Process for preparing purified 2,6-naphthalenedicarboxylic acid

A composition comprising 2,6-naphthalenedicarboxylic acid and a glycol wherein the 2,6-naphthalenedicarboxylic acid has an average particle size of at least 100 microns and wherein less than about 5 percent of the particles have a particle size under 11 microns.

The 2,6-naphthalenedicarboxylic acid made by the process comprising hydrolyzing a dialkyl-2,6-naphthalenedicarboxylate with water at a reaction temperature of at least about 570.degree. F. under liquid phase conditions and for a time sufficient to convert a major portion of the dialkyl-2,6-naphthalenedicarboxylate to 2,6-naphthalenedicarboxylic acid thereby forming a reaction product mixture, the amount of water present being sufficient to solubilize, at the reaction temperature, substantially all of the 2,6-naphthalenedicarboxylic acid formed;

• and recovering 2,6-naphthalenedicarboxylic acid from the reaction product mixture.

The composition consisting essentially of 2,6-naphthalenedicarboxylic acid and ethylene glycol having a Brookfield viscosity of no more than about 1000 centipoise and a mole ratio of ethylene glycol to 2,6-naphthalenedicarboxylic acid of no more than about 4:1, respectively.

A process for preparing 2,6-naphthalenedicarboxylic acid having improved purity comprising a) oxidizing a 2,6-dialkyl or 2-acyl-6-alkyl substituted naphthalene compound in the liquid phase in the presence of a low molecular weight aliphatic carboxylic acid, a molecular oxygen containing gas and a heavy metal oxidation catalyst to form a reaction mixture comprising impure 2,6-naphthalenedicarboxylic acid, b) separating the impure 2,6-naphthalenedicarboxylic acid from the reaction mixture, c) heating the separated impure 2,6-naphthalenedicarboxylic acid in the presence of a purification solvent under liquid phase conditions and at a temperature of at least about 500.degree. F. and thereafter d) recovering a purified 2,6-naphthalenedicarboxylic acid.

The purified 2,6-naphthalenedicarboxylic acid made by the process comprising (a) combining impure 2,6-naphthalenedicarboxylic acid with a purification solvent, (b) heating the resulting mixture under liquid phase conditions at a temperature of at least about 500.degree. F. to form a product mixture, and thereafter (c) recovering from the product mixture purified 2,6-naphthalenedicarboxylic acid, wherein the purification solvent is selected from the group consisting of water, a low molecular weight carboxylic acid and mixtures thereof, and having an average particle size of at least about 100 microns.

A process for purifying 2,6-naphthalenedicarboxylic acid comprising (a) combining impure 2,6-naphthalenedicarboxylic acid with a purification solvent, (b) heating the resulting mixture under liquid phase conditions at a temperature of at least about 500.degree. F. to form a product mixture, and thereafter (c) recovering from the product mixture purified 2,6-naphthalenedicarboxylic acid, wherein the purification solvent is selected from the group consisting of water, a low molecular weight carboxylic acid and mixtures thereof, and wherein the recovering step (c) comprises separating the 2,6-naphthalenedicarboxylic acid from the product mixture at temperatures of about 20.degree. F. to about 400.degree. F. below the temperature used to form the product mixture.