Chlorine dioxide generation from chloric acid
AssigneeTenneco Canada Inc.
InventorsMarek Lipsztajn, Maurice C. J. Fredette, Zbigniew Twardowski
Life of this patent
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Abstract
Chlorine dioxide, useful as a pulp mill chemical, is produced without producing sodium sulfate effluent for disposal, by effecting reduction of chloric acid in an aqueous reaction medium in a reaction zone at a total acid normality of up to about 7 normal in the substantial absence of sulfate ion and in the presence of a dead load of sodium chlorate added to and subsequently removed from the reaction medium. Chloric acid for the process is produced electrolytically from an aqueous solution of the deadload sodium chlorate and make-up quantities of sodium chlorate. The chloric acid reduction to produce chlorine dioxide may be effected using methanol or electrolytically.
Claims46
A continuous method for the production of chlorine dioxide, which comprises:
- forming an aqueous acid reaction medium in a chlorine dioxide generation zone,
- effecting reduction of chloric acid to form chlorine dioxide in said aqueous acid reaction medium having a total acid normality of up to about 7 normal in the substantial absence of sulfate ions and in the presence of a sufficient dead load of sodium chlorate to permit said chlorine dioxide formation to be effected,
- removing said dead load sodium chlorate from said chlorine dioxide generation zone,
- forwarding said removed dead load sodium chlorate to an electrolysis zone in which a sodium chlorate feed solution, which includes said removed dead load sodium chlorate and added sodium chlorate to make up for chloric acid consumed in said reduction, is electrochemically acidified to produce an acidified solution while sodium ions are electrochemically removed from the said sodium chlorate feed solution, and
- forwarding said acidified solution containing chloric acid and said dead load sodium chlorate to said chlorine dioxide generation zone to provide a feed of chloric acid and dead load sodium chlorate to said aqueous acid reaction medium, whereby said dead load of sodium chlorate is added to and subsequently removed from said aqueous acid reaction medium.
A method for the production of chlorine dioxide, which comprises:
- feeding chloric acid and an aqueous solution of sodium chlorate to an aqueous acid reaction medium in a reaction zone having a total acid normality of from about 0.1 to about 6 normal and a concentration of sodium chlorate of from about 6 to about 9 molar,
- maintaining said aqueous reaction medium at its boiling point at a temperature of at least about 50.degree. C. up to the temperature of spontaneous decomposition of chlorine dioxide under a subatmospheric pressure of about 50 to about 400 mm Hg applied to the reaction zone,
- generating chlorine dioxide from said aqueous acid reaction medium by reduction of chlorate ions with methanol at said total acid normality of from about 0.1 to about 6 normal maintained by said feed of chloric acid and said concentration of sodium chlorate of from about 6 to about 9 molar maintained by said feed of aqueous solution of sodium chlorate,
- removing chlorine dioxide in admixture with steam from said reaction zone, and
- removing sodium chlorate from said reaction zone in a quantity corresponding to that fed to said reaction zone in said aqueous sodium chlorate solution, whereby said chlorine dioxide generation is effected in the presence of a dead load of sodium chlorate fed to and subsequently removed from said reaction zone.
An electrochemical process for the production of chlorine dioxide, which comprises:
- feeding chloric acid and an aqueous solution of sodium chlorate to an aqueous acid solution in an electrolytic zone having a total acid normality of less than about 7 and a concentration of sodium chlorate of at least about 2 molar,
- passing a cathodic electrical current through said aqueous acid solution of a magnitude sufficient to effect chlorine dioxide generation from said aqueous acid solution in said electrolysis zone, employing an electroconductive cathode which is chemically inert to the production of chlorine dioxide from said aqueous acid solution,
- maintaining said total acid normality of less than about 7 normal and said concentration of sodium chlorate of at least about 2 molar in said aqueous acid solution by said feeds of chloric acid and aqueous sodium chlorate solution respectively,
- removing chlorine dioxide from said electrolysis zone while maintaining a dissolved concentration of chlorine dioxide in said aqueous acid solution, and
- removing sodium chlorate from said electrolysis zone in a quantity corresponding to that fed to said electrolysis zone in said aqueous sodium chlorate solution, whereby said chlorine dioxide generation is effected int he presence of a dead load of sodium chlorate fed to and subsequently removed from said electrolysis zone.
Dependencies are inferred from the claim text.