System for reducing siloxane impurities in dimethyl dichlorosilane hydrolyzed hydrogen chloride

Abstract

The utility model provides a system for reducing siloxane impurities in dimethyl dichlorosilane hydrolysis hydrogen chloride, a top outlet of a hydrogen chloride gas washing tower is connected with an inlet of a gas-liquid separation tank through a pipeline, a top outlet of the gas-liquid separation tank is connected with a hydrogen chloride cooler, and the hydrogen chloride cooler is connected with a demister. The middle part of the hydrogen chloride gas washing tower is connected with the circulating pump through a pipeline, the circulating pump is connected with the hydrochloric acid cooler, and a refrigerant pipeline of the hydrochloric acid cooler extends into the upper part in the hydrogen chloride gas washing tower and is provided with a spray head, so that a refrigerant is sprayed and washed from the tower top, part of siloxane impurities are removed, and circulation is realized. An adsorption medium in the inner layer of the demister is special glass fibers, the component is an FRP + glass fiber mixed material, fog drops with the diameter larger than 1 micrometer are directly intercepted, and when impurities existing in the fog drop form are accumulated to the situation that the gravity of the impurities exceeds the resultant force of the rising force of gas and the surface tension of liquid, the impurities can be separated and fall off, and the impurities are separated and separated. Therefore, the purpose of further removing siloxane impurities is achieved.

Description

Technical Field

[0001] This utility model relates to the field of chemical process technology, specifically to a system for reducing siloxane impurities in the hydrolysis of dimethyldichlorosilane into hydrogen chloride. Background Technology

[0002] Organosilicon combines the properties of both inorganic and organic materials, exhibiting excellent characteristics such as resistance to high and low temperatures, electrical insulation, oxidation stability, corrosion resistance, non-toxicity, odorlessness, and physiological inertness. It is widely used in aerospace, electronics, construction, transportation, chemical, textile, and medical industries. Most organosilicon products are processed from polydimethylsiloxane (PDMS) obtained by the hydrolysis of dimethyldichlorosilane (dimethyl), along with other additives. Therefore, dimethyldichlorosilane hydrolysis is a crucial step in the upstream industrial production of organosilicon.

[0003] Currently, industrial hydrolysis processes all employ low-energy concentrated acid hydrolysis to produce oligomeric siloxanes (dimethyl hydrolysate) and release hydrogen chloride gas. However, due to the complexity of the process, the generated hydrogen chloride gas carries small amounts of unreacted chlorosilane monomers, volatile small-molecule siloxane impurities, and water. These siloxane impurities are highly unstable in acidic media, readily undergoing condensation reactions between hydroxyl groups. Their short-chain siloxanes polymerize into long chains over time, undergoing cross-linking reactions to form gel-like substances that adhere to the walls. These siloxane impurities often exist as droplets with a diameter of less than 1 micrometer, accumulating and causing pipeline and equipment blockages, shortening start-up cycles, and hindering safe and stable production. Furthermore, the presence of siloxane impurities can restrict the synthesis of chloromethane in the next loop, affecting its reaction efficiency and product purity. Therefore, the adsorption and removal of siloxane impurities from hydrogen chloride gas is of great significance for the safe and stable production of organosilicon enterprises and the healthy development of the industrial economy. Summary of the Invention

[0004] To address the problem of high siloxane impurity content in the hydrogen chloride gas produced by dimethyl dichlorosilane hydrolysis, which leads to severe equipment wear, frequent maintenance, and low chloromethane synthesis efficiency, this invention provides a system for reducing siloxane impurities in the hydrogen chloride gas produced by dimethyl dichlorosilane hydrolysis. This system aims to improve hydrogen chloride recovery rate and product purity, increase enterprise economic value, and reduce waste acid emissions.

[0005] This invention relates to a system for reducing siloxane impurities in hydrogen chloride produced by the hydrolysis of dimethyldichlorosilane. The top outlet of the hydrogen chloride gas scrubbing tower is connected to the inlet of a gas-liquid separator via a pipeline. The top outlet of the gas-liquid separator is connected to a hydrogen chloride cooler, and the hydrogen chloride cooler is connected to a demister.

[0006] The middle part of the hydrogen chloride gas scrubbing tower is connected to a circulating pump via a pipeline. The circulating pump is connected to a hydrochloric acid cooler. The refrigerant pipeline of the hydrochloric acid cooler extends into the upper part of the hydrogen chloride gas scrubbing tower and is equipped with nozzles to achieve refrigerant spraying from the top of the tower for scrubbing, removing some siloxane impurities and achieving circulation.

[0007] The top outlet of the hydrogen chloride gas scrubbing tower is also connected to a demister via a pipeline.

[0008] The outlets of the gas-liquid separator, hydrogen chloride cooler, and demister are connected to the separator via pipelines.

[0009] The bottom outlet of the hydrogen chloride gas scrubbing tower is connected to the separator via a pipeline.

[0010] The process includes the following steps: Dimethyl chloride (DMC) reacts thoroughly with water in a static mixer to release hydrogen chloride gas containing siloxane impurities. This gas first enters a packed scrubbing tower for acid washing. The internal structure of the scrubbing tower is Pall ring packing, which allows for continuous and thorough contact between the gas and liquid phases on the packing surface, facilitating gas-liquid mass transfer. Simultaneously, saturated hydrochloric acid cooled to -35°C is sprayed from the top of the tower for washing. This allows the siloxane impurities in the hydrogen chloride gas to be absorbed by the supercooled saturated hydrochloric acid and condensed back down, thus removing some of the siloxane impurities. The temperature of the cooled saturated hydrochloric acid is -1°C to -25°C.

[0011] Then, hydrogen chloride gas enters a gas-liquid separator and a hydrogen chloride cooler (-35℃ refrigerant) for deep condensation and dehydration, achieving gas-liquid two-phase separation. The hydrogen chloride is then deeply cooled to -10℃ to -25℃. The dried hydrogen chloride gas is then introduced into the bottom of a demister. The adsorption medium in the inner layer of the demister is a special glass fiber, composed of FRP + glass fiber composite material. Droplets larger than 1 micrometer in diameter can be directly trapped. When the droplets are very small, they will be subjected to collisions with surrounding gas molecules, resulting in irregular Brownian diffusion motion. This motion increases as the droplet size decreases, greatly increasing the probability of the fiber capturing the droplets. Therefore, this special adsorption medium can adsorb siloxane impurities smaller than 1 micrometer in diameter onto the fiber layer at half the filter element. Impurities smaller than 0.3 micrometers in diameter are adsorbed and fixed by a finer filter layer. When these impurities, existing in the form of droplets, accumulate until their own weight exceeds the combined force of the gas's upward force and the liquid's surface tension, they will separate and fall, thus achieving the purpose of further removing siloxane impurities. Attached Figure Description

[0012] Figure 1 A system for reducing siloxane impurities in hydrogen chloride, a hydrolysate of dimethyldichlorosilane, comprises: 1, a hydrogen chloride gas scrubbing tower; 2, a gas-liquid separator; 3-1, a hydrogen chloride cooler; 3-2, a hydrochloric acid cooler; 4, a demister; and 5, a demister. Detailed Implementation

[0013] Example 1

[0014] like Figure 1 As shown, a system for reducing siloxane impurities in the hydrolysis of dimethyldichlorosilane and hydrogen chloride is described.

[0015] The top outlet of the hydrogen chloride gas scrubbing tower 1 is connected to the inlet of the gas-liquid separator 2 via a pipeline. The top outlet of the gas-liquid separator 2 is connected to the hydrogen chloride cooler 3-1. The hydrogen chloride cooler 3-1 is connected to the demister 4.

[0016] The middle part of the hydrogen chloride gas scrubbing tower 1 is connected to the circulating pump via a pipeline. The circulating pump is connected to the hydrochloric acid cooler 3-2. The refrigerant pipeline of the hydrochloric acid cooler 3-2 extends into the upper part of the hydrogen chloride gas scrubbing tower 1 and is equipped with nozzles to achieve refrigerant spraying from the top of the tower for scrubbing, removing some siloxane impurities and achieving circulation.

[0017] The top outlet of the hydrogen chloride gas scrubbing tower 1 is also connected to the demister 4 via a pipeline.

[0018] The outlets of the gas-liquid separator 2, the hydrogen chloride cooler 3-1, and the demister 4 are connected to the separator 5 via pipelines.

[0019] The bottom outlet of the hydrogen chloride gas scrubbing tower 1 is connected to the separator 5 via a pipe.

[0020] The above-described apparatus is used for the following process: Hydrogen chloride gas containing siloxane impurities, released after dimethyl hydrolysis, enters a packed hydrogen chloride gas scrubbing tower 1 via pipeline a for acid washing. The internal structure of the scrubbing tower is Pall ring packing, which allows for full and continuous contact between the gas and liquid phases on the packing surface and facilitates gas-liquid mass transfer. Simultaneously, saturated hydrochloric acid cooled to -35℃ is sprayed from the top of the tower for washing. This allows the siloxane impurities in the hydrogen chloride gas to be absorbed by the supercooled saturated hydrochloric acid and condensed back down, removing some of the siloxane impurities. At this point, the temperature of the hydrogen chloride gas drops to -1.7℃. Then, the hydrogen chloride gas sequentially enters a gas-liquid separator 2 and a hydrogen chloride cooler 3-1 (using -35℃ refrigerant) via pipelines c and d for deep condensation to -15.2℃ to remove water. Finally, the dried hydrogen chloride gas is discharged from pipeline e... The solution is introduced to the bottom of the demister 4. The adsorption medium in the inner layer of the demister is a special glass fiber, which is composed of FRP + glass fiber composite material. Droplets with a diameter greater than 1 micrometer can be directly intercepted. When the droplets are very small, they will be subjected to collisions with surrounding gas molecules and generate irregular Brownian diffusion motion. This motion increases as the number of droplets decreases, greatly increasing the probability of the fiber capturing droplets. Therefore, this special adsorption medium can adsorb siloxane impurities with a diameter less than 1 micrometer on the fiber layer at 1 / 2 of the filter element. Impurities with a diameter less than 0.3 micrometers are adsorbed and fixed by the finer filter layer. When these impurities existing in the form of droplets accumulate to the point that their own weight exceeds the resultant force of the gas lift force and the liquid surface tension, they will separate and fall, thereby achieving the purpose of further removing siloxane impurities.

[0021] Table 1. Purification effect of hydrogen chloride gas

[0022] .

Claims

1. A system for reducing siloxane impurities in the hydrolysis of dimethyldichlorosilane and hydrogen chloride, characterized in that, The top outlet of the hydrogen chloride gas scrubbing tower (1) is connected to the inlet of the gas-liquid separator (2) via a pipe. The top outlet of the gas-liquid separator (2) is connected to the hydrogen chloride cooler (3-1). The hydrogen chloride cooler (3-1) is connected to the demister (4). The middle part of the hydrogen chloride gas scrubbing tower (1) is connected to the circulating pump via a pipe. The circulating pump is connected to the hydrochloric acid cooler (3-2). The refrigerant pipe of the hydrochloric acid cooler (3-2) extends into the upper part of the hydrogen chloride gas scrubbing tower (1) and is equipped with a nozzle to achieve refrigerant spraying and scrubbing from the top of the tower, removing some siloxane impurities and achieving circulation.

2. The system for reducing siloxane impurities in dimethyldichlorosilane hydrolysis of hydrogen chloride according to claim 1, characterized in that, The top outlet of the hydrogen chloride gas scrubbing tower (1) is also connected to the demister (4) via a pipeline.

3. The system for reducing siloxane impurities in dimethyldichlorosilane hydrolyzed hydrogen chloride according to claim 1, characterized in that, The outlets of the gas-liquid separator (2), the hydrogen chloride cooler (3-1), and the demister (4) are connected to the separator (5) via pipes.

4. The system for reducing siloxane impurities in dimethyldichlorosilane hydrolyzed hydrogen chloride according to claim 1, characterized in that, The bottom outlet of the hydrogen chloride gas scrubbing tower (1) is connected to the separator (5) via a pipe.

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