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US 7,405,322 B2Granted
Manufacture of oxalic acid dihydrate
AssigneeE.I. du Pont de Nemours and Company
InventorsJoseph J. Zaher, Bryan C. Fritzler, Scott N. Hutchison
Life of this patent
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Abstract
A process for the manufacture of oxalic acid dihydrate in which an aqueous solution of sodium oxalate is contacted with hydrochloric acid and the resulting mixture then cooled to precipitate oxalic acid, followed by optional recovery and recycling of the sodium oxalate and hydrochloric acid into the reaction chamber.
Claims27
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.
4 more elements
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 molar ratio of the water to the sodium oxalate is between about 35 to 1 and about 350 to 1 and the molar ratio of the hydrochloric acid to the sodium oxalate is greater than about 2 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.
4 more elements
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 molar ratio of the hydrochloric acid to the sodium oxalate is greater than about 2 to 1 and less than about 45 to 1, and the concentration of hydrochloric acid in the aqueous solution of hydrochloric acid is no greater than about 18 wt %;
- 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.
4 more elements
Dependencies are inferred from the claim text.