Oxygen-Consuming Zero-Gap Electrolysis Cells With Porous/Solid Plates

Abstract

An electrolysis stack ( 53 ) with oxygen-depolarized cathodes ( 31 ) employs solid-plate anodes ( 38 ) and porous-plate cathodes ( 42 ). The stack ( 53 ) of electrolysis cells ( 29 ) (e.g, hydrogen-chloride or chlor-allkali cells) each include an ion exchange membrane ( 32 ) sandwiched between an anode conductor ( 34 ) and a permeable cathode ( 35 ); an oxygen-consuming gas diffusion cathode ( 31 ) is adjacent the cathode conductor of each cell. Between the anode conductor of one cell and the gas diffusion cathode of an adjacent cell there is a composite bipolar plate ( 51 ) including a solid plate ( 38 ) having channels ( 39 ) for conducing salt solution and product of the process; the bipolar plates also include a porous plate ( 42 ) having channels ( 43 ) for conducting oxidant adjacent the gas diffusion cathode and channels ( 49 ) connected to a source of liquid (such as water or dilute sodium hydroxide).

1 . A method of operating an oxygen-depolarized electrolysis cell having an anode and having a cathode including a water permeable gas diffusion electrode, said method comprising:
 feeding a solution to the anode of the cell selected from (a) a salt solution and (b) a solution of halide acid;   applying DC power between the anode and the cathode of the cell to drive electrochemical reactions in the cell to produce desired product; and   recovering desired product from the cell;   characterized by:   flowing oxygen-containing gas through passageways on a side of a porous hydrophilic plate adjacent to the gas diffusion electrode of the cathode; and   circulating a water-containing liquid solution through passageways in the porous hydrophilic plate which are separated from the flow of oxygen-containing gas.   
     
     
         2 . A method according to  claim 1  wherein said step of flowing is further characterized by:
 flowing non-hydrated oxygen-containing gas.   
     
     
         3 . A method according to  claim 1  wherein said step of flowing is further characterized by:
 flowing oxygen-containing gas which is not saturated with water.   
     
     
         4 . A method according to  claim 1  wherein said step of flowing is further characterized by:
 flowing oxygen-containing gas at a pressure which is lower than the pressure of the water-containing liquid.   
     
     
         5 . A method according to  claim 1  further characterized by:
 removing substantially all carbon dioxide from the oxygen-containing gas before flowing the oxygen-containing gas through said cell.   
     
     
         6 . A method according to  claim 1  further characterized by:
 said step of feeding comprising feeding a halide acid solution in water; and   said step of circulating comprises circulating water.   
     
     
         7 . A method according to  claim 6  further characterized by:
 said step of feeding comprises feeding hydrochloric acid.   
     
     
         8 . A method according to  claim 6  further characterized by:
 said step of feeding comprises feeding brine; and   said step of circulating comprises circulating a dilute solution of sodium hydroxide.   
     
     
         9 . An electrolysis cell ( 29 ) with an oxygen-depolarized cathode ( 31 ), comprising:
 a permeable anode conductor ( 34 ), a permeable cathode conductor ( 35 ), an ion exchange membrane ( 32 ) disposed between and contacting said conductors, a solid plate ( 38 ) having salt/product channels ( 39 ) adjacent to said anode conductor, configured to receive salt solution and configured to conduct product of said salt/product channels, and an oxygen consuming, gas diffusion cathode ( 31 ) contacting said cathode conductor;   characterized by the improvement comprising:   a porous, hydrophilic plate ( 42 ) having oxidant channels ( 43 ), extending from a first surface thereof contacting said gas diffusion cathode, configured to receive an oxygen-containing gas, said porous hydrophilic plate also having liquid channels ( 44 ), extending from a second surface thereof opposite to said first surface, configured to receive a water-containing liquid.   
     
     
         10 . An electrolysis cell ( 29 ) according to  claim 9  wherein:
 a noble metal or noble metal alloy catalyst is disposed in said cathode conductor ( 35 ) adjacent to said membrane ( 32 ).   
     
     
         11 . A stack ( 53 ) of electrolysis cells ( 29 ) according to  claim 9 . 
     
     
         12 . An electrolysis cell ( 29 ) according to  claim 9  wherein:
 said salt/product channels ( 39 ) are configured to receive brine;   said liquid channels ( 43 ) are configured to receive a dilute solution of water and sodium hydroxide; and   said salt/product channels are configured to provide chlorine as product.   
     
     
         13 . An electrolysis cell ( 29 ) according to  claim 9  wherein:
 said salt/product channels ( 39 ) are configured to receive halide acid solution;   said liquid channels ( 43 ) are configured to receive water; and   said salt/product channels are configured to provide chlorine as product.   
     
     
         14 . An electrolysis cell ( 29 ) according to  claim 13  wherein:
 said salt/product channels ( 39 ) are configured to receive hydrogen chloride solution.