Electrocatalytic conversion of carbon dioxide in liquids expanded by carbon dioxide

Abstract

Processes for the electrochemical reduction of CO2 are provided. In an embodiment, such a process comprises passing a current through a CO2 expanded liquid medium under a pressure greater than 0.2 MPa and less than 7.4 MPa in the presence of a catalyst to reduce and convert CO 2 to one or more products, wherein the CO 2 expanded liquid medium comprises dissolved CO 2 , a liquid solvent, and a dissolved electrolyte, and wherein the liquid solvent and the dissolved electrolyte are selected to provide a concentration of the dissolved CO 2 of at least 2 M at the pressure.

What is claimed is: 
     
         1 . A process for the electrochemical reduction of CO 2 , the process comprising passing a current through a CO 2  expanded liquid medium under a pressure greater than 0.2 MPa and less than 7.4 MPa in the presence of a catalyst to reduce and convert CO 2  to one or more products, wherein the CO 2  expanded liquid medium comprises dissolved CO 2 , a liquid solvent, and a dissolved electrolyte, and wherein the liquid solvent and the dissolved electrolyte are selected to provide a concentration of the dissolved CO 2  of at least 2 M at the pressure. 
     
     
         2 . The process of  claim 1 , wherein the concentration of the dissolved CO 2  is in a range of from at least 2 M to 12 M. 
     
     
         3 . The process of  claim 1 , wherein the liquid solvent is an organic liquid solvent. 
     
     
         4 . The process of  claim 3 , wherein the organic liquid solvent is selected from methanol, acetonitrile, ethyl acetate, toluene, propylene carbonate, ethylene carbonate, dimethyl carbonate, and combinations thereof. 
     
     
         5 . The process of  claim 1 , wherein the dissolved electrolyte is selected from tetrabutylammonium hexafluorophosphate, lithium perchlorate, tetraethylammonium tetrafluoroborate, potassium chloride, and combinations thereof. 
     
     
         6 . The process of  claim 1 , wherein the organic liquid solvent is acetonitrile and the dissolved electrolyte is tetrabutylammonium hexafluorophosphate. 
     
     
         7 . The process of  claim 1 , wherein the CO 2  expanded liquid medium does not comprise an ionic liquid and is not in contact with an ionic liquid. 
     
     
         8 . The process of  claim 1 , wherein the CO 2  expanded liquid medium does not comprise water and is not in contact with water. 
     
     
         9 . The process of  claim 1 , wherein the CO 2  expanded liquid medium exists as a single phase. 
     
     
         10 . The process of  claim 1 , wherein the dissolved electrolyte is present at a concentration in a range of from 0.1 M to 0.5 M. 
     
     
         11 . The process of  claim 1 , wherein the CO 2  expanded liquid medium further comprises a proton source. 
     
     
         12 . The process of  claim 11 , wherein the proton source is selected from water, an alcohol, a salt, or combinations thereof. 
     
     
         13 . The process of  claim 11 , wherein the proton source is present at an amount of no more than 1 M. 
     
     
         14 . The process of  claim 1 , wherein the selected liquid solvent and the dissolved electrolyte provide a faradaic efficiency of 80% and a selectivity of CO of 100% using a pressure of 3.1 MPa, room temperature, a timescale of two hours, a gold catalyst, and an applied potential of −2.5 V. 
     
     
         15 . The process of  claim 1 , wherein the pressure is in a range of from 1 to 5 MPa. 
     
     
         16 . The process of  claim 1 , wherein the CO 2  expanded liquid medium is at a temperature in the range of from 20° C. to 60° C. 
     
     
         17 . The process of  claim 16 , wherein the CO 2  expanded liquid medium is at room temperature. 
     
     
         18 . The process of  claim 1 , wherein the current is passed by applying a voltage across electrodes in direct contact with the CO 2  expanded liquid medium. 
     
     
         19 . The process of  claim 1 , wherein the liquid solvent is an organic liquid solvent; the CO 2  expanded liquid medium exists as a single phase; the dissolved electrolyte is present at a concentration in a range of from 0.1 M to 0.5 M; the pressure is in a range of from 1 to 5 MPa; and the CO 2  expanded liquid medium is at a temperature in the range of from 20° C. to 60° C.