Carbon molecular sieve and method for manufacturing same, and gas separation device

Abstract

A carbon molecular sieve according to one embodiment of the present invention has a spherical shape that has a ratio Sp / D of the sphericity Sp determined by a diameter method to the diameter D of 0.005 to 0.015 inclusive, while having a crushing strength per unit cross-sectional area of 20 kg / mm2 or more and a total volume of pores having a diameter of 7.8 nm or more as determined by a mercury intrusion method of 0.10 mL / g to 0.25 mL / g inclusive.

Description

Molecular sieve carbon and its manufacturing method, and gas separation apparatus

[0001] This invention relates to molecular sieve carbon, a method for producing the same, and a gas separation apparatus.

[0002] Carbon molecular sieve (CMS) is a porous carbon material whose pore opening diameter is precisely designed and controlled to match the molecular size of the target to be separated. It exhibits a velocity-type molecular sieve property that corresponds to the difference in molecular size of the adsorbate. For this reason, molecular sieve carbon is used in the separation of low molecular weight gases using pressure swing adsorption (PSA) and thermal swing adsorption (TSA) methods, and is particularly widely applied in the separation of oxygen and nitrogen in air using the PSA method.

[0003] For example, Patent Document 1 states that the full width at half maximum of the main peak of the oxygen adsorption rate constant distribution is 0.35 seconds. -1 The following conditions must be met, and the specific surface area determined by the BET method from the CO2 adsorption isotherm at 25°C must be 300 m². 2 / g or more 600m 2 A molecular sieve carbon is disclosed that has a concentration of less than / g, and selectively adsorbs oxygen from air when the target gas for separation is air.

[0004] International Publication No. 2024 / 143289

[0005] However, the molecular sieve carbon described in Patent Document 1 is in the form of a cylindrical pellet with a diameter of 2.0 mm and an aspect ratio of 1:5. In pressure swing adsorption, pressure fluctuations are repeated in short cycles, causing the adsorbent to move up and down within the adsorption tower. As a result, the cylindrical pellet-shaped molecular sieve carbon has the problem of generating fine powder due to wear of the material.

[0006] This invention has been made in view of the above problems, and aims to provide molecular sieve carbon that exhibits high gas separation performance and gas adsorption performance while suppressing the generation of fine powder due to wear, cracking, and chipping of the material, as well as a method for producing the same and a gas separation apparatus.

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by a specific molecular sieve carbon, a method for producing the same, and a specific gas separation device, and have accomplished the present invention.

[0008] The present invention includes the following embodiments. [1] A spherical particle having a ratio Sp / D of sphericity Sp determined by the diameter method to diameter D of 0.005 or more and 0.015 or less, and having a crushing strength per unit cross-sectional area of 20 kg / mm 2 or more, wherein a total volume of pores having a diameter of 7.8 nm or more determined by mercury porosimetry is 0.10 mL / g or more and 0.25 mL / g or less. Molecular sieve carbon.

[0009] [2] A spherical particle having a ratio Sp / D of sphericity Sp determined by the diameter method to diameter D of 0.005 or more and 0.015 or less, and having a crushing strength per unit cross-sectional area of 20 kg / mm 2 or more, wherein a total volume of pores having an inlet diameter of 0.37 nm or more and less than 0.46 nm determined by a molecular probe method is 0.150 mL / g or more, and a total volume of pores having an inlet diameter of 0.46 nm or more determined by the molecular probe method is 0.030 mL / g or less. Molecular sieve carbon.

[0010] [3] The molecular sieve carbon according to [1] or [2], wherein an average pore diameter determined by mercury porosimetry is 30 nm or more and 100 nm or less.

[0011] [4] The specific surface area determined by the BET method from an adsorption isotherm of CO 2 / g or more and 350 m 2 / g or less. The molecular sieve carbon according to [1] or [2].[

[0012] [5] The molecular sieve carbon according to [1] or [2], which selectively adsorbs oxygen from a mixed gas containing at least oxygen and nitrogen.

[0013] [6] The molecular sieve carbon according to [1] or [2], which selectively adsorbs one or more gases from a mixed gas containing at least two gases selected from the group consisting of nitrogen, carbon dioxide, methane, ethane, ethylene, propylene, and propane.

[0014] A method for producing molecular sieve carbon according to [7] [1] or [2], comprising the steps of carbonizing a raw material to obtain a carbide and calcining the carbide.

[0015] [8] A gas separation apparatus for separating oxygen from air by pressure swing adsorption, wherein the apparatus comprises molecular sieve carbon described in [1] or [2] as the adsorbent in the pressure swing adsorption method.

[0016] [9] A gas separation apparatus for separating one or more gases from a mixed gas containing at least two gases selected from the group consisting of nitrogen, carbon dioxide, methane, ethane, ethylene, propylene, and propane by pressure swing adsorption, wherein the apparatus comprises molecular sieve carbon as described in [1] or [2] as the adsorbent in the pressure swing adsorption method.

[0017]

[10] A gas separation apparatus for separating oxygen from air by a temperature swing adsorption method, wherein the apparatus comprises molecular sieve carbon described in [1] or [2] as the adsorbent in the temperature swing adsorption method.

[0018]

[11] A gas separation apparatus for separating one or more gases from a mixed gas containing at least two gases selected from the group consisting of nitrogen, carbon dioxide, methane, ethane, ethylene, propylene, and propane by a temperature swing adsorption method, wherein the apparatus comprises molecular sieve carbon as described in [1] or [2] as the adsorbent in the temperature swing adsorption method.

[0019] According to the present invention, it is possible to provide molecular sieve carbon that exhibits high gas separation performance and gas adsorption performance while suppressing the generation of fine powder due to wear, cracking, and chipping of the material, as well as a method for producing the same and a gas separation apparatus.

[0020] Figure 1 shows a schematic diagram of a pore volume measurement apparatus using the molecular probe method. Figure 2 shows a schematic diagram of a gas separation apparatus that separates gases using the pressure swing method. Figure 3 shows a schematic diagram of an adsorption rate measurement apparatus.

[0021] Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. It should be noted that the following present embodiment is an example for illustrating the present invention, and the present invention is not limited only to the present embodiment.

[0022] [Molecular sieve carbon] The molecular sieve carbon of the present embodiment is spherical with a ratio Sp / D of sphericity Sp determined by the diameter method to diameter D of 0.005 or more and 0.015 or less, and has a crushing strength per unit cross-sectional area of 20 kg / mm 2 or more. The smaller the value of the ratio Sp / D, the closer the molecular sieve carbon is to a true sphere. Further, in the molecular sieve carbon of the present embodiment, the total volume of pores having a diameter of 7.8 nm or more determined by mercury intrusion porosimetry may be 0.10 mL / g or more and 0.25 mL / g or less.

[0023] When the molecular sieve carbon has such a configuration, the number of corners that serve as starting points for wear, cracking and chipping of the material is reduced, the strength of the material is increased, and the intraparticle voids that cause cracking and chipping of the material are reduced. Thereby, the generation of fine powder due to wear, cracking and chipping of the material is suppressed, and the gas separation performance and gas adsorption performance are improved. In addition, when the above ratio Sp / D is 0.015 or less, the molecular sieve carbon of the present embodiment has a high packing density, and the packing amount per unit volume is increased. Therefore, this effect also improves the gas separation performance and gas adsorption performance of the molecular sieve carbon.

[0024] On the other hand, it is technically extremely difficult to produce molecular sieve carbon having the above ratio Sp / D of less than 0.005. In addition, when the above ratio Sp / D exceeds 0.015, the number of corners that serve as starting points for wear, cracking and chipping of the material increases, so fine powder is likely to be generated due to wear, cracking and chipping of the material. In addition, when the above ratio Sp / D exceeds 0.015, the packing density cannot be sufficiently increased, resulting in insufficient gas separation performance and gas adsorption performance. Furthermore, when the crushing strength is less than 20 kg / mm 2 , the strength of the material is low, so fine powder is likely to be generated due to wear, cracking and chipping of the material.

[0025] The ratio Sp / D of molecular sieve carbon is preferably 0.005 to 0.0135, and more preferably 0.005 to 0.012. Having the ratio Sp / D within this range further suppresses the generation of fine powder due to material wear, cracking, and chipping, and further improves packing density. This, in turn, improves gas separation performance and gas adsorption performance. The method for determining the ratio Sp / D will be described later.

[0026] The crushing strength per unit cross-sectional area of ​​molecular sieve carbon is 20.5 kg / mm². 2 Preferably, it is 21 kg / mm² or more. 2 It is more preferable that the above conditions are met. Having a crushing strength per unit cross-sectional area within the above range further suppresses the generation of fine powder due to wear, cracking, and chipping of the material. Furthermore, the crushing strength per unit cross-sectional area of ​​molecular sieve carbon is 50 kg / mm². 2 The following is preferable: Such molecular sieve carbon has a crush strength of 50 kg / mm². 2 Compared to the case of "super," manufacturing is easier. The method for determining the crushing strength per unit cross-sectional area will be described later.

[0027] The total volume of pores with a diameter of 7.8 nm or more, determined by the mercury intrusion method of molecular sieve carbon, is preferably 0.10 mL / g or more, more preferably 0.11 mL / g or more, and even more preferably 0.12 mL / g or more. Having the total volume of pores with a diameter of 7.8 nm or more within the above range prevents the macropore volume, which is the site of gas mass transport, from becoming too small, thereby further improving gas separation performance. The total volume of pores with a diameter of 7.8 nm or more, determined by the mercury intrusion method of molecular sieve carbon, is preferably 0.25 mL / g or less, more preferably 0.24 mL / g or less, and even more preferably 0.23 mL / g or less. Having the total volume of pores with a diameter of 7.8 nm or more within the above range reduces the number of voids that cause cracking and chipping of the material, thereby further suppressing the generation of fine powder. The method for determining the total volume of pores with a diameter of 7.8 nm or more by the mercury intrusion method will be described later.

[0028] The total volume of pores with an entrance diameter of 0.37 nm or more and less than 0.46 nm, as determined by molecular probe method of molecular sieve carbon, is preferably 0.150 mL / g or more, more preferably 0.220 mL / g or more, and even more preferably 0.225 mL / g or more. By having the total volume of pores with an entrance diameter of 0.37 nm or more and less than 0.46 nm within the above range, the gas separation performance can be further improved.

[0029] The total volume of pores with an entrance diameter of 0.46 nm or larger, as determined by the molecular probe method for molecular sieve carbon, is preferably 0.030 mL / g or less, more preferably 0.025 mL / g or less, and even more preferably 0.020 mL / g or less. Since pores with an entrance diameter of 0.46 nm or larger are not suitable for gas separation, the gas separation performance of molecular sieve carbon does not easily decrease even if the total volume is small within the above range. Furthermore, by having the total volume of pores with an entrance diameter of 0.46 nm or larger within the above range, the amount of voids that cause cracking and chipping of the material is reduced, thereby further suppressing the generation of fine powder.

[0030] The average pore size of molecular sieve carbon, as determined by the mercury intrusion method, is preferably 30 nm to 100 nm, more preferably 35 nm to 70 nm, and even more preferably 37 nm to 65 nm. Having the average pore size within this range optimizes the size of the macropores, which are the sites for gas mass transport, thereby further improving gas separation performance. The method for determining the average pore size by the mercury intrusion method will be described later.

[0031] The specific surface area of ​​molecular sieve carbon, determined by the BET method from the CO2 adsorption isotherm at 25°C, is 350 m². 2 It is preferable that it be 370 m or more per g. 2 It is more preferable that the amount is 390m or more per gram. 2 It is even more preferable that the specific surface area is greater than or equal to / g. Having a specific surface area within the above range increases the amount of gas adsorbed, thereby further improving gas separation performance and gas adsorption performance. The specific surface area determined by the BET method from the CO2 adsorption isotherm at 25°C is 600 m². 2 It is preferable that it be less than or equal to 580m 2It is more preferable that it be less than or equal to 560m 2 It is even more preferable that the specific surface area be less than or equal to / g, as having a specific surface area within the above range makes the size of the pores, which are the gas adsorption sites, suitable for gas adsorption, thereby further improving gas separation performance and gas adsorption performance. The method for determining the specific surface area by the BET method from the CO2 adsorption isotherm at 25°C will be described later.

[0032] (Applications) The molecular sieve carbon of this embodiment is suitable for selectively adsorbing specific molecules from a mixed gas due to the above configuration.

[0033] For example, the molecular sieve carbon of this embodiment may selectively adsorb oxygen from a mixed gas containing at least oxygen and nitrogen.

[0034] For example, the molecular sieve carbon of this embodiment may selectively adsorb one or more gases from a mixed gas containing at least two gases selected from the group consisting of nitrogen, carbon dioxide, methane, ethane, ethylene, propylene, and propane.

[0035] [Method for producing molecular sieve carbon] The molecular sieve carbon of this embodiment can be obtained, for example, by any one or any combination of the following methods: thermal decomposition, activation, coating, and vapor deposition.

[0036] For the production method of molecular sieve carbon, coating and vapor deposition methods are preferred. Using these production methods tends to make it easier to produce the molecular sieve carbon of this embodiment.

[0037] A method for producing molecular sieve carbon includes a carbonization step of carbonizing a raw material to obtain a carbide, and a calcination step of calcining the carbide. The method for producing molecular sieve carbon may also include an activation step between the carbonization step and the calcination step, in which case the calcination step involves calcining the activated product obtained in the activation step.

[0038] (Carbonization process) The raw materials are not particularly limited as long as they are materials from which the desired molecular sieve carbon can be obtained. Examples include styrene-divinylbenzene copolymer resins, ion exchange resins, polyacrylonitrile, phenolic resins, polyvinylidene chloride, polycarbonate, and synthetic resins such as polyvinyl alcohol.

[0039] Since the molecular sieve carbon of this embodiment tends to be easier to produce, the raw materials preferably include at least one selected from the group consisting of styrene-divinylbenzene copolymer resin, ion exchange resin, and phenol resin, and more preferably include an ion exchange resin. The type of ion exchange resin may be a porous type having a network structure with many fine pores, or a gel type having a nearly uniform polymer structure with few fine pores. Porous ion exchange resins tend to make the molecular sieve carbon of this embodiment easier to produce due to having many fine pores. Furthermore, the functional group of the ion exchange resin may be a cationic sulfo group or carboxyl group, an anionic primary amine or polyamine, or a chelate type iminodiacetic acid or methylglucamine. When the functional group contains a nitrogen atom, such as a primary amine, polyamine, iminodiacetic acid, or methylglucamine, the resin may melt during the carbonization process. Therefore, the functional group of the ion exchange resin is preferably a sulfo group or a carboxyl group, and it is more preferable that the functional group of the ion exchange resin is a sulfo group, as this tends to make it easier to produce molecular sieve carbon in this embodiment. The reason why the resin melts in the carbonization process when nitrogen atoms are present is not clear, but it is presumed that the presence of nitrogen in the thermal decomposition and condensation of the resin in the carbonization process inhibits the progress of the intermolecular crosslinking reaction, causing the resin to melt when the polystyrene main chain is cleaved. For this reason, a porous type ion exchange resin with a sulfo group as its functional group is particularly preferred as a raw material.

[0040] The method for carbonizing the raw material is not particularly limited, and one example is heating under oxygen-free conditions. The final heating temperature in carbonization is, for example, 300°C to 1000°C, preferably 500°C to 950°C.

[0041] The carbonization time can be appropriately set depending on the raw materials and the equipment used for carbonization. For example, the carbonization time is 15 minutes to 20 hours, preferably 30 minutes to 10 hours. The carbonization process can be carried out using known manufacturing equipment such as a rotary kiln. The carbonization process may also be carried out under reduced pressure with the air removed, or under a nitrogen atmosphere.

[0042] The heating rate during carbonization can be appropriately set depending on the raw materials and the equipment used for carbonization. For example, the heating rate is 1°C / min to 100°C / min, preferably 3°C / min to 50°C / min, and more preferably 5°C / min to 15°C / min.

[0043] The carbonization process described above yields the raw material carbonized material. After carbonization, the carbonized material may be subjected to washing and / or drying treatments. These conditions are not particularly limited, and known conditions can be used.

[0044] (Activation Process) Known methods can be used for the activation process. Examples of such methods include activation using active gases such as steam, oxygen, and carbon dioxide. Known manufacturing equipment such as rotary kilns and fluidized bed furnaces can be used for the activation process. The activation process may also be carried out under reduced pressure with the air removed, or under a nitrogen atmosphere. As an example of the activation process, when steam is used, a method may be used in which the steam is brought into contact with the carbide at a flow rate of 10 liters (L) or more and 300 liters (L) or less per minute for a period of 1 minute or more and 1440 minutes or less.

[0045] The activation temperature is not particularly limited, but it is preferably 750°C to 1200°C, and more preferably 800°C to 1100°C, as this tends to make it easier to produce molecular sieve carbon in this embodiment.

[0046] The partial pressure of the active gas is, for example, 10% to 100%, preferably 30% to 100%.

[0047] The activation time can be appropriately set depending on conditions such as the raw materials, activation temperature, and manufacturing equipment. For example, the activation time is 30 minutes to 48 hours, preferably 60 minutes to 36 hours, and more preferably 70 minutes to 24 hours.

[0048] After the activation treatment, washing and / or drying treatments may be performed. These conditions are not particularly limited, and known conditions can be used.

[0049] (Casturing process) In the calcination process, the carbide obtained in the carbonization process or the activated material obtained in the activation process is calcined. By performing the calcination process, the pore size distribution of the carbide or activated material is adjusted, and molecular sieving ability is exhibited.

[0050] One method of calcination is to bring a carbon source into contact with a carbide or activated material and calcinate it. Examples of calcination methods include coating and vapor deposition.

[0051] Examples of carbon sources used in coating or vapor deposition methods include coal tar, anhydrous tar, coal tar-based pitch, petroleum-based pitch, and creosote oil. Examples of carbon sources used in pyrolysis and vapor deposition methods include alcohols such as methanol and ethanol; esters such as ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane; amides such as dimethylformamide; and polyhydric alcohols such as ethylene glycol.

[0052] Since the pore size distribution of the carbide or activator can be more easily adjusted and the pore size distribution of molecular sieve carbon can be made more uniform, in the coating method or vapor deposition method, when the carbon source is benzene and the calcination temperature is 600°C or higher and 900°C or lower, the lower limit of the amount of benzene used is usually 1.0 part by mass or more, preferably 1.5 parts by mass or more, more preferably 2.0 parts by mass or more, even more preferably 2.5 parts by mass or more, and even more preferably 3.0 parts by mass or more, per 100 parts by mass of the carbide or activator. The upper limit of the amount of benzene used is usually 10 parts by mass or less, preferably 9.0 parts by mass or less, more preferably 8.5 parts by mass or less, even more preferably 8.0 parts by mass or less, and even more preferably 7.5 parts by mass or less, per 100 parts by mass of the carbide or activator.

[0053] Since the pore size distribution of the carbide or activated material can be more easily adjusted, and the pore size distribution of molecular sieve carbon can be made more uniform, the firing temperature is usually 600°C to 900°C, more preferably 700°C to 800°C.

[0054] The firing time can be appropriately determined according to the firing temperature, for example, between 15 minutes and 240 minutes.

[0055] The calcination process can be carried out, for example, under a nitrogen atmosphere, an argon atmosphere, or another inert gas atmosphere. The calcination process may also be carried out while a carbon source is circulated through these gases as carrier gases. Benzene is preferred as the carbon source circulated through the carrier gas.

[0056] After the firing process, washing and / or drying treatments may be performed. These conditions are not particularly limited, and known conditions can be used.

[0057] [Gas Separation Apparatus] The gas separation apparatus of this embodiment is an apparatus for separating specific molecules from a mixed gas by pressure swing adsorption or temperature swing adsorption. By incorporating the molecular sieve carbon described above, the gas separation apparatus of this embodiment can efficiently separate and recover specific molecules from a mixed gas. Such a gas separation apparatus may have the same configuration as a conventional gas separation apparatus, except for the inclusion of the molecular sieve carbon described above.

[0058] Specifically, the following gas separation apparatuses can be mentioned. The gas separation apparatus of this embodiment is a gas separation apparatus for separating oxygen from air by a pressure swing adsorption method, and may be equipped with the above-mentioned molecular sieve carbon as the adsorbent in the pressure swing adsorption method.

[0059] The gas separation apparatus of this embodiment is a gas separation apparatus for separating one or more gases from a mixed gas containing at least two gases selected from the group consisting of nitrogen, carbon dioxide, methane, ethane, ethylene, propylene, and propane by pressure swing adsorption, and may include molecular sieve carbon as the adsorbent in the pressure swing adsorption method.

[0060] The gas separation apparatus of this embodiment is a gas separation apparatus for separating oxygen from air by a temperature swing adsorption method, and may include molecular sieve carbon as the adsorbent in the temperature swing adsorption method.

[0061] The gas separation apparatus of this embodiment is a gas separation apparatus for separating one or more gases from a mixed gas containing at least two gases selected from the group consisting of nitrogen, carbon dioxide, methane, ethane, ethylene, propylene, and propane by a temperature swing adsorption method, and may include molecular sieve carbon as the adsorbent in the temperature swing adsorption method.

[0062] The molecular sieve carbon of this embodiment is suitable as an adsorbent in a gas separation apparatus using the pressure swing adsorption method because it can further suppress the generation of fine powder due to wear, cracking, and chipping of the material. The adsorbent may be formed solely of molecular sieve carbon, or it may be formed by combining it with other known components.

[0063] Next, using Figure 2, an example of a gas separation apparatus for separating oxygen from air, which includes molecular sieve carbon as the adsorbent in the pressure swing adsorption method, will be described.

[0064] As shown in Figure 2, the gas separation apparatus consists of, for example, adsorption towers A and B filled with molecular sieve carbon, a compressor 11 for pressurizing raw air, a raw material tank 12 for storing raw air, a product tank 17 for storing product gas, valves 13a, 13b, 14a, and 14b for opening and closing to switch the processes of adsorption towers A and B, valves 16a and 16b for sending product gas generated from the adsorption towers to the product tank, a pressure equalization valve 15, a product gas extraction valve 18, and an exhaust port 19 for exhausting the adsorbed gas.

[0065] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way by these examples.

[0066] [Example 1] (Carbonization Process) A spherical porous-type ion exchange resin (Resinex AF-CP manufactured by Jacobi Resins) was heated in a rotary kiln while removing air, from room temperature to a final temperature of 850°C at a heating rate of 15°C / min, and then held at 850°C for 1 hour to carbonize the ion exchange resin. The total volume of pores with a diameter of 7.8 nm or more in this porous-type ion exchange resin, as determined by the mercury intrusion method, was 0.20 mL / g.

[0067] (Casturing process) Next, 100 parts by mass of the obtained carbide were passed through a rotary kiln at 800°C with 7.5 parts by mass of benzene for 120 minutes using 200 L / min of nitrogen as a carrier gas. After that, the calcined material was removed into a container that maintained a nitrogen atmosphere to avoid combustion, and cooled to room temperature under the nitrogen atmosphere. Spherical molecular sieve carbon was obtained through this calcination process.

[0068] [Example 2] Spherical molecular sieve carbon was obtained in the same manner as in Example 1, except that the final temperature in the carbonization process was set to 950°C.

[0069] [Example 3] Spherical molecular sieve carbon was obtained in the same manner as in Example 1, except that the heating rate in the carbonization process was set to 5°C / min.

[0070] [Example 4] Spherical molecular sieve carbon was obtained in the same manner as in Example 2, except that the heating rate in the carbonization process was set to 5°C / min.

[0071] [Comparative Example 1] Based on Japanese Patent No. 7454199, cylindrical pellet-shaped molecular sieve carbon was produced as follows. Specifically, coconut shells were heated in a rotary kiln for approximately 5 hours while removing air until the final temperature reached 800°C, thereby carbonizing the coconut shells. 100 parts by mass of the coconut shell carbon was pulverized in a pulverizer until the average particle size (D50) was 0.1 mm or less to obtain coconut shell carbon powder. 100 parts by mass of this coconut shell carbon powder was mixed with 20 parts by mass of water and then with 40 parts by mass of coal tar. The resulting mixture was filled into an extruder and molded into cylindrical pellets with a diameter of 2.0 mm and an aspect ratio of 1:5. The resulting cylindrical pellets were heated in a rotary kiln for approximately 5 hours while removing air until the final temperature reached 800°C. Subsequently, the cylindrical pellets were exposed to steam at a flow rate of 100 liters per minute for 100 minutes to perform an activation treatment and obtain an activated material. Next, 100 parts by mass of the obtained activated material were passed through a rotary kiln at 800°C with 7.5 parts by mass of benzene over 120 minutes using 200 L / min of nitrogen as the carrier gas. After that, the calcined material was removed into a container that maintained a nitrogen atmosphere to avoid combustion, and cooled to room temperature under the nitrogen atmosphere. This calcination process yielded cylindrical pellet-shaped molecular sieve carbon.

[0072] [Comparative Example 2] Cylindrical pellet-shaped molecular sieve carbon was obtained in the same manner as in Comparative Example 1, except that the aspect ratio was set to 1:3.

[0073] [Comparative Example 3] (Carbonization Process) A spherical gel-type ion exchange resin (Resinex AF-CG, manufactured by Jacobi Resins) was heated in a rotary kiln while removing air, from room temperature to a final temperature of 850°C at a heating rate of 15°C / min, and then held at 850°C for 1 hour to carbonize the ion exchange resin. The total volume of pores with a diameter of 7.8 nm or more, as determined by the mercury intrusion method for this gel-type ion exchange resin, was 0.02 mL / g.

[0074] (Casturing Process) Next, 100 parts by mass of the obtained carbide were passed through a rotary kiln at 800°C with 7.5 parts by mass of benzene over 120 minutes using 200 L / min of nitrogen as a carrier gas. After that, the calcined material was removed into a container that maintained a nitrogen atmosphere to avoid combustion, and cooled to room temperature under the nitrogen atmosphere. Spherical molecular sieve carbon was obtained through this calcination process.

[0075] [Comparative Example 4] Spherical molecular sieve carbon was obtained in the same manner as in Comparative Example 3, except that the final temperature in the carbonization process was set to 950°C.

[0076] [Comparative Example 5] A spherical porous ion exchange resin (Resinex PFCR-1 manufactured by Jacobi Resins) was heated in a rotary kiln while removing air, from room temperature to a final temperature of 850°C at a heating rate of 15°C / min, and then held at 850°C for 1 hour to carbonize the ion exchange resin. The total volume of pores with a diameter of 7.8 nm or more, as determined by the mercury intrusion method for this porous ion exchange resin, was 0.15 mL / g.

[0077] [Comparative Example 6] A spherical gel-type ion exchange resin (Resinex PFCR-2 manufactured by Jacobi Resins) was heated in a rotary kiln while removing air, from room temperature to a final temperature of 850°C at a heating rate of 15°C / min, and then held at 850°C for 1 hour to carbonize the ion exchange resin. The total volume of pores with a diameter of 7.8 nm or more, as determined by the mercury intrusion method for this gel-type ion exchange resin, was 0.01 mL / g.

[0078] [Comparative Example 7] A spherical porous ion exchange resin (Resinex CH-23, manufactured by Jacobi Resins) was heated in a rotary kiln while removing air, from room temperature to a final temperature of 850°C at a heating rate of 15°C / min, and then held at 850°C for 1 hour to carbonize the ion exchange resin. The total volume of pores with a diameter of 7.8 nm or more, as determined by the mercury intrusion method for this porous ion exchange resin, was 0.15 mL / g.

[0079] [Comparative Example 8] A spherical porous ion exchange resin (Resinex KW-H, manufactured by Jacobi Resins) was heated in a rotary kiln while removing air, from room temperature to a final temperature of 850°C at a heating rate of 15°C / min, and then held at 850°C for 1 hour to carbonize the ion exchange resin. The total volume of pores with a diameter of 7.8 nm or more, as determined by the mercury intrusion method for this porous ion exchange resin, was 0.15 mL / g.

[0080] [Evaluation Method] [Ratio of sphericity Sp to diameter D determined by diameter method Sp / D] The ratio Sp / D was determined as follows. First, the molecular sieve carbon obtained in the examples and comparative examples was reduced to approximately 20 particles using a dichotomizer (manufactured by Tsutsui Chemical Instruments Co., Ltd.). The reduced molecular sieve carbon was observed using an electron microscope (JEOL Ltd. JCM-7000) and accompanying software (JEOL Ltd. SEM Operation EZ). For each particle, a straight line was drawn starting from an arbitrary point on the outer circumference of the particle and passing through approximately the center of the particle. The intersection of the straight line and the outer circumference of the particle was defined as the endpoint, and the length D of the straight line from the starting point to the endpoint was defined. 1#1 The following was measured. The same procedure was performed four times on the same particle, changing the starting position each time. 1#1 , D 1#2 , D 1#3 , and D 1#4 D was obtained. 1#1 ~D 1#4 The average value of, i.e., (D 1#1 +D 1#2 +D 1#3 +D 1#4 The diameter D1 of one particle was set to ) / 4. The same operation was performed for all the reduced molecular sieve carbon particles. That is, D 2#1 , D 2#2 , D 2#3 , D 2#4 ...D N#4 Measure D1, D2, ..., D N The following was obtained. N is the number of particles after reduction. D1 to D N The average value, i.e., (D1 + D2 + ... + D N The diameter D of the molecular sieve carbon was defined as ) / N. Next, the sphericity Sp was determined using a known diameter method as follows: That is, D 1#1, D 1#2 , D 1#3 , D 1#4 The maximum value among them is D 1#max , the minimum value is D 1#min Let the sphericity Sp1 of one particle be Sp1 = {(D 1#max -D 1#min This was calculated using ) / 2}. The same operation was performed for all the reduced particles, and Sp1, Sp2, ..., Sp N Obtained. Sp1-Sp N The average value, i.e., (Sp1 + Sp2 + ... + Sp N The sphericity Sp, determined by the diameter method, was defined as () / N. The ratio Sp / D was obtained by dividing the sphericity Sp obtained by the diameter method by the diameter D.

[0081] [Crushing Strength per Unit Cross-Section] The crushing strength per unit cross-sectional area was determined as follows. First, the molecular sieve carbon obtained in the examples and comparative examples was reduced to approximately 20 particles using a dichotomizer (manufactured by Tsutsui Chemical Instruments Co., Ltd.). For each particle after reduction, the crushing strength F(N) of the molecular sieve carbon was measured using a Kiya hardness tester (manufactured by Fujiwara Seisakusho Co., Ltd., model number 043019-A). The above measurement was performed for all the molecular sieve carbon after reduction, and the average value F was calculated. ave (N) was found. F ave (N) is the cross-sectional area of ​​molecular sieve carbon π(D / 2) 2 F divided by ave / (π(D / 2) 2 ) (N / mm 2 This was determined as the crushing strength per unit cross-sectional area of ​​molecular sieve carbon.

[0082] [Total volume of pores with a diameter of 7.8 nm or larger determined by mercury intrusion method] Using Micromeritics' AutoPore IV 9500, the cumulative pore volume at a pressure of 27,500 psia was determined by mercury intrusion method, and this was taken as the total volume of pores with a diameter of 7.8 nm or larger. The measurements were performed under the following conditions. Pressure Table Filling Pressure: 1.500 psi 1st point: 1.70 psi 2nd point: 2.00 psi 3rd point: 2.30 psi 4th point: 2.60 psi 5th point: 3.00 psi 6th point: 3.50 psi 7th point: 4.00 psi 8th point: 5.50 psi 9th point: 7.00 psi 10th point: 8.50 psi 11th point: 10.5 psi 12th point: 13.0 psi 13th point: 14.7 psi 14th point: 16.0 psi 15th point: 18.0 psi 16th point: 20.0 psi 17th point: 25.0 psia 18th point: 30.0 psia 19th point: 40.0 psia 20th point: 50.0 psia 21st point: 60.0 psia 22nd point: 75.0 psia 23rd point: 90.0 psia 24th point: 115 psia 25th point: 140 psia 26th point: 175 psia 27th point: 220 psia 28th point: 270 psia 29th point: 330 psia 30th point: 420 psia 31st point: 525 psia 32nd point: 645 psia 33rd point: 800 psia 34th point: 990 psia 35th point: 1200 psia 36th point: 1400 psia 37th point: 1600 psia 38th point: 1900 psia 39th point: 2300 psia 40th point: 2630 psia 41st point: 3030 psia 42nd point: 3500 psia 43rd point: 4030 psia 44th point: 4600 psia 45th point: 5400 psia 46th point: 6200 psia 47th point: 7100 psia 48th point: 8200 psia 49th point: 9500 psia 50th point: 10900 psia 51st point: 12600 psia52nd point: 14500 psia 53rd point: 16700 psia 54th point: 19200 psia 55th point: 22200 psia 56th point: 25200 psia 57th point: 27500 psia 58th point: 31000 psia 59th point: 32000 psia 60th point: 33000 psia 61st point: 34000 psia Mercury Properties Advancing contact angle: 140,000 degrees Receding contact angle: 140,000 degrees Hg surface Tension: 480,000 dynes / cm Hg Density: The density of mercury at room temperature was measured using a mercury thermometer. Compressibility Coefficians Liner: -2.7400e-07 (1 / psia) Quadratic: +2.8500e-13 (1 / psia) 2 ) Low pressure Equilibration: 20secs High pressure Equilibration: 20secs

[0083] [Average pore size determined by mercury intrusion method] The average pore size (nm) was determined by the mercury intrusion method using an AutoPore IV 9500 from Micromeritics. The measurement conditions were as described above.

[0084] [Total volume of pores with an entrance diameter of 0.37 nm or more and less than 0.46 nm, and total volume of pores with an entrance diameter of 0.46 nm or more, determined by molecular probe method] In this specification, "molecular probe method" refers to a method for determining the total volume of pores having an entrance diameter greater than or equal to the minimum molecular diameter by adsorbing gas molecules with known minimum molecular diameter and density onto molecular sieve carbon and measuring the amount of adsorption. Specifically, the total volume of pores with an entrance diameter of 0.37 nm or more and less than 0.46 nm, and the total volume of pores with an entrance diameter of 0.46 nm or more, determined by molecular probe method of molecular sieve carbon were determined by the following procedure.

[0085] First, as shown in Figure 1, a petri dish 24 filled with carbon disulfide (minimum molecular diameter: 0.37 nm, density: 1.263 g / mL) was placed in a glass container 20 having pinholes 21. A weighing bottle 22 containing the molecular sieve carbon sample was then placed on top of the petri dish 24 via a perforated plate 23. The glass container 20 was placed in a constant temperature bath at 25°C for 24 hours to allow the carbon disulfide to adsorb onto the molecular sieve carbon. The equilibrium adsorption amount A (g / g) of carbon disulfide per gram of molecular sieve carbon was determined from the change in mass of the molecular sieve carbon before and after adsorption. Since the minimum molecular diameter of carbon disulfide is 0.37 nm and the density of carbon disulfide is 1.263 g / mL, the total volume A' (mL / g) of pores with an entrance diameter of 0.37 nm or more was calculated as A' = A / 1.263.

[0086] By replacing carbon disulfide with chloroform and measuring using the same procedure as above, the equilibrium adsorption amount B (g / g) of chloroform per gram of molecular sieve carbon was determined. Since the minimum molecular diameter of chloroform is 0.46 nm and the density of chloroform is 1.410 g / mL, the total volume B' (mL / g) of pores with an entrance diameter of 0.46 nm or larger was calculated as B' = B / 1.410.

[0087] Using the calculated values ​​A' and B', the total volume (mL / g) of pores with an entrance diameter of 0.37 nm or more and less than 0.46 nm was determined by A' - B'.

[0088] [Specific surface area determined by the BET method from the CO2 adsorption isotherm at 25°C] Specific surface area (m²) 2 The specific surface area (m² / g) was determined as follows: First, using a specific surface area / pore distribution analyzer (BELSORP®-MAX (product name) manufactured by Microtrac-Bell Co., Ltd.), the molecular sieve carbon obtained in the examples and comparative examples was heated under reduced pressure (vacuum level: 0.1 kPa or less) at 250°C for 3 hours, and then the carbon dioxide adsorption isotherm of the molecular sieve carbon at 25°C was measured. Using the obtained carbon dioxide adsorption isotherm, a straight line was calculated from the obtained curve by BET analysis using the multipoint method in the region where the relative pressure P / P0 = 0.001 to 0.016, and the specific surface area (m²) was calculated from this straight line. 2 The value per g was calculated.

[0089] [Amount of Fine Powder Generated] The amount of fine powder generated due to wear, cracking, and chipping of the material was determined as follows. First, 2.0 g of molecular sieve carbon obtained in the examples and comparative examples was weighed into a 100 ml stoppered Erlenmeyer flask and shaken at room temperature for 48 hours using a shaker (amplitude 47 mm, 140 reciprocations / min). Then, 50 mL of ethanol was added and shaken for a further 30 minutes. Immediately after shaking, a portion of the suspension was transferred to a spectrophotometer square cell (10 mm × 10 mm), and the absorbance at a wavelength of 650 nm was measured. This absorbance was taken as the amount of fine powder generated. In other words, the smaller the absorbance, the less fine powder is generated due to wear, cracking, and chipping of the material.

[0090] [Gas Separation Performance] The gas separation performance of molecular sieve carbon was determined as follows from the adsorption rate curve obtained using a known constant-volume method. This will be explained using the schematic diagram of the adsorption rate measuring device shown in Figure 3. First, in the adsorption rate measuring device, valves 1, 2, and 3 were closed, and 3 g of molecular sieve carbon 7 was packed into a 20 mL sample cell 6. Next, valves 2 and 3 were opened, and the sample cell 6 and a 100 mL gas reservoir 5 were evacuated from the outlet 9. Next, valves 2 and 3 were closed, and valve 1 was opened, and oxygen (purity: 99.999%, manufactured by Naniwa Oxygen Co., Ltd.) was introduced into the gas reservoir 5 from the inlet 8 until the pressure reached approximately 75 kPa (absolute pressure). Next, valve 1 was closed, valve 2 was opened, and the oxygen adsorption measurement was started. The pressure P in the system at the elapsed time t (seconds) from the time the valve was opened was... t The pressure was measured using pressure sensor 4 until equilibrium was reached. The measurement was performed under conditions of 25°C (room temperature).

[0091] Here, the oxygen adsorption fraction θ_O2(t) is defined by the following equation (1). By defining it in this way, when no oxygen is adsorbed, θ_O2(t) = 0, and as adsorption progresses, the value of θ_O2(t) increases, and when equilibrium is reached, θ_O2(t) = 1, we can obtain an adsorption rate curve θ. θ_O2(t) = (P t -P0) / (P eq -P0) ... (1)

[0092] In formula (1), P tis the pressure (kPa) within the system at elapsed time t (seconds), and P eq P0 is the pressure (kPa) at the point when equilibrium is reached, and P0 is the pressure (kPa) defined by equation (2) below, which is the pressure (kPa) in the system at the moment valve 2 is opened.

[0093] P0 = P g ×V g / V d ... (2)

[0094] In formula (2), P g V is the pressure (kPa) of the gas reservoir 5 before valve 2 is opened, g V is the volume of gas reservoir 5 (mL), and Vd is the dead volume of the system, i.e., the volume of the system minus the volume occupied by molecular sieve carbon 7 (mL).

[0095] Next, the nitrogen adsorption rate curve θ_N2(t) is obtained by performing the exact same operation except that the gas introduced into gas reservoir 5 is changed to nitrogen (purity: 99.999%, manufactured by Naniwa Oxygen Co., Ltd.).

[0096] Let t_1 / 2_O2 be the time t at which θ_O2(t) = 0.5, and t_1 / 2_N2 be the time t at which θ_N2(t) = 0.5. Define the selectivity k as k = t_1 / 2_N2 / t_1 / 2_O2. A larger selectivity k indicates that oxygen and nitrogen are kinetically separated. In other words, a larger selectivity k means higher gas separation performance.

[0097] [Gas Adsorption Performance] In addition to the gas separation performance described above, gas adsorption performance is also important for molecular sieve carbon. Therefore, the gas adsorption performance was evaluated as follows. First, using a specific surface area / pore distribution analyzer (BELSORP®-MAX (product name) manufactured by Microtrac-Bell Co., Ltd.), the molecular sieve carbon obtained in the examples and comparative examples was heated under reduced pressure (vacuum level: 0.1 kPa or less) at 250°C for 3 hours, and then the oxygen adsorption isotherm of the molecular sieve carbon at 25°C was measured. The obtained oxygen adsorption isotherm was fitted using the Freundlich equation to determine the amount of oxygen adsorbed per unit weight (mL / g) at 100 kPa. A larger value for the amount of oxygen adsorbed per unit weight (mL / g) indicates higher gas adsorption performance. Furthermore, the packing density of the molecular sieve carbon obtained in the examples and comparative examples was measured according to JIS K 1474:2014 Activated Carbon Test Method Packing Density, and the oxygen adsorption amount per unit volume (mL / mL) was determined by multiplying this by the oxygen adsorption amount per unit weight. A higher value for oxygen adsorption amount per unit volume (mL / mL) indicates higher gas adsorption performance.

[0098] [Measurement Results] The ratio of sphericity Sp to diameter D determined by the diameter method Sp / D, the crushing strength per unit cross-sectional area, the total volume of pores with a diameter of 7.8 nm or more determined by the mercury intrusion method, the average pore diameter determined by the mercury intrusion method, the total volume of pores with an entrance diameter of 0.37 nm or more and less than 0.46 nm determined by the molecular probe method, the total volume of pores with an entrance diameter of 0.46 nm or more determined by the molecular probe method, the specific surface area determined by the BET method from the CO2 adsorption isotherm at 25°C, the amount of fine powder generated (absorbance), the selectivity k, the amount of oxygen adsorbed per unit weight at 100 kPa, and the amount of oxygen adsorbed per unit volume at 100 kPa are shown in Tables 1 and 2.

[0099]

[0100]

[0101] As shown in Tables 1 and 2, the sphericity ratio Sp / D, determined by the diameter method, is 0.005 or greater and 0.015 or less, indicating a spherical shape, and the crush strength per unit cross-sectional area is 20 kg / mm². 2 More than 50kg / mm 2 The molecular sieve carbon (Examples 1-4) that meets the following conditions, and whose total volume of pores with a diameter of 7.8 nm or more, as determined by the mercury intrusion method, is between 0.10 mL / g and 0.25 mL / g, exhibits significantly reduced generation of fine powder while maintaining high gas separation and gas adsorption performance compared to molecular sieve carbon (Comparative Examples 1-4) that do not meet the above conditions. In Comparative Examples 3 and 4, the selectivity k was set to 1.00 because molecular sieve carbon exhibiting gas separation performance could not be produced. In Comparative Examples 5-8, the material melted during the carbonization process of the ion exchange resin, making it impossible to carry out the subsequent firing process.

[0102] In other words, the sphericity ratio Sp / D, determined by the diameter method, is 0.005 or greater and 0.015 or less, indicating a spherical shape, and the crush strength per unit cross-sectional area is 20 kg / mm². 2 More than 50kg / mm 2 The molecular sieve carbon is as follows: the total volume of pores with a diameter of 7.8 nm or more, as determined by the mercury intrusion method, is between 0.10 mL / g and 0.25 mL / g; the ratio of sphericity Sp to diameter D, as determined by the diameter method, is between 0.005 and 0.015; and the crush strength per unit cross-sectional area is 20 kg / mm². 2 In summary, molecular sieve carbon that has a total volume of pores with an entrance diameter of 0.37 nm or more and less than 0.46 nm, as determined by molecular probe testing, of 0.150 mL / g or more, and a total volume of pores with an entrance diameter of 0.46 nm or more, as determined by molecular probe testing, of 0.030 mL / g or less, exhibits significantly reduced generation of fine particles while maintaining high gas separation and gas adsorption performance compared to molecular sieve carbon that does not meet the above conditions.

[0103] A...Adsorption tower, B...Adsorption tower, 11...Compressor, 12...Raw material tank, 13a...Valve, 13b...Valve, 14a...Valve, 14b...Valve, 15...Valve, 16a...Valve, 16b...Valve, 17...Product tank, 18...Valve, 19...Discharge port, 1...Valve, 2...Valve, 3...Valve, 4...Pressure sensor, 5...Gas reservoir, 6...Sample cell, 7...Molecular sieve carbon, 8...Inlet, 9...Discharge port, 20...Glass container, 21...Pinhole, 22...Weighing bottle containing molecular sieve carbon, 23...Perforated plate, 24...Petri dish filled with carbon disulfide or chloroform

Claims

1. The sphericity ratio Sp / D, determined by the diameter method, is 0.005 or greater and 0.015 or less, and the crush strength per unit cross-sectional area is 20 kg / mm². 2 The above describes molecular sieve carbon, wherein the total volume of pores with a diameter of 7.8 nm or more, as determined by the mercury intrusion method, is between 0.10 mL / g and 0.25 mL / g.

2. The sphericity ratio Sp / D, determined by the diameter method, is 0.005 or greater and 0.015 or less, and the crush strength per unit cross-sectional area is 20 kg / mm². 2 The molecular sieve carbon is characterized in that the total volume of pores with an entrance diameter of 0.37 nm or more and less than 0.46 nm, as determined by molecular probe testing, is 0.150 mL / g or more, and the total volume of pores with an entrance diameter of 0.46 nm or more, as determined by molecular probe testing, is 0.030 mL / g or less.

3. Molecular sieve carbon according to claim 1 or 2, wherein the average pore size determined by the mercury intrusion method is 30 nm or more and 100 nm or less.

4. The specific surface area, determined by the BET method from the CO2 adsorption isotherm at 25°C, is 350 m². 2 / g or more 600m 2 Molecular sieve carbon according to claim 1 or 2, wherein the amount is less than or equal to / g.

5. Molecular sieve carbon according to claim 1 or 2, which selectively adsorbs oxygen from a mixed gas containing at least oxygen and nitrogen.

6. Molecular sieve carbon according to claim 1 or 2, which selectively adsorbs one or more gases from a mixed gas containing at least two gases selected from the group consisting of nitrogen, carbon dioxide, methane, ethane, ethylene, propylene, and propane.

7. A method for producing molecular sieve carbon according to claim 1 or 2, comprising the steps of: carbonizing a raw material to obtain a carbide; and calcining the carbide.

8. A gas separation apparatus for separating oxygen from air by pressure swing adsorption, wherein the apparatus comprises molecular sieve carbon as the adsorbent in the pressure swing adsorption method, as described in claim 1 or 2.

9. A gas separation apparatus for separating one or more gases from a mixed gas containing at least two gases selected from the group consisting of nitrogen, carbon dioxide, methane, ethane, ethylene, propylene, and propane by pressure swing adsorption, wherein the apparatus comprises molecular sieve carbon as the adsorbent in the pressure swing adsorption method, as described in claim 1 or 2.

10. A gas separation apparatus for separating oxygen from air by a temperature swing adsorption method, wherein the apparatus comprises molecular sieve carbon as the adsorbent in the temperature swing adsorption method, as described in claim 1 or 2.

11. A gas separation apparatus for separating one or more gases from a mixed gas containing at least two gases selected from the group consisting of nitrogen, carbon dioxide, methane, ethane, ethylene, propylene, and propane by a temperature swing adsorption method, wherein the apparatus comprises molecular sieve carbon as the adsorbent in the temperature swing adsorption method according to claim 1 or 2.

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