A method and system for continuous salt removal in a triacetone amine rectification process

Abstract

The application provides a method and a system device for continuous salt removal in a triacetone amine rectification process, and the method comprises the following steps: performing solid-liquid separation treatment on a salt-containing organic liquid obtained in the rectification, and the solid-liquid separation treatment is sedimentation treatment; performing cross-flow filtration treatment on a liquid phase obtained in the solid-liquid separation to obtain a permeate and a concentrated liquid, and the permeate is the salt-removed organic liquid. The method and the system device can ensure the continuity and intensiveness of the rectification process, shorten the high-temperature residence time of the material, reduce the energy consumption, and at the same time, maximize the reduction of high-temperature polymerization of the material, and improve the yield.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical technology, and relates to a method and system device for removing salt, in particular to a method and system device for continuously removing salt in a triacetone amine rectification process. BACKGROUND

[0002] Hindered amine light stabilizers belong to the free radical scavengers, and have the characteristics of high efficiency, non-toxicity and colorlessness, and are mainly used in polyolefin films and polypropylene fibers, and are suitable for relatively thick products and relatively thin products. In relatively thick products, low molecular weight hindered amine light stabilizers have better effects, because the low molecular weight light stabilizers have a high diffusion speed and are easy to tend to the surface, thus playing a protective role. However, in relatively thin products, the loss of stabilizers is a dominant factor, and therefore in this case, high molecular weight light stabilizers have better effects. In addition, the hindered amine light stabilizers can also be mixed with other types of stabilizers, and exhibit good synergistic effects.

[0003] Due to the excellent performance of the hindered amine light stabilizers, the research and development of the hindered amine light stabilizers are promoted. The common parent of these light stabilizers is 2,2,6,6-tetramethyl-4-piperidone (also referred to as triacetone amine), and the triacetone amine has poor stability and is not easy to store. The triacetone amine will discolor after being stored for a long time. The reaction liquid of the triacetone amine is relatively complex, and in addition to the triacetone amine, the reaction liquid also contains a large amount of condensates of acetone and ammonia, such as dipropyl ketone amine, forone, dipropyl ketone alcohol, and acetone ning. In addition, some components are unstable to heat, and are easy to decompose and produce light component impurities when heated. Shinya T Manji S and Hidekazu Y 28] disclosed a method for separating and purifying triacetone amine in 2000. The method adopted by them includes two steps. In the first step, a low boiling point fraction containing triacetone amine is distilled out at 50-760 mmHg and 50-100℃, and high boiling point components are removed. In the second step, the obtained triacetone amine fraction is subjected to rectification in a batch rectification column with 5 theoretical plates, and the front fraction and the middle fraction are distilled out at 29-760 mmHg and 60-120℃, and the triacetone amine product is distilled out at 5-30 mmHg.

[0004] In the research on the separation and purification of triacetone amine, Tianjin University first adopted a new type of batch rectification column with a side line discharge to separate the reaction mixture of triacetone amine, and obtained triacetone amine with a purity of greater than 99%. The batch rectification column with a side line discharge reduces the transition fraction of triacetone amine, and improves the yield of the product, and the cycle yield reaches more than 90%. In the rectification process, with the evaporation of water, the salt in the system gradually precipitates, and the literature does not report how to remove the salt generated in the reaction. However, the precipitation of the salt requires a long time, and affects the production cycle, and therefore it is necessary to improve the process of removing the salt to meet the needs of industrial production. SUMMARY

[0005] To solve the above technical problems, the application provides a method and system device for continuous salt removal in a triacetone amine rectification process, which can ensure the continuity and intensiveness of the rectification process, shorten the high-temperature residence time of the material, reduce energy consumption, and maximize the reduction of high-temperature polymerization of the material, thereby improving the yield.

[0006] To achieve the above technical effects, the application adopts the following technical solutions:

[0007] One of the objectives of the application is to provide a method for continuous salt removal in a triacetone amine rectification process, which comprises the following steps:

[0008] The salt-containing organic liquid obtained in the rectification is subjected to solid-liquid separation treatment, and the method of the solid-liquid separation treatment is sedimentation treatment.

[0009] The liquid phase obtained by the solid-liquid separation is subjected to cross-flow filtration treatment to obtain a permeate and a concentrated liquid, and the permeate is the salt-removed organic liquid.

[0010] As mentioned in the background, in the preparation process of triacetone amine, the solvent, i.e., triacetone amine, needs to be removed after obtaining the reaction liquid, and then a large amount of salt generated by the reaction of the acidic catalyst and the basic substance in the system is precipitated as the water is evaporated. The conventional operation is static sedimentation, and the intermittent production seriously affects the production cycle of the product. In the application, the technical solutions of sedimentation solid-liquid separation and cross-flow filtration are combined to continuously and effectively remove the salt, thereby ensuring the continuity and intensiveness of the rectification process. The continuous salt removal instead of intermittent salt removal greatly shortens the high-temperature residence time of the material, reduces energy consumption, maximizes the reduction of high-temperature polymerization of the material, and improves the yield.

[0011] As a preferred technical solution of the application, the concentrated liquid obtained by the cross-flow filtration is returned to the solid-liquid separation device for sedimentation treatment again. The concentrated liquid obtained by the cross-flow filtration contains fine crystals, which can effectively promote the precipitation of supersaturated salt, increase the solid-liquid separation effect, and make the salt removal more thorough.

[0012] As a preferred technical solution of the application, the sedimentation device used in the sedimentation treatment is a sedimentation device with an inclined plate structure. In the application, the sedimentation device with an inclined plate structure is used for solid-liquid separation, which can improve the sedimentation effect, shorten the sedimentation time, and ensure the continuity of the salt removal treatment.

[0013] Preferably, the inclined length of the inclined plate of the sedimentation device with an inclined plate structure is 300-700 mm, such as 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, or 650 mm, but is not limited to the listed values. Other values not listed in this range are also applicable.

[0014] As a preferred technical scheme of the present application, the inclination angle of the inclined plate of the settler with inclined plate structure is 10-45°, such as 10°, 15°, 20°, 25°, 30°, 35°, 40° or 45°, but is not limited to the listed values, and other values not listed in the range are also applicable, preferably 20-45°.

[0015] As a preferred technical scheme of the present application, the pore size of the filter assembly in the cross-flow filtration device used in the cross-flow filtration process is 50-100 nm, such as 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm or 95 nm, but is not limited to the listed values, and other values not listed in the range are also applicable. Too small pore size will result in prolonged filtration time, and too large pore size will affect the subsequent rectification process and the purity of the final product.

[0016] As a preferred technical scheme of the present application, the flow rate of the liquid phase in the cross-flow filtration process is 0.5-5 L / min, such as 1 L / min, 1.5 L / min, 2 L / min, 2.5 L / min, 3 L / min, 3.5 L / min, 4 L / min or 4.5 L / min, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0017] In the present application, the method and system device for continuous salt removal in the rectification process are applicable to all rectification processes involving water, salt and organic substances. They are particularly suitable for the rectification process in the preparation of triacetone amine, which is generally prepared using Lewis acid as catalyst. The catalyst reacts with the base used for terminating the reaction to produce a large amount of salt. During the rectification process of the synthesis liquid, as the low-boiling-point substances and water are distilled out, the salt in the system gradually precipitates. The use of the technical scheme of the present application can significantly shorten the production cycle of triacetone amine and improve the product yield and quality.

[0018] As a preferred technical scheme of the present application, the salt-containing organic liquid is the organic liquid obtained after distilling out the low-boiling-point components and water from the triacetone amine reaction liquid.

[0019] As a preferred technical scheme of the present application, the triacetone amine reaction liquid is prepared by reacting acetone and ammonia raw materials at 45-65℃ under the action of a catalyst. The reaction temperature can be 45℃, 48℃, 50℃, 52℃, 55℃, 58℃, 60℃, 62℃ or 65℃, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0020] Preferably, the molar ratio of the acetone and ammonia raw materials is (3-5):1, such as 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1 or 5:1, etc., but not limited to the listed values, and other unlisted values within the range are also applicable.

[0021] Preferably, the catalyst is a Lewis acid.

[0022] Preferably, the catalyst includes a homogeneous catalyst and a heterogeneous catalyst.

[0023] Preferably, the homogeneous catalyst includes hydrochloric acid, sulfuric acid, nitric acid, an organic carboxylic acid or an organic sulfonic acid, and an ammonium salt or an amine salt of the hydrochloric acid, sulfuric acid, nitric acid, organic carboxylic acid or organic sulfonic acid.

[0024] Preferably, the heterogeneous catalyst includes an acidic ion exchange resin, an acidic molecular sieve, a doped modified body of the ion exchange resin or a doped modified body of the acidic molecular sieve.

[0025] As a preferred technical solution of the present application, a basic substance is added after the reaction is completed.

[0026] Preferably, the basic substance includes an alkali metal hydroxide or an alkaline earth metal hydroxide.

[0027] The second object of the present application is to provide a preparation method of triacetone amine, which comprises subjecting the desalted organic liquid obtained by the above method to rectification to obtain triacetone amine.

[0028] In the present application, the preparation method of triacetone amine can be: adding acetone and a catalyst into a reaction kettle, stirring and heating; introducing ammonia gas into the reaction kettle and further heating, and after the reaction kettle is heated to a reaction temperature, holding the temperature to perform the reaction; cooling the reaction liquid after the reaction is completed, adding a basic substance to obtain a salt-containing organic liquid, subjecting the salt-containing organic liquid to evaporation of low-melting-point components and water, and then using the continuous desalting method provided by the present application to perform desalting treatment, and subjecting the desalted organic liquid to rectification to obtain triacetone amine.

[0029] The third object of the present application is to provide a system device for the continuous desalting method in the above rectification process, which comprises a rectification device, a solid-liquid separation device and a cross-flow filtration device.

[0030] The outlet of the column kettle of the rectification device is connected to the liquid inlet of the solid-liquid separation device, the liquid outlet of the solid-liquid separation device is connected to the liquid inlet of the cross-flow filtration device, and the concentrated liquid outlet of the cross-flow filtration device is connected to the liquid inlet of the solid-liquid separation device.

[0031] Compared with the prior art, the present application has at least the following beneficial effects:

[0032] (1) The present application provides a method and system for continuous salt removal in the rectification process of triacetone amine, which can effectively remove salt continuously, ensure the continuity and intensiveness of the rectification process, and is more suitable for industrial production.

[0033] (2) The present application provides a method and system for continuous salt removal in the rectification process of triacetone amine, which shortens the high-temperature residence time of the material, reduces energy consumption, and maximizes the reduction of high-temperature polymerization of the material, thereby improving the yield.

[0034] (3) The present application provides a method and system for continuous salt removal in the rectification process of triacetone amine, which contains fine crystals in the concentrated solution of the cross-flow filtration, which can effectively promote the precipitation of supersaturated salt, increase the solid-liquid separation effect, and remove salt more thoroughly. DETAILED DESCRIPTION

[0035] To facilitate understanding of the present application, the present application provides the following examples. It should be understood by those skilled in the art that the examples are only to help understand the present application and should not be regarded as a specific limitation on the present application.

[0036] The present application provides a system for continuous salt removal in the rectification process, which is used in the method for continuous salt removal in the rectification process provided in the following examples and comparative examples, and the system comprises a rectification device, a solid-liquid separation device, and a cross-flow filtration device.

[0037] The outlet of the column of the rectification device is connected to the inlet of the solid-liquid separation device, the outlet of the solid-liquid separation device is connected to the inlet of the cross-flow filtration device, and the concentrated solution outlet of the cross-flow filtration device is connected to the inlet of the solid-liquid separation device.

[0038] The solid-liquid separation device is a settler with a inclined plate structure, the inclined angle of the inclined plate of the settler with a inclined plate structure is 10-45°, and the inclined length of the inclined plate of the settler with a inclined plate structure is 300-700 mm.

[0039] The pore size of the filter assembly in the cross-flow filtration device is 50-100 nm.

[0040] The beneficial effects of the present application will be further illustrated below in combination with examples and comparative examples.

[0041] The preparation of the synthetic liquid and the salt-containing organic material liquid according to the present application: 2000 g of acetone and 40 g of nitrate catalyst are added to a reaction kettle, stirred uniformly, heated to 55°C, and then ammonia is passed until the total amount reaches 190 L. After reacting at 60-75°C for 4.5 hours, the temperature is lowered to below 45°C, 24 g of NaOH is added, and the mixture is allowed to stand for 20 minutes to obtain a triacetone amine synthetic liquid.

[0042] The triacetone amine synthesis liquid enters the rectification device to evaporate the low-boiling-point acetone fraction at 80℃ to obtain a tower bottom effluent, and the salt-containing organic liquid is obtained after the tower bottom effluent is treated by rectification and water removal.

[0043] Example 1

[0044] The present embodiment provides a method for continuous salt removal in the rectification process of triacetone amine, which comprises the following steps:

[0045] The salt-containing organic liquid enters the sedimentation device with inclined plate structure for solid-liquid separation; the inclined angle of the inclined plate of the sedimentation device with inclined plate structure is 10°, and the inclined length of the inclined plate of the sedimentation device with inclined plate structure is 500 mm;

[0046] The liquid phase obtained by the solid-liquid separation enters the cross-flow filtration device, the flow rate of the liquid phase in the cross-flow filtration device is 2 L / min, the pore size of the filtration assembly in the cross-flow filtration device is 50 nm, and the permeate obtained by cross-flow filtration enters the subsequent rectification section, and the concentrated liquid returns to the sedimentation device with inclined plate structure.

[0047] Example 2

[0048] The present embodiment provides a method for continuous salt removal in the rectification process of triacetone amine, which comprises the following steps:

[0049] The salt-containing organic liquid enters the sedimentation device with inclined plate structure for solid-liquid separation; the inclined angle of the inclined plate of the sedimentation device with inclined plate structure is 20°, and the inclined length of the inclined plate of the sedimentation device with inclined plate structure is 500 mm;

[0050] The liquid phase obtained by the solid-liquid separation enters the cross-flow filtration device, the flow rate of the liquid phase in the cross-flow filtration device is 2 L / min, the pore size of the filtration assembly in the cross-flow filtration device is 50 nm, and the permeate obtained by cross-flow filtration enters the subsequent rectification section, and the concentrated liquid returns to the sedimentation device with inclined plate structure.

[0051] Example 3

[0052] The present embodiment provides a method for continuous salt removal in the rectification process of triacetone amine, which comprises the following steps:

[0053] The salt-containing organic liquid enters the sedimentation device with inclined plate structure for solid-liquid separation; the inclined angle of the inclined plate of the sedimentation device with inclined plate structure is 30°, and the inclined length of the inclined plate of the sedimentation device with inclined plate structure is 500 mm;

[0054] The liquid phase obtained by the solid-liquid separation enters the cross-flow filtration device, the flow rate of the liquid phase in the cross-flow filtration device is 2 L / min, the pore size of the filtration assembly in the cross-flow filtration device is 50 nm, the permeate obtained by the cross-flow filtration enters a subsequent rectification section, and the concentrated liquid returns to the settler with the inclined plate structure.

[0055] Example 4

[0056] The present embodiment provides a method for continuous salt removal in the rectification process of triacetone amine, which comprises the following steps:

[0057] The salt-containing organic liquid enters the settler with the inclined plate structure for solid-liquid separation; the inclined angle of the inclined plate of the settler with the inclined plate structure is 45°, and the inclined length of the inclined plate of the settler with the inclined plate structure is 500 mm.

[0058] The liquid phase obtained by the solid-liquid separation enters the cross-flow filtration device, the flow rate of the liquid phase in the cross-flow filtration device is 2 L / min, the pore size of the filtration assembly in the cross-flow filtration device is 50 nm, the permeate obtained by the cross-flow filtration enters a subsequent rectification section, and the concentrated liquid returns to the settler with the inclined plate structure.

[0059] Example 5

[0060] In the present embodiment, the inclined length of the settler with the inclined plate structure is 300 mm, and the remaining conditions are the same as those in Example 1.

[0061] Example 6

[0062] In the present embodiment, the inclined length of the settler with the inclined plate structure is 700 mm, and the remaining conditions are the same as those in Example 1.

[0063] Example 7

[0064] In the present embodiment, the flow rate of the liquid phase in the cross-flow filtration device is 0.5 L / min, and the remaining conditions are the same as those in Example 1.

[0065] Example 8

[0066] In the present embodiment, the flow rate of the liquid phase in the cross-flow filtration device is 5 L / min, and the remaining conditions are the same as those in Example 1.

[0067] Comparative Example 1

[0068] In the present comparative example, the other conditions are the same as those in Example 1 except that the settler device without the inclined plate structure is used for solid-liquid separation treatment.

[0069] Comparative Example 2

[0070] The comparative example is the same as example 1 except that cross flow filtration is not performed.

[0071] Comparative example 3

[0072] The comparative example is the same as example 1 except that the method of removing salt by allowing the solution to stand for 24 hours and the salt to precipitate at the bottom is used.

[0073] The organic solution after salt removal obtained in examples 1-8 and comparative examples 1-3 is subjected to distillation to remove the front fraction, and then tripropylamine product is obtained. The yield, purity, efficiency of solid-liquid separation and salt removal time of the tripropylamine are tested, and the results are shown in Table 1.

[0074] Table 1

[0075]

[0076]

[0077] As can be seen from the test results in Table 1, the method of continuous salt removal in the distillation process provided in examples 1-8 can effectively improve the salt removal efficiency and ensure the separation efficiency of salt and organic phase. At the same time, the yield of tripropylamine can reach more than 85%, and the purity can reach more than 98%. Compared with example 1, the salt removal time is significantly improved in comparative example 1 without the use of a settling device with a slope plate structure for solid-liquid separation treatment. In comparative example 2, cross flow filtration is not performed, and the salt separation efficiency is reduced. In comparative example 3, the salt removal time is also significantly improved by using the static method for salt removal.

[0078] The applicant declares that the above examples are used to illustrate the detailed process equipment and process flow of the present application, but the present application is not limited to the above detailed process equipment and process flow, that is, it does not mean that the present application must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the scope of protection and disclosure of the present application.

Claims

1. A method for continuous desalination during the distillation of triacetone amine, characterized in that, The method includes the following steps: The salt-containing organic feed obtained from distillation is subjected to solid-liquid separation treatment, wherein the solid-liquid separation treatment method is sedimentation treatment; The liquid phase obtained from the solid-liquid separation is subjected to cross-flow filtration to obtain permeate and concentrate, wherein the permeate is a desalted organic liquid. The sedimentation device used in the sedimentation treatment is a sedimentation device with an inclined plate structure. The pore size of the filter components in the cross-flow filtration device used in the cross-flow filtration process is 50-100 nm. The salt-containing organic liquid is an organic liquid obtained by distilling off low-boiling-point components and water from the triacetone amine reaction liquid. The triacetone amine reaction liquid is prepared by reacting acetone and ammonia as raw materials at 45-65°C under the action of a catalyst. The catalyst is a nitrate catalyst. After the reaction is completed, an alkaline substance is added for treatment. The alkaline substance is NaOH.

2. The method according to claim 1, characterized in that, The inclined length of the inclined plate of the settling device with the inclined plate structure is 300-700 mm.

3. The method according to claim 2, characterized in that, The inclined plate of the settling device with the inclined plate structure has an inclination angle of 10 to 45°.

4. The method according to claim 3, characterized in that, The inclined plate of the settling device with the inclined plate structure has an inclination angle of 20 to 45°.

5. The method according to claim 1, characterized in that, The flow rate of the liquid phase in the cross-flow filtration process is 0.5–5 L / min.

6. The method according to claim 1, characterized in that, The concentrate is returned to the solid-liquid separation process, i.e., recycled for sedimentation.

7. The method according to claim 1, characterized in that, The molar ratio of acetone to ammonia is (3-5):1.

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