System and Process for Making Formic Acid

Abstract

Methods and systems for electrochemical production of formic acid 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. The cathode is selected from the group consisting of indium, lead, tin, cadmium, and bismuth. The second compartment may include a pH of between approximately 4 and 7. Step (C) may apply an electrical potential between the anode and the cathode in the electrochemical cell sufficient to reduce the carbon dioxide to formic acid. Step (D) may maintain a concentration of formic acid in the second compartment at or below approximately 500 ppm.

1 .- 10 . (canceled) 
     
     
         11 . A system for electrochemical production of at least formic acid, comprising:
 an electrochemical cell including:
 a cathode; and 
 a catholyte, the pH of the catholyte being maintained from 4.3 to 5.5, the catholyte including formic acid maintained at a concentration of no greater than about 500 ppm. 
   
     
     
         12 . The system of  claim 11 , wherein the electrolyte includes at least one of potassium sulfate, potassium chloride, sodium chloride, sodium sulfate, lithium sulfate, sodium perchlorate, or lithium chloride. 
     
     
         13 . The system of  claim 11 , wherein the second cell compartment includes a heterocyclic aromatic amine selected from the group consisting of 4-hydroxy pyridine, adenine, a heterocyclic amine containing sulfur, a heterocyclic amine containing oxygen, an azole, benzimidazole, a bipyridine, furan, an imidazole, an imidazole related species with at least one five-member ring, an indole, methylimidazole, an oxazole, phenanthroline, pterin, pteridine, a pyridine, a pyridine related species with at least one six-member ring, pyrrole, quinoline, or a thiazole, and mixtures thereof. 
     
     
         14 . The system of  claim 13 , wherein the heterocyclic aromatic amine is 4-hydroxy pyridine. 
     
     
         15 . The system of  claim 13 , wherein a multi-carbon containing product is produced in the cell. 
     
     
         16 . The system of  claim 11 , wherein the cathode is selected from the group consisting of indium, lead, tin, cadmium, and bismuth. 
     
     
         17 . The system of  claim 16 , wherein the cathode comprises indium. 
     
     
         18 . The system of  claim 11 , further including:
 an extractor configured for extraction of formic acid from the second cell compartment to maintain the concentration of formic acid to no greater than about 500 ppm.   
     
     
         19 . A method for electrochemical production of at least formic acid, 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 and a cathode, the electrolyte in the second compartment having a pH which provides a concentration of hydrogen ions, carbon dioxide, and water at a surface of the cathode to favor reduction of carbon dioxide at the cathode;   (C) applying an electrical potential between the anode and the cathode in the electrochemical cell sufficient for the cathode to reduce the carbon dioxide to at least formic acid; and   (D) maintaining a concentration of formic acid in the second compartment at or below approximately 500 ppm.   
     
     
         20 . The method of  claim 19 , wherein the cathode includes at least one of indium, lead, tin, cadmium, bismuth, or indium. 
     
     
         21 . The method of  claim 20 , wherein the cathode comprises indium. 
     
     
         22 . The method of  claim 19 , wherein the liquid is water. 
     
     
         23 . A process for reducing carbon dioxide, the process comprising:
 (A) providing an electrochemical cell have a catholyte;   (B) applying a voltage to the cell; and   (C) monitoring the pH of the catholyte and the concentration of formic acid in the catholyte to generate a faradaic yield of at least 50%.   
     
     
         24 . The process of  claim 22 , wherein the cell includes an indium cathode. 
     
     
         25 . The process of  claim 22 , wherein the cell includes divalent ions. 
     
     
         26 . The process of  claim 22 , wherein the faradic yield is at least 60%. 
     
     
         27 . The process of  claim 22 , wherein the faradic yield is at least 70%. 
     
     
         28 . The process of  claim 22 , wherein the faradic yield is at least 80%. 
     
     
         29 . The process of  claim 22 , wherein the pH of the catholyte is maintained between about 4.3 and about 5.5. 
     
     
         30 . The process of  claim 26 , wherein the applied voltage is about −1.46 V vs. SCE.