Process for catalytic hydrogenation of halonitroaromatics

Patent metadata

Field	Value
Publication number	US-10562841-B2
Application number	US-201615761986-A
Country	US
Kind code	B2
Filing date	Sep 30, 2016
Priority date	Oct 1, 2015
Publication date	Feb 18, 2020
Grant date	Feb 18, 2020

Abstract

The present invention generally relates to processes for the catalytic hydrogenation of halonitroaromatics. In particular, the present invention includes processes for the catalytic hydrogenation of halonitroaromatics such as 2,5-dicloronitrobenzene to 2,5-dichloroaniline over a platinum-containing catalyst. The present invention also relates to processes for producing 3,6-dichloro-2-methoxybenzoic acid.

First claim

What is claimed is:

1. A process for producing 2,5-dichloroaniline, the process comprising:
feeding hydrogen and a feed mixture comprising 2,5-dichloronitrobenzene and a solvent comprising water, alcohol, and/or an acid to a hydrogenation zone; and
reacting the 2,5-dichloronitrobenzene with hydrogen in the presence of a heterogeneous hydrogenation catalyst comprising platinum on a carbon support to produce a reaction product comprising 2,5-dichloroaniline,
wherein the hydrogenation catalyst has a platinum loading that is from about 0.1 wt. % to about 1.5 wt. % and has been calcined at a temperature of from about 500° C. to about 1000° C.

2. The process of claim 1 wherein the feed mixture is free of dehalogenation suppressors.

3. The process of claim 1 wherein the hydrogenation catalyst has a platinum loading that is from about 0.5 wt. % to about 1.5 wt. %.

4. The process of claim 1 wherein the hydrogenation catalyst is prepared by heating the carbon support having platinum thereon to a temperature of from about 700° C. to about 1000° C.

5. The process of claim 1 wherein the hydrogenation catalyst is prepared by heating the carbon support having platinum thereon to a temperature of from about 800° C. to about 950° C.

6. The process of claim 1 wherein the hydrogenation catalyst comprises unreduced platinum.

7. The process of claim 6 wherein the hydrogenation catalyst is prepared by depositing the platinum onto the carbon support without use of a reducing agent; and calcining the platinum on the carbon support.

8. The process of claim 1 wherein the carbon support is a particulate.

9. The process of claim 1 wherein the hydrogenation catalyst comprises platinum metal particles at the surface of the carbon support of a size up to 10 nm in their largest dimension and at least about 25% (number basis) of the platinum metal particles are from 2 nm to 10 nm in their largest dimension.

10. The process of claim 1 wherein the hydrogenation catalyst comprises platinum metal particles of a size up to 10 nm in their largest dimension and these particles are characterized as having an average particle size from about 2.5 to about 8 nm.

11. The process of claim 1 wherein the hydrogenation catalyst comprises platinum metal particles of a size up to 10 nm in their largest dimension and no more than about 50% (number basis) of the platinum metal particles are less than 2 nm in their largest dimension.

12. The process of claim 1 wherein the hydrogenation catalyst is essentially free of metal catalyst modifiers.

13. The process of claim 1 wherein the carbon support has a total Langmuir specific surface area that is from about 500 m 2 /g to about 3000 m 2 /g.

14. The process of claim 1 wherein the carbon support has a Langmuir micropore surface area that is from about 750 m 2 /g to about 2000 m 2 /g.

15. The process of claim 1 wherein the carbon support has an average pore diameter that is in the range of from about 0.5 nm to about 5 nm.

16. The process of claim 1 wherein the carbon support has a pore volume of at least about 0.3 ml/g.

17. The process of claim 1 wherein the carbon support of the hydrogenation catalyst comprises activated carbon.

18. The process of claim 1 wherein the hydrogenation catalyst that is introduced into the hydrogenation zone consists essentially of platinum on a carbon support.

19. The process of claim 1 wherein the hydrogenation catalyst is essentially free of alkali and alkali earth metals.

20. The process of claim 1 wherein the solvent comprises the acid.

21. The process of claim 20 wherein the acid comprises an organic acid selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, citric acid, and mixtures thereof.

22. The process of claim 1 wherein the solvent is from about 20 wt. % to about 95 wt. % of the feed mixture.

23. The process of claim 1 wherein the hydrogenation reaction is conducted at a temperature that is from about 20° C. to about 100° C.

24. The process of claim 1 wherein hydrogenation reaction is conducted under a partial pressure of hydrogen that is at least about 20 kPa.

25. The process of claim 1 wherein the feed mixture is free or essentially free of hydroxides or oxides of magnesium, cycloaliphatic amines, and acidic phosphorous compounds.

26. The process of claim 1 wherein the reaction product further comprises 2-chloroaniline and 3-chloroaniline.

27. The process of claim 26 wherein the mole ratio of 3-chloroaniline to 2-chloroaniline is no greater than about 6:1.

28. The process of claim 1 wherein the yield of 2,5-dichloroaniline is at least about 90%.

29. The process of claim 1 wherein the reaction product further comprises platinum and the process further comprises recovering platinum from the reaction product.

30. A process for preparing 3,6-dichloro-2-methoxybenzoic acid or salt or ester thereof, the process comprising:
producing 2,5-dichloroaniline according to claim 1 ;
diazotizing 2,5-dichloroaniline to provide 2,5-dichlorobenzenediazonium;
hydrolyzing 2,5-dichlorobenzenediazonium to form 2,5-dichlorophenol;
carboxylating 2,5-dichlorophenol to form 2-hydroxy-3,6-dichlorobenzoic acid;
methylating 2-hydroxy-3,6-dichlorobenzoic acid to form a methylation reaction product comprising 3,6-dichloro-2-methoxybenzoic acid salt and/or ester thereof; and
optionally saponifiying the methylation reaction product to form 3,6-dichloro-2-methoxybenzoic acid.

31. The process of claim 26 wherein the mole ratio of 3-chloroaniline to 2-chloroaniline is from about 1:1 to about 5:1.

32. The process of claim 26 wherein the loss of selectivity from 2,5-dichloroaniline to 2-chloroaniline and 3-chloroaniline is less than about 0.4 mol.%.

33. The process of claim 1 wherein the solvent comprises the alcohol.

34. The process of claim 33 wherein the alcohol is selected from the group consisting of methanol, ethanol, propanol, isopropanol, 1-butanol, 2-butanol, t-butanol, and mixtures thereof.

Assignees

• Monsanto Technology Llc

Inventors

• Ahn John H
• Wan Kam-To

Classifications

• C07C37/045

  by substitution of a group bound to the ring by nitrogen · CPC title

• C07C209/365 Primary

  by reduction with preservation of halogen-atoms in compounds containing nitro groups and halogen atoms bound to the same carbon skeleton · CPC title

• B01J21/18

  Carbon · CPC title

• B01J23/42

  Platinum · CPC title

• B01J23/89

  combined with noble metals · CPC title