Dimethyldichlorosilane hydrolysis hydrogen chloride treatment process for high-pressure chloromethane synthesis

Abstract

The invention provides a dimethyl dichlorosilane hydrolysis hydrogen chloride treatment process for high-pressure chloromethane synthesis. A byproduct hydrogen chloride gas containing small molecular siloxane impurities and moisture generated by dimethyl concentrated acid hydrolysis enters a Pall ring packing type washing tower; spraying supercooled saturated hydrochloric acid which is cooled by a refrigerant at the temperature of-35 DEG C in the hydrochloric acid cooler to hydrogen chloride gas generated by hydrolysis so as to remove part of siloxane impurities; conveying the impurity-removed hydrogen chloride gas mixture to a gas-liquid separation tank and a-35 DEG C refrigerant medium hydrogen chloride cooler for deep condensation to remove part of moisture; the dried hydrogen chloride gas is conveyed to a demister, mist particles with the diameter larger than 1 micron are directly intercepted and mist particles with the diameter smaller than 1 micron are adsorbed and fixed through an adsorption medium of an internal FRP + glass fiber mixed material, sulfuric acid mist carried by the hydrogen chloride gas can be removed, finally, the purified hydrogen chloride gas is compressed, and pure hydrogen chloride gas with the pressure of 0.2-0.4 MPa is obtained. And a guarantee is provided for a co-production chloromethane synthesis process.

Description

Technical Field

[0001] The invention relates to the technical field of chemical process, and in particular to a process for treating dimethyldichlorosilane by hydrolyzing hydrogen chloride for synthesizing high-pressure methyl chloride. Background Art

[0002] Silicone, a multifunctional polymer material, has a unique structure with silicon-oxygen bonds (Si-O-Si) as its skeleton, which enables it to have the properties of both inorganic and organic materials. It can be widely used in chemical, pharmaceutical, electronic and electrical, construction and other fields.

[0003] Dimethyldichlorosilane hydrolysis (abbreviated as: dimethyl hydrolysis) is one of the important links in the production of organic silicon monomers. The industry mainly adopts low-energy concentrated acid hydrolysis process, which is characterized by the direct by-product of hydrogen chloride gas as a synthetic raw material for methyl chloride, realizing the recycling of chlorine. However, in the existing process technology, the by-product hydrogen chloride gas of dimethyl hydrolysis is easy to carry volatile small molecular siloxane impurities and moisture, causing the cooler, water washing tower and other equipment of the methyl chloride synthesis process to gel, block the pipeline, increase the difficulty and frequency of maintenance, resulting in high operation and maintenance costs, affecting the reaction efficiency and product quality of methyl chloride, and easily causing the by-product dilute hydrochloric acid waste acid content of the methyl chloride synthesis process to be high. Therefore, purifying the by-product hydrogen chloride gas of dimethyl hydrolysis and ensuring a certain pressure of the feed hydrogen chloride gas is conducive to the safe and stable production of high-pressure methyl chloride synthesis and increases the economic value of the enterprise. Summary of the invention

[0004] In view of the above technical limitations, the present invention provides a dimethyldichlorosilane hydrolysis hydrogen chloride treatment process for high-pressure methyl chloride synthesis, so as to improve the reaction efficiency and product purity of high-pressure methyl chloride synthesis, reduce the repair and maintenance costs of subsequent equipment, and reduce energy consumption and waste acid emissions.

[0005] The invention discloses a hydrolysis hydrogen chloride treatment process of dimethyldichlorosilane for high-pressure methyl chloride synthesis, which mainly comprises the following process flow: by-product hydrogen chloride gas containing small molecular siloxane impurities and water generated by dimethyl concentrated acid hydrolysis enters a ball ring packing type washing tower, and at the same time, supercooled saturated hydrochloric acid cooled by -35°C refrigerant in a hydrochloric acid cooler is sprayed onto the hydrogen chloride gas generated by the hydrolysis (the temperature of the cooled saturated hydrochloric acid is -1°C to -25°C), so that the siloxane impurities are absorbed by the supercooled saturated hydrochloric acid and condensed and recovered, so as to remove part of the siloxane impurities.

[0006] The impurity-free hydrogen chloride gas mixture is then transported to a gas-liquid separation tank and a hydrogen chloride cooler with a -35°C refrigerant for deep condensation (hydrogen chloride is deeply cooled to -10°C~-25°C) to remove part of the water and separate the gas-liquid phases.

[0007] The dried hydrogen chloride gas is transported to the demister, and the adsorption medium of the internal FRP+glass fiber mixed material is used to directly intercept the fog particles with a diameter greater than 1um, and adsorb and fix the fog particles with a diameter less than 1um, so as to achieve the purpose of purifying the hydrogen chloride gas. Then, the hydrogen chloride gas is transported to the drying tower, and concentrated sulfuric acid is introduced into the drying tower. The strong oxidizing property of the concentrated sulfuric acid is used to cross-link with low molecular weight siloxane, further reduce the volatility of the siloxane and absorb it. At the same time, the water absorption of the concentrated sulfuric acid is used to further perform drying treatment, and after passing through the purification tower demister, the hydrogen chloride gas with a siloxane impurity of less than 20ppm and a moisture content of less than 5ppm is obtained. The adsorption medium inside the purification tower demister is 316L+glass fiber mixed material, which can remove the sulfuric acid mist entrained in the hydrogen chloride gas. Finally, the purified hydrogen chloride gas can be transported to the buffer tank before the compressor and the hydrogen chloride compressor using a stainless steel pipe instead of a fluorine-lined pipe to obtain pure hydrogen chloride gas with a pressure of 0.2-0.4Mpa, which provides a guarantee for the co-production of methyl chloride synthesis process. If the impurities are not removed and dried, it will be difficult to use stainless steel pipes, and expensive fluorine-lined pipes will need to be used. Moreover, because it contains too many impurities, even if expensive fluorine-lined pipes are used, the pressurized hydrogen chloride gas formed in the compression process will be difficult to use as a downstream.

[0008] For the above process, it also includes a dimethyldichlorosilane hydrolysis hydrogen chloride processing device for high-pressure methyl chloride synthesis, the top outlet of the hydrogen chloride gas washing tower is connected to the inlet of the gas-liquid separation tank through a pipeline, the top outlet of the gas-liquid separation tank is connected to the hydrogen chloride cooler, and the hydrogen chloride cooler is connected to the defoamer; The demister is connected to the purification tower through the hydrogen chloride preheater, the top of the purification tower is connected to the compressor buffer tank, and the compressor buffer tank is connected to the hydrogen chloride compressor.

[0009] The middle part of the hydrogen chloride gas washing tower is connected to the circulation pump through a pipeline, and the circulation pump is connected to the hydrochloric acid cooler. The refrigerant pipeline of the hydrochloric acid cooler extends deep into the upper part of the hydrogen chloride gas washing tower and is provided with a nozzle to realize the refrigerant spraying and washing from the top of the tower, remove part of the siloxane impurities, and realize circulation.

[0010] The top outlet of the hydrogen chloride gas washing tower is also connected to the demister through a pipeline.

[0011] The outlets of the gas-liquid separation tank, the hydrogen chloride cooler and the defoamer are connected with the separator through pipelines.

[0012] The bottom outlet of the hydrogen chloride gas washing tower is connected to the separator through a pipeline.

[0013] The top of the purification tower is connected through a purification tower demister, and the purification tower demister is connected to the compressor buffer tank.

[0014] The demister is connected to the purification tower demister through a pipeline, and the purification tower demister is connected to the compressor buffer tank.

[0015] The bottom outlets of the purification tower and the purification tower demister are connected to the circulation pump through pipelines and then connected to the purification tower circulation cooler and the dilute sulfuric acid storage area respectively. The purification tower circulation cooler is connected to the middle inlet of the purification tower. The purification tower is provided with a concentrated sulfuric acid inlet pipeline.

[0016] The bottom outlet of the compressor buffer tank is connected to a drain pipe, and the drain pipe is connected to the storage tank area through a compressor buffer tank drain pump.

[0017] The siloxane impurity content in the pressurized hydrogen chloride gas obtained by adopting the technical solution of the present invention is lower than 1 ppm, and more preferably lower than 0.1 ppm; the water content is lower than 1 ppm, and more preferably lower than 0.1 ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The invention discloses a process for treating dimethyldichlorosilane by hydrolyzing hydrogen chloride for synthesizing high-pressure methyl chloride, wherein 1 is a hydrogen chloride gas washing tower, 2 is a gas-liquid separation tank, 3-1 is a hydrogen chloride cooler, 3-2 is a hydrochloric acid cooler, 4 is a demister, 5 is a demister, 6 is a hydrogen chloride preheater, 7 is a purification tower, 8 is a purification tower demister, 9 is a compressor buffer tank, 10 is a drain pipe, 11 is a hydrogen chloride compressor, and 12 is a purification tower circulating cooler. DETAILED DESCRIPTION

[0019] Example 1 A dimethyldichlorosilane hydrolysis hydrogen chloride processing device for high-pressure methyl chloride synthesis, the top outlet of the hydrogen chloride gas washing tower 1 is connected to the inlet of the gas-liquid separation tank 2 through a pipeline, the top outlet of the gas-liquid separation tank 2 is connected to the hydrogen chloride cooler 3-1, and the hydrogen chloride cooler 3-1 is connected to the defoamer 4; The demister 4 is connected to the purification tower 7 through the hydrogen chloride preheater 6, the top of the purification tower 7 is connected to the compressor buffer tank 9, and the compressor buffer tank 9 is connected to the hydrogen chloride compressor 11. The purification tower 7 is provided with a concentrated sulfuric acid inlet pipeline.

[0020] The middle part of the hydrogen chloride gas washing tower 1 is connected to the circulation pump through a pipeline, and the circulation pump is connected to the hydrochloric acid cooler 3-2. The refrigerant pipeline of the hydrochloric acid cooler 3-2 extends deep into the upper part of the hydrogen chloride gas washing tower 1 and is provided with a nozzle to achieve refrigerant spray washing from the top of the tower to remove part of the siloxane impurities and achieve circulation.

[0021] The top outlet of the hydrogen chloride gas washing tower 1 is also connected to the demister 4 through a pipeline.

[0022] The outlets of the gas-liquid separation tank 2, the hydrogen chloride cooler 3-1 and the demister 4 are connected to the separator 5 through pipelines.

[0023] The bottom outlet of the hydrogen chloride gas scrubbing tower 1 is connected to the separator 5 through a pipeline.

[0024] The top of the purification tower 7 is connected through a purification tower demister 8, and the purification tower demister 8 is connected to a compressor buffer tank 9.

[0025] The demister 4 is connected to the purification tower demister 8 through a pipeline, and the purification tower demister 8 is connected to the compressor buffer tank 9.

[0026] The bottom outlets of the purification tower 7 and the purification tower demister 8 are connected to the circulation pump through pipelines and then connected to the purification tower circulation cooler 12 and the dilute sulfuric acid storage area respectively. The purification tower circulation cooler 12 is connected to the middle inlet of the purification tower 7.

[0027] The bottom outlet of the compressor buffer tank 9 is connected to a drain pipe 10, and the drain pipe 10 is connected to the storage tank area through a compressor buffer tank drain pump.

[0028] like Figure 1 , the by-product hydrogen chloride gas containing small molecular siloxane impurities and moisture produced by the hydrolysis of dimethyl concentrated acid enters the ball ring packed scrubber 1, and is fully contacted with the supercooled saturated hydrochloric acid (-35℃ refrigerant spray) circulating inside the hydrochloric acid cooler 3-2 for gas-liquid mass transfer. At this time, the temperature of the hydrogen chloride gas is reduced to -5.5℃, so that the siloxane impurities are absorbed and condensed and recovered by the supercooled saturated hydrochloric acid to remove part of the siloxane impurities. Then, the hydrogen chloride gas mixture after impurity removal is transported to the gas-liquid separation tank 2 and the hydrogen chloride cooler 3-1 (-35℃ refrigerant) for deep condensation, and the moisture is removed at -14.5℃. The dried hydrogen chloride gas is then transported to the demister 4, and the adsorption medium of the internal FRP+glass fiber mixed material is used to directly intercept the fog particles with a diameter greater than 1um, and adsorb and fix the fog particles with a diameter less than 1um, thereby achieving To purify the hydrogen chloride gas, it is then transported to the purification tower 7, and concentrated sulfuric acid is introduced into the drying tower. The strong oxidizing property of the concentrated sulfuric acid is used to cross-link with low-molecular-weight siloxanes, further reducing the volatility of the siloxanes and absorbing them. At the same time, the water absorption of the concentrated sulfuric acid is used to further perform drying treatment, and after passing through the purification tower demister 8, the hydrogen chloride gas with a siloxane impurity of less than 20ppm and a water content of less than 5ppm is obtained. The adsorption medium inside the purification tower demister is a 316L+glass fiber mixed material, which can remove the sulfuric acid mist entrained in the hydrogen chloride gas. Finally, the purified hydrogen chloride gas can be transported to the compressor front buffer tank 9 and the hydrogen chloride compressor 11 using a stainless steel pipe instead of a fluorine-lined pipe, to obtain pure hydrogen chloride gas with a pressure of 0.2-0.4Mpa, which provides a guarantee for the co-production of methyl chloride synthesis process.

[0029] Table 1 Purification effect of hydrogen chloride gas

[0030] Example 2 like Figure 1 , the by-product hydrogen chloride gas containing small molecular siloxane impurities and moisture produced by the hydrolysis of dimethyl concentrated acid enters the ball ring packed scrubber 1, and is fully contacted with the supercooled saturated hydrochloric acid (-35℃ refrigerant spray) circulating inside the hydrochloric acid cooler 3-2 for gas-liquid mass transfer. At this time, the temperature of the hydrogen chloride gas is reduced to -2.7℃, so that the siloxane impurities are absorbed by the supercooled saturated hydrochloric acid and condensed and recovered to remove part of the siloxane impurities. Then, the hydrogen chloride gas mixture after impurity removal is transported to the gas-liquid separation tank 2 and the hydrogen chloride cooler 3-1 (-35℃ refrigerant) for deep condensation, and the moisture is removed at -20.3℃. The dried hydrogen chloride gas is then transported to the demister 5, and the adsorption medium of the internal FRP+glass fiber mixed material is used to directly intercept the fog particles with a diameter greater than 1um, and adsorb and fix the fog particles with a diameter less than 1um, thereby achieving To purify the hydrogen chloride gas, it is then transported to the purification tower 7, and concentrated sulfuric acid is introduced into the drying tower. The strong oxidizing property of the concentrated sulfuric acid is used to cross-link with low-molecular-weight siloxanes, further reducing the volatility of the siloxanes and absorbing them. At the same time, the water absorption of the concentrated sulfuric acid is used to further perform drying treatment, and after passing through the purification tower demister 8, the hydrogen chloride gas with a siloxane impurity of less than 20ppm and a water content of less than 5ppm is obtained. The adsorption medium inside the purification tower demister is a 316L+glass fiber mixed material, which can remove the sulfuric acid mist entrained in the hydrogen chloride gas. Finally, the purified hydrogen chloride gas can be transported to the compressor front buffer tank 9 and the hydrogen chloride compressor 11 using a stainless steel pipe instead of a fluorine-lined pipe, to obtain pure hydrogen chloride gas with a pressure of 0.2-0.4Mpa, which provides a guarantee for the co-production of methyl chloride synthesis process.

[0031] Table 2 Purification effect of hydrogen chloride gas

[0032] Example 3 like Figure 1, the by-product hydrogen chloride gas containing small molecular siloxane impurities and moisture produced by the hydrolysis of dimethyl concentrated acid enters the ball ring packed scrubber 1, and is fully contacted with the supercooled saturated hydrochloric acid (-35℃ refrigerant spray) circulating inside the hydrochloric acid cooler 3-2 for gas-liquid mass transfer. At this time, the temperature of the hydrogen chloride gas is reduced to -10℃, so that the siloxane impurities are absorbed by the supercooled saturated hydrochloric acid and condensed and recovered to remove part of the siloxane impurities. Then, the hydrogen chloride gas mixture after impurity removal is transported to the gas-liquid separation tank 2 and the hydrogen chloride cooler 3-1 (-35℃ refrigerant) for deep condensation, and the moisture is removed at -18.5℃. The dried hydrogen chloride gas is then transported to the demister 5, and the adsorption medium of the internal FRP+glass fiber mixed material is used to directly intercept the fog particles with a diameter greater than 1um, and adsorb and fix the fog particles with a diameter less than 1um, thereby achieving For the purpose of purifying the hydrogen chloride gas, it is then transported to the purification tower 7, and concentrated sulfuric acid is introduced into the drying tower. The strong oxidizing property of the concentrated sulfuric acid is utilized to cross-link with low molecular weight siloxanes, further reducing the volatility of the siloxanes and absorbing them. At the same time, the water absorption of the concentrated sulfuric acid is utilized to further perform drying treatment, and after passing through the purification tower demister 8, the hydrogen chloride gas with a siloxane impurity of less than 20 ppm and a water content of less than 5 ppm is obtained. The adsorption medium inside the purification tower demister is a 316L+glass fiber mixed material, which can remove the sulfuric acid mist entrained in the hydrogen chloride gas. Finally, the purified hydrogen chloride gas can be transported to the compressor front buffer tank 9 and the hydrogen chloride compressor 11 using a stainless steel pipe instead of a fluorine-lined pipe, to obtain pure hydrogen chloride gas with a pressure of 0.2-0.4 MPa, providing a guarantee for the co-production of methyl chloride synthesis process.

[0033] Table 3 Purification effect of hydrogen chloride gas .

Claims

1. A process for hydrolyzing dimethyldichlorosilane with hydrogen chloride for high-pressure methyl chloride synthesis, characterized in that Including the following process: (1) The by-product hydrogen chloride gas containing small molecular siloxane impurities and water produced by the hydrolysis of dimethylformamide with concentrated acid enters the scrubbing tower, and undergoes gas-liquid mass transfer with the circulating supercooled saturated hydrochloric acid to remove some of the siloxane impurities; (2) transporting the hydrogen chloride gas obtained in step (1) from which part of the siloxane impurities have been removed to a gas-liquid separation tank and a hydrogen chloride cooler for deep condensation to remove moisture; (3) conveying the hydrogen chloride gas obtained in step (2) to a demister to further adsorb siloxane impurities; (4) transporting the hydrogen chloride gas obtained in step (3) to a drying tower and a drying tower demister to obtain hydrogen chloride gas with higher purity; (5) The purified hydrogen chloride gas obtained in step (4) is finally transported to the buffer tank before the compressor and the hydrogen chloride compressor to obtain pressurized hydrogen chloride gas.

2. A process for treating dimethyldichlorosilane by hydrolysis of hydrogen chloride for high-pressure methyl chloride synthesis as claimed in claim 1, characterized in that The washing tower in step (1) is a ball ring packed washing tower.

3. A process for treating dimethyldichlorosilane by hydrolysis of hydrogen chloride for high-pressure methyl chloride synthesis as claimed in claim 1, characterized in that The supercooled saturated hydrochloric acid cooling medium circulated in step (1) is a -35°C refrigerant, and the temperature of the saturated hydrochloric acid after cooling is -1°C to -25°C.

4. A process for treating dimethyldichlorosilane by hydrolysis of hydrogen chloride for high-pressure methyl chloride synthesis as claimed in claim 1, characterized in that The medium of the hydrogen chloride cooler for deep condensing and removing water from the hydrogen chloride gas in step (2) is a -35°C refrigerant, and the hydrogen chloride is deeply cooled to -10°C~-25°C.

5. A process for treating dimethyldichlorosilane by hydrolysis of hydrogen chloride for high-pressure methyl chloride synthesis as claimed in claim 1, characterized in that The adsorption medium of the inner layer of the defoamer in step (3) is a special glass fiber, whose composition is FRP+glass fiber, which can adsorb and remove siloxane impurities.

6. A process for treating dimethyldichlorosilane by hydrolysis of hydrogen chloride for high-pressure methyl chloride synthesis as claimed in claim 1, characterized in that The adsorbent and desiccant used in the drying tower in step (4) are concentrated sulfuric acid, and the internal medium of the defoamer of the purification tower is 316L+glass fiber.

7. A process for treating dimethyldichlorosilane by hydrolysis of hydrogen chloride for high-pressure methyl chloride synthesis as claimed in claim 1, characterized in that The hydrogen chloride gas with a siloxane impurity of less than 20 ppm and a water content of less than 5 ppm after purification in step (5) is transported to the buffer tank in front of the compressor and the hydrogen chloride compressor using a stainless steel pipeline to obtain 0.2-0.4 MPa pressurized hydrogen chloride gas.

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