Methods for making chlorous acid and chlorine dioxide

Abstract

Chlorous acid is generated from a chlorite salt precursor, a chlorate salt precursor, or a combination of both by ion exchange. The ion exchange material facilitates the generation of chlorous acid by simultaneously removing unwanted cations from solution and adding hydrogen ion to solution. Chlorine dioxide is generated in a controlled manner from chlorous acid by catalysis. Chlorine dioxide can be generated either subsequent to the generation of chlorous acid or simultaneously with the generation of chlorous acid. For catalysis of chlorous acid to chlorine dioxide, the chlorous acid may be generated by ion exchange or in a conventional manner. Ion exchange materials are also used to purify the chlorous acid and chlorine dioxide solutions, without causing degradation of said solutions, to exchange undesirable ions in the chlorous acid and chlorine dioxide solutions with desirable ions, such as stabilizing ions, and to adjust the pH of chlorous acid and chlorine dioxide solutions.

1 . A process for producing halogen oxide, the process comprising: 
 feeding a dilute aqueous alkali metal halite solution into a cation exchange column, wherein the cation exchange column contains a cation exchange material;    contacting the dilute aqueous alkali metal halite solution with the cation exchange material to produce an effluent containing halous acid; and    feeding the effluent halous acid into contact with a catalytic material in a moist environment for a time sufficient to produce a halogen oxide.    
     
     
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         13 . A process for generating chlorous acid and chlorine dioxide which comprises contacting a chlorite salt precursor and an acid with a catalytic material in a moist environment for a time sufficient to form chlorous acid and chlorine dioxide together.  
     
     
         14 . The process as described in  claim 13  wherein said catalytic material is on said cation exchange material.  
     
     
         15 . The process as described in  claim 13  wherein said catalytic material is an ion exchange material.  
     
     
         16 . (canceled)  
     
     
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         25 . (canceled)  
     
     
         26 . (canceled)  
     
     
         27 . (canceled)  
     
     
         28 . A process for purifying a chlorous acid solution which comprises contacting said chlorous acid solution with an ion exchange material in a moist environment for a time sufficient to remove unwanted ions from said chlorous acid solution.  
     
     
         29 . The process as described in  claim 28  wherein said ion exchange material is mixed with an additive.  
     
     
         30 . A process for purifying a chlorine dioxide solution which comprises contacting said chlorine dioxide solution with an ion exchange material in a moist environment for a time sufficient to remove unwanted ions from said chlorine dioxide solution.  
     
     
         31 . The process as described in  claim 30  wherein said ion exchange material is mixed with an additive.  
     
     
         32 . A process for substituting desirable ions for undesirable ions in a chlorous acid solution which comprises contacting said chlorous acid solution with an ion exchange material containing said desirable ions in a moist environment for a time sufficient to substitute said desirable ions for said undesirable ions in said chlorous acid solution.  
     
     
         33 . The process as described in  claim 32  wherein said ion exchange material is mixed with an additive.  
     
     
         34 . The process as described in  claim 32  wherein said desirable ion is a stabilizing ion.  
     
     
         35 . A process for substituting desirable ions for undesirable ions in a chlorine dioxide solution which comprises contacting said chlorine dioxide solution with an ion exchange material containing said desirable ions in a moist environment for a time sufficient to substitute said desirable ions for said undesirable ions in said chlorine dioxide solution.  
     
     
         36 . The process as described in  claim 35  wherein said ion exchange material is mixed with an additive.  
     
     
         37 . The process as described in  claim 35  where said desirable ion is a stabilizing ion.  
     
     
         38 . A process for adjusting the pH of a chlorous acid solution which comprises contacting said chlorous acid solution with an ion exchange material in a moist environment for a time sufficient to adjust the pH of said chlorous acid solution.  
     
     
         39 . The process as described in  claim 38  wherein said ion exchange material is mixed with an additive.  
     
     
         40 . A process for adjusting the pH of a chlorine dioxide solution which comprises contacting said chlorine dioxide solution with an ion exchange material in a moist environment for a time sufficient to adjust the pH of said chlorine dioxide solution.  
     
     
         41 . The process as described in  claim 40  wherein said ion exchange material is mixed with an additive.  
     
     
         42 . The process of  claim 1  wherein said aqueous alkali metal halite comprises an aqueous solution of a chlorite salt.  
     
     
         43 . The process of  claim 1  wherein said cation exchange material is selected from the group consisting of weak acid cation resins and powders, strong acid cation exchange resins and powders, and cation selected membranes, or any combination of the foregoing.  
     
     
         44 . The process of  claim 1  wherein said halous acid effluent comprises an aqueous solution containing chlorous acid.  
     
     
         45 . The process of  claim 1 , wherein said catalytic material is selected from the group consisting of platinum, palladium, manganese dioxide, carbon and ion exchange material.  
     
     
         46 . The process of  claim 1 , wherein said halogen oxide produced is chlorine dioxide.  
     
     
         47 . A process for generating chlorine dioxide, the process comprising: 
 feeding a dilute aqueous chlorite salt solution into a cation exchange column, wherein the cation exchange column contains a strong cation exchange material;    contacting the dilute aqueous chlorite salt solution with the strong cation exchange material to produce an effluent containing chlorous acid; and    feeding the effluent chlorous acid into contact with a platinum catalyst in a moist environment for a time sufficient to produce chlorine dioxide.    
     
     
         48 . A process for generating chlorine dioxide, the process comprising: 
 feeding a dilute aqueous chlorate salt precursor solution and an acid into an anion exchange column, wherein the anion exchange column is in a reducing ionic form;    contacting the dilute aqueous chlorate salt precursor solution with the anion exchange material in a reducing ionic form to produce an effluent containing chlorous acid; and    feeding the effluent chlorous acid into contact with a palladium catalyst in a moist environment for a time sufficient to produce chlorine dioxide.