Multiple phase SO3/SO2/H2O/H2SO4 electrolyzer

Abstract

An electrolyzer ( 16 ) having opposed electrodes ( 44, 46 ) to produce hydrogen gas operates at a pressure greater than 5.5 MPa, where SO 2 is liquefied, and a reaction phase ( 48 ) of liquid SO 2 and H 2 O which is passed to the electrolyzer where liquid SO 3 is formed as a bottom phase ( 54 ), and where the amount of water present is less than two moles per mole of liquid SO 2 .

1 . a method of operating an electrolyzer having an anode electrode and an opposed cathode electrode to produce hydrogen gas at a pressure greater than 5.5 MPa comprising: 
 (1) liquefying SO 2  at a pressure greater than 5.5 MPa in the presence of H 2 O to provide a reaction phase which is passed to the anode of an electrolyzer, where the liquid SO 2  is immiscible in the H 2 O, where the amount of water present is less than or equal to two moles per mole of liquid SO 2 ;    (2) forming liquid SO 3  from oxidizing the liquid SO 2  to liquid SO 3  on the anode in the electrolyzer where the liquid SO 3  is reactive to excess H 2 O, and where 2H +  and 2e −  are provided at or near the cathode;    (3) formation of a liquid phase in the electrolyzer from the SO 3  and excess H 2 O where the liquid phase is selected from the group consisting of dense H 2 SO 4  solution and liquid SO 3  both of which are more dense than liquid H 2 O or liquid SO 2 ;    (4) recovering a liquid from the electrolyzer where the liquid is selected from the group consisting of liquid SO 3  and liquid H 2 SO 4 ; and    (5) recovering hydrogen gas from the cathode of the electrolyzer by reaction of the 2H +  and 2e −  provided in (2).    
   
   
       2 . The method of  claim 1 , wherein the pressure is from 5.5 MPa to 11.7 MPa.  
   
   
       3 . The method of  claim 1 , wherein the pressure is from 6.9 MPa to 11.7 MPa.  
   
   
       4 . The method of  claim 1 , wherein liquid SO 3  is recovered at a temperature from 20° C. to 75° C.  
   
   
       5 . The method of  claim 1 , wherein the following reactions occur:  
       SO 2 (liquid)+H 2 O (liquid)→2H + +2e − +SO 3 (liquid)  2H + +2e − →H 2 O (gas); and optionally  SO 3 (liquid)+H 2 O (liquid)→H 2 SO 4 (liquid)  
   
   
       6 . The method of  claim 1  where the electrolyzer is used in the operation of the Westinghouse Sulfur Process.  
   
   
       7 . The method of  claim 1 , wherein H +  and H 2 O pass through a microporous or ion exchange membrane separating the electrolyzer into an anode chamber and a cathode chamber, to form H 2  at or near the cathode electrode.  
   
   
       8 . The method of  claim 1 , wherein liquefaction of SO 2  in (1) occurs in a scrubber where two phases form; a lighter phase of water with dissolved SO 2  and a heavier phase of liquefied SO 2  with dissolved water, which heavier phase is passed to the electrolyzer.  
   
   
       9 . The method of  claim 8 , wherein the scrubber operates at pressures greater than 5.5 MPa.  
   
   
       10 . The method of  claim 8 , wherein the scrubber operates at pressures from 5.5 MPa to 11.7 MPa.  
   
   
       11 . The method of  claim 8 , wherein the scrubber operates at pressures from 6.9 MPa to 11.7 MPa.  
   
   
       12 . A method of operating a Westinghouse Sulfur Process containing an electrolysis oxidation step or an Iodine Sulfur Process containing an iodine/sulfur oxidation step, at a pressure greater than 5.5 MPa to allow the formation of feed with a minimal amount of water used in the oxidation step, where SO 3  is generated to form a solution layer denser than water, and water plus immiscible liquid SO 2 , where the liquid SO 3  is recovered or is reacted with water to form liquid H 2 SO 4 , where the H 2 O:SO 3  mole ratio is lower than 1:1 (less H 2 O than SO 2 ) and the product of the oxidation step contains pure SO 3  and/or H 2 SO 4 .  
   
   
       13 . The method of  claim 12 , wherein the pressure is from 6.9 MPa to 11.7 MPa.