Method for removing oxygen molecules and method for purifying carbon monoxide

Abstract

Provided is a method for purifying carbon monoxide with which it is possible to obtain high-purity carbon monoxide. In a catalyst preparation step, water is removed from a platinum catalyst by heat treatment of a platinum catalyst in a heat treatment vessel. This heat treatment is carried out until the concentration of water contained in the inert gas discharged from the heat treatment vessel after being supplied to the heat treatment vessel and used in heat treatment is less 1000 vol ppm. In an oxygen molecule removal step, carbon-monoxide-containing gas is brought into contact with a platinum catalyst, an oxygen molecule is removed from the carbon-monoxide-containing gas, and gas having an oxygen molecule removed is obtained. In a carbon dioxide removal step, carbon dioxide is removed from gas having an oxygen molecule removed using a carbon dioxide adsorbent, and gas having carbon dioxide removed is obtained. In a pressure swing adsorption step, carbon monoxide is recovered from gas having carbon dioxide removed by a pressure swing adsorption method, and purified carbon monoxide having a purity of 99.95 vol% or higher is obtained.

Description

Technical Field

[0001] The present invention relates to a method for removing oxygen molecules and a method for purifying carbon monoxide.

Background Art

[0002] Carbon monoxide (CO) is used as an additive gas in the dry etching process for manufacturing silicon semiconductors of non-volatile memories such as NAND flash memories. For carbon monoxide used in this application, a high purity of about 99.99% by volume is required.

[0003] As a method for purifying carbon monoxide, generally, the pressure swing adsorption method (PSA method: Pressure Swing Adsorption method) is adopted. For example, in Patent Documents 1 and 2, a method for purifying carbon monoxide by the pressure swing adsorption method using a pressure swing adsorbent in which cuprous chloride (CuCl) is supported on a carrier such as alumina or activated carbon is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when cuprous chloride contained in the pressure swing adsorbent reacts with oxygen molecules (O2) and is oxidized to cupric chloride (CuCl2), the adsorption performance of carbon monoxide decreases. Therefore, it is preferable to remove the oxygen molecules contained in carbon monoxide before bringing carbon monoxide into contact with the pressure swing adsorbent and performing purification by the pressure swing adsorption method.

[0006] For example, Patent Document 3 discloses a technique for removing oxygen molecules from a carbon monoxide-containing gas by contacting the gas, which contains carbon monoxide and oxygen molecules as impurities, with activated carbon. However, because activated carbon has a low ability to adsorb oxygen molecules, a large amount of activated carbon is required to reduce the concentration of oxygen molecules in the carbon monoxide-containing gas to less than 1 ppm by volume. Therefore, industrially removing oxygen molecules from carbon monoxide-containing gas requires large-scale equipment, and there is a problem in that it is difficult to remove oxygen molecules simply.

[0007] The present invention aims to provide a method for removing oxygen molecules from a carbon monoxide-containing gas that can be easily removed. Furthermore, the present invention also aims to provide a method for purifying carbon monoxide that can be obtained in high purity. [Means for solving the problem]

[0008] To solve the aforementioned problems, one aspect of the present invention is as follows [1] to

[13] . [1] A catalyst preparation step comprising: placing a platinum catalyst containing platinum in a heat treatment container where the pressure is maintained below atmospheric pressure; and heating the platinum catalyst in the heat treatment container while supplying and passing an inert gas through the heat treatment container, thereby removing the water contained in the platinum catalyst; and continuing the heat treatment until the concentration of water contained in the inert gas supplied to the heat treatment container and discharged from the heat treatment container after being used for the heat treatment is less than 1000 ppm by volume; An oxygen molecule removal step is performed to remove oxygen molecules from the carbon monoxide-containing gas, which contains carbon monoxide and oxygen molecules as impurities, wherein the concentration of carbon monoxide is 10% by volume or more and the concentration of water is less than 1000 ppm by volume, by contacting the platinum catalyst that has been subjected to the heat treatment in the catalyst preparation step, thereby obtaining an oxygen molecule-removed gas in which the concentration of oxygen molecules has been reduced. A method for removing oxygen molecules, comprising the following:

[0009] [2] The method for removing oxygen molecules according to [1], wherein the concentration of oxygen molecules contained in the carbon monoxide-containing gas is less than 2000 ppm by volume. [3] The method for removing oxygen molecules according to [1] or [2], wherein the carbon monoxide-containing gas further contains at least one selected from hydrogen molecules, nitrogen molecules, carbon dioxide, argon, helium, and methane.

[0010] [4] The method for removing oxygen molecules according to any one of the items [1] to [3], wherein in the oxygen molecule removal step, the concentration of the oxygen molecules contained in the gas after the removal of the oxygen molecules is reduced to less than 1 volume ppm.

[0011] [5] The method for removing oxygen molecules according to any one of the following [1] to [4], wherein in the oxygen molecule removal step, the carbon monoxide-containing gas is introduced and passed through a reaction tube filled with the heat-treated platinum catalyst, and the rate at which the carbon monoxide-containing gas is introduced into the reaction tube is 500 / h or more and 1500 / h or less in space velocity.

[0012] [6] The method for removing oxygen molecules according to any one of the items [1] to [5], wherein the pressure conditions for the heat treatment in the catalyst preparation step are -0.09 MPaG or more and -0.01 MPaG or less, and the temperature conditions are 150°C or more and 300°C or less. [7] The method for removing oxygen molecules according to any one of [1] to [6], wherein the inert gas is at least one selected from nitrogen molecules, helium, and argon.

[0013] [8] A method for removing oxygen molecules according to any one of the items [1] to [7], further comprising a dehydration step of removing moisture from the carbon monoxide-containing gas using a desiccant before the oxygen molecule removal step. [9] The method for removing oxygen molecules according to [8], wherein the desiccant is at least one selected from molecular sieves 3A, molecular sieves 4A, and high silica zeolite.

[0014]

[10] A method for purifying carbon monoxide by purifying the carbon monoxide-containing gas using the method for removing oxygen molecules according to any one of [1] to [9], said catalyst preparation step, said oxygen molecule removal step, a carbon dioxide removal step of removing carbon dioxide generated in the oxygen molecule removal step from the post-oxygen molecule removal gas using a carbon dioxide adsorbent to obtain a post-carbon dioxide removal gas with a reduced concentration of carbon dioxide, a pressure swing adsorption step of recovering carbon monoxide from the post-carbon dioxide removal gas by pressure swing adsorption to obtain purified carbon monoxide with a purity of 99.95% by volume or more, A method for purifying carbon monoxide comprising:

[0015]

[11] The method for purifying carbon monoxide according to

[10] , wherein the carbon dioxide adsorbent is at least one selected from molecular sieves 4A, molecular sieves 13X, activated carbon, and metal oxides.

[0016]

[12] The method for purifying carbon monoxide according to

[10] or

[11] , wherein in the carbon dioxide removal step, the concentration of carbon dioxide contained in the post-carbon dioxide removal gas is reduced to less than 50 ppm by volume.

[0017]

[13] The pressure swing adsorption step is an adsorption step of adsorbing carbon monoxide in the post-carbon dioxide removal gas to a pressure swing adsorbent containing a monovalent copper compound and zeolite under a pressure of 0.3 MPaG or more and 0.9 MPaG or less, a desorption step of placing the pressure swing adsorbent adsorbed with carbon monoxide in the adsorption step under a pressure of -0.08 MPaG or more and -0.01 MPaG or less to desorb the carbon monoxide adsorbed on the pressure swing adsorbent, The method for purifying carbon monoxide according to any one of

[10] to

[12] comprising:

Advantages of the Invention

[0018] According to the method for removing oxygen molecules according to the present invention, oxygen molecules mixed in the carbon monoxide-containing gas can be easily removed. Further, according to the method for purifying carbon monoxide according to the present invention, high-purity carbon monoxide can be obtained.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic diagram showing an example of a purification processing apparatus for explaining an embodiment of the method for purifying carbon monoxide according to the present invention, and is a diagram of a part for carrying out a catalyst preparation step, a dehydration step, an oxygen molecule removal step, and a carbon dioxide removal step. [Figure 2] It is a schematic diagram showing an example of a purification processing apparatus for explaining an embodiment of the method for purifying carbon monoxide according to the present invention, and is a diagram of a part for carrying out a pressure swing adsorption step.

Embodiments for Carrying Out the Invention

[0020] One embodiment of the present invention will be described below. Note that this embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. Further, various changes or improvements can be made to this embodiment, and forms with such changes or improvements can also be included in the present invention.

[0021] The method for removing oxygen molecules according to one embodiment of the present invention includes a catalyst preparation step and an oxygen molecule removal step. In the catalyst preparation step, a platinum catalyst containing platinum is arranged in a heat treatment container in which the pressure is maintained below atmospheric pressure, and while an inert gas is supplied to and passed through the heat treatment container, the platinum catalyst is heat-treated in the heat treatment container (that is, by heat-treating the platinum catalyst under the gas flow of the inert gas), and the moisture contained in the platinum catalyst is removed from the platinum catalyst. This heat treatment is carried out until the concentration of the moisture contained in the inert gas supplied into the heat treatment container and discharged from the heat treatment container after being used for the heat treatment becomes less than 1000 volume ppm.

[0022] The oxygen molecule removal process involves contacting a carbon monoxide-containing gas, which contains carbon monoxide and oxygen molecules as impurities, with a carbon monoxide concentration of 10% by volume or more and a water concentration of less than 1000 ppm by volume, with a platinum catalyst that has been heat-treated in the catalyst preparation process. This process removes oxygen molecules from the carbon monoxide-containing gas, obtaining a gas with a reduced oxygen molecule concentration. In the oxygen molecule removal process, oxygen molecules are removed by a reaction between one oxygen molecule and two carbon monoxide molecules, resulting in the production of two carbon dioxide (CO2) molecules. The platinum catalyst is a catalyst that promotes this oxidation-reduction reaction.

[0023] In the oxygen molecule removal process, if a platinum catalyst with a sufficiently reduced water content is used in the catalyst preparation process, it becomes possible to obtain an oxygen-removed gas from which oxygen molecules have been sufficiently removed from the carbon monoxide-containing gas. For example, an oxygen-removed gas with an oxygen molecule concentration of less than 1 ppm by volume can be obtained.

[0024] Furthermore, because platinum catalysts have a higher ability to remove oxygen molecules compared to activated carbon and other materials, it is possible to obtain oxygen-removed gas from carbon monoxide-containing gas without using large amounts of platinum catalyst. Therefore, even when industrially producing oxygen-removed gas with an oxygen molecule concentration of less than 1 volume ppm, oxygen molecules mixed in carbon monoxide-containing gas can be easily removed without using large-scale equipment.

[0025] A method for purifying carbon monoxide according to one embodiment of the present invention is a method for purifying a carbon monoxide-containing gas using the oxygen molecule removal method according to the present embodiment, comprising a catalyst preparation step, an oxygen molecule removal step, a carbon dioxide removal step, and a pressure swing adsorption step. The catalyst preparation process and the oxygen molecule removal process are as described above.

[0026] The carbon dioxide removal process involves removing the carbon dioxide generated in the oxygen molecule removal process from the gas after oxygen molecule removal using a carbon dioxide adsorbent, thereby obtaining a gas after carbon dioxide removal with a reduced carbon dioxide concentration. The pressure swing adsorption process is a process in which carbon monoxide is recovered from the gas after carbon dioxide removal by the pressure swing adsorption method to obtain purified carbon monoxide with a purity of 99.95% by volume or higher.

[0027] Since oxygen molecules are removed in the oxygen molecule removal process and carbon dioxide is removed in the carbon dioxide removal process, the amount of oxygen molecules and carbon dioxide contained in the carbon dioxide removal gas subjected to the pressure swing adsorption process is extremely small. Therefore, the carbon monoxide adsorption performance of the pressure swing adsorbent does not deteriorate easily. Consequently, carbon monoxide is adsorbed with high efficiency on the pressure swing adsorbent in the pressure swing adsorption process, making it possible to produce high-purity carbon monoxide (i.e., purified carbon monoxide with a purity of 99.95% by volume or higher).

[0028] Such high-purity carbon monoxide is suitably usable as a high-purity gas in semiconductor manufacturing processes. For example, it can be suitably used as an additive gas in the dry etching process when manufacturing silicon semiconductors for non-volatile memory such as NAND flash memory.

[0029] The method for removing oxygen molecules and purifying carbon monoxide according to this embodiment will be described in more detail below. [Platinum catalyst] The platinum catalyst used in the oxygen molecule removal method and carbon monoxide purification method according to this embodiment is not particularly limited as long as it contains platinum, but a catalyst in which platinum is supported on a carrier is preferred. The type of carrier on which the platinum is supported is not particularly limited, but it is preferable to use at least one selected from alumina (Al2O3), activated carbon, and zeolite as the carrier.

[0030] The shape of the platinum catalyst is not particularly limited; for example, it can be in the form of a powder, granules, spheres, or rings. In a platinum catalyst, the amount of platinum supported on the support (hereinafter sometimes referred to as "supported amount"), that is, the mass ratio of platinum in the platinum catalyst, may affect the oxygen molecule removal performance in the oxygen molecule removal process. The supported amount of platinum in the platinum catalyst is preferably 0.05% by mass or more and 5% by mass or less, and more preferably 0.5% by mass or more and 5% by mass or less.

[0031] If the amount of platinum supported in the platinum catalyst is within the above range, the oxygen molecule removal performance can be sufficiently high, and costs can be kept down. An example of a suitable platinum catalyst is the platinum catalyst (product code NA061RZ) manufactured by JGC Catalysts & Chemicals Co., Ltd. This platinum catalyst has platinum supported on a γ-alumina support, and is a ring-shaped tablet molded product with a platinum support amount of 0.5% by mass.

[0032] [Catalyst preparation process] In the catalyst preparation process, the platinum catalyst is heat-treated under an inert gas stream to remove moisture contained in the platinum catalyst. The heat treatment temperature is preferably between 150°C and 300°C. By performing the heat treatment under the above temperature conditions, moisture can be sufficiently removed from the platinum catalyst while suppressing a decrease in the lifespan of the platinum catalyst. The heat treatment temperature is more preferably between 170°C and 280°C, and even more preferably between 200°C and 250°C.

[0033] Furthermore, the pressure conditions for the heat treatment are preferably between -0.09 MPaG and -0.01 MPaG. By performing the heat treatment under the above pressure conditions, moisture can be sufficiently removed from the platinum catalyst. The pressure conditions for the heat treatment are more preferably between -0.09 MPaG and -0.02 MPaG, and even more preferably between -0.04 MPaG and -0.02 MPaG.

[0034] If a large amount of moisture remains in the platinum catalyst, its ability to remove oxygen molecules in the subsequent oxygen molecule removal process will decrease. Therefore, it is necessary to continue the heat treatment until the concentration of moisture in the inert gas supplied to the heat treatment vessel and discharged from the heat treatment vessel after use is less than 1000 ppm by volume.

[0035] If the water content in the inert gas discharged from the heat treatment container is 1000 ppm by volume or higher, there is a risk that a large amount of water will remain in the platinum catalyst. As a result, it may not be possible to sufficiently remove oxygen molecules from the carbon monoxide-containing gas in the oxygen molecule removal process, and it may become difficult to reduce the oxygen molecule concentration in the gas after oxygen molecule removal to, for example, less than 1 ppm by volume. The heat treatment is preferably carried out until the water content in the inert gas discharged from the heat treatment container is less than 1000 ppm by volume, and more preferably until it is less than 10 ppm by volume.

[0036] The water content in the inert gas discharged from the heat treatment container can be measured, for example, by a Fourier transform infrared spectrophotometer. Therefore, it is advisable to continuously measure the water content in the inert gas discharged from the heat treatment container using a Fourier transform infrared spectrophotometer and continue the heat treatment until the water content is less than 1000 ppm per volume. However, an appropriate heat treatment time may be predetermined based on previous experience.

[0037] The flow rate of the inert gas supplied to the heat treatment container is not particularly limited, but if the capacity of the heat treatment container is approximately 120 mL to 1200 mL, it is preferable to set the flow rate to 1 L / min or more and 10 L / min or less. By performing the heat treatment at the above flow rate, moisture can be sufficiently removed from the platinum catalyst.

[0038] The type of inert gas is not particularly limited, but it is preferably at least one selected from nitrogen molecules (N2), helium (He), and argon (Ar). The type of heat treatment container used in the catalyst preparation process is not particularly limited, but for example, tubular, rectangular, or spherical containers can be used.

[0039] [Gas containing carbon monoxide] The carbon monoxide-containing gas treated by the oxygen molecule removal method and carbon monoxide purification method according to this embodiment contains carbon monoxide and oxygen molecules as impurities, with a carbon monoxide concentration of 10% by volume or more and a water content of less than 1000 ppm by volume. Because the water content is less than 1000 ppm by volume, oxygen molecules can be sufficiently removed from the carbon monoxide-containing gas in the oxygen molecule removal step. The water content in the carbon monoxide-containing gas is preferably less than 1000 ppm by volume, and more preferably less than 10 ppm by volume.

[0040] The oxygen molecule removal performance of a platinum catalyst is affected by the concentration of carbon monoxide in the carbon monoxide-containing gas. Therefore, if the carbon monoxide concentration is 10% by volume or higher, the oxygen molecule removal performance of the platinum catalyst will be good. As a result, it becomes possible to easily remove oxygen molecules contained in the carbon monoxide-containing gas during the oxygen molecule removal process, and it becomes easier to reduce the concentration of oxygen molecules in the gas after oxygen molecule removal to less than 1 ppm by volume. The concentration of carbon monoxide in the carbon monoxide-containing gas is preferably 10% by volume or higher, and more preferably 30% by volume or higher. Furthermore, the concentration of carbon monoxide in the carbon monoxide-containing gas may be between 10% by volume and 99% by volume, and preferably between 20% by volume and 90% by volume.

[0041] The concentration of oxygen molecules in the carbon monoxide-containing gas is preferably less than 2000 ppm by volume. Since the oxygen molecule removal performance of the platinum catalyst is affected by the concentration of oxygen molecules in the carbon monoxide-containing gas, if the oxygen molecule concentration is less than 2000 ppm by volume, it becomes easier to reduce the concentration of oxygen molecules in the gas after oxygen molecule removal to less than 1 ppm by volume in the oxygen molecule removal process. The concentration of oxygen molecules in the carbon monoxide-containing gas is more preferably less than 2000 ppm by volume, and even more preferably less than 100 ppm by volume.

[0042] The carbon monoxide-containing gas may contain other components along with carbon monoxide, oxygen molecules, and water. For example, it may further contain at least one selected from hydrogen molecules (H2), nitrogen molecules, carbon dioxide, argon, helium, and methane (CH4).

[0043] [Dehydration process] In the oxygen molecule removal method and carbon monoxide purification method according to this embodiment, a dehydration step may be performed before the oxygen molecule removal step to remove moisture from the carbon monoxide-containing gas using a desiccant. Performing the dehydration step is optional, and whether or not to perform it may be decided depending on the concentration of moisture in the carbon monoxide-containing gas.

[0044] By further reducing the water content in the carbon monoxide-containing gas, it becomes easier to reduce the concentration of oxygen molecules in the gas after oxygen molecule removal to less than 1 ppm by volume during the oxygen molecule removal process. If a dehydration process is performed, even carbon monoxide-containing gas with a water content of 1000 ppm by volume or more can be subjected to the oxygen molecule removal method and carbon monoxide purification method according to this embodiment.

[0045] The type of desiccant used in the dehydration process is not particularly limited, and general desiccants can be used. For example, zeolites can be used, and specific examples include at least one selected from molecular sieves 3A, molecular sieves 4A, and high silica zeolite.

[0046] [Oxygen molecule removal process] The oxygen molecule removal step involves contacting a platinum catalyst, which has been heat-treated in the catalyst preparation step, with a carbon monoxide-containing gas to convert oxygen molecules in the carbon monoxide-containing gas into carbon dioxide, thereby obtaining a gas with reduced oxygen molecule concentration. The oxidation-reduction reaction between carbon monoxide and oxygen molecules is accelerated by the platinum catalyst, resulting in the removal of oxygen molecules from the carbon monoxide-containing gas and the generation of carbon dioxide. The above oxidation-reduction reaction is represented by the following equation. 2CO + O2 → 2CO2

[0047] In the oxygen molecule removal step, it is preferable to sufficiently remove oxygen molecules from the carbon monoxide-containing gas and reduce the concentration of oxygen molecules in the gas after oxygen molecule removal to less than 1 volume ppm, and more preferably to less than 0.1 volume ppm. This further suppresses the decrease in the carbon monoxide adsorption performance of the pressure swing adsorbent in the subsequent pressure swing adsorption step.

[0048] In the oxygen molecule removal step, a carbon monoxide-containing gas is introduced and passed through a reaction tube filled with a heat-treated platinum catalyst. It is efficient and preferable to use the same heat treatment container used in the catalyst preparation step as the reaction tube (in this specification, the reaction tube used in the oxygen molecule removal step may also be referred to as the heat treatment container). The material of the reaction tube is not particularly limited, but stainless steel is preferred.

[0049] The rate at which carbon monoxide-containing gas is introduced into the reaction tube is preferably 500 / h to 1500 / h in terms of space velocity. This allows for more reliable and efficient removal of oxygen molecules from the carbon monoxide-containing gas. The rate at which carbon monoxide-containing gas is introduced into the reaction tube (space velocity) is more preferably 500 / h to 1200 / h, and even more preferably 500 / h to 1000 / h.

[0050] The temperature conditions for contacting the carbon monoxide-containing gas with the platinum catalyst in the oxygen molecule removal process are not particularly limited, but it is preferable to set them between 100°C and 300°C. This allows for sufficient removal of oxygen molecules from the carbon monoxide-containing gas while suppressing a decrease in the lifespan of the platinum catalyst. The above temperature conditions are more preferably between 150°C and 250°C, and even more preferably between 150°C and 200°C.

[0051] The amount of platinum catalyst used in the oxygen molecule removal process (for example, the amount of platinum catalyst packed into one reaction tube) is not particularly limited, but it is preferable to use 30 g to 80 g per 1 L / min of carbon monoxide-containing gas flow rate. If the amount of platinum catalyst used in the oxygen molecule removal process is within the above range, the oxygen molecule removal performance is sufficiently high and the cost is also favorable.

[0052] The analytical method for determining the composition of carbon monoxide-containing gas and the gas after oxygen molecule removal is not particularly limited, but analytical methods using gas chromatography and Fourier transform infrared spectrophotometers can be employed. A specific example of a gas chromatograph is the Tracera gas chromatograph (trade name) manufactured by Shimadzu Corporation, and a specific example of a Fourier transform infrared spectrophotometer is the Nicolet® iS10 FT-IR Fourier transform infrared spectrophotometer manufactured by Thermo Fisher K.K.

[0053] Examples of gas chromatograph detectors include thermal conductivity detectors (TCD) and barrier discharge ionization detectors (BID). Examples of columns include MICROPACKED ST (product name) manufactured by Shinwa Chemical Co., Ltd. and CP-Molsieve 5Å manufactured by Agilent Technologies, Inc.

[0054] In the carbon monoxide purification method according to this embodiment, after performing a catalyst preparation step, a dehydration step, and an oxygen molecule removal step (the dehydration step may be omitted), a carbon dioxide removal step and a pressure swing adsorption step are performed to obtain purified carbon monoxide with a purity of 99.95% by volume or higher.

[0055] [Carbon dioxide removal process] The carbon dioxide removal process involves removing the carbon dioxide generated in the oxygen molecule removal process from the gas after oxygen molecule removal using a carbon dioxide adsorbent, thereby obtaining a gas after carbon dioxide removal with a reduced carbon dioxide concentration.

[0056] In the carbon dioxide removal process, it is preferable to keep the concentration of carbon dioxide in the gas after carbon dioxide removal below 50 ppm by volume, and more preferably below 1 ppm by volume. This allows for the acquisition of higher purity purified carbon monoxide in the subsequent pressure swing adsorption process.

[0057] The type of carbon dioxide adsorbent is not particularly limited, but at least one selected from molecular sieves 4A, molecular sieves 13X, activated carbon, and metal oxides can be used. Specific examples of metal oxides include magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), cerium oxide (CeO2), and zirconium oxide (ZrO2).

[0058] [Pressure Swing Adsorption Process] The pressure swing adsorption process is a process of recovering carbon monoxide from the gas after carbon dioxide removal by the pressure swing adsorption method to obtain purified carbon monoxide with a purity of 99.95% by volume or higher. The pressure swing adsorption process may include an adsorption process and a desorption process. The adsorption process is a process of adsorbing carbon monoxide in the gas after carbon dioxide removal onto a pressure swing adsorbent, and the desorption process is a process of desorbing carbon monoxide from the pressure swing adsorbent that has adsorbed carbon monoxide in the adsorption process.

[0059] The type of pressure swing adsorbent is not particularly limited as long as it can adsorb carbon monoxide, but pressure swing adsorbents containing a monovalent copper compound and zeolite are preferred. Specific examples of monovalent copper compounds include cuprous chloride, cuprous bromide (CuBr), and cuprous acetate (CuOAc), with cuprous chloride being more preferred. Instead of zeolite, activated carbon or alumina can be used as a support, and a pressure swing adsorbent in which a monovalent copper compound such as cuprous chloride is supported on the activated carbon or alumina can be used.

[0060] In the adsorption process, it is preferable to adsorb carbon monoxide from the gas after carbon dioxide removal onto a pressure swing adsorbent under a pressure of 0.3 MPaG to 0.9 MPaG. Performing adsorption under the above pressure conditions makes it easier to obtain purified carbon monoxide of higher purity. The above pressure conditions are more preferably 0.5 MPaG to 0.9 MPaG, and even more preferably 0.7 MPaG to 0.9 MPaG.

[0061] In the desorption process, it is preferable to desorb the carbon monoxide adsorbed on the pressure swing adsorbent, which has adsorbed carbon monoxide in the adsorption process, by placing it under a pressure of -0.08 MPaG to -0.01 MPaG. Performing desorption under the above pressure conditions makes it easier to obtain purified carbon monoxide of higher purity. The above pressure conditions are more preferably -0.06 MPaG to -0.02 MPaG, and even more preferably -0.04 MPaG to -0.02 MPaG.

[0062] Furthermore, a cleaning step may be added between the adsorption and desorption steps to clean the pressure swing adsorbent with a cleaning gas. The type of gas that can be used as the cleaning gas is not particularly limited as long as it can clean the pressure swing adsorbent, but it is also possible to use a portion of the purified carbon monoxide obtained after the pressure swing adsorption step as the cleaning gas. In addition, when a portion of purified carbon monoxide is used as the cleaning gas, the post-cleaning gas (off-gas 39) may be returned to the oxygen molecule removal step.

[0063] Next, an example of a purification apparatus capable of carrying out the carbon monoxide purification method according to this embodiment will be described with reference to Figures 1 and 2. The purification apparatus shown in Figures 1 and 2 comprises a carbon monoxide gas container 1 filled with carbon monoxide, a nitrogen gas container 2 filled with nitrogen gas, and an oxygen gas container 3 filled with oxygen gas.

[0064] Furthermore, the purification apparatus shown in Figures 1 and 2 includes a dehydration tube 13 for carrying out a dehydration process, a reaction tube 16 for carrying out a catalyst preparation process and an oxygen molecule removal process, a carbon dioxide removal tube 21 for carrying out a carbon dioxide removal process, and a pressure swing adsorption tower 30 for carrying out a pressure swing adsorption process (adsorption process and desorption process).

[0065] The reaction tube 16 is made of, for example, stainless steel and is filled with a platinum catalyst 18. The reaction tube 16 also includes a heater 19 for heating the reaction tube 16 and an insulating material 17 that covers the surface of the reaction tube 16 to provide insulation.

[0066] During the catalyst preparation process, nitrogen gas is supplied from the nitrogen gas supply line 4 through piping into the reaction tube 16 and passed through the reaction tube 16. At the same time, the pressure inside the reaction tube 16 is reduced to a predetermined level by the vacuum pump 25, and the platinum catalyst 18 inside the reaction tube 16 is heated to a predetermined temperature by the heater 19. This removes moisture from the platinum catalyst 18. Reference numeral 5 in Figure 1 indicates a check valve.

[0067] The pressure inside the reaction tube 16 can be measured by the pressure gauge 20. Furthermore, the flow rate of nitrogen gas supplied into the reaction tube 16 can be adjusted by the mass flow controller 9.

[0068] The nitrogen gas discharged from the reaction tube 16 is sent to the Fourier transform infrared spectrophotometer 24, where the concentration of water it contains can be measured. This allows for monitoring of the water content in the nitrogen gas discharged from the reaction tube 16 during the catalyst preparation process.

[0069] By flowing carbon monoxide gas, nitrogen gas, and oxygen gas from carbon monoxide gas container 1, nitrogen gas container 2, and oxygen gas container 3, respectively, and adjusting the flow rates of each gas with mass flow controllers 9, 10, and 11, a carbon monoxide-containing gas of a desired composition can be prepared. Reference numerals 6, 7, and 8 in Figure 1 indicate pressure reducing valves.

[0070] During the oxygen molecule removal process, the prepared carbon monoxide-containing gas is supplied to the reaction tube 16 via piping. This removes oxygen from the carbon monoxide-containing gas, resulting in a gas with reduced oxygen molecule concentration. Temperature and pressure can be controlled by the heater 19 and vacuum pump 25, similar to the catalyst preparation process. The flow rate (space velocity) of the carbon monoxide-containing gas can be controlled by mass flow controllers 9, 10, and 11.

[0071] When performing the dehydration process, before sending the carbon monoxide-containing gas to the reaction tube 16, it is sent to a dehydration tube 13 filled with a desiccant 14 to remove the moisture contained in the carbon monoxide-containing gas. Then, the carbon monoxide-containing gas from which the moisture has been removed is discharged from the dehydration tube 13, and this carbon monoxide-containing gas is sent to the reaction tube 16 to perform the oxygen molecule removal process.

[0072] Furthermore, if the carbon monoxide-containing gas is sent to the gas chromatograph 23 or Fourier transform infrared spectrophotometer 24 via the raw material analysis line 15 (the area enclosed by the dashed line in Figure 1) before flowing it through the dewatering tube 13 or reaction tube 16, the carbon monoxide-containing gas can be analyzed and the concentrations of each component contained in the carbon monoxide-containing gas can be measured.

[0073] Next, the gas from which oxygen molecules have been removed, discharged from the reaction tube 16, is passed through a carbon dioxide removal tube 21 filled with a carbon dioxide adsorbent 22. This carries out the carbon dioxide removal process, removing carbon dioxide from the gas from which oxygen molecules have been removed, and obtaining a gas 26 from which carbon dioxide has been removed, with a reduced concentration of carbon dioxide.

[0074] Next, the carbon dioxide-removed gas 26 is compressed to a predetermined pressure by a compressor 28 and then circulated through a pressure swing adsorption tower 30 filled with pressure swing adsorbent 31. The pressure of the compressed carbon dioxide-removed gas 26 can be measured by a pressure gauge 27. The total amount of carbon dioxide-removed gas 26 circulating through the pressure swing adsorption tower 30 can be measured by an integrated flow meter 29.

[0075] Carbon monoxide in the carbon dioxide-removed gas 26 supplied to the pressure swing adsorption tower 30 is adsorbed by the pressure swing adsorbent 31. Components other than carbon monoxide that are not adsorbed in this adsorption process are discharged from the pressure swing adsorption tower 30 and exhausted as off-gas 39. In Figure 2, reference numeral 37 denotes a pressure reducing valve, and reference numeral 38 denotes a check valve.

[0076] Once the adsorption process is complete, the cleaning gas contained in the surge tank 33 is circulated through the pressure swing adsorption tower 30, with the flow rate controlled by the mass flow controller 35 and the total amount measured by the cumulative flow meter 36, to clean the pressure swing adsorbent 31. This removes any remaining impurities in the pressure swing adsorption tower 30 (cleaning process). Note that reference numeral 34 in Figure 2 indicates a pressure gauge used to measure the pressure inside the surge tank 33.

[0077] Once the cleaning process is complete, the pressure inside the pressure swing adsorption tower 30 is reduced to a predetermined pressure using a vacuum pump 32, and carbon monoxide is desorbed from the pressure swing adsorbent 31 (desorption process). The desorbed carbon monoxide discharged from the pressure swing adsorption tower 30 is filled into the surge tank 33. A portion of the carbon monoxide filled into the surge tank 33 is recovered as purified carbon monoxide 42, and the remainder is used as a cleaning gas. In Figure 2, reference numeral 40 denotes a pressure reducing valve, and reference numeral 41 denotes a check valve. [Examples]

[0078] The present invention will be described in more detail below with reference to examples and comparative examples. [Example 1] Example 1 is an embodiment of the invention relating to a method for removing oxygen molecules. Using a purification apparatus having a configuration similar to that of the purification apparatus shown in Figure 1, a catalyst preparation step was performed to heat-treat a platinum catalyst, and an oxygen molecule removal step was performed to remove oxygen molecules from a carbon monoxide-containing gas.

[0079] The platinum catalyst used was a platinum catalyst (product code NA061RZ) manufactured by JGC Catalysts & Chemicals Co., Ltd. This platinum catalyst consists of platinum supported on a γ-alumina carrier, with a platinum load of 0.5% by mass. The catalyst is a ring-shaped tablet with dimensions of 5mm outer diameter, 2mm inner diameter, and 4mm height. Furthermore, the average crushing longitudinal strength of this platinum catalyst is 430N, and its specific surface area is 180m². 2 / g, pore volume is 0.4 cm³ 3 It is / g.

[0080] Next, the catalyst preparation process will be described. A stainless steel reaction tube with an inner diameter of 3 / 4 inch and a length of 700 mm was used as the heat treatment vessel. 70.8 g of platinum catalyst was packed into this reaction tube, and it was heated to 200°C while supplying nitrogen gas as an inert gas. The nitrogen gas supply rate was set to a space velocity of 500 / h. The pressure inside the reaction tube was then reduced using a vacuum pump to -0.02 MPaG, and the heat treatment was carried out for 3 hours under a nitrogen gas stream while maintaining this pressure. After the heat treatment was completed, the water content in the nitrogen gas discharged from the reaction tube was measured using a Fourier transform infrared spectrophotometer and was found to be less than 1 ppm by volume.

[0081] Next, the oxygen molecule removal process will be described. A carbon monoxide-containing gas containing carbon monoxide and oxygen molecules as impurities, with a carbon monoxide concentration of 10% by volume or more, was prepared as follows. First, commercially available carbon monoxide gas with a purity of 99.99% by volume or higher, commercially available industrial nitrogen gas with a purity of 99.99% by volume or higher, and commercially available industrial oxygen gas with a purity of 99.99% by volume or higher were prepared. Then, while controlling the flow rate using a mass flow controller, the carbon monoxide gas and nitrogen gas were mixed in a volume ratio of 2.0:1.0, and oxygen gas was added to this mixed gas to a concentration of 69.0 ppm by volume.

[0082] The water content of the obtained carbon monoxide-containing gas was less than 1 ppm by volume. In Example 1, the dehydration step was not performed, and the untreated carbon monoxide-containing gas was subjected to the oxygen molecule removal step. However, for convenience, in Table 1, the water content of the carbon monoxide-containing gas is listed in the column for the dehydration step. Therefore, the water content of the inlet gas and the outlet gas, which will be explained later, are the same value.

[0083] A Tracera gas chromatograph (trade name) manufactured by Shimadzu Corporation was used to analyze the composition of the prepared carbon monoxide-containing gas. A thermal conductivity detector (TCD) and a barrier discharge ionization detector (BID) were used as detectors for the gas chromatograph. In addition, the columns used were MICROPACKED ST (trade name) manufactured by Shinwa Chemical Co., Ltd. and CP-Molsieve 5Å manufactured by Agilent Technologies, Inc.

[0084] The prepared carbon monoxide-containing gas was supplied to the above-mentioned reaction tube, which was maintained at a temperature of 150°C, and brought into contact with the platinum catalyst that had been heat-treated in the catalyst preparation step. This removed oxygen molecules from the carbon monoxide-containing gas, yielding a gas with a reduced oxygen molecule concentration. At this time, the supply rate of the carbon monoxide-containing gas was 1.14 L / min (space velocity of 570 L / h) at 25°C and 0 MPaG.

[0085] The oxygen concentration in the obtained gas after oxygen molecule removal was measured to be less than 0.1 ppm by volume. Furthermore, the carbon dioxide concentration in the obtained gas after oxygen molecule removal was measured using a Fourier transform infrared spectrophotometer and was found to be 170 ppm by volume. The conditions for the catalyst preparation process and the oxygen molecule removal process, as well as the obtained results, are summarized in Table 1.

[0086] [Table 1]

[0087] [Examples 2-6, Example 9, and Comparative Examples 1-4] Except for changing the conditions for the catalyst preparation step and the oxygen molecule removal step as shown in Tables 1 and 2, oxygen molecules were removed from the carbon monoxide-containing gas in the same manner as in Example 1 to obtain the gas from which oxygen molecules have been removed. The results are shown in Tables 1 and 2.

[0088] [Table 2]

[0089] [Example 7] Except for changing the conditions for the catalyst preparation and oxygen molecule removal steps as shown in Table 1, oxygen molecules were removed from the carbon monoxide-containing gas in the same manner as in Example 1 to obtain the gas after oxygen molecule removal. The results are shown in Table 1. The platinum catalyst used was platinum catalyst (product number: NS) manufactured by JGC Universal Corporation. This platinum catalyst is granular, with a particle size of 2.5 to 4.0 mm and a packing specific gravity of 0.35 to 0.45 g / cc.

[0090] [Example 8] Except for performing a dehydration step before the oxygen molecule removal step to remove moisture from the carbon monoxide-containing gas with a desiccant, and then subjecting the dehydrated carbon monoxide-containing gas to the oxygen molecule removal step, and changing the conditions for the catalyst preparation step and the oxygen molecule removal step as shown in Table 1, oxygen molecules were removed from the carbon monoxide-containing gas in the same manner as in Example 1 to obtain the gas after oxygen molecule removal. The results are shown in Table 1.

[0091] As a desiccant, 35.5g of Molecular Sieves 3A (referred to as "MS3A" in Tables 1-3), manufactured by Union Showa Co., Ltd., was used.

[0092] Furthermore, the dewatering process is carried out by passing carbon monoxide-containing gas through a dewatering tube filled with a desiccant at an adsorption temperature of 25°C and an inflow rate of 1.14 L / min. Tables 1 to 3 show the moisture concentration of the carbon monoxide-containing gas before it is introduced into the dewatering tube (labeled "Moisture Concentration of Inlet Gas" in the table) and the moisture concentration of the carbon monoxide-containing gas after it has been dewatered by the desiccant and discharged from the dewatering tube (labeled "Moisture Concentration of Outlet Gas" in the table).

[0093] [Comparative Examples 5 and 6] Except for changing the conditions for the catalyst preparation step and the oxygen molecule removal step as shown in Table 2, oxygen molecules were removed from the carbon monoxide-containing gas in the same manner as in Example 1 to obtain the oxygen molecule-removed gas. The results are shown in Table 2. In Comparative Examples 5 and 6, activated carbon was used instead of the platinum catalyst. The activated carbon used was Granular Shirasagi (registered trademark) G2x manufactured by Osaka Gas Chemical Co., Ltd., and the amount used was 35.4 g.

[0094] As can be seen from Tables 1 and 2, in Examples 1 to 9, oxygen molecules were sufficiently removed from the carbon monoxide-containing gas, and a gas with an oxygen molecule concentration of less than 1 ppm by volume was obtained. In contrast, in Comparative Examples 1 to 6, oxygen molecules were not sufficiently removed, and it was not possible to obtain a gas with an oxygen molecule concentration of less than 1 ppm by volume.

[0095] [Example 10] Example 10 is an embodiment of the invention relating to a method for purifying carbon monoxide. Using a purification apparatus having a configuration similar to that of the purification apparatus shown in Figures 1 and 2, the catalyst preparation step, dehydration step, oxygen molecule removal step, carbon dioxide removal step, and pressure swing adsorption step were carried out.

[0096] Specifically, in the catalyst preparation step, the platinum catalyst was heat-treated; in the dehydration step, moisture was removed from the carbon monoxide-containing gas using a desiccant; and in the oxygen molecule removal step, oxygen molecules were removed from the dehydrated carbon monoxide-containing gas to obtain the gas after oxygen molecule removal. Then, in the carbon dioxide removal step, the carbon dioxide generated in the oxygen molecule removal step was removed from the gas after oxygen molecule removal using a carbon dioxide adsorbent to obtain the gas after carbon dioxide removal. Furthermore, in the pressure swing adsorption step, carbon monoxide was recovered from the gas after carbon dioxide removal by the pressure swing adsorption method to obtain purified carbon monoxide.

[0097] The catalyst preparation, dehydration, and oxygen molecule removal steps were carried out in the same manner as in Example 8. The carbon dioxide removal step will now be described. The gas after oxygen molecule removal was brought into contact with a carbon dioxide adsorbent at an inflow rate of 1.14 L / min and an adsorption temperature of 50°C to remove the carbon dioxide generated in the oxygen molecule removal step from the gas, thereby obtaining a gas after carbon dioxide removal with a reduced carbon dioxide concentration. As the carbon dioxide adsorbent, 50.3 g of Molecular Sieves 4A (indicated as "MS4A" in Table 3) manufactured by Union Showa Co., Ltd. was used.

[0098] Next, the pressure swing adsorption process will be described. First, the manufacturing method of the pressure swing adsorbent used in the pressure swing adsorption process will be described. 80.5 g of cuprous chloride manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. and 400 mL of hydrochloric acid with a concentration of 36% by mass were mixed, and then 100 g of ZSM-5 type HSZ® zeolite manufactured by Tosoh Corporation was added, and the mixture was stirred for 24 hours while being heated at 60°C. Subsequently, after filtering and washing with distilled water, the mixture was heated at 100°C for 24 hours under a nitrogen gas stream and reduced pressure using a vacuum pump to obtain a pressure swing adsorbent in which cuprous chloride was supported on the zeolite.

[0099] 110 mL of the pressure-swing adsorbent manufactured in this manner was filled into a pressure-swing adsorption tower (internal volume 1 L), and the carbon dioxide-removed gas was passed through it. Under pressurized conditions, carbon monoxide in the carbon dioxide-removed gas was adsorbed onto the pressure-swing adsorbent (adsorption process). The supply rate of the carbon dioxide-removed gas was set to a space velocity of 545 / h, the pressure inside the pressure-swing adsorption tower was 0.9 MPaG, and the supply time of the carbon dioxide-removed gas was 120 seconds. The exhaust gas from the pressure-swing adsorption tower was discharged as off-gas.

[0100] Subsequently, a cleaning gas was supplied to the pressure swing adsorption tower under atmospheric pressure to clean the pressure swing adsorbent (cleaning process). Carbon monoxide with a purity of 99.95% by volume or higher was used as the cleaning gas. The supply rate of the cleaning gas was set to a space velocity of 1090 / h, and the supply time of the cleaning gas was 60 seconds.

[0101] Finally, the pressure inside the pressure swing adsorption tower was reduced to -0.02 MPaG using a vacuum pump, and the carbon monoxide adsorbed on the pressure swing adsorbent was desorbed (desorption step). The purified carbon monoxide obtained in this way was then filled into a surge tank. The high-purity purified carbon monoxide produced in this manner was repeatedly used as the cleaning gas described above.

[0102] The purified carbon monoxide packed in the surge tank was analyzed using a gas chromatograph with a barrier discharge ionization detector and a Fourier transform infrared spectrophotometer. The purity of the carbon monoxide was found to be 99.99% by volume. The results are shown in Table 3. In addition, the trace components contained in the purified carbon monoxide were nitrogen molecules at 100 ppm by volume, carbon dioxide at less than 1 ppm by volume, water at less than 1 ppm by volume, and oxygen molecules at less than 0.1 ppm by volume.

[0103] [Table 3]

[0104] [Examples 11, 12] Purified carbon monoxide was obtained in the same manner as in Example 10, except that the pressure conditions for the adsorption step in the pressure swing adsorption process were changed as shown in Table 3. Analysis of the purified carbon monoxide in the same manner as in Example 10 showed that the purity of carbon monoxide was 99.97% by volume in both Examples 11 and 12. The results are shown in Table 3. Furthermore, the trace components contained in the purified carbon monoxide in both Examples 11 and 12 were nitrogen molecules at 300 ppm by volume, carbon dioxide at less than 1 ppm by volume, water at less than 1 ppm by volume, and oxygen molecules at less than 0.1 ppm by volume.

[0105] [Example 13] Purified carbon monoxide was obtained in the same manner as in Example 10, except that the dehydration step was omitted and the conditions for the oxygen molecule removal step were changed as shown in Table 3. Analysis of the purified carbon monoxide in the same manner as in Example 10 revealed that the purity of the carbon monoxide was 99.99% by volume. The results are shown in Table 3. In addition, the trace components contained in the purified carbon monoxide were 60 ppm by volume of nitrogen molecules, less than 1 ppm by volume of carbon dioxide, less than 1 ppm by volume of water, and less than 0.1 ppm by volume of oxygen molecules.

[0106] [Example 14] Purified carbon monoxide was obtained in the same manner as in Example 10, except that the dehydration step was omitted and the conditions for the oxygen molecule removal step were changed as shown in Table 3. Analysis of the purified carbon monoxide in the same manner as in Example 10 revealed that the purity of the carbon monoxide was 99.96% by volume. The results are shown in Table 3. In addition, the trace components contained in the purified carbon monoxide were 400 ppm by volume of nitrogen molecules, less than 1 ppm by volume of carbon dioxide, less than 1 ppm by volume of water, and less than 0.1 ppm by volume of oxygen molecules.

[0107] [Comparative Example 7] Carbon monoxide was obtained in the same manner as in Example 10, except that the carbon dioxide removal process was not performed. Analysis of the purified carbon monoxide, in the same manner as in Example 10, revealed a purity of 99.93% by volume. The results are shown in Table 3. The trace components contained in the carbon monoxide were nitrogen molecules at 600 ppm by volume, carbon dioxide at 100 ppm by volume, water at less than 1 ppm by volume, and oxygen molecules at less than 0.1 ppm by volume.

[0108] [Comparative Example 8] Carbon monoxide was obtained in the same manner as in Example 10, except that the oxygen molecule removal step and the carbon dioxide removal step were not performed. When the purified carbon monoxide was analyzed in the same manner as in Example 10, the purity of the carbon monoxide was 99.80 volume%. The results are shown in Table 3. In addition, the trace components contained in the carbon monoxide were nitrogen molecules 1978 volume ppm, carbon dioxide 2 volume ppm, water less than 1 volume ppm, and oxygen molecules 20 volume ppm.

[0109] As can be seen from Table 3, in Examples 10 to 14, highly purified carbon monoxide with a purity of 99.95% by volume or higher was obtained. In contrast, in Comparative Examples 7 and 8, the purity of the obtained carbon monoxide was less than 99.95% by volume, and it was not possible to obtain sufficiently high-purity carbon monoxide. [Explanation of symbols]

[0110] 1. Carbon monoxide gas container 2. Nitrogen gas container 3. Oxygen gas container 4. Nitrogen gas supply line 5, 38, 41... Check valves 6, 7, 8, 37, 40... Pressure reducing valves 9, 10, 11, 35... Mass flow controllers 12, 20, 27, 34... pressure gauges 13...Dehydration pipe 14. Desiccant 15. Raw material analysis line 16. Reaction tube 17. Insulation 18...Platinum catalyst 19. Heater 21. Carbon dioxide removal tube 22. Carbon dioxide adsorbent 23. Gas chromatograph 24. Fourier Transform Infrared Spectrophotometer 25, 32... Vacuum pump 26. Gas after carbon dioxide removal 28. Compressor 29, 36... Integral flow meter 30. Pressure Swing Adsorption Tower 31. Pressure Swing Adsorbent 33. Surge Tank 39.. Off-gas 42. Refined carbon monoxide

Claims

1. A catalyst preparation step comprising: placing a platinum catalyst containing platinum in a heat treatment container where the pressure is maintained below atmospheric pressure; and heating the platinum catalyst in the heat treatment container while supplying and passing an inert gas through the heat treatment container, thereby removing the water contained in the platinum catalyst; and continuing the heat treatment until the concentration of water contained in the inert gas supplied to the heat treatment container and discharged from the heat treatment container after being used for the heat treatment is 30 ppm by volume or less; An oxygen molecule removal step is performed to remove the oxygen molecules from the carbon monoxide-containing gas, which contains carbon monoxide and oxygen molecules as impurities, wherein the concentration of carbon monoxide is 20% by volume or more and 90% by volume or less, the concentration of oxygen molecules is less than 2000 ppm by volume, and the concentration of water is less than 1000 ppm by volume. A method for removing oxygen molecules, comprising the following:

2. The method for removing oxygen molecules according to claim 1, wherein the carbon monoxide-containing gas further contains at least one selected from hydrogen molecules, nitrogen molecules, carbon dioxide, argon, helium, and methane.

3. The method for removing oxygen molecules according to claim 1 or claim 2, wherein in the oxygen molecule removal step, the concentration of the oxygen molecules contained in the gas after the oxygen molecule removal is reduced to less than 1 volume ppm.

4. The method for removing oxygen molecules according to any one of claims 1 to 3, wherein in the oxygen molecule removal step, the carbon monoxide-containing gas is introduced and passed through a reaction tube filled with the heat-treated platinum catalyst, and the rate at which the carbon monoxide-containing gas is introduced into the reaction tube is 500 / h or more and 1500 / h or less in space velocity.

5. A method for removing oxygen molecules according to any one of claims 1 to 4, wherein the pressure conditions for the heat treatment in the catalyst preparation step are -0.09 MPaG or more and -0.01 MPaG or less, and the temperature conditions are 150°C or more and 300°C or less.

6. The method for removing oxygen molecules according to any one of claims 1 to 5, wherein the inert gas is at least one selected from nitrogen molecules, helium, and argon.

7. A method for removing oxygen molecules according to any one of claims 1 to 6, further comprising a dehydration step of removing moisture from the carbon monoxide-containing gas using a desiccant, prior to the oxygen molecule removal step.

8. The method for removing oxygen molecules according to claim 7, wherein the desiccant is at least one selected from molecular sieves 3A, molecular sieves 4A, and high silica zeolite.

9. A method for purifying carbon monoxide, comprising purifying the carbon monoxide-containing gas using the method for removing oxygen molecules described in any one of Claims 1 to 8, The catalyst preparation step, The oxygen molecule removal step, A carbon dioxide removal step is performed to remove the carbon dioxide generated in the oxygen molecule removal step from the gas after oxygen molecule removal using a carbon dioxide adsorbent, thereby obtaining a gas after carbon dioxide removal in which the concentration of carbon dioxide has been reduced. A pressure swing adsorption step is performed to recover carbon monoxide from the carbon dioxide-removed gas by a pressure swing adsorption method to obtain purified carbon monoxide with a purity of 99.95% by volume or higher, A method for purifying carbon monoxide, comprising [a specific component / feature].

10. The method for purifying carbon monoxide according to claim 9, wherein the carbon dioxide adsorbent is at least one selected from molecular sieves 4A, molecular sieves 13X, activated carbon, and metal oxides.

11. A method for purifying carbon monoxide according to claim 9 or claim 10, wherein in the carbon dioxide removal step, the concentration of carbon dioxide contained in the gas after carbon dioxide removal is reduced to less than 50 ppm by volume.

12. The aforementioned pressure swing adsorption process is An adsorption step in which carbon monoxide in the gas after carbon dioxide removal is adsorbed onto a pressure swing adsorbent containing a monovalent copper compound and zeolite under a pressure of 0.3 MPaG to 0.9 MPaG, The desorption step involves placing the pressure swing adsorbent, which has adsorbed carbon monoxide in the adsorption step, under a pressure of -0.08 MPaG or more and -0.01 MPaG or less to desorb the carbon monoxide adsorbed on the pressure swing adsorbent. A method for purifying carbon monoxide according to any one of claims 9 to 11, comprising:

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