Purifying method, production method, and distillation apparatus for acrylonitrile

Patent metadata

Field	Value
Publication number	US-10294197-B2
Application number	US-201715756617-A
Country	US
Kind code	B2
Filing date	Aug 21, 2017
Priority date	Oct 21, 2016
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

A method for purifying acrylonitrile involving a purification step of distilling an acrylonitrile solution containing acrylonitrile, hydrogen cyanide, and water, wherein the purification step involves a first step of separating a side stream withdrawn from a first position of a distillation column into an organic layer and an aqueous layer, and then returning the organic layer to a second position of the distillation column, the second position being positioned below the first position and a second step of supplying water from a third position of the distillation column, the third position being positioned below the second position and above a lowermost stage of the distillation column is a novel method in which stabilization of product quality and reduction in load on the acrylonitrile production process can be achieved by stabilizing a hydrocyanic acid-removing dehydration column in the process for producing acrylonitrile.

First claim

The invention claimed is:

1. A method for purifying acrylonitrile comprising a purification step of distilling an acrylonitrile solution comprising acrylonitrile, hydrogen cyanide, and water, wherein
the purification step comprises:
a first step of separating a side stream withdrawn from a first position of a distillation column into an organic layer and an aqueous layer, and then returning the organic layer to a second position of the distillation column, the second position being positioned below the first position; and
a second step of supplying water from a third position of the distillation column, the third position being positioned below the second position and above a lowermost stage of the distillation column.

2. A method for producing acrylonitrile comprising:
a reaction step of reacting: propylene and/or propane; ammonia; and oxygen in the presence of a catalyst;
an absorption step of allowing a gas comprising generated acrylonitrile, acetonitrile, and hydrogen cyanide to be absorbed in water, thereby obtaining an aqueous solution;
a collection step of distilling the aqueous solution to obtain an acrylonitrile solution comprising acrylonitrile, hydrogen cyanide, and water; and
a purification step of separating hydrogen cyanide and water from the acrylonitrile solution to obtain acrylonitrile, wherein
the method for purifying acrylonitrile according to claim 1 is used in the purification step.

3. A distillation apparatus for purifying acrylonitrile, comprising:
a distillation column;
a first line that takes out a side stream from a first position of the distillation column;
a cooler that cools the side stream;
a decanter that separates the side stream having passed through the cooler into an organic layer and an aqueous layer;
a second line that returns the organic layer to a second position of the distillation column, the second position being positioned below the first position; and
a third line that introduces water from a third position of the distillation column, the third position being positioned below the second position and above a lowermost stage of the distillation column.

Assignees

• Asahi Chemical Ind

Inventors

• Sano Kazuhiko

Classifications

• B01D3/14

  Fractional distillation {or use of a fractionation or rectification column} · CPC title

• B01D3/40

  Extractive distillation · CPC title

• C07C253/26

  containing carbon-to-carbon multiple bonds, e.g. unsaturated aldehydes · CPC title

• C07C255/08

  Acrylonitrile; Methacrylonitrile · CPC title

• C07C253/34 Primary

  Separation; Purification · CPC title