Method For Improving The Performance of Nickel Electrodes

Abstract

The invention relates to a method for improving the performance of nickel electrodes in alkali chloride electrolysis by adding water-soluble platinum compounds to the catolyte.

1 . A method for improving the performance of nickel electrodes that are used in a membrane sodium chloride electrolytic process comprising:
 (a) preparing a water-soluble or alkali-soluble platinum solution comprising:
 (i) a solvent and 
 (ii) a soluble platinum compound 
   and   (b) adding the solution to the catolyte   
       and thereby forming a coating on the nickel electrode. 
     
     
         2 . The method according to  claim 1 , wherein the platinum compound is a water-soluble salt or a complex acid. 
     
     
         3 . The method according to  claim 1 , wherein the platinum solution is hexachloroplatinic acid, or an alkali platinate, or a mixture thereof. 
     
     
         4 . The method according to  claim 1 , wherein the soluble platinum compound is Na 2 PtCl 6 , or Na 2 Pt(OH) 6 , or a mixture thereof. 
     
     
         5 . The method according to  claim 1 , wherein, after the addition of the platinum solution, the electrolytic voltage is varied in the range from 0V to 5V. 
     
     
         6 . The method according to  claim 4 , wherein, after the addition of the platinum solution, the electrolytic voltage is varied in the range from 0V to 5V. 
     
     
         7 . The method according to  claim 5 , wherein, after the addition of the platinum solution, the difference in the electrolytic voltage is from 0.5 to 500 mV. 
     
     
         8 . The method according to  claim 6 , wherein, after the addition of the platinum solution, the difference in the electrolytic voltage is from 0.5 to 500 mV. 
     
     
         9 . The method according to  claim 5 , wherein the voltage is varied by pulsing the voltage or by superimposing an alternating voltage on the electrolytic voltage, in the range from 0 to 5 V, and by a difference of from 0.5 to 500 mV. 
     
     
         10 . The method according to  claim 8 , wherein the voltage is varied by pulsing the voltage or by superimposing an alternating voltage on the electrolytic voltage, in the range from 0 to 5 V, and by a difference of from 0.5 to 500 mV. 
     
     
         11 . The method according to  claim 10 , which further comprises at least one additional water-soluble compound from Group VIII of the Periodic Table are added to the platinum solution. 
     
     
         12 . The method according to  claim 1 , which further comprises at least one additional water-soluble compound from selected from the group consisting of palladium, iridium, platinum, rhodium, osmium and ruthenium. 
     
     
         13 . The method according to  claim 11 , wherein, the additional water-soluble compound, based on the amount of platinum in the platinum compound, are present in a concentration of 1 wt. % to 50 wt. %. 
     
     
         14 . The method according to  claim 12 , wherein, the additional water-soluble compound, based on the amount of platinum in the platinum compound, are present in a concentration of 1 wt. % to 50 wt. %. 
     
     
         15 . The method according to  claim 1 , wherein the water soluble or alkali soluble platinum compound solution is metered at a rate of 0.001 g Pt/(h*m 2 ) to 1 g Pt/(h*m 2 ). 
     
     
         16 . The method according to  claim 14 , wherein the water soluble or alkali soluble platinum compound solution is metered at a rate of 0.001 g Pt/(h*m 2 ) to 1 g Pt/(h*m 2 ). 
     
     
         17 . The method according to  claim 15 , wherein the temperature at which the metering of the platinum solution is from 70° C. to 90° C. 
     
     
         18 . The method according to  claim 16 , wherein the temperature at which the metering of the platinum solution is from 70° C. to 90° C. 
     
     
         19 . The method according to  claim 15 , wherein the metering of the platinum solution occurs during electrolysis and under a current density between 0.1 to 10 kA/m 2 . 
     
     
         20 . The method according to  claim 18 , wherein the metering of the platinum solution occurs during electrolysis and under a current density between 0.1 to 10 kA/m 2 .