Process and device for recycling chlorosilane in tail gas and purifying acetic acid

Abstract

The invention belongs to the technical field of organic silicon, and particularly discloses treatment equipment and a treatment method for recycling chlorosilane in tail gas and purifying acetic acid. According to the method provided by the invention, the problems of recycling of chlorosilane in the HCL tail gas and adverse reaction of iron ions on chlorosilane acylation can be solved at the same time, and a high-quality target product is obtained. According to the device, chlorosilane in tail gas can be efficiently reacted and absorbed through acetic acid steam, meanwhile, chlorosilane is converted into part of substitutes which can be continuously used as raw materials, the atom utilization rate is high, and good economic benefits are achieved. Meanwhile, an acetic acid purification effect can be realized, the content of iron ions in acetic acid is greatly reduced, and the purified acetic acid is taken as a synthesis raw material, so that the product quality can be remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of organosilicon silane manufacturing, and particularly relates to a process and a device for recovering tail gas chlorosilane and purifying acetic acid. Background Art

[0002] Triacetoxysilane is mainly used as a vulcanizing agent for one-component deacetated silicone adhesive. Its synthesis method is the most economical preparation process of the reaction of chlorosilane and carboxylic acid, such as US Patent US3974198 and Chinese Patent CN104926856. This preparation method is suitable for industrial-scale mass production, but it also has certain defects. First, the reaction of chlorosilane and carboxylic acid produces a large amount of HCL gas. During the heating process, the HCL gas will carry the chlorosilane to escape, especially the reaction of low-boiling methyltrichlorosilane with carboxylic acid. The loss of silane can reach more than 5%, resulting in a decrease in yield and an increase in the difficulty of subsequent tail gas treatment. Secondly, the acylation of chlorosilane has strict requirements on the iron ion concentration in the system. There is evidence that when the iron ion concentration in the system exceeds 4ppm, the reactant polymer increases sharply, and the yield of the target product triacetoxysilane monomer decreases by more than 20%.

[0003] CN101628710 discloses a method for purifying hydrogen chloride containing chlorosilane, which is limited to the treatment of hydrogen chloride gas containing trace amounts of chlorosilane. When treating hydrogen chloride gas with a chlorosilane concentration exceeding 5%, hydrolysis produces a large amount of silicon slag, which can cause system blockage and cannot recover chlorosilane. CN116078097 discloses a process and device for treating acyloxysilane tail gas, which can recover chlorosilane and acetic acid in the tail gas, but the method is limited to treating desulfurization tail gas and cannot treat synthetic tail gas. In addition, the method uses low-temperature acetic acid for physical absorption, and the absorption efficiency is low.

[0004] Iron ions in the reaction system are mainly brought in by glacial acetic acid. Iron containers are used in the storage and transportation of glacial acetic acid. In particular, in winter, to prevent crystallization, the containers are equipped with a heating system. The iron ion concentration in glacial acetic acid even exceeds 30ppm under high temperature conditions. In order to prevent the influence of iron ions on chlorosilane acylation, iron complexing agents such as ethylenediaminetetraacetic acid and acetylacetone are usually added to the system to reduce the generation of side reactions. For example, U.S. Patent No. 3,974,198 discloses a method for preparing triacetoxysilane. Chlorosilane, glacial acetic acid and solvent are added with an iron ion complexing agent to obtain an ideal target product yield, but in actual verification, the product color will be deepened, and the product needs to be further decolorized.

[0005] In view of the above, the present invention provides a process and device for recovering chlorosilane from tail gas and purifying acetic acid, which simultaneously solves the problem of recovering chlorosilane from HCL tail gas and the adverse reaction of iron ions to acylation of chlorosilane, thereby obtaining a high-quality target product. Summary of the invention

[0006] The object of the present invention is to provide a process and device for recovering chlorosilane from tail gas and purifying acetic acid. Through the method provided by the present invention, it is possible to simultaneously solve the problem of recovering chlorosilane from HCl tail gas and the adverse reaction of iron ions to acylation of chlorosilane, and obtain a high-quality target product.

[0007] The technical solution adopted by the present invention is to provide a processing device for recovering chlorosilane from tail gas and purifying acetic acid, comprising: a metering pump connected to a flow meter, the flow meter connected to an evaporator, the evaporator connected to a packing tower, the bottom of the packing tower connected to a silane receiving tank, the top connected to a condenser, the bottom of the condenser connected to an acetic acid receiving tank, and the bottom of the silane receiving tank connected to the bottom of the acetic acid receiving tank.

[0008] Furthermore, the tail gas carries chlorosilane into the evaporator from the lower part, and acetic acid enters the evaporator through a metering pump to generate acetic acid vapor. The acetic acid vapor and the tail gas enter the packed tower together from the lower part, and the two are fully contacted and reacted in the packed tower.

[0009] The present invention also relates to a method for recovering chlorosilane from tail gas and purifying acetic acid, which uses the above-mentioned device and comprises the following steps: (1) Open the steam inlet and outlet valves of the evaporator. The glacial acetic acid enters the evaporator at a uniform speed to be fully vaporized through the flow meter to control the flow rate of the metering pump. The vaporized acetic acid vapor enters the packed tower from the top outlet of the evaporator.

[0010] (2) The chlorosilane tail gas enters the packed tower through the bottom, and fully contacts and reacts with the acetic acid vapor between the packings. Some of the substitutes generated by the reaction and a small amount of condensed acetic acid liquid fall into the silane receiving tank.

[0011] (3) After the removal of chlorosilane, the HCL tail gas and acetic acid vapor enter the condenser through the top of the packed tower, and the acetic acid is condensed into liquid and enters the acetic acid collection tank. The tail gas after the acetic acid is separated enters the next step through the bottom of the condenser and is treated according to the existing known technology.

[0012] Furthermore, in step (1), the temperature of the acetic acid vapor is controlled at 140-175° C., and the pressure is controlled at 1-20 kPa. More preferably, the temperature of the acetic acid vapor is controlled at 145-175° C., and the pressure is controlled at 5-10 kPa.

[0013] Furthermore, in step (1), the feed flow rate is controlled at 200-500 kg / h, and more preferably, the feed flow rate is controlled at 350-400 kg / h.

[0014] Furthermore, in step (2), the packed tower is maintained at a temperature of 140 to 160°C, and more preferably, the packed tower is maintained at a temperature of 150 to 160°C.

[0015] Furthermore, the tail gas components in step (2) include one or more of acetic acid, hydrogen chloride, methyltrichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, and acetoxysilane.

[0016] Furthermore, the packing used in the packed tower in step (2) is one of ceramic ball rings and ceramic corrugated packing.

[0017] Furthermore, in step (2), in order to avoid thermal decomposition of the substitute, condensed water is circulated through the silane receiving tank to maintain the tank temperature at 40-50°C.

[0018] Furthermore, in step (3), the condensation temperature is controlled at 5 to 15°C.

[0019] Furthermore, the known technology described in step (3) is water washing spray absorption.

[0020] The beneficial effects of the present invention are (1) The reaction between acetic acid and chlorosilane is an endothermic reversible reaction. Compared with liquid acetic acid, acetic acid vapor has a higher temperature and stronger reaction activity. The use of acetic acid vapor can efficiently realize the reaction and absorption of chlorosilane in the exhaust gas. At the same time, chlorosilane is converted into partial substitutes and can continue to be used as raw materials. The atomic utilization rate is high and it has good economic benefits.

[0021] (2) The device can simultaneously purify acetic acid and significantly reduce the iron ion content in acetic acid. Using the purified acetic acid as a synthetic raw material can significantly improve product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a diagram of the device for recovering chlorosilane from tail gas and purifying acetic acid, including a metering pump 1, a flow meter 2, an evaporator 3, a packing tower 4, a condenser 5, a silane receiving tank 6, and an acetic acid receiving tank 7. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] A processing device for recovering chlorosilane from tail gas and purifying acetic acid, wherein a metering pump 1 is connected to a flow meter 2, the flow meter 2 is connected to an evaporator 3, the evaporator 3 is connected to a packing tower 4, the packing tower 4 is connected to a silane receiving tank 6 at the bottom, and to a condenser 5 at the top, the condenser 5 is connected to an acetic acid receiving tank 7 at the bottom, the silane receiving tank 6 is connected to the bottom of the acetic acid receiving tank 7 at the bottom, the tail gas carries chlorosilane and enters from the bottom of the evaporator 3, acetic acid enters the evaporator 3 through the metering pump 1, acetic acid vapor is generated, the acetic acid vapor and the tail gas enter from the bottom of the packing tower 4 together, and fully contact and react in a packing layer.

[0025] Open the steam inlet and outlet valves of evaporator 3. The glacial acetic acid controls the flow rate of the metering pump through the flow meter. The feed flow rate is controlled at 350-400 kg / h. It enters the evaporator at a uniform speed for full vaporization. The acetic acid vapor temperature is maintained at 145-175°C and the pressure is maintained at 5-10 kPa. The vaporized acetic acid vapor enters the packed tower 4 from the top outlet of the evaporator.

[0026] The packed tower is maintained at a temperature of 140-150°C. The tail gas containing chlorosilane enters through the bottom of the evaporator and fully contacts and reacts with the acetic acid vapor between the packings. Usually, this reaction rate is very fast. However, the present invention does not require complete substitution of chlorosilane. The partial substitution of trichlorosilane can also achieve the separation requirement due to the increase in boiling point. This substitution is a mixture of complete substitution or partial substitution, and falls into the silane receiving tank 6 with a small amount of condensed acetic acid liquid. In order to avoid thermal decomposition of the substitution, the silane receiving tank is circulated with condensed water to maintain the tank temperature at 40-50°C.

[0027] The HCl tail gas after the removal of chlorosilane and the acetic acid vapor enter the condenser 5 through the top of the packed tower, and the acetic acid is condensed into liquid and enters the acetic acid collection tank 7. The HCl tail gas after the acetic acid is separated enters the next step through the bottom of the condenser and is processed according to the existing known technology.

[0028] The materials in the silane receiving tank and the acetic acid receiving tank are used as acetic acid raw materials to supply the front-end batching process, so that the system is completely free of iron ions, and the process of the following embodiment is carried out.

[0029] Example 1 Add 1600kg of the above-mentioned silane receiving tank and acetic acid receiving tank materials (mainly AcOH, containing a small amount of acetoxysilane) into the reactor, add 400kg of methyltrichlorosilane (MeSiCl3) dropwise, reflux at 70℃ for 1h, transfer the kettle liquid to the desulfurization kettle, desulfurize at 110℃ for 3h, collect and recover 1020kg of glacial acetic acid and 488kg of product methyltriacetoxysilane. The synthetic tail gas and desulfurization tail gas are collected and fed into the above-mentioned device, and acetic acid is pumped into the evaporator at a rate of 150kg / h through a metering pump. The acetic acid vapor temperature is 160℃ and the pressure is 5kPa. The acetic acid vapor and the collected tail gas are fully contacted and reacted in the packed tower. The temperature in the packed tower is 140-150℃. A small amount of acetoxysilane produced by the reaction enters the silane receiving tank together with the acetic acid. The excess acetic acid vapor is condensed by the condenser into acetic acid liquid and enters the acetic acid receiving tank. The materials of the silane receiving tank and the acetic acid receiving tank are reused as synthetic raw materials. After the above treatment, the tail gas is used to prepare hydrochloric acid through water washing and spraying. The water washing and spraying tower operates normally and no obvious silicon slag is produced.

[0030] Example 2 Add 580kg of the above-mentioned silane receiving tank and acetic acid receiving tank materials (mainly AcOH, containing a small amount of acetoxysilane) into the reactor, recover 1020kg of glacial acetic acid, drop 400kg of methyltrichlorosilane (MeSiCl3), reflux at 70℃ for 1h, transfer the kettle liquid to the desulfurization kettle, desulfurize at 110℃ for 3h, collect and obtain 983kg of recovered glacial acetic acid and 502kg of product methyltriacetoxysilane. The synthetic tail gas and desulfurization tail gas are collected and fed into the above-mentioned device, and acetic acid is pumped into the evaporator at a rate of 150kg / h through a metering pump. The acetic acid vapor temperature is 160℃ and the pressure is 5kPa. The acetic acid vapor and the collected tail gas are fully contacted and reacted in the packed tower. The temperature in the packed tower is 140-150℃. A small amount of acetoxysilane produced by the reaction enters the silane receiving tank together with the acetic acid. The excess acetic acid vapor is condensed into acetic acid liquid through the condenser and enters the acetic acid receiving tank. The materials in the silane receiving tank and the acetic acid receiving tank are reused as synthetic raw materials. After the above treatment, the tail gas is sprayed with water to prepare hydrochloric acid. The water spray tower operates normally and no obvious silicon slag is produced.

[0031] Comparative Example 1 1600kg of glacial acetic acid was added to the reactor, and 400kg of methyltrichlorosilane (MeSiCl3) was added dropwise. After reflux reaction at 70℃ for 1h, the reactor liquid was transferred to the desulfurization reactor, and desulfurization was carried out at 110℃ for 3h. 1036kg of recovered glacial acetic acid and 483kg of product methyltriacetoxysilane were collected. The synthetic tail gas and desulfurization tail gas were collected and fed into the above-mentioned device. At the same time, acetic acid was pumped into the evaporator at a rate of 150kg / h through a metering pump. The acetic acid vapor temperature was 160℃ and the pressure was 5kPa. The acetic acid vapor and the collected tail gas were fully contacted and reacted in the packed tower. The temperature in the packed tower was 140℃. A small amount of acetoxysilane produced by the reaction entered the silane receiving tank together with acetic acid. The excess acetic acid vapor was condensed by the condenser into acetic acid liquid and entered the acetic acid receiving tank. The materials of the silane receiving tank and the acetic acid receiving tank were reused as synthetic raw materials. After the above treatment, the tail gas was sprayed with water to prepare hydrochloric acid. The water washing spray tower operated normally without producing obvious silicon slag.

[0032] Comparative Example 2 Add 1600kg of the above-mentioned silane receiving tank and acetic acid receiving tank materials (mainly AcOH, containing a small amount of acetoxysilane) into the reactor, add 400kg of methyltrichlorosilane (MeSiCl3) dropwise, reflux at 70℃ for 1h, transfer the kettle liquid to the desulfurization kettle, desulfurize at 110℃ for 3h, and collect 1024kg of recovered glacial acetic acid and 462kg of product methyltriacetoxysilane. The synthetic tail gas and desulfurization tail gas are directly used to prepare hydrochloric acid through water washing and spraying. The water washing spray tower is blocked after half an hour, and obvious silicon slag can be seen in the hydrochloric acid.

[0033] Comparative Example 3 Add 1600kg of the above-mentioned silane receiving tank and acetic acid receiving tank materials (mainly AcOH, containing a small amount of acetoxysilane) into the reactor, add 400kg of methyltrichlorosilane (MeSiCl3) dropwise, reflux at 70℃ for 1h, transfer the kettle liquid to the desulfurization kettle, desulfurize at 110℃ for 3h, collect and recover 1016kg of glacial acetic acid and 491kg of product methyltriacetoxysilane. The synthetic tail gas and desulfurization tail gas are collected and fed into the above-mentioned device, and acetic acid is pumped into the evaporator at a rate of 150kg / h through a metering pump. The acetic acid vapor temperature is 120℃ and the pressure is 0.5kPa. The acetic acid vapor and the collected tail gas are fully contacted and reacted in the packed tower. The temperature in the packed tower is 120℃. A small amount of acetoxysilane produced by the reaction enters the silane receiving tank together with the acetic acid. The excess acetic acid vapor is condensed by the condenser into acetic acid liquid and enters the acetic acid receiving tank. The materials of the silane receiving tank and the acetic acid receiving tank are reused as synthetic raw materials. After the above treatment, the tail gas is used to prepare hydrochloric acid through water washing and spraying. The water washing and spraying tower operates basically normally and produces a small amount of silicon slag.

[0034] The methyltriacetoxysilane produced in the examples and comparative examples was analyzed by gas chromatography, and the iron ion detection and analysis were performed on the glacial acetic acid in the tank area, the recovered glacial acetic acid, the silane receiving tank and the acetic acid receiving tank materials. The data are as follows.

[0035] Table 1 Product chromatographic result record Component batch Methyltriacetoxysilane / % Dimer / % Trimers and polymers / % Example 1 91.02 3.21 1.06 Example 2 88.69 5.65 3.72 Comparative Example 1 62.04 22.12 8.92 Comparative Example 2 83.12 8.36 3.96 Comparative Example 3 82.68 9.22 4.76 Table 2 Iron ion detection results materials Glacial acetic acid in tank area Recovery of glacial acetic acid Silane receiving tank Acetic acid receiving tank Iron ion content / ppm 5.3 1.6 1.2 1.1 As can be seen from Table 2, the iron ion content in the tank area glacial acetic acid is high, and the iron ion content in the silane receiving tank and acetic acid receiving tank materials obtained by the low recovery of glacial acetic acid and the treatment of the device is reduced to less than 2ppm. In conjunction with Table 1 and Table 2 data, it can be seen that when using tank area glacial acetic acid, due to iron ion interference, the monomer content in the product is significantly reduced, and polymer increases, proving that the set of devices can successfully achieve acetic acid purification. It can be seen from Example 1 and Comparative Example 2 that the untreated direct water washing absorption of chlorosilane tail gas can cause system blockage, and it is difficult to operate normally, and by the set of devices, chlorosilanes are successfully absorbed in the tail gas, and no obvious silicon slag is seen when washing to prepare hydrochloric acid, and the system operates normally. It can be seen from Example 1 and Comparative Example 3 that the acetic acid vapor temperature is increased, and reacting is conducive to promoting the reaction recovery of chlorosilanes in the tail gas.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A treatment device for recovering chlorosilane from tail gas and purifying acetic acid, characterized in that: The metering pump is connected to the flow meter, the flow meter is connected to the evaporator, the evaporator is connected to the packing tower, the bottom of the packing tower is connected to the silane receiving tank, the top is connected to the condenser, the bottom of the condenser is connected to the acetic acid receiving tank, and the bottom of the silane receiving tank is connected to the bottom of the acetic acid receiving tank.

2. The processing device for recovering chlorosilane from tail gas and purifying acetic acid according to claim 1, characterized in that: The tail gas carries chlorosilane into the evaporator from the bottom, and acetic acid enters the evaporator through a metering pump to generate acetic acid vapor. The acetic acid vapor and the tail gas enter the packed tower from the bottom together, and the two are fully contacted and reacted in the packed tower.

3. A method for recovering chlorosilane from tail gas and purifying acetic acid, using the device according to claim 1 or 2, characterized in that: The steps include: (1) Open the steam inlet and outlet valves of the evaporator. The glacial acetic acid enters the evaporator at a uniform speed and is fully vaporized through the flow meter to control the flow rate of the metering pump. The vaporized acetic acid vapor enters the packed tower from the top outlet of the evaporator; (2) The chlorosilane tail gas enters the packed tower from the bottom, fully contacts and reacts with the acetic acid vapor between the packings, and some of the substitutes generated by the reaction and a small amount of condensed acetic acid liquid fall into the silane receiving tank; (3) After the removal of chlorosilane, the tail gas containing HCl and acetic acid vapor enter the condenser through the top of the packed tower. The acetic acid is condensed into liquid and enters the acetic acid collection tank. The tail gas after the acetic acid is separated is absorbed by water washing spray.

4. The method for recovering chlorosilane from tail gas and purifying acetic acid according to claim 3, characterized in that: In step (1), the temperature of the acetic acid vapor is controlled at 140-175° C., and the pressure is controlled at 1-20 kPa. More preferably, the temperature of the acetic acid vapor is controlled at 145-175° C., and the pressure is controlled at 5-10 kPa.

5. The method for recovering chlorosilane from tail gas and purifying acetic acid according to claim 3, characterized in that: In step (1), the feed flow rate is controlled at 200-500 kg / h, and more preferably, the feed flow rate is controlled at 350-400 kg / h.

6. The method for recovering chlorosilane from tail gas and purifying acetic acid according to claim 3, characterized in that: In step (2), the packed tower is maintained at a temperature of 140 to 160°C. More preferably, the packed tower is maintained at a temperature of 150 to 160°C.

7. The method for recovering chlorosilane from tail gas and purifying acetic acid according to claim 3, characterized in that: The tail gas components in step (2) include one or more of acetic acid, hydrogen chloride, methyltrichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, and acetoxysilane.

8. The method for recovering chlorosilane from tail gas and purifying acetic acid according to claim 3, characterized in that: The packing used in the packed tower in step (2) is one of ceramic ball rings and ceramic corrugated packing.

9. The method for recovering chlorosilane from tail gas and purifying acetic acid according to claim 3, characterized in that: In step (2), to avoid thermal decomposition of the substitute, condensed water is circulated through the silane receiving tank to maintain the tank temperature at 40-50°C.

10. The method for recovering chlorosilane from tail gas and purifying acetic acid according to claim 3, characterized in that: In step (3), the condensation temperature is controlled at 5 to 15°C.

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