Process for the isolation of aromatic hydroxycarboxylic acids
AssigneeE. I. Du Pont de Nemours and Company
InventorsMichael Robert Samuels, Ronald M. Yabroff
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Abstract
Processes are provided for the electrodialysis of a (di)alkali metal salt of an aromatic hydroxycarboxylic acid to produce a free aromatic hydroxycarboxylic acid and the alkali metal hydroxide, in the presence of a selected alkali metal salt. These various embodiments represent efficient and economical methods for recovering the alkali metal hydroxide, as well as the parent organic compound, from these dialkali metal salts. These processes also desirably prevent overvoltage during the electrodialysis.
Claims12
A process for the preparation of an aromatic hydroxycarboxylic acid from its dialkali metal salt, comprising electrodialyzing an aqueous solution of a first compound of the formula (OR1CO2)HtM2−t, and a second compound of the formula MxHzQ, to produce a third compound of the formula (OR1CO2)HyM2−y and MOH, wherein:
- R1 is arylene;
- t is zero to about 1.90;
- each M is independently an alkali metal cation;
- HzQ is an anion whose conjugate acid has a pKa of about 2 or less;
- x is an integer of 1 or more, and z is 0 or an integer of 1 or more, provided that x+z is equal to the total number of negative charges on Q;
- M has a concentration associated with HzQ at a pH of 2.5 of about 0.03 to about 4 molar;
- and
- y is about 1.95 to 2.00.
Dependencies are inferred from the claim text.