Integrated process for the production of 2, 6-naphthalene dicarboxylic acid

An integrated process:

• for producing 2,6-naphthalene dicarboxylic acid using methylnaphthalene as the feedstock which comprises:
• a) Reacting a hydrocarbon stream containing predominantly methylnaphthalene with an oxygen-containing gas in the presence of a suitable solvent and an oxidation catalyst to form a crude product mixture of naphthoic acid, wherein said crude product naphthoic acid remains dissolved in the solvent;
• b) Recovering said crude product midxture of isomers by evaporation of solvent and washing said crude product naphthoic acid with water;
• c) Debrominating said crude product naphthoic acid (NA) by passing over a supported catalyst selected from Group VIII in the presence of hydrogen, and water washing said crude debrominated product naphthoic acid;
• d) Contacting said crude, debrominated product naphthoic acid with an aqueous basic potassium salt to extract pure naphthoic acid as the aqueous potassium salt of naphthoic acid;
• e) Separating said aqueous potassium salt of naphthoic acid from the remaining. organic liquid and recycling said organic liquid to step a);
• f) Contacting said aqueous potassium salt of naphthoic acid with naphthalene vapor, adding a solid disproportionation catalyst, and removing water by evaporation to form a slurry of solid potassium salt of naphthoic acid and. catalyst suspended in liquid naphthalene;
• g) Reacting said slurry in the presence of carbon dioxide to convert said solid potassium salt of naphthoic acid to liquid naphthalene and solid dipotassium salt of 2,6-naphthalene dicarboxylic acid;
• h) Reducing the pressure to vaporize the naphthalene, separating the solids from the naphthalene vapor, recycling a portion of the naphthalene to step f), and recovering the remainder as a product, or methylating the naphthalene via direct alktylation or transalkylation to provide additional methylnaphthalene feed for step a);
• i) Contacting the solids with water to create a mixture of aqueous potassium salts comprising the potassium salt of naphthoic acid and the dipotassium salts of 2,6-naphthalene dicarboxylic acid and its isomers and solid catalyst;
• j) Separating the solid catalyst from the mixture of aqueous potassium salts and recycling said catalyst to step f);
• k) 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, separating said solid, and recycling the remaining liquid to step d);
• l) Dissolving said dipotassium salt of 2,6-naphthalene dicarboxylic acid in water;
• m) Optionally passing said aqueous dipotassium salt of 2,6-naphthalene dicarboxylic acid through an activated carbon bed to remove impurities;
• n) Contacting said aqueous dipotassium salt of 2,6-naphthalene dicarboxylic acid with carbon dioxide to create a mixture precipitated solid monopotassium salt of 2,6-naphthalene dicarboxylic acid and aqueous potassium bicarbonate, separating said solids, and recycling the aqueous potassium bicarbonate to step k);
• o) Contacting the solid monopotassium salt of 2,6-naphthalene dicarboxylic acid 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;
• p) Separating the solid 2,6-naphthalene dicarboxylic acid and recycling the liquid containing aqueous dipotassium salt of 2,6-naphthalene dicarboxylic acid and potassium bicarbonate to step n);
• q) Contacting solid 2,6-naphthalene dicarboxylic acid with water in a pipe reactor to remove traces of potassium ion impurity;
• r) Separating solid 2,6-naphthalene dicarboxylic acid and recycling water to step o);
• s) Washing the solid 2,6-naphthalene dicarboxylic acid with water;
• t) Separating the water from the solid, producing wet polymer grade 2,6-naphthalene dicarboxylic acid, and recycling most of the water to step q);
• u) Drying solid 2,6-naphthalene dicarboxylic acid by conventional means, or optionally feeding as an aqueous slurry to a process for making polyethylene naphthalate, optionally adding additional water if necessary.