RU-2861453-C2 - METHOD FOR PRODUCING HIGH-PURITY (METH)ACRYLIC ACID

Abstract

FIELD: chemical industry. SUBSTANCE: method for producing (meth)acrylic acid (MAA) is proposed, comprising bringing a mixed gas containing MAA into contact with water in an absorption column to obtain first and second aqueous MAA solutions, withdrawing the first aqueous MAA solution from the bottom of the absorption column and feeding it to a crystalliser, and withdrawing the second aqueous MAA solution from a side part of the absorption column and feeding it to a water separation column to obtain a distillate, which in turn is fed to a high-boiling by-product separation column. The top exit stream of the high-boiling by-product separation column, containing MAA, is fed to the crystalliser, where purified MAA is obtained and a part of the mother liquor returned to the crystalliser is pumped to the absorption column and the remainder to the water separation column. The first aqueous MAA solution and the top exit stream of the high-boiling by-product separation column form a mixed stream which is fed to the crystalliser. Obtaining a distillate containing MAA and high-boiling by-products comprises feeding a part of the second aqueous MAA solution to an extraction column as an inlet stream and feeding the remainder to the water separation column. In the extraction column, contacting an extracting solvent and the inlet stream of the extraction column is carried out, and the extract stream is fed to the water separation column, with separation of the top exit stream and the distillate as the bottom exit stream. EFFECT: reducing energy consumption in the process of separating MAA and impurities and obtaining a high-purity target product. 8 cl, 4 dwg, 4 ex

Inventors

• YOO, SUNG JIN
• JANG, KYUNG SOO
• LEE, SUNG KYU

Dates

Publication Date

20260505

Application Date

20230824

Priority Date

20220830

Claims (18)

1. 1. A method for producing (meth)acrylic acid, comprising:
2. introducing a mixed gas containing (meth)acrylic acid into reaction with water in an absorption column to obtain first and second aqueous solutions of (meth)acrylic acid;
3. removing the first aqueous solution of (meth)acrylic acid from the lower part of the absorption column and feeding the solution into the crystallizer, and removing the second aqueous solution of (meth)acrylic acid from the side part of the absorption column;
4. feeding a second aqueous solution of (meth)acrylic acid into a water separation column to obtain a distillate comprising (meth)acrylic acid and high-boiling by-products;
5. feeding the distillate to a high-boiling by-product separation column and feeding the top effluent of the high-boiling by-product separation column containing (meth)acrylic acid to a crystallizer; and
6. obtaining purified (meth)acrylic acid in a crystallizer and pumping part of the mother liquor returned to the crystallizer into an absorption column and the remainder into a water separation column,
7. wherein the first aqueous solution of (meth)acrylic acid withdrawn from the bottom of the absorption column and the upper outlet stream of the high-boiling by-product separation column form a mixed stream and are fed to the crystallizer, and the content of (meth)acrylic acid in the mixed stream is from 85 to 99 wt.%,
8. wherein the production of a distillate containing (meth)acrylic acid and high-boiling by-products involves:
9. feeding a portion of the second aqueous solution of (meth)acrylic acid into the extraction column as an input stream of the extraction column and feeding the remainder into the water separation column as an input stream of the water separation column;
10. introducing the extracting solvent and the input stream of the extraction column into contact in the extraction column and feeding the extract stream including the extract to the water separation column; and
11. separating an upper outlet stream of the water separation column including water and a distillate including (meth)acrylic acid and high-boiling by-products as a lower outlet stream of the water separation column in a water separation column.
12. 2. A method for producing (meth)acrylic acid according to claim 1, wherein the content of (meth)acrylic acid in the first aqueous solution of (meth)acrylic acid is from 75 wt.% to 95 wt.% and the content of (meth)acrylic acid in the second aqueous solution of (meth)acrylic acid is from 30 wt.% to 60 wt.%.
13. 3. The method for producing (meth)acrylic acid according to claim 1, wherein the second aqueous solution of (meth)acrylic acid is withdrawn from the side portion at a height of 40% to 80% from the top to the bottom of the absorption column.
14. 4. The method for producing (meth)acrylic acid according to claim 1, wherein the content of (meth)acrylic acid in the upper outlet stream of the high-boiling by-product separation column is from 90 wt.% to 99 wt.%.
15. 5. The method for producing (meth)acrylic acid according to claim 1, wherein the flow rate of acetic acid withdrawn from the top of the absorption column is from 20 wt.% to 80 wt.% based on the flow rate of acetic acid introduced into the absorption column.
16. 6. The method for producing (meth)acrylic acid according to claim 1, wherein the ratio of the feed flow rate into the extraction column, fed into the extraction column, to the flow rate of the second aqueous solution of (meth)acrylic acid is from 20 wt.% to 60 wt.%.
17. 7. The method for producing (meth)acrylic acid according to claim 1, wherein the upper outlet stream of the water separation column is fed to a layer separator, a portion of the aqueous layer, including water and acetic acid, is pumped into an absorption column and the remainder is removed as wastewater.
18. 8. The method for producing (meth)acrylic acid according to claim 1, wherein the extracting solvent and the input stream of the extraction column are brought into contact in the extraction column to further produce a raffinate stream comprising the raffinate, and the raffinate stream is fed to a layer separator.

Description

Field of technology to which the invention relates CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority of Korean Patent Application No. 10-2022-0109514, filed on August 30, 2022, and Korean Patent Application No. 10-2023-0107059, filed on August 16, 2023, the entire contents of which are incorporated herein as part of the description. Field of technology to which the invention relates The present invention relates to a method for producing high-purity (meth)acrylic acid. State of the art (Meth)acrylic acid is usually produced by introducing a compound such as propane, propylene, and (meth)acrolein into a gas-phase oxidation reaction in the presence of a catalyst. For example, propane, propylene, etc., are converted via (meth)acrolein into (meth)acrylic acid by a gas-phase oxidation reaction in the presence of a suitable catalyst in a reactor, and a mixed gas comprising (meth)acrylic acid, unreacted propane or propylene, (meth)acrolein, an inert gas, carbon dioxide, water vapor, and various organic reaction by-products (such as acetic acid, low-boiling-point by-products, and high-boiling-point by-products) is obtained in the last step in the reactor. A mixed gas containing (meth)acrylic acid is reacted with an absorbent solvent, such as water, in an absorption column to produce a (meth)acrylic acid solution. Furthermore, the subsequent recovery of the (meth)acrylic acid contained in the (meth)acrylic acid solution typically involves extraction, distillation, and purification. Various methods for adjusting process conditions, procedure order, and other factors have been proposed to improve the efficiency of (meth)acrylic acid recovery. However, since the absorbent solvent, such as water, used in the absorption column has a high specific heat capacity, a large amount of thermal energy must be expended to separate byproducts, including the absorbent solvent, from the (meth)acrylic acid solution through a process such as distillation. Simplifying and shortening the subsequent process to reduce energy consumption may reduce energy consumption, but it may make it difficult to obtain high-purity (meth)acrylic acid. Therefore, it is urgent to use a new technology that can reduce the energy consumption in separating (meth)acrylic acid and by-products by distillation and obtain high-purity (meth)acrylic acid from (meth)acrylic acid solution. Disclosure Technical challenge In order to solve the problems specified in the Prior Art, the object of the present invention is to provide a method for isolating (meth)acrylic acid, which can further reduce energy consumption in the purification procedure and obtain high-purity (meth)acrylic acid at a high recovery rate. Solving a technical problem In one general aspect, a method for producing (meth)acrylic acid includes: introducing a mixed gas containing (meth)acrylic acid into a reaction with water in an absorption column to obtain first and second aqueous solutions of (meth)acrylic acid; withdrawing a first aqueous solution of (meth)acrylic acid from a bottom of the absorption column and feeding the solution to a crystallizer, and withdrawing a second aqueous solution of (meth)acrylic acid from a side of the absorption column; feeding the second aqueous solution of (meth)acrylic acid to a water separation column to obtain a distillate including (meth)acrylic acid and high-boiling by-products; feeding the distillate to a high-boiling by-product separation column, and feeding an overhead stream of the high-boiling by-product separation column containing (meth)acrylic acid to a crystallizer; and obtaining purified (meth)acrylic acid in a crystallizer and pumping part of the mother liquor returned to the crystallizer into an absorption column and the remainder into a water separation column. Beneficial effects In the method for producing (meth)acrylic acid proposed in the present invention, the amount of water introduced into the absorption column for purifying (meth)acrylic acid is minimized and a portion of the aqueous solution of (meth)acrylic acid withdrawn from the absorption column is fed directly to a crystallizer without undergoing a distillation procedure, thereby reducing the amount of energy consumed in the entire method. In addition, a water separation column and a layer separator can be installed after the absorption column to separate and remove acetic acid as a by-product, and thus the loss of (meth)acrylic acid at the top of the absorption column can be reduced compared with the case where all the acetic acid is removed from the top of the absorption column. In addition, the high-boiling by-product can be separated after the water separation column to prevent the high-boiling by-product from accumulating in the system, and the upper outlet stream of the high-boiling by-product can be re-directed for crystallization, thereby further reducing the loss of (meth)acrylic acid. Description of drawings Fig. 1 is a flow chart of the pro