JPH05155612A - Ion-exchange method of zeolite - Google Patents

Abstract

PURPOSE:To obtain a zeolite adsorbent for ion exchange having a high adsorption capacity by bringing zeolite into contact with an aq. soln. contg. >=2-valence metal ion while specifying the pH of the soln. CONSTITUTION:Zeolite is brought into contact with an aq. soln. contg. a >=2-valence metal ion to exchange the cation contained in the zeolite crystal. In this case, the pH of the soln. is controlled to <=4. Either the batch process or the circulation process is exemplified as the ion-exchange method, and both processes can be used. When the zeolite powder is subjected to such ion exchange, the powder is compacted by the ordinary method, and the compact is activated and used as an adsorbent. Besides, when the preformed zeolite is subjected to ion exchange, the deposited moisture is dried off at room temp. to 150 deg.C, and the zeolite is activated at 350-600 deg.C. The adsorption of this adsorbent is increased by >=10% as compared with the one kept at >=pH 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zeolite ion exchange method. By this ion exchange, for example, a zeolite adsorbent suitable for use for the purpose of separating, purifying, and concentrating oxygen from a mixed gas containing nitrogen and oxygen as main components by an adsorption method can be manufactured.

[0002]

2. Description of the Related Art For example, A having a pore size of 5 Å
Type zeolite is usually produced as follows. First, a synthetic Na-A type zeolite crystal powder is brought into contact with an aqueous solution of calcium chloride, and sodium ions of 0.67 equivalent fraction or more are exchanged with calcium ions to adjust the pore diameter to 5 angstrom. After the ion exchange is completed, it is separated from the mother liquor and washed with an appropriate amount of washing water. When it is used as a molded body, a binder is further added for molding. in this case,
Ion exchange has no effect even if it is performed after molding. Clay-based binders are often used as binders for molding. In addition, after adding a molding aid such as carboxymethyl cellulose and the like, water is mixed and sufficiently kneaded, and molding is carried out by a usual molding method such as extrusion molding. By firing at a temperature of 450 ° C. to 700 ° C., a molded product of A-type zeolite having a pore size of 5 Å and physical strength capable of withstanding industrial use is produced.

[0003]

The adsorption capacity of the Ca-A type zeolite produced by such a method is not always high. If an adsorbent having a larger adsorption capacity than this can be produced, the amount of adsorbent used will be reduced. It is possible to reduce the size, and it is possible to downsize the adsorption device. As a result, the power cost can be reduced. However, it is not easy to increase the adsorption capacity, and until now, efforts have been made to reduce the amount of binder added at the time of molding and to develop a binderless technology. In order to achieve this, it is necessary to essentially increase the adsorption capacity of zeolite.
The present invention was made for the purpose of producing a zeolite having a large adsorption capacity.

That is, an object of the present invention is to provide a method for exchanging the cation of zeolite with a metal ion having a valence of 2 or more, such as Ca, which makes it possible to obtain an adsorbent having a larger adsorption capacity.

[0005]

Means for Solving the Problems The adsorption capacity of nitrogen and the like is closely related to the type of cations in the zeolite crystals and the ion exchange rate. Therefore, it can be easily inferred that if the cation having high selectivity to the target adsorbate (for example, nitrogen) is ion-exchanged, the adsorption capacity will be increased.
However, the present inventors have found that even the adsorbents having exactly the same ion exchange rate may cause a difference in adsorption capacity, and as a result of earnest studies on the ion exchange method of zeolite, they are used for ion exchange. The inventors have found a close relationship between the pH of the aqueous solution and the adsorption capacity, and completed the present invention.

That is, according to the present invention, when the zeolite is brought into contact with an aqueous solution containing a metal ion having a valence of 2 or more, the cations contained in the zeolite crystals are ion-exchanged.
The gist of the present invention is a method for ion-exchanging zeolite by bringing the pH of the aqueous solution to 4 or less and then performing the contact.

The present invention will be described in detail below.

As the zeolite to be subjected to the ion exchange, any of naturally occurring zeolite and synthesized zeolite by a known method can be used. For example, A-type zeolite and faujasite-type zeolite can be mentioned. In the following description, synthetic Na-A type zeolite and X type zeolite will be described as examples. The zeolite used for ion exchange may be in the form of powder or crushed product, and it may be in the form of powder or crushed product.
It may be molded into a molded body in advance, such as the ion exchange method disclosed in Japanese Patent No. 60616. Further, it is more effective if it is subjected to a binderless treatment. The zeolite powder or molded body is contacted with an aqueous solution in which a salt of a metal having a valence of 2 or more, such as calcium, is dissolved to carry out ion exchange. Alkaline earth metal salts include most commonly used chlorides, nitrates,
Of the salts such as sulfates, hydrogen carbonates, acetates, hydroxides and oxides, those having sufficient solubility can be used. The concentration of the aqueous solution used for ion exchange is 1N or less, especially 0.7N
It is preferable to carry out the following concentrations. The temperature of ion exchange is not particularly limited, but a temperature of 40 ° C. or higher, preferably 60 ° C. or higher is desirable from the viewpoint of efficiency such as ion exchange rate. The ratio of the zeolite to the solution cannot be limited because it depends on the concentration of the solution, the temperature, etc., but it may be a ratio sufficient to carry out ion exchange to a desired ion exchange rate. The pH of the aqueous solution used for ion exchange must be 4 or less, but at a pH of 1 or less, the crystals of the A-type zeolite easily disintegrate, and the X-type zeolite is more difficult to disintegrate than that. Therefore, the pH should be practically set to about 2 or higher.

Under such conditions, the exchangeable cations contained in the zeolite crystals are ion-exchanged with desired metal ions. The ion exchange method includes a batch method (batch method), a column flow method, and the like, but any method may be used.

When the zeolite powder is subjected to ion exchange in this way, it is molded by a usual method, activated and used as an adsorbent. Further, when the preformed zeolite is subjected to ion exchange, the previously attached water is dried at room temperature to 150 ° C. and activated at a temperature of 350 to 600 ° C.

When the zeolite adsorbent is produced by this method, the adsorption capacity can be increased by 10% or more as compared with the case where the pH of the aqueous solution used for ion exchange is 5 even with the same ion exchange rate.

[0012]

The calcium chloride aqueous solution has a pH of about 5 due to the action of hydrolysis and the like unless the pH is adjusted. Conventionally, this solution has been used for ion exchange. This solution contains not only Ca ²⁺ ions but also Ca (OH) ⁺ ions in a considerable proportion, and these are directly ion-exchanged with the cations of the zeolite by the ion exchange treatment, and Ca (OH) ⁺ ions are It is inactive in the adsorption capacity of zeolites, which makes it impossible to obtain zeolites having a high adsorption capacity by the conventional method; on the other hand, in the case of a solution having a pH of 4 or less, for example, in the case of calcium, Ca (OH) ⁺ ions are not present or It is presumed that the zeolite obtained by the method of the present invention has a high adsorption capacity due to the small content ratio.

[0013]

According to the method of the present invention, it is possible to produce a zeolite adsorbent having a larger adsorption capacity than conventional adsorbents.

As is clear from the above description, according to the method of the present invention, (1) an adsorbent having a large adsorption capacity can be produced, and (2) as a result, the amount of adsorbent used can be reduced. It is possible to downsize the adsorption device and the like.

[0015]

EXAMPLES Each measuring method in Examples and Comparative Examples is as follows. <Static adsorption capacity measuring method> The static adsorption capacity was measured by the capacitance method. As the pretreatment, activation was performed at 350 ° C. for 2 hours under a pressure of 0.01 mmHg or less. After introducing the nitrogen gas, the adsorption temperature and the adsorption pressure were set to −10 ° C. and 700, respectively.
After holding at mmHg and reaching sufficient equilibrium, the adsorption capacity (Nc
c / g) was measured. <Dynamic Evaluation Method> Using the dynamic evaluation apparatus shown in FIG. 1, the amount of product oxygen gas taken out and its oxygen concentration were determined according to the following operating procedure. The operation was performed at 25 ° C.

The adsorption tower (7) is filled with about 1300 g of a zeolite adsorption separating agent. Blower (1) during adsorption process
Air compressed to 0.2 kg / cm ² G with a solenoid valve (2,
4, 5) are opened and flowed in the adsorption tower. The flow rate at that time was adjusted by a flow meter (9). During the regeneration process, the solenoid valves (2, 4, 5) were closed, the solenoid valve (3) was opened, and the pressure was reduced by the vacuum pump (12). The ultimate pressure at this time is 180 m
The mHg was kept constant. During the pressure recovery step, the solenoid valve (3) is closed, the solenoid valve (4) is opened, and the product oxygen gas in the pressure accumulator (8) is used to restore the pressure in the adsorption tower. The time of each step was 1 minute, and the operation of the solenoid valve was controlled by a sequencer. The oxygen concentration of the product oxygen gas was read by the oxygen concentration meter (10) after the value became steady, and the accurate amount of product oxygen gas taken out was calculated from the value of the integrated flow meter (11). The pressure was read with a pressure gauge (8).

Example 1 100 parts by weight of a powder of commercially available sodium A type zeolite (Zeorum A4 manufactured by Tosoh Corporation) (about 150 μ or less),
20 parts by weight of a clay-based binder, 5 parts by weight of an organic molding aid (carboxymethyl cellulose sodium salt) and 1 part by weight of sodium hydroxide are mixed, and water is further added and kneaded,
Using a usual extrusion molding machine, a die having a diameter of 1.5 mm was passed through for extrusion molding to obtain a molded body having a length of about 5 to 15 mm. The molded body was dried in a ventilation dryer at a temperature of 60 ° C. until the moisture content of the molded body became 30% by weight or less. Then, it was baked in a furnace at 550 ° C. for 2 hours. The water content of the fired compact was 2% by weight. The molded body was hydrated until the water content became about 20% by weight.
As described in JP-A-2-157119, this molded product was brought into contact with a 1.6 mol / liter aqueous sodium hydroxide solution to crystallize the added clay-based binder into A-type zeolite. This is 60mm in diameter x 200
The column of mm was packed with about 300 g. 1N in this column
1N hydrochloric acid was added dropwise to the calcium chloride aqueous solution (1) to adjust the pH to 4, then heated to 80 ° C., and circulated from the lower part of the column to the upper part at a flow rate of 4.2 cc / min. The distribution time was 12 hours. After the circulation of the aqueous calcium chloride solution was completed, the aqueous calcium chloride solution in the column was drained and washed with distilled water. Distilled water remains at room temperature (about 20 ° C) 30
Flowing was performed from the lower part of the column to the upper part at a flow rate of cc / min for 2 hours to complete the washing. Next, the product was taken out from the column and dried in a ventilation dryer at a temperature of 25 ° C. for 15 hours until the moisture content of the molded product was 40% by weight or less. The calcium ion exchange rate of the dried molded body was measured by the atomic absorption photometry, and as a result, the ratio with the aluminum atoms contained in the zeolite crystals (2 × Ca / Al) was 0.94. After drying, a tubular furnace having an inner diameter of 40 mm and a length of 900 mm was charged with a dry weight of about 500 g, and activated at 500 ° C. for 1 hour while flowing 8 liters / minute of air. afterwards,
When the nitrogen adsorption capacity was measured by the method described above, it was 2
It was 6.0 Ncc / g. Further, according to the result of the dynamic evaluation, 93% of oxygen is 64.
9 liters were obtained.

Example 2 An operation was carried out under the same conditions as in Example 1 except that the pH of the solution was adjusted to 3 and ion exchange was carried out.
The ion exchange rate of the sample thus prepared was 0.9.
It was 1. Further, when the nitrogen adsorption capacity was measured by the method described above after the activation in the tubular furnace under exactly the same conditions as in Example 1, it was 26.7 Ncc / g. Further, according to the result of dynamic evaluation, 93% of oxygen was obtained in an amount of 65.3 liters per hour of 1 kg of the adsorbent.

Example 3 An operation was carried out under the same conditions as in Example 1 except that the pH of the solution was adjusted to 2 and ion exchange was carried out.
The ion exchange rate of the sample thus prepared was 0.9.
It was 6. Further, when the nitrogen adsorption capacity was measured by the above-mentioned method after activating in a tubular furnace under exactly the same conditions as in Example 1, it was 25.8 Ncc / g. According to the results of dynamic evaluation, 93% of oxygen was obtained in an amount of 65.0 liters per 1 kg of the adsorbent.

Example 4 A sodium X type zeolite (Zeorum F-9, manufactured by Tosoh Corporation) was used in place of the sodium A type zeolite, and the molding was performed in the same manner as in Example 1 to contain 2 wt% of SiO ₂ 2.2.
The added clay-based binder was crystallized into X-type zeolite by contacting with mol / l sodium hydroxide. The column was packed as in Example 1 and the column was charged with 1.0N.
An appropriate amount of 1N hydrochloric acid solution was added dropwise to the above calcium chloride aqueous solution to adjust the pH to 4, heated to 80 ° C., and circulated from the lower part of the column to the upper part at a flow rate of 4.2 cc / min. The distribution time was 12 hours. After the completion of circulation of the calcium chloride aqueous solution, the calcium chloride aqueous solution in the column was drained, washed in the same manner as in Example 1, and dried at a temperature of 25 ° C. for 15 hours. The calcium ion exchange rate of the dried compact was 0.95 as a result of measurement by an atomic absorption photometry. Further, when the nitrogen adsorption capacity was measured by the method described above after activating in a tubular furnace under exactly the same conditions as in Example 1, it was 27.5 Ncc / g. According to the result of dynamic evaluation, 93% of oxygen was obtained in an amount of 66.1 Nl per 1 kg of the adsorbent.

Example 5 The procedure of Example 4 was repeated except that the pH of the solution was adjusted to 3 and ion exchange was performed.
The ion exchange rate of the sample thus prepared was 0.9.
It was 7. Further, the nitrogen adsorption capacity was measured by the method described above after the activation in the tubular furnace under the same conditions as in Example 1, and it was 27.7 Ncc / g. According to the results of dynamic evaluation, 93% of oxygen was obtained in an amount of 66.7 liters per hour of 1 kg of the adsorbent.

Example 6 The procedure of Example 4 was repeated except that the pH of the solution was adjusted to 2 and ion exchange was performed.
The ion exchange rate of the sample thus prepared was 0.9.
It was 1. Further, when the nitrogen adsorption capacity was measured by the method described above after activating in a tubular furnace under exactly the same conditions as in Example 1, it was 26.6 Ncc / g. According to the results of dynamic evaluation, 93% of oxygen was obtained in an amount of 63.1 liters per hour of 1 kg of the adsorbent.

Comparative Example 1 The procedure of Example 4 was repeated except that the pH of the solution was adjusted to 8 and ion exchange was performed.
The ion exchange rate of the sample thus prepared was 0.9.
It was 3. Moreover, when the nitrogen adsorption capacity was measured by the method described above after activation in a tubular furnace under exactly the same conditions as in Example 1, 23. It was Ncc / g. Moreover, according to the result of the dynamic evaluation, 93% of oxygen is 1% per 1 kg of the adsorbent.
Obtained 60.3 liters per hour.

Comparative Example 2 The procedure of Example 4 was repeated except that the pH of the solution was adjusted to 10 and ion exchange was performed. The ion exchange rate of the sample thus prepared was 0.94. Moreover, after activating in a tubular furnace under exactly the same conditions as in Example 1, the nitrogen adsorption capacity was measured by the method described above, and was 21.1 Ncc / g. Moreover, according to the results of the dynamic evaluation, 93% of oxygen is adsorbent 1
57.1 Nl was obtained per hour per kg.

Comparative Example 3 The procedure of Example 4 was repeated except that the pH of the solution was adjusted to 8 and ion exchange was performed.
The ion exchange rate of the sample thus prepared was 0.9.
It was 6. Moreover, after activating in a tubular furnace under exactly the same conditions as in Example 1, the nitrogen adsorption capacity was measured by the method described above, and was 22.5 Ncc / g. According to the results of dynamic evaluation, 93% of oxygen was obtained in an amount of 61.1 liters per hour of 1 kg of the adsorbent.

Comparative Example 4 The procedure of Example 4 was repeated except that the pH of the solution was adjusted to 10 and ion exchange was performed. The ion exchange rate of the sample thus prepared was 0.94. Moreover, after activating in a tubular furnace under exactly the same conditions as in Example 1, the nitrogen adsorption capacity was measured by the method described above, and was 20.8 Ncc / g. Moreover, according to the results of the dynamic evaluation, 93% of oxygen is adsorbent 1
58.3 Nl was obtained per hour per kg.

[Brief description of drawings]

FIG. 1 is a system diagram of a dynamic evaluation device for an adsorption separation agent in Examples and Comparative Examples.

[Explanation of symbols]

 1: Blower 2-5: Solenoid valve 6: Pressure gauge 7: Adsorption tower 8: Accumulation tower 9: Flow meter 10: Oxygen concentration meter 11: Integrated flow meter 12: Vacuum pump

Claims (1)

[Claims] 1. When the zeolite is brought into contact with an aqueous solution containing divalent or higher valent metal ions to ion-exchange the cations contained in the zeolite crystals, the pH of the aqueous solution is set to 4
An ion exchange method for zeolite, characterized in that the above contact is carried out after the following.