Reduction of Carbon Dioxide to Carboxylic Acids, Glycols, and Carboxylates

Abstract

Methods and systems for electrochemical conversion of carbon dioxide to carboxylic acids, glycols, and carboxylates are disclosed. A method may include, but is not limited to, steps (A) to (D). Step (A) may introduce water to a first compartment of an electrochemical cell. The first compartment may include an anode. Step (B) may introduce carbon dioxide to a second compartment of the electrochemical cell. The second compartment may include a solution of an electrolyte and a cathode. Step (C) may apply an electrical potential between the anode and the cathode in the electrochemical cell sufficient to reduce the carbon dioxide to a carboxylic acid intermediate. Step (D) may contact the carboxylic acid intermediate with hydrogen to produce a reaction product.

What is claimed is: 
     
         1 . A method for electrochemical conversion of carbon dioxide, comprising:
 (A) introducing a liquid to a first compartment of an electrochemical cell, the first compartment including an anode;   (B) introducing carbon dioxide to a second compartment of the electrochemical cell, the second compartment including a solution of an electrolyte, a cathode, and a homogenous heterocyclic amine catalyst, the cathode selected from the group consisting of cadmium, a cadmium alloy, cobalt, a cobalt alloy, nickel, a nickel alloy, chromium, a chromium alloy, indium, an indium alloy, iron, an iron alloy, copper, a copper alloy, lead, a lead alloy, palladium, a palladium alloy, platinum, a platinum alloy, molybdenum, a molybdenum alloy, tungsten, a tungsten alloy, niobium, a niobium alloy, silver, a silver alloy, tin, a tin alloy, rhodium, a rhodium alloy, ruthenium, a ruthenium alloy, carbon, and mixtures thereof;   (C) applying an electrical potential between the anode and the cathode sufficient for the cathode to reduce the carbon dioxide to a carboxylic acid intermediate; and   (D) contacting the carboxylic acid intermediate with hydrogen to produce a reaction product.   
     
     
         2 . The method of  claim 1 , wherein the carboxylic acid intermediate includes at least one of formate, formic acid, glycolate, glycolic acid, glyoxylate, glyoxylic acid, lactate, lactic acid, oxalate, or oxalic acid. 
     
     
         3 . The method of  claim 1 , wherein the reaction product includes at least one of formaldehyde, formic acid, methanol, glyoxylic acid, glycolic acid, glyoxal, glycolaldehyde, ethylene glycol, acetic acid, acetaldehyde, ethanol, lactic acid, oxalic acid, propylene glycol, or isopropanol. 
     
     
         4 . The method of  claim 1 , wherein the carboxylic acid intermediate includes formic acid, and wherein the reaction product includes at least one of formaldehyde or methanol. 
     
     
         5 . The method of  claim 1 , wherein the carboxylic acid intermediate includes oxalic acid, and wherein the reaction product includes at least one of glyoxylic acid, glycolic acid, glyoxal, glycolaldehyde, ethylene glycol, acetic acid, acetaldehyde, or ethanol. 
     
     
         6 . The method of  claim 1 , wherein the carboxylic acid intermediate includes lactic acid, and wherein the reaction product includes at least one of propylene glycol or isopropanol. 
     
     
         7 . The method of  claim 1 , wherein the carboxylic acid intermediate includes glyoxylic acid, and wherein the reaction product includes at least one of glycolic acid, glyoxal, glycolaldehyde, ethylene glycol, acetic acid, acetaldehyde, or ethanol. 
     
     
         8 . The method of  claim 1 , wherein the carboxylic acid intermediate includes glycolic acid, and wherein the reaction product includes at least one of glycolaldehyde, ethylene glycol, acetic acid, acetaldehyde, or ethanol. 
     
     
         9 . The method of  claim 1 , wherein a pH of the second compartment is between about 1 and about 8. 
     
     
         10 . The method of  claim 1 , further comprising:
 adjusting a pH of the second compartment to favor production of one of a carboxylic acid and a carboxylic acid intermediate over production of the other of the one of a carboxylic acid and a carboxylic acid intermediate.   
     
     
         11 . A system for electrochemical reduction of carbon dioxide, comprising:
 an electrochemical cell including:
 a first cell compartment; 
 an anode positioned within said first cell compartment; 
 a second cell compartment; 
 a separator interposed between said first cell compartment and said second cell compartment, said second cell compartment containing an electrolyte; and 
 a cathode and a homogenous heterocyclic amine catalyst positioned within said second cell compartment, said cathode selected from the group consisting of cadmium, a cadmium alloy, cobalt, a cobalt alloy, nickel, a nickel alloy, chromium, a chromium alloy, indium, an indium alloy, iron, an iron alloy, copper, a copper alloy, lead, a lead alloy, palladium, a palladium alloy, platinum, a platinum alloy, molybdenum, a molybdenum alloy, tungsten, a tungsten alloy, niobium, a niobium alloy, silver, a silver alloy, tin, a tin alloy, rhodium, a rhodium alloy, ruthenium, a ruthenium alloy, carbon, and mixtures thereof; 
   an energy source operably coupled with said anode and said cathode, said energy source configured to apply a voltage between said anode and said cathode to reduce carbon dioxide at said cathode to an intermediate product stream including a carboxylic acid;   an extractor configured to extract the carboxylic acid from the intermediate product stream; and   a secondary reactor configured to introduce the carboxylic acid to hydrogen from a hydrogen source, the secondary reactor configured to produce at least one of formaldehyde, methanol, glycolic acid, glyoxal, glyoxylic acid, glycolaldehyde, ethylene glycol, acetic acid, acetaldehyde, ethanol, propylene glycol, or isopropanol.