Process for the production of ethanol by hydrogenation of methyl acetate

Patent metadata

Field	Value
Publication number	US-10464871-B2
Application number	US-201415107779-A
Country	US
Kind code	B2
Filing date	Dec 19, 2014
Priority date	Dec 24, 2013
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

Process for the production of ethanol from acetic acid and hydrogen, said process comprising: reacting in an esterification reaction vessel methanol with acetic acid in the presence of an esterification catalyst and an entrainer to form a product comprising entrainer, methyl acetate and water, and in a distillation column, recovering from the product an overhead product fraction comprising methyl acetate, methanol and water, feeding the overhead product fraction, together with hydrogen, into a hydrogenation unit containing a copper based hydrogenation catalyst, to produce a hydrogenation product stream comprising ethanol, methanol, unreacted methyl acetate, unreacted hydrogen, ethyl acetate and water, cooling the hydrogenation product stream; separating the cooled hydrogenation product stream into a liquid phase which comprises the majority of the methanol, ethanol, methyl acetate, ethyl acetate and water, and a gaseous phase which comprises the majority of the unreacted hydrogen; recycling at least part of the gaseous phase to the hydrogenation unit; separating a lower boiling product stream comprising methanol, methyl acetate and ethyl acetate, and a higher boiling product stream comprising ethanol, water, from the liquid phase; recycling at least part of the lower boiling product stream to the esterification reaction vessel; and, optionally removing water from the higher boiling product stream.

First claim

The invention claimed is:

1. A process for the production of ethanol from acetic acid and hydrogen, said process comprising the following steps:
(1) reacting in an esterification reaction vessel methanol at elevated temperature with acetic acid in the presence of an esterification catalyst and an entrainer which is sparingly soluble in water and which forms a minimum boiling point azeotrope therewith to form a product comprising entrainer, methyl acetate and water, and in a distillation column, recovering from the product an overhead product comprising methyl acetate, methanol and water, and from an intermediate point in the column removing a liquid sidestream fraction comprising water, methanol, entrainer and methyl acetate, wherein the molar ratio of acetic acid to methanol in the esterification reaction vessel is in the range of from 1:1.1 to 1:1.8, and the distillation column is operated at an overall pressure of at most 5 bara, and wherein the amount of water present in the overhead product fraction comprising methyl acetate, methanol and water is in the range of from 0.5 to 5 mol %;
(2) feeding the overhead product fraction comprising methyl acetate, methanol and water form step 1, together with hydrogen, into a hydrogenation unit containing a copper based hydrogenation catalyst, wherein said hydrogenation unit is operated in the vapour phase at a temperature in the range of from 180 to 270° C., and a pressure in the range of from 20 to 100 bara, to produce a hydrogenation product stream comprising ethanol, methanol, unreacted methyl acetate, unreacted hydrogen, ethyl acetate and water, wherein the total molar ratio of hydrogen to methyl acetate in the hydrogenation unit is in the range of from 5:1 to 20:1;
(3) cooling the hydrogenation product stream from step 2 to a temperature below 120° C. and a pressure which is no more than 10 bar lower than the pressure of the hydrogenation unit, such that the majority of the methanol, ethanol, methyl acetate, ethyl acetate and water present in the hydrogenation product stream condense;
(4) separating the cooled hydrogenation product stream form step 3 into a liquid phase which comprises the majority of the methanol, ethanol, methyl acetate, ethyl acetate and water, and a gaseous phase which comprises the majority of the unreacted hydrogen;
(5) recycling at least part of the gaseous phase from step 4 to the hydrogenation unit of step 2;
(6) separating a lower boiling product stream comprising methanol, methyl acetate and ethyl acetate, and a higher boiling product stream comprising ethanol, water, from the liquid phase of step 4 in in a distillation column operated at an overall pressure of at most 5 bara; and
(7) recycling at least 80 vol % of the lower boiling product stream from step 6 to the esterification reaction vessel of step 1.

2. A process according to claim 1 , wherein in step 1, a fraction comprising the majority of the methanol, entrainer and methyl acetate in the sidestream fraction is separated from the water, and the fraction comprising the majority of the methanol, entrainer and methyl acetate is returned to a point in the distillation column of step 1 which is lower than the sidestream fraction removal point.

3. A process according to claim 1 , wherein in step 1, the esterification reaction vessel is a kettle at the base of the distillation column.

4. A process according to claim 1 , wherein in step 1, the distillation column contains from 15 to 50 theoretical plates.

5. A process according to claim 1 , wherein the esterification reaction vessel is operated at a temperature in the range 90 to 150° C.

6. A process according to claim 1 , wherein in step 1, primary reflux is provided by condensing an overhead fraction of the distillation column in a condenser and returning a portion of the condensate to the distillation column, wherein the ratio of reflux flow rate to distillate flow rate is in the range of from 1:2 to 10:1.

7. A process according to claim 1 , wherein in step 1, the entrainer is selected from toluene, diisobutyl ether, n-butyl acetate, iso-butyl acetate, methyl ethyl ketone, and mixtures thereof.

8. A process according to claim 7 , wherein the entrainer is n-butyl acetate.

9. A process according to claim 8 , wherein the n-butyl acetate is formed “in-situ” by incorporating n-butanol in the reaction mixture in the esterification reaction vessel.

10. A process according to claim 1 , wherein all of the methanol in step 1 is provided by the lower boiling product stream that is recycled in step 7.

11. A process according to claim 1 , wherein in addition to the methanol which is provided by the lower boiling product stream that is recycled in step 7, fresh methanol is added to the esterification reaction vessel of step 1.

12. A process according to claim 1 , wherein the esterification catalyst in step 1 is a homogeneous catalyst selected from methane sulphonic acid and para-toluene sulphonic acid.

13. A process according to claim 1 , wherein the hydrogenation unit of step 2 comprises one or more adiabatic reactors.

14. A process according to claim 13 , wherein the hydrogenation unit of step 2 comprises two or more adiabatic reactors connected in series.

15. A process according to claim 14 , wherein all of the hydrogen is fed to the first adiabatic reactor and part of the overhead product fraction comprising methyl acetate, methanol and water form step 1 is fed to the first adiabatic reactor and the remaining part(s) of the overhead product fraction comprising methyl acetate, methanol and water is fed to the inlet of the second and/or subsequent adiabatic reactor together with the effluent of the previous adiabatic reactor in the hydrogenation unit.

16. A process according to claim 1 , wherein the hydrogenation unit of step 2 comprises at least one multitubular reactor.

17. A process according to claim 1 , wherein the separation of step 4 is performed in a flash separation unit.

18. A process according to claim 1 , wherein in step 5, at least 99 vol. % of the gaseous phase from step 4 is recycled to the hydrogenation unit of step 2.

19. A process according to claim 1 , wherein the lower boiling product stream of step 6 contains less than 0.5 mol % ethanol.

20. A process according to claim 1 , wherein the higher boiling product stream of step 6 contains less than 1.0 mol % methanol.

21. A process according to claim 1 , wherein the copper based hydrogenation catalyst in step 2 is a catalyst comprising copper oxide.

22. A process according to claim 1 , wherein the acetic acid has been prepared by the carbonylation of methanol.

23. A process according to claim 1 , wherein the molar ratio of acetic acid to methanol in the esterification reaction vessel of step 1 is within the range of 1:1.2 to 1:1.8.

Assignees

• Bp Plc

Inventors

• Bailey Craig
• Bolton Leslie William

Classifications

• Y02P20/582

  Recycling of unreacted starting or intermediate materials · CPC title

• Y02P20/52

  using catalysts, e.g. selective catalysts · CPC title

• C07C29/149 Primary

  with hydrogen or hydrogen-containing gases · CPC title

• C07C67/08

  by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds · CPC title

• C07C29/82

  by azeotropic distillation · CPC title