Process for producing acetic acid

Patent metadata

Field	Value
Publication number	US-9006483-B2
Application number	US-201314378049-A
Country	US
Kind code	B2
Filing date	Mar 12, 2013
Priority date	Mar 14, 2012
Publication date	Apr 14, 2015
Grant date	Apr 14, 2015

Abstract

A production process of acetic acid according to the present invention inhibits concentration of hydrogen iodide and improves a liquid-liquid separation of an overhead from a distillation column. Acetic acid is produced by distilling a mixture containing hydrogen iodide, water, acetic acid and methyl acetate in a first distillation column (3) to form an overhead and a side cut stream or bottom stream containing acetic acid, cooling and condensing the overhead in a condenser (C3) to form separated upper and lower phases in a decanter (4). According to this process, a zone having a high water concentration is formed in the distillation column above the feed position of the mixture by feeding a mixture having a water concentration of not less than an effective amount to not more than 5% by weight (e.g., 0.5 to 4.5% by weight) and a methyl acetate concentration of 0.5 to 9% by weight (e.g., 0.5 to 8% by weight) as the mixture to the distillation column and distilling the mixture. In the zone having a high water concentration, hydrogen iodide is allowed to react with methyl acetate to produce methyl iodide and acetic acid.

First claim

The invention claimed is:

1. A process for producing acetic acid, comprising:
distilling a mixture containing hydrogen iodide, water, methyl iodide, acetic acid, and methyl acetate to form an overhead containing a lower boiling point component, and
condensing the overhead to form separated liquid phases,
wherein the mixture contains an effective amount of water in a concentration of not more than 5% by weight and methyl acetate in a concentration of 0.5 to 9% by weight, and is separated, in the distillation step, into the overhead containing methyl iodide and a side cut stream or bottom stream containing acetic acid.

2. The process according to claim 1 , wherein the mixture has a methyl acetate concentration of 0.07 to 1.2 mol/L and a water concentration of 0.28 to 2.8 mol/L, and is distilled continuously.

3. The process according to claim 1 , wherein the mixture contains 0.5 to 4.5% by weight of water and 0.5 to 8% by weight of methyl acetate, and is subjected to the distillation step.

4. The process according to claim 1 , wherein the mixture further contains dimethyl ether.

5. The process according to claim 1 , wherein the mixture is fed to a distillation column from an intermediate or lower position of the distillation column in height.

6. The process according to claim 1 , wherein a zone having a high water concentration is formed inside a distillation column at a position upper than a position at which the mixture is fed to the distillation column,
in the zone having the high water concentration, hydrogen iodide is allowed to react with methyl acetate for producing methyl iodide and acetic acid, and
the distillation provides the overhead containing the resulting methyl iodide.

7. The process for producing acetic acid according to claim 1 , wherein
methanol is allowed to continuously react with carbon monoxide by using a catalyst containing a group 8 metal of the Periodic Table, an ionic iodide, and methyl iodide in the presence of water,
the reaction product is separated into a low-volatile phase component and a volatile phase component by a flash distillation,
the volatile phase component as the mixture is distilled to form the overhead containing methyl iodide and the side cut stream or bottom stream containing acetic acid, and
the overhead is condensed to form an aqueous phase and an organic phase,
and wherein the volatile phase component is distilled while being adjusted to a water concentration of an effective amount and not more than 5% by weight and a methyl acetate concentration of 0.5 to 9% by weight in a distillation atmosphere of the volatile phase component in terms of a condensate or liquid form.

8. The process according to claim 1 , wherein at least one member selected from the group consisting of methyl acetate, methanol and dimethyl ether, and if necessary water, is added to the volatile phase component as the mixture or a distillation atmosphere thereof as the mixture to adjust the concentrations of water and methyl acetate, and the resulting volatile phase component is distilled.

9. The process according to claim 1 , wherein a distillation atmosphere of a volatile phase component is formed in the distillation column at a height equal to or upper than a feed site of the volatile phase component.

10. The process according to claim 1 , wherein the mixture contains 1 to 4.3% by weight of water and 0.8 to 7.5% by weight of methyl acetate, and is subjected to the distillation step.

11. The process according to claim 1 , wherein the mixture has a hydrogen iodide concentration of 100 to 10000 ppm, and is subjected to a distillation to form the side cut stream having a hydrogen iodide concentration of 1 to 350 ppm.

12. The process according to claim 1 , wherein the separated liquid phases are a lower phase and an upper phase, the lower phase has a methyl acetate concentration of 1 to 15% by weight, and the upper phase has a methyl acetate concentration of 0.4 to 8% by weight.

13. A method for improving a liquid-liquid separation of a condensate while reducing a concentration of hydrogen iodide in an overhead and a side cut stream, comprising:
distilling a mixture containing hydrogen iodide, water, methyl iodide, acetic acid, and methyl acetate to form an overhead containing a lower boiling point component, and
condensing the overhead to give a condensate containing separated liquid phases,
wherein the mixture contains an effective amount of water in a concentration of not more than 5% by weight and methyl acetate in a concentration of 0.5 to 9% by weight.

14. The method according to claim 13 , wherein the concentration of hydrogen iodide in the overhead and the side cut stream is reduced by adjusting a concentration of methyl acetate in the mixture to 0.5 to 8% by weight.

15. The method according to claim 13 , wherein said method improves the liquid-liquid separation of the condensate, wherein concentrations of methyl iodide and methyl acetate in the lower phase are adjusted to 76 to 98% by weight and 1 to 15% by weight, respectively (with the proviso that the total of components in the lower phase is 100% by weight), and concentrations of water and methyl acetate in the upper phase are adjusted to 50 to 90% by weight and 0.4 to 8% by weight, respectively (with the proviso that the total of components in the upper phase is 100% by weight).

Assignees

• Daicel Corp

Inventors

• Shimizu Masahiko
• Miura Hiroyuki
• Ueno Takashi
• Nakajima Hidehiko

Classifications

• C07C51/44 Primary

  by distillation · CPC title

• B01D3/009

  in combination with chemical reactions · CPC title

• C07C51/48

  by liquid-liquid treatment · CPC title