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Title:
A PROCESS FOR SEPARATION OF CRUDE NAPHTHALENE DICARBOXYLIC ACID USING REVERSE OSMOSIS
Document Type and Number:
WIPO Patent Application WO/2001/016067
Kind Code:
A2
Abstract:
Disclosed is a process for purifying 2,6-naphthalene dicarboxylic acid produced by disproportionation and more efficiently recycling byproduct dipotassium salts which includes the steps of: a) Contacting an aqueous solution containing the disalt of 2,6-NDA(2,6-K2NDA) with carbon dioxide to form as a precipitate the monopotassium salt of 2,6-NDA (KHNDA) and an aqueous solution containing 2,3-KHNDA, K2NDA, and potassium bicarbonate; b) Disproportionating said monopotassium salt (KHNDA) to form 2,6-NDA and an aqueous solution containing K2NDA, and potassium bicarbonate; c) Separating said 2,6-NDA and concentrating said aqueous solution containing K2NDA and potassium bicarbonate by reverse osmosis.

Inventors:
Diaz, Zaida (12106 Meadow Lake Houston, TX, 77077, US)
Rodden, John B. (4014 Hallmark Fair Court Houston, TX, 77059, US)
Application Number:
PCT/US2000/021674
Publication Date:
March 08, 2001
Filing Date:
August 08, 2000
Export Citation:
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Assignee:
MOSSI & GHISOLFI OVERSEAS S.A. (45-47 Boulevard de la Pétrusse Luxembourg, L-2320, LU)
International Classes:
C07C51/44; B01J27/232; C07C51/02; C07C51/15; C07C51/265; C07C51/41; C07C51/42; C07C51/43; C07C51/47; C07C51/48; C07C51/487; C07C63/38; C08G63/189; (IPC1-7): C07C51/00
Foreign References:
US3671578A1972-06-20
US3888921A1975-06-10
Other References:
DATABASE WPI Derwent Publications Ltd., London, GB; AN 1978-18376A XP002159814 & JP 53 007633 A (MITSUBISHI GOS CHEMICAL CO.; TOYO BOSEKI; MIZUSHIMA AROMA KK) 9 July 1976 (1976-07-09)
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Claims:
CLAIMS
1. A process for purifying 2,6naphthalene dicarboxylic acid produced by disproportionation and more efficiently recycling byproduct dipotassium salts which comprises: a) Dissolving a disproportionation product comprising the dipotassium salt of 2,6NDA (K2NDA) in water, removing any remaining disproportionation reaction medium, centrifuging the solution to separate disproportionation catalyst, and removing acid salts other than 2,6NDA by crystallization and/or carbon adsorption, b) Contacting said aqueous solution of 2,6K2NDA with carbon dioxide to form as a precipitate the monopotassium salt of 2,6NDA (KHNDA) and an aqueous solution containing 2,3KHNDA, K2NDA, and potassium bicarbonate; c) Separating said monopotassium salt as a solid from said stream containing 2,3KHNDA, K2NDA and potassium bicarbonate; d) Disproportionating said monopotassium salt (KHNDA) to form 2,6NDA and an aqueous solution containing K2NDA and potassium bicarbonate; e) Separating said 2,6NDA; f) Concentrating said aqueous solution containing K2NDA and potassium bicarbonate from step (d) by reverse osmosis; and g) Recycling concentrated K2NDA to step (b) and pure water to step (d).
2. The process of Claim l (f) wherein the aqueous solution is concentrated by reverse osmosis to a wt% of disalt of 10 30 wt% dipotassium naphthalene dicarboxylic acid.
3. The process of Claim 2 wherein the aqueous solution of step (f) is concentrated by reverse osmosis to about 20 wt% dipotassium naphthalene dicarboxylic acid.
4. The process of Claim 1 (f) wherein reverse osmosis is accomplished using thin film composite membranes.
5. The process of Claim 4 wherein the membrane further comprises three layers consisting of a support web, a microporous polysulfone interlayer with controlled pore diameters, and an ultrathin polyamide coating selective layer.
6. The process of Claim 5 wherein the selective layer is on the order of 0.2 microns and can withstand high pressures due to the support provided by the interlayer.
7. The process of Claim l (f) further comprising the reverse osmosis being carried out under a pressure in the range of 500 to 2000 psig.
8. The process of Claim l (f) further comprising the reverse osmosis being carried out in two stages.
9. The process of Claim 8 further comprising contacting the solution of dipotassium salts with a reverse osmosis membrane at a pressure of about 500900 psig for a period and then contacting the concentrate with a second reverse osmosis membrane at a pressure of about 16001800 psig for a period of time.
10. The process of Claim 9 further comprising contacting the solution of dipotassium salts with the first membrane a pressure below 900 psig until about 7080% of the water is recovered and then contacting the solution with the second membrane at a pressure below 1800 psig.
11. In any process for producing 2,6naphthalene dicarboxylic acid, the improvement of concentrating a solution of dipotassium salts by reverse osmosis.
12. A novel process for producing high purity 2,6 naphthalene dicarboxylic acid which comprises: h) Disproportionating potassium naphthoate to produce a disproportionation reactor effluent containing reaction medium and disproportionation reaction solids comprising isomers of the dipotassium salt of 2,6NDA, unreacted feed, catalyst and trace coke, i) Removing naphthalene by flashing; j) Dissolving said reaction solids in water; k) Separating any residual solvent and the solid catalyst from the reaction mixture; 1) Adding aqueous potassium bicarbonate to the mixture of aqueous potassium salts and evaporating a portion of the water to selectively crystallize the dipotassium salt of 2,6naphthalene dicarboxylic acid as a solid and separating said solid; m) Removing acid salts other than the salts of 2,6NDA by crystallization and, optionally, carbon adsorption; n) Dissolving said dipotassium salt of 2,6naphthalene dicarboxylic acid in water; o) Contacting said aqueous dipotassium salt of 2,6 naphthalene dicarboxylic acid with carbon dioxide to create a mixture of solid monopotassium salt of 2,6naphthalene dicarboxylic acid and aqueous potassium bicarbonate, and separating said solids from the aqueous solution; p) Contacting solid monopotassium salt of 2,6NDA with water, optionally in the presence of carbon dioxide, to form solid 2,6naphthalene dicarboxylic acid, aqueous dipotassium salt of 2,6naphthalene dicarboxylic acid, and potassium bicarbonate; q) Separating the solid 2,6naphthalene dicarboxylic acid; r) Concentrating said aqueous solution by reverse osmosis and recycling to the crystallization step (e).
Description:
INTERNATIONALSEARCH REPORT Int tional Application No PCT/US 00/21674 C. (Continuation) DOCUMENTS CONSIDERED TO BE RELEVANT Category ° Citation of document, with indication, where appropriate, ot the relevant passages Relevant to claim No. A DATABASE WPI 1 Derwent Publications Ltd., London, GB; AN 1978-18376A XP002159814 abstract &JP 53 007633 A (MITSUBISHI GOS CHEMICAL CO.; TOYO BOSEKI; MIZUSHIMA AROMA KK) 9 July 1976 (1976-07-09) INTERNATIONAL SEARCH REPORT zonal Application No Information on patent family members PCT/US 00/21674 Patent document Publication Patent family Publication cited in search report date member (s) date US 3671578 A 20-06-1972 NONE US 3888921 A 10-06-1975 NONE