Electrochemical Process and Apparatus Therefor
A process and apparatus are provided for the electrochemical reduction of carbon dioxide to formate. According one embodiment, an electrochemical process includes the catalytic electro-chemical reduction of carbon dioxide to formate utilizing a cathodic catalyst comprising tin and zinc, the zinc comprising between three and six weight percent of the catalyst. In a further embodiment, an electrochemical reactor for the electrochemical reduction of carbon dioxide to formate comprises a cathodic catalyst comprising tin and zinc, the zinc comprising between three and six weight percent of the catalyst.
1 . A process, comprising:
(a) introducing an anolyte into an anolyte compartment of an electrochemical reactor, the anolyte compartment at least partially containing an anode;
(b) introducing a catholyte into a catholyte compartment of the electrochemical reactor, the catholyte compartment separated from the anolyte compartment by a membrane, the catholyte compartment at least partially containing a cathode, the cathode comprising a cathodic catalyst, the catalyst comprising:
tin; and
zinc, wherein the zinc comprises between three weight percent and six weight percent of the cathodic catalyst;
(c) introducing carbon dioxide into the catholyte compartment of the electrochemical reactor; and
(d) impressing a DC voltage across the anode and the cathode, whereby at least a portion of the carbon dioxide is converted to formate.
2 . The process of claim 1 , the conversion of carbon dioxide to formate accomplished at a Faradaic Efficiency of between 65 percent and 68 percent.
3 . The process of claim 2 , the Faradaic Efficiency accomplished at a potential of tween −1.70 V SCE and −1.90 V SCE .
4 . The process of claim 1 , wherein the catholyte is formulated for the electrochemical reduction of carbon dioxide to formate.
5 . The process of claim 4 , wherein the catholyte comprises a solution selected from the group consisting of:
2M potassium chloride at a pH of 5.5;
2M sodium chloride at a pH of 5.3;
0.5M potassium bicarbonate at a pH of 7.5;
2M potassium chloride at a pH of 2.5;
0.5M potassium sulfate at a pH of 6.5; and
0.5M sodium sulfate at a pH of 5.5.
6 . The process of claim 1 , wherein the anolyte is formulated for the electrochemical reduction of carbon dioxide to formate.
7 . The process of claim 6 , wherein the anolyte comprises a solution selected from the group consisting of:
1M sodium hydroxide; and
0.5M sulfuric acid.
8 . The process of claim 1 , wherein the cathode is porous, and further comprising:
(a) introducing carbon dioxide from a gas compartment in fluid communication with the cathode into the cathode prior to introducing the carbon dioxide into the catholyte.
9 . The process of claim 8 , the catholyte compartment containing a porous, absorbent nonconductive pad, the pad adjacent to the membrane side of the cathode.
10 . The process of claim 9 , further comprising:
(a) introducing at least a portion of the catholyte into the porous, absorbent nonconductive pad.
11 . The process of claim 8 , further comprising:
(a) introducing carbon dioxide from the gas compartment into a diffuser prior to introducing the carbon dioxide gas into the cathode, the diffuser adjacent to the gas compartment side of the cathode.
12 . The process of claim 8 , wherein the catholyte is formulated for the electrochemical reduction of carbon dioxide to formate.
13 . The process of claim 12 , wherein the catholyte comprises a solution selected from the group consisting of:
2M potassium chloride at a pH of 5.5;
2M sodium chloride at a pH of 5.3;
0.5M potassium bicarbonate at a pH of 7.5;
2M potassium chloride at a pH of 2.5;
0.5M potassium sulfate at a pH of 6.5; and
0.5M sodium sulfate at a pH of 5.5.
14 . The process of claim 8 , wherein the anolyte is formulated for the electrochemical reduction of carbon dioxide to formate.
15 . The process of claim 14 wherein the anolyte comprises a solution selected from the group consisting of:
1M sodium hydroxide; and
0.5M sulfuric acid.
16 . An apparatus, comprising:
a container;
a membrane, the membrane positioned within the container, the membrane dividing the container into a catholyte compartment and an anolyte compartment;
a cathode, the cathode positioned at least partially within the catholyte compartment, the cathode comprising a cathodic catalyst, the cathodic catalyst comprising:
tin; and
zinc, wherein the zinc comprises between three weight percent and six weight percent of the cathodic catalyst; and
an anode, the anode positioned at least partially within the anolyte compartment.
17 . The apparatus of claim 16 , wherein the cathode is porous, and further comprising a gas compartment, the gas compartment in fluid communication with the cathode.
18 . The apparatus of claim 17 , further comprising a porous, absorbent nonconductive pad, the pad adjacent to the membrane side of the cathode.
19 . The apparatus of claim 17 , further comprising a diffuser adjacent to the gas compartment side of the cathode.
20 . A process, comprising:
(a) introducing a catholyte into the catholyte compartment of claim 16 ;
(b) introducing an anolyte into the anolyte compartment of claim 16 ;
(c) impressing a DC voltage across the anode and the cathode of claim 16 ; and
(d) withdrawing formate from the cathode compartment of claim 16 .