JP7454199B1 - Molecular sieve carbon, its manufacturing method, and gas separation device - Google Patents

Abstract

[Problem] To provide a molecular sieve carbon with improved performance for selectively adsorbing oxygen and separating oxygen from air, a method for producing the same, and a gas separation device. [Solution] The molecular sieve carbon for separating oxygen from air of the present invention has a half-width of the main peak of the oxygen adsorption rate constant distribution of 0.35 sec-1 or less, and a specific surface area of 300 m2/g or more and 600 m2/g or less, as determined by the BET method from the CO2 adsorption isotherm at 25°C. [Selected Figure] Figure 5

Description

The present invention relates to a carbon molecular sieve, a method for producing the same, and a gas separation device.

Carbon Molecular Sieve (CMS) is a porous carbon material whose pore entrance diameter is precisely designed and controlled to match the molecular diameter to be separated. Expresses speed separation type molecular sieve properties. For this reason, it is used to separate low-molecular gases using the Pressure Swing Adsorption (PSA) method and the Thermal Swing Adsorption (TSA) method. Widely used for separation with nitrogen.

The PSA method involves filling one or more adsorption towers with molecular sieve carbon, and periodically repeating selective adsorption under pressure and regeneration of the molecular sieve carbon under reduced pressure or normal pressure. This is a method to separate the In the above-described oxygen/nitrogen separation, oxygen with a small molecular diameter is selectively adsorbed, and nitrogen is extracted as a product gas.

In recent years, the required purity of nitrogen gas in the chemical and semiconductor fields has increased, and the importance of improving the separation performance of CMS has increased. Therefore, many prior art techniques aimed at improving the separation performance of CMS have been disclosed.

For example, Patent Document 1 describes the separation ratio α of oxygen and nitrogen (the ratio of the adsorption rate constant of oxygen K(O ₂ ) to the adsorption rate constant of nitrogen K(N ₂ ) K(O ₂ )/K(N ₂ )) is 35 or more, and the adsorption rate characteristic is the relationship between the time t95 required to adsorb ₉₅ % of the oxygen equilibrium adsorption amount and the time _t50 required to adsorb 50% of the oxygen equilibrium adsorption amount. A carbon molecular sieve satisfying (t ₉₅ /t ₅₀ )<0.4(α-24) (α>35) is disclosed.

International Publication No. 2003/018189

However, the molecular sieve carbon of Patent Document 1 has a problem in that the amount of nitrogen gas generated per unit time is small because the PSA half cycle time for achieving gas separation is long, 90 seconds to 105 seconds.

Since molecular sieve carbon has a wide pore size distribution, ranging from ultramicropores to macropores, the adsorption rate constant has a distribution that corresponds to the pore size distribution. When the gases to be separated are oxygen (minimum molecular diameter: 0.28 nm) and nitrogen (minimum molecular diameter: 0.30 nm), the gases must be separated based on a molecular diameter difference of only 0.02 nm, and this slight difference in pore size distribution, i.e., the difference in adsorption rate constant distribution, has a significant effect on separation performance.

However, in Patent Document 1, the adsorption rate constant distribution was not taken into account, and it was difficult to improve the separation performance between oxygen and nitrogen where the difference in minimum molecular diameter was 0.02 nm.

The present invention was made in view of these problems, and provides a carbon molecular sieve with improved performance for selectively adsorbing oxygen and separating oxygen from air, a method for producing the same, and a gas separation device. It is about providing.

As a result of intensive studies to solve the above-mentioned problems, the present inventors discovered that the above-mentioned problems could be solved by using a specific molecular sieve carbon, its manufacturing method, and a specific gas separation device, and completed the present invention. I ended up doing it.

The present invention includes the following embodiments.
[1] The half width of the main peak of the oxygen adsorption rate constant distribution is 0.35 seconds ^or less, and the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C is 300 m ² /g. Molecular sieve carbon having a density of at least 600 m ² /g.

[2] The molecular sieve carbon according to [1], wherein the maximum center of the main peak of the oxygen adsorption rate constant distribution is 0.030 sec ^-1 or more and 0.250 sec ^-1 or less.

[3] The molecular sieve carbon according to [1], wherein the volume of pores having a pore entrance diameter of 0.37 nm or more and 0.46 nm or less as determined by a molecular probe method is 0.150 mL/g or more.

[4] The molecular sieve carbon according to [1], which is made of non-graphitizable carbon.

[5] The carbon molecular sieve according to [1], wherein the gas to be separated is air, and the carbon molecular sieve selectively adsorbs oxygen from the air.

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

[7] The method of [1] to [6], which includes a step of carbonizing a raw material to obtain a carbide, an activation step of activating the carbide to obtain an activated material, and a firing step of firing the activated material. A method for producing carbon molecular sieve according to any one of the above.

[8] A gas separation device for separating oxygen from air by a pressure swing adsorption method, wherein the molecular sieve carbon according to any one of [1] to [5] is used as an adsorbent in the pressure swing adsorption method. Equipped with equipment.

[9] Selectively adsorb one or more gases from a mixed gas containing at least two gases selected from the group consisting of carbon dioxide, methane, ethane, ethylene, propylene, and propane by pressure swing adsorption method. A gas separation device for
An apparatus comprising the carbon molecular sieve according to any one of [1] to [4] and [6] as an adsorbent in the pressure swing adsorption method.

[10] A gas separation device for separating oxygen from air by a temperature swing adsorption method, wherein the molecular sieve carbon according to any one of [1] to [5] is used as an adsorbent in the temperature swing adsorption method. Equipped with equipment.

[11] Selectively adsorb one or more gases from a mixed gas containing at least two gases selected from the group consisting of carbon dioxide, methane, ethane, ethylene, propylene, and propane by temperature swing adsorption method. A gas separation device for
An apparatus comprising the molecular sieve carbon according to any one of [1] to [4] and [6] as an adsorbent in the temperature swing adsorption method.

According to the present invention, it is possible to provide a carbon molecular sieve with improved performance for selectively adsorbing oxygen and separating oxygen from air, a method for producing the same, and a gas separation device.

FIG. 1 is a schematic diagram showing an oxygen adsorption device. FIG. 2 is a schematic diagram of an oxygen adsorption rate curve. FIG. 3 shows a family of theoretical adsorption rate curves for oxygen. FIG. 4 shows an L-Curve. Figure 5 shows the adsorption rate constant distribution. FIG. 6 shows a schematic diagram of a pore volume measuring device using a molecular probe method. FIG. 7 shows a schematic diagram of a nitrogen generator using pressure swing adsorption.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "this embodiment") will be described in detail. Note that the present embodiment below is an illustration for explaining the present invention, and the present invention is not limited only to this embodiment.

[Molecular sieve carbon]
The carbon molecular sieve for separating oxygen from air of this embodiment has a half width of the main peak of the oxygen adsorption rate constant distribution of 0.35 sec ^-1 or less, and CO ₂ (carbon dioxide) at 25°C. The specific surface area determined by the BET method from the adsorption isotherm is 300 m ² /g or more and 600 m ² /g or less.

Since the molecular sieve carbon has such a configuration, the pore entrance diameter distribution of the molecular sieve carbon becomes more uniform, and the amount of oxygen adsorbed is further increased. Therefore, compared to conventional carbon molecular sieves, carbon molecular sieves can selectively adsorb oxygen and improve the performance for separating oxygen from air. On the other hand, if the half-width of the main peak of the oxygen adsorption rate constant distribution is larger than 0.35 s ^-1 , the pore entrance diameter distribution of carbon molecular sieve is too broad, and not only oxygen but also nitrogen can be adsorbed. The number of pores progressing simultaneously increases. Therefore, such molecular sieve carbon has a reduced performance for separating oxygen from air. Furthermore, if the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25° C. is smaller than 300 m ² /g, the amount of oxygen adsorbed will be small, and the performance for separating oxygen from air will be degraded. If the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C is larger than 600 m ² /g, the size of the inside of the pores, which is the site of oxygen adsorption, will not be suitable for oxygen adsorption, and the amount of oxygen adsorption will decrease. The performance for separating oxygen from air decreases.

The half-width of the main peak of the oxygen adsorption rate constant distribution is preferably 0.33 seconds ^or less, since oxygen can be adsorbed more selectively and the performance for separating oxygen from air can be further improved. , 0.30 sec ^-1 or less is more preferable. Although the lower limit is not particularly limited, it is, for example, 0.05 sec ^-1 or more. Note that the method for determining the half-width of the main peak of the oxygen adsorption rate constant distribution will be described later.

Since it can adsorb oxygen more selectively and improve the performance for separating oxygen from air, the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C is 350 m ² /g. The area is preferably at least 400 m ² /g, more preferably at least 415 m ² /g, and even more preferably at least 415 m 2 /g. Note that Examples may be referred to for a specific method of measuring the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C.

In the carbon molecular sieve of the present embodiment, the maximum center of the main peak of the oxygen adsorption rate constant distribution is preferably 0.030 sec ^-1 or more and 0.250 sec ^-1 or less, more preferably 0.110 sec ^-1. It is above 0.130 seconds ^-1 . The maximum center of the main peak of the oxygen adsorption rate constant distribution represents the adsorption rate of carbon molecular sieve. When this is within the above range, the oxygen adsorption rate of the carbon molecular sieve is optimized, and the performance for separating oxygen from air can be further improved compared to conventional carbon molecular sieves. Furthermore, if the maximum center of the main peak of the oxygen adsorption rate constant distribution is smaller than 0.030 s ^-1 , oxygen adsorption tends to be too slow, and if it is larger than 0.250 s ^-1 , oxygen adsorption tends to be too slow. Adsorption tends to be too rapid. Therefore, when such molecular sieve carbon is used as an adsorbent in a pressure swing adsorption method or an adsorbent in a temperature swing adsorption method, it may become difficult to optimize the operating conditions of the gas separation device. Note that the method for determining the maximum center of the main peak of the oxygen adsorption rate constant distribution will be described later.

Preferably, the molecular sieve carbon of this embodiment has a pore volume of 0.150 mL/g or more, which has a pore entrance diameter of 0.37 nm or more and 0.46 nm or less, as determined by a molecular probe method, and more preferably 0. .220 mL/g or more, more preferably 0.225 mL/g or more and 0.260 mL/g or less. When separating oxygen from air, the pore entrance diameter of the molecular sieve carbon and the pore volume with that pore entrance diameter are also very important. According to the study by the present inventors, the pore entrance diameter of carbon molecular sieve and oxygen adsorption are determined by the volume of pores having a pore entrance diameter of 0.37 nm or more and 0.46 nm or less being 0.150 mL/g or more. The amount is optimized and tends to further improve the performance for separating oxygen from air compared to traditional carbon molecular sieves. Note that the upper limit is not particularly limited, but is, for example, 0.300 mL/g or less. Note that a method for determining the volume of a pore having a pore entrance diameter of 0.37 nm or more and 0.46 nm or less, which is determined by the molecular probe method, will be described later.

The molecular sieve carbon of this embodiment preferably contains non-graphitizable carbon, and more preferably contains non-graphitizable carbon, since it can more selectively adsorb oxygen and further improve the performance for separating oxygen from air. Consists of oxidizable carbon. Examples of non-graphitizable carbons include coal; coconut shells such as palm shells and coconut shells; natural fibers such as linen and cotton; synthetic fibers such as rayon and polyester; polyacrylonitrile, phenolic resins, and polychloride. Examples include synthetic resins such as vinylidene, polycarbonate, and polyvinyl alcohol; carbon made from charcoal, carbon black, glassy carbon, and the like.

(How to find the half width and maximum center of the main peak of the distribution of oxygen adsorption rate constant)
The half width and maximum center of the main peak of the distribution of oxygen adsorption rate constants are determined as follows.
First, the distribution of the oxygen adsorption rate constant can be determined as follows from the adsorption rate curve obtained using the known constant volume method. This will be explained using a schematic diagram of an oxygen adsorption device shown in FIG.

First, in the oxygen adsorption apparatus, valve 1, valve 2, and valve 3 are closed, and 3 g of carbon molecular sieve 7 is filled into sample cell 6 having a volume of 20 mL. Next, the valves 2 and 3 are opened, and the sample cell 6 and the gas reservoir 5 having a volume of 100 mL are evacuated from the exhaust port 9. Next, valves 2 and 3 are closed, valve 1 is opened, and oxygen (purity: 99.999%, Naniwa Oxygen Co., Ltd. company-made). Next, valve 1 is closed, valve 2 is opened, and oxygen adsorption measurement is started. The pressure P _t in the system at the elapsed time t (seconds) from the time when the valve is opened is measured by the pressure sensor 4 until equilibrium is reached. Note that the measurement is performed at 25° C. (room temperature).

Here, the adsorption fraction θ(t) is defined by the following formula (1). With this definition, when no gas is adsorbed, θ(t) = 0, and as adsorption progresses, the value of θ(t) increases, and when equilibrium is reached, θ(t) It is possible to obtain an adsorption rate curve θ where =1.

θ(t)=(P _t - P ₀ )/(P _eq - P ₀ )...(1)

In formula (1), P _t is the pressure (kPa) in the system at the elapsed time t (seconds), P _eq is the pressure (kPa) at the time when equilibrium is reached, and P ₀ is expressed by the following formula (2 ), and is the pressure (kPa) in the system at the moment when valve 2 is opened.

P ₀ =P _g ×V _g /V _d ...(2)

In equation (2), P _g is the pressure (kPa) of the gas reservoir 5 before opening the valve 2, V _g is the volume (mL) of the gas reservoir 5, and V _d is the dead volume of the system, that is, the system It is the volume (mL) obtained by subtracting the volume occupied by the molecular sieve carbon 7 from the volume.

By plotting the adsorption fraction θ(t) on the vertical axis and the elapsed time t (seconds) on the horizontal axis, an oxygen adsorption rate curve as illustrated in FIG. 2 is obtained.

Next, an adsorption rate constant distribution is obtained from the oxygen adsorption rate curve as follows.
Since molecular sieve carbon has a wide pore size distribution ranging from macropores to ultramicropores, the adsorption rate constant also has a distribution. Therefore, a group of theoretical adsorption rate curves that are theoretically determined from a large number of adsorption rate constants is prepared, and the experimentally obtained adsorption rate curve is reproduced by linear addition of these curves. The distribution of adsorption rate constants can be expressed by the weighting coefficient applied to each theoretical adsorption rate curve during linear addition. Specifically, it is performed as follows.

First, a group of theoretical oxygen adsorption rate curves is prepared. The theoretical adsorption rate curve θ _ideal is expressed by the following equation (3) based on the LDF model. Furthermore, in the theoretical adsorption rate curve θ _ideal , the theoretical adsorption fraction at a certain time t is expressed as θ _ideal (t). Regarding the LDF model, you may refer to Adsorption (2017) 23:131-147.

θ _ideal (t)=1-exp(-α×k _LDF ×t)...(3)

In formula (3), α is a value defined by formula (4) below. Moreover, _kLDF is an adsorption rate constant (sec ^-1 ), and t is time (sec).

α=P ₀ /P _eq ...(4)

In formula (4), P ₀ and P _eq are as described above. That is, P ₀ is the pressure (kPa) defined by the above equation (2), and P _eq is the pressure (kPa) at the time when equilibrium is reached.

In order to obtain a group of theoretical adsorption rate curves for oxygen, the following value is used as _kLDF , and a group consisting of a total of 46 theoretical adsorption rate curves is prepared.
1.00×10 ⁻⁹ , 1.58×10 ⁻⁹ , 2.51×10 ⁻⁹ , 3.98×10 ⁻⁹ , 6.31×10 ⁻⁹ , 1.00×10 ⁻⁸ , 1. 58× ^10-8 , 2.51× ^10-8 , 3.98× ^10-8 , 6.31× ^10-8 , 1.00×10-7, ^{1.58×10-7 ,} 2.51× ^10-7 , 3.98× ^10-7 , 6.31× ^10-7 , 1.00× ^10-6 , 1.58× ^10-6 , 2.51× ^10-6 , 3.98× ^{10- 6} , 6.31× ^10-6 , 1.00× ^10-5 , 1.58× ^10-5 , 2.51× ^10-5 , 3.98× ^10-5 , 6.31× ^10-5 , 1.00×10 ⁻⁴ , 1.58×10 ⁻⁴ , 2.51×10 ⁻⁴ , 3.98×10 ⁻⁴ , 6.31×10 ⁻⁴ , 1.00×10 ⁻³ , 1. 58×10 ⁻³ , 2.51×10 ⁻³ , 3.98×10 ⁻³ , 6.31×10 ⁻² , 1.58×10 ⁻² , 2.51×10 ⁻² , 3.98× ^10-2 , 6.31× ^10-2 , 1.00× ^10-1 , 1.58× ^10-1 , 2.51× ^10-1 , 3.98×10-1, ^6.31 × ^{10-1 1} , and 1.00.

In order to obtain the theoretical oxygen adsorption rate curve group, the following value is used for t.
0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, and 2400.

FIG. 3 shows a group of theoretical oxygen adsorption rate curves obtained in this way.

Next, a method for reproducing the oxygen adsorption rate curve obtained from experiments by linear addition of the theoretical adsorption rate curve group shown in FIG. 3 will be described.

First, the theoretical adsorption rate curve group shown in FIG. 3 is expressed as a square matrix A. That is, let A _ij represent the i-th row and j-th column of A, then set the value of k _LDF =1.0×10 ^-9 to A ₁₁ , the value of t=0.5 to A ₁₂ , and set k _LDF =1 to A 12. The value of θ when k _LDF =1.0×10 ⁻⁹ is listed for each t in the first column of A, such as the value of .0×10 ⁻⁹ and the value of t=1.
Next, in the second column of A, the values of θ when k _LDF =1.58×10 ⁻⁹ are listed for each t as before. This is repeated for all k _LDFs to obtain a 46th order square matrix A.
Next, the experimentally obtained oxygen adsorption rate curve is expressed by vector b.

That is, from the oxygen adsorption rate curve obtained in the experiment, t=0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 400, The theoretical adsorption fractions θ _ideal (t) at times of 500, 600, 700, 800, 900, 1000, 1500, 2000, and 2400 are determined and listed as a vector b.

Next, the weight to be applied to each theoretical adsorption rate curve for linear addition is expressed by a vector x. Here, the Tikhonov regularization method is used to find the optimal vector x.

That is, find x that minimizes the value expressed by equation (5) below.

||Ax−b|| ² +λ||x|| ² ...(5)

In equation (5), ||Ax−b|| ² = Σ _i (Σ _j A _ij x _j − b _i ) ² , ||x|| ² = Σ _i x _j ² , and λ is regular parameter.

Prepare the following candidates for λ.
0, 0.01, 0.0398, 0.063, 0.1, 0.398, 0.63, 1, 3.98, 6.3, 10, 15.8, 25.1, 39.8, 63, 100, 158, 251, 398, 630, 1000, 1580, 2510, 3980, 6300, and 10000.

For each λ, find x that minimizes the value expressed by equation (5). At this time, x is found using the solver function of Microsoft Excel 2016. The solving method of the solver is GRG (Generalized Reduced Gradient) nonlinearity. The optimal λ and its corresponding x are determined from the x for each λ obtained in this way. For this purpose, the L-Curve method is used. In other words, plot log ₁₀ ||x|| on the horizontal axis and log ₁₀ ||Ax-b|| on the vertical axis to draw an L-Curve, and calculate Adopt the corresponding x. An example of the L-Curve method and points to be adopted are illustrated in FIG. Note that the plot indicated by the arrow in FIG. 4 is the optimum λ and the x corresponding to it.

Through the above procedure, x, which is the weight to be applied to each theoretical adsorption rate curve, is obtained. Next, the adsorption rate constant ( _kLDF ) of the theoretical adsorption rate curve is plotted on the horizontal axis, and the weight (x) corresponding to each adsorption rate constant is plotted on the vertical axis. Thereby, an adsorption rate constant distribution can be obtained. In this specification, this plot is defined as an adsorption rate constant distribution. FIG. 5 illustrates the adsorption rate constant distribution obtained by this method. In FIG. 5, it can be seen that there is a main peak, that is, a peak where the local maximum value of the weight is the largest, near _kLDF = 0.1 (sec ^-1 ).

The half width and maximum center of the main peak of the oxygen adsorption rate constant according to this embodiment can be determined by fitting the adsorption rate constant distribution shown in FIG. 5 with a lognormal distribution function. For fitting, OriginPro 2021b manufactured by OriginLab is used, and the peak fitting function can be used.

(How to determine pore volume)
First, in this specification, the molecular probe method refers to gas molecules whose minimum molecular diameter and density are known to be adsorbed onto molecular sieve carbon, and the amount of adsorption is measured. A method for determining the pore volume of pores.

The volume of a pore having a pore entrance diameter of 0.37 nm or more and 0.46 nm or less, which is determined by the molecular probe method, can be determined as follows. This will be explained using a schematic diagram of a pore volume measuring device using the molecular probe method shown in FIG.

As shown in FIG. 6, a petri dish 24 filled with carbon disulfide (minimum molecular diameter: 0.37 nm, density: 1.263 g/mL) is placed in a glass container 20 having a pinhole 21, and then The weighing bottle 22 containing molecular sieve carbon as a sample is placed still through the punching plate 23. The glass container 20 is placed in a constant temperature bath at 25° C., and carbon disulfide is adsorbed onto the carbon molecular sieve for 24 hours. From the change in mass of the carbon molecular sieve before and after adsorption, the equilibrium adsorption amount of carbon disulfide Ag/g per gram of carbon molecular sieve is determined. Since the minimum molecular diameter of carbon disulfide is 0.37 nm and the density of carbon disulfide is 1.263 g/mL, the volume of pores having a pore entrance diameter of 0.37 nm or more is A'mL/g. is determined by A'=A/1.263.

By replacing carbon disulfide with chloroform (minimum molecular diameter: 0.46 nm, density: 1.410 g/mL) and measuring in the same manner as above, the equilibrium adsorption amount of chloroform per gram of carbon molecular sieve Bg/ g is determined, and the volume B'mL/g of pores having a pore entrance diameter of 0.46 nm or more is determined as B'=B/1.410.

Using the calculated values of A' and B', the volume of a pore having a pore entrance diameter of 0.37 nm or more and 0.46 nm or less is determined by A'-B' mL/g.

(Shape of molecular sieve carbon)
The shape of the carbon molecular sieve is not particularly limited, and can be any shape that can be used as a known adsorbent. Examples of such shapes include pellets, powders, substrates (sheets), rods, blocks, spheres, ellipsoids, distorted shapes, and fibers. From the viewpoint of being able to more selectively adsorb oxygen, improving the performance for separating oxygen from air, and being easy to apply to various applications, the shape of molecular sieve carbon is pellet-like or powder-like. It is preferable that there be. Further, when the molecular sieve carbon is in the form of pellets, unnecessary fine powder is less likely to be generated, and therefore piping etc. are less likely to be clogged in the process of molding the molecular sieve carbon. From the viewpoint of ease of molding, it is more preferable that the molecular sieve carbon is in the form of a cylindrical pellet.

When the carbon molecular sieve is in the form of a pellet, its planar shape can be, for example, a shape that can be used as a known adsorbent. Examples of such a shape include a circular shape, an elliptical shape, a rectangular shape, a rod shape, a distorted shape, and the like in plan view. When the carbon molecular sieve is in the form of a pellet, its thickness is not particularly limited, and known adsorbents can be used as a reference. The thickness is preferably applicable as an adsorbent in a pressure swing adsorption method or a temperature swing adsorption method, and is usually 100 μm or more and 10,000 μm or less.

When the carbon molecular sieve is in the form of a cylindrical pellet, the pellet preferably has a diameter of 0.1 mm or more and 4.0 mm or less, and an aspect ratio of 1:1 to 1:10. Such pellets are suitable as adsorbents in pressure swing adsorption methods or temperature swing adsorption methods.

In this specification, the diameter of a pellet means the average value of the diameters of 30 molecular sieve carbon particles randomly sampled. The diameter can be measured using, for example, calipers. Examples may be referred to for specific measurement methods.
As used herein, the aspect ratio means the ratio of the diameter and height of one molecular sieve carbon, ie, the diameter of the molecular sieve carbon: the height of the molecular sieve carbon. The aspect ratio means the average value of the aspect ratios of 30 molecular sieve carbons randomly sampled. Examples may be referred to for specific measurement methods.

When the molecular sieve carbon is in the form of a powder, the particle size (average particle diameter, D50) of the molecular sieve carbon is preferably 1 μm or more and 150 μm or less. Such powders are suitable as adsorbents in temperature swing adsorption methods.
In addition, in this specification, the average particle diameter (D50) is measured as a volume-based median diameter using a laser diffraction light scattering particle size distribution measuring device in accordance with JIS K 1474.

(Application)
The carbon molecular sieve of this embodiment can be suitably used for air as a gas to be separated. That is, the carbon molecular sieve can selectively adsorb oxygen from air when the gas to be separated is air.

The molecular sieve carbon of this embodiment can be suitably used for a mixed gas containing at least two gases selected from the group consisting of carbon dioxide, methane, ethane, ethylene, propylene, and propane as a gas to be separated. That is, molecular sieve carbon is a mixed gas in which the gas to be separated contains at least two gases selected from the group consisting of carbon dioxide, methane, ethane, ethylene, propylene, and propane, and one or more of the mixed gases. can selectively adsorb gases.

[Method for producing molecular sieve carbon]
The carbon molecular sieve of this embodiment can be obtained by a known manufacturing method.

Examples of such methods include a thermal decomposition method, an activation method, a coating method, and a vapor deposition method. As the manufacturing method, it is preferable to use a thermal decomposition method, a coating method, and a vapor deposition method. By using these production methods, the half-width of the main peak of the distribution of oxygen adsorption rate constant is 0.35 s ^-1 or less, and it is determined by the BET method from the CO ₂ adsorption isotherm at 25°C. There is a tendency that molecular sieve carbon having a specific surface area of 300 m ² /g or more and 600 m ² /g or less can be manufactured more easily. Next, a manufacturing method when the carbon molecular sieve is activated carbon will be described in detail as an example.

The method for producing carbon molecular sieve includes a carbonization step in which a raw material is carbonized to obtain a carbide, an activation step in which the carbide is activated to obtain an activated material, and a firing step in which the activated material is fired.

(Carbonization process)
The method for producing carbon molecular sieve includes a carbonization step of carbonizing a raw material to obtain a carbide.
The raw material is not particularly limited as long as it can obtain the desired carbon molecular sieve, but a raw material that becomes non-graphitizable carbon after carbonizing the raw material is desirable.
Such raw materials include, for example, coal; coconut shells such as palm shells and coconut shells; natural fibers such as linen and cotton; synthetic fibers such as rayon and polyester; polyacrylonitrile, phenolic resins, and polyvinylidene chloride. Examples include synthetic resins such as , polycarbonate, and polyvinyl alcohol; carbon made from charcoal, carbon black, and glassy carbon.

The half width of the main peak of the distribution of the oxygen adsorption rate constant is 0.35 sec ^-1 or less, and the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C is 300 m ² /g or more and 600 m Since molecular sieve carbon having a molecular weight of ² /g or less tends to be more easily produced, it is preferable that the raw material contains at least one member selected from the group consisting of coal, coconut shell, synthetic resin, phenolic resin, and charcoal. Preferably, it contains at least one selected from the group consisting of coconut shells and phenolic resins.

The raw material may contain additives and the like, if necessary. Further, additives and the like may be added to the carbide as necessary.
Examples of such additives include water, coal tar, anhydrous tar, hard pitch, coal tar pitch, and petroleum pitch. The additives may be used alone or in combination of two or more.
The additives and the like are usually blended in an amount of 1 part by mass or more and 50 parts by mass or less, with respect to 100 parts by mass of the raw material or carbide. Further, the total amount of additives and the like is usually 1 part by mass or more and 100 parts by mass or less based on 100 parts by mass of the raw material or carbide. When mixing the raw material or carbide and the additive, if necessary, adjust the amount of oxygen in the raw material or carbide in advance to a range of 1% by mass or more and 20% by mass or less based on 100% by mass of the raw material or carbide. You can adjust it with The amount of oxygen can be adjusted, for example, by mixing the raw material or carbide and oxygen under heating at 150° C. or higher and 300° C. or lower.

In the method for producing carbon molecular sieve, the raw material may be pulverized or molded before being carbonized. Such a method includes, for example, a method in which, before carbonizing the raw material, the raw material is pulverized into a powder using a known pulverizer, and then carbonized. Furthermore, before carbonizing the raw material, there is a method in which the raw material is formed into pellets by a known method and then carbonized.

When the raw material is in the form of powder, the particle size (average particle diameter, D50) of the powder is preferably 1 μm or more and 150 μm or less.

The method of carbonizing the raw material is not particularly limited, and examples include a method of heating the raw material to 300°C or more and 900°C or less, preferably 300°C or more and 800°C or less under oxygen-free conditions.

The carbonization time can be appropriately set depending on the raw material and the equipment for carbonization. The carbonization time is, for example, 15 minutes or more and 20 hours or less, preferably 30 minutes or more and 10 hours or less. The carbonization treatment can be performed using, for example, known production equipment such as a rotary kiln. Further, the carbonization treatment may be performed under reduced pressure with air excluded, or may be performed under a nitrogen atmosphere.

The half width of the main peak of the distribution of the oxygen adsorption rate constant is 0.35 sec ^-1 or less, and the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C is 300 m ² /g or more and 600 m Since molecular sieve carbon having a molecular weight of ² /g or less tends to be more easily produced, in the method for producing molecular sieve carbon, a known pulverizer may be used to pulverize the carbide into powder. In the method for producing molecular sieve carbon, carbide is pulverized into powder, then additives are added to the powdered carbide as needed and kneaded by a known method, and the resulting kneaded product is kneaded by a known method. May be molded.

When the carbide is in powder form, the particle size (average particle diameter, D50) of the carbide is preferably 1 μm or more and 150 μm or less.

The half width of the main peak of the distribution of the oxygen adsorption rate constant is 0.35 sec ^-1 or less, and the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C is 300 m ² /g or more and 600 m ² /g or less, the method for producing carbon molecular sieves uses known methods to produce carbides, powdered carbides, kneaded products, or powdered blends. The forged material may be formed into cylindrical pellets.
When the carbide is shaped like a cylindrical pellet, the diameter of the cylindrical pellet is usually preferably 0.1 mm or more and 4.0 mm or less. Further, the aspect ratio (diameter:height) of the cylindrical pellets is usually preferably 1:1 to 1:10.

Through the carbonization step, a carbide of the raw material is obtained. After carbonization, the carbide may be subjected to cleaning treatment and/or drying treatment. These conditions are not particularly limited, and known conditions can be adopted.

(activation process)
The method for producing carbon molecular sieve includes an activation step of activating a carbide to obtain an activated material.

As the activation treatment, a known method can be adopted. Examples of such methods include activation methods using active gases such as water vapor, oxygen, and carbon dioxide . For the activation treatment, known manufacturing equipment such as a rotary kiln and a fluidized fluidized furnace can be used. Further, the activation treatment may be performed under reduced pressure with air excluded, or may be performed under a nitrogen atmosphere. Examples of the activation treatment include, when using steam, a method of contacting the steam with the carbide at a flow rate of 10 liters (L) or more and 300 liters (L) or less per minute for 1 minute or more and 1440 minutes or less. .

The temperature of the activation treatment is not particularly limited, but the half width of the main peak of the distribution of the oxygen adsorption rate constant is 0.35 sec ^-1 or less, and the temperature is determined by the BET method from the CO ₂ adsorption isotherm at 25°C. Since molecular sieve carbon having a required specific surface area of 300 m ² /g or more and 600 m ² /g or less tends to be more easily produced, the temperature is preferably 750°C or more and 1200°C or less, and the temperature is preferably 800°C or more and 1100°C or less. It is more preferable that there be.

The partial pressure of the active gas is, for example, 10% or more and 100% or less, preferably 30% or more and 100% or less.

The activation time can be appropriately set depending on conditions such as raw materials, activation temperature, and manufacturing equipment. The activation time is, for example, 30 minutes or more and 48 hours or less, preferably 1.0 hour or more and 36 hours or less, and more preferably 70 minutes or more and 24 hours or less.

After the activation treatment, a cleaning treatment, a drying treatment, etc. may be performed. These conditions are not particularly limited, and known conditions can be adopted.

(Firing process)
The method for producing molecular sieve carbon includes a firing step of firing an activated material.
By performing the firing treatment, the pore size distribution of the activator can be adjusted, and the pore size distribution of the carbon molecular sieve can be made uniform. Therefore, compared to conventional carbon molecular sieves, carbon molecular sieves can selectively adsorb oxygen and improve the performance for separating oxygen from air.

Examples of the firing treatment include a method in which the activation material is brought into contact with a carbon source and fired. Examples of the firing method include a thermal decomposition method, a coating method, and a vapor deposition method.

Examples of carbon sources used in the coating method or vapor deposition method include coal tar, anhydrous tar, coal tar pitch, petroleum pitch, and creosote oil. Carbon sources used in pyrolysis and vapor deposition include, for example, alcohols such as methanol and ethanol; esters such as ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic carbonization such as benzene, toluene, and xylene. Hydrogen; aliphatic hydrocarbons such as hexane; amides such as dimethylformamide; and polyhydric alcohols such as ethylene glycol.

Since the pore size distribution of the activator can be more easily adjusted and the pore size distribution of the molecular sieve carbon can be made more uniform, it is possible to use benzene as the carbon source and the firing temperature at 600°C in the coating method or vapor deposition method. When the temperature is above 900°C or less, the lower limit of the amount of benzene used is usually 1.0 parts by mass or more, preferably 1.5 parts by mass or more, and more preferably 2.0 parts by mass, based on 100 parts by mass of the activator. The amount is more preferably 2.5 parts by mass or more, and even more preferably 3.0 parts by mass or more. 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, per 100 parts by mass of the activator. The amount is more preferably 7.5 parts by mass or less.

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

The firing time can be appropriately determined depending on the firing temperature, and is, for example, 15 minutes or more and 240 minutes or less.

The firing process can be performed, for example, under a nitrogen atmosphere, an argon atmosphere, or another inert gas atmosphere.
The firing process may be performed while circulating the carbon source using these gases as a carrier gas. In that case, the flow rate of the carrier gas is preferably 110 L/min or more, more preferably 150 L/min or more and 300 L/min or less, and even more preferably 170 L/min or more and 250 L/min or less. Benzene is preferred as the carbon source passed through the carrier gas. According to such a calcination treatment, the half-value width of the main peak of the distribution of oxygen adsorption rate constant is 0.35 s ^-1 or less, and the half-width is determined by the BET method from the CO ₂ adsorption isotherm at 25°C. There is a tendency that molecular sieve carbon having a specific surface area of 300 m ² /g or more and 600 m ² /g or less can be manufactured more easily.

After the firing process, a cleaning process, a drying process, etc. may be performed. These conditions are not particularly limited, and known conditions can be adopted.

[Gas separation equipment]
The gas separation device is not particularly limited as long as it is equipped with the carbon molecular sieve described above and can separate oxygen using a pressure swing adsorption method or a temperature swing adsorption method. That is, the gas separation device is a device that efficiently separates and recovers gases other than oxygen gas from air containing oxygen gas. Such a gas separation device may have the same configuration as a conventional gas separation device except that it includes the carbon molecular sieve described above.

Further, the gas separation device is equipped with the above molecular sieve carbon, and uses at least two kinds of carbon dioxide, methane, ethane, ethylene, propylene, and propane selected from the group consisting of carbon dioxide, methane, ethane, and propane using a pressure swing adsorption method or a temperature swing adsorption method. The apparatus may be capable of selectively adsorbing one or more gases from a mixed gas containing the following gases to separate the gases. Such a gas separation device may have the same configuration as a conventional gas separation device except that it includes the carbon molecular sieve described above.

Specifically, the following gas separation devices can be mentioned.
The gas separation device of this embodiment is a gas separation device for separating oxygen from air by a pressure swing adsorption method, and includes molecular sieve carbon as an adsorbent in the pressure swing adsorption method.

The gas separation device of this embodiment uses a pressure swing adsorption method to extract one or more gases from a mixed gas containing at least two gases selected from the group consisting of carbon dioxide, methane, ethane, ethylene, propylene, and propane. This is a gas separation device for selectively adsorbing carbon, and includes molecular sieve carbon as an adsorbent in a pressure swing adsorption method.

The gas separation device of this embodiment is a gas separation device for separating oxygen from air by a temperature swing adsorption method, and includes molecular sieve carbon as an adsorbent in the temperature swing adsorption method.

The gas separation device of this embodiment uses a temperature swing adsorption method to extract one or more gases from a mixed gas containing at least two gases selected from the group consisting of carbon dioxide, methane, ethane, ethylene, propylene, and propane. This gas separation device selectively adsorbs carbon molecular sieves as an adsorbent in the temperature swing adsorption method.

Carbon molecular sieve can be suitably used as an adsorbent. Since the adsorbent can efficiently separate oxygen from air, it is suitable for a gas separation device using a pressure swing adsorption method or a temperature swing adsorption method.
The adsorbent may be made of only carbon molecular sieve, or may be made of a combination of other known members.

Next, an example of a gas separation apparatus for separating oxygen from air, which includes molecular sieve carbon as an adsorbent in a pressure swing adsorption method, will be described with reference to FIG.

As shown in FIG. 7, the gas separation device includes adsorption towers A and B filled with molecular sieve carbon, a compressor 11 that pressurizes raw material air, a raw material tank 12 that stores raw material air, and a product tank that stores product gas. 17, valves 13a, 13b, 14a, and 14b that are opened and closed to switch the processes of the adsorption towers A and B, and valves 16a and 16b that send the product gas generated from the adsorption tower to the product tank. It is composed of a pressure equalization valve 15, a product gas extraction valve 18, and an exhaust port 19 for exhausting adsorbed gas.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples in any way.

[Example 1]
(Carbonization process)
The phenol resin was heated to a final temperature of 800° C. over about 5 hours while excluding air in a rotary kiln, thereby carbonizing the phenol resin. 100 parts by mass of a phenol resin carbide was pulverized using a pulverizer until the average particle diameter (D50) became 0.15 mm or less to obtain a phenol resin carbide powder. While adding 20 parts by mass of water to 100 parts by mass of this phenolic resin carbide powder, 40 parts by mass of coal tar was further added and kneaded. The obtained kneaded product was filled into an extrusion molding machine and molded into a cylindrical pellet having a diameter of 2.0 mm and an aspect ratio of 1:5. Thirty of the obtained cylindrical pellets were randomly sampled, and the diameters of these pellets were measured with calipers, and the diameter was determined as an average value. Further, 30 of the obtained cylindrical pellets were randomly sampled, the heights of these pellets were measured with calipers, the average value was determined, and the aspect ratio was determined as the average value of diameter:height. As a result, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

(activation process)
The resulting cylindrical pellets were heated in a rotary kiln, while excluding air, to a final temperature of 800° C. over about 5 hours. Thereafter, the cylindrical pellet was brought into contact with water vapor for 100 minutes at a flow rate of 100 liters per minute to carry out an activation treatment to obtain an activated material.

(Firing process)
Next, in a nitrogen atmosphere at 800° C., 5.0 parts by mass of benzene was passed through 100 parts by mass of the obtained activation material over 120 minutes using nitrogen as a carrier gas at 200 L/min. Through this firing treatment, carbon molecular sieve was obtained.

[Example 2]
A carbon molecular sieve was obtained in the same manner as in Example 1, except that in the firing step, benzene was changed from 5.0 parts by mass to 7.5 parts by mass. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Example 3]
(Carbonization process)
The coconut shell was heated to a final temperature of 800° C. over about 5 hours while excluding air in a rotary kiln, thereby carbonizing the coconut shell. 100 parts by mass of coconut shell carbide was pulverized using a pulverizer until the average particle diameter (D50) became 0.1 mm or less to obtain a coconut shell carbide powder. To 100 parts by mass of this coconut shell carbide powder, while adding 20 parts by mass of water, 40 parts by mass of coal tar was further added and kneaded. The obtained kneaded product was filled into an extrusion molding machine and molded into a cylindrical pellet having a diameter of 2.0 mm and an aspect ratio of 1:5. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

(activation process)
The resulting cylindrical pellets were heated in a rotary kiln, while excluding air, to a final temperature of 800° C. over about 5 hours. Thereafter, the cylindrical pellet was brought into contact with water vapor for 100 minutes at a flow rate of 100 liters per minute to carry out an activation treatment to obtain an activated material.

(Firing process)
Next, under a nitrogen atmosphere at 800° C., 7.5 parts by mass of benzene was passed through 100 parts by mass of the obtained activation material over 120 minutes using nitrogen as a carrier gas at 200 L/min. Through this firing treatment, carbon molecular sieve was obtained.

[Example 4]
Carbon molecular sieve was obtained in the same manner as in Example 3, except that in the firing step, benzene was changed from 7.5 parts by mass to 7.0 parts by mass. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Example 5]
Example 3 except that in the activation step, the activation time during which water vapor was bonded to the cylindrical pellet was changed from 100 minutes to 120 minutes, and in the firing step, benzene was changed from 7.5 parts by mass to 6.0 parts by mass. Carbon molecular sieve was obtained in the same manner as above. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Example 6]
A carbon molecular sieve was obtained in the same manner as in Example 3, except that in the firing step, benzene was changed from 7.5 parts by mass to 5.0 parts by mass. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Example 7]
Carbon molecular sieve was obtained in the same manner as in Example 3, except that in the firing step, benzene was changed from 7.5 parts by mass to 4.0 parts by mass. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Example 8]
Example 3 except that in the activation step, the activation time during which water vapor was bonded to the cylindrical pellet was changed from 100 minutes to 80 minutes, and in the firing step, benzene was changed from 7.5 parts by mass to 3.0 parts by mass. Carbon molecular sieve was obtained in the same manner as above. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Comparative example 1]
In the firing process, molecular sieve carbon was obtained in the same manner as in Example 1, except that the amount of carrier gas was changed from 200 L/min to 100 L/min. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Comparative example 2]
Example 3 except that in the activation step, the activation time during which water vapor was bonded to the cylindrical pellet was changed from 100 minutes to 60 minutes, and in the firing step, benzene was changed from 7.5 parts by mass to 3.0 parts by mass. Carbon molecular sieve was obtained in the same manner as above. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Comparative example 3]
In the firing process, the molecular sieve carbon was prepared in the same manner as in Example 3, except that the amount of carrier gas was changed from 200 L/min to 100 L/min, and the amount of benzene was changed from 7.5 parts by mass to 4.0 parts by mass. I got it. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Comparative example 4]
In the firing process, the molecular sieve carbon was prepared in the same manner as in Example 3, except that the amount of carrier gas was changed from 200 L/min to 75 L/min, and the amount of benzene was changed from 7.5 parts by mass to 4.0 parts by mass. I got it. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Comparative example 5]
In the firing process, the molecular sieve carbon was prepared in the same manner as in Example 3, except that the amount of carrier gas was changed from 200 L/min to 50 L/min, and the amount of benzene was changed from 7.5 parts by mass to 4.0 parts by mass. I got it. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Comparative example 6]
In the activation process, the activation time for adhering water vapor to the cylindrical pellets was changed from 100 minutes to 60 minutes, and in the firing process, the amount of carrier gas was changed from 200 L/min to 50 L/min, and benzene was changed from 7.5 parts by mass to 2 parts by mass. Carbon molecular sieves were obtained in the same manner as in Example 3, except that the amounts were changed to .0 parts by mass. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Comparative example 7]
Example 3 except that in the activation step, the activation time during which water vapor was bonded to the cylindrical pellet was changed from 100 minutes to 40 minutes, and in the firing step, benzene was changed from 7.5 parts by mass to 3.0 parts by mass. Carbon molecular sieve was obtained in the same manner as above. When the diameter and aspect ratio of the pellet were determined in the same manner as in Example 1, it was confirmed that the obtained cylindrical pellet had a pellet diameter of 2.0 mm and an aspect ratio of 1:5.

[Evaluation method]
[Half width of main peak of oxygen adsorption rate constant distribution]
Using the carbon molecular sieves obtained in Examples and Comparative Examples, the half width (sec ^-1 ) of the main peak of the oxygen adsorption rate constant distribution was determined by the method described above.

〔Specific surface area〕
The specific surface area (m ² /g) determined by the BET method from the CO ₂ adsorption isotherm at 25° C. was determined as follows. That is, using a specific surface area/pore distribution measuring device (BELSORP (registered trademark)-MAX (trade name) manufactured by Microtrac Bell Co., Ltd.), the molecular sieve carbon obtained in Examples and Comparative Examples was measured under reduced pressure. After heating at 250°C for 3 hours under vacuum (degree of vacuum: 0.1 kPa or less), the carbon dioxide adsorption isotherm of the carbon molecular sieve at 25°C was measured.
Using the obtained carbon dioxide adsorption isotherm, calculate a straight line in the region of relative pressure P/P0 = 0.01 or more and 0.1 or less using the multi-point method from the obtained curve by BET analysis, and calculate this straight line. The specific surface area was calculated from

[Maximum center of main peak of oxygen adsorption rate constant distribution]
Using the carbon molecular sieves obtained in Examples and Comparative Examples, the maximum center (sec ^-1 ) of the main peak of the oxygen adsorption rate constant distribution was determined by the method described above.

[Volume of pores with pore entrance diameter of 0.37 nm or more and 0.46 nm or less]
Using the molecular sieve carbon obtained in Examples and Comparative Examples, the volume (mL/g) of pores having a pore entrance diameter of 0.37 nm or more and 0.46 nm or less determined by the molecular probe method was determined by the above method. I asked for it.

[Evaluation of gas separation performance]
Gas separation performance was evaluated by the amount of product nitrogen generated per ton of molecular sieve carbon (Nm ³ /h·t) and nitrogen yield (%) by a nitrogen generator using a pressure swing adsorption method.

In addition, the amount of product nitrogen generated per 1 ton of molecular sieve carbon is calculated using the following formula, where M (t) is the mass of molecular sieve carbon used in the nitrogen generator, and Q (Nm ³ /h) is the amount of product nitrogen generated per hour. It is shown in (6).
Product nitrogen generation amount (Nm ³ /h・t)=Q(Nm ³ /h)/M(t)...(6)
The nitrogen yield represents the proportion of nitrogen that can be separated and recovered from the nitrogen in the supplied raw material gas, and is expressed by the following formula (7).
Nitrogen yield (%) = 100 × (Product nitrogen generation amount per hour (NL/h) / (Product nitrogen generation amount per hour (NL/h) + Exhaust gas amount per hour (NL/h))) ...(7)

Further, as the nitrogen generator, a gas separation device as shown in the schematic diagram of FIG. 7 was used, and the gas separation device was operated according to the following operating operations.

First, in the gas separation device, each valve 13a, 13b, 14a, 14b, 15, 16a, 16b, and 18 is closed. Next, the raw material air compressed by the compressor 11 is supplied to the raw material tank 12, the valve 13a is opened, and the air is introduced into the adsorption tower A. Thereafter, oxygen is adsorbed in the adsorption tower A, and by opening the valve 16a, unadsorbed gas (mainly nitrogen) is supplied to the product tank 17 through the valve 16a. Thereafter, by closing the valve 16a and opening the valve 18, mainly nitrogen gas in the product tank 17 is discharged. At this time, adsorption tower A becomes pressurized. Along with this operation, the same operation as above is performed to discharge the oxygen that has been adsorbed in the adsorption tower B in advance. That is, by opening the valve 14b, the oxygen adsorbed in the adsorption tower B is discharged from the valve 19 through the valve 14b. At this time, adsorption tower B becomes atmospheric pressure. Adsorption towers A and B are maintained in this state, and after 59 seconds have elapsed, valves 13a and 14b are closed, and valve 15 is opened, thereby equalizing the pressure in adsorption towers A and B. The pressure equalization time is 1 second. After pressure equalization, by closing the valve 14b and opening the valves 13b, 16b, and 14a, the adsorbed oxygen gas from the adsorption tower A is discharged from the outlet 19, and oxygen adsorption in the adsorption tower B progresses. . By repeating this operation, product nitrogen is continuously extracted.
Note that the opening degree of the valve 18 is kept constant during the series of operations. By adjusting the opening degree of the valve 18, the flow rate of the product nitrogen taken out can be changed, and thereby the product nitrogen concentration can be adjusted.

Here, in this specification, the product nitrogen concentration is 99.99%.

〔Measurement result〕
Half width of main peak of oxygen adsorption rate constant distribution, specific surface area, maximum center of main peak of oxygen adsorption rate constant distribution, volume of pores with pore entrance diameter of 0.37 nm or more and 0.46 nm or less, product Table 1 shows the results of nitrogen generation amount and nitrogen yield.

As shown in Table 1, the half-width of the main peak of the oxygen adsorption rate constant distribution is 0.35 s ^-1 or less, and the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C is 300 m ² /g or more and 600 m ² /g or less (Examples 1 to 8) have significantly improved gas separation performance compared to molecular sieve carbons (Comparative Examples 1 to 5) that do not meet the above conditions. I understand.

That is, the half width of the main peak of the oxygen adsorption rate constant distribution is 0.35 sec ^-1 or less, and the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C is 300 m ² /g or more. It can be seen that molecular sieve carbon having a particle size of 600 m ² /g or less has significantly improved gas separation performance between oxygen and nitrogen compared to molecular sieve carbon that does not meet the above conditions.

1...Valve, 2...Valve, 3...Valve, 4...Pressure sensor, 5...Gas reservoir, 6...Sample cell, 7...Molecular sieve carbon, 8...Inlet, 9...Outlet, A...Adsorption tower, B...Adsorption Column, 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, 20... Glass container, 21... Pinhole, 22... Weighing bottle containing carbon molecular sieve, 23... Punching plate, 24... Petri dish filled with carbon disulfide or chloroform.

Claims (7)

The half width of the main peak of the oxygen adsorption rate constant distribution is 0.35 sec ^-1 or less, and the specific surface area determined by the BET method from the CO ₂ adsorption isotherm at 25°C is 300 m ² /g or more and 600 m ² /g or less ,
The gas to be separated is air, and carbon molecular sieve selectively adsorbs oxygen from the air . The molecular sieve carbon according to claim 1, wherein the maximum center of the main peak of the oxygen adsorption rate constant distribution is 0.030 sec ^-1 or more and 0.250 sec ^-1 or less. The molecular sieve carbon according to claim 1, wherein the volume of pores having a pore entrance diameter of 0.37 nm or more and 0.46 nm or less as determined by a molecular probe method is 0.150 mL/g or more. The molecular sieve carbon according to claim 1, comprising non-graphitizable carbon. a step of carbonizing raw materials to obtain carbide;
an activation step of activating the carbide to obtain an activated material;
The method for producing carbon molecular sieve according to any one of claims 1 to 4 , comprising a firing step of firing the activated material. A gas separation device for separating oxygen from air by pressure swing adsorption method,
An apparatus comprising the molecular sieve carbon according to any one of claims 1 to 4 as an adsorbent in the pressure swing adsorption method. A gas separation device for separating oxygen from air by a temperature swing adsorption method,
An apparatus comprising the molecular sieve carbon according to any one of claims 1 to 4 as an adsorbent in the temperature swing adsorption method.