JP3334664B2 - Adsorbent for gas separation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas separation adsorbent for separating a gas mixture containing a component that is easily adsorbed (easy adsorbable component) and a component that is not easily adsorbed (hardly adsorbable component). The present invention relates to the manufacturing method. In particular, the adsorbent for gas separation of the present invention is a pressure vibration adsorption method (PS
Method A: Pressure Swing Advisor
The present invention relates to a gas separation adsorbent used for separating a gas mixture by an ion method (hereinafter abbreviated as PSA method). The gas separated and recovered by the PSA method using the adsorbent for gas separation of the present invention is, for example, oxygen gas, nitrogen gas,
There are carbon dioxide gas, hydrogen gas, carbon monoxide gas and the like.

[0002] Among them, oxygen gas is one of the most important gases among industrial gases, and is widely used mainly in iron making, pulp bleaching and the like. In particular, recently, oxygen-enriched combustion has been put to practical use in the fields of refuse combustion, glass melting, etc. for the purpose of reducing the generation of NOx which cannot be avoided by combustion in air.
The importance of oxygen gas is also increasing in terms of environmental issues.

As an industrial production method of oxygen gas, PSA
The method, the cryogenic separation method and the membrane separation method are known, but the ratio of the PSA method, which is advantageous in oxygen gas purity and cost, is increasing. Oxygen gas production by the PSA method is a method in which nitrogen gas in air is adsorbed by an adsorbent, and the remaining concentrated oxygen gas is taken out as a product. Therefore, an adsorbent capable of selectively adsorbing nitrogen gas is used as the adsorbent.

[0004]

2. Description of the Related Art When a gaseous mixture is separated using a crystalline zeolite, an easily adsorbed component is selectively adsorbed on the crystalline zeolite. For example, in the case of producing oxygen gas from air by the PSA method, air separation is performed by selectively adsorbing nitrogen in the air onto crystalline zeolite. Selective adsorption of nitrogen on crystalline zeolites occurs due to the strong interaction between the quadrupole moment of nitrogen and the electrostatic attraction with cations in the zeolite. For this reason, in the PSA method, crystalline zeolites having a large electrostatic attraction of cations and a large amount of adsorbed nitrogen are used. Agent is used. In particular, lithium-exchanged crystalline zeolite X ion-exchanged with lithium cations is excellent in selective adsorption of nitrogen, and is used as a crystalline zeolite for obtaining concentrated oxygen by the PSA method.

For example, in US Pat. No. 3,140,933, a lithium-exchanged crystalline zeolite X having an excellent adsorption coefficient of nitrogen and a separation coefficient calculated from adsorption isotherms of nitrogen and oxygen has been proposed. 25527
The performance has been reconfirmed in the official gazette.

[0006] Usually, when a gas mixture is separated, it is preferably performed in a packed bed, so that the pressure loss in the packed bed is preferably small. For example, when performing gas separation by the PSA method, crystalline zeolite is made of clay mineral, silica sol, alumina sol, etc. in order to reduce the pressure loss in the packed bed and reduce the load on the blower or vacuum pump that constitutes the PSA device. Is formed into a spherical (bead) or columnar (pellet) shape using a binder such as an inorganic binder. An organic additive may be used depending on the purpose. In this molded article, a network of macropores is formed by the crystalline zeolite and the binder. When the easily adsorbed component is adsorbed to the adsorption site of the crystalline zeolite existing in the center of the molded body, the easily adsorbed component reaches the adsorption site in the center of the molded body while diffusing through the macropores. The easily adsorbed component desorbed from the adsorption site diffuses through the macropores and is exhausted to the outside of the molded body.
In order to exhibit the expected performance of the adsorbent, several adsorbents have been proposed that can effectively utilize the adsorption site existing at the center of the molded article and increase the adsorption efficiency of the easily adsorbable components.

For example, the macropore volume is increased to 0.3 ml / g using zeolite A exchanged with calcium cation.
The zeolite compact for gas separation described above (Japanese Unexamined Patent Publication No.
No. 124539), the ratio of macropore volume / micropore volume is 1 to 4.5, and the macropore volume is 0.3 to 0.7 m.
1 / g zeolite compact (JP-A-62-2838)
No. 12). Also, an air separation method using an adsorbent in which the porosity of the adsorbent and the average diameter of macropores are controlled (Japanese Patent Application Laid-Open No. 9-308810) is exemplified.

These adsorbents improve the rate of adsorption of readily adsorbable components, such as nitrogen in the case of air separation, on crystalline zeolites and reduce the time of contact between the gas mixture and the adsorbent. No attention has been paid to the phenomenon in which the adsorbed easily adsorbed components are desorbed under reduced pressure. In the PSA method, since adsorption and desorption are repeated, the performance of the adsorbent cannot be exhibited unless the diffusion rate of the easily adsorbed component at the time of desorption is improved as well as the diffusion speed of the easily adsorbed component at the time of adsorption. Therefore, none of the adsorbents can be said to be adsorbents for gas separation in which the utilization factor of the adsorbent is sufficiently increased.

Further, the shape of the adsorbent for gas separation is as follows:
A columnar or beaded shape is common. Cylindrical compacts are usually extruded, and bead-shaped compacts are usually formed by rolling granulation using centrifugal force, but the macropores inside the compact are generally crushed. In addition, such a problem in molding is more likely to occur when a plate-like clay such as kaolin-type or bentonite-type clay is used as a binder. Such an adsorbent has a large gas diffusion resistance inside the molded body and cannot be effectively used up to the center of the adsorbent.

[0010]

When the easily adsorbed component is adsorbed on the crystalline zeolite, it is an exothermic process. However, when the easily adsorbed component is desorbed from the crystalline zeolite, the process is an endothermic process. Requires more energy than during adsorption. Therefore, unless the easily adsorbed components desorbed from the crystalline zeolite are quickly discharged to the outside of the adsorbent, the expected gas separation performance cannot be exhibited. In particular, when the amount of the easily adsorbed component adsorbed on the crystalline zeolite is large, a higher desorption speed is required in order to discharge a larger amount of the easily adsorbed component to the outside of the adsorbent during desorption. Another important factor is that the rate of adsorption when adsorbing easily adsorbable components is high. Furthermore, the adsorbent for gas separation is used in a state where water is removed (activated state), but crystalline zeolite has a very strong affinity for water, and there is a concern that moisture in the surrounding atmosphere may be reabsorbed. If moisture remains in the adsorbent due to moisture absorption, the gas adsorption site will be occupied by water, adversely affecting gas separation, and the expected performance will not be obtained.

For example, when a lithium-exchanged faujasite-type zeolite is used as the crystalline zeolite used for the air separation by the PSA method, the amount of nitrogen adsorbed is large, so that a crystalline zeolite exchanged with calcium or the like is used. It is necessary to absorb and desorb a large amount of nitrogen,
Unless the diffusion rate of nitrogen at the time of adsorption / desorption is sufficiently improved, the performance of the adsorbent cannot be sufficiently exhibited. In addition, when the time of the adsorption / desorption step is shortened in the PSA operation, it is necessary to absorb and desorb nitrogen in a short time, and an adsorbent having an improved diffusion rate at the time of adsorption / desorption must be used. Not enough performance. Furthermore, the water content of the adsorbent must be as low as possible so as not to impair the original performance of the adsorbent.

[0012] An object of the present invention is to set conditions for desorbing easily adsorbable components in order to reduce the power consumption of a PSA device when separating a gas mixture, particularly when performing gas separation by the PSA method. An object of the present invention is to provide a gas separation adsorbent which has macropores having a suitable average pore diameter and has an excellent diffusion rate of easily adsorbable components during desorption.
In addition, while providing macropores that are advantageous for absorption and desorption of easily adsorbable components, it has excellent strength physical properties such as pressure resistance,
It is also an object of the present invention to provide a gas separation adsorbent with a low water content of the adsorbent. Further, the present invention provides a production method capable of easily obtaining such an adsorbent for gas separation.

[0013]

The present inventors have conducted intensive studies on the macropore structure of the adsorbent for gas separation and the diffusion of easily adsorbable components in the macropores.
In an adsorbent composed of a crystalline low-silica faujasite-type zeolite having an iO ₂ / Al ₂ O ₃ molar ratio of 1.9 or more and 2.1 or less and a binder, the average pore diameter of the macropores indicates that the easily adsorbed component. The total volume of pores having a pore diameter that is equal to or greater than the mean free path of the easily adsorbable component at the time of desorption and is equal to or greater than the mean free path of the easily adsorbable component occupies 70% or more of the total volume of all macropores. It has been found that the adsorbent for gas separation is excellent in the absorption / desorption performance of the easily adsorbable component, particularly in the diffusion rate of the easily adsorbable component during desorption. Furthermore, zeolite crystal SiO ₂ / A
a crystalline low-silica faujasite-type zeolite having a l ₂ O ₃ molar ratio of 1.9 or more and 2.1 or less, and binding of 5 to 30 parts by weight based on 100 parts by weight of the low-silica faujasite zeolite on an anhydrous basis The bulk density is 0.8
It was found that the desired adsorbent for gas separation was obtained by kneading and kneading so as to obtain a gas adsorbent of 1.0 to 1.0 kg / liter, followed by molding, firing, ion exchange, and activation. It has been completed.

Hereinafter, the present invention will be described in detail. The adsorbent for gas separation of the present invention has a SiO ₂ / Al ₂ O ₃ molar ratio of 1.
In an adsorbent for gas separation comprising a crystalline low-silica faujasite-type zeolite of 9 or more and 2.1 or less and a binder, the average diameter of macropores is such that the easily adsorbable component is desorbed from the adsorbent. Greater than the average free path of
The adsorbent for gas separation, wherein the total volume of macropores having a diameter equal to or greater than the mean free path of the easily adsorbable component occupies 70% or more of the total volume of all macropores.

For example, PS which repeats the adsorption process and the desorption process
When the gas separation is performed by the method A, the adsorption process is in a pressurized state, and molecular diffusion mainly occurs in the macropores of the adsorbent, where the molecules collide with each other and diffuse. However, in the desorption step, the mean free path of the easily adsorbed component increases under reduced pressure, and collisions between the molecules and the walls of the macropores frequently occur in the macropores of the adsorbent, in addition to the movement of molecules by molecular diffusion. Therefore, the diffusion resistance in the adsorbent becomes larger than in the adsorption step. Therefore, when the average pore diameter of the macropores is less than the mean free path of the easily adsorbable component when desorbing the easily adsorbable component, or the pore volume having a pore diameter equal to or more than the mean free path of the easily adsorbable component is If less than 70% of the total macropore volume,
The diffusion resistance of the easily adsorbed component in the macropores is large, and the performance of the adsorbent for gas separation cannot be sufficiently obtained.

The gas separation adsorbent has a total macropore volume of 0.25 cc / g or more and a pore surface area of 20 m ² / g.
g or more. Usually, the macropores of the adsorbent for gas separation are mostly composed of pores having a pore diameter of 1000 mm or more. Tends to be weak in pressure resistance. By appropriately providing pores having a relatively small diameter (for example, 1000 ° or less) between relatively large pores, it is possible to obtain an adsorbent having excellent strength properties without reducing the total volume of macropores. it can. Further, the pores having such a relatively small diameter have a small mean free path of the easily adsorbed component in the adsorption step at a high pressure, and thus serve as a gas passage to reduce the diffusion resistance of the easily adsorbed component during adsorption.

The macropores of the adsorbent for gas separation according to the present invention are pores having a pore diameter in the range of 60 ° to 200 μm as measured by a mercury intrusion method in a pressure range of 1 to 30,000 psi. From the relationship between the pore diameter and the pore volume (pore diameter distribution curve) obtained by the mercury intrusion method, the average pore diameter of the macropores becomes 50% of the total pore volume. It can be determined as the diameter (median diameter) or the diameter (mode diameter) at which the gradient of the pore diameter distribution curve is maximum.

The mean free path of the easily adsorbed component is the average distance that the molecules of the easily adsorbed component move during subsequent collisions. This mean free path is described in 312 of "Alberty Physical Chemistry (Revised 4th Edition)" (Science & Technology Publisher; Alberti).
With reference to pages 314 to 314, the pressure can be calculated by the pressure and temperature when the easily adsorbable component is desorbed from the adsorbent in the PSA method.

The mother zeolite of the adsorbent for gas separation according to the present invention is a crystalline low silica faujasite type zeolite having a molar ratio of SiO ₂ / Al ₂ O ₃ of 1.9 to 2.1 (hereinafter LSX zeolite). Call). The SiO ₂ / Al ₂ O ₃ molar ratio of LSX zeolite is theoretically 2.0, but considering the measurement error in chemical composition analysis, etc.
It is clear that LSX zeolites having a composition of 1.9 to 2.1 fall within the scope of the present invention. Various methods have been disclosed as methods for synthesizing LSX zeolite having a SiO ₂ / Al ₂ O ₃ molar ratio of 1.9 to 2.1, for example, a method described in Japanese Patent Publication No. 5-25527. Can be synthesized.

When LSX zeolite is used as the adsorbent for gas separation, the higher the crystal purity of LSX zeolite, the better the separation efficiency, and the crystal purity of LSX zeolite is 9%.
0% or more is preferable. The crystal purity of LSX zeolite is measured by powder X-ray method, gas adsorption amount measurement, moisture adsorption amount measurement,
It can be performed by NMR measurement or the like.

The fibrous binder used in the adsorbent for gas separation of the present invention includes sepiolite-type clay and attapulgite-type clay, and exists as a binder between the LSX zeolite particles in the adsorbent. Needle-like crystals having a fibrous form to form the macropores of the present invention are preferred. These clays may be used alone or as a mixture of two or more.

When a plate-shaped binder is used, the shape of the binder may inhibit the diffusion of the easily adsorbed component.
In addition, dehydration does not occur promptly during firing performed after molding, and there is a possibility that crystals of LSX zeolite may be broken.

The shape of the adsorbent for gas separation of the present invention is preferably bead-shaped, and is not limited as long as it has the characteristics of the adsorbent for gas separation of the present invention, such as spherical and elliptical shapes. . In consideration of the size of the device to be filled, the pressure loss of the packed bed, or the diffusion resistance inside the compact, the size of the adsorbent for gas separation should be 0.5 to fully exhibit the expected performance. The diameter is preferably about 5 mm.

LSX in the adsorbent for gas separation of the present invention
The composition ratio of the zeolite and the binder is preferably 5 to 30 parts by weight of the LSX zeolite in consideration of the macropore structure and the strength properties of the molded product.

The water content of the adsorbent for gas separation is preferably as small as possible, and an adsorbent having a water content of 0.8% by weight or less, more preferably 0.5% by weight or less has satisfactory adsorption performance and is preferably used. Used.

Next, a method for producing the adsorbent for gas separation of the present invention will be described.

The production method includes the following: a crystalline low-silica faujasite type zeolite having a SiO ₂ / Al ₂ O ₃ molar ratio of zeolite crystal of 1.9 or more and 2.1 or less; Water is added to 5 to 30 parts by weight of a binder with respect to 100 parts by weight of the site zeolite, and the mixture is kneaded and kneaded so as to have a bulk density of 0.8 to 1.0 kg / l. , Ion exchange,
Activate.

The method for producing the adsorbent for gas separation of the present invention comprises:
Adding and kneading and kneading the synthesized LSX zeolite powder with a binder and water, forming a kneaded and kneaded product, drying and firing the compact, and ion-exchanging the calcined compact. And a step of firing and activating, and will be described in order below.

<Kneading / Kneading Step> The synthetic LSX zeolite powder used in the adsorbent for gas separation of the present invention was synthesized by, for example, the method described in Japanese Patent Publication No. 5-25527 (Na, K). Type LSX zeolite as starting material.

This synthetic LSX zeolite powder and the binder are kneaded and mixed so that they are all uniform while adjusting the water content, and then kneaded sufficiently so that the bulk density becomes 0.8 to 1.0 kg / l. . At this time, the bulk density of the kneaded product is 0.
If it is less than 8 kg / liter, the consolidation is not sufficient, and air bubbles may be present between the mixed particles and the granulation property may be reduced. When the bulk density of the kneaded material is more than 1.0 kg / liter and is excessively compacted, the macropores of the adsorbent may be crushed.

The amount of the binder to be added is such that (Na, K) type LSX is used in order to form desired macropores, maintain a high adsorption capacity, and further increase the physical strength of the adsorbent. The range is preferably 5 to 30 parts by weight based on 100 parts by weight of zeolite. When the amount of the binder is less than 5 parts by weight, the ratio of LSX zeolite increases, which is advantageous for the adsorption of easily adsorbed components. However, the particle strength of the adsorbent becomes weak, and crushing and pulverization may occur in the packed bed. There is. If the amount of the binder is more than 30 parts by weight, the particle strength is increased, but the ratio of LSX zeolite decreases, and the adsorption capacity of easily adsorbable components decreases when gas is separated.

Kneading LSX zeolite powder and binder
The amount of water added at the time of kneading depends on the LSX zeolite powder as the raw material, the properties of the binder, and the ratio of these, but the final amount added is L
The range is preferably from 60 to 65 parts by weight based on 100 parts by weight of the SX zeolite powder.

As an additive other than water, an additive such as carboxymethyl cellulose or polyvinyl alcohol may be added.

<Molding Step> In this way, a mixture having a bulk density of 0.8 to 1.0 kg / liter by kneading and kneading is formed. The shaping is preferably carried out by blade stirring type granulation. This is because, compared to normal rolling granulation, the blade is stirred to give a strong shearing force, the added binder is uniformly dispersed, and the LSX zeolite is formed. Macropores can be formed by adhering to the particles and existing between the zeolite particles. The shape of the molded article is not particularly limited as long as it has the characteristics of the adsorbent for gas separation of the present invention, and may be spherical, elliptical, or the like, for example, 0.5 to 5 mm. A bead-shaped molded article having a size can be obtained. Furthermore, when physical strength, especially wear resistance, is required in the use as an adsorbent, it is desirable to have a bead shape having a high sphericity, and a molded spherical article is formed by a known method, for example, using a marmellaizer molding machine. The particles may be sized to smooth the surface of the molded body.

A pellet-shaped molded product is generally formed by an extrusion molding method, and has a surface in which macropores are difficult to control as compared with a bead-shaped molding. However, carboxymethylcellulose and polyvinyl which are conventionally known as a forming aid are used. By using alcohol or the like, it is possible to obtain the desired macropore structure, and it can be used as an adsorbent for gas separation.

The diameter of the beads to be formed and sized can be varied depending on the application, and the size may be uniform by classification using a sieve or the like.

<Firing Step> The formed body thus formed is dried and fired, and the added binder is sintered. Drying and baking can be performed by a usual method, for example, a hot air dryer, a muffle furnace, a rotary kiln, a tubular furnace, or the like can be used. The firing temperature may be any temperature at which the binder sinters and the zeolite crystals are not destroyed because the adsorbent can keep its shape.
Usually, it is carried out in the range of 400 to 700 ° C.

Further, the fired molded body can be cooled and humidified so that the water content becomes about 20 to 30%.
Although the humidification operation is not an essential condition, it is effective in preventing breakage such as cracking of the molded body due to rapid heat generation due to moisture adsorption in contact with the ion exchange liquid in the next step of ion exchange, Further, it is an effective means to expel the adsorbed gas such as nitrogen from the inside of the molded body and to efficiently diffuse the ion exchange liquid.

<Ion Exchange Step> The compact formed and fired by the above steps is brought into contact with an ion exchange liquid containing a cation such as lithium, potassium, calcium, strontium, barium or the like to perform ion exchange. The type of cation can be selected according to the gas to be adsorbed. For example, when air in nitrogen is adsorbed to perform air separation, lithium cation is preferably used. The compound used for ion exchange is not particularly limited as long as it can be easily provided as an aqueous solution. For example, chloride, nitrate, sulfate,
Carbonates and the like are preferably used.

As a method of ion exchange, a batch contact method or a column flow method is usually used. The batch contact method is suitable for uniformly ion-exchanging the whole, and it is possible to increase the ratio of contacting exchange ions for efficient ion exchange and to reduce the amount of ion exchange liquid by the column flow method. It is preferable to adjust the speed. In particular, when ion exchange is difficult as in the case of ion exchange of lithium cation, a column flow method is preferably used.

The temperature at which the ion exchange is carried out is preferably carried out at a temperature as high as possible in order to increase the ion exchange rate and improve the efficiency of the ion exchange.
It is carried out in the range of 〜100 ° C.

The concentration of the ion exchange liquid used is usually set at a concentration in the range of about 1 to 4N in consideration of the ion exchange rate. The ion exchange liquid is LSX at the time of ion exchange.
It is preferably alkaline to prevent the zeolite crystals from being destroyed, and usually the pH (hydrogen ion concentration) is adjusted to 9 to 12 by adding a hydroxide or the like.

After the ion exchange as described above, the molded body is taken out of the ion exchange liquid, washed with water or hot water, and usually dried at a temperature of about 30 to 100 ° C.

<Activation Step> The target adsorbent for air separation can be obtained by removing water and activating the molded body subjected to ion exchange as described above. The purpose of the activation is to remove the moisture in the molded body, and the removal of the moisture is performed under vacuum or by firing, and usually, the removal of the moisture by firing is preferably performed. As the activation condition, any condition can be used as long as moisture is removed from the molded body. In the case of activating by calcination, it is preferable to remove water as quickly as possible at a temperature as low as possible in consideration of the heat resistance of the LSX zeolite, which is usually achieved by calcination at a temperature condition of 600 ° C. or lower, for example, at 500 ° C. for about 1 hour. it can.

The adsorbent for gas separation obtained by the above steps is used for adsorption separation in which the easily adsorbable components in the gas mixture are adsorbed to separate and concentrate, for example, the oxygen adsorbed by selectively adsorbing nitrogen in the air. It can be used for recovering gas. In the case of concentrating and recovering oxygen in air by the PSA method, an adsorption step of contacting air with a packed bed of an adsorbent to selectively adsorb nitrogen and recover concentrated oxygen from an outlet of the packed bed; It is operated by a series of steps consisting of a regeneration step of interrupting the contact of the packed bed and depressurizing the inside of the packed bed to desorb and exhaust the adsorbed nitrogen, and a pressurizing step of pressurizing the packed bed with the concentrated oxygen obtained in the adsorption step. You. The number of adsorption towers constituting the PSA device for air separation is plural, and usually 2
A tower or three towers. The raw air is supplied from a blower or a compressor, but the water in the air impedes the adsorption of nitrogen, so it is necessary to remove the water before introducing it into the packed bed. The dehumidification of the raw material air is usually performed to a dew point of −50 ° C. or less. The temperature of the raw material air is closely related to the performance of the adsorbent, and may be heated or cooled so that the performance of the adsorbent can be sufficiently obtained.
It is a temperature of about ° C.

The higher the adsorption pressure in the adsorption step, the higher the nitrogen adsorption amount. Considering the load on the blower or compressor that supplies the raw air, the adsorption pressure may be in the range of 760 Torr to 1520 Torr.

It is preferable that the regeneration pressure in the regeneration step is lower because more nitrogen can be desorbed. Considering the load on the vacuum pump, the regeneration pressure is 100T
It may be in the range of not less than orr and not more than 400 Torr.

In the pressure recovery step, since the concentrated oxygen gas obtained in the adsorption step is used, when the return pressure is high, the amount of the concentrated oxygen gas extracted as the product gas decreases. Further, if the process proceeds to the adsorption step in a state where the return pressure is low, since the raw air is pressurized, nitrogen may not be adsorbed by the adsorbent and break through to the outlet of the packed bed. Also, in order to prevent nitrogen in the raw material air from breaking through to the packed bed outlet, the concentrated oxygen is returned to the packed bed in the first 1 to 5 seconds after the adsorption step is started so as to be in countercurrent with the raw material air. The pressure can be restored. The return pressure may be in a range from 400 Torr to 800 Torr.

In the adsorbent for gas separation of the present invention, the average pore diameter of the macropores is greater than or equal to the mean free path of the easily adsorbable component when the easily adsorbable component is desorbed, and is greater than or equal to the mean free path of the easily adsorbable component. Since the pore volume having a pore diameter of 70% or more of the total macropore volume is large, the diffusion rate of the easily adsorbable component at the time of desorption in the macropores under reduced pressure is particularly large, and the adsorbent for gas separation is large. Usage rate is high. The point that the physical strength properties are further excellent is that macropores are not formed only by pores having relatively large pore diameters, but pores having moderately small pore diameters are provided. It is thought to be due to

In particular, the adsorbent for gas separation of the present invention is PSA
It is more effective in air separation by the method. Therefore, when air separation is performed by the PSA method, the amount of concentrated oxygen gas taken out and the recovery rate are high, and it is possible to reduce the power consumption when the PSA device is operated.

[0051]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, each evaluation was implemented by the method shown below.

(1) Average pore diameter, pore volume and pore surface area of macropores Using an mercury intrusion porosimeter (manufactured by Micromeritics Co., model: Pore Sizer 9310), the activated adsorbent was used in an amount of 1 to 30. 2,000 psi pressure range (60Å
(Pore diameter in the range of 200 μm). From the relationship between the pore diameter and the pore volume (pore diameter distribution curve) obtained by the measurement, the average pore diameter of the adsorbent is 50% of the total pore volume.
%, Or the diameter (mode diameter) when the gradient of the pore diameter distribution curve is the maximum, and the medium diameter is adopted here.

(2) Amount of Nitrogen Adsorption Examples 1 to 6 and Comparative Examples 1 to 6 were measured by a gravimetric method using an electronic balance (Kahn 2000 type).
The pretreatment is performed at 350 ° C. for 2 hours under a vacuum of 10 ⁻³ Torr or less.
Activation was performed under the conditions. The adsorption temperature was kept at 0 ° C. and 25 ° C., and after introducing nitrogen gas, the weight after reaching a sufficient equilibrium was measured to calculate the amount of adsorption (unit: Ncc / g). The nitrogen adsorption amount in Examples and Comparative Examples shown below was 70
The values measured at 0 Torr are shown.

The measurements of Examples 7 to 9 and Comparative Example 7 were carried out by a volume method using Bell Soap 28SA (Nippon Bell Co., Ltd.). The pretreatment was performed under a vacuum of 10 ⁻³ Torr or less at room temperature (about 25 ° C.) for 2 hours. The adsorption temperature was kept at 25 ° C., and the amount of adsorption was measured up to about 800 Torr (unit: Ncc / g). Note that the nitrogen adsorption amounts in Examples and Comparative Examples are measured values at 700 Torr.

(3) Air Separation Test by PSA Method An air separation test was performed using the air separation performance test apparatus shown in FIG. 1 according to the following procedure.

The adsorption towers (13) and (14) are filled with about 2 L of an adsorbent for air separation. At the time of the adsorption step, the adsorption tower (12) dehumidifies the air compressed by the compressor (1) with the dehydration tower (2).
The pressure was reduced to kg / cm ² G, and solenoid valves (5) and (7)
Is opened to circulate through the adsorption tower (air temperature is 25
° C). The obtained concentrated oxygen gas was stored in a product tank (17), and the amount of the concentrated oxygen gas taken out was adjusted by a mass flow meter (18). The pressure at the end of the adsorption step was kept constant at 1.4 atm. When the adsorption tower (13) is in the regeneration step, the solenoid valves (5) and (7) are closed, and the solenoid valve (6)
Was opened, and the pressure inside the adsorption tower was reduced by a vacuum pump (20). The ultimate pressure at the end of the regeneration step was kept constant at 250 Torr. During the pressure recovery step, the adsorption tower (13) closes the solenoid valve (6) and opens the solenoid valve (8) to open the product tank (1).
7) The pressure inside the adsorption tower is restored with the concentrated oxygen gas. The pressure at the end of the pressure recovery step was kept constant at 500 Torr. The pressure was measured with a pressure gauge (15) (for the adsorption tower (14), a pressure gauge (16) was used). Subsequently, the adsorption tower (13) is subjected to the adsorption step, and these steps are sequentially repeated. The time of each step was 1 minute for the adsorption step and 30 seconds for the regeneration step and the pressure recovery step. The operation of the solenoid valve was controlled by a sequencer.

The adsorption tower (14) is also subjected to the same process. However, in order to continuously extract the concentrated oxygen gas, while the adsorption tower (13) is in the adsorption step, the adsorption tower (14) is subjected to the regeneration step and the regeneration step. The pressure recovery step is performed, and the adsorption tower (14) performs the adsorption step during the regeneration step and the pressure recovery step of the adsorption tower (13).

The concentration of the concentrated oxygen gas was measured with an oxygen concentration meter (19) after the value became steady,
From the value of 1), an accurate flow rate of the concentrated oxygen gas was measured (hereinafter, referred to as an oxygen amount). Also, a vacuum pump (2
The flow rate of the exhaust gas exhausted by 0) was measured from the value of the integrating flow meter (22) (hereinafter, referred to as an exhaust gas amount). In addition, the measurement of each gas amount was performed at 25 degreeC.

The air separation performance of the adsorbent was represented by the ratio of recovering 93% oxygen concentration and 93% concentrated oxygen gas from the raw material air (hereinafter referred to as the recovery ratio). The air separation test was performed at 0 ° C. and 25 ° C. in the adsorption tower.

The oxygen amount is obtained by converting the value measured by an integrating flow meter into a standard state and expressing the flow rate per 1 kg of the adsorbent (anhydrous state) per hour, in units of NL / (kg · hr). The recovery was calculated by the following equation.

Recovery rate (%) = {(oxygen content) × 0.93} /
{(Supply air amount) × 0.209} × 100 supply air amount = (oxygen amount) + (exhaust gas amount) (4) Mean free path of nitrogen when desorbing nitrogen The mean free path of nitrogen (λ) is as described above. It was calculated from the temperature (T) of the adsorption tower and the ultimate pressure (P) at the end of the regeneration step, which are the conditions of the air separation test, by the following formula. When air separation is performed by the PSA method, the temperature of the adsorbent increases due to heat generation in the adsorption step, and the temperature of the adsorbent decreases and fluctuates due to heat absorption in the desorption step. For this reason, the temperature at which the mean free path of nitrogen is calculated can be calculated using the actual temperature of the adsorbent, the temperature of the adsorption tower (ambient environment), or the temperature of the introduced gas. Was.

Λ = κT / ｛(√2) πPσ ² ｝ σ: molecular diameter of nitrogen molecule 3.681 × 10 ⁻¹⁰ (m) κ: Boltzmann constant 1.3807 × 10 ⁻²³ (J / K) The mean free path is 2 at a pressure of 250 Torr.
It becomes 2052 (２０５) at 5 ° C and 1880 (Å) at 0 ° C.

(5) Bulk density According to the method using an apparent density measuring device of JIS K-3362, the kneaded mixture was placed in a Vml polyethylene cup (W1), and a linear spatula was formed at the peak. After rubbing off, the weight (W2) of the cup containing the mixture was read to the nearest 0.1 g, and the bulk density was calculated by the following equation.

Bulk density (kg / liter) = (W2-W
1) / V (6) Moisture content According to the test method by coulometric titration of JIS K-0068, a Karl Fischer moisture meter (manufactured by Mitsubishi Chemical Corporation, moisture meter: CA-06 type, moisture vaporizer: VA-21 type) ). The electric furnace of the moisture vaporizer was set at 400 ° C,
Approximately 400 to 500 mg of the activated sample was quickly weighed and put into a sample boat in a moisture vaporizer, and dried nitrogen 30
Water was vaporized under a flow of 0 ml / min. The water content was calculated by the following equation based on the sample amount (S; unit is g) and the water amount (G; unit is μg) determined from coulometric titration.

Water content (% by weight) = G / (S × 1)
0 ⁶ ) × 100 Example 1 Synthesis of LSX zeolite was carried out by a conventionally known method. An aqueous solution of sodium aluminate (Na ₂ O = 2) is placed in a 20-liter stainless steel reaction vessel.
0.088% by weight, Al ₂ O ₃ = 22.5% by weight)
g, water 7923 g, sodium hydroxide (purity 99%) and reagent grade potassium hydroxide (purity 85%) 1845 g
And cooled while stirring at 60 rpm (solution a: ~
5 ° C). An aqueous sodium silicate solution (Na ₂ O = 3.8% by weight, SiO ₂ =
(12.6% by weight), 7150 g and water (1176 g) were added and cooled (liquid b: ℃ 10 ° C.). While stirring the liquid a, the liquid b was introduced over about 5 minutes. The solution after the addition was transparent. After stirring was continued for about 20 minutes after the completion of the charging, the temperature of the water bath was raised to 36 ° C. At the same time when the solution became cloudy, stirring was stopped, the stirring blade was taken out, and aging was performed at 36 ° C. for 48 hours.

Thereafter, the temperature of the water bath was raised to 70 ° C., and crystallization was performed for 20 hours. The obtained crystals were filtered, sufficiently washed with pure water, and then dried at 80 ° C. overnight.
The structure of the obtained crystal powder was a single phase of faujasite as a result of X-ray diffraction, and its purity was 98% or more. As a result of composition analysis by ICP emission analysis, 0.72 Na ₂
O · 0.28K is a _{2 O · Al 2 O 3 ·} 2.0SiO 2,
It was confirmed to be LSX zeolite.

20 parts by weight of attapulgite-type clay were mixed and kneaded with 100 parts by weight of this LSX zeolite powder using a mix maller mixer (manufactured by Shinto Kogyo Co., Ltd., model MSG-05S), and finally LSX was added while appropriately adding water. The mixture was adjusted by adding 65 parts by weight of water to 100 parts by weight of the zeolite powder, and then kneaded sufficiently. The bulk density of the obtained kneaded product was 0.85 kg / liter.

The kneaded product was stirred and granulated into beads having a diameter of 1.2 to 2.0 mm using a blade stirring type granulator Henschel mixer (manufactured by Mitsui Mining Co., Ltd., model: FM / I-750).
Malmerizer molding machine (Fuji Paudal, model: Q-
1000) and dried at 100 ° C. overnight. Then, using a tubular furnace (manufactured by Advantech Co., Ltd.) and sintering the attapulgite-type clay at 600 ° C. for 2 hours under air flow, and cooling in the air, the water content is reduced to about 25%. Humidified.

This compact was packed in a column of 70 mmφ × 700 mm (length), and an aqueous solution prepared by adjusting lithium chloride to a concentration of 1 mol / liter was passed at 80 ° C. to exchange lithium ions. Next, the column was sufficiently washed with pure water while being packed, and then taken out of the column and cooled to 40 ° C.
For 16 hours.

Thereafter, it was activated in a horizontal tubular furnace (manufactured by Advantech Co., Ltd.) at 500 ° C. for 1 hour under air flow, and packaged without cooling. The average pore diameter, pore volume, and pore surface area of the macropores of the obtained adsorbent for gas separation were measured. Further, the nitrogen adsorption amount and the air separation performance were measured at the adsorption temperature of 25 ° C. by the methods described above. The water content of the adsorbent for gas separation was 0.1% by weight or less. Table 1 shows the results.

Example 2 The same operation as in Example 1 was carried out except that the bulk density of the kneaded product was 0.90 kg / liter. Table 1 shows the measurement results of the obtained adsorbent for gas separation.

Example 3 The same operation as in Example 1 was performed, except that sepiolite-type clay was used as a binder. Table 1 shows the measurement results of the obtained adsorbent for gas separation.

Comparative Example 1 The bulk density after kneading and mixing was 1.8 kg / L, and a marmellaizer molding machine (manufactured by Fuji Paudal, model:
Q-1000), except that molding was performed only. Table 1 shows the measurement results of the obtained adsorbent for gas separation.

Comparative Example 2 The bulk density after kneading and mixing was 1.2 kg / l, and a marmellaizer molding machine (manufactured by Fuji Paudal Co., model:
Q-1000), except that molding was performed only. Table 1 shows the measurement results of the obtained adsorbent for gas separation.

Comparative Example 3 The same operation as in Example 1 was performed except that the bulk density after kneading and mixing was 1.2 kg / liter. Table 1 shows the measurement results of the obtained adsorbent for gas separation.

[0076]

[Table 1]

Examples 4 to 6 Using the same adsorbent for gas separation used in Examples 1, 2 and 3, the nitrogen adsorption amount and gas separation performance were measured at an adsorption temperature of 0 ° C. Table 2 shows the measurement results of the obtained adsorbent for gas separation.

Comparative Examples 4 to 6 Using the same adsorbent for gas separation used in Comparative Examples 1 to 3, the nitrogen adsorption amount and air separation performance were measured at an adsorption temperature of 0 ° C. Table 2 shows the measurement results of the obtained adsorbent for gas separation.

[0079]

[Table 2]

Example 7 The same procedure as in Example 1 was performed until the adsorbent for gas separation was activated. Before packaging, the adsorbent was taken out of the tube furnace, cooled to 400 ° C., sealed in a glass bottle, packaged, and allowed to cool to room temperature. Evaluate the water content and nitrogen adsorption of the gas separation adsorbent thus prepared,
Table 3 shows the measurement results.

Example 8 The same operation as in Example 7 was performed except that the cooling before packaging was 350 ° C. Table 3 shows the measurement results.

Example 9 The same operation as in Example 7 was carried out except that the cooling before packaging was performed at 300 ° C. Table 3 shows the measurement results.

Comparative Example 7 The same operation as in Example 7 was carried out except that the cooling before packaging was performed at 200 ° C. Table 3 shows the measurement results.

[0084]

[Table 3]

The adsorbents for gas separation shown in the above Examples 1 to 6 have an average macropore diameter of macropores larger than the average free path of nitrogen at 250 Torr for desorbing nitrogen in air separation by PSA method. The pore volume having a pore diameter not less than the mean free path occupies 70% or more of the whole, the diffusion coefficient in the pores under the condition of 250 Torr is large, and the air separation performance is excellent.

The adsorbent for gas separation of Comparative Example 1 or 4 was
The average pore diameter of the macropores is smaller than the average free path of nitrogen at 250 Torr for desorbing nitrogen in air separation by the PSA method, and the pore volume having a pore diameter equal to or larger than the average free path is the whole. And the diffusion coefficient in the pores is small. Therefore, the equilibrium adsorption amount of nitrogen is equal to that of the adsorbent of the example, but the air separation performance is lower than that of the example. In the adsorbents of Comparative Examples 2, 3 or 5, and 6, the average pore diameter is larger than the mean free path at 250 Torr, but the ratio of the pore volume equal to or larger than the mean free path is 70%.
Less, the air separation performance is lower than the adsorbents of the examples.

When Examples 7 to 9 and Comparative Example 7 are compared,
It can be seen that the gas separation adsorbent of the example having a water content of 0.8% by weight or less has a higher nitrogen adsorption amount and is preferable as the gas separation adsorbent.

[0088]

As described in detail above, in the adsorbent for gas separation of the present invention, the average pore diameter of the macropores is longer than the mean free path of the easily adsorbable component when the easily adsorbable component is desorbed.
Since the pore volume having a pore diameter not less than the mean free path of the easily adsorbed component is 70% or more of the total macropore volume, the diffusion of the easily adsorbed component during desorption in the macropores under reduced pressure High speed and high adsorbent utilization. In addition, it has excellent strength properties by appropriately providing pores having a relatively small diameter. In particular, the gas separation adsorbent of the present invention is exchanged with lithium cations, and is more effective when air separation is performed by the PSA method. Therefore, when air separation is performed by the PSA method, the amount of concentrated oxygen gas taken out and the recovery rate are high, and it is possible to reduce the power consumption when the PSA device is operated. Further, according to the production method of the present invention, an adsorbent for gas separation can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram of an air separation performance test apparatus.

[Explanation of symbols]

 1: Compressor 2: Dehydration tower 3: Pressure reducing valve 4: Dew point meter 5-12: Solenoid valve 13, 14: Adsorption tower 15, 16: Pressure gauge 17: Product tank 18: Mass flow meter 19: Oxygen concentration meter 20: Vacuum pump 21, 22: integrating flow meter

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-337365 (JP, A) JP-A-9-308810 (JP, A) JP-A-5-163015 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B01J 20/18 B01D 53/04

Claims (18)

(57) [Claims] 1. An adsorbent for gas separation comprising a crystalline low-silica faujasite-type zeolite having a SiO ₂ / Al ₂ O ₃ molar ratio of 1.9 or more and 2.1 or less and a binder, an average of macropores The diameter is greater than or equal to the mean free path of the easily adsorbable component when the easily adsorbable component is desorbed from the adsorbent, and the total volume of the macropores having a diameter equal to or greater than the mean free path of the easily adsorbable component is equal to the total macropore. Characterized in that it accounts for at least 70% of the total volume of the adsorbent. 2. The adsorbent for gas separation according to claim 1, wherein the total volume of all macropores is 0.25 cc / g or more, and the pore surface area is 20 m ² / g or more. Adsorbent for gas separation. 3. The adsorbent for gas separation according to claim 1, wherein the purity of the crystalline low silica faujasite type zeolite is 90% or more. 4. The method according to claim 1, wherein the binder is a sepiolite type clay and / or an attapulgite type clay.
The adsorbent for gas separation according to any one of claims 1 to 3. 5. The adsorbent for gas separation according to claim 1, wherein the adsorbent for gas separation is in the form of beads. 6. The adsorbent for gas separation according to claim 1, wherein the low silica faujasite type zeolite has been ion-exchanged with lithium cations. 7. The adsorbent for gas separation according to claim 1, wherein the water content of the adsorbent for gas separation is 0.8% by weight or less. 8. A crystalline low silica faujasite zeolite having a zeolite crystal having a SiO ₂ / Al ₂ O ₃ molar ratio of 1.9 or more and 2.1 or less, and 100 parts by weight of said low silica faujasite zeolite on an anhydrous basis. 5 to 30 parts by weight of a binder and water are added to make the bulk density 0.8 to 1.0 k
g / liter and then kneaded and kneaded, then molded,
The method for producing an adsorbent for gas separation according to any one of claims 1 to 7, wherein the method is calcined, ion-exchanged, and activated. 9. The method according to claim 8, wherein the binder is a sepiolite type clay and / or an attapulgite type clay.
3. The method for producing an adsorbent for gas separation according to item 1. 10. The method for producing an adsorbent for gas separation according to claim 8, wherein the adsorbent is formed into a bead shape by blade stirring type granulation. 11. The method for producing an adsorbent for gas separation according to claim 8, wherein the calcined compact is subjected to ion exchange with a solution containing lithium cations. 12. A gas mixture is brought into contact with a packed bed of the adsorbent for gas separation according to any one of claims 1 to 7,
A gas separation method comprising selectively adsorbing at least one constituent gas among constituent gases in a gas. 13. The gas separation method according to claim 12, wherein the gas is air, and nitrogen gas is selectively adsorbed,
A method for separating nitrogen gas and oxygen gas, comprising recovering oxygen gas. 14. The nitrogen gas-oxygen gas separation method according to claim 13, wherein nitrogen in air is selectively adsorbed by a pressure vibration adsorption method. 15. The nitrogen gas-oxygen gas separation method according to claim 14, wherein air is brought into contact with the packed bed to selectively adsorb nitrogen and recover concentrated oxygen from an outlet of the packed bed. It is operated by a regeneration step of interrupting the contact between air and the packed bed and depressurizing the packed bed to desorb and adsorb the adsorbed nitrogen, and a depressurizing step of pressurizing the packed bed with the concentrated oxygen obtained in the adsorption step. A method for separating nitrogen gas and oxygen gas. 16. The method according to claim 15, wherein the adsorption pressure in the adsorption step is 760 Torr.
A nitrogen gas-oxygen gas separation method characterized by being in the range of not less than r and not more than 1520 Torr. 17. The nitrogen gas according to claim 15,
In the oxygen gas separation method, the regeneration pressure in the regeneration step is 10
A nitrogen gas-oxygen gas separation method characterized by being in a range of 0 Torr or more and 400 Torr or less. 18. The nitrogen gas-oxygen gas separation method according to claim 15, wherein the return pressure of the pressure recovery step is in a range of 400 Torr to 800 Torr. An oxygen gas separation method.