Processes for preparing 2,5-dichlorophenol
Processes for producing 2,5-dichlorophenol and 3,6-dichloro-2-methoxybenzoic acid are described. Various processes for isomerizing 2,4-dichlorophenol over a zeolite catalyst to form 2,5-dichlorophenol are provided. Processes for preparing 2,5-dichlorophenol including hydroxylating 1,4-dichlorobenzene are also described. The present invention also relates to processes for producing 3,6-dichloro-2-methoxybenzoic acid.
1. A process for producing 2,5-dichlorophenol, the process 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.
2. The process of claim 1 wherein the SiO 2 /Al 2 O 3 mole ratio is from about 23:1 to about 35:1.
3. The process of claim 1 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.
4. The process of claim 1 wherein the zeolite catalyst comprises a HZ SM-5 zeolite, a HZ SM-11 zeolite, or a mixture thereof.
5. The process of claim 1 further comprising feeding water to the isomerization zone.
6. The process of claim 1 wherein the isomerization is conducted at a catalyst temperature of from about 220° C. to about 550° C.
7. The process of claim 1 wherein the zeolite catalyst is calcined at a temperature in the range of from about 500° C. to about 1000° C.
8. The process of claim 1 wherein the zeolite catalyst is selected from the group consisting of pentasil zeolites, Beta zeolites, and faujasite zeolites.
9. A process for producing 2,5-dichlorophenol, the process comprising:
contacting a feed comprising 2,4-dichlorophenol and 3,4-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.
10. The process of claim 9 wherein the zeolite catalyst comprises a HZ SM-5 zeolite, a HZ SM-11 zeolite, or a mixture thereof.
11. The process of claim 9 further comprising feeding water to the isomerization zone.
12. The process of claim 9 wherein the mole ratio of 2,4-dichlorophenol to 3,4-dichlorophenol in the feed is from about 10:1 to about 50:1.
13. The process of claim 9 wherein the zeolite catalyst comprises a desilicated zeolite catalyst.
14. The process of claim 13 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) from about 50% to about 500% greater than the meso-macro pore volume of the initial zeolite catalyst before desilication.
15. A process for producing 3,6-dichloro-2-methoxybenzoic acid comprising:
isomerizing 2,4-dichlorophenol to 2,5-dichlorophenol in accordance with the process of claim 9 ;
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.
16. The process of claim 9 wherein the zeolite catalyst is selected from the group consisting of pentasil zeolites, Beta zeolites, and faujasite zeolites.
17. A process for producing 2,5-dichlorophenol, the process 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;
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.
18. The process of claim 17 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.
19. The process of claim 17 wherein the zeolite catalyst comprises a HZ SM-5 zeolite, a HZ SM-11 zeolite, or a mixture thereof.
20. The process of claim 17 wherein the zeolite catalyst comprises a desilicated zeolite catalyst.
21. The process of claim 20 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) from about 50% to about 500% greater than the meso-macro pore volume of the initial zeolite catalyst before desilication.
22. A process for producing 3,6-dichloro-2-methoxybenzoic acid comprising:
isomerizing 2,4-dichlorophenol to 2,5-dichlorophenol in accordance with the process of claim 17 ;
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.
23. The process of claim 17 wherein the zeolite catalyst is selected from the group consisting of pentasil zeolites, Beta zeolites, and faujasite zeolites.