Method of operating electrochemical reaction device and electrochemical reaction device

Abstract

A method of operating an electrochemical reaction device, includes controlling an electrolytic unit during each of a startup process, an operation process, and a shutdown process so that a first time-averaged pressure at a first position in the cathode space and closer to an inlet of a cathode space than an outlet of the cathode space is equal to or higher than a second time-averaged pressure at a second position in an anode space and opposite the first position with a diaphragm therebetween, and a third time-averaged pressure at a third position in the cathode space and closer to the outlet than the inlet is equal to or higher than a fourth time-averaged pressure at a fourth position in the anode space and opposite the third position with the diaphragm therebetween.

What is claimed is: 
     
         1 . A method of operating an electrochemical reaction device,
 the device comprising an electrolytic unit having a cathode, an anode, a cathode space facing on the cathode, an anode space facing on the anode, and a diaphragm provided between the cathode space and the anode space,   the method comprising:   a startup process of regulating at least one parameter selected from the group consisting of a plurality of parameters in the electrolytic unit to satisfy an operation start condition, the plurality of parameters including a temperature, a pressure, a current density, a voltage, a composition of a first fluid containing a reducible material to be supplied to the cathode space, a flow rate of the first fluid, a composition of a second fluid containing an oxidizable material to be supplied to the anode space, and a flow rate of the second fluid;   an operation process of using the electrolytic unit in an operation condition range including the operation start condition and reducing the reducible material in the cathode to produce a reduction product;   a shutdown process of regulating at least one parameter selected from the group consisting of the plurality of parameters to satisfy a storage start condition; and   a storage process of using the electrolytic unit in a storage condition range including the storage start condition, wherein   the electrolytic unit is controlled during each of the startup process, the operation process, and the shutdown process so that a first time-averaged pressure at a first position in the cathode space is equal to or higher than a second time-averaged pressure at a second position in the anode space and a third time-averaged pressure at a third position in the cathode space is equal to or higher than a fourth time-averaged pressure at a fourth position in the anode space, the first position being closer to an inlet of the cathode space than an outlet of the cathode space, the second position being opposite the first position with the diaphragm therebetween, the third position being closer to the outlet than the inlet, and the fourth position being opposite the third position with the diaphragm therebetween.   
     
     
         2 . The method according to  claim 1 , wherein
 the electrolytic unit is controlled during each of the startup process, the operation process, and the shutdown process so that the first time-averaged pressure is higher than the second time-averaged pressure and the third time-averaged pressure is higher than the fourth time-averaged pressure.   
     
     
         3 . The method according to  claim 1 , wherein:
 the operation process is performed next to the startup process;   the shutdown process is performed next to the operation process; and   the storage process is performed next to the shutdown process.   
     
     
         4 . The method according to  claim 3 , wherein
 the startup process is performed next to the storage process again; and   a sequence of the startup process, the operation process, the shutdown process, and the storage process is repeated multiple times.   
     
     
         5 . The method according to  claim 1 , wherein
 the diaphragm is a porous membrane.   
     
     
         6 . The method according to  claim 1 , wherein
 a reduction reaction of carbon dioxide occurs on the cathode.   
     
     
         7 . The method according to  claim 1 , wherein
 in the startup process, a humidified gas is supplied as the first fluid to the cathode space.   
     
     
         8 . The method according to  claim 1 , wherein
 in the startup process, the electrolytic unit is preheated.   
     
     
         9 . The method according to  claim 1 , wherein
 in the shutdown process, a purge operation in the anode space and the cathode space is performed.   
     
     
         10 . The method according to  claim 9 , wherein
 in the purge operation, a fluid in the cathode space is replaced with a humidified gas.   
     
     
         11 . The method according to  claim 1 , wherein:
 during the operation process,   a flow rate of the reducible material to be supplied to the cathode space is constantly equal to or more than a theoretical amount of the reducible material calculated from a current flowing through the electrolytic unit; and   a flow rate of the oxidizable material to be supplied to the anode space is constantly equal to or more than a theoretical amount of the oxidizable material calculated from the current.   
     
     
         12 . The method according to  claim 1 , wherein:
 during the startup process and the shutdown process,   a flow rate of the reducible material to be supplied to the cathode space is constantly equal to or more than a theoretical amount of the reducible material calculated from a current flowing through the electrolytic unit; and   a flow rate of the oxidizable material to be supplied to the anode space is constantly equal to or more than a theoretical amount of the oxidizable material calculated from the current.   
     
     
         13 . The method according to  claim 1 , wherein
 during the startup process, the operation process, the shutdown process, and the storage process,   a current density in the electrolytic unit is constantly −5 mA/cm 2  or higher with a direction of flowing from the cathode through an external circuit including a power supply into the anode set to be positive.   
     
     
         14 . The method according to  claim 1 , wherein
 during the startup process, the operation process, the shutdown process, and the storage process,   an electric potential of the cathode based on a standard hydrogen electrode reference is constantly +1.5 V or less.   
     
     
         15 . The method according to  claim 1 , wherein
 during the storage process, a current density in the electrolytic unit is zero.   
     
     
         16 . The method according to  claim 1 , wherein
 during the storage process, a current density in the electrolytic unit is higher than zero.   
     
     
         17 . The method according to  claim 1 , wherein
 the electrolytic unit is controlled during the storage process so that the first time-averaged pressure is equal to or higher than the second time-averaged pressure and the third time-averaged pressure is equal to or higher than the fourth time-averaged pressure.   
     
     
         18 . The method according to  claim 1 , wherein
 the electrolytic unit is controlled during the storage process so that the first time-averaged pressure is higher than the second time-averaged pressure, and the third time-averaged pressure is higher than the fourth time-averaged pressure.   
     
     
         19 . The method according to  claim 1 , wherein
 during the startup process,   a maximum increase rate of a current supplied to the electrolytic unit is 1 mA/cm 2  per second or less.   
     
     
         20 . An electrochemical reaction device operable by the method according to  claim 1 ,
 the device comprising:   the electrolytic unit;   a power supply configured to supply current or voltage to the electrolytic unit;   a temperature regulator configured to regulate a temperature in the electrolytic unit;   a pressure regulator configured to regulate a pressure in the electrolytic unit; and   a controller configured to control the electrolytic unit, the power supply, the temperature regulator, and the pressure regulator to control an operation of operating the device according to the method.