Process for extracting aromatic dicarboxylic acids from their metal salts
AssigneeRittec Umwelttechnik GmbH
InventorsClemens Müller, Esther Brepohl, Lars Biermann, Carsten Eichert, Stephan Scholl
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Abstract
The present invention relates to a process for extracting aromatic dicarboxylic acids from an outlet stream of a basic depolymerization of polycondensates containing metal carboxy lates of the aromatic dicarboxylic acid to be extracted, wherein a mineral or organic acid is added to this outlet stream, the pKs value of which acid being greater than or equal to that of the aromatic dicarboxylic acid, on which the polycondensate is based.
Claims12
A method for producing isophthalic acid and terephthalic acid from an effluent of a basic depolymerization reaction of polycondensates comprising metal carboxylates of isophthalic acid and of terephthalic acid, comprising the steps of:
- a) dissolving the metal carboxylates of isophthalic acid and terephthalic acid in the effluent;
- and
- b) carrying out a reactive precipitation by adding a mineral and/or organic acid to the effluent, wherein the added mineral acid or organic acid has at least a pKA value that is greater than or equal to the pKA values of the terephthalic acid, wherein the reactive precipitation is carried out at a temperature between 50° C. and 200° C., and wherein the mineral and/or organic acid is added in an amount corresponding to a stoichiometry factor of 1.33 to 3.6 based on the total present substance amount of isophthalic acid and terephthalic acid in the effluent, to receive a precipitated mixture of terephthalic acid and isophthalic acid, and wherein the precipitated mixture has an isophthalic acid content that is reduced by 44% to 87% by weight compared to the isophthalic acid content of the mixture of the effluent.
Dependencies are inferred from the claim text.