JPH11246215A - Low silica x-zeolite bead compact and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a low silica X-zeolite bead compact having a high adsorption capacity because of its large pore volume and large pore surface area, also having superior adsorption performance such as a high adsorption rate and excellent in strength and physical properties typified by pressure resistance. SOLUTION: This low silica X-zeolite bead compact comprises low silica X-zeolite powder having an SiO2 to Al2 O3 molar ratio of 1.9-2.1 and a clay binder having a fibrous one-dimensional structure and has >=0.25 cc/g pore volume and >=20 m<2> /g pore surface area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to SiO ₂ / Al ₂ O ₃
The present invention relates to a low-silica X-type zeolite (hereinafter, referred to as “LSX-type zeolite”) bead having a molar ratio of 1.9 to 2.1 and a method for producing the same. More specifically, it is widely used as an adsorptive separation agent, and ion-exchanges sodium and potassium ions in LSX-type zeolite into various ions according to the purpose by an ion exchange method, for example, containing nitrogen and oxygen as main components. The present invention relates to a low-silica X-type zeolite bead molded article useful in the field of adsorptive separation such as selectively adsorbing nitrogen from a mixed gas by an adsorption method and separating and concentrating oxygen, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a zeolite molded body has been prepared by using a zeolite powder, a clay-based binder, and water and, depending on the purpose, adding an organic-based molding aid to form a columnar (pellet).
It is formed into a spherical shape (beads), a granular shape, a fine granular shape, or the like.
Further, as a more specific example, there is one using silica sol, alumina sol or the like as a binder.

[0003] In the case of an adsorbent produced using a binder having a different size from zeolite crystals, the key to exhibiting excellent adsorption performance is how to form pores in the obtained molded article. In general, the molded article is molded using a large amount of binder in order to increase the physical strength of the molded article.

[0004] However, usually used binders are extremely fine compared to zeolite crystals,
As the amount of the binder increases, the surface of the molded body is easily covered in proportion to the amount of the binder added, and the molded body is liable to be clogged up to the inside of the molded body. ) Is difficult to form, resulting in a compact having a small pore volume and a small pore surface area.

A bead-shaped compact is formed by a rolling granulation method utilizing centrifugal force. The bead-shaped compact generally has an onion shape, and almost no mesopore exists. Not. Such a problem in molding becomes more prominent when plate-like clay such as kaolin-type or bentonite-type clay is used as the binder.

As described above, when a gas is separated or concentrated using a small number of molded bodies even if there is no mesopore, the gas diffusion is difficult and the adsorption or desorption speed is reduced. It will be. For example, in a short cycle gas separation / concentration by a PSA (Pressure Swing Adsorption) method, there is a possibility that the inside of the compact is not effectively used.

[0007]

SUMMARY OF THE INVENTION The present invention overcomes the conventional problems in the above-mentioned zeolite molded article, and has an object to provide a large pore volume and a large pore surface area, and therefore a large adsorption capacity. An object of the present invention is to provide an LSX-type zeolite bead molded article which is excellent in adsorption performance such as high adsorption speed and is particularly useful as a high-performance PSA adsorbent. In addition, LS with excellent strength physical properties represented by pressure resistance
It is also an object of the present invention to provide an X-type zeolite bead molding. Further, the present invention provides a production method capable of easily obtaining such an LSX-type zeolite bead molded product.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that SiO ₂ / Al ₂
Water is added to a low silica X-type zeolite powder having an O ₃ molar ratio of 1.9 to 2.1 and a clay binder having a fibrous one-dimensional structure, and these have a bulk density of 0.8 to 1.0 kg / liter. After kneading and kneading, the mixture is formed into beads by tumbling granulation using a blade stirring method, resulting in a large pore volume and a large pore surface area, a high adsorption performance, and an LSX type having excellent strength physical properties. The inventors have found that a zeolite bead molded product can be easily obtained, and have completed the present invention.

Hereinafter, the present invention will be described in detail.

The LSX-type zeolite bead compact of the present invention comprises a low-silica X-type zeolite powder having a SiO ₂ / Al ₂ O ₃ molar ratio of 1.9 to 2.1 and a clay binder having a fibrous one-dimensional structure. Body having a pore volume of 0.2
5 cc / g or more and a pore surface area of 20 m ² / g
That is all.

Here, the LSX-type zeolite beads of the present invention have the following properties: a pore volume by a mercury intrusion method at a pressure of 30,000 psi is 0.25 cc / g or more;
Further, the pore surface area is preferably 20 m ² / g or more, and the pore volume is preferably 0.30 cc / g or more. Within this range, the adsorption rate is high, and within the pore diameter range of 60 to 2,000,000 angstroms, 30% of the pore volume of the compact is in the range.
% Or more becomes a mesopore, and can exhibit excellent adsorption performance. Generally, the performance of the zeolite adsorbent used for separation and concentration depends on how quickly the adsorbed substance diffuses in the molded body. Therefore, the pore volume is large, especially dispersing the mesopores uniformly in the molded body,
In addition, by forming the fine particles so as to increase the number as much as possible, the surface area of the pores can be increased and the diffusion rate can be improved, and the adsorbent is excellent in terms of the adsorption rate.

The shape of the LSX-type zeolite bead molded article of the present invention may be in the form of beads, and is not limited as long as it has the characteristics of the LSX-type zeolite bead molded article of the present invention, such as a sphere or an ellipse. Never. Furthermore, the size may be any size in accordance with the purpose of use, taking into account ease of molding and operability.
A compact having a diameter of about 5 mm is used.

The LSX-type zeolite powder used in the LSX-type zeolite bead compact of the present invention may be SiO 2 powder.
₂ / Al ₂ O ₃ molar ratio of X-type zeolite 1.9 to 2.1. Note that the Na / K type LSX type zeolite Si
The O ₂ / Al ₂ O ₃ molar ratio is theoretically 2.0, but 1.9 to 1.9 in consideration of the variation in measurement in chemical composition analysis.
Obviously, it will be in the range of 2.1. In addition, a synthetic product is preferable in consideration of purity.

The fibrous one-dimensional structure clay binder used in the LSX-type zeolite bead compact of the present invention includes sepiolite-type clay and attapulgite-type clay, and exists as a binder between zeolite particles in the compact. In particular, needle-like crystals are preferable in order to increase the pore surface area of the molded product. These clays may be used alone or as a mixture of two or more.

The composition ratio of the LSX-type zeolite and the clay binder in the LSX-type zeolite bead compact of the present invention is such that when the amount of the clay binder is large, the pore surface area is large and the strength is strong, and when the amount of the clay binder is small, In consideration of an increase in the pore volume, a zeolite having a ratio of about 15 to 25% by weight of the LSX zeolite is preferably used.

Next, a method for producing the molded LSX-type zeolite beads of the present invention will be described.

The production method is as follows: SiO ₂ / Al ₂ O ₃
An LSX-type zeolite powder having a molar ratio of 1.9 to 2.1;
Water is added to a fibrous one-dimensional clay binder such as sepiolite-type or attapulgite-type clay in an amount of 15 to 25 parts by weight per 100 parts by weight of the LSX-type zeolite powder on an anhydrous basis to obtain a bulk density of 0.8 to 1 After kneading and kneading so as to be 0.0 kg / liter, the mixture is formed into beads by tumbling granulation of a blade stirring type.

Here, sepiolite-type clay and attapulgite-type clay which are clay binders to be added are S
i, Al, Mg, and Fe are only slightly different in content, and are basically similar hydrous magnesium silicates having a fibrous primary structure. Have the same physical properties. Therefore,
In the following description, it is described as a clay binder without any particular limitation.

The method for producing a molded LSX zeolite bead of the present invention comprises a step of mixing and kneading a synthetic LSX zeolite powder, a clay binder and water, a step of molding the kneaded product into beads, and drying the molded article. It comprises a firing step, a step of contacting with an aqueous solution of a salt of lithium, calcium, strontium or the like for ion exchange, and a step of firing and activating the molded body depending on the application.

<Mixing / Kneading Step> The synthetic LSX-type zeolite powder used in the zeolite bead molded product of the present invention comprises:
A starting material is a Na / K type LSX zeolite synthesized from sodium aluminate, sodium silicate and potassium hydroxide.

The synthetic LSX zeolite powder and the clay binder are kneaded and mixed so as to be uniform while adjusting the water content, and then kneaded sufficiently so that the bulk density becomes 0.8 to 1.0 kg / l. You. When the bulk density of the mixture at the time of kneading and mixing is smaller than 0.8 kg / liter, the compaction is not sufficient, and pores of air bubbles exist between the particles of the mixture, so that granulation properties may be reduced.

The amount of the clay binder to be added is as follows:
In order to increase the physical strength of the molded body, maintain a higher adsorption capacity, and form a pore volume and a pore surface area,
A range of ２５25 parts by weight is preferred. When the amount exceeds 25 parts by weight, the adsorption capacity of the obtained molded body is reduced due to a relative decrease in the amount of zeolite, and when the amount is less than 15 parts by weight, the physical strength is remarkably reduced, making it difficult to withstand use as an adsorbent. Is not preferred.

The amount of water added for adjustment when mixing and kneading the zeolite powder and the clay binder depends on the properties of the raw material zeolite powder and the clay binder, and the ratio of these amounts. The amount to be added is preferably in the range of 60 to 65 parts by weight based on 100 parts by weight of the zeolite powder.

<Molding Step> The mixture having a bulk density of 0.8 to 1.0 kg / liter after sufficiently kneading is formed into beads by stirring granulation using a blade stirring method. Strong shear force is given by stirring blades compared to normal tumbling granulation, added clay binder is uniformly dispersed and adheres to zeolite particles, and pores are formed by existing between zeolite particles Will do. The shape of the molded product is not particularly limited as long as it has the features of the LSX-type zeolite bead molded product of the present invention.
It may be formed into a spherical shape, an elliptical shape, or the like.
A bead compact having a size of 4 mesh can be obtained. In addition, physical strength in use as an adsorbent,
In particular, when abrasion strength is required, it is desirable to use a bead having a high sphericity, and the formed spherical article is sized using a known method, for example, a melmerizer, to smooth the surface of the formed article. You may.

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

<Firing Step> The molded body thus formed is dried and fired, and the added clay binder is sintered. As a method for drying and firing, known methods can be used, and for example, a hot air dryer, a muffle furnace, a tubular furnace, or the like may be used. The firing may be performed at a temperature of 600 ° C. or higher, which is the sintering temperature of the clay binder, in order to stably maintain the shape of the obtained molded body, and a temperature condition of 600 to 650 ° C. is more preferable.

Further, the fired molded body can be cooled and humidified so that the water content becomes about 25%. The humidification operation is not an essential condition, but it is necessary to prevent breakage, such as cracking and peeling, of the molded body due to rapid heat generation due to moisture adsorption in contact with the ion exchange liquid during the next step of ion exchange treatment. It is an effective means to expel gas such as nitrogen adsorbed from the inside of the molded body and to make diffusion with the ion exchange liquid more efficient.

<Ion Exchange Step> The bead compact formed and fired by the above steps is brought into contact with an ion exchange liquid containing desired ions such as LI, Ca, Sr, etc. at a predetermined temperature to perform ion exchange. The compound used for exchange with each ion is not particularly limited as long as it can be easily provided as an aqueous solution, but usually, an aqueous chloride solution is preferably used.

As a method of exchange, a batch contact method, a column flow method, or the like is usually used. In order to increase the ratio of exchanged ions to be contacted for efficient ion exchange or to reduce the amount of exchange liquid, a column flow method is used. The flow rate is preferably adjusted by using the above method, and a batch contact method is suitable for uniformly ion-exchanging the whole. In particular, when the exchange is extremely difficult such as a solution containing lithium ions, a column flow method is preferably used.

The exchange temperature at the time of performing these ion exchanges is determined in consideration of the ion exchange equilibrium reaching speed.
Usually, about 60 ° C. is preferably used. However,
For example, when the exchange is very difficult such as lithium ion, the exchange efficiency can be improved by increasing the exchange temperature. After the ion exchange in this manner, the molded body is taken out of the ion exchange aqueous solution, washed sufficiently with water or warm water, and usually dried at a temperature of about 80 to 100 ° C.

<Activation Step> By sintering and activating the compact obtained as described above, an adsorptive separating agent having excellent adsorption performance can be obtained. As the firing conditions, any purpose can be used as long as the purpose is to desorb moisture in the molded body, and the molded body is thereby activated. In consideration of the heat resistance of the zeolite, it is preferable to quickly desorb water at a temperature as low as possible.
This can be achieved by firing at about 1 hour for about 1 hour.

The molded LSX-type zeolite beads obtained by the method of the present invention are capable of selectively adsorbing a mixed gas, for example, nitrogen, which is a main component in air, by an adsorption method to separate and concentrate oxygen. Useful for applications in the pharmaceutical field.

The reason why the LSX-type zeolite bead molded product of the present invention can be obtained without impairing the pore structure essential for the adsorptive separation agent is that a fibrous one-dimensional sepiolite-type clay or an attapulgite-type clay is used as a clay binder. And a point that the clay binder is uniformly dispersed by applying a strong shearing force by granulation using a blade stirring granulator. That is, it is considered that countless pores can be formed between zeolite particles by adhering fine clay particles of 1 μm or less to the zeolite surface during molding. Therefore, diffusion of the adsorbed gas and the like is hastened,
For example, PS that repeats adsorption and regeneration in a fixed short cycle
Gas separation / concentration by the method A is an excellent adsorbent which is effectively used up to the inside of the molded article.

It is considered that the further excellent pressure resistance or wear resistance is due to the fact that the uniformly mixed and kneaded clay binder is strongly sintered by firing.

However, such a presumption does not restrict the present invention at all.

[0036]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Each evaluation was carried out by the following methods: 1) Pore volume, surface area The fired and activated bead compact was placed on a mercury intrusion porosimeter (Micromeritics, Model: Poisizer)
9310) in a pressure range of 1 to 30,000 psi.

2) Pressure Resistance 25 pieces of the fired and activated bead moldings were measured with a hardness meter (manufactured by Kiya Seisakusho, Model: KHT-20).

The measurement is carried out by applying a load to the compact at a constant speed with an indenter having a diameter of 5 mm, and the weight when the compact is crushed is defined as the pressure resistance (kgf).

3) Abrasion rate The abrasion rate was calculated according to the particle strength measurement method described in JIS-K-1464 (1962 version). That is, the fired activated bead compact as a sample was allowed to stand in a desiccator at a temperature of 25 ° C. and a relative humidity of 80% for 16 hours or more until equilibrated. Then, about 70 g of the sample was 850 μm, 3
Using a sieve (Model: JIS Z-8801, manufactured by Tokyo Screen Co., Ltd., model: JIS Z-8801) with a set of 55 μm and a saucer, sieved for 3 minutes, and then sieved for 3 minutes to the above-mentioned sieve from which deposits and the like have been removed, and 50 g of a remaining sample is obtained. Is accurately weighed, 5 coins are set at the same time, and shaken for 15 minutes. The wear rate was calculated by the following equation (1) using the sample dropped on the pan as Xg.

Abrasion rate (% by weight) = (X / 50) × 100 (1) 4) Nitrogen adsorption amount It was measured using a Cahn electronic balance. Activation was performed at 350 ° C. for 2 hours at a degree of vacuum of 10 ⁻³ torr or less as pretreatment conditions. The adsorption temperature is kept at −10 ° C., and the adsorption capacity (unit:
Ncc / g) was calculated. The nitrogen adsorption amounts in Examples and Comparative Examples shown below are measured values at an equilibrium pressure of 700 torr.

5) Bulk density According to the method using an apparent density measuring device according to 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 (2).

Bulk density (kg / liter) = (W2-W1) / V (2) Example 1 Synthetic LSX zeolite powder (Si, manufactured by Tosoh Corporation)
O ₂ / Al ₂ O ₃ = 2.0) 15 parts by weight of sepiolite-type clay were mixed and kneaded with 100 parts by weight of the mixture using a mixing muller granulator (manufactured by Shinto Kogyo Co., Ltd., model: MSG-05S), and water was removed. LSX type zeolite powder 10
After adjusting by adding 65 parts by weight of water to 0 parts by weight,
Kneaded well. When the bulk density of the obtained kneaded product was measured by the above method, it was 0.85 kg / liter.

The kneaded product was stirred and granulated into beads having a diameter of 1.2 mm to 2.0 mm using a blade stirring granulator Henschel mixer (manufactured by Mitsui Mining Co., Ltd., model: FM / I-750). Riser molding machine (manufactured by Fuji Paudal, model:
Q-1000), and dried. Next, a muffle furnace (manufactured by Advantech, model: KM-60)
After sintering in a 600 ° C. atmosphere for 2 hours in a stream of air using 0) to sinter the sepiolite-type clay, it was cooled in the air and humidified so that the water content became about 25%.

This compact was packed in a column of 70 mmφ × 700 mm (length)), and lithium chloride was previously charged at 1 mol / mol.
An aqueous solution adjusted to a concentration of 1 liter was flow-contacted at 80 ° C. for lithium ion exchange, washed sufficiently with water while filling the column, and then dried at 80 ° C. for 16 hours. Thereafter, activation treatment was performed at 500 ° C. for 1 hour in a tubular furnace (manufactured by Advantech) under air flow. The pore volume, surface area, of the obtained LSX-type zeolite bead molding,
The compressive strength, wear rate, and nitrogen adsorption amount were measured by the methods described above. Table 1 shows the results.

[0045]

[Table 1]

Examples 2 to 9 Example 1 was repeated except for the types of clay and the amount of clay shown in Table 1.
An LSX-type zeolite bead molded product was prepared by the same operation as described above. Of used synthetic LSX type zeolite powder Si
The O ₂ / Al ₂ O ₃ molar ratio was all 2.0, and the bulk density of the obtained kneaded product was measured by the method described above.
It was in the range of 0.81 to 0.86 kg / liter. Table 1 shows the results of measuring the pore volume, surface area, pressure resistance, abrasion rate, and nitrogen adsorption amount of the obtained LSX-type zeolite bead compact by the above-described methods.

Comparative Examples 1 to 6 Example 1 was repeated except for the types and amounts of the clays shown in Table 2.
An LSX-type zeolite bead molded product was prepared by the same operation as described above. Of used synthetic LSX type zeolite powder Si
The O ₂ / Al ₂ O ₃ molar ratio was all 2.0, and the bulk density of the obtained kneaded product was measured by the method described above.
It was in the range of 0.84 to 0.90 kg / liter. Table 2 shows the results of measurement of the pore volume, pore surface area, and nitrogen adsorption amount of the obtained LSX-type zeolite bead molded product by the above-described methods.

[0048]

[Table 2]

Comparing the above Examples and Comparative Examples, the Examples show that the obtained LSX-type zeolite bead molded products have a higher pore volume and a higher pore surface area, and therefore have a superior nitrogen adsorption amount. I understand.

[0050]

As is clear from the above, the LS of the present invention
The X-type zeolite bead molded article has a high adsorption capacity such as an adsorption capacity and an adsorption speed due to a large pore volume and a large pore surface area, and has excellent strength physical properties. Further, according to the production method of the present invention, an LSX-type zeolite bead molded product can be easily obtained.

Claims (5)

[Claims] (1) The molar ratio of SiO ₂ / Al ₂ O ₃ is 1.9 to 2.
The molded product comprising the low silica X-type zeolite powder of No. 1 and a fibrous one-dimensional structure clay binder has a pore volume of 0.25 c.
A low silica zeolite bead molded product having a c / g or more and a pore surface area of 20 m ² / g or more. 2. The low-silica X-type zeolite bead molding according to claim 1, wherein the fibrous one-dimensional clay is a sepiolite-type clay and / or an attapulgite-type clay. 3. The SiO ₂ / Al ₂ O ₃ molar ratio is from 1.9 to 2.
1 to 15 parts by weight based on 100 parts by weight of the low silica zeolite powder on an anhydrous basis.
Water is added to a weight part of a fibrous one-dimensional clay binder and kneaded and kneaded so as to have a bulk density of 0.8 to 1.0 kg / l. 3. The method for producing a low silica X-type zeolite bead according to claim 1, wherein the molded product is formed into a sintered body, and then fired, ion-exchanged, and activated. 4. The method for producing a low silica X-type zeolite bead according to claim 3, wherein the clay having a fibrous one-dimensional structure is a sepiolite-type clay and / or an attapulgite-type clay. 5. The low silica X-form according to claim 3, wherein the calcined compact is packed in a column, and a solution containing lithium ions is passed through the column for ion exchange. A method for producing a molded zeolite bead.