JPH04210243A - Catalyst for cleaning exhaust gas - Google Patents

Abstract

PURPOSE:To obtain a catalyst having heat resistance and durability by allowing a crystalline aluminosilicate containing alkaline earth metal to contain group Ib and/or group VIII metals of periodic table. CONSTITUTION:Alkaline earth metal such as barium or calcium is kneaded with silica source and alumina source to obtain the crystalline alumino silicate containing alkaline earth metal. And group Ib of periodic table such as copper, silver or platinum and/or group VIII elements are allowed to be contained therein. The catalyst for cleaning exhaust gas obtained in such a way does not lower the cleaning ability of exhaust gas even when it is brought into contact with the high temp. exhaust gas from the internal combustion engine of automobile, the boiler in factory or the like.

Description

[Detailed description of the invention]

[00011

[Field of Industrial Application] The present invention relates to a catalyst with improved heat resistance and durability for purifying exhaust gas discharged from internal combustion engines of automobiles, boilers of factories, etc. [0002] In recent years, various methods have been studied for purifying harmful components in exhaust gases discharged from internal combustion engines of industrial plants, automobiles, and the like. Conventionally, there is a method of removing harmful components in exhaust gas by bringing them into contact with a catalyst. For example, there is a method called catalytic reduction method, which uses ammonia. It requires a reducing agent such as hydrogen or carbon oxide, and also requires special equipment to recover or decompose the unreacted reducing agent. On the other hand, the catalytic cracking method does not require a special reducing agent and can remove harmful components in the exhaust gas, especially nitrogen oxides, by simply passing the exhaust gas through a catalyst layer, and is the simplest process. This is the preferred method. The Si 02 /A 1203 molar ratio containing copper ions as a catalyst used in this process is 20 to 10.
0 crystalline aluminosilicate catalyst (JP-A-60-1252
No. 50). [0003] In addition, in gasoline engines, lean combustion has become necessary for the purpose of improving fuel efficiency and reducing carbon dioxide emissions, but since the exhaust gas of this lean burn gasoline engine is an oxygen-rich atmosphere, Conventional three-way catalysts cannot be used, and as a method to remove harmful components,
A method using hydrophobic zeolite as a catalyst has been proposed (Japanese Unexamined Patent Publication No. 63-283727). [0004]

However, the crystalline aluminosilicate exhaust gas purification catalyst containing steel ions has a problem in that its activity is significantly reduced when the operating temperature is high. That is, the molar ratio of S i 02 /A I 203 containing copper ions is 20 to 1.
In the case of the crystalline aluminosilicate of No. 00, there was a problem in that the catalyst activity significantly decreased after contact with high-temperature exhaust gas. [0005] Hydrophobic zeolite, which has been proposed as a method for removing harmful components from the exhaust gas of lean-burn gasoline engines, has the problem of causing a significant decrease in catalytic activity after coming into contact with high-temperature exhaust gas, making it difficult to put it into practical use. It has not yet become a reality. [0006]

[Means for Solving the Problems] In order to prevent the above-mentioned conventional problem of reducing the exhaust gas purification activity of the exhaust gas purification catalyst due to contact with high-temperature exhaust gas, the present inventors have developed a crystalline catalyst as a result of various studies. Even if a catalyst using an alkaline earth metal-containing crystalline aluminosilicate produced by having an alkaline earth metal salt present in the raw materials for crystal production during production comes into contact with high-temperature exhaust gas, the exhaust gas purification activity decreases. They discovered that this does not occur, and completed the present invention. [0007] That is, the present invention provides an alkaline earth metal-containing crystalline aluminosilicate produced by allowing an alkaline earth metal salt to be present in the crystal production raw material during crystal production.
The present invention proposes an exhaust gas purification catalyst containing one or more metal elements selected from metals belonging to Group B and/or Group VIII. [00081 Hereinafter, the present invention will be described in detail. [0009] The alkaline earth metal-containing crystalline aluminosilicate used as the base material of the catalyst in the present invention is an alkaline earth metal-containing crystalline aluminosilicate produced by making an alkaline earth metal salt exist in the aluminosilicate production raw material. It is essential that it is an aluminosilicate. Crystalline aluminosilicate containing no alkaline earth metal cannot prevent the reduction in exhaust gas purification activity due to contact with high-temperature exhaust gas, which is the object of the present invention. or,
The method for producing the alkaline earth metal-containing crystalline aluminosilicate is not particularly limited as long as the alkaline earth metal is included during production. For example, a silica source, an alumina source and an alkaline earth metal source, and optionally an alkali source. Mix organic mineralizers, etc. and heat in an autoclave for 60 to 20 minutes.
It is produced by maintaining the temperature at 0°C. As the silica source, sodium silicate, colloidal silica, white carbon, water glass, etc. can be used, and as the aluminum source, aluminum nitrate, aluminum sulfate, sodium aluminate, aluminum hydroxide, alumina, etc. can be used. Amorphous silica-alumina can also be used. Preparation conditions can be arbitrarily selected depending on the desired zeolite species. Regarding ZSM-5, Japanese Patent Application Laid-Open No. 581
56528, JP-A-59-97523, etc. can also be used as a manufacturing method. [00101 The S i 02 /A 1203 molar ratio of the alkaline earth metal-containing crystalline aluminosilicate of the present invention is
Although there is no particular limitation as long as the alkaline earth metal is contained, it is preferable that the molar ratio is 20 or more. If the molar ratio is less than 20, there is a possibility that the heat resistance will be low. [00111 Beryllium, magnesium, calcium, strontium, barium, and radium can be used as alkaline earth metals added to the crystal production raw materials during crystal production. Particularly preferred alkaline earth metals are barium, calcium and strontium. [0012] The alkaline earth metal source includes inorganic and organic salts of the metal, such as chlorides, bromides, and carbonates. Nitrates, nitrites, acetates, formates, benzoates, tartrates, etc. can be used. Particularly preferred metal salts are nitrates, acetates or chlorides. [0013] The amount of alkaline earth metal present in the exhaust gas purification catalyst of the present invention is preferably such that the alkaline earth metal/AI atomic ratio is 0.05 to 10. If the amount of alkaline earth metal is less than 0.05 per gram atom of aluminum, sufficient exhaust gas purification activity cannot be maintained after contact with high-temperature exhaust gas, and if the amount is more than 10 equivalents, alkaline earth metal Not only is the effect small compared to the content of , but it may also have a negative effect on the heat resistance of the catalyst. [0014] An alkaline earth metal-containing crystalline aluminosilicate produced by allowing an alkaline earth metal salt to be present in the crystal production raw material during crystal production is a crystalline aluminosilicate containing an alkaline earth metal by ion exchange. Higher heat resistance than silicates. [0015] Further, in the present invention, it is essential to contain one or more metal elements selected from metals belonging to Group Ib and/or Group VII of the Periodic Table as a catalytically active component. These metallic elements are metals, ions, and oxides. It may be a complex or the like. Although the content of the metal element is not particularly limited, it is preferably 0.05 to 0.8 equivalent per gram atom of aluminum. If the amount of the metal element is less than 0.05 equivalent per gram atom of aluminum, harmful components in the exhaust gas may not be sufficiently removed. Further, if the amount is more than 0.8 equivalent, not only the effect is smaller than the content of the metal element, but also there is a possibility that the heat resistance of the catalyst will be adversely affected. [00163 Aluminum in the crystalline aluminosilicate mentioned here means aluminum forming the structure of the crystalline aluminosilicate, and is added as a binder or diluent when forming the crystalline aluminosilicate as a catalyst or carrier. It does not contain aluminum present in materials such as alumina sol, alumina, and silica-alumina, or aluminum cations introduced by exchanging cations by ion exchange. [0017] Group Ib and/or V of the periodic table of the present invention
■The method for incorporating one or more metal elements selected from metals belonging to Group II is to add an alkaline earth metal-containing crystalline aluminosilicate to an aqueous or non-aqueous solution containing the above-mentioned metal elements. (organic solvent, etc.). In this type of method for introducing metal elements, water is the most preferred medium from the operational point of view. Organic solvents can also be used as long as they can ionize the metal. For example, methanol. Alcohols such as ethanol, propatool etc., amides such as dimethylformamide, diacetamide etc. Solvents such as ethers such as diethyl ether and ketones such as dimethyl ketone, methyl ethyl ketone are suitable. Metal elements include steel, silver, gold, nickel, palladium, platinum, cobalt, rhodium, and iridium. Iron, ruthenium and osmium can be used. [0018] Particularly preferred metal elements are copper, silver, and platinum. These include cobalt and nickel. [0019] Examples of the metal element source include inorganic and organic salts of the metal, such as chlorides, bromides, carbonates, and sulfates. Nitrates, nitrites, sulfides, acetates, formates, benzoates, tartrates, etc. can be used. Particularly preferred metal salts are nitrates, acetates or chlorides. [00201 The method of introducing the metal element is not particularly limited, and may be either ion exchange or support, but one or more types of alkaline earth metal-containing crystalline aluminosilicate may be introduced from Group Ib and/or Group Ib of the periodic table. This is carried out by immersion in a solution containing a metal element belonging to Group VIII, or by flowing a solution containing the metal element into contact with a contact tower filled with an alkaline earth metal-containing crystalline aluminosilicate. When introducing a metal element, an ammine complex of the above metal can also be used. [00213 The concentration of the metal element in the solution, the solution amount, the contact time, etc. are determined according to Group Ib and/or VII of the periodic table.
One or more metal elements selected from the metal elements belonging to Group I can be appropriately selected under the conditions that the alkaline earth metal-containing crystalline aluminosilicate contains a predetermined amount. [0022] After the introduction of the gold metal element, the alkaline earth metal-containing crystalline aluminosilicate is washed, and if necessary, the alkaline earth metal-containing crystalline aluminosilicate is
It may be fired at a temperature in the range of -800°C, preferably 400-700°C. [0023] When calcining the alkaline earth metal-containing crystalline aluminosilicate after introducing the gold metal element, it can be calcined as is, but natural clay (for example, kaolin, halloysite, montmorillonite, etc.) and/or inorganic oxidation (e.g. binary gels such as alumina, silica, magnesia, titania, zirconia, hafnia, aluminum phosphate, silica-alumina, silica-zirconia, silica-magnesia, ternary gels such as silica-magnesia-alumina, etc.). It is also possible to sinter the granulated product. [00241 In order to use the catalyst according to the present invention for removing harmful components from exhaust gas, the contact surface with the exhaust gas may be a cylindrical bispherical shape, a Raschig ring shape, a honeycomb shape, or a monolith catalyst coated on a ceramic or metal honeycomb structure. It is preferable to form a large amount of gas into a shape that allows easy gas flow. [0025NAlso, the introduction of the metal element can be performed after molding. [0026] Alkaline earth is present in the raw material for producing crystals containing one or more metal elements belonging to Group Ib and/or Group VII I of the periodic table as described above. An alkaline earth metal-containing crystalline aluminosilicate catalyst produced in the presence of a metal salt is used as an exhaust gas purification catalyst. At this time, there are no particular restrictions on the origin of the exhaust gas,
It may be brought into contact with the catalyst. The temperature at that time was about 200
~1000°C, and the contact time is not particularly limited. [00271 The catalyst according to the present invention can be used in internal combustion engines of automobiles,
When purifying exhaust gas from factory boilers, etc., it shows high exhaust gas purification activity even after being heat-treated at high temperatures. [0028]

[Example 1] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. [0029] Example 1 (Synthesis of zeolite) 13.74 g of aluminum nitrate nonahydrate and 4.68 g of barium acetate
g in 400 g of water, and while vigorously stirring this solution, colloidal Silica Cataloid 5I-30 (Catalyst Kasei Co., Ltd., 5iCh; 30.4%, Na 20
:0.38%) 146.58g, then 127g of water.
Add 6.84g of sodium hydroxide dissolved in 0.4g. Furthermore, tetrapropylammonium bromide 1
9.5 g was added and stirring continued for about 15 minutes to obtain an aqueous gel mixture. S i 02 / A 1 in the raw material mixture
The 203 molar ratio is 40. [00301 This aqueous gel mixture was charged into an autoclave having an internal volume of 11, and crystallized by stirring at 160° C. for 16 hours. After solid-liquid separation of the product, it was washed with water, dried, and then heat-treated in air at 550°C for 5 hours to obtain zeolite Ba-1, which will serve as a base material for an exhaust gas purification catalyst. As a result of chemical analysis, its composition, expressed as the molar ratio of oxides on an anhydrous basis, was as follows: [003110,23Na20・0.72BaO-A1
203 ・46.8SiO2 Table 1 also shows the lattice spacing (d value) determined from the powder X-ray diffraction diagram. [0032] [Table 1] Example 2 (Synthesis of Zeolite) Using 27.48 g of aluminum nitrate nonahydrate, 7.91 g of sodium hydroxide, and 5.801 g of calcium acetate instead of barium acetate. Zeolite Ca-1 was synthesized in the same manner as in Example 1 except for this. As a result of chemical analysis, its composition, expressed as the molar ratio of oxides on an anhydrous basis, was as follows: [0033] 0.27Na2o-o, 65CaO-A
1203 ・26.03iO2 again. The lattice spacing (d value) determined from the powder X-ray diffraction diagram was basically the same as the values shown in Table 1. [0034] Example 3 (Synthesis of Zeolite) 6.87 g of aluminum nitrate nonahydrate and 2.0 g of sodium hydroxide.
39g, strontium acetate 3 instead of barium acetate
．． Zeolite 5r-1 was synthesized in the same manner as in Example 1 except that 77 g was used. As a result of chemical analysis, its composition, expressed as the molar ratio of oxides on an anhydrous basis, was as follows: [0035] 0.24Naz o-o, 70SrO-
A1203 78.5Si02 Also, the lattice spacing (d value) determined from the powder X-ray diffraction pattern was basically the same as the values shown in Table 1. [0036] Example 4 (Preparation of exhaust gas purification catalyst) 10 g of each of Ba-1, Ca-1, and 5r-1 obtained in Examples 1 to 3 was collected, and the amount was 10 times the number of Al atoms in the zeolite. Weighed so that the number of ammonium molecules is 1
Pour into a mol/1 ammonium chloride aqueous solution and bring the liquid temperature to 6.
The mixture was stirred at 0°C for 2 hours. After solid-liquid separation, wash thoroughly with water,
It was dried at 00°C for 10 hours. Subsequently, the zeolite was poured into a 0.1 mol/l copper acetate aqueous solution weighed so that the number of copper atoms was 5 times the number of A1 atoms in the zeolite, and the liquid temperature was 50°C.
The mixture was stirred for 20 hours. After solid-liquid separation, wash thoroughly with water and
It was dried at ℃ for 10 hours. The obtained catalysts were each Cu-
Ba-1, Cu-Ca-1, Cu-3r-1. The copper content (C
u O/A 1203 molar ratio) are shown in Table 2. [0037]

[Table 2] Example 5 (Preparation of exhaust gas purification catalyst) Ba-1, Ca-1, 5r-1 obtained in Examples 1 to 3
Collect 10 g of each and add them to a 1 mol/1 ammonium chloride aqueous solution weighed so that the number of ammonium molecules is 10 times the number of AI atoms in the zeolite,
The mixture was stirred for 2 hours at a liquid temperature of 60°C. After solid-liquid separation, it was thoroughly washed with water and dried at 100°C for 10 hours. Subsequently, it was poured into a 0.1 mol/I cobalt acetate aqueous solution weighed so that the number of cobalt atoms was 10 times the number of AI atoms in the zeolite, and the mixture was stirred at a liquid temperature of 80° C. for 20 hours. After solid-liquid separation, it was thoroughly washed with water and dried at 100°C for 10 hours. The obtained catalysts were Co-Ba-1, Co-Ca-1, and C, respectively. -3r-1. Table 3 shows the copper content (COO/A 1203 molar ratio) of the exhaust gas purification catalyst determined by chemical analysis. [0038]

[Table 3] Example 6 (Preparation of exhaust gas purification catalyst) Ba-1, Ca-1, 5r-1 obtained in Examples 1 to 3
Collect 10 g of each and add them to a 1 mol/L ammonium chloride aqueous solution weighed so that the number of ammonium molecules is 10 times the number of AI atoms in the zeolite.
The mixture was stirred for 2 hours at a liquid temperature of 60°C. After solid-liquid separation, the mixture was thoroughly rinsed with water and dried at 100°C for 10 hours. Subsequently, it was poured into a 0.1 mol/I aqueous nickel acetate solution weighed so that the number of nickel atoms was 10 times the number of A1 atoms in the zeolite, and stirred at a liquid temperature of 80° C. for 20 hours. After solid-liquid separation, it was thoroughly washed with water and dried at 100°C for 10 hours. The obtained catalysts were Ni-B-1, Ni-Ca-1, and Ni
-8r-1. Table 4 shows the copper content (NiO/A1203 molar ratio) of the exhaust gas purification catalyst determined by chemical analysis. [0039]

[Table 4] Comparative Example 1 (Synthesis of Zeolite) Zeolite was synthesized in the same manner as in Example 1 except that barium acetate was not added to the synthesis raw material, and comparative catalyst base material Z-1 was synthesized.
I got it. As a result of chemical analysis, its composition, expressed as the molar ratio of oxides on an anhydrous basis, was as follows: [004010,65Na20-A1203 ・45
．． 5SiCh again. The lattice spacing (d value) determined from the powder X-ray diffraction diagram was basically the same as the values shown in Table 1. [00411 Comparative Example 2 (Preparation of Comparative Catalyst) A comparative catalyst Cu-Z-1 was obtained in the same manner as in Example 4. The copper content (CuO/A) of the exhaust gas purification catalyst determined by chemical analysis
1203 molar ratio) are shown in Table 5. [0042] Comparative Example 3 (Preparation of Comparative Catalyst) A comparative catalyst Co-Z-1 was obtained in the same manner as in Example 5. The cobalt content (CO
O/A I 203 molar ratio) is shown in Table 5. [00431 Comparative Example 4 (Preparation of comparative catalyst) Comparative catalyst N1-Z-1 was obtained in the same manner as in Example 6. The nickel content (Ni
Table 5 shows the O/AI203 molar ratio. [0044]

[Table 5] Example 7 (Evaluation of hot water resistance of exhaust gas purification catalyst) Example 4,
2 g of the exhaust gas purification catalyst obtained in steps 5 and 6 was packed into a normal pressure fixed bed reaction tube, and 60 m of air with a water vapor concentration of 10% and 17 m of air were charged.
In, bottom, 900°C at a heating rate of 10°C/min.
and held for 6 hours. The power was turned off and the mixture was left to cool to room temperature. The hot water resistance was evaluated based on the crystallinity, which was defined as the ratio of the peak intensities of the d values before and after heat treatment in the X-ray diffraction pattern determined by powder X-ray diffraction method. The results are shown in Table 6. [004sl Comparative Example 5 (Hot water resistance evaluation gf1 of comparative catalyst)
The comparative catalysts obtained in Comparative Catalysts 2.3 and 4 were treated in the same manner as in Example 7, and their hot water resistance was evaluated by the same evaluation method. The results are shown in Table 6. [0046]

[Table 6] Example 8 (Evaluation of heat resistance based on exhaust gas purification ability) Example 4,
Exhaust gas purification catalysts prepared in 5 and 6. 65 g was packed into a normal pressure fixed bed reaction tube and heated under flowing reaction gas with the following composition (
After pretreatment at 600 ml/min, ), 500°C for 0.5 hour, the temperature was raised to 800°C at a constant rate, and the No.
The purification rate was measured (reaction 1). [0047] Also, corresponding gas composition No. 11000pp etc.
4% Co 1000100 0pp, 500ppm H2O4%N, balance was continued and heat treated at 800°C for 5 hours. After cooling, 2
0.0 at 00℃. After pretreatment of holding for 5 hours, the temperature was raised again at a constant rate to 800°C, and the No purification rate at each temperature was measured (
Reaction 2). [0048] Reaction 1 with No harmful components in the reaction gas
The results of evaluating heat resistance based on the change in No purification rate in Reaction 2 are shown in Tables 7 to 15. [00491

[Table 7] [Table 8]

[Table 9]

[Table 10]

[Table 11]

[Table 12]

[Table 13 [Table 14]

[Table 15] The No purification rate is expressed by the following formula. [0050]

[Equation 1] Comparative Example 6 (Evaluation of heat resistance based on exhaust gas purification ability of comparative catalyst)
The comparative catalysts obtained in Comparative Examples 2, 3 and 4 were used in Example 8.
The results of evaluating heat resistance using the same method as above are shown in Table 169, Table 17, and Table 18. [00511

[Table 16] [Table 17] From Tables 7 to 18, the alkaline earth metal-containing crystalline aluminosilicate exhaust gas purification catalyst of the present invention shows that even if the exhaust gas purification catalyst is kept in the reaction gas at 800°C for 5 hours, It can be seen that the decrease in exhaust gas purification ability was smaller than that of the comparative catalyst, and the heat resistance was improved. [0052]

[Effects of the Invention] As explained above, according to the present invention,
An alkaline earth metal-containing crystalline aluminosilicate produced by allowing an alkaline earth metal salt to be present in the crystal production raw material during crystal production, containing Group Ib and/or VII of the periodic table.
An exhaust gas purification catalyst containing one or more metal elements selected from Group I metals has the effect of purifying exhaust gas and maintaining high exhaust gas purification activity even after contact with high-temperature exhaust gas. Ta. [o o 53]

Claims (1)

[Claims] Claim 1: An alkaline earth metal-containing crystalline aluminosilicate produced by allowing an alkaline earth metal salt to be present in the raw material for crystal production during crystal production, containing a group Ib and/or VIII of the periodic table. An exhaust gas purification catalyst containing one or more elements selected from metals belonging to the group.