CN219050351U - MMA separation system for byproduct high-purity methylal - Google Patents

Abstract

The utility model relates to an MMA separation system for byproduct high-purity methylal, which comprises methylal reaction units connected in sequence, wherein part of raw materials in an initial aldol condensation product are utilized to react to generate methylal and are separated; a methanol recovery unit for separating methanol from the aldol condensation product after methylal removal; the methyl propionate recovery unit is used for separating methyl propionate in the material components from which the methanol is removed; and an MMA recovery unit for separating MMA from the remaining material component. The utility model solves the problem of recycling byproducts existing in separating MMA from aldol condensation products, further improves the yield of MMA, further reduces the treatment cost and improves the economic benefit.

Description

MMA separation system for byproduct high-purity methylal

Technical Field

The utility model relates to the technical field of chemical separation, in particular to an MMA (methyl methacrylate) separation system for byproduct high-purity methylal.

Background

Methyl Methacrylate (MMA) is an important chemical raw material as an organic compound, and can be used for producing organic glass, plastic modifiers, surface coatings and other industries. Currently, main methods for producing MMA include an acetone cyanohydrin method, a tert-butanol/isobutylene direct oxidation method, an ethylene carbonylation method, a methyl propionate aldol condensation method, and the like, wherein the methyl propionate aldol condensation method is a research hot spot in recent years, and a subsequent refining process of a crude MMA product (condensation reaction product) is also a research hot spot.

Since the MMA crude product contains unreacted formaldehyde, the recycling problem is not considered in the refining process, so that the economical efficiency is not ideal, and the potential environmental protection problem exists. In addition, methyl propionate and methanol are separated in the form of azeotrope in the conventional refining process, and the separation form is difficult to realize the recovery and the reutilization of the methanol, which means that methanol is required to be continuously added as a solvent of a condensation reactant, methanol accumulation can occur in actual operation, and engineering is difficult to implement.

Disclosure of Invention

The utility model aims to solve the problems and provide an MMA separation system for preparing a byproduct of high-purity methylal, so as to solve the problem of recycling byproducts existing in separating MMA from aldol condensation products, further improve the yield of MMA, further reduce the treatment cost and improve the economic benefit.

The aim of the utility model is achieved by the following technical scheme:

an MMA separation system for byproduct high-purity methylal, comprising the following steps of:

a methylal reaction unit for generating methylal by using the raw materials in the initial aldol condensation product and separating the methylal;

a methanol recovery unit for separating methanol from the aldol condensation product after methylal removal;

the methyl propionate recovery unit is used for separating methyl propionate in the material components from which the methanol is removed;

and an MMA recovery unit for separating MMA from the remaining material component.

Further, the methylal reaction unit comprises a methylal tower, the top of the methylal tower is connected with a high-pressure tower, the top material of the methylal tower enters the high-pressure tower, methanol is extracted from the top of the high-pressure tower in the form of an azeotrope and returns to the methylal tower, the concentration of methanol at the top of the methylal tower is about 10-20%, and high-concentration (more than or equal to 99.9%) methylal is extracted from the bottom of the high-pressure tower; and the tower kettle produced material of the methylal tower enters a methanol recovery unit.

Further, the high-pressure tower is operated under 0.3-0.6MPaG, a heat exchanger and a condenser are arranged at the tower bottom of the high-pressure tower, and high-concentration methylal extracted from the tower bottom of the high-pressure tower is extracted after passing through the heat exchanger and the condenser;

the material at the top of the methylal tower firstly exchanges heat through the heat exchanger before entering the high-pressure tower;

the tower kettle of the methylal tower is provided with a methylal tower reboiler, and the tower top steam of the high-pressure tower enters the upper part of the methylal tower after heat exchange of the methylal tower reboiler, so that the consumption of steam and cooling water is greatly reduced.

Further, the high-pressure tower is connected with an atmospheric tower, tower top materials of the high-pressure tower enter the atmospheric tower, the tower top materials of the atmospheric tower reflux to the high-pressure tower, and methanol is extracted from a tower kettle of the atmospheric tower;

and a reboiler is arranged at the tower bottom of the atmospheric tower, and tower top materials of the high-pressure tower enter the atmospheric tower through the reboiler.

Further, the methanol recovery unit comprises a methanol recovery tower, the methanol recovery tower is operated at normal pressure, most of methanol is extracted from the tower top in an azeotrope form, condensation products after most of methanol is removed are extracted from the tower bottom, and the condensation products are sent to the methyl propionate recovery unit.

Further, the methyl propionate recovery unit comprises a dehydration tower and a methyl propionate recovery tower,

the dehydration tower is operated under negative pressure, the steam at the top of the dehydration tower is condensed to 35-45 ℃ by a condenser and then sent to a reflux tank to realize liquid-liquid phase separation, wherein an organic phase is used as a reflux stream to be returned to the top of the dehydration tower, the reflux tank extracts decantation water, and the discharge material at the bottom of the dehydration tower is sent to the methyl propionate recovery tower;

the methyl propionate recovery tower is operated under negative pressure, methyl propionate is extracted from the tower top, and the discharged material of the tower bottom is sent to the MMA recovery unit.

Further, the decanted water extracted from the reflux tank is sent to a stripping tower, the stripping tower operates at normal pressure, light components including methyl propionate and methanol are extracted from the tower top and returned to the methylal tower, and the wastewater extracted from the tower bottom of the stripping tower is cooled and sent out of the boundary region.

Further, the MMA recovery unit comprises an MMA crude tower, an MMA refining tower and a propionic acid recovery tower;

the tower top of the MMA crude tower is connected with the MMA refining tower, the tower bottom is connected with the propionic acid recovery tower, so that a tower top extract of the MMA crude tower is sent to the MMA refining tower, a recombinant component containing propionic acid and acrylic acid is sent to the propionic acid recovery tower, a tower bottom of the MMA refining tower is used for extracting high-concentration MMA, and a light component containing methyl isobutyrate is sent to an impurity buffer tank;

or the tower bottom of the MMA crude tower is connected with the MMA refining tower, so that the recombination produced by the MMA crude tower bottom is distributed to the MMA refining tower, the tower bottom of the MMA refining tower is connected with the propionic acid recovery tower, so that the high-concentration MMA is produced by the MMA refining tower, and the recombination produced by the tower bottom comprises propionic acid and acrylic acid is distributed to the propionic acid recovery tower;

the MMA crude tower, the MMA refining tower and the propionic acid recovery tower are all operated by negative pressure.

Further, the mixture of propionic acid and methacrylic acid extracted from the top of the propionic acid recovery tower is sent to an esterification reactor, and high-boiling substances extracted from the tower bottom are cooled and sent out of a boundary region;

and (3) carrying out esterification reaction on the mixture of propionic acid and methacrylic acid from the propionic acid recovery tower and methanol in the esterification reactor, and returning the product to the methylal tower.

Further, the tower tops of the methylal tower, the dehydration tower, the methyl propionate recovery tower, the MMA crude tower and the MMA refining tower are provided with two-stage condensers, the two-stage condensers are connected with a reflux tank, and gas products at the tower tops are sent out of the boundary zone after two-stage condensation.

Compared with the prior art, the utility model has the following beneficial effects:

1. the utility model sets a methylal reaction unit, separates and obtains the high-purity methylal product with the concentration of 99.9% from the condensation product, and realizes the recycling of formaldehyde. And the tail gas aftercooler is arranged behind the methylal tower top condenser, so that methylal loss can be reduced.

2. The utility model sets up the esterification reactor, has solved the hydrolysis by-product propionic acid and methacrylic acid recycle problem that the aldol condensation product separates MMA and exists, and raise MMA yield of the product.

3. According to the utility model, through the thermal coupling design of the high-pressure tower and the methylal tower, the consumption of heating steam and condensed water is obviously reduced, the treatment cost is effectively reduced, and the economic benefit is improved.

Drawings

FIG. 1 is a schematic diagram showing the structure of an MMA separating system in example 1 of the utility model;

FIG. 2 is a schematic diagram showing the structure of an MMA separating system in example 2 of the utility model;

FIG. 3 is a schematic diagram showing the structure of an MMA separating system in example 3 of the utility model.

In the figure: methylal column 1; a methanol recovery column 2; a dehydration tower 3; a methyl propionate recovery column 4; MMA crude column 5; an MMA refining tower 6; a high pressure column 7; a stripping column 8; an esterification reactor 9; a propionic acid recovery column 10; a reflux drum 23; a heat exchanger 24; a reboiler 25;11 to 22 and 26 are condensers.

Detailed Description

The utility model will now be described in detail with reference to the drawings and specific examples. In the technical scheme, the characteristics of preparation means, materials, structures or composition ratios and the like which are not explicitly described are regarded as common technical characteristics disclosed in the prior art.

A system for separating MMA and by-producing high-purity methylal from aldol condensation products comprises a methylal reaction unit, a methanol recovery unit, a methyl propionate recovery unit and an MMA recovery unit, wherein the methylal reaction unit comprises a methylal tower, the methanol recovery unit comprises a methanol recovery tower, the methyl propionate recovery unit comprises a dehydration tower and a methyl propionate recovery tower, and the MMA recovery unit comprises an MMA crude tower, an MMA refining tower and a propionic acid recovery tower. As shown in fig. 1, the system mainly includes: methylal column 1; a methanol recovery column 2; a dehydration tower 3; a methyl propionate recovery column 4; MMA crude column 5; an MMA refining tower 6; a high pressure column 7; a stripping column 8; an esterification reactor 9; propionic acid recovery column 10, etc.

The condensation product feed (mainly comprising MMA, methyl propionate, methanol, methylal, methyl isobutyrate, water, etc.) first enters the methylal column 1, the vapor phase product after two-stage condensation at the top of the column via condensers 11, 12 is sent out of the boundary zone, two-stage condensers 11 and 12 are arranged to reduce methylal loss, and the methylal azeotrope is sent into the higher pressure column 7.

The methylal azeotrope from the top of methylal column 1 enters the middle part of high-pressure column 7, and the function of high-pressure column 7 is mainly to remove methanol from methylal azeotrope. The high-pressure tower is operated under 0.3-0.6MPaG, methanol is extracted from the tower top and returned to the upper part of the methylal tower 1 in the form of azeotrope, and the concentration of the methanol at the tower top is about 10-20%. Methylal with the concentration of 99.9 percent is extracted from the high-pressure tower kettle, heat is firstly exchanged and recovered in the heat exchanger 24, and then cooled by the condenser 22 and is sent out as a product to a boundary region.

The high-pressure tower 7 and the methylal tower 1 adopt a heat integration design, and the steam at the top of the high-pressure tower 7 is condensed by the methylal tower reboiler 25 and then enters the upper part of the methylal tower 1, so that the consumption of steam and cooling water is greatly reduced.

The tower kettle product after methylal is removed from the methylal tower 1 enters a methanol recovery tower 2, and the methanol recovery tower 2 is operated at normal pressure. Most of the methanol is removed through the methanol recovery tower 2, and the most of the methanol is recovered from the top of the tower in the form of an azeotrope and then condensed through a condenser 13 to be sent to an upstream reaction section. The condensation product after removing most of the methanol is extracted from the tower bottom of the methanol recovery tower 2, the methanol content is reduced to below 1.0 percent, and then the condensation product is sent to a dehydration tower 3 for further treatment.

The dehydration column 3 mainly has the function of removing the dissolved water in the light phase. The dehydration column 3 is operated with a negative pressure to lower the column temperature and reduce the polymerization of MMA. The vapor at the top of the dehydration tower 3 is condensed to 35-45 ℃ by a condenser 14 and then sent to a reflux tank to realize liquid-liquid phase separation, wherein the organic phase is used as a reflux stream to be returned to the top of the dehydration tower. The decanted water withdrawn from reflux drum 23 is sent to stripper 8 for further processing. An aftercooler 15 is arranged before the non-condensable gas at the top of the dehydration tower is sent out of the boundary region so as to reduce the loss of effective components. The discharged material of the dehydration tower 3 is pumped to a methyl propionate recovery tower 4 for further treatment, and the water content of the tower kettle is required to be controlled to be below 0.1-1 percent so as to avoid the aggravated hydrolysis side reaction brought into an aldol condensation section.

The stripping tower 8 operates at normal pressure, and light components including methyl propionate and methanol are extracted from the top of the stripping tower and returned to the inlet of the methylal tower 1. And cooling the qualified wastewater extracted from the tower bottom of the stripping tower 8 and delivering the cooled wastewater out of the boundary region.

The methyl propionate recovery column 4 mainly has the function of recovering methyl propionate and returning the methyl propionate to the upstream aldol condensation section for continuous reaction so as to improve the yield. The methyl propionate recovery tower 4 adopts negative pressure operation, and methyl propionate is extracted from the tower top. An aftercooler 16 is arranged before the noncondensable gas at the top of the methyl propionate recovery tower 4 is sent out of the boundary region so as to reduce the loss of methyl propionate. The discharge of the tower bottom requires that the methyl propionate content is reduced to below 0.1 percent, and then the methyl propionate content is sent to an MMA crude tower 5 for further refining.

The top of the MMA crude tower 5 is connected with the MMA refining tower 6, so that the tower top extract of the MMA crude tower 5 is sent to the MMA refining tower 6, and the tower bottom of the MMA crude tower 5 is connected with the propionic acid recovery tower 10, so that the heavy component material extracted from the tower bottom of the MMA crude tower 5 enters the propionic acid recovery tower 10; the tower top extract of the MMA refining tower 6 is sent to an impurity buffer tank, and high-concentration MMA is extracted from the tower bottom; the mixture of the propionic acid and the methacrylic acid extracted from the top of the propionic acid recovery tower 10 is sent to the esterification reactor 9, and the high-boiling-point substances extracted from the tower bottom are sent out of the boundary area after being cooled; the esterification reaction of the propionic acid/methacrylic acid mixture from the propionic acid recovery column 10 with methanol in the esterification reactor 9 is carried out, and the product is returned to the methylal column 1.

The MMA crude column 5 mainly has a function of removing heavy components including propionic acid, methacrylic acid and high boiling substances. The MMA crude tower 5 is operated under negative pressure, MMA with heavy components removed is extracted from the tower top, the propionic acid content is required to be lower than 0.01%, and then the MMA crude tower is sent to the MMA refining tower 6. An after cooler 17 is provided before the top noncondensable gas of the MMA crude column 5 is sent out of the boundary region to reduce loss of MMA. The recombinant fraction withdrawn from the MMA crude column bottoms contains a large amount of propionic acid and acrylic acid, and is sent to the propionic acid recovery column 10 for further treatment.

The heavy fraction from the bottom of MMA crude column 5 is fed to propionic acid recovery column 10, and the propionic acid recovery column 10 mainly has the function of removing high boiling impurities and recovering propionic acid and methacrylic acid. The propionic acid recovery tower is operated under negative pressure, the mixture of propionic acid and methacrylic acid is extracted from the tower top and sent to the esterification reactor 9, and an aftercooler 19 is arranged before the noncondensable gas at the tower top is sent out of the boundary zone so as to reduce propionic acid loss. The high-boiling-point substances in the bottom of the propionic acid recovery tower are cooled by a water cooler 20 and then sent out of the boundary region.

The propionic acid/methacrylic acid mixture from the top of the propionic acid recovery column 10 was mixed with methanol at an acid-to-alcohol molar ratio of 1.2:1 and fed to the esterification reactor 9. The esterification reactor 9 may be of isothermal or adiabatic design with a resin catalyst incorporated to accelerate the propionic acid/methylacrylate reaction, with a methanol conversion of about 85-95%. The esterification reaction product returns to the inlet of the methylal tower 1 for separation.

MMA-refining column 6 is mainly used for removing methyl isobutyrate close to the boiling point of MMA product. The MMA refining tower 6 adopts negative pressure operation, and the impurity methyl isobutyrate is extracted from the top of the tower and then sent to an impurity buffer tank. An after cooler 18 is provided before the noncondensable gas at the top of the MMA refining tower is sent out of the boundary region to reduce loss of MMA. The product with MMA concentration reaching 99.9% is extracted from the tower kettle, cooled by a water cooler 21 and sent to an intermediate tank area.

In addition, the tops of the methylal tower 1, the dehydrating tower 3, the methyl propionate recovery tower 4, the MMA crude tower 5 and the MMA refining tower 6 are provided with two-stage condensers, the two-stage condensers are connected with a reflux tank, and gas products at the top of the tower are sent out of the boundary zone after two-stage condensation so as to reduce product loss.

Considering that most of the equipment of the device operates under negative pressure, the tower internal parts are all structured packing to reduce the pressure difference and reduce the occurrence of polymerization side reaction. And aftercoolers are arranged before the tower top gas phase enters the vacuum pump so as to reduce loss of effective components and reduce power consumption of the vacuum pump.

The following is a specific application:

using the system shown in FIG. 1, for a 10 ten thousand ton MMA plant, a condensation product of about 129ton/h MMA mass concentration of 5to 10% was fed into the plant, and treated to obtain a product MMA of about 12.8ton/h having a purity of 99.9%. While 99.9% of methylal by-product was obtained at about 6.0ton/h from the bottom of the high-pressure column 7, methanol azeotrope at about 47ton/h was obtained at the top of the methanol recovery column 2, methyl propionate at about 58.4ton/h was obtained at the top of the methyl propionate recovery column 4, light fraction at about 0.3ton/h was obtained at the top of the MMA refining column 6, high-boiling substance at about 0.4ton/h was obtained at the bottom of the propionic acid recovery column 10, waste water was discharged at 4.1ton/h, system steam consumption at 125ton/h, and the circulating cooling water consumption at 850ton/h.

Compared with the conventional system, the system obviously reduces the consumption of heating steam by 12%, improves the MMA yield of the product by about 2%, reduces the methylal loss by 2.4%, reduces the consumption of heating steam by 0.2% and reduces cooling water by about 0.1%.

Example 2

In this embodiment, as a preferred scheme, as shown in fig. 2, unlike embodiment 1, in which the high-pressure tower 7 is connected to the atmospheric tower 27, the overhead material of the high-pressure tower 7 enters the atmospheric tower 27, the overhead material of the atmospheric tower 27 flows back to the high-pressure tower 7, and methanol is extracted from the bottom of the atmospheric tower 27; the tower bottom of the atmospheric tower 27 is provided with a reboiler, and the tower top material of the high-pressure tower 7 enters the atmospheric tower 27 through the reboiler. The coupling of the higher pressure column and the atmospheric column allows for the separation of higher concentrations of methanol from the condensation product.

Example 3

The difference from example 1 is that the connecting structure of MMA crude column 5 and MMA refining column 6 is that in this example, the heavy fraction in the column bottom of MMA crude column 5 is fed into MMA refining column 6, the heavy fraction from the column bottom of MMA refining column 6 is fed into propionic acid recovery column 10, and high purity MMA is extracted from the column top of MMA refining column 6. As shown in fig. 3.

Specifically, the tower bottom of the MMA crude tower 5 is connected with the MMA refining tower 6, so that the heavy fraction in the tower bottom of the MMA crude tower 5 enters the MMA refining tower 6; the column bottom of the MMA refining column 6 is connected to the propionic acid recovery column 10 so that a heavy fraction (containing propionic acid and acrylic acid) from the column bottom of the MMA refining column 6 is fed to the propionic acid recovery column 10, and high-purity MMA is produced from the column top of the MMA refining column 6.

The advantages of this solution are: MMA having higher purity can be obtained as compared with example 1, because the influence of heavy component impurities such as polymer on the product can be avoided. 99.90% MMA was obtained for the corresponding example in FIG. 1, and 99.95% MMA was obtained for this example.

The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present utility model. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present utility model is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present utility model.

Claims (9)

1. An MMA separation system for byproduct high-purity methylal, which is characterized by comprising the following steps of:

a methylal reaction unit for generating methylal by using the raw materials in the initial aldol condensation product and separating the methylal;

a methanol recovery unit for separating methanol from the aldol condensation product after methylal removal;

the methyl propionate recovery unit is used for separating methyl propionate in the material components from which the methanol is removed;

an MMA recovery unit for separating MMA from the remaining material component;

the methylal reaction unit comprises a methylal tower (1), the top of the methylal tower (1) is connected with a high-pressure tower (7), the material at the top of the methylal tower (1) enters the high-pressure tower (7), the top extract of the high-pressure tower (7) returns to the methylal tower (1),

or alternatively, the process may be performed,

the high-pressure tower (7) is connected with an atmospheric tower (27), and methanol is extracted from the tower kettle of the atmospheric tower (27) and then returned to the methylal tower (1);

and high-concentration methylal is extracted from the tower bottom of the high-pressure tower (7), and the discharged material of the tower bottom of the methylal tower (1) is sent to the methanol recovery unit.

2. MMA separation system for byproduct high-purity methylal according to claim 1, wherein the tower kettle of the high-pressure tower (7) is provided with a heat exchanger (24), and the high-concentration methylal extracted from the tower kettle of the high-pressure tower (7) is extracted after passing through the heat exchanger (24);

the materials at the top of the methylal tower (1) firstly pass through the heat exchanger (24) for heat exchange before entering the high-pressure tower (7);

the tower kettle of the methylal tower (1) is provided with a methylal tower reboiler (25), and the tower top steam of the high-pressure tower (7) enters the upper part of the methylal tower (1) after heat exchange of the methylal tower reboiler (25).

3. MMA separation system by-produced high-purity methylal according to claim 1, characterized in that the tower bottom of the atmospheric tower (27) is provided with a reboiler through which the overhead material of the high-pressure tower (7) enters the atmospheric tower (27).

4. The MMA separation system for by-product high-purity methylal according to claim 1, wherein the methanol recovery unit comprises a methanol recovery tower (2), and the methyl propionate recovery unit is fed with the discharge of the tower bottom of the methanol recovery tower (2).

5. The MMA separation system by-produced high-purity methylal according to claim 1, wherein the methyl propionate recovery unit comprises a dehydration column (3) and a methyl propionate recovery column (4),

the vapor at the top of the dehydration tower (3) is condensed and then sent to a reflux tank (23) to realize liquid-liquid phase separation, wherein an organic phase is taken as a reflux stream to be returned to the top of the dehydration tower (3), the reflux tank (23) extracts decantation water, and the discharge of the tower bottom of the dehydration tower (3) is sent to the methyl propionate recovery tower (4);

methyl propionate is extracted from the top of the methyl propionate recovery tower (4), and the discharge of the tower bottom is sent to an MMA recovery unit.

6. The MMA separation system of high-purity methylal by-product according to claim 5, wherein decanted water is taken out from the reflux drum (23) and sent to the stripping column (8), light components taken out from the top of the stripping column (8) are returned to the methylal column (1), and wastewater is taken out from the bottom of the stripping column (8) and sent out from the boundary zone.

7. The MMA separation system of by-product high-purity methylal according to claim 1, wherein the MMA recovery unit comprises an MMA crude column (5), an MMA refining column (6) and a propionic acid recovery column (10);

the tower top of the MMA crude tower (5) is connected with the MMA refining tower (6), the tower bottom is connected with the propionic acid recovery tower (10), so that a tower top extract of the MMA crude tower (5) is sent to the MMA refining tower (6), a tower bottom discharge is sent to enter the propionic acid recovery tower (10), and a high-concentration MMA is extracted from the tower bottom of the MMA refining tower;

or the tower bottom of the MMA crude tower (5) is connected with the MMA refining tower (6) so that the tower bottom of the MMA crude tower (5) is discharged to the MMA refining tower (6), the tower bottom of the MMA refining tower (6) is connected with the propionic acid recovery tower (10) so that the tower bottom of the MMA refining tower is discharged to the propionic acid recovery tower (10), and high-concentration MMA is produced from the tower top.

8. The MMA separation system for by-producing high-purity methylal according to claim 7, wherein the mixture of propionic acid and methacrylic acid produced from the top of the propionic acid recovery column (10) is fed to the esterification reactor (9), and the bottom of the column is fed out of the boundary zone;

and (3) carrying out esterification reaction on the mixture of propionic acid and methacrylic acid from the propionic acid recovery tower (10) and methanol in the esterification reactor (9), and returning the product to the methylal tower (1).

9. MMA separation system by-produced high-purity methylal according to claim 1 or 2 or 5 or 7, characterized in that the tops of methylal column (1), dehydration column (3), methyl propionate recovery column (4), MMA crude column (5) and MMA refining column (6) are provided with two-stage condenser, the two-stage condenser is connected with reflux tank, and the gaseous product of the top is sent out to the boundary zone after two-stage condensation.

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