Process for purifying trichlorosilane and silicon tetrachloride

Abstract

The invention discloses a process for purifying trichlorosilane and silicon tetrachloride. The process purifies the trichlorosilane and the silicon tetrachloride by means of three-tower continuous rectification and comprises: setting two towers as three-tower continuation; by adjusting process conditions, extracting high-purity trichlorosilane at the top of a rectifying tower 1 by gas phase, while extracting a silicon tetrachloride solution containing a small amount of the trichlorosilane by liquid phase, and feeding the solution into a rectifying tower 2; completing gas phase extraction of residual trichlorosilane and a small amount of the silicon tetrachloride at the top of the rectifying tower 2, and returning the extracts to a synthetic fluid intermediate tank after condensation; and feeding the silicon tetrachloride and high-boiling saline obtained through liquid phase extraction in the rectifying tower 2 into a rectifying tower 3; and carrying out purification on the silicon tetrachloride and the high-boiling saline by the rectifying tower 3 to obtain the high-purity silicon tetrachloride at the top of the tower. The process increases the product yield, the quality, the application and benefits, and realizes stable production control and greatly reduces labor intensity.

Description

technical field [0001] The invention relates to a process for purifying trichlorosilane and silicon tetrachloride, in particular to a process for purifying trichlorosilane and silicon tetrachloride by three-tower continuous distillation, which belongs to the field of silicon chemical industry. Background technique [0002] Trichlorosilane and silicon tetrachloride products are mainly used as raw materials for the production of organic silicon and polysilicon. Among them, trichlorosilane is a basic raw material for the production of organic silicon and polysilicon, while silicon tetrachloride is mainly used for the production of organic silicon coupling agent, white carbon black and other products. At present, trichlorosilane is produced by reacting silicon powder and hydrogen chloride in a fluidized bed, and then the synthetic liquid after the reaction enters the rectification tower and is continuously purified through two rectification towers. [0003] Chinese patent CN200...

AI Technical Summary

Problems solved by technology

In addition, Chinese patent CN1693192A proposes a purification method and device for separating trichlorosilane in a single tower, but its product contains relatively high content of light components such as boron and phosphorus. Although it can meet the requirements of solar cell grade polysilicon, its quality is still low. It is not enough, and the separation efficiency is low, and the energy consumption is high; Chinese patent CN1010455362A has proposed the technology of double-tower separation of trichlorosilane, but there is the problem of unstable product quality index, and the whole process needs a large amount of chilled water and high energy consumption. Big

[0004] In the production of trichlorosilane, as a side reaction, a certain amount of silicon tetrachloride will inevitably be produced. According to the current production process, there are many other by-products in addition to silicon tetrachloride, so the product four The purity of silicon chloride can only reach 95.0%. Generally, the purity of the trichlorosilane product obtained by this method is acceptable, but the purity of silicon tetrachloride is poor, so it cannot be used in a deeper way.

Silicon tetrachloride of this quality can only be used in lower-grade product applications, and the product yield is poor

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