Patent ID: 7405322
Filing Date: 2008-07-29
Classification: C07C,Y02P

Abstract:
1. A process comprising: a) contacting an aqueous solution of hydrochloric acid with sodium oxalate in a reaction zone at a temperature between about 35° C. and about 140° C. to form a mixture wherein the solids are dissolved, wherein the molar ratio of the water to the sodium oxalate is between about 20 to 1 and about 350 to 1 and the molar ratio of the hydrochloric acid to the sodium oxalate is greater than about 3 to 1 and less than about 45 to 1; b) cooling the mixture to a temperature between about −10° C. and about 25° C. to form precipitated oxalic acid dihydrate in a slurry; c) separating the precipitated oxalic acid dihydrate from the slurry, thereby leaving a first residual solution; d) separating hydrochloric acid from the first residual solution, thereby leaving a second residual solution; and e) recycling the hydrochloric acid separated in step (d) to the reaction zone.