A method for purifying siloxanes using hydrocarbon compounds

Abstract

The present application belongs to the field of purification of organic silicon hydrolyzate, and particularly relates to a method for purifying siloxane by using hydrocarbon compounds. The material is preheated by a product heat exchanger through a light-removing tower feed tank and a light-removing tower feed pump, and then is secondarily preheated by a light-removing tower feed preheater and then enters the light-removing tower. The material is rectified by a light-removing tower reboiler, light components are condensed from the top of the light-removing tower by a light-removing tower overhead condenser and then are condensed to a light-removing tower reflux tank, an assistant heptane is added into the light-removing tower reflux tank, separated acid and water are discharged to an acid discharge tank, and the hydrolyzate is purified by a light-removing tower reflux pump. The purification method provided by the present application promotes the separation of hydrocarbons and water and improves the oil-water separation speed of the reaction system by the participation of a certain proportion of hydrocarbon compounds, so that the acid content is low and the quality of the hydrolyzate is high.

Description

Technical Field

[0001] This invention belongs to the field of purification of organosilicon hydrolysis products, specifically relating to a method for purifying siloxanes using hydrocarbon compounds. Background Technology

[0002] Dimethyldichlorosilane hydrolysis is a fundamental step in the organosilicon industry and plays a crucial role. Currently, the crude hydrolysis products produced by dimethyldichlorosilane hydrolysis have poor oil-water separation. The main contaminants are hydrocarbons (approximately 1-4% concentration), short-chain siloxanes (primarily D3), and trace amounts of HCl (approximately 1-2 ppm concentration). These contaminants are difficult to remove, resulting in excessive water carryover in the next process, poor reaction efficiency in the pyrolysis reactor, and a high level of impurities in the product, directly affecting the operational quality of subsequent use units. Summary of the Invention

[0003] To address the shortcomings of existing hydrolysis product purification technologies, this invention provides a method for purifying siloxanes using hydrocarbon compounds. This process utilizes hydrocarbon compounds, solving the problem of slow separation of hydrocarbons and other impurities (D3 rings and acids) in the hydrolysis products, thereby obtaining high-quality hydrolysates. Furthermore, the reaction system maintains a slight positive pressure, which does not inhibit the removal of light components from the crude hydrolysates.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] This invention provides a method for purifying siloxanes using hydrocarbon compounds, comprising the following steps:

[0006] (1) The crude hydrolysate is kept at a stable liquid level in the feed tank of the light-light-removal tower, and then preheated by the feed preheater of the light-light-removal tower;

[0007] (2) The preheated crude hydrolysate is a vaporized feed that enters the light-light removal tower from the top of the stripping section. In the tower, hydrocarbons, D3 rings, all residual water, acids and D4 rings are vaporized and then enter the rectification section. In the rectification section, the reflux from the light-light removal tower reflux tank is used to cool the vapor stream and condense all the 210-230 degree hydrolysate carried therein so that it flows down back to the light-light removal tower.

[0008] (3) Reflux concentrates hydrocarbon feed. The hydrocarbon vapor stream from the rectification section of the tower enters the top condenser of the light-light-removal tower for condensation. Then the liquid hydrocarbon feed stream enters the reflux tank of the light-light-removal tower from the top condenser of the light-light-removal tower, and is then pumped back to the rectification section of the light-light-removal tower from the reflux tank.

[0009] (4) In the stripping section, the hydrolysis product flows from the feed inlet of the light-light removal tower to the distribution plate, flows down through the packing section to the bottom of the tower, and the hydrolysate is pumped into the E2103 heat exchanger. The hot hydrolysis product from the light-light removal tower and the cold hydrolysis product from the auxiliary agent bed A exchange heat. The hot hydrolysis product from the E2103 heat exchanger flows through the auxiliary agent cooler and is cooled by the process water. Then the cooled hydrolysate flows through the pre-filter and enters the auxiliary agent bed A to remove contaminants. The hydrolysis product then flows out of the auxiliary agent bed A and flows through the post-filter to remove all particles in the product stream. Then it flows through the E2103 heat exchanger to obtain the heat energy from the hot hydrolysis product from the light-light removal tower. The hot hydrolysis product leaves the E2103 heat exchanger and enters the separation system.

[0010] (5) Control the slight positive pressure of the light tower, add hydrocarbon compounds into the reflux tank of the light tower, and let the hydrolysis products stand out.

[0011] Furthermore, in step (1), the light-light removal tower is divided into two different functional sections: the bottom section or stripping section has a diameter of 1.9m, and the middle section of the tower has two packing sections; the top section or rectification section is shorter and the stripping section has a diameter of 0.7m, and the rectification section includes one packing section.

[0012] Furthermore, in step (1), the packing material in the packing section is a ceramic Pall ring type.

[0013] Furthermore, in step (1), the preheater is heated to 90-110°C.

[0014] Furthermore, in step (4), the additive in the additive bed A is an anionic resin.

[0015] Furthermore, in step (5), the feed ratio of the hydrocarbon compound is 0.075; after adding the hydrocarbon compound, the top temperature of the light tower reflux tank is 100-130℃ and the top pressure is 0.01-0.1MPa.

[0016] Furthermore, in step (5), the hydrocarbon compound is heptane.

[0017] In the processing system of this invention, all equipment and piping components, including the light-weight residue removal tower feed preheater, the light-weight residue removal tower itself, the light-weight residue removal tower top condenser, the light-weight residue removal tower reflux tank, and the product heat exchanger, are made of acid-corrosion-resistant materials. The light-weight residue removal tower preheater and the light-weight residue removal tower top condenser are made of graphite heat exchangers. The E2103 heat exchanger and the additive cooler are made of super stainless steel.

[0018] The beneficial effects of this invention are as follows: The purification method provided by this invention, with the participation of a certain proportion of hydrocarbons, most hydrocarbons, D3 rings, and all residual water / acids, promotes the separation of hydrocarbons and water, improves the oil-water separation speed of the reaction system, has low acid content, and produces high-quality hydrolysis products. Attached Figure Description

[0019] Figure 1 This is a system diagram for purifying siloxanes using hydrocarbon compounds; where 1 is the light-light-removal tower, 2 is the light-light-removal tower feed preheater, 3 is the light-light-removal tower top condenser, 4 is the light-light-removal tower reflux tank, 5 is the light-light-removal tower reflux pump, 6 is the product heat exchanger, 7 is the light-light-removal tower feed pump, 8 is the light-light-removal tower feed tank, 9 is the auxiliary agent A bed, 10 is the plate heat exchanger, 11 is the E2103 heat exchanger, 12 is the light-light-removal tower reboiler, and 13 is the light-light-removal tower bottom liquid pump. Detailed Implementation

[0020] The present invention will be further illustrated below with specific examples. It should be noted that the following description is only for explaining the present invention and does not limit its content.

[0021] The material described in this invention is fed from the light-light-removal tower feed tank 8 into the product heat exchanger 6 via the light-light-removal tower feed pump 7 for preheating, and then into the light-light-removal tower feed preheater 2 for secondary preheating before entering the light-light-removal tower 1. The material is then distilled by the light-light-removal tower reboiler 12. The light components are condensed from the top of the tower through the light-light-removal tower top condenser 3 to the light-light-removal tower reflux tank 4. Heptane is then added to the light-light-removal tower reflux tank 4. The separated acid and water are discharged to the acid discharge tank, and the hydrolysate is refluxed and purified by the light-light-removal tower reflux pump 5.

[0022] Example 1

[0023] The crude hydrolysate feed rate is 25 t / h. After passing through a product heat exchanger, the crude hydrolysate exchanges heat with the subsequent hot-roller product at a temperature of 85-95℃. It then enters the light oil removal tower preheater for further heating to achieve optimal operation, at a temperature of 100-110℃. The preheated crude hydrolysate is a vaporized feed, entering the light oil removal tower from the top of the stripping section. Inside the tower, most hydrocarbons, D3 rings, all residual water / acids, and some D4 rings vaporize before entering the rectification section. The top temperature of the tower is 115-123℃, and the pressure inside the tower is 15-20 kPa. The hydrocarbon feed then enters the light oil removal tower top condenser, with the condenser outlet temperature controlled at 55-65℃, for further condensation into the light oil removal tower reflux tank. The rectification product enters the light oil removal tower reflux tank for acid-oil separation. Heptane is added to the reflux tank of the light hydrocarbon removal tower at a feed ratio of 0.075 by mass to increase the density difference between the water and oil phases, promote the separation of hydrocarbons and water, improve the oil-water separation rate of the reaction system, and remove chlorides from the hydrolysate. The reflux section concentrates the hydrocarbon feed, reduces impurities in the hydrolysate, and a portion of the circulating liquid is sent back to the first reaction vessel to facilitate the separation of acids and siloxanes.

[0024] In the stripping section, the hydrolysis product flows from the feed inlet of the light-weight product stripping tower to the distribution plate, then flows downwards through the packed section to the tower bottom. Heat is supplied by the reboiler of the light-weight product stripping tower to ensure the tower bottom temperature is controlled at 210-230 degrees Celsius, ensuring the hydrolysis product is free of any residual hydrocarbons. The hydrolysis product is pumped from the light-weight product stripping tower bottom liquid into the E2103 heat exchanger, where the 210-230 degree Celsius hydrolysis product from the light-weight product stripping tower and the 35-45 degree Celsius hydrolysis product from the auxiliary agent bed A exchange heat, maintaining the light-weight product stripping tower level at 50-60%. The 80-95 degree Celsius hydrolysis product exiting the E2103 heat exchanger then passes through a plate heat exchanger and is further cooled to 35-50 degrees Celsius by circulating water. The cooled hydrolysis product then enters the auxiliary agent bed A for further removal of any contaminants. The hydrolysis product then flows out of the auxiliary agent bed A and passes through the E2103 heat exchanger, where it obtains heat energy from the hydrolysis product in the light sludge removal tower, raising the temperature to 85-100 degrees Celsius. The hot hydrolysis product then enters the subsequent system through the E2103 heat exchanger.

[0025] After the crude hydrolysis product is processed with hydrocarbon compounds, the oil phase hydrocarbons contain 56% cyclic compounds and 44% linear compounds, with an acid content of 0.1% and a viscosity of 20 mPa·s. The yield of the hydrolysis product after distillation is 99.6%, the purity is higher than 99%, and the quality meets the process requirements.

[0026] Comparative Example 1

[0027] In the traditional process, the crude hydrolysate is fed at a rate of 10 t / h into a water-washing stirred tank A for washing at 40-50 degrees Celsius. It then flows through a phase separator A for oil-water separation to remove acid and water. The overflow from the phase separator is then transferred to an alkaline washing stirred tank for further alkaline washing with 5% sodium hydroxide to remove hydrocarbons and chloride ions. After alkaline washing, the crude hydrolysate enters a phase separator B for oil-water separation. The hydrolysate is then further purified and washed in water-washing tank B to remove hydrocarbons, acid, and water. Finally, it undergoes oil-water separation in a phase separator C, and the hydrolysate is allowed to settle before entering the subsequent system. While this traditional three-stage washing process ensures the quality of the final product, it is cumbersome, has a lower separation efficiency than the method described in this patent, and suffers from even worse separation when the crude hydrolysate feed rate is too high, limiting its feed capacity.

[0028] After three-stage washing, the crude hydrolysis product contains 45% cyclic hydrocarbons and 55% linear hydrocarbons in the oil phase, with an acid content of 0.3% and a viscosity of 22-30 mPa·s. The yield of the hydrolysis product after distillation is 99.0%, with a purity higher than 99%, and the quality meets the process requirements.

[0029] Comparative Example 2

[0030] The crude hydrolysate feed rate is 25 t / h. After passing through a product heat exchanger, the crude hydrolysate exchanges heat with subsequent hot-wire products at a temperature of 85-95℃. It then enters the light oil removal tower preheater for further heating to achieve optimal operation, at a temperature of 100-110℃. The preheated crude hydrolysate is a vaporized feed, entering the light oil removal tower from the top of the stripping section. Inside the tower, most hydrocarbons, D3 rings, all residual water / acids, and some D4 rings vaporize before entering the rectification section. The top temperature of the tower is 115-123℃, and the pressure inside the tower is 15-20 kPa. The hydrocarbon feed then enters the light oil removal tower top condenser, with the condenser outlet temperature controlled at 55-65℃, for further condensation into the light oil removal tower reflux tank. The rectification product enters the light oil removal tower reflux tank for acid-oil separation. Adding hexane to the reflux tank of the light hydrocarbon removal tower at a feed ratio of 0.075 increases the density difference between the oil and water phases, promotes the separation of hydrocarbons and water, and improves the oil-water separation rate of the reaction system, while also removing chlorides from the hydrolysate. However, its flash point is -25.5 degrees Celsius, making it highly flammable and explosive during use, increasing operational risks.

[0031] While the specific embodiments and control methods of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for purifying siloxanes using hydrocarbon compounds, characterized in that, Includes the following steps: (1) The feed rate of crude hydrolysate is 25t / h. After the crude hydrolysate passes through the product heat exchanger and exchanges heat with the subsequent hot wire product, the temperature is 85-95℃. Then it enters the light removal tower preheater to further heat the crude hydrolysate to achieve the best operating effect of the light removal tower, with a temperature of 100-110℃. The preheated crude hydrolysate is a vaporized feed that enters the light removal tower from the top of the stripping section. In the tower, most hydrocarbons, D3 rings, all residual water / acids and some D4 rings are vaporized and then enter the rectification section. The top temperature of the tower is 115-123℃ and the pressure inside the tower is 15-20Kpa. The hydrocarbon feed then enters the top condenser of the light hydrocarbon removal tower, where the outlet temperature is controlled at 55-65℃. The hydrocarbons are further condensed into the reflux tank of the light hydrocarbon removal tower. The distillation product enters the reflux tank for acid-oil separation. Heptane is added to the reflux tank at a feed ratio of 0.075 to increase the density difference between the water and oil phases, promoting the separation of hydrocarbons and water, increasing the oil-water separation rate of the reaction system, and simultaneously removing chlorides from the hydrolysate. The reflux portion concentrates the hydrocarbon feed, reducing impurities in the hydrolysate. A portion of the circulating liquid is returned to the first reactor to facilitate the separation of acids and siloxanes. (2) In the stripping section, the hydrolysis product flows from the feed inlet of the light-light removal tower to the distribution plate, flows down through the packing section to the tower bottom, and the heat is supplied by the reboiler of the light-light removal tower to ensure that the tower bottom temperature is controlled at 210-230 degrees, so that the hydrolysis product does not contain any residual hydrocarbons. The hydrolysis product is pumped into the E2103 heat exchanger by the light-light removal tower bottom liquid pump. The 210-230 degree hydrolysis product from the light-light removal tower and the 35-45 degree hydrolysis product from the auxiliary agent A bed exchange heat to control the light-light removal tower liquid level to be stable at 50-60%. The 80-95 degree hydrolysis product coming out of the E2103 heat exchanger passes through the plate heat exchanger and is further cooled to 35-50 degrees by circulating water. Then the cooled hydrolysis product enters the auxiliary agent A bed for further removal of contaminants. The hydrolysis product then flows out of the auxiliary agent bed A and passes through the E2103 heat exchanger, where it obtains heat energy from the hydrolysis product in the light sludge removal tower, raising the temperature to 85-100 degrees Celsius. The hot hydrolysis product then enters the subsequent system through the E2103 heat exchanger.

2. The method according to claim 1, characterized in that, In step (1), the light-weight removal tower is divided into two different functional sections: the bottom section or stripping section has a diameter of 1.9m, and the middle section has two packing sections; the top section or rectification section is shorter and the stripping section has a diameter of 0.7m, and the rectification section includes one packing section.

3. The method according to claim 2, characterized in that, In step (1), the packing material of the packing section is a ceramic Pall ring.

4. The method according to claim 1, characterized in that, In step (2), the additive in the additive bed A is an anionic resin.

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