Patent ID: 7439391

Claim:
A process for the purification of glycolic acid comprising: (a) providing a first aqueous feed stream comprising at least 60 weight % glycolic acid and at least 0.2 weight % of an undesirable impurity; (b) isolating high purity crystalline glycolic acid using a crystallization process characterized by a product yield of at least 80% and a plurality of cascaded crystallization loops, said process comprising a first crystallization loop and a second crystallization loop; said first crystallization loop comprising: (i) a first crystallizer; (ii) a first evaporator; (iii) a first solid/liquid separator; and (iv) a first wash solution; wherein the first crystallization loop produces a first purge, a first washed solid crystalline product and a first washed mother liquor; wherein said first wash liquid is an aqueous feed stream of glycolic acid; whereby the first purge from the first crystallization loop is less than 20% of the glycolic acid within said first aqueous feed stream; whereby said first washed solid crystalline product is dissolved with water forming a second aqueous feed stream comprising glycolic acid, said second aqueous feed stream fed into said second crystallization loop; said second crystallization loop comprising (v) a second crystallizer; (vi) a second evaporator; (vii) a second solid/liquid separator; and (viii) a second wash solution; wherein said second wash liquid is said second aqueous feed stream whereby the second crystallization loop produces a second purge, a second washed mother liquor, and a second washed crystalline product, wherein the second purge is recycled back into said first crystallization loop; whereby high purity crystalline glycolic acid is produced.