Process for controlling a reboiler during alcohol recovery and reduced ester formation

Patent metadata

Field	Value
Publication number	US-8927787-B2
Application number	US-201213457100-A
Country	US
Kind code	B2
Filing date	Apr 26, 2012
Priority date	Apr 26, 2011
Publication date	Jan 6, 2015
Grant date	Jan 6, 2015

Abstract

The present invention is related to processes for the separation of ethanol from a crude ethanol product obtained from the hydrogenation of acetic acid. The crude ethanol product is separated in one or more columns. A reboiler is used following one or more of the columns for reducing ester formation.

First claim

We claim:

1. A process for producing ethanol, comprising:
hydrogenating acetic acid and/or an ester thereof in a reactor in the presence of a catalyst to form a crude ethanol product;
separating at least a portion of the crude ethanol product in a first distillation column to yield a first distillate comprising acetaldehyde and ethyl acetate and a tower bottoms comprising ethanol, acetic acid and water;
feeding a first portion of the tower bottoms to a reboiler to generate a reboiler vapor stream;
withdrawing a second portion of the tower bottoms as a residue product comprising less than 1.5 wt. % ethyl acetate;
separating at least a portion of the residue product in a second distillation column to yield a second residue comprising acetic acid and water and a second distillate comprising ethanol and ethyl acetate; and
separating at least a portion of the second distillate to yield a third residue comprising ethyl acetate and a third residue comprising ethanol.

2. The process of claim 1 , wherein at least 50% of the ethanol in the crude ethanol product is withdrawn into the tower bottoms.

3. The process of claim 1 , wherein the residue product comprises less than 1.1 wt. % ethyl acetate.

4. The process of claim 1 , wherein the first portion of the tower bottoms comprises less than 1 wt. % ethyl acetate.

5. The process of claim 1 , further comprising returning at least a portion of the third distillate to the first distillation column.

6. The process of claim 1 , further comprising returning at least a portion of the first distillate to the reactor.

7. The process of claim 1 , wherein the first distillate is further separated to yield an ethanol stream and a raffinate stream comprising ethyl acetate, and at least a portion of the raffinate stream is returned to the reactor.

8. The process of claim 7 , wherein at least a portion of the ethanol stream is fed to the third distillation column.

9. The process of claim 1 , wherein the reboiler is selected from the group consisting of internal reboiler, kettle reboiler, jacketed kettle reboiler, thermosyphon reboiler, falling film reboiler, fire reboiler, and forced circulation reboiler.

10. The process of claim 1 , wherein the second distillate is further separated to yield an ethanol stream and a raffinate stream comprising ethyl acetate.

11. The process of claim 1 , wherein the third distillate is further separated to yield an ethanol stream and a raffinate stream comprising ethyl acetate.

12. The process of claim 1 , wherein the second distillate is substantially free of acetic acid.

13. The process of claim 1 , further comprising removing water from at least a portion of the second distillate using an adsorption unit, membrane, extractive column distillation, molecular sieve, or a combination thereof to yield an ethanol product stream having a lower water content than the at least a portion of the second distillate.

14. The process of claim 13 , wherein the third residue comprises less than 8 wt. % water.

15. The process of claim 1 , wherein the acetic acid is formed from methanol and carbon monoxide, wherein each of the methanol, the carbon monoxide, and hydrogen for the hydrogenating step is derived from syngas, and wherein the syngas is derived from a carbon source selected from the group consisting of natural gas, oil, petroleum, coal, biomass, and combinations thereof.

16. A process for producing ethanol, comprising:
hydrogenating acetic acid and/or an ester thereof in a reactor in the presence of a catalyst to form a crude ethanol product;
separating at least a portion of the crude ethanol product in a first distillation column to yield a first distillate comprising acetaldehyde and ethyl acetate and a tower bottoms comprising ethanol, acetic acid, and water;
feeding the tower bottoms to a reboiler to generate a reboiler vapor stream, and a residue product, wherein ethyl acetate is formed in the reboiler and the residue product comprises less than 1.5 wt. % ethyl acetate;
separating at least a portion of the residue product in a second distillation column to yield a second residue comprising acetic acid and water and a second distillate comprising ethanol, and ethyl acetate; and
separating at least a portion of the second distillate to yield a third distillate comprising ethyl acetate and a third residue comprising ethanol.

17. A process for producing ethanol comprising:
hydrogenating acetic acid and/or an ester thereof in a reactor in the presence of a catalyst to form a crude ethanol product;
separating a portion of the crude ethanol product in a first distillation column to yield a first distillate comprising acetaldehyde and ethyl acetate and a tower bottoms comprising ethanol, acetic acid and water;
feeding the tower bottoms to a reboiler to generate a reboiler vapor stream, and a residue product, wherein ethyl acetate is formed in the reboiler and the residue product comprises less than 1.5 wt. % ethyl acetate;
separating a portion of the residue product in a second distillation column to yield a second residue comprising acetic acid and a second distillate comprising ethanol, ethyl acetate and water;
removing water from at least a portion of the second distillate to yield an ethanol product stream having a lower water content than the at least a portion of the second distillate; and
separating at least a portion of the ethanol product stream in a third distillation column to yield a third distillate comprising ethyl acetate and a third residue comprising ethanol and less than 8 wt. % water.

18. The process of claim 17 , wherein removing water using an adsorption unit, membrane, extractive column distillation, molecular sieves, or a combination thereof.

19. A process for producing ethanol comprising:
hydrogenating acetic acid and/or an ester thereof in a reactor in the presence of a catalyst to form a crude ethanol product;
separating a portion of the crude ethanol product in a first distillation column to yield a first distillate comprising acetaldehyde and ethyl acetate and a tower bottoms comprising ethanol, and acetic acid;
feeding the tower bottoms to a reboiler to generate a reboiler vapor stream, and a residue product, wherein ethyl acetate is formed in the reboiler and the residue product comprises less than 1.5 wt. % ethyl acetate;
separating a portion of the residue product in a second distillation column to yield a second residue comprising high boiling point components and a second distillate comprising ethanol and ethyl acetate; and
separating at least a portion of the second distillate to yield a third distillate comprising ethyl acetate and a third residue comprising ethanol;
wherein the residue product comprises more ethyl acetate than the tower bottoms.

20. The process of claim 19 , wherein the high boiling point components are selected from the group consisting of acetic acid, water, alcohols having more than 2 carbon atoms, and mixtures thereof.

Assignees

• Warner R Jay
• Duff Emily
• Johnston Victor J
• Lee David
• Orosco Adam
• Celanese Int Corp

Inventors

• Warner R Jay
• Duff Emily
• Johnston Victor J
• Lee David
• Orosco Adam

Classifications

• C07C31/08

  Ethanol · CPC title

• C07C29/149

  with hydrogen or hydrogen-containing gases · CPC title

• C07C51/12 Primary

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

• C07C53/08

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

• C07C29/80

  by distillation · CPC title