Process for removing and recycling dimethyldichlorosilane from hydrochloric acid gas

Abstract

The invention discloses a process for removing and recycling dimethyldichlorosilane from hydrochloric acid gas. A frozen brine graphite cooler is used. The process is characterized by comprising the following steps: volatilizing liquid CH3Cl to obtain low temperature less than -50 DEG C; absorbing dimethyldichlorosilane by using CH3Cl at low temperature; and separating absorption liquid into gas having more than 99.9% (wt) of CH3Cl in purity and a residue having more than 99.9% (wt) of dimethyldichlorosilane through rectification. According to the process, an original frozen brine graphite cooler can be adopted; cooling capacity can be obtained by using evaporation of the residue in an absorption tower so as to cool the raw material HCl to the temperature less than -20 DEG C; the whole process is performed in closed cycle, thus dimethyldichlorosilane in a gas phase of the raw material HCl can be thoroughly removed, the separated dimethyldichlorosilane can be treated up to the standard and returned to a dimethyldichlorosilane hydrolysis step; and the process has the advantages of simplicity in method, economy and practicability, low operation cost, little pollution and environment friendliness.

Description

technical field [0001] The invention relates to the field of chemistry, and relates to a process for removing and recovering dimethyldichlorosilane from hydrochloric acid gas. Background technique [0002] Existing large-scale organosilicon equipment hydrolyzes dimethyldichlorosilane chloride to generate siloxane by-product hydrochloric acid gas, which is also called HCl gas. Then HCl gas and methanol in saturated ZnCl 2 Chloromethane is generated under the catalysis of the solution, which is also called CH 3 Cl. CH 3 Cl reacts with Si powder in a fluidized bed to form chlorosilanes. Its main chemical reaction equation is: [0003] n(CH 3 ) 2 SiCl 2 +nH 2 O—→〔CH 3 ) 2 SiO〕 n +2n HCl↑ (1) [0004] Dimethyldichlorosilane Siloxane [0005] 2HCl+CH 3 OH—→CH 3 Cl 3 +H 2 O (2) [0006] Chloromethane [0007] 2CH 3 Cl+Si—→(CH 3 ) 2 SiCl 2 (3) [0008] Dimethyldichlorosilane [0009] The most economical dimethyldichlorosilane hydrolysis method today is t...

AI Technical Summary

Problems solved by technology

The problem existing in the dimethyldichlorosilane recovery process of the prior art is that the amount of dimethyldichlorosilane remaining in the HCl gas is related to the final temperature after cooling, and at -10°C, the dimethyldichlorosilane< 0.99% (mol), at -20°C, dimethyldichlorosilane <0.5% (mol), the lowest temperature of brine is -25°C, and brine at a temperature lower than -25°C is easy to crystallize, so the simple fractionation method will not Possible complete recovery of dimethyldichlorosilane in HCl

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