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AssigneeMitsubishi Gas Chemical Company, Inc.
InventorsAkio Hashimoto, Ryusuke Shigematsu, Kenichi Nakamura, Makoto Takagawa
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A process for producing a high-purity naphthalenedicarboxylic acid having an improved hue or an excellent hue from a crude naphthalenedicarboxylic acid obtained by the oxidation of dialkyl naphthalene, industrially advantageously at high yields, which comprises dissolving a crude naphthalenedicarboxylic acid obtained by the oxidation of dialkyl naphthalene in an aqueous solution containing an aliphatic amine, an alicyclic amine or acetonitrile, removing heavy metal components contained as impurities until the content of the heavy metal components based on the crude naphthalenedicarboxylic acid is 100 ppm or less, and heating the aqueous solution containing a naphthalenedicarboxylic acid amine salt to distill off the amine.
A process for the production of a high-purity naphthalenedicarboxylic acid, which comprises dissolving a crude naphthalenedicarboxylic acid obtained by the oxidation of dialkyl naphthalene in an aqueous solution containing an aliphatic or alicyclic amine, removing heavy metal components contained as impurities until the content of the heavy metal components based on the crude naphthalenedicarboxylic acid is 100 ppm or less, and heating the aqueous solution containing a naphthalenedicarboxylic acid amine salt to provide a high-purity naphthalenedicarboxylic acid by distilling off the amine.
A process for the production of a high-purity naphthalenedicarboxylic acid, which comprises dissolving a crude naphthalenedicarboxylic acid obtained by the oxidation of dialkyl naphthalene in an aqueous solution containing an aliphatic or alicyclic amine, bringing the aqueous solution into contact with a metal belonging to the group VIII of the periodic table in an inert gas atmosphere, and heating the aqueous solution containing a naphthalenedicarboxylic acid amine salt to provide a high-purity naphthalenedicarboxylic acid by distilling off the amine.
A process for the production of a high-purity naphthalenedicarboxylic acid, which comprises dissolving a crude naphthalenedicarboxylic acid obtained by the oxidation of dialkyl naphthalene in an aqueous solution containing an aliphatic amine, an alicyclic amine or an acetonitrile, precipitating a crystal of a naphthalenedicarboxylic acid amine salt by crystallization in mixed solvents of water with an aliphatic ketone, an alicyclic ketone or an acetonitrile, and heating the naphthalenedicarboxylic acid amine salt to provide a high-purity naphthalenedicarboxylic acid by distilling off the amine.
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