A process for separating a mixture of methyl methacrylate-methanol-water by pressure swing distillation combined with extractive distillation

Abstract

This invention relates to a method for separating a methyl methacrylate-methanol-water mixture using pressure swing distillation combined with extractive distillation. The apparatus for implementing this method mainly comprises the following parts: distillation column 1 (C1), distillation column 2 (C2), distillation column 3 (C3), condenser 1 (D1), condenser 2 (D2), condenser 3 (D3), reboiler 1 (B1), reboiler 2 (B2), reboiler 3 (B3), cooler (E1), mixer (FS), centrifugal pump 1 (P1), centrifugal pump 2 (P2), and centrifugal pump 3 (P3); wherein the bottom stream of distillation column 1 (C1) enters the distillation column... Distillation column 2 (C2) receives high-purity methanol from the top stream of distillation column 1 (C1). The bottom product of distillation column 1 (C1) passes through P1 and enters distillation column 2 (C2). High-purity methyl methacrylate is then received from the top stream of distillation column 2 (C2), and the bottom product of distillation column 2 (C2) passes through P2 and enters distillation column 3 (C3). High-purity water is then received from the top stream of distillation column 3 (C3), completing the separation of the three components. High-purity extractant is obtained from the bottom of distillation column 3 (C3) and passes through P3 into cooler (E1). After cooling, extractant is added and then refluxed back to distillation column 2 (C2). The extractant used is non-volatile, has good chemical and thermal stability, and is environmentally friendly and pollution-free.

Description

[Technical Field]

[0001] This invention belongs to the field of chemical separation and purification, specifically relating to a method for separating a methyl methacrylate-methanol-water mixture by pressure swing distillation combined with extractive distillation. More specifically, it relates to a method for separating a methyl methacrylate-methanol-water mixture by extractive distillation using a high-pressure tower as a pre-separation device and glycerol as an extractant. [Background Technology]

[0002] Methyl methacrylate, methanol, and water are common chemical substances in daily life. Methyl methacrylate is widely used in plexiglass, coatings, and emulsion resins. It is often used as a monomer in the production of polymers, mainly in the production of polymethyl methacrylate, acrylate copolymers as impact aids in polyvinyl chloride processing, methyl methacrylate-butadiene-styrene terpolymers, and as a second monomer for acrylonitrile fibers.

[0003] The main production methods for methyl methacrylate are the ethylene route and the isobutylene oxidation route. In both of these methods, an excess of methanol is involved in the reaction process, and a large amount of water is produced as a byproduct after the reaction. Therefore, a large amount of methyl methacrylate-water-methanol mixture exists after the reaction. Under normal pressure, methyl methacrylate can form azeotropes with water and methanol, which increases the difficulty of separation.

[0004] This invention utilizes a thermally coupled pressure swing distillation and extractive distillation apparatus to achieve high-purity separation and recovery of a methyl methacrylate-methanol-water mixture. Glycerol is used as the extractant, and separation is achieved by leveraging the high pressure to alter the relative volatility of the methyl methacrylate-methanol mixture and the significant influence of the extractant on the relative volatility of methyl methacrylate-water. The purity of the separated methyl methacrylate, methanol, and water all exceeds 99.9%, and the extractant can be recovered and reused with high purity, significantly reducing separation costs. This method is energy-efficient, requires minimal equipment, and features a simple process. [Summary of the Invention]

[0005] [Technical problem to be solved]

[0006] The object of this invention is to provide a method for separating a methyl methacrylate-methanol-water mixture using the aforementioned apparatus via pressure swing distillation combined with extractive distillation.

[0007] Another object of the present invention is to provide an apparatus for separating a methyl methacrylate-methanol-water mixture by pressure swing distillation combined with extractive distillation.

[0008] Another object of the present invention is to provide the use of glycerol as an extractant in the extractive distillation separation of methyl methacrylate-methanol-water mixtures.

[0009] [Technical Solution]

[0010] The present invention is achieved through the following technical solution.

[0011] A method for separating a methyl methacrylate-methanol-water mixture using pressure swing distillation combined with extractive distillation, characterized in that the apparatus for implementing this method mainly comprises the following parts: distillation column 1 (C1), distillation column 2 (C2), distillation column 3 (C3), condenser 1 (D1), condenser 2 (D2), condenser 3 (D3), reboiler 1 (B1), reboiler 2 (B2), reboiler 3 (B3), cooler (E1), mixer (FS), centrifugal pump 1 (P1), centrifugal pump 2 (P2), and centrifugal pump 3 (P3); wherein the bottom stream of distillation column 1 (C1) enters the distillation column. In distillation column 2 (C2), high-purity methanol is collected from the top stream of distillation column 1 (C1); the bottom product of distillation column 1 (C1) passes through P1 and enters distillation column 2 (C2); high-purity methyl methacrylate is collected from the top stream of distillation column 2 (C2); the bottom product of distillation column 2 (C2) passes through P2 and enters distillation column 3 (C3); high-purity water is collected from the top stream of distillation column 3 (C3), completing the separation of the three components; high-purity extractant is obtained at the bottom of distillation column 3 (C3) and passes through P3 into cooler (E1), after cooling, extractant is added and then refluxed to distillation column 2 (C2).

[0012] A method for separating a methyl methacrylate-methanol-water mixture using the above-described apparatus comprises the following steps:

[0013] (1) The methyl methacrylate-methanol-water mixture enters from the middle of distillation column 1 (C1). The distillation column 1 (C1) is operated at a pressure of 12 atmospheres. After effective vapor-liquid phase contact separation, high-purity product methanol is collected from the top of distillation column 1 (C1). The methyl methacrylate-water mixture in the bottom of the column enters distillation column 2 (C2) through centrifugal pump 1 (P1).

[0014] (2) The methyl methacrylate-water mixture enters from the middle of the distillation column 2 (C2), and the extractant enters from the top of the distillation column 2 (C2). High-purity methyl methacrylate is obtained at the top of the distillation column 2 (C2). The water-extractant mixture collected from the bottom of the column enters the distillation column 3 (C3) through the centrifugal pump 2 (P3) from the top of the distillation column 2 (C2).

[0015] (3) The water-extractant mixture enters the distillation column 3 (C3). High-purity water is collected from the top of the distillation column 3 (C3), and high-purity extractant is recovered from the bottom of the distillation column 3 (C3) to complete the separation.

[0016] (4) The bottom stream of distillation column 3 (C3) is taken out with high purity extractant and enters cooler (E1) through P3. After cooling, extractant is added and then refluxed to distillation column 2 (C2).

[0017] According to claim 1, the method is characterized in that: the operating pressure of distillation column 1 (C1) is 12 atmospheres, the operating pressure of distillation column 2 (C2) and distillation column (C3) is atmospheric pressure, the number of trays of distillation column 1 (T1) is 60-80, and the temperature is 145-171°C; the number of trays of distillation column 2 (T2) is 50-70, and the temperature is 100-233°C; the number of trays of distillation column 3 (T3) is 30-50, and the temperature is 99-297°C.

[0018] According to another preferred embodiment of the present invention, the extractant is glycerol.

[0019] According to another preferred embodiment of the present invention, the feed flow rate mass ratio of the extractant to the methyl methacrylate-water mixture is 0.3 to 0.5.

[0020] According to another preferred embodiment of the present invention, the methyl methacrylate-methanol-water mixture contains 17.71% methyl methacrylate, 69.79% methanol, and 12.5% ​​water.

[0021] According to another preferred embodiment of the present invention, the methanol recovered from the top of distillation column 1 (C1) has a purity higher than 99.9% and a yield higher than 99.9%; the methyl methacrylate recovered from the top of distillation column 2 (C2) has a purity higher than 99.9% and a yield higher than 99.9%; and the water recovered from the top of distillation column 3 (C3) has a purity higher than 99.9% and a yield higher than 99.9%.

[0022] [Beneficial Effects]

[0023] Compared with the prior art, the present invention has the following main advantages:

[0024] (1) The method was used to separate the methyl methacrylate-methanol-water mixture to obtain high-purity methyl methacrylate, methanol and water, which solved the problem of the difficulty in separating the methyl methacrylate-methanol-water mixture.

[0025] (2) This method has the advantages of simple process, low investment in equipment, high purity of methyl methacrylate, methanol and water after separation, and the extractant used is easy to recover, has good chemical and thermal stability, and is green and pollution-free.

[0026] (3) The extractant used in this method is almost non-volatile, which reduces the loss of extractant and avoids secondary pollution of methyl methacrylate, methanol and water. In addition, the extractant is easy to recycle and reuse, which reduces the separation cost. [Attached Image Description]

[0027] Figure 1 This is a process flow diagram of the extraction and distillation separation of a mixture of methyl methacrylate, methanol, and water according to the present invention.

[0028] In the diagram, C1-distillation column, C2-distillation column, C3-distillation column, D1-condenser, D2-condenser, D3-condenser, B1-reboiler, B2-reboiler, B3-reboiler, P1-centrifugal pump, P2-centrifugal pump, P3-centrifugal pump, E1-cooler; FS-mixer.

Detailed Implementation Methods

[0029] Example:

[0030] The feed flow rate is 100 kmol / h, containing 17.71% methyl methacrylate, 69.79% methanol, and 12.5% ​​water (mole fraction). Distillation column 1 (C1) has 70 theoretical plates and operates at 12 atmospheres. The methyl methacrylate-methanol-water mixture enters from the middle of distillation column 1 (C1); 69.79 kmol / h of 99.9% methanol is obtained at the top of distillation column 1 (C1). The methyl methacrylate-water mixture enters from the middle of distillation column 2 (C2) at a flow rate of 30.21 kmol / h. Distillation column 2 (C2) has 61 theoretical plates, and glycerol is used as the extractant. The glycerol extractant enters from the top of distillation column 2 (C1) at a flow rate of 101.3 kmol / h, obtaining 17.71 kmol / h of 99.9% methyl methacrylate at the top. The water-extractant mixture enters from the middle of distillation column 3 (C3), which has 31 theoretical plates, to separate the water and extractant. The distillation column operates at atmospheric pressure. After separation, the purity of methyl tert-butyl ether is 99.9%, and the yield is 99.9%; the purity of methanol is 99.9%, and the yield is 99.9%; and the purity of water is 99.9%, and the yield is 99.9%.

Claims

1. A method for separating a methyl methacrylate-methanol-water mixture by pressure swing distillation combined with extractive distillation, characterized in that... The apparatus for implementing this method includes the following parts: Distillation column 1 (C1), distillation column 2 (C2), distillation column 3 (C3), condenser 1 (D1), condenser 2 (D2), condenser 3 (D3), reboiler 1 (B1), reboiler 2 (B2), reboiler 3 (B3), cooler (E1), mixer (FS), centrifugal pump 1 (P1), centrifugal pump 2 (P2), centrifugal pump 3 (P3); the bottom stream of distillation column 1 (C1) enters distillation column 2 (C2), and high-purity methanol is collected from the top stream of distillation column 1 (C1). The bottom product of distillation column 1 (C1) passes through P1 and enters distillation column 2 (C2). High-purity methyl methacrylate is collected from the top stream of distillation column 2 (C2). The bottom product of distillation column 2 (C2) passes through P2 and enters distillation column 3 (C3). High-purity water is collected from the top stream of distillation column 3 (C3), completing the separation of the three components. High-purity extractant is obtained at the bottom of distillation column 3 (C3) and passes through P3 into cooler (E1). After cooling, extractant is added and then refluxed to distillation column 2 (C2). A method for separating a methyl methacrylate-methanol-water mixture using the above-described apparatus comprises the following steps: (1) The methyl methacrylate-methanol-water mixture enters from the middle of distillation column 1 (C1). The operating pressure of distillation column 1 (C1) is 12 atmospheres. After effective vapor-liquid phase contact separation, high-purity product methanol is collected from the top of distillation column 1 (C1). The methyl methacrylate-water mixture in the bottom of the column enters distillation column 2 (C2) through centrifugal pump 1 (P1). (2) The methyl methacrylate-water mixture enters from the middle of the distillation column 2 (C2), and the extractant is glycerol, which enters from the top of the distillation column 2 (C2). The operating pressure of the distillation column 2 (C2) is atmospheric pressure. High-purity methyl methacrylate is obtained at the top of the distillation column 2 (C2). The water-extractant mixture collected from the bottom of the column enters the distillation column 3 (C3) through the centrifugal pump 2 (P2) from the top of the distillation column 2 (C2). (3) The water-extractant mixture enters the distillation column 3 (C3). The operating pressure of the distillation column 3 (C3) is atmospheric pressure. High-purity water is collected from the top of the distillation column 3 (C3), and high-purity extractant is recovered from the bottom of the distillation column 3 (C3) to complete the separation. (4) The bottom stream of distillation column 3 (C3) is used to collect high-purity extractant and enters cooler (E1) through P3. After cooling, extractant is added and then refluxed to distillation column 2 (C2).

2. The method according to claim 1 is characterized in that: the number of trays in distillation column 1 (C1) is 60-80, and the temperature is 145-171°C; the number of trays in distillation column 2 (C2) is 50-70, and the temperature is 100-233°C; the number of trays in distillation column 3 (C3) is 30-50, and the temperature is 99-297°C.

3. Another feature of the method according to claim 1 is that the feed flow rate mass ratio of the extractant to the methyl methacrylate-water mixture is 0.3~0.

5.

4. Another feature of the method according to claim 1 is that: in the methyl methacrylate-methanol-water mixture, the molar fraction of methyl methacrylate is 17.71%, the molar fraction of methanol is 69.79%, and the molar fraction of water is 12.5%.

5. Another feature of the method according to claim 1 is that: the methanol recovered from the top of distillation column 1 (C1) has a purity higher than 99.9% and a yield higher than 99.9%; the methyl methacrylate recovered from the top of distillation column 2 (C2) has a purity higher than 99.9% and a yield higher than 99.9%; and the water recovered from the top of distillation column 3 (C3) has a purity higher than 99.9% and a yield higher than 99.9%.

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