Process for separation of crude naphthalene dicarboxylic acid using reverse osmosis
AssigneeMossi & Ghisolfi Overseas S.A.
InventorsZaida Diaz, John B. Rodden
Life of this patent
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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.
Claims11
A process for purifying 2,6-naphthalene dicarboxylic acid comprising:
- a) dissolving a product remaining from the disproportionation of potassium naphthoate comprising a dipotassium salt of 2,6-naphthalene dicarboxylic acid in water to form an aqueous solution, removing any remaining disproportionation reaction medium, centrifuging the solution to separate disproportionation catalyst, and removing acid salts other than 2,6-naphthalene dicarboxylic acid by crystallization and/or carbon adsorption,
- b) Contacting said aqueous solution of the dipotassium salt of 2,6-naphthalene dicarboxylic acid with carbon dioxide to form as a precipitate a monopotassium salt of 2,6-naphthalene dicarboxylic acid and an aqueous solution containing a monopotassium salt of 2,3-naphthalene dicarboxylic acid, dipotassium salt of naphthalene dicarboxylic acid, and potassium bicarbonate;
- c) Separating said monopotassium salt of 2,6-naphthalene dicarboxylic acid as a solid from said solution containing the monopotassium salt of 2,3-naphthalene dicarboxylic acid, dipotassium salt of 2,6-naphthalene dicarboxylic acid and potassium bicarbonate;
- d) Disproportionating the monopotassium salt of 2,3-naphthalene dicarboxylic acid to form 2,6-naphthalene dicarboxylic acid and an aqueous solution containing the dipotassium salt of 2,6-naphthalene dicarboxylic acid, and potassium bicarbonate;
- e) Separating said 2,6-naphthalene dicarboxylic acid;
- f) Concentrating said aqueous solution containing 2,6-naphthalene dicarboxylic acid and potassium bicarbonate from step (d) by reverse osmosis;
- and
- g) Recycling concentrated 2,6-naphthalene dicarboxylic acid to step (b) and pure water to step (d).
A novel process for producing high purity 2,6-naphthalene dicarboxylic acid which comprises:
- a) Disproportionating potassium naphthoate to produce a disproportionation reactor effluent containing reaction medium and disproportionation reaction solids comprising isomers of the dipotassium salt of 2,6-NDA, unreacted feed, catalyst and trace coke,
- b) Removing naphthalene by flashing;
- c) Dissolving said reaction solids in water;
- d) Separating any residual solvent and the solid catalyst from the reaction mixture;
- e) 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 2,6-naphthalene dicarboxylic acid as a solid and separating said solid;
- f) Removing acid salts other than the salts of 2,6-NDA by crystallization and, optionally, carbon adsorption;
- g) Dissolving said dipotassium salt of 2,6-naphthalene dicarboxylic acid in water;
- h) Contacting said aqueous dipotassium salt of 2,6-naphthalene dicarboxylic acid with carbon dioxide to create a mixture of solid monopotassium salt of 2,6-naphthalene dicarboxylic acid and aqueous potassium bicarbonate, and separating said solids from the aqueous solution;
- i) Contacting solid monopotassium salt of 2,6-NDA with water, optionally in the presence of carbon dioxide, to form solid 2,6-naphthalene dicarboxylic acid, aqueous dipotassium salt of 2,6-naphthalene dicarboxylic acid, and potassium bicarbonate;
- j) Separating the solid 2,6-naphthalene dicarboxylic acid;
- k) Concentrating said aqueous solution by reverse osmosis and recycling to the crystallization step (e).
Dependencies are inferred from the claim text.