JPH0781915A - Plate-shaped molecular sieve carbon and production thereof - Google Patents

Abstract

PURPOSE:To produce a molecular sieve carbon formed body having high performance as a molecular sieve with inexpensive starting materials through simple processes. CONSTITUTION:Pitch fibers made infusible are preformed into a plate shape and the resulting plate-shaped preform is carbonized at 760-900 deg.C in an inert gaseous atmosphere to produce the objective plate-shaped molecular sieve carbon made of fibrous molecular sieve carbon whose micropore diameter distribution is ranged within 0.28nm to <0.43nm.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is used for gas separation technology such as air separation by pressure swing adsorption method (PSA method), hydrogen purification from off gas, recovery separation of active ingredient, methane separation from fermentation gas, etc. And a method for producing the same.

[0002]

2. Description of the Related Art In recent years, technological development for separating and refining specific components from various mixed gases has been active. Among them, the method called PSA is expected to be applied to many applications because the device is compact and the running cost is low. In particular, air separation for separating and recovering nitrogen from air using hydrophobic molecular sieving carbon is expected to rapidly expand the market as the demand for nitrogen increases.

The characteristics of molecular sieving carbon are 0.3 to 0.5, whereas ordinary activated carbon has micropores of 1 to 3 nm.
The micropores are as small as nm and have a narrow distribution. Regarding the method of producing molecular sieving carbon,
Although various methods have been proposed, they are roughly classified into 5 categories, 1) impregnation method, 2) thermal decomposition method, 3) activation method, 4) thermal decomposition carbon vapor deposition method, and 5) thermal contraction method. be able to.

The impregnation method refers to JP-A-59-45914, JP-A-61-191510, and JP-A-62-1.
As disclosed in Japanese Patent No. 76908, hydrocarbons (pitch, resin, etc.) that are liquid in the temperature range from room temperature to about 300 ° C. are permeated into the base material such as activated carbon, and then carbonized. Then, pyrolytic carbon is released from the hydrocarbon and the pyrolytic carbon narrows the micropores of the substrate. However, it is very difficult to control the amount of hydrocarbon permeation into the base material, and the generated pyrolytic carbon cannot be controlled, resulting in unstable product molecular sieving carbon quality (poor reproducibility), resulting in poor product yield. It has the disadvantage of low rate.

The thermal decomposition method is a heat treatment (carbonization) of a carbonaceous substrate in an inert gas atmosphere, as disclosed in JP-A-62-59510 and JP-A-63-139909. It is a method of producing molecular sieving carbon simply by performing. This method is easier to stabilize the quality than the impregnation method. However, it is necessary to stabilize the quality of the carbonaceous base material, and thus it is inevitable to use an expensive vinylidene chloride resin or phenol resin as the carbonaceous base material.
Further, the method for preparing these resins is also very complicated.

In order to solve the drawback that an expensive material has to be used, JP-A-60-227832 and Japanese Patent Publication No.
Japanese Patent Laid-Open No. 58975 discloses a method for producing molecular sieving carbon using coal or pitch as a carbonaceous base material. However, the molecular sieving carbon obtained by this method is 0.5 nm.
It has molecular sieving properties only for molecules of the above size, and its performance is insufficient for use in air separation applications, separation of methane from fermentation gas, and the like.

The pyrolytic carbon deposition method is a method in which a carbonaceous substrate and a hydrocarbon gas are brought into contact with each other at a high temperature, and pyrolytic carbon released from the hydrocarbon is deposited near the entrance of the micropores of the carbonaceous substrate. A method for adjusting micropores in a carbonaceous substrate. According to this method, since the amount of pyrolytic carbon generated can be controlled by the concentration and temperature of the hydrocarbon gas, it is considered possible to produce stable molecular sieving carbon.

Japanese Patent Publication No. 52-18675 discloses a method for producing molecular sieving carbon by a pyrolytic carbon deposition method using coke having a volatile content of 5% or less as a carbonaceous substrate. However, when producing coke by heat treatment starting from coal or the like, the obtained coke has a wide micropore size distribution, and therefore the carbonaceous substrate suitable for the pyrolytic carbon vapor deposition method has good reproducibility, And it is difficult to obtain efficiently. Japanese Patent Laid-Open No. 1-502743 discloses that
A method is disclosed in which coke as a carbonaceous substrate is activated with an inert gas containing water vapor to forcibly generate micropores, and then pyrolytic carbon is deposited on the generated micropores. However, this method is also difficult to control the micropore diameter in terms of the pore distribution of the activated coke used in the pyrolytic carbon deposition method.

On the other hand, in JP-A-60-171212, a hydrocarbon which releases pyrolytic carbon from a carbonaceous substrate having a very fine pore distribution of 0.50 to 0.55 nm at 500.degree. A method of chemically adsorbing and then performing high temperature treatment (heat shrinkage method) to deposit pyrolytic carbon on the micropores is disclosed below. This method is a method of producing molecular sieving carbon of stable quality by utilizing the controllability of the pyrolytic carbon deposition method and selecting the carbonaceous substrate more strictly. However, the disadvantage that the manufacturing process is complicated and complicated is inevitable. In addition, the micropore diameter is 0.5 to
The carbonaceous base material adjusted to 0.55 nm is already itself a molecular sieving carbon, and is considerably expensive as a raw material.

On the other hand, a method for producing fibrous molecular sieving carbon as opposed to granular molecular sieving carbon is disclosed in JP-A-57-1010.
No. 24 publication. This is produced by melt-spinning a coal depolymerized product by a special production method, inactivating it and then mildly activating it. However,
Activation from the outside of the fiber using water vapor or the like cannot exhibit excellent performance such as air separation for the purpose of the present invention. Also in the examples of the above publications, only the separation of benzene / cyclohexane is described. In addition, Japanese Patent Publication No. 3-80055 discloses a method for producing fibrous molecular sieving carbon. The pitch fiber is infusibilized, and further heated in an inert gas atmosphere to about 500 to 750 ° C. and heat treated.
By this heat treatment (carbonization treatment), oxygen-containing compounds such as CO and CO ₂ are released to the outside of the fiber to form pores in the fiber and to impart strength. However, under the described conditions, there is a problem that the adsorption capacity is inferior to that of the granular molecular sieving carbon.

The fibrous molecular sieving carbon has micropores directly formed on the surface of the fiber, and therefore has a characteristic that the effective geometric surface area is larger than that of the granular molecular sieving carbon. , Efficient. On the other hand, in the case of the fibrous form, the handling property was poor in filling and the like as compared with the granular molecular sieving carbon, and the productivity was poor because the product was processed in a low bulk density state during the production.

Since the fibrous molecular sieving carbon produced in this manner is a fiber, it has weak strength as a fiber aggregate, poor workability, is difficult to handle, is easily scattered, has poor shape-maintaining properties, and has a void. Due to the drawbacks of high porosity and low packing density, there is a problem of poor reproducibility of porosity and packing density.

On the other hand, conventionally, as the adsorbent, one having a granular carbon raw material or one having an activated carbon fiber sheet has been used, but it has a molecular sieve carbon fiber. Plate-like molecular sieving carbon is not known.

In Japanese Patent Laid-Open No. 61-12918, a sheet obtained by making a paper from organic fibers for producing carbon fibers and pulp is impregnated with a solution of an organic polymer substance, dried and carbonized by heating to obtain a porous film. To produce a high quality carbon plate,
JP-A-54-64105 discloses a method for producing an adsorptive sheet in which activated carbon fibers and other fiber materials are dispersed in water to make a paper. Further, a lump-shaped activated carbon fiber aggregate is disclosed in JP-A-2-38374. However, none of these porous carbon materials has a molecular sieving property.

In order to obtain a compact molecular sieve carbon material having a good handling property for an adsorption column,
It is necessary to produce a molecular sieve carbon material of a molded body that matches the form of the adsorbent. If you try to obtain a molded product from the conventional method for producing molecular sieving carbon, it will go through complicated steps,
There is a problem that the molecular sieving property of the plate-shaped molded product is not uniform.

[0016]

DISCLOSURE OF THE INVENTION The present invention provides a high-performance molecular sieve carbon plate-shaped molded body easily, at low cost, and with high reproducibility without using an expensive material or introducing an activation process. It is to manufacture well. That is, the present invention retains the handling property more than granular molecular sieving carbon, the molecular sieving property, and the adsorption capacity, and has a larger effective geometric surface area per filling volume as compared with the granular molecular sieving carbon. It is an object of the present invention to provide a plate-like molecular sieving carbon and a method for producing the same. According to the present invention, since the activation process is not performed, the yield is also improved. Another object of the present invention is to provide a molecular sieving carbon compact having high strength.

[0017]

Means for Solving the Problems The present inventors have achieved the present invention as a result of diligent study by paying attention to the micropore size distribution generated in the carbonization treatment of excessively infusibilized pitch fiber. is there.

When the pitch fibers are infusibilized in an oxidizing atmosphere under the oxidizing conditions of the infusibilizing conditions or higher at which the carbon fiber strength is maximized, an increase in oxygen adsorption capacity is observed even at 750 ° C. or higher. It was found that the pore size was narrowed. Further, it was found that the molecular sieving property is hardly deteriorated even when a molded body composed of an excessively infusible fiber lump is carbonized. In addition, when it is molded into a plate shape, the filling amount can be increased, and at least one surface of the plate shape has irregularities, and the structure has continuous recesses,
It has the effect of reducing the pressure loss in the adsorption layer.

That is, the pitch fibers are excessively infusibilized in an oxidizing atmosphere, the infusibilized pitch fibers and the pitch binder are mixed and preformed into a plate shape, and the pitch binder is melted to bond the fibers together. After being heated up to a predetermined shape, the temperature is raised to 760 to 900 in an inert gas atmosphere.
Carbonization treatment is performed at ℃ to obtain a plate-shaped molecular sieve carbon molded product.
Further, in the case of narrowing the micropore diameter, a plate-shaped molecular sieving carbon compact may be produced by a pyrolytic carbon deposition method.

The plate-shaped molecular sieving carbon molded product obtained by this method has a narrow micropore size of 0.28 to less than 0.43 nm, and a plate-shaped molecular sieving carbon molded product having a form suitable for an adsorption column can be produced. Therefore, it has been clarified that it can exhibit excellent performances such as air separation and separation of methane from fermentation gas. In addition, the micropore diameter in the present invention refers to pores having a diameter of 2 nm or less.

In addition, after the tar pitch is spun as a raw material, the infusibilizing treatment condition in the usual carbon fiber production is
That is, under the infusibilizing treatment conditions that maximize the carbon fiber strength, when carbonization treatment is performed at a temperature of 500 to 750 ° C., molecular sieving carbon having a little molecular sieving property can be prepared, but the adsorption capacity is low and the molecular sieving is small. The characteristics were also bad. Further, if the infusibilization treatment is excessively performed, there is a problem that the fiber strength is lowered because it is fibrous.

As a result of intensive studies to solve the above-mentioned problems, the present inventors obtained an infusibilized fiber that was excessively infusibilized, and then formed it into a desired shape, preferably a plate shape, and then used an inert gas. It has been found that plate-like molecular sieving carbon having a high adsorption capacity and excellent molecular sieving property can be obtained by carbonizing at a temperature of 760 to 900 ° C. in the atmosphere, and completed the present invention.

That is, the present invention provides a molecular sieving carbon molded body composed of fibrous molecular sieving carbon and having a micropore size distribution of the molecular sieving carbon in the range of 0.28 nm or more and less than 0.43 nm, The molded product is preferably in the form of a plate, and at least a part of the surface of the molded product has irregularities, and in the case of a plate-shaped molecular sieve carbon molded product, at least one surface has irregularities, and the recesses have a continuous structure. Is desirable. Further, as the molded body, a plate-shaped body may be used as it is or a honeycomb-shaped body may be used.

In the present invention, the pitch fibers are excessively infusibilized in an oxidizing atmosphere, the infusibilized pitch fibers and the pitch binder are mixed, and preferably preformed into a plate shape, and the fibers are bonded to each other. For that purpose, the method for producing a porous molecular sieve carbon molded body is characterized in that the pitch binder is heated until it is melted and molded into a predetermined shape, and then carbonized in an inert gas atmosphere of 760 to 900 ° C. Desirably, the infusibilized pitch fiber has an oxygen content of 10 to 15% by weight and a fiber length of 0.02 to 20 m.
m, the fiber diameter is 4 to 60 μm, and the apparent density of the plate-shaped body is 0.
It is preferably 1 g / cm ³ or more, more preferably more than 0.6 g / cm ³ .

[0025]

The plate-like molecular sieving carbon of the present invention and the method for producing the same will be described in more detail below. The plate-like molecular sieving carbon of the present invention is composed of fibrous molecular sieving carbon, which will be described in detail later, and its micropore size distribution is 0.28 nm or more and less than 0.43 nm. Although this molded body is not limited, it is preferable to make it into a plate shape, and it is preferable that at least one surface of the plate body has irregularities and the recessed portions are continuous as shown in FIG. Is.

Next, the method for producing the plate-like molecular sieving carbon of the present invention will be described in detail. The raw material used in the present invention is preferably tar pitch. This is because the pitch is cheaper as a raw material than the polyacrylonitrile-based, phenol resin-based, and cellulose-based materials in which activated carbon fibers are conventionally manufactured, the product yield is high, and the degree of infusibilization is easy to adjust. The reason is that a product having a narrow micropore size distribution can be prepared. In addition, the pitch used here is preferably one having a high softening point which is made heavy so as to be suitable for spinning, infusibilization and carbonization in the subsequent steps, and particularly one having a softening point of 200 ° C. or higher is suitable. preferable. As such a pitch, for example, a pitch prepared by subjecting to purification, solvent extraction, distillation, heat treatment, etc., which is proposed in Japanese Patent Publication No. 61-002712, has a substantially optically isotropic pitch. Are suitable. This is because the carbon material obtained from the isotropic pitch is amorphous,
This is because it is easy to control the pore structure.

Next, pitch spinning can be carried out by a known method, for example, melt extrusion spinning, centrifugal spinning, or the like. The fiber diameter of the pitch fiber is preferably 4 μm to 60 μm. Further, the apparent density of the plate-shaped molecular sieve carbon molded product of the present invention is 0.
It is preferably 1 g / cm ³ or more, more preferably more than 0.6 g / cm ³ . This is because if the apparent density of the fiber mass is too low, the strength of the molded body cannot be maintained.

The fiber length is preferably 0.02.
It is not less than mm and not more than 20 mm. This is because if the fiber length is too short, the effect of the morphology of the fiber is small, a large amount of binder is required, the porosity is lowered, and the molecular sieving performance is deteriorated. If the fiber length is too long, the porosity tends to increase,
Moreover, the homogeneity of the molded body is deteriorated. The plate thickness is preferably 1 mm or more and 10 mm or less. This is because if the plate thickness is too thin, the strength of the molded product will decrease, and if the plate thickness is too thick, the homogeneity of the molded product will deteriorate and the molecular sieving property will deteriorate.

The infusibilizing treatment is carried out at a temperature of about 150 to 350 ° C. in an oxidizing atmosphere in order to maintain the shape when carbonizing the obtained pitch fiber at a high temperature. In the production of (1), the oxidation treatment is usually performed under the infusibilizing conditions that maximize the carbon fiber strength during carbonization. On the other hand, as a method of excessive infusibilizing treatment in the present invention, a longer time than the usual infusibilizing conditions during carbon fiber production, high temperature,
Alternatively, the treatment is performed with a high oxidizing gas concentration. This infusibilization treatment can be performed by heat treatment in a gas atmosphere of an oxidizing gas such as air, oxygen, nitrogen dioxide, or ozone.

As a method of forming the fiber into a plate shape, for example, the infusible fiber and the binder are mixed, charged into a flat-bottomed mold container in a predetermined amount, preformed, and then higher than the softening point of the binder. The temperature is raised to a temperature, the binder is melted, and the infusible fibers are bonded to each other to be molded. Desirably, pressure is applied during this molding. When the surface of the plate-like molecular sieving carbon is provided with irregularities, it is desirable to provide the flat-bottomed mold container surface with irregularities of a predetermined shape. At this time, it is preferable that the recess has a continuous structure. By providing the unevenness in this manner, the gas flowability can be improved and the pressure loss during adsorption can be reduced.

That is, the effect of the continuous structure of the concave portions is to secure the flow path of the gas, and it has the effects of reducing the pressure loss during adsorption and increasing the desorption rate of the adsorbed gas during desorption. Also, since the gas does not have to flow inside the molded body,
It is possible to increase the density of the molded body and increase the filling amount when filling the adsorption tank. Since it is plate-shaped, there is an effect that gas can be easily diffused from the gas flow path into the inside of the molded body.

The binder has a softening point of 80 to 15
Coal-based pitch of about 0 ° C., phenol resin, furan resin, epoxy resin and the like can be used, but coal-based pitch having a softening point of about 80 to 150 ° C. is preferable in order not to deteriorate the molecular sieving performance. The amount of the binder acting as an adhesive is 1 part by weight or more based on 100 parts by weight of the fiber when the residual carbon content of the binder (defined by the residual amount when the binder is heated to 1000 ° C. in an inert gas atmosphere) is 100 parts by weight. Three
It is preferably used in an amount of 0 parts by weight or less. This is because if it is more than 30 parts by weight, the porosity is lowered and the molecular sieving performance is deteriorated, which is not preferable, and if it is less than 1 part by weight, there is no adhesive effect.

The plate-shaped formed body made of the excessively infusibilized fiber thus obtained is treated under an inert gas atmosphere at a temperature of 760 ° C. or higher and 900 ° C. or lower, more preferably 80 ° C.
0.28, which has a large adsorption capacity and excellent molecular sieving property, by being heated to 0 ° C or higher and 900 ° C or lower and carbonized
A plate-like molecular sieving carbon composed of fibers having micropores of not less than nm and less than 0.43 nm can be prepared. 760 ° C
If it is less than 1, the micropore size distribution becomes wide, and if it exceeds 900 ° C., the micropore size becomes too narrow, and the adsorption rate is greatly reduced, which is not suitable for practical use.

The heating and carbonizing time is preferably 5 minutes or more and 8 hours or less, more preferably 10 minutes or more and 2 hours or less. If it is less than 5 minutes, the micropore size distribution is wide, and if it exceeds 8 hours, the micropore size becomes too narrow, and the adsorption rate is large, which is not suitable for practical use.

The plate-like molecular sieving carbon produced by the production method of the present invention hardly adsorbs n-butane (minimum molecular diameter 0.43 nm), and oxygen (minimum molecular diameter 0.28 nm),
Well adsorbs carbon dioxide (minimum molecular diameter 0.33 nm),
Since the micropore size distribution is narrow, it is excellent in separating oxygen and nitrogen, and separating carbon dioxide and methane. This micropore size distribution can be adjusted by adjusting the carbonization conditions (temperature, time). The micropore size distribution can be further narrowed by increasing the carbonization temperature.

Further, in the present invention, there is provided a manufacturing method in which pyrolytic carbon is vapor-deposited on the plate-like molecular sieving carbon obtained by the carbonization treatment. Since the micropore size distribution has already been adjusted, mild conditions can be used for the deposition of pyrolytic carbon. That is, the carbonized plate-shaped molded body is heated to 600 to 850 ° C. in an inert gas atmosphere, and subsequently at the temperature under an inert gas atmosphere containing an aromatic hydrocarbon and / or an alicyclic hydrocarbon. When treated with, the pyrolytic carbon released from the aromatic hydrocarbon or the alicyclic hydrocarbon is vapor-deposited near the entrance of the micropores. By controlling the vapor deposition treatment temperature, the vapor deposition treatment time, the concentrations of aromatic hydrocarbons and alicyclic hydrocarbons, 0.28 nm or more,
Plate-like molecular sieving carbon having micropores of less than 0.43 nm can be produced with good reproducibility and at low cost.

The deposition temperature of the pyrolytic carbon is 600-8.
The temperature is 50 ° C, preferably 700 to 750 ° C. 600
This is because if the temperature is lower than 0 ° C, the amount of pyrolytic carbon generated is small, and thus it takes a huge amount of time for vapor deposition. If it exceeds 850 ° C., on the contrary, the amount of pyrolytic carbon generated is too large, and the optimum pyrolytic carbon deposition time becomes too short, so that the micropore diameter narrowing rate cannot be controlled. Examples of aromatic hydrocarbons include benzene, xylene, toluene, ethylbenzene, naphthalene, and examples of alicyclic hydrocarbons include cyclohexane. Alternatively, a mixed gas thereof may be used, and the concentration of the aromatic hydrocarbon and the alicyclic hydrocarbon in the inert gas is 3
-15% is preferable. Since the vapor deposition treatment time varies depending on the vapor deposition time, the concentration of aromatic hydrocarbons, the equipment used, etc., it may be selected from various combinations, but in industrial production, it should be between 10 and 120 minutes. Is preferable from the viewpoint of quality stability.

A high-quality porous molecular sieving carbon molded body can be obtained by the above-mentioned manufacturing method. However, after the vapor deposition treatment, subsequently, in an inert gas atmosphere, the vapor deposition treatment temperature or higher,
It is even better to keep the temperature below 900 ° C. The effect is to firmly fix the micropore size distribution obtained by the vapor deposition process. Further, holding at high temperature also has the effect of narrowing the micropore diameter exceeding 0.4 nm, and therefore has the effect of making the distribution of micropores generated by the vapor deposition treatment sharper. This effect cannot be obtained below the vapor deposition treatment temperature.

By the method described above, it is possible to easily and reproducibly produce a plate-shaped molecular sieve carbon molded product having a micropore size of 0.28 nm or more and less than 0.43 nm and a narrow micropore size distribution.

The plate-like molecular sieving carbon molded product of the present invention is made of fibrous molecular sieving carbon and therefore has a high strength. Furthermore, the plate-shaped molecular sieve carbon molded body of the present invention can be obtained in the form of a molded body according to the application, is excellent in workability and handleability, can be homogeneously filled, and has an adsorption amount per unit volume. Since it is large and the gas flow path is secured, pressure loss during adsorption / desorption is small. Also, the strength of the molded product is high, the loss of pulverization is small, and the number of adsorption / desorption cycles is high.
Suitable for use in SA etc.

[0041]

EXAMPLES The present invention will be specifically described below based on examples. Example 1 Tar pitch was used as a raw material, and a softening point of 215 ° C. (temperature gradient method) containing 56% by weight of benzene insoluble matter was melt-spun to obtain an optically isotropic pitch (precursor pitch), thereby obtaining pitch fibers. The pitch fiber obtained was a continuous long fiber and had a diameter of 14 μm. This was infusibilized to 345 ° C. under air flow. The oxygen content based on the total fiber weight of the obtained infusible fiber was 13.1% by weight.

The infusibilized fiber thus obtained was subjected to 3 by an automatic fiber cutting machine.
It was cut to a length of mm and crushed by a rotary disk type coffee mill grinder to obtain short fiber-like (average fiber length 0.4 mm) infusible short fibers. Pitch fine particles having an average particle diameter of 5 μm per 100 parts by weight of short fibers (pitch binder softening point 1
(09 ° C) is mixed in advance with 8 parts by weight in terms of residual carbon content,
A predetermined amount was charged into a flat-bottomed mold container having a recess of 5 mmφ and a trapezoid of 5 mmφ at 15 mm intervals and pre-molded by applying pressure (0.1 kgf / mm ² ) to the upper lid plate. After preforming, the temperature was raised to 150 ° C., the binder was melted, and the infusible fibers were adhered to each other for molding. The obtained molded body is shown in FIG. In FIG. 1, (a) shows a single body, (b)
Indicates the laminated composite.

The obtained plate-shaped infusible fiber molding was heated to 850 ° C. in an inert gas atmosphere (nitrogen gas flow), carbonized for 0.5 h, and having a plate thickness of 6 mm including a convex portion. A porous molecular sieve carbon compact was obtained. The apparent density of the molded body was 0.7 g / cm ³ . The carbonization yield at 850 ° C. treatment was 79.5% by weight based on the infusible fiber molding. A part of the obtained porous molecular sieving carbon compact was cut out, and the micropore size distribution and the molecular sieving property were evaluated. In order to evaluate the molecular sieving property, oxygen (minimum molecular diameter: 0.28 nm), nitrogen (minimum molecular diameter: 0.30 n)
m), carbon dioxide (minimum molecular diameter: 0.33 nm), ethane (minimum molecular diameter: 0.40 nm), n-butane (minimum molecular diameter: 0.43 nm), i-butane (minimum molecular diameter: 0.
50 nm), carbon tetrachloride (minimum molecular diameter: 0.60 nm)
The adsorption isotherm (25 ° C) was measured. For the measurement, the adsorption isotherm measuring device Bellsoap 18 by the constant volume method was used.
(Manufactured by Nippon Bell Co., Ltd.) was used. The measurement results of the coarsely crushed 850 ° C. carbonized product are shown in FIG. Also, the above 850 ℃
FIG. 3 shows the results of adsorption isotherm measurement of carbon dioxide, methane (minimum molecular diameter: 0.40 nm), and n-butane using a coarsely pulverized carbonized product.

The micropore size distribution is shown by the relationship between the cumulative micropore volume and the micropore size. The adsorption isotherm was measured for the adsorption gas, and the maximum adsorption volume of each was determined from the Dubinin-Astakhov plot, and the value was represented.
There is a large difference in the amount of adsorption of n-butane, methane and carbon dioxide, which shows excellent equilibrium separation type molecular sieving property.
The produced plate-like fiber lump molecular sieving carbon has a carbon content of 0.43 nm.
It was found that they do not have the above-mentioned micropore size substantially.

FIG. 4 compares the adsorption rates of nitrogen and oxygen of the 850 ° C. carbonized product. The measurement method is to put a molecular sieving carbon sample in a container of known volume, evacuate the system, introduce a gas to be adsorbed (nitrogen, oxygen), and measure the time and pressure after the introduction. Used the same Belthorpe 18 used for the measurement of the adsorption isotherm.

From FIG. 4, it is understood that the adsorption amount of oxygen reaches the equilibrium within a very short time, while the adsorption amount of nitrogen takes a very long time to reach the equilibrium. In other words, it is clear that this plate-shaped molecular sieving carbon fiber has a very good velocity separation type molecular sieving property. In addition, the plate-shaped molecular sieving carbon molded body was filled into a prismatic column having a cross section of 50 mm square and a height of 400 mm, and the spring pressure was 2.0 kg / cm.
^When air was passed through the PSA method in a state of being held down by ² in 60 seconds for 1 cycle to separate oxygen and nitrogen, the shape of the molecular sieving carbon compact was hardly disturbed even after 168 hours of use. Also, a separated nitrogen concentration of 99.5% could be achieved at a set pressure of 2.1 kg / cm ² .

Comparative Example 1 The pitch fiber obtained in Example 1 was infusibilized up to 300 ° C. under air flow. The obtained infusible fiber is cut into a length of 3 mm with an automatic cutting machine and crushed with a rotary disk type coffee mill grinder to give a short fiber-shaped (average fiber length 0.4 mm) infusibilized pitch Short fibers were obtained. Next, to 100 parts by weight of this infusibilized pitch short fiber, 8 parts by weight of pitch fine particles (binder softening point: 109 ° C.) having an average particle diameter of 5 μm were mixed in advance in terms of residual carbon content, and 5 mmφ with a depth of 1 mm at 15 mm intervals. A predetermined amount was charged into a cylindrical trapezoidal hollow flat-bottomed mold container, and pressure (0.1 kgf / mm ² ) was applied to the upper lid flat plate to perform preforming. After preforming, the temperature was raised to 150 ° C., the binder was melted, and the infusible fibers were adhered to each other for molding. Then
This plate-shaped infusible fiber molded body was heated to 690 ° C. while flowing nitrogen gas, held for 10 minutes, and then cooled.
Plate-like molecular sieving carbon was prepared. The adsorption amount of the coarsely crushed 690 ° C. carbonized product was measured. Regarding this, carbon dioxide and n-butane were adsorbed in large amounts, but i-butane was hardly adsorbed. The produced plate-like molecular sieving carbon does not substantially have a micropore size of 0.5 nm or more, but has a wider micropore size distribution than the porous molecular sieving carbon compact prepared in Example 1. I understand.

FIG. 5 shows the results of comparing the oxygen / nitrogen adsorption rates of the obtained porous molecular sieve carbon compacts. From this figure, it is understood that the molecular sieving performance is inferior to oxygen and nitrogen as compared with the porous molecular sieving carbon molded body prepared in Example 1. In addition, a plate-shaped molecular sieve carbon molded body was filled into a prismatic column having a cross section of 50 mm square and a height of 400 mm, and was pressed with a spring pressure of 2.0 kg / cm ² for 1 cycle 60 seconds by air by the PSA method. When oxygen and nitrogen were separated by passing through, the shape of the plate-shaped molecular sieving carbon compact was hardly disturbed even after 168 hours of use. However, even at the set pressure of 7.5 kg / cm ² , the concentration of separated nitrogen increased only up to 89.5%.

(Example 2) The pitch fiber obtained in Example 1 was infusibilized at 345 ° C under air flow. The obtained infusible fiber is cut into a length of 3 mm by an automatic cutting machine, and is crushed by a rotary disk type coffee mill grinder to be a short fibrous (average length 0.4 mm) infusibilized pitch short fiber. Got 8 parts by weight of fine pitch particles (pitch binder softening point: 95 ° C.) having an average particle diameter of 5 μm were mixed in advance with 100 parts by weight of the obtained infusible pitch short fiber, and a completely flat, flat-bottomed mold was obtained. A predetermined amount was charged into a container, and pressure (0.1 kgf / mm ² ) was applied to the flat plate of the upper lid to perform preforming. After preforming, raise the temperature to 150 ° C to melt the binder,
The infusible fibers were bonded together and molded. The obtained molded body was completely flat on both sides. The obtained plate-shaped infusible fiber molded body was heated to 850 ° C. while flowing nitrogen gas and carbonized to prepare a molecular sieve carbon molded body. 8
The carbonization yield at 50 ° C. treatment was 80.3% by weight based on the plate-shaped infusible fiber molding. The adsorption amount of the coarsely pulverized 850 ° C. carbonized product was measured.

There was a large difference in the amount of adsorption of n-butane and carbon dioxide, showing excellent equilibrium separation type molecular sieving property.
The produced plate-like molecular sieve carbon fiber molded product has 0.4
It was found to have substantially no micropore size of 3 nm or more. The above-mentioned plate-shaped molecular sieve carbon molded body was filled in the adsorption layer in the shape of a prism having a square cross section of 50 mm and a height of 400 mm, and was pressed with a spring pressure of 2.0 kg / cm ² for 1 cycle 60 seconds by the PSA method. When oxygen and nitrogen were separated by passing air, there was almost no disorder in the shape of the plate-like molecular sieving carbon compact even after 168 hours of use. However, at the set pressure of 6.5 kg / cm ² , the concentration finally increased to the separated nitrogen concentration of 99.5%.

Comparative Example 2 Using the infusible fiber obtained in Example 1, a felt having a thickness of 5 mm was formed. Cut this into a 50 mm square and stack it to a height of 400 mm,
When oxygen and nitrogen were separated in the form of prisms under the same conditions as in Example 1, the stacking height was reduced by 22% after 168 hours of use, and further pulverization from the molecular sieve carbon felt was observed. Halved from the performance of.

[0052]

As is clear from the above description, according to the method for producing a porous molecular sieving carbon molding of the present invention, the molecular sieving carbon having a micropore diameter of 0.28 nm or more and less than 0.43 nm is activated. It can be easily and reproducibly manufactured without a process. In addition, since there is no activation process using easily available pitch as a starting material,
High-performance molecular sieving carbon can be obtained in high yield and at low cost.

The porous molecular sieving carbon molded product obtained by the present invention is particularly excellent in the performance of steric separation type molecular sieving for methane and carbon dioxide, and the performance of rate separation type molecular sieving for oxygen and nitrogen.

The plate-like molecular sieve carbon molded product of the present invention is
Since it is composed of fibrous molecular sieving carbon, the strength of the molded product is high. Furthermore, the plate-shaped molecular sieve carbon molded body of the present invention can be obtained in the form of a molded body according to the application, is excellent in workability and handleability, can be uniformly filled, and has an adsorption amount per unit volume. Is large and the gas flow path is secured, so there is little pressure loss during adsorption and desorption. Moreover, the strength of the molded product is high, the loss of pulverization property is small, and it is suitable for use in PSA or the like, which has a large number of adsorption and desorption times.

[Brief description of drawings]

FIG. 1 is a schematic view of a plate-shaped molded body in Example 1, where (a) is a single body of the molded body and (b) is a laminated composite body thereof.

FIG. 2 is a diagram showing a cumulative distribution of micropore size distribution of a plate-shaped molecular sieve carbon molded product subjected to carbonization at 850 ° C. in Example 1. The vertical axis represents the micropore volume, and the horizontal axis represents the micropore diameter.

FIG. 3 is an adsorption isotherm of n-butane, methane, and carbon dioxide of a plate-shaped molecular sieve carbon molded product subjected to carbonization at 850 ° C. in Example 1. The vertical axis is the equilibrium adsorption amount, and the horizontal axis is the gas pressure.

FIG. 4 is a diagram expressing the adsorption rates of oxygen and nitrogen of a plate-like molecular sieving carbon molded product subjected to carbonization at 850 ° C. in Example 1 as a change in adsorption amount with time.

FIG. 5 is a diagram expressing the adsorption rates of oxygen and nitrogen of a plate-shaped molecular sieving carbon compact subjected to carbonization at 690 ° C. in Comparative Example 1 as changes in adsorption amount with time.

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location D01F 9/14 512 (72) Inventor Hiroyuki Ougi Sugihiro Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Stock Corporate Technology Research Headquarters (72) Inventor Masami Ueda 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Headquarters

Claims (4)

[Claims] 1. A fibrous molecular sieving carbon having a micropore size distribution of 0.28 nm or more and 0.4 or more.
A plate-like molecular sieving carbon characterized by having a plate shape in the range of less than 3 nm. 2. The plate-like molecular sieving carbon according to claim 1, wherein the plate-like molecular sieving carbon has a structure in which at least one surface has irregularities and the recesses are continuous. 3. An infusibilized pitch fiber is molded into a plate shape and subjected to an adhesive treatment to obtain a predetermined shape, and then 760 to 900.
A process for producing plate-like molecular sieving carbon, which comprises carbonizing at a temperature of ℃. 4. The method for producing plate-like molecular sieving carbon according to claim 3, wherein the infusibilized pitch fiber has an oxygen content of 10 to 15% by weight.