JPS6312346A - Production of catalytic carrier containing aluminium titanate as main component - Google Patents

Abstract

PURPOSE:To obtain a porous catalytic carrier having high strength by adding a sol or gel-like material capable of forming the aluminium titanate by calcining it to the aluminium titanate powders having a specific particle size, kneading and forming, followed by calcining it. CONSTITUTION:The sol or gel-like material capable of forming the aluminium titanate by calcining such as a mixture of alumina sol and orthotitanic acid sol is added to the aluminium titanate powders having 3mum mean particle size. Any one of the aluminium type and the titanium type additives is preferably to be the gel or sol-like material. The used amount of the aluminium titanate to the additives is over zero to <30wt% on the weight based on the additives. The porous aluminium titanate carrier obtd. by adding said mixture, followed by kneading, forming and calcining it, is used to the catalytic carrier for burning which has an excellent strength and heat-resisting property.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing a catalyst carrier containing aluminum titanate as a main component, and particularly a method for producing a porous catalyst carrier containing aluminum titanate as a main component. It is related to.

(Prior Art) The catalytic combustion method is characterized by a small amount of NOx generated in the combustion gas, and in recent years, research has been actively conducted to apply this property to various combustors.

Characteristics that a combustion catalyst used in a combustor should have include:
The following items are listed.

(1) There is no change in physical properties even when used continuously at high temperatures of 1200 to 1600°C.

(2) The strength of the catalyst is high.

(3) Sufficiently withstand sudden temperature changes during startup and shutdown.

Among these, regarding (1), La-β has excellent heat resistance.
-Aj! 203 carrier (Japanese Patent Application Laid-open No. 59-080752),
Alternatively, a B a A l 12 0 ,y carrier (Special No. 89196/1989) was invented. Regarding (2), the present inventors invented a partially mullitized carrier (Japanese Patent Application No. 1983-49098) which improved the strength of the above-mentioned carrier. However, with respect to these above-mentioned carriers, sufficient consideration has not been given to the thermal shock resistance shown in (3). For this reason, researchers involved in the development of combustion catalysts are conducting intensive research with the goal of developing a carrier or catalyst that has all of the characteristics (1) to (3), but until now, this goal has not been fully achieved. has not been achieved.

Currently, the most effective method for achieving this goal is to obtain a catalyst by supporting an active ingredient on a thermal shock-resistant ceramic carrier by kneading, impregnation, or coating. Typical examples of thermal shock-resistant ceramics include cordierite, β-subodumen, and aluminum titanate. Among these, cordierite is widely used today as a catalyst carrier for automobile exhaust gas purification, but the melting point of this substance is 1460°C, and when using it for combustion, it meets the above-mentioned required characteristics (1). cannot be satisfied. In addition, the melting point of β-spodumene is 1423°C, which is also the above-mentioned required property (1).
) cannot be satisfied. The melting point of aluminum titanate is 1860°C, and if it is used as a combustion catalyst carrier, there is a high possibility that a catalyst satisfying all of the above-mentioned required properties (1) to (3) can be obtained.

In order to use aluminum titanate as a carrier for impregnation or coating, it is necessary to make the material porous. Generally, to obtain a porous fired body (carrier),
The following substances are often added to the raw clay or slurry.

(a) Organic combustible substances (b) Volatile substances (c) Gas-generating substances (Hiroshi Soki: Ceramic materials for furnace construction, pages 844 to 849). Of these, (a) is a method in which a large amount of organic binder, sawdust, graphite, etc. is added, and the porous material is obtained by decomposing and burning at a relatively high temperature of 200 to 400°C. For (b), a large amount of a low-melting point compound that volatilizes at a temperature around room temperature or a substance that sublimes easily is added in large quantities, and for (C), a temperature range slightly higher than (b) (60 to 100°C) is used. In this method, a large amount of a substance that decomposes into gaseous components, such as ammonium carbonate, is added. The methods for adding large amounts of substances (a) to (C) are all the same in principle, and the methods for adding large amounts of substances (a) to (C) are the same in principle;
This involves allowing a large amount of the substance C) to exist, and then scattering it to create a large number of cavities.

(Problems to be Solved by the Invention) However, as mentioned above, since the substance present in the molded body as a solid or liquid is scattered as a gas, the resulting carrier has a large pore diameter and has a high strength. often decreases. Therefore, it is necessary to add a sintering aid to the compact to improve its strength. for example,
In the case of aluminum titanate, in the method of adding the substance (a), approximately 5% of silica is added to the molding clay to obtain the strength required for practical use (Japanese Patent Publication No. 57-42563).
. The carrier obtained from this property is excellent as an automatic catalyst carrier used at 800 to 1000°C, but
If used at temperatures above 1200°C, the sintering aid and carrier component may react to form a low melting point compound, or sintering may progress during use, resulting in a decrease in pores and surface area, resulting in decreased activity. There was a problem that it decreased over time.

(Means for Solving the Problems) In order to solve the above problems, the method for producing a catalyst carrier of the present invention has an average particle diameter of 3 μm or more, preferably 10 to 30 μm.
By adding and mixing a sol or gel-like substance that can produce aluminum titanate by firing to aluminum titanate powder, shaping and firing, it is porous, thermally stable, and has sufficient strength. A catalyst carrier having the following properties is obtained.

In order to produce the carrier of the present invention, aluminum titanate powder having an average particle size of 3 μm or more is typically mixed with a sol or gel material containing aluminum as a main component and a sol or gel material containing titanium as a main component. After adding a gel-like substance to the powder, or adding a sol or gel-like substance containing aluminum titanate as a main component to the above powder, and forming it into a shape such as a honeycomb, round bar, or granule through wet kneading. , just need to be fired.

The aluminum titanate powder may be made from any raw material as long as it has an average particle size of 3 μm or more. Examples include raw materials such as γ-alumina and titania, or aluminum hydroxide and metatitanic acid slurry. Note that if a particle size of 1 μm or less is used, such as alumina sol and titania sol, the pulverizability becomes poor.

Any sol or gel-like substance to be added to aluminum titanate may be used as long as aluminum titanate is produced by firing. For example, examples of substances containing aluminum as a main component include alumina sol, boehmite gel, and a precipitated product obtained by adding aqueous ammonia to an aqueous solution of aluminum nitrate. Examples of substances containing titanium as a main component include orthotitanic acid sol (hereinafter referred to as titania sol), metatitanic acid slurry, and the like. As long as one of the above-mentioned sol or gel material is mainly composed of aluminum or titanium, the other one is not a sol or gel material. A carrier according to the present invention is obtained. That is, various combinations such as alumina sol and titania, γ-alumina and titania sol, aluminum hydroxide and metatitanic acid slurry, and boehmite gel and titania are possible. However, when α-alumina is used as an aluminum additive, the strength may decrease. In addition to the above-mentioned additives, the carrier of the present invention can also be obtained by using a sol-like substance in which ultrafine aluminum titanate powder is dispersed.

The compositional ratio of the aluminum-based and titanium-based additives is preferably such that the atomic ratio of aluminum:titanium is about 2:1, and when this ratio is used, all of the additives become aluminum titanate by firing.

The addition ratio of the above-mentioned additives to the aluminum titanate powder is preferably greater than O and within 3 Qwt% on a dry basis.

(Example) Hereinafter, the present invention will be explained in detail with reference to specific examples.

(Preparation example of aluminum titanate powder) 10 kg of hydraulic γ-alumina with an average particle size of 3 μm and 26.1 kg of metatitanate slurry (containing 3 Q w t% gold as titanium oxide) with an average particle size of 4 μm were mixed into 1007! After heating and kneading at 150°C for 3 hours using a kneader, the mixture was dried at 180°C for 10 hours, then heated to 1600°C over 4 hours, and fired at 1600°C for 2 hours. This fired product was pulverized with a hammer mill to obtain aluminum titanate powder having an average particle size of 17 μm. This powder is hereinafter referred to as raw material.

Example 1 4 kg of raw material was added with alumina sol (IQw as alumina)
After adding a mixture consisting of 400 g of titania sol (containing 3Qwt% titanium oxide) and 104 g of titania sol (containing 3Qwt% titanium oxide), a piston extruder was used to mold the diameter I.
A round bar molded product of Qmm was obtained.

After drying this molded body at 180°C for 1 hour, it was heated to 1400°C.
The aluminum titanate carrier was obtained by firing for 2 hours.

Example 2 A slurry prepared by adding 1.71 J of water to 4 kg of raw material was wet-pulverized using a starter ball mill.

At this time, the grinding time (residence time in the start ball mill) was set to 2.3 minutes to obtain aluminum titanate slurry with an average particle size of 3 μm. A mixture of 400 g of alumina sol and 104 g of titania sol was added to this slurry, and the volume was ff1.
After heating and kneading at 120° C. for 2 hours using a 5J kneader, the mixture was cooled to room temperature. This was formed into a tip rod with a diameter of 10 m using a piston extruder, and dried and fired in the same manner as in Example 1 to obtain an aluminum titanate support.

Example 3.4 The amount of alumina sol added in Example 1 was set to 4.0 pupil and 9.0 pupil.
An aluminum titanate support was obtained by the same procedure as in Example 1 except that the amount of titania sol added was changed to 1.0 kg and 2) 5 kg.

Example 5 The alumina sol in Example 3 was replaced with boehmite kel, and the amount added was 530 g. In addition to 1.0 kg of titania sol, 90 g of glacial acetic acid was added, and the same procedure as in Example 1 was followed to obtain an aluminum titanate support.

Example 6.7 The titania sol in Example 3 was replaced with metatitanic acid slurry and anatase titania with an average particle size of 3 μm, and the amounts added were 1.0 kg and 34 g, respectively, and titanic acid was added using the same procedure as in Example 3. An aluminum carrier was obtained.

Example 8 50g of hydroxymethylcellulose to 5kg of FM,
880 g of boehmite gel was added and thoroughly mixed in a dry method. To this mixed powder, 1.3 kg of titania sol and 110 g of glacial acetic acid were added and kneaded for 2 hours using a kneader with a capacity of 51 to obtain a clay for molding.

After that, this clay is molded into an outer diameter hole 3 using an extruder.
After forming into a honeycomb structure with a diameter of 5 inches, a cell diameter of 1.4, and a wall thickness of 0.41, it was dried at 20°C for 12 hours, 60°C for 3 hours, and 180°C for 1 hour to obtain a honeycomb-shaped dried body. I got it. This dried body was fired at 1600° C. for 2 hours to obtain a honeycomb carrier of aluminum titanate.

Example 9 Regarding the honeycomb carrier of Example 8, La-β-A120
After repeating the coating process six times by immersing it in 3 slurry (slurry concentration: 65%), it was fired at 800°C. This fired body was loaded with 1 wt % palladium by an impregnation method, and then fired at 1200° C. for 2 hours to obtain a honeycomb catalyst.

Example 10 The alumina sol in Example 1 was 40 g, the titania sol was 10.4 g, and the other procedures were the same as in Example 1.
Comparative Example 1 Aluminum titanate carrier obtained Comparative Example 1 The grinding time in the wet grinding using the start ball mill performed in Example 2 was 27.8 minutes, and the average particle size was 1.
A 7 μm aluminum titanate slurry was obtained.

The following procedure was carried out according to Example 2 to obtain an aluminum titanate support.

Comparative Example 2 An aluminum titanate support was obtained in the same manner as in Example 1 except that the amount of alumina sol added was 12.1 kg and the amount of titania sol added was 3.2 kg.

Comparative Example 3 5 kg of raw materials, 1 kg of hydroxymethylcellulose, 500 g of graphite with an average particle size of 1 μm, and kaolina l-5
After adding 00g of water and thoroughly mixing with a dry method, add 2.1g of water.
2 was added and kneaded for 2 hours using a kneader with a capacity of 51 to obtain a molding clay. The following procedure was carried out according to Example 8 to obtain a honeycomb carrier. Furthermore, a honeycomb catalyst was obtained by the same procedure as in Example 9.

(Test method) 1. The shrinkage rate of each carrier during firing was calculated from the dimensional difference before and after firing.

2) The water absorption rate of each carrier was calculated from the difference in weight before and after water absorption.

3. The bending strength of the round bar-shaped carrier was measured using a sample length of 50 m.

4. The longitudinal crushing strength of the honeycomb-shaped carrier is determined by measuring the sample length 501
Measured as a mu.

5. In order to evaluate the heat resistance of the honeycomb catalyst, a methane combustion test was conducted under the following conditions.

(1) Catalyst dimensions: 35 cranes x 50 cranes (2) Methane concentration = 4.7% (remainder is air) (3) Space velocity: 40.000 h-1 (4) Air preheating temperature: 300°C (5) Test time: lOOh Table 1 shows the firing time reduction ratio and the water absorption rate of the carriers of Examples 1 to 1O1 Comparative Example 1.2 and the carrier of Comparative Example 3 before catalysis. From the wood surface, it can be seen that the carrier of the present invention has a shrinkage rate of 1/10 to 1/2, which is smaller than that of the comparative example, and a water absorption rate of 1.7 to 5.4 times larger than that of the comparative example. It is highly porous and porous.

Table 2 in the margin below shows the strengths of the supports or catalysts of Examples 1 to 10 and Comparative Examples 1 to 3. From the wood surface results, it can be seen that the strength of the carrier according to the present invention or the catalyst produced using the present carrier is not significantly inferior to that of Comparative Examples 1 to 3 in which sintering has proceeded. Generally, it is said that the strength of the honeycomb carrier is preferably 100 kg/ctA or more, and the carrier of the present invention has a strength of 100 kg/ctA or more.
There is no problem at all.

Table 1 shows the results using the catalysts of Example 9 and Comparative Example 3.
These are the results of a heat resistance test using methane combustion. From this figure, it can be seen that the heat resistance, which was a problem with the conventional method (Comparative Example 3),
It can be seen that the problem can be solved by using the carrier according to the present invention.

(Effects of the Invention) As described above, according to the present invention, a porous aluminum titanate carrier with thermal shock resistance that exhibits thermally stable characteristics and has sufficient strength as required can be obtained. It will be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the results of a heat resistance test using methane combustion for a catalyst using a honeycomb carrier according to the present invention and a catalyst using a honeycomb carrier obtained by a conventional method. Agent Patent Attorney Takeshi Kawakita Long combustion duration (h)

Claims (3)

[Claims] (1) In a method for producing a catalyst carrier containing aluminum titanate as a main component, a sol or gel-like substance capable of producing aluminum titanate by firing is added to aluminum titanate powder having an average particle size of 3 μm or more. A method for producing a catalyst carrier containing aluminum titanate as a main component, which is characterized by kneading, shaping, and then sintering. (2) In the method for producing a catalyst carrier according to claim 1, the sol or gel substance added to the aluminum titanate powder is a sol or gel substance containing aluminum as the main component of the metal element, titanium titanium characterized by adding at least one kind of sol or gel-like substance out of a sol or gel-like substance whose main component is a metal element containing A method for producing a catalyst carrier whose main component is acid aluminum. (3) In the method for producing a catalyst carrier according to claim 1, the amount of the sol or gel substance to be added to the aluminum titanate powder is adjusted to the amount of alumina and/or titania and/or titanium added to the aluminum titanate powder. A method for producing a catalyst carrier containing aluminum titanate as a main component, characterized by adding more than 0 and 30 wt% or less as aluminum acid.