Method and apparatus for producing hydrogen peroxide

Abstract

An electrolytic cell generates hydrogen peroxide and includes a reservoir for storing hydrogen peroxide generated by the cell. A controller is arranged to activate the cell and introduce stored hydrogen peroxide from the reservoir to the cell. This permits the concentration of a store of hydrogen peroxide to be refreshed as required, by introducing the stored hydrogen peroxide as the electrolyte in the cell. This counteracts the natural decay of the stored hydrogen peroxide. The pH of the hydrogen peroxide is controlled so that it is below a predetermined value. It has been found that hydrogen peroxide having a low pH, close to neutral, decays much more slowly than hydrogen peroxide having a more strongly alkaline pH.

1 . An apparatus for producing hydrogen peroxide, comprising:
 an electrolytic cell arranged to generate hydrogen peroxide,   a reservoir for storing the hydrogen peroxide generated by the cell and   a controller arranged to activate the cell and introduce the stored hydrogen peroxide from the reservoir to the cell.   
     
     
         2 . The apparatus of  claim 1 , in which the controller is further arranged to monitor the length of time that the stored hydrogen peroxide has been stored in the reservoir, and to activate the electrolytic cell for a predetermined period in dependence on the length of time of storage. 
     
     
         3 . The apparatus of  claim 1 , further comprising a pump arranged to circulate hydrogen peroxide between the reservoir and the cell. 
     
     
         4 . The apparatus of  claim 1 , in which the controller is arranged to control the pH of the hydrogen peroxide produced by the cell to below a predetermined value. 
     
     
         5 . The apparatus of  claim 4 , in which the pH of the produced hydrogen peroxide is controlled by controlling the pH of an electrolyte in the cell to below a predetermined value. 
     
     
         6 . The apparatus of  claim 5 , in which the electrolyte is associated with an anode of the cell. 
     
     
         7 . The apparatus of  claim 5 , in which the electrolyte is stored in an airtight tank. 
     
     
         8 . The apparatus of  claim 5 , in which the electrolyte is replenished by adding water. 
     
     
         9 . The apparatus of  claim 8 , in which a an amount of added water is relatively small compared to the volume of the electrolyte. 
     
     
         10 . The apparatus of  claim 5 , in which the electrolyte is softened water. 
     
     
         11 . The apparatus of  claim 10 , in which the water is supplied from a local mains supply. 
     
     
         12 . The apparatus of  claim 5 , in which the electrolyte is a solution of sodium sulphate. 
     
     
         13 . (canceled) 
     
     
         14 . An appliance comprising the apparatus for producing hydrogen peroxide of  claim 1 . 
     
     
         15 . An automatic dishwasher comprising the apparatus for producing hydrogen peroxide of  claim 1 . 
     
     
         16 . The automatic dishwasher of  claim 15  configured to perform a pre-wash step for items placed in the dishwasher for washing, with the controller being configured to activate the cell and introduce hydrogen peroxide from the reservoir to the cell during the pre-wash step. 
     
     
         17 . The automatic dishwasher of  claim 15 , in which the hydrogen peroxide is applied to the items to be washed from the reservoir during a wash step. 
     
     
         18 . The automatic dishwasher of  claim 17 , in which, when the reservoir is emptied of hydrogen peroxide, the cell is activated to produce a store of hydrogen peroxide in the reservoir. 
     
     
         19 . A method of producing hydrogen peroxide, comprising:
 providing an electrolytic cell arranged to generate hydrogen peroxide, activating the cell and introducing stored hydrogen peroxide from a reservoir to the cell.   
     
     
         20 . A method of washing dishes comprising:
 providing an electrolytic cell arranged to generate hydrogen peroxide activating the cell,   introducing stored hydrogen peroxide from a reservoir to the cell and of applying the hydrogen peroxide to the dishes.   
     
     
         21 . The method of  claim 20 , in which the hydrogen peroxide is produced during a pre-wash step, in which water is applied to the dishes to be washed. 
     
     
         22 . The method of  claim 20 , in which hydrogen peroxide is applied from the reservoir to the dishes during a main wash step. 
     
     
         23 . The method of  claim 22 , in which, when the reservoir is emptied of hydrogen peroxide, the cell is activated to produce a store of hydrogen peroxide in the reservoir.