Reactive distillation production process and device of 3-pentenenitrile

Abstract

The invention relates to a reaction rectification production process and device for 3-pentenenitrile, which are used for improving the conversion rate of 2-methyl-3-butenenitrile and the yield of 3-pentenenitrile and realizing efficient production of 3-pentenenitrile. The process comprises the following steps: carrying out chemical reaction on a mixture mainly comprising 2-methyl-3-butenenitrile in a reaction section of a reactive distillation tower under the action of a catalyst, and separating and purifying through a distillation section to obtain high-purity 3-pentenenitrile. According to the invention, 2-methyl-3-butenenitrile is converted into 3-pentenenitrile by adopting a reactive distillation tower process. The method comprises the following steps: firstly, enabling a mixture to enter a tower from the middle lower part of the tower, carrying out chemical reaction in the tower, separating and purifying through a rectifying section and a stripping section, and condensing and refluxing light components at the top of the tower to obtain a target product 3-pentenenitrile. The used device mainly comprises a reactive distillation tower, a condenser and a reflux tank are arranged at the tower top, a reflux pump, a tower top product pump and a raw material feeding pump are further arranged, and a reboiler and a tower bottom product pump are arranged at the tower bottom. According to the present invention, the 2-methyl-3-butenenitrile isomerization reaction is performed by using the reaction rectification process and the device so as to obtain the 3-pentenenitrile product;

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production processes and equipment, and relates to a reaction distillation production process and device for 3-pentenenitrile. Background Art

[0002] Adiponitrile is one of the main raw materials indispensable for the production of new material nylon. It is also the most important industrial use of adiponitrile. Its output is used to produce nylon fiber and resin, and most of the adiponitrile is used by manufacturers. The traditional process routes of adiponitrile mainly include four methods: electrolytic dimerization of acrylonitrile (AN), catalytic amination of adipic acid (ADA), hydrolysis of caprolactam and butadiene (BD). In recent years, with the development of technology, its application field has become increasingly extensive, and the demand for adiponitrile will also increase significantly. At present, the production of adiponitrile is mainly prepared by the direct cyanation of butadiene by INVISTA. As the most advanced adiponitrile production technology, the components are complex in the production process and the boiling points of the main components are close, and its separation and purification are relatively difficult. The reaction principle of the direct hydrocyanation of butadiene is that the reaction of the direct hydrocyanation of butadiene to produce adiponitrile includes three steps: primary cyanation, isomerization and secondary cyanation. The present invention introduces reactive distillation technology into the isomerization stage, and the complexity of the device can be greatly reduced.

[0003] Distillation is the most common unit operation in multi-component separation and is the most widely used in chemical production. 90%-95% of product purification and recovery are achieved by distillation. Sometimes, due to the particularity of the physical properties of the components of the mixture, it is necessary to add various separation agents or use special distillation methods such as reactive distillation, extractive distillation, constant boiling distillation, etc. to achieve the specified separation requirements and improve the separation efficiency.

[0004] As a technical means of process intensification, reactive distillation is an operation process that couples chemical reaction and distillation separation, so that the reaction and separation processes proceed simultaneously. Therefore, chemical reaction and distillation operation both promote and restrict each other. Reactive distillation is to separate reactants and products by distillation, thereby destroying the reaction equilibrium relationship, ensuring that the direction of the reaction is the formation of products, and thus improving the conversion rate, selectivity, and production capacity of the reversible reaction. Moreover, during reactive distillation, the gas-liquid equilibrium relationship may also be destroyed by chemical reactions, which increases the mass transfer rate and reduces the reaction time. The heat released by the exothermic reaction can also be used for the vaporization heat required for the distillation reaction, reducing energy consumption and costs. Compared with traditional chemical production processes, reactive distillation has higher selectivity, which will increase the reaction conversion rate, production capacity, and product purity. It can also speed up the reaction rate, reduce energy consumption and operating costs, and has therefore been widely studied in recent years.

[0005] The conventional process of preparing 3-pentenenitrile utilizes a reactor for chemical reaction. After the isomerization reaction is completed, the reaction liquid first enters a recovery tower to recycle the catalyst, and then enters a distillation tower for separation and purification to obtain high-purity 3-pentenenitrile. The introduction of reactive distillation technology will improve production capacity and product purity. By simulating and optimizing the isomerization process, an advanced 3-pentenenitrile preparation process has been developed. This will improve the yield and product purity of 3-pentenenitrile, reduce the energy consumption of the 3-pentenenitrile production process, and achieve a breakthrough in 3-pentenenitrile production technology. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a reactive distillation production process and device for 3-pentenenitrile. In the process, 2-methyl-3-butenenitrile is reacted under the action of a catalyst to obtain 3-pentenenitrile, and a high-purity 3-pentenenitrile product is extracted at the top of the tower through distillation separation, thereby avoiding the use of a reactor and a catalyst recovery tower, and obtaining high-purity 3-pentenenitrile. The equipment operation difficulty and cost are effectively reduced, thereby reducing production costs, saving resources, having good economic benefits and social benefits, and having broad industrial application and promotion prospects.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A reactive distillation production process and device for 3-pentenenitrile, mainly comprising a raw material feed pump, a reactive distillation tower, a tower top condenser, a reflux tank, a tower bottom reboiler, a reflux pump, a tower top product pump and a tower bottom product pump. The raw material feed pump is connected to the feed port of the reactive distillation tower through a pipeline; the tower top condenser is connected to the distillation tower and a loop is formed therebetween; the distillation tower reboiler is connected to the distillation tower and a loop is formed therebetween; the distillation tower is connected to the tower bottom reboiler.

[0009] The tower top condenser is connected with the distillation tower and a loop is formed therebetween, which means that the tower top condenser is connected with the reflux tank and the reflux pump to form a loop with the distillation tower.

[0010] The use of the above-mentioned device for isomerization reaction distillation includes the following steps:

[0011] The method comprises the steps of isomerizing a mixture mainly containing 2-methyl-3-butenenitrile in a reaction and rectification section to generate 3-pentenenitrile; and the step of separating and purifying 3-pentenenitrile in a stripping section and a rectification section.

[0012] The distillation tower is divided into three sections, the upper section is the distillation section, the middle reaction distillation section, and the lower section is the stripping section. First, a mixture mainly composed of 2-methyl-3-butenenitrile enters the middle and lower part of the distillation tower through a feed pump; the isomerization reaction is carried out in the reaction distillation section of the distillation tower, and 2-methyl-3-butenenitrile is converted into 3-pentenenitrile through an isomerization reaction; then, during the rising process of the mixed gas through the distillation section of the tower, the light components in the vapor phase are continuously refined, and the concentration in the vapor phase is continuously increased. The steam drawn from the top of the tower is condensed through a condenser, and a part of the condensate is returned to the distillation tower from the top of the tower as a reflux liquid, and the remaining distillate is used as the top product of the tower, that is, high-purity 3-pentenenitrile. Then in the stripping section, during the descending process of the liquid phase, its light components are continuously stripped from the liquid phase, so that the heavy components are continuously concentrated in the liquid phase, and then the liquid drawn from the bottom of the tower is partially vaporized through a reboiler, and the steam rises along the tower, and the remaining liquid is extracted as the bottom product of the tower.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The reactive distillation production process and device of 3-pentenenitrile described in the present invention uses a system consisting of a reactive distillation tower, has a high reaction conversion rate, and the product 3-pentenenitrile has high purity and good quality.

[0015] (2) The process of the present invention is simple, the operation is flexible, and the control is easy, and the energy consumption and equipment investment cost are low. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention provides a process flow diagram of a reactive distillation production process and device for 3-pentenenitrile.

[0017] In the figure, 1, 5, 6, and 8 are centrifugal pumps, 2 is a reactive distillation tower, 3 is a condenser, 4 is a reflux tank, and 7 is a reboiler. ① is a catalyst, ② is a feed mixture, ③ is a tower top reflux liquid, ④ is a tower top product, and ⑤ is a tower bottom product. (1) is a distillation section, (2) is a reactive distillation section, and (3) is a stripping section. DETAILED DESCRIPTION

[0018] The reactive distillation production process and device of 3-pentenenitrile described in the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the scope of the present invention is not limited thereto.

[0019] Example 1

[0020] As shown in the figure, a reactive distillation production process and device for 3-pentenenitrile, the reactive distillation tower 2 carries out the isomerization reaction of 2-methyl-3-butenenitrile to obtain high-purity 3-pentenenitrile, and a catalyst (e.g., zinc complex) is added to promote the reaction. The operating pressure of the reactive distillation tower 2 is set to 1atm, the theoretical number of plates is 30, and the reflux ratio is 0.5-10. The mixture mainly composed of 2-methyl-3-butenenitrile enters the reactive distillation tower 2 from the tower plate 19, and the feed flow rate is 320koml / h. Under steady-state operation, the mobile phase of the catalyst enters the tower at the lower position of the tower, and the flow rate is 25kmol / h. The reaction starting tower plate is 2, the ending tower plate is 20, and the reaction residence time is 3-7min. The number of plates in the stripping section is 21-29. The vapor phase at the top of the tower is condensed by the top condenser 3 and enters the reflux tank 4. The reflux liquid of 1740.2 kmol / h is sent to the reaction distillation tower 2 by the pump 5, and 320 kmol / h of 3-pentenenitrile with a purity of 0.999 is produced by the pump 6. The bottom liquid of 71 kmol / h is reboiled by the reboiler 7 and returned to the reaction distillation tower 2, and 25 kmol / h of the catalyst with a purity of 0.98 is produced by the bottom pump 8. Under this process condition, the heat loads of the condenser 3 and the reboiler 7 are -22.7MW and 32.6MW respectively.

[0021] As shown in the figure, the device includes a raw material feed pump, a reaction distillation tower, a tower top condenser, a reflux tank, a tower bottom reboiler, a reflux pump, a tower top product pump and a tower bottom product pump. The raw material feed pump is connected to the feed port of the reaction distillation tower through a pipeline; the tower top condenser is connected to the distillation tower and a loop is formed between the two; the distillation tower reboiler is connected to the distillation tower and a loop is formed between the two; the distillation tower is connected to the tower bottom reboiler.

[0022] Example 2

[0023] As shown in the figure, a reactive distillation production process and device for 3-pentenenitrile, the reactive distillation tower 2 carries out the isomerization reaction of 2-methyl-3-butenenitrile to obtain high-purity 3-pentenenitrile, and a catalyst (e.g., organic acid) is added to promote the reaction. The operating pressure of the reactive distillation tower 2 is set to 1atm, the theoretical plate number is 35, and the reflux ratio is 0.5-10. The mixture mainly composed of 2-methyl-3-butenenitrile enters the reactive distillation tower 2 from the plate 19, and the feed flow rate is 320koml / h. Under steady-state operation, the mobile phase of the catalyst enters the tower at the lower position of the tower, and the flow rate is 25kmol / h. The reaction starting plate is 2, the ending plate is 25, and the reaction residence time is 3-7min. The number of plates in the stripping section is 26-34. The top vapor phase is condensed by the top condenser 3 and enters the reflux tank 4. The reflux liquid of 1423.8 kmol / h is sent to the reaction distillation tower 2 by the pump 5. 320 kmol / h of 3-pentenenitrile with a purity of 0.999 is produced by the pump 6. 65.4 kmol / h of the bottom liquid is reboiled by the reboiler 7 and returned to the reaction distillation tower 2. 25 kmol / h of the catalyst with a purity of 0.97 is produced by the bottom pump 8. Under this process condition, the heat loads of the condenser 3 and the reboiler 7 are -19.2MW and 29.1MW respectively.

[0024] As shown in the figure, the device includes a raw material feed pump, a reaction distillation tower, a tower top condenser, a reflux tank, a tower bottom reboiler, a reflux pump, a tower top product pump and a tower bottom product pump. The raw material feed pump is connected to the feed port of the reaction distillation tower through a pipeline; the tower top condenser is connected to the distillation tower and a loop is formed between the two; the distillation tower reboiler is connected to the distillation tower and a loop is formed between the two; the distillation tower is connected to the tower bottom reboiler.

[0025] Those skilled in the art should understand that the process flow described in the present invention can effectively achieve efficient conversion of raw materials to obtain high-purity products, and is also applicable to situations where the components in other mixtures have different volatilities.

[0026] The above is only used to illustrate the technical solution of the present invention, and is not intended to limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. Any modification, equivalent replacement, improvement, etc. made to the technical solution without departing from the purpose and scope of the technical solution shall be included in the protection scope of the present invention.

Claims

1. A reactive distillation production process and device for 3-pentenenitrile, characterized in that: The mixture is fed into the middle and lower part of the reactive distillation tower. After chemical reaction and distillation separation, part of the tower bottom liquid is reboiled in the reboiler and returned to the bottom of the tower, and the other part is extracted as the bottom product. The light component vapor at the top of the tower is condensed in the condenser and collected in the reflux tank, and part of it is refluxed to the top of the tower, and 3-pentenenitrile is extracted as the top product.

2. A reactive distillation production process and device for 3-pentenenitrile according to claim 1, characterized in that: The top operating pressure of the reactive distillation tower is 0.8-3atm absolute pressure, and the top of the tower is full reflux.

3. The reactive distillation production process and device of 3-pentenenitrile according to claim 1, characterized in that: The feed pressure of the stream mainly composed of 2-methyl-3-butenenitrile is the same as the pressure at the feed tray position of the reactive distillation tower.

4. A reactive distillation production process and device for 3-pentenenitrile according to claim 1, characterized in that: The catalytic isomerization reaction of 2-methyl-3-butenenitrile to prepare 3-pentenenitrile is carried out in the reaction distillation section of the reaction distillation tower. The reaction is an exothermic reaction, and the heat released by the exothermic reaction can be used as the vaporization heat required for the distillation reaction.

5. A reactive distillation production process and device for 3-pentenenitrile according to claim 1, characterized in that: The generated 3-pentenenitrile has a low boiling point and is a light component in the distillation process and is extracted from the top of the reactive distillation tower.

6. A reactive distillation production process and device for 3-pentenenitrile according to claim 1, characterized in that: This process is a continuous operation process, which helps a certain flow rate of raw materials and catalysts to be continuously added into the tower through their respective feed ports, and a certain flow rate of products to be continuously extracted from the discharge ports at the top and bottom of the tower.

7. A reactive distillation production process and device for 3-pentenenitrile according to claim 1, characterized in that: The condenser in this process can be various types of heat exchange equipment for cold and hot materials.

8. A reactive distillation production process and device for 3-pentenenitrile according to claim 1, characterized in that: The reboiler in this process can be various types of heat exchange equipment for cold and hot materials.

9. A reactive distillation production process and device for 3-pentenenitrile according to claim 1, characterized in that: The device used mainly includes a reactive distillation tower, with a condenser and a reflux tank at the top, a reflux pump and a tower top product pump, a raw material feed pump, and a reboiler and a tower bottom product pump at the bottom.

Images