Purification of aromatic carboxylic acids

Claim 1

A PROCESS FOR IMPROVING THE QUANTITY OF A CRUDE NORMALLY SOLID ACID SELECTED FROM THE GROUP CONSISTING OF BENZOIC, TOLUIC AND PHTHALIC ACIDS, SAID CRUDE ACID BEING CONTAMINATED WITH NON-ACIDIC IMPURITIES WHICH CONTAIN AT LEAST ONE OF THE ELEMENTS SELECTED FROM THE GROUP CONSISTING OF SULFUR, IRON, NECKEL AND CHROMIUM, WHICH PROCESS COMPRISES: (A) DISSOLVING SAID CRUDE ACID IN AN AQUEOUS MEDIUM CONSISTING ESSENTIALLY OF ABOUT 30 TO 95 PERCENT BY VOLUME OF WATER AND ABOUT 70 TO 5 PERCENT BY VOLUME OF A NITROGEN COMPOUND SELECTED FROM THE GROUP CONSISTING OF PYRIDINE AND ALKYL SUBSTITUTED PYRIDINES: (B) CONTACTING SAID SOLUTION WITH A SOLID ABSORBENT SELECTED FROM THE GROUP CONSISTING OF ACTIVATED CARBON, ALUMINA, SILICA AND SILICA-ALUMINA; (C) MECHANICALLY SEPARATING SAID ADSORBENT FROM SAID SOLUTION; (D) REGULATING THE COMPOSITION OF SAID SOLUTION SO THAT IT CONTAINS FROM ABOUT 30 TO 95 PERCENT BY VOLUME OF WATER; (E) DISTILLING THE LAST NAMED SOLUTION TO SEPARATE THEREFROM AS AN OVERHEAD FRACTION AN AZEOTROPIC MIXTURE CONTAINING WATER AND A MAJOR PROPORTION OF SAID NITROGEN COMPOUND AND THEREBY FORM AS A DISTILLATION RESIDUE AN AQUEOUS SLURRY CONTAINING CRYSTALS OF SAID ACID; AND (F) RECOVERING SAID ACID CRYSTALS FROM SAID AQUEOUS SLURRY.