Method for producing acetic acid

Patent metadata

Field	Value
Publication number	US-10752572-B2
Application number	US-201816334673-A
Country	US
Kind code	B2
Filing date	May 29, 2018
Priority date	May 29, 2018
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

Provided is a method for industrially efficiently producing acetic acid that yields a good potassium permanganate test result, without enormous cost. A light ends column (first distillation column) is operated with a reflux ratio at a specific level or more, a distillation column (crotonaldehyde-removing column) is provided for treating an organic phase of an overhead condensate from the light ends column, and the crotonaldehyde-removing column is operated under such conditions as to meet at least one of conditions (i) to (iii) as follows: (i) a reflux ratio at the distillation column is 0.01 or more; (ii) at the distillation column, the ratio of a crotonaldehyde concentration in a distillate to a crotonaldehyde concentration in a charge liquid is less than 1; and (iii) at the distillation column, the ratio of a crotonaldehyde concentration in bottoms to a crotonaldehyde concentration in the charge liquid is greater than 1.

First claim

The invention claimed is:

1. A method for producing acetic acid, the method comprising the steps of:
carbonylating methanol with carbon monoxide in a reactor in the presence of a catalytic system, acetic acid, methyl acetate, and water, to give acetic acid in a reaction mixture, the catalytic system including a metal catalyst and methyl iodide;
separating the reaction mixture resulting from the carbonylation step, using at least one selected from evaporators and distillation columns, into at least:
a stream including the metal catalyst;
an acetic acid stream rich in acetic acid; and
a stream rich in light ends as compared with the acetic acid stream;

recycling at least a part of the light ends-rich stream to the reactor; and
removing crotonaldehyde from at least a part of a remainder of the light ends-rich stream by a treatment in a distillation column,
wherein the separation step comprises
a first separation step of separating the reaction mixture, using a first distillation column, into at least a first acetic acid stream rich in acetic acid, and an overhead stream rich in light ends as compared with the first acetic acid stream, and condensing the overhead stream to give a condensate,

wherein a reflux ratio at the first distillation column is controlled as follows:
provided that the condensate is liquid-liquid separated into an aqueous phase and an organic phase,
the reflux ratio for the aqueous phase is 2 or more when the aqueous phase alone is refluxed to the first distillation column;
the reflux ratio for the organic phase is 1 or more when the organic phase alone is refluxed to the first distillation column; and
the total reflux ratio for the aqueous phase and the organic phase is 1.5 or more when both the aqueous phase and the organic phase are refluxed to the first distillation column, or

provided that the condensate is refluxed to the first distillation column without liquid-liquid separation,
the reflux ratio for the condensate is 1.5 or more,

wherein the distillation column is operated in the crotonaldehyde-removing step so as to meet at least one of conditions (i) to (iii) as follows:
(i) a reflux ratio at the distillation column is 0.01 or more;
(ii) at the distillation column, a ratio of a crotonaldehyde concentration (ppm by mass) in a distillate to a crotonaldehyde concentration (ppm by mass) in a charge liquid is less than 1; and
(iii) at the distillation column, a ratio of a crotonaldehyde concentration (ppm by mass) in bottoms to a crotonaldehyde concentration (ppm by mass) in the charge liquid is greater than 1, and
wherein a crotonaldehyde concentration in the first acetic acid stream is controlled to 2.2 ppm by mass or less, and at least one ratio is lowered, to give an acetic acid product that yields a better potassium permanganate test result, where the at least one ratio is selected from the group consisting of:
a ratio (C CR /C ECR ) of a crotonaldehyde concentration C CR (ppm by mass) to a 2-ethylcrotonaldehyde concentration C ECR (ppm by mass) in the first acetic acid stream;
a ratio (C CR /C BA ) of a crotonaldehyde concentration C CR (ppm by mass) to a butyl acetate concentration C BA (ppm by mass) in the first acetic acid stream;
a ratio (C CR /C ECR ) of a crotonaldehyde concentration C CR (ppm by mass) to a 2-ethylcrotonaldehyde concentration C ECR (ppm by mass) in an acetic acid-rich stream resulting from further purification of the first acetic acid stream; and
a ratio (C CR /C BA ) of a crotonaldehyde concentration C CR (ppm by mass) to a butyl acetate concentration C BA (ppm by mass) in the acetic acid-rich stream resulting from further purification of the first acetic acid stream.

2. A method for producing acetic acid, the method comprising the steps of:
carbonylating methanol with carbon monoxide in a reactor in the presence of a catalytic system, acetic acid, methyl acetate, and water, to give acetic acid in a reaction mixture, the catalytic system including a metal catalyst and methyl iodide;
separating the reaction mixture resulting from the carbonylation step, using at least one selected from evaporators and distillation columns, into at least:
a stream including the metal catalyst;
an acetic acid stream rich in acetic acid; and
a stream rich in light ends as compared with the acetic acid stream;

recycling at least a part of the light ends-rich stream to the reactor; and
removing crotonaldehyde from at least a part of a remainder of the light ends-rich stream by a treatment in a distillation column,
wherein the separation step comprises:
a first separation step of separating the reaction mixture, using a first distillation column, into at least a first acetic acid stream rich in acetic acid, and an overhead stream rich in light ends as compared with the first acetic acid stream, and condensing the overhead stream to give a condensate; and
a second separation step of subjecting the first acetic acid stream to distillation in a second distillation column to further purify acetic acid,

wherein a reflux at the first distillation column is controlled as follows:
provided that the condensate is liquid-liquid separated into an aqueous phase and an organic phase,
the reflux ratio for the aqueous phase is 2 or more when the aqueous phase alone is refluxed to the first distillation column;
the reflux ratio for the organic phase is 1 or more when the organic phase alone is refluxed to the first distillation column; and
the total reflux ratio for the aqueous phase and the organic phase is 1.5 or more when both the aqueous phase and the organic phase are refluxed to the first distillation column, or

provided that the condensate is refluxed to the first distillation column without liquid-liquid separation,
the reflux ratio for the condensate is 1.5 or more,

wherein the distillation column is operated in the crotonaldehyde-removing step so as to meet at least one of conditions (i) to (iii) as follows:
(i) a reflux ratio at the distillation column is 0.01 or more;
(ii) at the distillation column, a ratio of a crotonaldehyde concentration (ppm by mass) in a distillate to a crotonaldehyde concentration (ppm by mass) in a charge liquid is less than 1; and
(iii) at the distillation column, a ratio of a crotonaldehyde concentration (ppm by mass) in bottoms to a crotonaldehyde concentration (ppm by mass) in the charge liquid is greater than 1, and
wherein a crotonaldehyde concentration in the first acetic acid stream is controlled to 2.2 ppm by mass or less and/or a reflux ratio at the second distillation column is controlled to 0.1 or more, and at least one ratio is lowered, to give an acetic acid product that yields a better potassium permanganate test result, where the at least one ratio is selected from the group consisting of:
a ratio (C CR /C ECR ) of a crotonaldehyde concentration C CR (ppm by mass) to a 2-ethylcrotonaldehyde concentration C ECR (ppm by mass) in the first acetic acid stream;
a ratio (C CR /C BA ) of a crotonaldehyde concentration C CR (ppm by mass) to a butyl acetate concentration C BA (ppm by mass) in the first acetic acid stream;
a ratio (C CR /C ECR ) of a crotonaldehyde concentration C CR (ppm by mass) to a 2-ethylcrotonaldehyde concentration C ECR (ppm by mass) in an acetic acid-rich stream from the second separation step; and
a ratio (C CR /C BA ) of a crotonaldehyde concentration C CR (ppm by mass) to a butyl acetate concentration C BA (ppm by mass) in the acetic acid-rich stream from the second separation step.

3. The acetic acid production method according to claim 1 ,
wherein the separation step comprises:
an evaporation step of separating the reaction mixture resulting from the carbonylation step into a vapor stream and a residue stream, using an evaporator; and
a light ends-removing step, as the first sepa

Assignees

• Daicel Corp

Inventors

• Shimizu Masahiko

Classifications

• C07C53/08

  Acetic acid (pyroligneous acid C10C; preparation of vinegar C12J) · CPC title

• C07C51/44

  by distillation · CPC title

• C07C51/12 Primary

  on an oxygen-containing group in organic compounds, e.g. alcohols · CPC title

• C07C51/445 Primary

  by steam distillation · CPC title

• Y02P20/584

  Recycling of catalysts · CPC title