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US 4,773,974 AGranted
Production of hexavalent chromium for use in chlorate cells
AssigneeTenneco Canada Inc.
InventorLeszek M. Dobosz
Life of this patent
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Abstract
By-product hypochlorite from the electrolytic production of chlorates, notably sodium chlorate, is used to form hexavalent chromium for use in the electrolysis process by oxidation of trivalent chromium compounds by the hypochlorite. The hypochlorite may be the condensate produced by treatment of the chlorate cell by-product gas stream and/or present in the cell liquor.
Claims15
A process for the electrolytic production of a chlorate, which comprises:
- electrolyzing in a diaphragmless cell an aqueous solution of the corresponding chloride to an aqueous chlorate product stream in the presence of hexavalent chromium ions wherein at least one effluent from the electrolysis contains hypochlorite, and
- reacting hypochlorite in said at least one effluent with trivalent chromium ions in a basic solution to form hexavalent chromium ions for use in said electrolyzing step.
A process for the electrolytic production of sodium chlorate, which comprises:
- electroylzing in a diaphragmless cell an aqueous solution of sodium chloride using an electroconductive metal anode at an elevated temperature in the presence of hexavalent chromium ions to form an aqueous sodium chlorate product solution and a hydrogen off-gas stream also containing steam and chlorine gas,
- treating said hydrogen off-gas stream to provide an effluent hydrogen stram substantially free from contaminants and an aqueous condensate containing condensed steam, hypochlorite and dissolved chlorine, and
- reacting hypochlorite in said condensate with trivalent chromium ions in a basic solution to form hexavalent chromium ions for use in said electrolysis.
Dependencies are inferred from the claim text.