Electrochemical conversion of anhydrous hydrogen halide to halogen gas using a membrane-electrode assembly or gas diffusion electrodes

Abstract

The present invention relates to an electrochemical cell and a process for converting anhydrous hydrogen halide to halogen gas using a membrane-electrode assembly (MEA) or a separate membrane and electrode arrangement, such as gas diffusion electrodes with a membrane.

What is claimed is:  
     
       1. A process for the direct production of essentially dry halogen gas from essentially anhydrous hydrogen halide, comprising the steps of: 
       (a) feeding molecules of essentially anhydrous hydrogen halide to an inlet of an electrochemical cell comprising a cation-transporting membrane, an anode disposed in contact with one side of the membrane and a cathode disposed in contact with the other side of the membrane; and  
       (b) applying a voltage to the anode and the cathode such that the anode is at a higher potential than the cathode, wherein the molecules of the essentially anhydrous hydrogen halide are transported to the anode, the molecules are oxidized at the anode to produce essentially dry halogen gas and protons, the protons are transported through the cation-transporting membrane of the electrochemical cell, and the transported protons are reduced at the cathode.  
     
     
       2. The process of claim  1 , wherein the anode and the cathode comprise particles of an electrochemically active material applied to the membrane. 
     
     
       3. The process of claim  1 , further including the step of supplying water to the cathode-side of the membrane through an inlet disposed at the cathode-side of the membrane. 
     
     
       4. The process of claim  3 , further including the step of distributing the water from the cathode-side inlet through flow channels formed in a cathode mass flow field disposed in contact with the cathode, and distributing hydrogen halide through flow channels formed in an anode mass flow field disposed in contact with the cathode, wherein the channels in the anode mass flow field and the channels in the cathode mass flow field are parallel to each other. 
     
     
       5. A process for the direct production of chlorine gas from anhydrous hydrogen chloride, comprising the steps of: 
       (a) supplying anhydrous hydrogen chloride to an inlet of an electrochemical cell comprising a cation-transporting membrane, an anode disposed in contact with one side of the membrane and a cathode disposed in contact with the other side of the membrane; and  
       (b) applying a voltage to the anode and the cathode such that the anode is at a higher potential than the cathode, wherein the hydrogen chloride is oxidized at the anode to produce chlorine gas and protons, the protons are transported through the cation-transporting membrane of the electrochemical cell, and the transported protons are reduced at the cathode.  
     
     
       6. The process of claim  5 , further including the step of supplying water to the cathode-side of the membrane through an inlet disposed at the cathode-side of the membrane. 
     
     
       7. The process of claim  6 , further including the step of distributing the water from the cathode-side inlet through flow channels formed in a cathode mass flow field disposed in contact with the cathode, and distributing hydrogen chloride through flow channels formed in an anode mass flow field disposed in contact with the cathode, wherein the channels in the anode mass flow field and the channels in the cathode mass flow field are parallel to each other. 
     
     
       8. The process of claims  5  or  7 , wherein the hydrogen chloride is anhydrous hydrogen chloride which is oxidized at the anode. 
     
     
       9. The process of claims  5  or  7 , wherein the voltage is in the range of 1.0 to 2.0 volts. 
     
     
       10. The process of claims  5  or  7 , wherein the current density is greater than about 5.38 kA/m 2  at a voltage of 1.8 to 2.0 volts. 
     
     
       11. The process of claim  10 , wherein the current density is in the range of 8-12 kA/m 2  at a voltage of 1.8 to 2.0 volts. 
     
     
       12. The process of claims  5  or  7 , wherein the temperature of the electrochemical cell is in the range of 40°-120° C. 
     
     
       13. The process of claim  12 , wherein the temperature of the electrochemical cell is in the range of 60°-90° C. 
     
     
       14. The process of claims  5  or  7 , wherein the pressure of the electrochemical cell is in the range of 30-110 psig. 
     
     
       15. The process of claim  14 , wherein the pressure of the electrochemical cell is in the range of 60-110 psig. 
     
     
       16. The process of claim  5  or  7 , wherein the anode and the cathode comprise particles of an electrochemically active material applied to the membrane. 
     
     
       17. The process of claims  1  or  16 , wherein the voltage is in the range of 1.0 to 2.0 volts. 
     
     
       18. The process of claims  1  or  16 , wherein the current density is greater than about 5.38 kA/m 2  at a voltage of 1.8 to 2.0 volts. 
     
     
       19. The process of claim  18 , wherein the current density is in the range of 8-12 kA/m 2  at a voltage of 1.8 to 2.0 volts. 
     
     
       20. The process of claims  1  or  16 , wherein the temperature of the electrochemical cell is in the range of 40°-120° C. 
     
     
       21. The process of claim  20 , wherein the temperature of the electrochemical cell is in the range of 60°-90° C. 
     
     
       22. The process of claims  1  or  16 , wherein the pressure of the electrochemical cell is in the range of 30-110 psig. 
     
     
       23. The process of claim  22  wherein the pressure of the electrochemical cell is in the range of 60-110 psig. 
     
     
       24. The process of claims  1  or  16 , wherein the anhydrous hydrogen halide is hydrogen chloride. 
     
     
       25. The process of claims  1  or  16 , further comprising the step of contacting the membrane with water on the cathode-side of the membrane. 
     
     
       26. The process of claims  1  or  16 , further comprising the step of contacting the membrane with an oxygen-containing gas on the cathode-side of the membrane.