Process for producing acetic acid

Patent metadata

Field	Value
Publication number	US-10265639-B2
Application number	US-201715507137-A
Country	US
Kind code	B2
Filing date	Jan 16, 2017
Priority date	Jul 7, 2016
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

A process for separating or removing permanganate reducing compounds (PRC's) from a first mixture containing at least one PRC, methyl iodide, and water comprises the steps of: feeding the first mixture to a feed port of a distillation column, and distilling and separating the first mixture into an upper stream and a lower stream, wherein the distillation of the first mixture forms a second mixture at an upper position than the feed port, and the process further comprises the steps of: withdrawing the second mixture as the upper stream, and withdrawing the lower stream from a lower position than the feed port.

First claim

The invention claimed is:

1. A process for separating or removing permanganate reducing compounds (PRC's) from a first mixture containing at least one PRC, methyl iodide, and water, the process comprising the steps of:
feeding the first mixture to a feed port of a distillation column, and
distilling and separating the first mixture into an upper stream and a lower stream, the upper stream being at least one stream selected from the group consisting of an overhead stream and a side-cut stream,
wherein the distillation of the first mixture allows at least a portion of water in the first mixture to rise to an upper position than the feed port to form a second mixture containing the portion of water, and
the process further comprises the steps of: withdrawing the second mixture as the upper stream,
withdrawing the lower stream from a lower position than the feed port, the lower stream having a water content, the water content of the lower stream being lower than that of the first mixture, and
wherein the first mixture is separated into the upper stream and the lower stream without supply of additional water to the distillation column,
the withdrawn upper stream is biphasically separated into an aqueous phase containing at least acetaldehyde and an organic phase containing at least methyl iodide, and
the distillation of the first mixture comprises at least one of the following (A) and (B):
(A) the lower stream has a ratio of water relative to methyl iodide lower than the first mixture, and
(B) not less than 1% by weight of water in the first mixture is transferred or distributed to the upper stream, and not more than 99% by weight of water in the first mixture is transferred or distributed to the lower stream.

2. A process according to claim 1 , wherein the distillation of the first mixture allows at least a portion of water in the first mixture to rise to an upper position than the feed port to form the second mixture containing the portion of water, wherein the second mixture is azeotropic, and
the process comprises the steps of:
withdrawing the second mixture as the upper stream, and
withdrawing the lower stream from a lower position than the feed port, the water content of the lower stream being lower than that of the first mixture.

3. A process according to claim 1 , wherein not less than 5% by weight of water in the first mixture is transferred or distributed to the upper stream, and not more than 95% by weight of water in the first mixture is transferred or distributed to the lower stream.

4. A process according to claim 1 , wherein the distillation of the first mixture forms a concentration zone of the PRC's and methyl iodide at an upper position than the feed port of the distillation column and allows at least a portion of water in the first mixture to rise to the concentration zone; and a stream or fluid in the concentration zone is withdrawn as the upper stream.

5. A process according to claim 4 , wherein a mixture falling from the concentration zone is withdrawn as the side-cut stream.

6. A process according to claim 1 , wherein the first mixture contains 10 ppm to 30% by weight acetaldehyde, 0.1 to 90% by weight methyl iodide, and 0.1 to 90% by weight water, provided that the total amount of the first mixture, including an impurity or impurities, is 100% by weight.

7. A process according to claim 1 , wherein the first mixture comprises at least a portion of an organic phase, at least a portion of an aqueous phase, or a mixture containing the organic phase and the aqueous phase, and the first mixture has a biphasically separable composition.

8. A process according to claim 1 , wherein the first mixture comprises acetaldehyde, methyl iodide, and water and further comprises at least one of (a) or (b):
(a) methyl acetate,
(b) at least one member selected from the group consisting of acetic acid, methanol, dimethyl ether, and an acetaldehyde derivative.

9. A process according to claim 1 , wherein the withdrawn upper stream is biphasically separated into an aqueous phase containing at least acetaldehyde and an organic phase containing at least methyl iodide, and the process further comprises a step of recycling the organic phase to the distillation step by the following method (a), (b), or (c):
(a) separating the aqueous phase, and recycling the organic phase to the distillation column;
(b) recycling a portion of the aqueous phase and the organic phase to the distillation column;
(c) subjecting at least a portion of the aqueous phase to at least one selected from the group consisting of distillation in a succeeding distillation step and water extractive distillation in a succeeding distillation step, and directly or indirectly recycling the organic phase to the distillation column.

10. A process according to claim 1 , wherein the withdrawn upper stream is biphasically separated into an aqueous phase and an organic phase, and the process further comprises the steps of:
directly or indirectly recycling the organic phase to the distillation step,
distilling at least a portion of the aqueous phase in a succeeding distillation step, and
directly or indirectly feeding a miscible solvent to the distillation column, wherein the miscible solvent is miscible with the organic phase and is at least one member selected from the group consisting of water, acetic acid, methyl iodide, and methanol.

11. A process according to claim 1 , the process further comprising:
a reaction step of continuously carbonylating methanol in the presence of a catalyst system comprising a metal catalyst, a metal halide, and methyl iodide;
a flash evaporation step of continuously separating the reaction mixture into a volatile phase and a less-volatile phase, the volatile phase containing product acetic acid and methyl iodide, and the less-volatile phase containing the metal catalyst and the metal halide;
a distillation step of continuously separating the volatile phase into an overhead and a stream containing acetic acid, the overhead containing methyl iodide and by-product acetaldehyde; and
a step of condensing a gaseous phase to form two phases, the gaseous phase being produced from at least one step selected from the group consisting of these steps and containing at least acetaldehyde and methyl iodide.

Assignees

• Daicel Corp

Inventors

• Shimizu Masahiko
• Mizutani Yoshihisa
• Miura Hiroyuki

Classifications

• C07C51/44

  by distillation · CPC title

• C07C51/12

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

• B01D3/4261

  Side stream · CPC title

• B01D3/4255

  Head-, side-, bottom- and feed stream · CPC title

• B01D3/40 Primary

  Extractive distillation · CPC title