Equipment and method for treating acetoxysilane tail gas

Abstract

The invention belongs to the technical field of organic silicon, and particularly discloses acetoxysilane tail gas treatment equipment and method.The equipment comprises multiple sets of tower reactors, water washing towers and alkaline washing towers which are arranged in series, a tail gas pipeline is connected with a gas inlet of the first-stage tower reactor, and an acetic acid feeding port and a gas phase outlet are formed in the upper portion of each tower reactor; a gas phase outlet is connected to a gas inlet of the next-stage tower reactor through a condenser and a gas-liquid separator, and a gas phase from the last-stage tower reactor enters a water washing tower and an alkaline washing tower and then is connected with an emptying pipeline. According to the invention, the tail gas is treated by the multi-stage tower reactor and acetic acid, acetic acid and chlorosilane are rapidly reacted, chlorosilane in the acetoxysilane tail gas is efficiently removed, and chlorosilane is converted into a substitute of which part of chlorine is substituted by acetoxy or acetoxysilane, so that the industrial problem that the acetoxysilane tail gas carries chlorosilane can be effectively solved; and meanwhile, good economic benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of organic silicon, and particularly relates to equipment and a method for treating acetoxysilane tail gas. Background Art

[0002] Industrially, the manufacturing methods of acetoxysilane generally include the acetic acid method and the acetic anhydride method. The main difference between the two is the different acyl oxidation reagents used. The acetic anhydride method uses acetic anhydride as the raw material, which is relatively expensive. The byproduct acetyl chloride is complicated to purify and process. At the same time, the product has a strong pungent odor and is easy to crystallize at low temperatures. The advantages of the acetic acid method are that the raw material acetic acid is low in price, and the product has a light odor, light color, and high activity. However, the acetic acid method has high requirements for process, equipment, and tail gas treatment, and is difficult to develop.

[0003] The tail gas produced by the acetic acid method for preparing acetoxysilane is mainly composed of chlorosilane, acetic acid and HCl gas. Directly spraying the tail gas to absorb the water consumption is large, and the reaction of chlorosilane and water to form silicon slag can easily cause the spray tower to be blocked, hindering the normal operation of the system. Therefore, it is necessary to find a suitable process and equipment to treat the tail gas.

[0004] CN116078097A proposes a process and device for treating acyloxysilane tail gas, which uses acetic acid as the medium of a venturi jet pump, promotes the liquefaction of chlorosilane through efficient mass transfer and heat transfer, and recovers chlorosilane to the maximum extent. However, the liquefaction of chlorosilane is relatively difficult, and it is difficult to completely liquefy and recover it. The reaction activity of acetic acid is low at low temperatures, and only physical absorption has little effect on the recovery of gaseous chlorosilane. At the same time, the process and device are limited to treating the tail gas, and cannot treat the tail gas of acyloxysilane synthesis. Summary of the invention

[0005] The invention provides an acetoxysilane tail gas treatment device and method, wherein the tail gas is treated by a tower reactor, chlorosilane entrained in the tail gas is removed by reaction with acetic acid, and the remaining tail gas is washed and sprayed to prepare high-quality hydrochloric acid.

[0006] The technical solution of the present invention is to provide an acetoxysilane tail gas treatment device, comprising a plurality of tower reactors, water washing towers and alkali washing towers arranged in series, the tail gas pipeline is connected to the air inlet of the first-stage tower reactor, the upper part of the tower reactor is provided with an acetic acid addition port and a gas phase outlet, the gas phase outlet is connected to the air inlet of the next-stage tower reactor after passing through a condenser and a gas-liquid separator, and the gas phase coming out of the last-stage tower reactor enters the water washing tower and the alkali washing tower and is connected to a venting pipeline.

[0007] Furthermore, the tower reactor is one of a packed tower reactor, a plate tower reactor, a spray tower reactor and a membrane tower reactor.

[0008] Furthermore, a buffer collecting tank is provided at the lower part of the tower reactor, and the bottom of the buffer collecting tank is connected to the distillation equipment through a drainage pipe.

[0009] Furthermore, the liquid phase outlet of the gas-liquid separator is connected to the acetoxysilane synthesis section through a pipeline.

[0010] The present invention also relates to a method for treating acetoxysilane tail gas, comprising the following steps: introducing acetoxysilane tail gas from the lower part of a primary tower reactor, mixing and reacting with acetic acid introduced from the upper part, discharging the gas phase at the top of the tower reactor, condensing and separating the gas and liquid, reacting, condensing and separating the gas and liquid in a multi-stage tower reactor, and finally entering a water washing tower to wash with water to prepare hydrochloric acid. The gas phase after water washing finally enters an alkali washing tower to be alkali washed and then discharged; during the operation, the temperature in the tower reactor is controlled to be 80-120°C, and the acetic acid dripping speed in the tower reactor is 100-400 L / h; and the condenser temperature is controlled to be -10-20°C.

[0011] Furthermore, the tower reactor is three-stage, and the temperatures of the first-stage, second-stage and third-stage tower reactors are 80-100°C, 90-110°C and 100-120°C respectively, and the temperature of the first-stage tower reactor is less than the temperature of the second-stage tower reactor and less than the temperature of the third-stage tower reactor.

[0012] Furthermore, the acetic acid dropping speeds of the primary, secondary and tertiary tower reactors are 200-400 L / h, 150-300 L / h and 100-200 L / h, respectively; and the acetic acid dropping speed of the primary tower reactor is greater than the acetic acid dropping speed of the secondary tower reactor and greater than the acetic acid dropping speed of the tertiary tower reactor.

[0013] Furthermore, the temperatures of the condensers after the primary, secondary and tertiary tower reactors are 10-20°C, 0-15°C and -10-0°C, respectively, and the temperature of the primary condenser is > the temperature of the secondary condenser > the temperature of the tertiary condenser.

[0014] Furthermore, the liquid phase obtained after gas-liquid separation is recycled to the acetoxysilane synthesis section; the liquid phase obtained after the tower reactor reaction is separated by reduced pressure distillation to obtain the product acetoxysilane and the raw material acetic acid.

[0015] Furthermore, the reduced pressure distillation temperature is 80~120°C, and the vacuum degree is -0.085~-0.095MPa.

[0016] Furthermore, the tail gas components include one or more of acetic acid, hydrogen chloride, methyltrichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, and acetoxysilane.

[0017] The present invention has the following beneficial effects: (1) By utilizing the advantages of efficient mass and heat transfer of the tower reactor and the excess acetic acid to promote the rapid reaction of acetic acid and chlorosilane to form acetoxysilane, the chlorosilane in the tail gas of acetoxysilane can be efficiently removed, the quality of hydrochloric acid prepared by the tail gas washing tower can be improved, and the solid impurity content and turbidity in the hydrochloric acid can be reduced.

[0018] (2) A three-set tower reactor combination is used to gradiently control the acetic acid dripping acceleration, tower reactor temperature, and condenser temperature. Chlorosilane is first converted into a product in which part of the chlorine is replaced by acetoxy groups, and finally all the chlorine is replaced by acetoxy groups to obtain the product acetoxysilane. Through three-stage tower reaction and three-stage condensation recovery, the physical condensation recovery and chemical reaction absorption are combined to improve the tail gas chlorosilane absorption efficiency.

[0019] (3) The second and third stages increase the temperature and utilize the high temperature to generate some acetic acid vapor inside the tower reactor. The high chemical reactivity of acetic acid vapor is utilized to bring out some HCl gas at the same time, further improving the reaction absorption efficiency of chlorosilane.

[0020] (4) The chlorosilane in the tail gas is chemically absorbed by acetic acid, and the product acetoxysilane and the raw material acetic acid can be separated by vacuum distillation, which has high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural diagram of the equipment in Example 1 of the present invention. In the figure, R1, R2, and R3 are respectively the first-level, second-level, and third-level buffer collection tanks, T1, T2, and T3 are respectively the first-level, second-level, and third-level tower reactors, E1, E2, and E3 are respectively the first-level, second-level, and third-level condensers, V1, V2, and V3 are respectively the first-level, second-level, and third-level gas-liquid separators, T4 is a water washing absorption tower, T5 is an alkali washing absorption tower, P1 is a water washing circulation pump, and P2 is an alkali washing circulation pump.

[0022] Figure 2 This is the gas chromatogram of the first-level condensation recovery liquid in Example 2.

[0023] Figure 3 This is the gas chromatogram of the secondary condensation recovery liquid in Example 2.

[0024] Figure 4 This is the gas chromatogram of the three-stage condensation recovery liquid in Example 2.

[0025] Figure 5 This is the gas chromatogram of the product obtained after the liquid in the buffer collection tank in Example 2 was distilled under reduced pressure. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0027] Example 1 An acetoxysilane tail gas treatment device comprises a plurality of tower reactors, water washing towers and alkali washing towers arranged in series, wherein a tail gas pipeline is connected to an air inlet of a first-stage tower reactor, an acetic acid addition inlet and a gas phase outlet are arranged on the upper part of the tower reactor, the gas phase outlet is connected to an air inlet of a next-stage tower reactor after passing through a condenser and a gas-liquid separator, and the gas phase coming out of the last-stage tower reactor enters a water washing tower and an alkali washing tower and is connected to a venting pipeline.

[0028] In a preferred embodiment, a buffer collecting tank is provided at the bottom of the tower reactor, and the bottom of the buffer collecting tank is connected to a vacuum distillation device through a drainage pipe. The liquid in the kettle is separated by vacuum distillation to obtain acetoxysilane and acetic acid. Figure 1 As shown, the processing equipment is provided with three stages of series-connected tower reactors, three stages of condensers and three stages of gas-liquid separators.

[0029] In a preferred embodiment, the liquid phase outlet of the gas-liquid separator is connected to the acetoxysilane synthesis section through a pipeline.

[0030] Specifically, when the tail gas is treated, the acetoxysilane tail gas is introduced from the lower part of the first-stage tower reactor, mixed and reacted with the acetic acid introduced from the upper part, and the gas phase at the top of the tower reactor is discharged and condensed and separated into gas and liquid. The obtained gas phase is reacted, condensed and separated into gas and liquid by multi-stage tower reactors, and finally the separated gas phase enters the water washing tower for washing with water to prepare hydrochloric acid, and the gas phase after water washing finally enters the alkali washing tower for alkali washing and then emptied; during the operation, the temperature in the tower reactor is controlled to be 80~120℃, and the acetic acid dripping speed of the tower reactor is 100~400 L / h; the condenser temperature is controlled to be -10~20℃.

[0031] In a preferred embodiment, the temperatures of the primary, secondary and tertiary tower reactors are 80-100°C, 90-110°C, and 100-120°C, respectively, and the temperature of the primary tower reactor is less than the temperature of the secondary tower reactor and less than the temperature of the tertiary tower reactor. The acetic acid droplet speeds of the primary, secondary and tertiary tower reactors are 200-400 L / h, 150-300 L / h, and 100-200 L / h, respectively; and the acetic acid droplet speed of the primary tower reactor is greater than the acetic acid droplet speed of the secondary tower reactor and greater than the acetic acid droplet speed of the tertiary tower reactor. The temperatures of the condensers after the primary, secondary and tertiary tower reactors are 10-20°C, 0-15°C, and -10-0°C, respectively, and the temperature of the primary condenser is greater than the temperature of the secondary condenser and greater than the temperature of the tertiary condenser.

[0032] Example 2 Acetoxysilane tail gas treatment method Add 1600kg of glacial acetic acid (AcOH) and 400kg of methyltrichlorosilane (MeSiCl3) into the reactor, and prepare methyltriacetoxysilane through reaction and desulfurization. The synthetic tail gas and desulfurization tail gas are collected and enter the acetic acid washing system of the tower reactor. The first, second and third stage acetic acid droplet speeds are 200L / h, 150L / h and 100L / h respectively. The temperatures of the first, second and third stage tower reactors are 80℃, 90℃ and 100℃ respectively. The temperatures of the first, second and third stage condensers are 20℃, 10℃ and -10℃ respectively. After 2h, 642kg of liquid in the recovery kettle is collected and recovered. After reduced pressure distillation, 157kg of product is obtained. V1, V2 and V3 collect 51kg, 84kg and 88kg of condensed recovery liquid respectively. The remaining tail gas is absorbed by the water washing absorption tower to prepare hydrochloric acid, and then discharged after passing through the alkali washing absorption tower. No silicon slag is produced in the hydrochloric acid, and the turbidity is 0.78NTU.

[0033] Example 3 Add 1600kg of glacial acetic acid (AcOH) and 400kg of methyltrichlorosilane (MeSiCl3) into the reactor, and prepare methyltriacetoxysilane through reaction and desulfurization. The synthetic tail gas and desulfurization tail gas are collected and enter the acetic acid washing system of the tower reactor. The first, second and third stage acetic acid droplet speeds are 300L / h, 200L / h and 150L / h respectively. The temperatures of the first, second and third stage tower reactors are 80℃, 90℃ and 100℃ respectively. The temperatures of the first, second and third stage condensers are 20℃, 10℃ and -10℃ respectively. After 2h, 838kg of liquid in the recovery kettle is collected and recovered. After reduced pressure distillation, 173kg of product is obtained. V1, V2 and V3 collect 63kg, 85kg and 107kg of condensed recovery liquid respectively. The remaining tail gas is absorbed by the water washing absorption tower to prepare hydrochloric acid, and then discharged after passing through the alkali washing absorption tower. No silicon slag is produced in the hydrochloric acid, and the turbidity is 0.56NTU.

[0034] Example 4 Add 1600kg of glacial acetic acid (AcOH) and 400kg of methyltrichlorosilane (MeSiCl3) into the reactor, and prepare methyltriacetoxysilane through reaction and desulfurization. The synthetic tail gas and desulfurization tail gas are collected and enter the acetic acid washing system of the tower reactor. The first, second and third stage acetic acid droplet speeds are 200L / h, 150L / h and 100L / h respectively. The temperatures of the first, second and third stage tower reactors are 90℃, 100℃ and 110℃ respectively. The temperatures of the first, second and third stage condensers are 10℃, 5℃ and 0℃ respectively. After 2h, 668kg of liquid in the recovery kettle is collected and recovered. After reduced pressure distillation, 186kg of product is obtained. V1, V2 and V3 collect 58kg, 93kg and 102kg of condensed recovery liquid respectively. The remaining tail gas is absorbed by the water washing absorption tower to prepare hydrochloric acid, and then discharged after passing through the alkali washing absorption tower. No silicon slag is produced in the hydrochloric acid, and the turbidity is 0.43NTU. Example 5 1600kg of glacial acetic acid (AcOH) and 400kg of ethyltrichlorosilane (EtSiCl3) were added to the reactor to prepare ethyltriacetoxysilane through reaction and degassing. The synthetic tail gas and degassing tail gas were collected and entered into the acetic acid washing system of the tower reactor. The first, second and third stage acetic acid droplet speeds were 200L / h, 150L / h and 100L / h respectively. The temperatures of the first, second and third stage tower reactors were 80℃, 90℃ and 100℃ respectively. The temperatures of the first, second and third stage condensers were 20℃, 10℃ and -10℃ respectively. After 2h, 654kg of liquid in the recovery kettle was collected and recovered. After reduced pressure distillation, 112kg of product was obtained. V1, V2 and V3 collected 63kg, 78kg and 106kg of condensed recovery liquid respectively. The remaining tail gas was absorbed by the water washing absorption tower to prepare hydrochloric acid, and then discharged after passing through the alkali washing absorption tower. No silicon slag was produced in the hydrochloric acid, and the turbidity was 0.68NTU.

[0035] Example 6 Add 1600kg of glacial acetic acid (AcOH) and 400kg of propyltrichlorosilane (PrSiCl3) into the reactor, and prepare methyltriacetoxysilane through reaction and desulfurization. The synthetic tail gas and desulfurization tail gas are collected and enter the acetic acid washing system of the tower reactor. The first, second and third stage acetic acid droplet speeds are 200L / h, 150L / h and 100L / h respectively. The temperatures of the first, second and third stage tower reactors are 80℃, 90℃ and 100℃ respectively. The temperatures of the first, second and third stage condensers are 20℃, 10℃ and -10℃ respectively. After 2h, 630kg of liquid in the recovery kettle is collected and recovered. After reduced pressure distillation, 126kg of product is obtained. V1, V2 and V3 collect 56kg, 68kg and 108kg of condensed recovery liquid respectively. The remaining tail gas is absorbed by the water washing absorption tower to prepare hydrochloric acid, and then discharged after passing through the alkali washing absorption tower. No silicon slag is produced in the hydrochloric acid, and the turbidity is 0.63NTU.

[0036] Comparative Example 1 1600kg of glacial acetic acid (AcOH) and 400kg of methyltrichlorosilane (MeSiCl3) were added to the reactor to prepare methyltriacetoxysilane through reaction and desulfurization. The synthetic tail gas and desulfurization tail gas were directly sent to the water washing absorption tower to prepare hydrochloric acid. The hydrochloric acid produced contained a large amount of silicon slag. At the same time, the circulating pump of the water washing absorption tower was blocked after running for 1 hour, resulting in the inability to continue running. This proves that the acetoxysilane tail gas cannot be directly absorbed by water washing without treatment.

[0037] Comparative Example 2 1600kg of glacial acetic acid (AcOH) and 400kg of methyltrichlorosilane (MeSiCl3) were added to the reactor to prepare methyltriacetoxysilane through reaction and desulfurization. The synthetic tail gas and desulfurization tail gas were collected and entered into the acetic acid washing system of the tower reactor. The first, second and third stage acetic acid drop rates were 200L / h, 150L / h and 100L / h respectively. The temperatures of the first, second and third stage tower reactors were all at room temperature without heating. The temperatures of the first, second and third stage condensers were 20℃, 10℃ and -10℃ respectively. The remaining tail gas was absorbed by the water washing absorption tower to prepare hydrochloric acid, and then discharged after passing through the alkaline washing absorption tower. The produced hydrochloric acid contained a large amount of silicon slag. At the same time, the circulating pump of the water washing absorption tower was blocked after running for 1h, resulting in the inability to continue to operate. It was proved that room temperature acetic acid washing could not treat acetoxysilane tail gas.

[0038] Comparative Example 3 1600 kg of glacial acetic acid (AcOH) and 400 kg of methyltrichlorosilane (MeSiCl3) were added into the reactor to prepare methyltriacetoxysilane through reaction and deoxidation. The synthetic tail gas and the de-low tail gas are collected and then enter the acetic acid washing system of the tower reactor. The acetic acid droplet speeds of the first, second and third stages are 200L / h, 150L / h and 100L / h respectively. The temperatures of the first, second and third stage tower reactors are 80℃, 90℃ and 100℃ respectively. No cooling medium is introduced into the first, second and third stage condensers. After 2h, 657kg of liquid in the recovery kettle is collected and recovered. 162kg of product is obtained after reduced pressure distillation. 12kg, 18kg and 20kg of condensed recovery liquid are collected from V1, V2 and V3 respectively. The remaining tail gas is absorbed by a water washing absorption tower to prepare hydrochloric acid, and then discharged after passing through an alkali washing absorption tower. Trace silicon slag is produced in the hydrochloric acid, and the turbidity is 1.42NTU. This proves that the three-stage condensation can physically recover part of the chlorosilanes and their substitutes, thereby improving the recovery efficiency of chlorosilanes in the tail gas.

[0039] As described above, after the acetoxysilane tail gas is washed with acetic acid in a three-stage tower reactor, the chlorosilane in the tail gas reacts with acetic acid, and the product acetoxysilane and the raw material acetic acid are obtained by reduced pressure distillation. The remaining tail gas is sprayed with water for absorption to prepare hydrochloric acid. There is no silicon slag in the hydrochloric acid, the tail gas absorption effect is good, and it has high economic benefits.

[0040] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An acetoxysilane tail gas treatment device, characterized in that: The method comprises a plurality of tower reactors, water washing towers and alkali washing towers which are arranged in series. The tail gas pipeline is connected to the air inlet of the first-stage tower reactor. An acetic acid addition port and a gas phase outlet are arranged on the upper part of the tower reactor. The gas phase outlet is connected to the air inlet of the next-stage tower reactor after passing through a condenser and a gas-liquid separator. The gas phase coming out of the last-stage tower reactor enters the water washing tower and the alkali washing tower and is then connected to a venting pipeline.

2. The device according to claim 1, characterized in that: The tower reactor is one of a packed tower reactor, a plate tower reactor, a spray tower reactor or a membrane tower reactor.

3. The device according to claim 1, characterized in that: A buffer collecting tank is arranged at the lower part of the tower reactor; the bottom of the buffer collecting tank is connected to the distillation equipment through a drainage pipe; and the liquid phase outlet of the gas-liquid separator is connected to the acetoxysilane synthesis section through a pipe.

4. A method for treating acetoxysilane tail gas, characterized in that: The following steps are involved: The acetoxysilane synthesis tail gas and the degassing tail gas are collected and introduced from the lower part of the first-stage tower reactor to react with the acetic acid introduced from the upper part. The gas phase at the top of the tower reactor is discharged and condensed and separated into gas and liquid. The obtained gas phase is reacted, condensed and separated into gas and liquid in a multi-stage tower reactor. Finally, the separated gas phase enters a water washing tower to be washed with water to prepare hydrochloric acid. The gas phase after water washing finally enters an alkali washing tower and is discharged after alkali washing. During the operation, the temperature in the tower reactor is controlled to be 80~120℃, and the acetic acid dripping speed in the tower reactor is 100~400 L / h; the condenser temperature is controlled to be -10~20℃.

5. The method according to claim 4, characterized in that: The tower reactor is three-stage, and the temperatures of the first-stage, second-stage and third-stage tower reactors are 80-100° C., 90-110° C. and 100-120° C. respectively, and the temperature of the first-stage tower reactor is less than the temperature of the second-stage tower reactor and less than the temperature of the third-stage tower reactor.

6. The method according to claim 4, characterized in that: The acetic acid dropping speeds of the primary, secondary and tertiary tower reactors are 200~400 L / h, 150~300 L / h and 100~200 L / h, respectively; and the acetic acid dropping speed of the primary tower reactor is greater than that of the secondary tower reactor and greater than that of the tertiary tower reactor.

7. The method according to claim 4, characterized in that: The temperatures of the condensers after the primary, secondary and tertiary tower reactors are 10~20°C, 0~15°C and -10~0°C respectively, and the temperature of the primary condenser is > the temperature of the secondary condenser > the temperature of the tertiary condenser.

8. The method according to any one of claims 4 to 7, characterized in that: The liquid phase obtained after gas-liquid separation is recycled to the acetoxysilane synthesis section; the liquid phase obtained after the tower reactor reaction is separated by reduced pressure distillation to obtain the product acetoxysilane and the raw material acetic acid.

9. The method according to claim 8, characterized in that: The reduced pressure distillation temperature is 80~120℃, and the vacuum degree is -0.085~-0.095MPa.

10. The method according to claim 4, characterized in that: The tail gas components include one or more of acetic acid, hydrogen chloride, methyltrichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, and acetoxysilane.

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