Separators for Gaseous Products in Oxocarbon Electrolyzers

Abstract

This disclosure relates to systems and methods for gas separation in oxocarbon electrolyzers. A disclosed method includes supplying an oxocarbon to an input stream of a cathode chamber of an oxocarbon electrolyzer, converting the oxocarbon to a product gas in the cathode chamber, obtaining an output stream, with the product gas and residual oxocarbon, from the oxocarbon electrolyzer, and recycling a portion of the product gas, from the output stream, to the input stream.

What is claimed is: 
     
         1 . A method comprising:
 supplying an oxocarbon to an input stream of a cathode chamber of an oxocarbon electrolyzer;   reducing the oxocarbon at a cathode electrode of the oxocarbon electrolyzer under conditions effective to produce a first product gas and a second product gas in the cathode chamber;   obtaining an output stream from the oxocarbon electrolyzer comprising the first product gas, the second product gas, and residual oxocarbon;   supplying the first product gas, the second product gas, and the residual oxocarbon to a gas/liquid separator system; and   recycling a first portion, of the first product gas and the second product gas, from one or more outputs of the gas/liquid separator system to the input stream.   
     
     
         2 . The method of  claim 1 , further comprising:
 supplying a second portion, of the first product gas and the second product gas, from the one or more outputs of the gas/liquid separator system to a gas separator.   
     
     
         3 . The method of  claim 2 , further comprising:
 controlling the first portion, of the first product gas and the second product gas, that is recycled to the input stream of the cathode chamber to maintain less than 50 mole percentage of the oxocarbon in the input stream.   
     
     
         4 . The method of  claim 2 , wherein:
 the mole percentage of the oxocarbon in the input stream is less than 50 and the combined mole percentage of the first product gas and the second product gas in the input stream is greater than 5.   
     
     
         5 . The method of  claim 2 , further comprising:
 supplying the output stream to a first separator; and   controlling the first portion, of the first product gas and the second product gas, that is recycled to the input stream to maintain higher than 50 combined mole percentage of the first product gas and second product gas at an input to the first separator.   
     
     
         6 . The method of  claim 5 , wherein:
 the first separator is a membrane separator, a pressure swing adsorption separator, a temperature swing adsorption separator, a cryogenic separator or a lean oil absorption separator.   
     
     
         7 . The method of  claim 1 , further comprising:
 supplying the first product gas, the second product gas, and the residual oxocarbon to a gas/liquid separator system; and   separating the first product gas, the second product gas, and the residual oxocarbon from one or more liquid products using the gas/liquid separator system;   wherein the one or more liquid products comprise alcohols or carboxylates; and   wherein the recycling of a portion, of the first product gas and the second product gas, from the output stream, to the input stream decreases the selectivity of reactions in the cathode chamber that create the alcohols or carboxylates.   
     
     
         8 . The method of  claim 1 , wherein:
 the oxocarbon is carbon monoxide;   the first product gas is ethylene; and   the oxocarbon electrolyzer is a carbon monoxide electrolyzer.   
     
     
         9 . The method of  claim 1 , wherein:
 the oxocarbon is carbon dioxide;   the first product gas is carbon monoxide; and   the oxocarbon electrolyzer is a carbon dioxide electrolyzer.   
     
     
         10 . The method of  claim 1 , further comprising:
 controlling a portion of the first product gas and at least one additional product gas that are recycled to the input stream of the cathode chamber to: (i) maintain less than 50 mole percentage of the oxocarbon in the input stream; and (ii) maintain greater than 50 combined mole percentage of product gas and at least one additional product gas in the input stream.   
     
     
         11 . The method of  claim 1 , wherein:
 the oxocarbon is carbon monoxide;   the first product gas is ethylene;   the second product gas is hydrogen; and   the oxocarbon electrolyzer is a carbon monoxide electrolyzer.   
     
     
         12 . The method of  claim 1 , wherein:
 the oxocarbon is carbon dioxide;   the first product gas is carbon monoxide;   the second product gas is hydrogen or ethylene; and   the oxocarbon electrolyzer is a carbon dioxide electrolyzer.   
     
     
         13 . A method comprising:
 supplying a gaseous input stream comprising at least an oxocarbon to an input stream of a cathode chamber of an oxocarbon electrolyzer;   converting the oxocarbon to a product gas in the cathode chamber;   obtaining an output stream, with the product gas and residual oxocarbon, from the oxocarbon electrolyzer;   monitoring, with one or more sensors, at least a composition of the gaseous input stream; and   recycling a portion of at least one of the product gas and the residual oxocarbon, from the output stream, to the input stream;   wherein: (i) the composition of the gaseous input stream can be variable; and (ii) the amount of the portion of the at least one of the product gas and the residual oxocarbon recycled from the output stream is dynamically controlled based on the composition of the gaseous input stream.   
     
     
         14 . The method of  claim 13 , further comprising:
 supplying the output stream to a first separator;   wherein the portion of the at least one of the product gas and the residual oxocarbon is recycled from after the first separator to the input stream.   
     
     
         15 . The method of  claim 13 , wherein an additional portion of the output stream is recycled from before a first separator to the input stream. 
     
     
         16 . The method of  claim 13 , further comprising:
 monitoring, with the one or more sensors, a composition of the output stream;   wherein the amount of the portion of the at least one of the product gas and the residual oxocarbon recycled from the output stream is also controlled based on the composition of the output stream.   
     
     
         17 . A system comprising:
 an oxocarbon electrolyzer having a cathode chamber, wherein the oxocarbon electrolyzer is configured to reduce an oxocarbon in an input stream to a product gas;   a supply configured to introduce the oxocarbon into the input stream, the supply containing one or more additional gases;   an output of the oxocarbon electrolyzer with an output stream, wherein the output stream includes the product gas and residual oxocarbon;   a recycle conduit configured to recycle a portion of at least one of the product gas and the residual oxocarbon, from the output stream, to the input stream; and   a sensor arrangement configured to monitor, using one of indirect and direct monitoring, the composition of the supply including the oxocarbon and the one or more additional gases;   wherein the recycle conduit is configured such that the portion of the at least one of the product gas and the residual oxocarbon is based on the composition of the input stream as measured by the sensor arrangement.   
     
     
         18 . The system of  claim 17 , wherein:
 the sensor arrangement is also configured to monitor at least one of the composition of the input stream and the output stream; and further comprising:   a control system configured to adjust the portion of the at least one of the product gas and the residual oxocarbon being recycled to an input of the cathode chamber to maintain less than 50 mole percent of the oxocarbon in the input stream.   
     
     
         19 . The system of  claim 18 , wherein the control system is also configured to adjust the at least one of the product gas and the oxocarbon being recycled to the cathode chamber based on the composition of the output stream. 
     
     
         20 . The system of  claim 17 , wherein:
 the sensor arrangement is further configured to monitor, in real time and using a combination of direct gas-composition sensors and indirect parameters derived from pressure, temperature, or flow measurements, at least one of (i) the composition of the input stream to the cathode chamber and (ii) the composition of the output stream from the oxocarbon electrolyzer; and   the system further comprises a programmable control system that dynamically adjusts, based on the monitored compositions, a flow-control element within the recycle conduit so as to: (i) maintain the mole percentage of the oxocarbon in the input stream below about fifty mole percent while simultaneously maintaining a combined mole percentage of recycled product gas and residual oxocarbon greater than about five mole percent; and (ii) regulate the total pressure and partial pressure of the oxocarbon in the cathode chamber to suppress undesirable side reactions and improve catalyst selectivity towards the product gas.