; second, the yield is very low, and it is difficult to control the amount of liquid alkali.
This post was last edited by *lihuagong on 2015-9-6 11:00. What are these high-boiling components? Hexachlorodisilane (Si2Cl6)? Hexachlorodisiloxane (Si2OCl6)? I have read some literature stating that hexachlorodisilane, which is purified from these high-boiling residue streams, is still very useful. Hexachlorodisilane (Si2Cl6) is an efficient deoxidizing agent as well as a raw material for producing disilane; it can be used to manufacture amorphous silicon films, materials for optical fibers, glass, MoSi2, and more. Among these applications, the production of nitrogen-silicon films is its most important use. Compared to traditional methods such as those using dichlorodihydrosilane or silane for vapor deposition of nitrogen-silicon films, the hexachlorodisilane vapor deposition method features lower deposition temperatures and pressures, higher efficiency, and yields films with improved density, insulation properties, corrosion resistance, and compatibility. At present, it is expensive on the market; those with a purity of over 98% cost 370 dollars per kilogram, making it the most valuable component among the residual materials. However, it is said that purification of this is rarely done domestically.
The purification cost of hexachlorosilane is very high; three additional columns are needed. Moreover, the current output is still far from sufficient to achieve purification. Due to the limited analytical instruments available in the factory, I conducted an analysis using only a thermal conductivity cell gas chromatograph. In the clear liquid obtained after distilling out the high-boiling substances, the silicon tetrachloride content was over 50%, while the content of low-boiling substances was around 1%; the remaining components were used to prepare standard samples. According to the literature, there are also metal chloride impurities such as phosphorus trichloride, titanium tetrachloride, and aluminum trichloride. The content of hexachlorosilane is in the range of 10%.