JPH10101326A - Zeolite bead formed body having low wearing property and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain A-type or X-type zeolite beads having high adsorptivity and low wearing property and containing no binder which are useful for adsorption separation by preparing the beads to have a high zeolite content and large pore volume. SOLUTION: After bead formed body comprising 100 pts.wt. zeolite powder and <=25 pts.wt. kaolin clay is calcined, the bead body is brought into contact with a single soln. of NaOH (to obtain A-type zeolite) or a soln. of NaOH and sodium silicate (to obtain X-type zeolite) for hydrothermal treatment to transfer the kaolin clay to the zeolite. The obtd. zeolite bead formed body has >=95wt.% zeolite content, >=0.2cc/g pore volume and <=0.5wt.% wearing rate measured according to JIS-K1464.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called binder-less, low-wear zeolite bead molding having a low binder content and a method for producing the same. More specifically, it is widely used as an adsorptive separation agent, and ion-exchanges sodium ions into calcium ions by an ion-exchange method, for example, selectively adsorbs nitrogen by an adsorption method from a mixed gas containing nitrogen and oxygen as main components. The present invention relates to a binderless, low-abrasive A-type and X-type zeolite bead molded body useful for purposes such as adsorption separation such as separation and concentration of oxygen or adsorption and removal of water in an organic solution, and a method for producing the same. It is.

[0002]

2. Description of the Related Art Conventionally, a zeolite bead compact is formed by rolling a zeolite powder, a binder such as a clay-based binder, silica sol, and alumina sol, and water, or, depending on the purpose, a wet powder of a kneaded mixture containing a molding aid. It is formed by a granulation method. According to this method, it is easy to control the size of the beads. For example, if the obtained granules are coated with wet powder while rolling, the bead diameter becomes large, and these methods are generally widely used. There is also known an extrusion malm-forming method in which a wet powder of a kneaded mixture is extruded and the formed pellets are rolled to form beads.

[0003] The molded body thus obtained is usually 5
The binder is sintered by baking at a temperature of 50 to 650 ° C. to increase the strength. If necessary, the binder is ion-exchanged with various cations, activated, and subjected to adsorption separation.

[0004] However, a zeolite molded body formed by the tumbling granulation method can maintain a certain level of strength physical properties because it contains a large amount of a binder component. In contrast to the columnar articles, the beads which are formed by centrifugal force under their own weight have a drawback in that the abrasion resistance is particularly low.
For example, when a binder having poor sinterability such as silica sol or alumina sol is used, there is a defect that the wear resistance is remarkably poor regardless of the amount of the binder. In addition, in an adsorbent manufactured using a binder having a different size from the zeolite crystal, it is characterized that pores important in its performance are easily formed, but the added binder does not participate in adsorption separation. Therefore, the adsorption performance was not always satisfactory.

Further, in the case of an adsorbent having poor abrasion resistance, powdering occurs due to repeated filling and adsorption / desorption of the adsorption tower, for example, which causes various troubles in valves or valves, or increases pressure loss. There is a problem that the adsorptive separation ability is reduced.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the conventional problems in such a zeolite molded article,
An object of the present invention is to provide a binderless, low wear zeolite bead molded article having high adsorption performance, a large pore volume, and not impairing strength properties represented by wear resistance, and a method for producing the same.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, as a molded article of low-wearing zeolite beads, increase the zeolite content and increase the pore volume. As a result, the present inventors have found that it is possible to easily obtain a low-wear A-type or X-type zeolite bead molded body having high adsorption performance and also excellent strength properties as a bead molded body, and completed the present invention. I came to.

Hereinafter, the present invention will be described in detail.

First, the low wear zeolite bead molding of the present invention will be described.

[0010] The molded article of low-wear zeolite beads of the present invention has a zeolite content of 95% by weight or more based on the whole amount,
The pore volume is 0.2 cc / g or more. Furthermore, as shown in the examples, the low wear property is JIS-K
The wear rate calculated according to the particle strength measurement method described in -1464 is 0.5% by weight or less.

Here, when the zeolite content is less than 95% by weight of the total amount, the gas diffusion rate, that is, the adsorption / desorption rate becomes low, and the performance as an adsorbent is unfavorably deteriorated. Similarly, for the pore volume, 0.2 cc
/ G is not preferable because the adsorption capacity becomes small. Further, when the wear rate exceeds 0.5% by weight, the strength of the molded body is deteriorated, which is not preferable in practical use.

Next, the method for producing the low-wear zeolite bead compact of the present invention will be described.

As a method for producing the same, a bead compact composed of zeolite powder and 25 parts by weight or less of kaolin-type clay with respect to 100 parts by weight of zeolite powder is calcined, and then an aqueous sodium hydroxide solution or sodium hydroxide and silicic acid are used. The gist of the present invention is to convert kaolin-type clay in a molded body into zeolite by contacting with a mixed aqueous solution of sodium and performing a hydrothermal treatment.

Here, the process for producing the low-wear zeolite bead compact of the present invention in either the A-type or the X-type zeolite is the same, and a binder-less solution used for performing a binder-less treatment, In other words, the only difference is the hydrothermal treatment conditions using an aqueous sodium hydroxide solution for A-type zeolite and a mixed aqueous solution of sodium hydroxide and sodium silicate for X-type zeolite. Accordingly, the binder-less low-wear A-type zeolite bead molded product and the method for producing the same will be described in detail below, and the method for producing the low-wear X-type zeolite bead molded product will be described in detail with reference to examples.

The method for producing the low-wear zeolite bead compact of the present invention includes a step of mixing a synthetic sodium A-type zeolite powder with kaolin-type clay and water, a step of forming a mixture, and a step of drying the obtained compact. Baking, contacting with a sodium hydroxide aqueous solution at a constant temperature to perform a binderless treatment, and contacting with a calcium salt aqueous solution to exchange 67% or more of sodium ions for calcium ions, thereby obtaining a theoretical pore diameter of 5 angstroms. CaA
It comprises a step of exchanging the zeolite into a zeolite and a step of firing and activating the molded body, so that a binderless, low-wear CaA-type zeolite bead molded body can be easily produced.

Hereinafter, these steps will be described.

<Mixing Step> As the synthetic sodium A-type zeolite powder as a starting material of the molded article of low-wear zeolite beads, a known method, that is, one synthesized from sodium aluminate and sodium silicate is preferably used.

The synthetic sodium A-type zeolite powder and the kaolin-type clay to be added are kneaded and mixed so that they are all uniform while adjusting by adding water, and then sufficiently kneaded. As the amount of kaolin-type clay to be added, in order to obtain a molded body having high physical strength and further increase the binderless conversion rate as much as possible to increase the adsorption capacity, 100 parts by weight of sodium A-type zeolite powder is used. The content is preferably 25 parts by weight or less, particularly preferably in the range of 20 to 25 parts by weight. The amount of addition may be determined, for example, by
After the molded body was brought into contact with an aqueous sodium hydroxide solution at 40 ° C. for 1 hour and aged as in the method described in JP-A-7119,
By raising the temperature to 80 ° C. and contacting for 4 hours, kaolin-type clay as a binder is transferred to A-type zeolite, and a binder-less and low-wear A-type zeolite bead molded body is subjected to calcium ion exchange treatment. This is an amount suitable for obtaining a molded article having higher adsorption performance. As the kaolin-type clay, in order to stabilize the physical properties of the finally obtained molded body and increase the yield, it is preferable to use those having few impurities, and examples thereof include georgia akaolin. As the amount of water used for adjustment when mixing the zeolite powder and kaolin-type clay, the raw material zeolite powder,
Although it is not fixed depending on the properties and the ratio of the kaolin type clay, it is usually 60 to 7 parts per 100 parts by weight of the zeolite powder.
An amount in the range of 0 parts by weight is sufficient.

<Molding Step> The mixture thus kneaded sufficiently is formed by rolling granulation or the like. The shape of the molded article is not limited as long as it has the features of the low-wear zeolite bead molded article of the present invention,
The beads can be formed into a spherical shape, an elliptical spherical shape, or the like. For example, a bead compact of 6 to 14 mesh can be formed by rolling granulation. Here, as a method of molding into beads, a known method can be used, and for example, a marmalizer molding machine or the like can be exemplified. The diameter of the beads to be formed can be varied depending on the application. Further, if necessary, the obtained beads may be classified by sieving to uniform the size.

<Firing Step> After forming, drying and firing, the added kaolin-type clay is sintered, cooled, and humidified to a water content of about 25%. As a method of drying and firing,
It can be carried out by using a known method. The firing temperature is set at 6 in order to stably maintain the shape of the obtained molded body.
It is preferable to carry out under the condition of 00 to 650 ° C. Furthermore,
The humidifying operation may be carried out as needed, but in the next step of binderless treatment, rapid heat generation due to contact with the binderless liquid causes generation of impurities or cracks and peeling of the molded body. It is effective in preventing.

<Binderless treatment step> The molded body thus obtained is immersed in an aqueous sodium hydroxide solution to carry out a binderless treatment. The concentration of the aqueous sodium hydroxide solution used here is preferably in the range of 1.5 to 2 mol / l. The reason for this is that the crystallization is advanced quickly and the sodium hydroxide aqueous solution is sufficiently diffused into the inside of the molded body to complete the binderless process, thereby obtaining a molded body with a large pore volume and excellent adsorption performance. This is because the formation of impurities such as hydroxysodalite can be suppressed.

Next, after aging at a predetermined temperature for a predetermined time, the temperature is raised to crystallize, and the kaolin-type clay is transferred to the A-type zeolite. The aging condition may be a temperature of 40 ° C. or less and a time of 1 hour or more. Conditions for raising the temperature for crystallization may be such that A-type zeolite is generated. The temperature is preferably 80 ° C. or more, and the crystallization time is preferably 4 hours or more. In this way, of the kaolin-type clay added and mixed, a molded product obtained by crystallizing substantially all that can be transformed into A-type zeolite is taken out from the aqueous sodium hydroxide solution and sufficiently washed with water or warm water.

<Exchange Step> The binderless bead molded article is brought into contact with a calcium salt aqueous solution under a constant temperature condition by the above steps, and 67% or more of sodium ions are exchanged for calcium ions. The calcium compound used for exchange with sodium ions is not particularly limited as long as it can be easily provided as an aqueous solution, but usually, calcium chloride, calcium nitrate, an aqueous solution of calcium bromide and the like are preferably used, and particularly an aqueous solution of calcium chloride Is preferably used. As the exchange method, a batch contact method, a column flow method, or the like is usually used, and when performing efficient ion exchange, it is preferable to perform the flow by adjusting the flow rate by the column flow method. For this, the batch contact method is suitable. The temperature at which the ion exchange is carried out is determined in consideration of the speed at which the ion exchange equilibrium is reached, but usually about 50 ° C. is sufficient.

After the calcium ion exchange as described above, the molded body is taken out of the calcium salt aqueous solution, washed sufficiently with water or warm water, and dried usually at about 60 to 80 ° C. <Activation Step> By further firing the molded body thus obtained, an adsorptive separating agent having high adsorption performance can be obtained.
The firing conditions are to desorb water in the molded body for the purpose, and any conditions can be used as long as the firing activates the molded body and improves the adsorption performance. For example, it can be achieved by firing at 400 ° C. for about 1 hour.

As described above, there is no problem as long as the raw material powder characteristics, the production conditions and the like are appropriately selected and the molded product having the characteristics of the low wear zeolite bead molded product of the present invention can be obtained.

The low-wear zeolite beads obtained by the method of the present invention can selectively adsorb nitrogen from a mixed gas by an adsorption method to separate and concentrate oxygen, or adsorb and remove water in an organic solution. It can be used for applications such as adsorption separation agents.

The reason why the low-wear zeolite bead compact of the present invention can increase the zeolite component without impairing the pore volume essential for the adsorptive separation agent is that the molar ratio of SiO ₂ / Al ₂ O ₃ is 2 In the point that kaolin-type clay is used as a binder, a binderless liquid, that is, dissolution of kaolin-type clay in a mixed aqueous solution of sodium hydroxide and sodium silicate for an A-type zeolite, and a mixed aqueous solution of sodium hydroxide and sodium silicate for an X-type zeolite. It is considered that the next generation and growth of zeolite crystal nuclei proceed relatively uniformly from the surface to the inside of the compact. Another point of excellent abrasion resistance is that 1
Fine clay particles of μm or less strongly sinter with the mother zeolite by calcination, and in the next binderless process, all are 1-2 μm.
This is presumably because it is converted to zeolite m and no fine clay component can be present on the surface of the compact.

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

[0029]

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.

The kaolin-type clay used is Georgia Kaolin having a low impurity content.

Pure Crystal Content The zeolite crystal content (pure crystal content) was measured by the amount of water absorbed. That is, the compact was activated at 350 ° C. for 1 hour, and after cooling, allowed to stand in a desiccator at a temperature of 25 ° C. and a relative humidity of 80% for 16 hours or more, and the amount of equilibrium moisture adsorbed on the compact was measured.

For the measurement of the equilibrium moisture adsorption amount, the weight (M, supposed) of the activated compact after the activation and the weight (N, supposed) of the molded body in which the moisture adsorption was balanced were measured. (1).

(NM) / M × 100 (1) In addition, in the case of A-type zeolite, the content of pure crystals is
Equilibrium water adsorption of aA zeolite crystal powder 28.0
%, And in the case of X-type zeolite, the pure crystal content in the compact was determined based on the equilibrium water adsorption of the synthetic NaX-type zeolite crystal powder of 35.0%.

Pore Volume The bead compact was measured using a mercury intrusion porosimeter (manufactured by Amco) in a pressure range of 1 to 1500 kg / cm ² .

Abrasion Rate The abrasion rate was calculated according to the method for measuring the particle strength described in JIS-K-1464 (1962 version). That is, a molded body as a sample was previously subjected to a temperature of 25 ° C. and a relative humidity of 80%.
In the desiccator for more than 16 hours. Then, about 70 g of the sample was sieved for 3 minutes using a sieve (Model: JIS Z-8801, manufactured by Tokyo Screen Co., Ltd., model: JIS Z-8801) having 850 μm, 355 μm and a saucer, and then passed through the sieve from which the attached matter was removed.
After sieving for 50 minutes, 50 g of the remaining sample is accurately weighed, and at the same time, five 10-yen coins are set and shaken for 15 minutes. The wear rate was calculated by the following equation (2) using the sample dropped on the tray as Xg.

Abrasion rate (% by weight) = (X / 50) × 100 (2) X-ray diffraction test In order to confirm whether there is any impurity other than the A-type or X-type zeolite in the molded body, The sample was subjected to crystal analysis using an X-ray diffractometer (manufactured by Mac Science, model: MXP ³ ). Purity was confirmed by the absence of impurity peaks other than the peaks due to A-type or X-type zeolite.

Example 1 Synthetic sodium A-type zeolite powder (manufactured by Tosoh Corporation) and kaolin-type clay (manufactured by DRY BRANCH KAOLIN, trade name: 100 parts by weight)
Flat D) 25 parts by weight are mixed and kneaded with a mix muller granulator (manufactured by Shinto Kogyo Co., Ltd., model: MSG-05S), and finally A-type zeolite powder 10 is added while appropriately adding purified water.
After preparing by adding 60 parts by weight of purified water to 0 parts by weight, it was kneaded sufficiently. This kneaded product was treated with a marmerizer molding machine (manufactured by Fuji Paudal Co., Ltd., model: Q-230) to have a diameter of 1.
Roll-formed into beads of 4 to 2.8 mm and dried.
Next, a muffle furnace (manufactured by Advantech, model: KM-
After baking in a 600 ° C. atmosphere for 2 hours to sinter the kaolin-type clay using the above method, the mixture was cooled in the air and humidified so that the water content became about 25%. 100 g of this compact
(Activation weight) in a stainless steel reaction vessel (inner diameter: 105
mm × height: 180 mm) and immersed in an aqueous solution of sodium hydroxide having a concentration of 1.5 mol / l at 40 ° C.
After aging for an additional hour, the temperature was further raised to 80 ° C., and the mixture was allowed to stand for 4 hours to completely transfer the added clay to A-type zeolite.
It was sufficiently washed with water and dried at 60 ° C. for 16 hours to obtain a molded A-type low-wear zeolite bead. As a result of measuring the amount of water adsorption by the above method, it was 27.5%.
Equilibrium moisture adsorption of synthetic NaA type zeolite crystal powder 2
When the crystal content of the obtained molded body was calculated based on 8.0%, it was found to be 98.2%.

The obtained binderless, low-wear type A zeolite bead compact was dissolved in purified water in advance with calcium chloride (granular, manufactured by Central Glass Co., Ltd.) to a concentration of 0.5 mol / l. It was brought into contact with an aqueous calcium chloride solution at 50 ° C. for 3 hours while stirring using a three-one motor, and after performing calcium ion exchange, thoroughly washed with purified water and dried at 60 ° C. for 16 hours. Thereafter, activation treatment was performed at 400 ° C. for 1 hour in a tubular furnace (manufactured by Advantech) under air flow. The pure crystal content, pore volume, wear rate, and the like of the obtained molded body were measured by the above-mentioned methods. The results are shown in Table 1.

[0039]

[Table 1]

Further, as a result of performing a crystal analysis on the molded product by the X-ray diffraction test, no other phase, that is, no impurity was recognized.

Examples 2 to 6 A binderless, low abrasion type A zeolite bead molding was obtained in the same manner as in Example 1 except that the amount of clay and the concentration of the aqueous sodium hydroxide solution shown in Table 1 were used. Prepared. Table 1 shows the results of the measurement of the crystal content, the pore volume, and the wear rate by the above-described methods. Further, as a result of performing a crystal analysis by the X-ray diffraction test on these compacts, no other phase, that is, no impurity was recognized.

Example 7 A mixture of synthetic sodium X-type zeolite powder (manufactured by Tosoh Corporation) and 100 parts by weight of this powder was mixed with 25 parts by weight of kaolin-type clay (manufactured by DRY BRANCH KAOLIN, trade name: Flat D). Mixing and kneading with a Mahler granulator (manufactured by Shinto Kogyo Co., Ltd., model: MSG-05S), and finally adding 65 parts by weight of purified water to 100 parts by weight of X-type zeolite powder while appropriately adding purified water. After that, it was thoroughly kneaded. This kneaded product was roll-molded into a bead shape having a diameter of 1.4 to 2.8 mm using a marmalizer molding machine (manufactured by Fuji Paudal Co., model: Q-230) and dried. Next, a muffle furnace (manufactured by Advantech, model: K
(M-600) for 2 hours in an atmosphere of 600 ° C. to sinter the kaolin-type clay, and then cooled in the air and humidified to a water content of about 35%. This molded body 100
g (activation weight) in a stainless steel reaction vessel (inner diameter: 10
5mm x height: 180mm) 1.5 mol /
Liter of aqueous sodium hydroxide solution and 0.1 mol /
Immersion in 4 liters of mixed aqueous solution of sodium silicate
Aged at 0 ° C. for 1 hour, further heated to 90 ° C., left to stand for 6 hours to completely transfer the added clay to X-type zeolite, thoroughly washed with water, and dried at 60 ° C. for 16 hours. Thus, a low-wear X-type zeolite bead molded product was obtained. As a result of measuring the amount of water adsorption by the above method, 34.
3%. The crystal content of the obtained molded body was calculated based on the equilibrium water adsorption of the synthetic NaX type zeolite crystal powder of 35.0%, and was found to be 97.9%.

The obtained binder-less, low-abrasion X-type zeolite bead compact was previously dissolved in purified water so that calcium chloride (granular, manufactured by Central Glass Co., Ltd.) had a concentration of 0.5 mol / l. It was brought into contact with an aqueous calcium chloride solution at 50 ° C. for 3 hours while stirring using a three-one motor, and after performing calcium ion exchange, thoroughly washed with purified water and dried at 60 ° C. for 16 hours. Thereafter, activation treatment was performed at 400 ° C. for 1 hour in a tubular furnace (manufactured by Advantech) under air flow. The pure crystal content, pore volume, wear rate, and the like of the obtained molded body were measured by the above-mentioned methods, and the results are shown in Table 2.

[0044]

[Table 2]

Further, as a result of performing a crystal analysis on the molded product by the X-ray diffraction test described above, no other phase, that is, no impurity was recognized.

Examples 8 to 14 Except for using the amount of clay and the concentration of aqueous sodium hydroxide solution shown in Table 2, a binderless, low abrasion type X-type zeolite bead was obtained in the same manner as in Example 7. Prepared. Table 2 shows the results of the measurement of the crystal content, the pore volume, and the wear rate by the above-described methods. Further, as a result of performing a crystal analysis by the X-ray diffraction test on these compacts, no other phase, that is, no impurity was recognized.

Comparative Examples 1 to 9 Except that the amount of clay and the concentration of aqueous sodium hydroxide solution or aqueous sodium silicate solution shown in Table 3 were used, when the mother zeolite as the starting raw material powder was A-type zeolite, 1. When the mother zeolite was X-type zeolite, an A-type zeolite compact and an X-type zeolite compact were prepared in the same manner as in Example 7. Table 3 shows the results obtained by measuring the crystal content, the pore volume, and the wear rate by the above-described methods.

[0048]

[Table 3]

[0049]

As is evident from the above description, the binderless, low abrasion zeolite beads of the present invention have a high zeolite content and a large pore volume, so that the adsorption performance is high and low. It is a molded product having strength properties with excellent wear properties. Further, according to the production method of the present invention, a binderless, low-wear, zeolite bead molded article having a high content of A-type or X-type zeolite can be easily obtained.

[0050]

Claims (5)

[Claims] (1) a molded article of zeolite beads having low abrasion, wherein the zeolite content is 95% by weight or more of the total amount;
A molded article of low wear zeolite beads, characterized in that the pore volume is 0.2 cc / g or more. 2. The low-wear zeolite bead according to claim 1, wherein the zeolite is an A-type or X-type zeolite. 3. The molded article of low-wear zeolite beads according to claim 1, wherein cations of the zeolite are exchanged for calcium ions. 4. Zeolite powder and zeolite powder 100
After baking a molded body composed of 25 parts by weight or less of kaolin-type clay with respect to parts by weight, the molded body is brought into contact with an aqueous solution of sodium hydroxide or a mixed aqueous solution of sodium hydroxide and sodium silicate, and subjected to hydrothermal treatment, thereby obtaining The method for producing a low-wear zeolite bead according to any one of claims 1 to 3, wherein the kaolin-type clay is transferred to zeolite to desorb water. 5. The method for producing a low-wear zeolite bead product according to claim 4, wherein the ion-exchange is performed by contacting with calcium ions after hydrothermal treatment. Production method.