Processes for preparing 2,5-dichlorophenol

1. A process for producing 2,5-dichlorophenol, the process comprising:

contacting a feed comprising 2,4-dichlorophenol with a desilicated zeolite catalyst in acid form in an isomerization zone to isomerize at least a portion of the 2,4-dichlorophenol to 2,5-dichlorophenol, wherein the desilicated zeolite catalyst has a meso-macro pore volume (attributable to pores that have diameters greater than 20 Å up to 2500 Å) that is at least about 50% greater than the meso-macro pore volume of the initial zeolite catalyst before desilication; or

contacting a feed comprising 2,4-dichlorophenol with a zeolite catalyst in acid form in an isomerization zone to isomerize at least a portion of the 2,4-dichlorophenol to 2,5-dichlorophenol, wherein the zeolite catalyst has a meso-macro pore volume that is at least about 0.15 cm 3 /g.

2. The process of claim 1 wherein the zeolite catalyst has a SiO 2 /Al 2 O 3 mole ratio of from about 23:1 to about 80:1.

3. The process of claim 1 wherein the zeolite catalyst comprises a HZSM-5 zeolite.

4. The process of claim 1 further comprising feeding water to the isomerization zone.

5. The process of claim 1 wherein the feed comprising 2,4-dichlorophenol is contacted with the desilicated zeolite catalyst in acid form and the desilicated zeolite catalyst has a meso-macro pore volume (attributable to pores that have diameters greater than 20 Å up to 2500 Å) from about 50% to about 500% greater than the meso-macro pore volume of the initial zeolite catalyst before desilication.

6. The process of claim 1 wherein the feed comprising 2,4-dichlorophenol is contacted with the zeolite catalyst in acid form having a meso-macro pore volume (attributable to pores that have diameters greater than 20 Å up to 2500 Å) of at least about 0.15 cm 3 /g and the meso-macro pore volume of the zeolite catalyst is from about 0.15 cm 3 /g to about 0.3 cm 3 /g.

7. A process for producing 3,6-dichloro-2-methoxybenzoic acid comprising:

contacting a feed comprising 2,4-dichlorophenol with a zeolite catalyst in acid form in an isomerization zone to isomerize at least a portion of the 2,4-dichlorophenol to 2,5-dichlorophenol, wherein the zeolite catalyst has a SiO 2 /Al 2 O 3 mole ratio of no greater than about 35:1;

carboxylating at least a portion of the 2,5-dichlorophenol to produce 2-hydroxy-3,6-dichlorobenzoic acid; and

methylating the 2-hydroxy-3,6-dichlorobenzoic acid to 3,6-dichloro-2-methoxybenzoic acid.

8. The process of claim 7 wherein the zeolite catalyst comprises at least one alumino-silicate zeolite selected from the group consisting of ZSM zeolites, Beta zeolites, Y zeolites, and mixtures thereof.

9. The process of claim 1 further comprising:

carboxylating at least a portion of the 2,5-dichlorophenol to produce 2-hydroxy-3,6-dichlorobenzoic acid; and

methylating the 2-hydroxy-3,6-dichlorobenzoic acid to 3,6-dichloro-2-methoxybenzoic acid.

10. A process for producing 2,5-dichlorophenol, the process comprising:

hydroxylating 1,4-dichlorobenzene with an oxidizing agent in the presence of a first zeolite catalyst in a hydroxylation zone to form a hydroxylation reaction product comprising 2,5-dichlorophenol and 2,4-dichlorophenol;

separating at least a portion of the 2,4-dichlorophenol from the hydroxylation reaction product to form a fraction comprising 2,4-dichlorophenol; and

contacting the fraction comprising 2,4-dichlorophenol with a second zeolite catalyst in acid form in an isomerization zone to isomerize at least a portion of the 2,4-dichlorophenol to 2,5-dichlorophenol.

11. The process of claim 10 wherein the oxidizing agent comprises nitrous oxide.

12. The process of claim 10 wherein the first zeolite catalyst comprises an iron-promoted alumino-silicate zeolite.

13. The process of claim 12 wherein the iron loading of the iron-promoted zeolite is in the range of from about 0.01 wt. % to about 2 wt. % of the total catalyst weight.

14. The process of claim 10 wherein the first zeolite catalyst has a SiO 2 /Al 2 O 3 mole ratio that is in the range of from about 20:1 to about 1000:1.

15. The process of claim 10 wherein a feed gas comprising the 1,4-dichlorobenzene is contacted with the first zeolite catalyst in the hydroxylation zone at a temperature in the range of from about 250° C. to about 550° C.

16. The process of any one of claim 10 further comprising:

carboxylating at least a portion of the 2,5-dichlorophenol to produce 2-hydroxy-3,6-dichlorobenzoic acid; and

methylating the 2-hydroxy-3,6-dichlorobenzoic acid to 3,6-dichloro-2-methoxybenzoic acid.

17. The process of claim 7 wherein the SiO 2 /Al 2 O 3 mole ratio is from about 23:1 to about 35:1.

18. The process of claim 7 wherein the zeolite catalyst comprises a HZSM-5 zeolite, a HZSM-11 zeolite, or a mixture thereof.

19. The process of claim 7 further comprising feeding water to the isomerization zone.

20. The process of claim 7 wherein the isomerization is conducted at a catalyst temperature of from about 280° C. to about 325° C.

21. The process of claim 7 wherein the feed comprises a feed gas comprising 2,4-dichlorophenol and the partial pressure of 2,4-dichlorophenol in the feed gas is from about 0.05 kPa to about 10 kPa.

22. The process of claim 7 further comprising:

suspending contact of the feed comprising 2,4-dichlorophenol with the zeolite catalyst; and

contacting the zeolite catalyst with steam at a temperature from about 250° C. to about 375° C. to rejuvenate the catalyst.

23. A process for producing 2,5-dichlorophenol, the process comprising:

contacting a feed comprising 2,4-dichlorophenol and water with a zeolite catalyst in acid form in an isomerization zone to isomerize at least a portion of the 2,4-dichlorophenol to 2,5-dichlorophenol, wherein the water is fed continuously or intermittently to the isomerization zone as steam.

24. The process of claim 23 wherein the water is fed intermittently to the isomerization zone as steam.

25. The process of claim 23 wherein the water is fed continuously to the isomerization zone as steam.

26. The process of claim 23 wherein the zeolite catalyst comprises at least one alumino-silicate zeolite selected from the group consisting of ZSM zeolites, Beta zeolites, Y zeolites, and mixtures thereof.

27. The process of claim 23 wherein the zeolite catalyst comprises a ZSM zeolite.

28. The process of claim 23 wherein the zeolite catalyst comprises a HZSM-5 zeolite, a HZSM-11 zeolite or a mixture thereof.

29. The process of claim 23 wherein the isomerization is conducted at a catalyst temperature of from about 280° C. to about 325° C.

30. The process of any one of claim 23 further comprising:

carboxylating at least a portion of the 2,5-dichlorophenol to produce 2-hydroxy-3,6-dichlorobenzoic acid; and

methylating the 2-hydroxy-3,6-dichlorobenzoic acid to 3,6-dichloro-2-methoxybenzoic acid.

31. A process for producing 2,5-dichlorophenol, the process comprising:

contacting a feed comprising 2,4-dichlorophenol and water with a zeolite catalyst in acid form in an isomerization zone to isomerize at least a portion of the 2,4-dichlorophenol to 2,5-dichlorophenol, wherein the weight ratio of catalyst to water per hour is from about 150:1 to about 500:1.

32. The process of claim 31 wherein the zeolite catalyst comprises at least one alumino-silicate zeolite selected from the group consisting of ZSM zeolites, Beta zeolites, Y zeolites, and mixtures thereof.

33. The process of claim 31 wherein the zeolite catalyst comprises a ZSM zeolite.

34. The process of claim 31 wherein the zeolite catalyst comprises a HZSM-5 zeolite, a HZSM-11 zeolite or a mixture thereof.

35. The process of claim 31 wherein the isomerization is conducted at a catalyst temperature of from about 280° C. to about 325° C.

36. The process of any one of claim 31 further comprising:

carboxylating at least a portion of the 2,5-dichlorophenol to produce 2-hydroxy-3,6-dichlorobenzoic acid; and

methylating the 2-hydroxy-3,6-dichlorobenzoic acid to 3,6-dichloro-2-methoxybenzoic acid.

37. A process for producing 2,5-dichlorophenol, the process comprising:

contacting a feed comprising 2,4-dichlorophenol and water with a zeolite catalyst in acid form in an isomerization zone to isomerize at least a portion of the 2,4-dichlorophenol to 2,5-dichlorophenol, wherein the weight ratio of 2,4-dichlorophenol in the feed to water per hour is from about 5:1 to about 30:1.

38. The process of claim 37 wherein the zeolite catalyst comprises at least one alumino-silicate zeolite selected from the group consisting of ZSM zeolites, Beta zeolites, Y zeolites, and mixtures thereof.

39. The process of claim 37 wherein the zeolite catalyst comprises a ZSM zeolite.

40. The process of claim 37 wherein the zeolite catalyst comprises a HZSM-5 zeolite, a HZSM-11 zeolite or a mixture thereof.

41. The process of claim 37 wherein the isomerization is conducted at a catalyst temperature of from about 280° C. to about 325° C.

42. The process of any one of claim 37 further comprising:

carboxylating at least a portion of the 2,5-dichlorophenol to produce 2-hydroxy-3,6-dichlorobenzoic acid; and

methylating the 2-hydroxy-3,6-dichlorobenzoic acid to 3,6-dichloro-2-methoxybenzoic acid.