Purifying synthetic water-soluble carboxylic acids

Claim 1

IN A PROCESS FOR OBTAINING SUBSTANTIALLY PURE DRY WATER-SOLUBLE CARBOXYLIC ACIDS, WHICH FORM MINIMUM BOILIN AZEOTROPES WITH WATER, FROM DULUTE AQUEOUS SOLUTIONS THEREOF, SAID ACIDS HAVING BEEN PRODUCED BY SYNTHESIS FROM HYDROGEN AND CARBON MONOXIDE AND CONTAINING WATERSOLUBLE ORGANIC OXYGENATED IMPURITIES SIMULTANEOUSLY PRODUCED WITH SAID ACIDS, INCLUDING WATER-SOLUBLE ESTERS AND CARBONYL COMPOUNDS WHICH BOIL NEAR THE BOILING POINTS OF SAID ACIDS OR FORM AZEOTROPES WITH AT LEAST SOME OF SAID ACIDS IN THE ABSENCE OF WATER, WHEREIN A DILUTE AQUEOUS MIXTURE OF SAID ACIDS AND IMPURITIES IS FIRST SUBJECTED TO EXTRACTION WITH A SUBSTANTIALLY WATER-IMMISCIBLE SOLVENT FOR SAID ACIDS, AND THE LATTER, TOGETHER WITH SAID IMPURITIES, SEPARATED IN SUBSTANTIALLY ANHYDROUS FORM FROM THE RESULTING EXTRACT TO OBTAIN SAID ACIDS IN AL SUBSTANTIALLY ANHYDROUS FRACTION CONTAINING SAID IMPURITIES, THE STEPS WHICH COMPRISES ADDING ONLY SUFFICIENT WATER TO SAID FRACTION TO FORM MINIMUM BOILING AZEOTROPES WITH SAID IMPURITIES, AND THERAFTER SUBJECTING THE RESULTING MIXTURE TO DISTILLATION AT A TEMPERATURE BELOW THE BOILING POINT OF SAID FIRSTMENTIONED MINIMUM BOILING AZEOTROPES UNTIL SAID FRACTION IS SUFFICIENTLY FREE OF SAID IMPURITIES TO PASS STANDARD ACID TURBIDITY TESTS.