Electrolytic recovery of retained carbon dioxide

Abstract

Methods and apparatus relate to capturing carbon dioxide. A solution formed from metal ions combined with an amine reagent absorbs carbon dioxide from gas introduced into the solution. Subsequent electrolysis of the solution results in dissociation of complexes formed upon the carbon dioxide being absorbed. The electrolysis thus liberates the carbon dioxide for capture and regenerates the solution for reuse.

1 . A method comprising:
 contacting an aqueous solution formed from amine and metal ions with a gas mixture containing carbon dioxide, wherein the contacting forms metallocarbamate complexes from the amine, the metal ions and the carbon dioxide;   separating the aqueous solution from unabsorbed constituents of the gas mixture after the contacting; and   applying an electric potential to the aqueous solution recovered by the separating, wherein the electric potential causes dissociation of the metallocarbamate complexes in order to liberate the carbon dioxide for capture.   
     
     
         2 . The method according to  claim 1 , wherein the aqueous solution is formed on a mole basis from less of the metal ions than the amine. 
     
     
         3 . The method according to  claim 1 , wherein one of the metal ions reacts with different molecules throughout regeneration of the aqueous solution by the applying of the electric potential. 
     
     
         4 . The method according to  claim 1 , wherein the amine includes alcohol amine. 
     
     
         5 . The method according to  claim 1 , wherein the amine has a formula 
       
         
           
           
               
               
           
         
       
       with R 1  being C x H 2x OH and R 2  being one of hydrogen and C x H 2x OH given x is from 2 to 4. 
     
     
         6 . The method according to  claim 1 , wherein the amine includes at least one of monoethanolamine (MEA), diethanolamine (DEA), diisopropanolamine (DIPA) and diglycolamine (DGA). 
     
     
         7 . The method according to  claim 1 , wherein the metal ions include at least one of copper, zinc, cobalt, nickel, aluminum and magnesium. 
     
     
         8 . The method according to  claim 1 , wherein the metal ions include copper. 
     
     
         9 . The method according to  claim 1 , wherein the amine includes monoethanolamine and the metal ions include copper. 
     
     
         10 . The method according to  claim 1 , wherein the applying of the electric potential includes cycling a working electrode between positive and negative potentials. 
     
     
         11 . The method according to  claim 1 , wherein the applying of the electric potential utilizes a carbon working electrode. 
     
     
         12 . The method according to  claim 1 , wherein the applying of the electric potential occurs with the aqueous solution pumped above a first pressure associated with the contacting such that the carbon dioxide is liberated at a second pressure above the first pressure. 
     
     
         13 . The method according to  claim 1 , further comprising forming the aqueous solution by adding a metal salt to a reagent containing the amine, wherein the metal ions are from the metal salt. 
     
     
         14 . The method according to  claim 1 , further comprising forming the aqueous solution using a counter electrode made from source metal in a reagent containing the amine, wherein the metal ions are from the source metal of the counter electrode. 
     
     
         15 . The method according to  claim 1 , wherein the applying of the electric potential regenerates the aqueous solution for reuse in a cycle of more carbon dioxide absorption and liberation. 
     
     
         16 . A method comprising:
 forming an aqueous solution by mixing monoethanolamine and copper ions from copper sulfate;   contacting the aqueous solution with a gas mixture containing carbon dioxide, wherein the contacting forms metallocarbamate complexes from the monoethanolamine, the copper ions and the carbon dioxide;   separating the aqueous solution from unabsorbed constituents of the gas mixture after the contacting;   pumping the aqueous solution recovered by the separating to increase pressure of the aqueous solution to above a first pressure associated with the contacting; and   applying an electric potential to the aqueous solution to liberate from the aqueous solution the carbon dioxide at a second pressure above the first pressure due to the pumping.   
     
     
         17 . The method according to  claim 16 , wherein the forming of the aqueous solution includes mixing reagent of between 10 percent and 20 percent monoethanolamine in water with the copper sulfate such that the copper ions added are between 1 mole percent and 5 mole percent relative to the monoethanolamine. 
     
     
         18 . A method comprising:
 forming an aqueous solution by mixing amine and metal ions, wherein on a mole basis less of the metal ions are added than the amine;   contacting the aqueous solution with a gas mixture containing carbon dioxide, wherein the aqueous solution absorbs the carbon dioxide;   separating the aqueous solution from unabsorbed constituents of the gas mixture after the contacting; and   applying an electric potential to the aqueous solution recovered by the separating, wherein one of the metal ions reacts with more than one molecule to facilitate liberation of the carbon dioxide and regeneration of the aqueous solution throughout the applying of the electric potential.   
     
     
         19 . The method according to  claim 18 , wherein metallocarbamate complexes form upon the aqueous solution absorbing the carbon dioxide. 
     
     
         20 . The method according to  claim 18 , wherein the applying of the electric potential includes cycling between positive and negative voltages.