Process for the preparation of terephthalic acid
AssigneeChemische Werke Witten GmbH
InventorEwald Katzschmann
Life of this patent
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Abstract
An after-treatment or purification process for oxidation products produced by the air oxidation of a mixture of p-toluic acid methyl ester and p-xylene to provide terephthalic acid wherein the oxidation products are heated to an elevated temperature under pressure and a substance such as p-xylene, water, a lower carboxylic acid containing from 1 - 4 carbon atoms and mixtures thereof is added thereto. Subsequently, the desired terephthalic acid is separated from the resultant reaction mixture.
Claims16
An after-treatment process for oxidation products, that are obtained by the air oxidation of a mixture of p-toluic acid methyl ester in excess and p-xylene and that contain p-toluic acid methyl ester, p-toluic acid, terephthalic acid monomethyl ester and terephthalic acid, to isolate pure terphthalic acid which comprises heating said oxidation products to an elevated temperature and under pressure and adding a substance selected from the group consisting of water, a mixture of p-xylene and water, and a mixture of acetic acid and water and separating the pure terephthalic acid from the reaction mixture.
An after-treatment process for oxidation products, that are obtained by the air oxidation of a mixture of p-toluic acid methyl ester in excess and p-xylene and that contain p-toluic acid methyl ester, p-toluic acid, terephthalic acid monomethyl ester and terephthalic acid, to isolate pure terephthalic acid which comprises heating said oxidation products to an elevated temperature of between about 210.degree. and 280.degree.C. and under pressure and adding a substance selected from the group consisting of water, a mixture of p-xylene and water, and a mixture of acetic acid and water, the period of time of said after-treatment process ranging from between the necessary heating up time and five hours, and separating the pure terephthalic acid from the reaction mixture.
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