JPH04224108A - Production of cobalt-containing zeolite - Google Patents

Abstract

PURPOSE:To produce cobalt-containing zeolite useful for catalysts for various organic reactions, catalysts for environmental purification, and adsorbents with superior reproducibility. CONSTITUTION:The method is a manufacturing method for cobalt-containing zeolite characterized by applying ion exchange to cobalt and subjecting zeolite having a composition represented, expressed in terms of anhydrous oxide, by formula xCoO.yM2/nO.Al2O3.zSiO2 [where M means cation excluding that of Co, (n) means the valence of the cation M, x=0.2 to 2.0, y=0.01 to 1.0, and z=10-200] to burning at 500-900 deg.C while allowing the air having <=5000ppm moisture content to flow at >=SV400hr<-1>.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a method for producing cobalt-containing zeolite, and more particularly to a method for producing cobalt-containing zeolite, which is characterized by carrying out a calcination treatment under specific conditions. be.

0002

BACKGROUND OF THE INVENTION Cobalt-containing zeolites are useful substances that have been proposed as catalysts for various organic reactions, environmental purification catalysts, and adsorbents. For example, JP-A-63-2837
No. 27, JP-A-1-130735, Japanese Patent Application No. 1-130735, Japanese Patent Application No. 1-130735
No. 331,740 describes that zeolite containing cobalt is effective as a catalyst for removing nitrogen oxides from exhaust gas even in exhaust gas containing excess oxygen.

[0003] The reason why cobalt-containing zeolite has characteristic effects in each application is presumed to be that cobalt exists in the zeolite as a cation or as a highly dispersed cobalt compound within the pores of the zeolite. .

[0004] Cobalt-containing zeolite having such characteristics is generally prepared by ion exchange or impregnating support using a water-soluble cobalt compound, and an example of the preparation method is disclosed in Japanese Patent Application No. 1-331740, etc. can be mentioned.

[0005]

[Problems to be Solved by the Invention] As mentioned above, cobalt-containing zeolite is generally prepared by ion exchange using a cobalt compound, but it is usually used for various purposes by drying and calcining after ion exchange. Ru. During ion exchange, the operating conditions, i.e., the type of cobalt compound used for ion exchange, the pH of the exchange solution, the ratio of cobalt ions to the number of ion exchange sites of zeolite (amount of Al2O3 contained), solid-liquid ratio, cobalt ion concentration, addition Cobalt-containing zeolite formed depending on the presence or absence of substances, temperature, etc., especially,
It is known that the states of cobalt are different. but,
Even if ion exchange is performed under the same operating conditions, cobalt-containing zeolite with similar properties may not be obtained. Therefore, it is expected that the drying and calcination steps after ion exchange are important, but conventional However, the preferred drying and firing methods were not clear.

[0006]

[Means for Solving the Problems] In view of the current situation, the present inventors have conducted intensive studies on the preparation method of cobalt-containing zeolite, and have found that cobalt exists in ion exchange sites or is highly dispersed in pores, etc. The inventors have discovered a method for preparing a cobalt-containing zeolite that exists in a state that has favorable properties, and have completed the present invention.

That is, in producing a cobalt-containing zeolite, the present invention ion-exchanges cobalt and then converts the zeolite having a composition as shown in the following formula as an oxide on an anhydrous basis into a zeolite with a water content of 5000 ppm or less. 500℃ while circulating certain air at SV400hr-1 or more
The present invention provides a method for producing cobalt-containing zeolite, which is characterized by firing at a temperature of ~900°C.

xCoO・yM2/nO・Al2O3・zSiO2 (where M represents a cation other than Co, and n represents the valence of the cation M. x=0.2 to 2.0, y=0 .01～
1.0, z=10-200) The present invention will be explained in more detail below.

[0009] Zeolite is usually called a crystalline aluminosilicate, and its skeleton is composed of SiO4 tetrahedra and AlO4 tetrahedra, but many types are known due to differences in the bonding styles of each tetrahedron. . Zeolite is
Since the crystal structure differs depending on the type, it can be identified by powder X-ray diffraction. A large number of natural and synthetic zeolites are known to date. Examples include A-type zeolite, chabasite, erionite, clinoptilolite, ferrierite, ZSM-5, ZSM-11, mordenite, faujasite, L-type zeolite, and the like. The SiO2/Al2O3 ratio of the zeolite used in the present invention is preferably 10 to 200. S
Examples of the zeolite having an iO2/Al2O3 ratio of 10 to 200 include ferrierite, ZSM-5, ZSM-11, mordenite, and faujasite. ZSM-5 is preferred as the zeolite used in the present invention. Moreover, the manufacturing method of these zeolites is not limited.

The cobalt-containing zeolite of the present invention can also be produced by forming the zeolite in advance. There are no particular restrictions on the binder used when molding zeolite, but clay minerals such as kaolin, attapulgite, montmorillonite, bentonite, allophane, and sepiolite, and inorganic oxides such as silica, titania, and zirconia can be used. . Alternatively, it may be a binderless zeolite molded product that is directly synthesized without using a binder. Moreover, zeolite can be wash-coated onto a cordierite or metal honeycomb base material.

[0011] Although there are no restrictions on the method of incorporating cobalt into the zeolite, an ion exchange method is preferred. The method is not particularly limited, and ion exchange may be performed using a commonly used aqueous solution containing cobalt. The concentration of cobalt ions in the aqueous solution during ion exchange can be arbitrarily set depending on the desired ion exchange rate. Further, cobalt can be used in the form of a soluble salt, and as the soluble salt, nitrate, acetate, oxalate, hydrochloride, etc. can be suitably used. Further, when performing cobalt ion exchange, ammonia or the like may be added to adjust the pH. There is no problem even if the zeolite contains cations other than cobalt before the zeolite contains cobalt. Furthermore, after the zeolite contains cobalt, there is no problem even if the zeolite contains cations other than cobalt. The sample subjected to ion exchange treatment is subjected to solid-liquid separation, washing, drying, and then firing.

[0012] In the present invention, firing is performed when the moisture content is 50%.
00 ppm or less, preferably 2000 ppm or less, at a SV of 400 hr-1 or more, preferably 600 h
It is characterized by firing at 500°C to 900°C while flowing at r-1 or higher. Here, SV is the air flow rate F(
cc/hr) divided by the volume V of the agent to be fired. When the moisture content of the air to be circulated is high, or when the SV
When is small, the water desorbed from the zeolite increases the water vapor partial pressure in the atmosphere, and cobalt is more likely to be hydrolyzed and aggregate on the outer surface of the zeolite as an oxide.
On the other hand, zeolite is thought to be easier to dealumate. Further, if the calcination temperature is lower than 500°C, the stabilization of cobalt at the ion exchange site of the zeolite is insufficient, and if it is higher than 900°C, the structure of the zeolite is destroyed.

[0013]

EXAMPLES The present invention will be explained in more detail in the following examples. However, the present invention is not limited to these examples.

Example 1 A ZSM-5-like zeolite was synthesized according to the method of Example 5 of JP-A-59-54620. It had the following chemical composition, expressed as molar ratios of oxides on an anhydrous basis.

1.1Na2O・Al2O3・43SiO2 Ammonium type ZSM-5 prepared by ion-exchanging this with an aqueous ammonium chloride solution;
1800ml of an aqueous solution of cobalt(II) acetate tetrahydrate
1 and stirred at 80°C for 16 hours. After solid-liquid separation of the slurry, the zeolite cake was added to the prepared aqueous solution having the above composition and the same operation was performed. After solid-liquid separation, it was thoroughly washed with water and dried at 110°C for 10 hours to form Co-ZSM-
5-A was prepared. It had the following chemical composition, expressed as molar ratios of oxides on an anhydrous basis.

1.39CoO・0.01Na2O・Al
2O3・43SiO2 Fill a quartz tube with 10ml of this Co-ZSM-5-A, and add 400ml/dry air with a moisture content of 190ppm.
Co-ZSM-
5-A1 was obtained.

Example 2 10 ml of Co-ZSM-5-A obtained in Example 1 was filled into a quartz tube, and dry air with a water content of 190 ppm was flowed at 100 ml/min (SV = 1200 hr-1). At the same time, the temperature was raised to 850°C at a rate of 10°C/min in a circular electric furnace, and the temperature was maintained at that temperature for 5 hours to perform a firing treatment.
Co-ZSM-5-A2 was obtained.

Example 3 10 ml of Co-ZSM-5-A obtained in Example 1 was filled into a quartz tube, and dry air with a moisture content of 190 ppm was flowed at 400 ml/min (SV = 2400 hr-1). At the same time, the temperature was raised to 500 °C at a rate of 10 °C/min in a circular electric furnace, and the temperature was maintained at that temperature for 5 hours to perform a firing treatment.
Co-ZSM-5-A3 was obtained.

Example 4 10 ml of Co-ZSM-5-A obtained in Example 1 was filled into a quartz tube, and 4 ppm of dry air with a water content of 3 ppm was added.
While flowing at 00ml/min (SV = 2400hr-1), the temperature was raised to 800°C at 10°C/min in an annular electric furnace, and the temperature was held for 5 hours to perform a firing treatment.
-ZSM-5-A4 was obtained.

Example 5 10 ml of Co-ZSM-5-A obtained in Example 1
was filled into a quartz tube, and dry air with a moisture content of 2000 ppm was supplied at 400 ml/min (SV = 2400 hr-1).
800℃ at 10℃/min in an annular electric furnace while flowing with
The temperature was raised to .degree. C., and the temperature was maintained for 5 hours to perform a firing treatment, thereby obtaining Co-ZSM-5-A5.

Comparative Example 1 10 ml of Co-ZSM-5-A obtained in Example 1 was filled into a quartz tube, and dry air with a water content of 190 ppm was flowed at a rate of 50 ml/min (SV=300 hr-1). Meanwhile, the temperature was raised to 800°C at a rate of 10°C/min in a circular electric furnace, and the firing process was performed by holding at that temperature for 5 hours.
-ZSM-5-A6 was obtained.

Comparative Example 2 10 ml of Co-ZSM-5-A obtained in Example 1 was filled into a quartz tube, and dry air with a water content of 190 ppm was flowed at 200 ml/min (SV = 1200 hr-1). At the same time, the temperature was raised to 400 °C at a rate of 10 °C/min in a circular electric furnace, and the temperature was maintained at that temperature for 5 hours to perform a firing treatment.
Co-ZSM-5-A7 was obtained.

Comparative Example 3 10 ml of Co-ZSM-5-A obtained in Example 1 was filled into a quartz tube, and dry air with a moisture content of 190 ppm was flowed at 200 ml/min (SV=1200 hr-1). At the same time, the temperature was raised to 900°C at a rate of 10°C/min in an annular electric furnace, and the temperature was maintained for 5 hours to perform a firing treatment.
Co-ZSM-5-A8 was obtained.

Comparative Example 4 10 ml of Co-ZSM-5-A obtained in Example 1 was filled into a quartz tube, and air with a moisture content of 9000 ppm was flowed at 200 ml/min (SV=1200 hr-1). The temperature was raised to 800°C at a rate of 10°C/min in a circular electric furnace, and the firing process was performed by holding at that temperature for 5 hours.
o-ZSM-5-A9 was obtained.

Comparative Example 5 10 ml of Co-ZSM-5-A obtained in Example 1 was filled into a quartz tube, and air with a water content of 6000 ppm was flowed at a rate of 200 ml/min (SV=1200 hr-1). The temperature was raised to 800°C at a rate of 10°C/min in a circular electric furnace, and the firing process was performed by holding at that temperature for 5 hours.
o-ZSM-5-A10 was obtained.

Example 6 Co-ZS obtained in Examples 1 to 5 and Comparative Examples 1 to 5
The NO adsorption amount of M-5 was measured. Measurement of NO adsorption amount is as follows:
After the sample was evacuated at 500°C for 1 hour, the test was carried out at 25°C. Table 1 shows the NO adsorption amount at 600 Torr.

Example 7 Co-ZS obtained in Examples 1 to 5 and Comparative Examples 1 to 5
Exhaust gas purification performance was investigated using M-5.

[0028] Each Co-ZSM-5 was press-molded and then pulverized to size 42 to 80 mesh. 2ml of the mixture was filled into a normal pressure fixed bed flow reaction tube, and the gas simulating the exhaust gas of a lean burn engine shown below was heated to a space velocity of 300.
It ran at a rate of 00/hr. Table 1 shows the results of measuring the NO purification rate at a steady state of 400°C after pretreatment at 500°C for 30 minutes.

Gas composition CO 0.1vol% H2 0.033vol% C3H6
0.04vol% NO 0.06vol%CO2
10vol% H2O 3vol% O2 4vol% N2 Balance

[0030]

[Table 1] Example 8 Ammonium type ZSM-5 prepared in Example 1; 200
g was added to 1800 ml of an aqueous barium chloride solution having a concentration of 1.09 mol/l, and the mixture was stirred at 80° C. for 16 hours. After solid-liquid separation, the mixture was thoroughly washed with water, then poured into 700 ml of an aqueous solution of 0.23 mol/l cobalt (II) acetate tetrahydrate, and stirred at 80° C. for 16 hours. After solid-liquid separation of the slurry, the zeolite cake was added to the prepared aqueous solution having the above composition and the same operation was performed. After solid-liquid separation, it was thoroughly washed with water and dried at 110°C for 10 hours to form Co-Ba-ZSM-5.
-A was prepared. It had the following chemical composition, expressed as molar ratios of oxides on an anhydrous basis.

0.49CoO・0.58BaO・Al2
O3.43SiO2 10ml of this Co-Ba-ZSM-5-A was filled into a quartz tube, and 400ml of dry air with a water content of 190ppm was added.
Co-B
a-ZSM-5-A1 was obtained.

Comparative Example 6 Co-Ba-ZSM-5-A obtained in Example 8; 10
ml into a quartz tube and air with a water content of 6000 ppm at 200 ml/min (SV = 1200 hr-1)
800℃ at 10℃/min in an annular electric furnace while flowing with
The temperature was raised to .degree. C., and the temperature was maintained for 5 hours to perform a firing treatment, thereby obtaining Co-Ba-ZSM-5-A2. Example 9 Co-Ba-ZS prepared in Example 8 and Comparative Example 6
Regarding M-5, the NO adsorption amount was measured in the same manner as in Example 6. The results are shown in Table 2.

Example 10 Co-Ba-ZSM prepared in Example 8 and Comparative Example 6
-5, the exhaust gas purification performance was measured in the same manner as in Example 7. The results are shown in Table 2.

[0034]

[Table 2]

[0035]

As described above, according to the method of the present invention, high-performance cobalt-containing zeolite can be produced with good reproducibility. Although the reason for this is not clear, it is suggested that the water vapor partial pressure and temperature during calcination have a large influence on the state of cobalt, which is thought to affect the performance of cobalt-containing zeolites.

According to the method of the invention, the water content is 500
When firing at 500°C to 900°C while flowing air with a concentration of 0 ppm or less at a SV of 400 hr-1 or more, the water vapor partial pressure becomes sufficiently low, so copper hydrolysis is suppressed and cobalt is uniformly dispersed in the ion exchange sites. A cobalt-containing zeolite can be obtained.

Claims (1)

[Claims] [Claim 1] In producing cobalt-containing zeolite, after ion-exchanging cobalt, zeolite having the following formula expressed as an oxide on an anhydrous basis is mixed with air having a water content of 5000 ppm or less. SV400
A method for producing cobalt-containing zeolite, which comprises firing at 500°C to 900°C while circulating at hr-1 or more. xCoO・yM2/nO・Al2O3・zSiO2 (in the formula, M represents a cation other than Co, and n represents the valence of the cation M. x = 0.2 ~ 2.0, y = 0.01 ~
1.0, z=10~200)