Process for recovering amide compounds

Patent metadata

Field	Value
Publication number	US-2021039963-A1
Application number	US-201916967085-A
Country	US
Kind code	A1
Filing date	Nov 15, 2019
Priority date	Dec 18, 2018
Publication date	Feb 11, 2021
Grant date	—

Abstract

There is provided a method for efficiently recovering amide-based compounds such as N-methyl-2-pyrrolidone from a waste liquid containing amide-based compounds such as N-methyl-2-pyrrolidone generated, for example, in a production process of polyarylene sulfide.

First claim

1 . A method for recovering amide-based compounds comprising:
collecting a waste liquid containing water and amide-based compounds into a storage tank; distilling the waste liquid from a stripping section, separating a vapor phase mixture containing water and amide-based compounds which is vaporized at an upper part of the stripping section, and separating a liquid phase mixture containing amide-based compounds which is not vaporized at a lower part of the stripping section; conducting distillation by transferring the vaporized vapor phase mixture containing water and amide-based compounds separated from the upper part of the stripping section to a rectifying section; circulating heat generated in the distillation process of the stripping section and the rectifying section using a heat exchanger; recirculating the vaporized vapor phase mixture containing water and amide-based compounds in the rectifying section, flowing the vaporized water to an upper part of the rectifying section, and flowing the amide compound liquefied by recirculation to a lower part of the rectifying section and then recycling to the stripping section; and flowing out the liquid phase mixture containing amide-based compounds from the stripping section to the lower part of the stripping section.

2 . The method for recovering amide-based compounds according to claim 1 , further comprising
operating one or more heat exchangers between the stripping section and the rectifying section.

3 . The method for recovering amide-based compounds according to claim 1 , wherein the operating the one or more heat exchangers comprises operating one to three heat exchangers.

4 . The method for recovering amide-based compounds according to claim 1 , wherein the one or more heat exchangers are located between 2 nd and 7th stages of a distillation column in the stripping section, based on overhead of a distillation column of the rectifying section.

5 . The method for recovering amide-based compounds according to claim 1 , wherein the collecting a waste liquid step through the flowing out the liquid phase mixture containing amide-based compounds steps are performed continuously and repeatedly at least once.

6 . The method for recovering amide-based compounds according to claim 1 , further comprising operating a compressor connected and installed to the upper part of the stripping section, and operating a reboiler connected and installed to the lower part of the stripping section.

7 . The method for recovering amide-based compounds according to claim 1 , wherein the stripping section performs a distillation process by setting so that a theoretical stage number is the 5th stage to the 10th stage.

8 . The method for recovering amide-based compounds according to claim 1 , wherein the temperature of an overhead region of a distillation column in the stripping section is adjusted to 90° C. to 110° C., and the temperature of a bottom region of the distillation column in the stripping section is adjusted to 170° C. to 190° C.

9 . The method for recovering amide-based compounds according to claim 1 , wherein the temperature of a top region of a distillation column of the rectifying section is adjusted to 125° C. to 145° C., and the temperature of the a bottom region of the distillation column in the rectifying section is adjusted to 125° C. to 145° C.

10 . The method for recovering amide-based compounds according to claim 1 , wherein the rectifying section performs a distillation process by setting so that a theoretical stage number is the 6th stage to the 10th stage.

11 . The method for recovering amide-based compounds according to claim 1 , wherein the amide-based compound is one or more selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), N-cyclohexyl-2-pyrrolidone, N-methyl-ε-caprolactam, 1,3-dialkyl-2-imidazolidinone, and tetramethyl urea.

12 . The method for recovering amide-based compounds according to claim 1 , wherein the waste liquid is a liquid from which fine powders of inorganic salt and polyarylene sulfide are removed from a reaction mixture in a production process of polyarylene sulfide through a pretreatment process using a filtration.

13 . The method for recovering amide-based compounds according to claim 1 , wherein the waste liquid further includes an alkali metal halide, a dihalogenated aromatic compound, an alkali metal sulfide and a polyarylene sulfide.

Assignees

• Lg Chemical Ltd

Inventors

• Jo Sanghwan
• Han Joong Jin
• Kim Hansol

Classifications

• B01D3/146

  Multiple effect distillation · CPC title

• C08G75/02

  Polythioethers · CPC title

• C08J11/02

  of solvents, plasticisers or unreacted monomers · CPC title

• C08G75/0281 Primary

  Recovery or purification · CPC title

• C02F1/04

  by distillation or evaporation · CPC title