Claims
- 1. A process for producing a high purity aromatic polycarboxylic acid by purifying a crude aromatic polycarboxylic acid, comprising steps of:(I) forming a salt which comprises forming an amine salt of an aromatic polycarboxylic acid from the crude aromatic polycarboxylic acid and amine; (II) decomposing a salt which comprises simultaneously and continuously conducting in a salt decomposition reactor three operations of (i) supplying an aqueous solution of the amine salt of an aromatic polycarboxylic acid formed in the step of forming a salt, (ii) removing the amine and water by distillation under heating and (iii) taking out a slurry containing crystallized aromatic polycarboxylic acid in a condition, at steady state, that a concentration of crystals of the aromatic polycarboxylic acid is 5 to 50% by weight and that a fraction of decomposition of the amine salt of the carboxylic acid is 20 to 80%; and (III) separating crystals which comprises separating and recovering crystals of the aromatic polycarboxylic acid from the slurry which is taken out in the step of decomposing a salt, wherein at least a portion of a mother liquor, which is obtained after crystals of the aromatic polycarboxylic acid are separated in the step of separating crystals, is recycled to the step of decomposing a salt.
- 2. A process according to claim 1, wherein said at least a portion of said mother liquor is recycled directly to said step of decomposing a salt, from said step of separating crystals.
- 3. A process according to claim 1, wherein the amine and water are removed by distillation in the step of decomposing a salt at a temperature of 100 to 250° C.
- 4. A process according to claim 1, wherein at least a portion of the amine removed by distillation in the step of decomposing a salt is recycled to the step of forming a salt.
- 5. A process according to claim 1, wherein the aromatic polycarboxylic acid as a component of the amine salt of the polycarboxylic acid is a compound selected from naphthalenepolycarboxylic acids and biphenylpolycarboxylic acids.
- 6. A process according to claim 1, wherein the amine as a component of the amine salt of the polycarboxylic acid is at least one amine selected from aliphatic amines and alicyclic amines.
- 7. A process according to claim 1, wherein the amine as a component of the amine salt of the aromatic polycarboxylic acid is a compound selected from triethylamine and trimethylamine.
- 8. A process according to claim 1, wherein said concentration of crystals of the aromatic polycarboxylic acid in the slurry taken out from the salt decomposition reactor is 10 to 30% by weight.
Priority Claims (2)
Number |
Date |
Country |
Kind |
2000-154793 |
May 2000 |
JP |
|
2000-397491 |
Dec 2000 |
JP |
|
Parent Case Info
This application is a Divisional application of application Ser. No. 09/858,487, now U.S. Pat. No. 6,455,731 filed May 17, 2001, the contents of which are incorporated herein by reference in their entirety.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
6194609 |
Abrams et al. |
Feb 2001 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
787 712 |
Aug 1997 |
EP |