JPS62201644A - Production of catalyst and catalytic carrier - Google Patents

Abstract

PURPOSE:To enhance shock resistance, compressive strength and specific surface area by molding an aggregate composition from each specified amount of rehydrating alumina and cordierite and subjecting the composition to rehydrating treatment and thereafter sintering it at the specified temp. CONSTITUTION:The following aggregate composition is molded wherein it consists of 90-10wt% rehydrating alumina, 10-90wt% cordierite and total of rehydrating alumina and cordierite is at least >=50%. Then after subjecting this molded material to rehydrating treatment, it is calcined at 1,100-1,350 deg.C temp. to produce a catalytic carrier. As the above-mentioned rehydrating treatment of the molded material, a treating method in underwater at room temp. -100 deg.C or in steam at room temp. -150 deg.C can be adopted. The obtained carrier has the value of 5-100m<2>/g specific surface area and >=100kg/cm<2> compressive strength.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst having excellent thermal shock resistance and pressure resistance strength and a high specific surface area, and a method for producing a catalyst carrier.

In recent years, exhaust gas regulations from various industries have been tightened from the perspective of environmental conservation, and molded bodies made of transitional alumina such as activated alumina and alumina sol have a characteristic of having a high specific surface area compared to other inorganic molded bodies. It is widely used as a catalyst and catalyst carrier for denitrification, deodorization, and internal heat engines, but the molded bodies obtained from transition alumina have low thermal shock resistance and pressure resistance, and are not suitable for use as catalyst carriers for automobiles, for example. Items that require pressure resistance due to impact being applied to the carrier itself, or large temperature changes such as sudden heat generation due to catalytic oxidation reaction of unburned hydrocarbons and carbon oxides in exhaust gas, or sudden cooling due to engine stop. If this happens, the carrier will crack or break, rendering it unusable.

On the other hand, molded bodies made from low thermal expansion materials such as cordierite, subodumene, and mullite are used as catalysts or catalyst carriers in fields where thermal shock resistance and pressure resistance are required. The molded body generally has a low specific surface area of 1r+ (7 g or less), so if a high specific surface area is required, the surface of the molded body is coated with a substance having a high specific surface area such as activated alumina or alumina sol,
Although they are used as catalysts or catalyst carriers, these catalysts and catalyst carriers are expensive due to the complexity of the manufacturing process, and the coating layer tends to peel off during use, resulting in a decrease in activity.

Additionally, in recent years, honeycomb-shaped catalyst carriers with approximately 400 holes per square inch have become mainstream as catalysts or catalyst carriers for exhaust gas from internal heat engines due to stricter exhaust gas regulations and demands for more compact equipment. Further, a honeycomb-shaped catalyst carrier having a very small pore diameter of about 600 pores per square inch or more is being developed.

It is very difficult to uniformly coat this catalyst carrier with a very small pore size with an alumina layer, and the cost must also increase.

In view of this situation, the present inventors conducted intensive research to find a catalyst and catalyst support that have excellent thermal shock resistance, pressure resistance, and a high specific surface area. The present inventors have discovered that a catalyst or catalyst carrier that satisfies all of the above physical properties can be obtained by rehydrating an aggregate composition after molding and then sintering at a specific temperature, and have completed the present invention. .

That is, the present invention uses 90 to 10% by weight of rehydratable alumina.
, an aggregate composition consisting of 10 to 90% by weight of cordierite and a total of at least 50% by weight of rehydratable alumina and cordierite is molded, and after the molded body is rehydrated, it is The present invention provides a method for producing a catalyst and a catalyst carrier, characterized in that the catalyst is sintered at a temperature of 1350°C.

The method of the present invention will be explained in detail below.

The rehydratable alumina used in the method of the present invention is transitional alumina other than α-alumina obtained by thermally decomposing alumina hydrate, such as ρ-alumina and amorphous alumina, and industrially, for example, it can be obtained from a Bayer step. Alumina hydrates, such as alumina trihydrate, are brought into contact with hot gas at about 400 to 1200°C, usually for a fraction of a second to 10 seconds, or alumina hydrates are brought into contact with hot gas at about 250 to 900°C under reduced pressure. Approximately 0 can be obtained by heating and holding for 1 minute to 4 hours.
．． Examples include those having a loss on ignition of 5 to 15% by weight.

When looking at the physical properties of the rehydratable alumina used in the present invention, X-ray diffraction reveals that ρ-alumina and/or amorphous alumina are present in the rehydrating alumina at least 20 times, preferably at least 30 times. It is fine as long as it is done.

Rehydratable alumina is generally used with a particle size of about 50 μm or less, and the mixing ratio with cordierite is 10 to 90 μm.
%, preferably 30 to 70%.

If the mixing ratio of rehydratable alumina to cordierite is less than 10% by weight, no improvement in specific surface area is observed, while if it exceeds 90% by weight, no improvement in compressive strength or thermal shock resistance is observed. .

The cordierite used in the present invention may be any cordierite as long as the main component of the crystalline phase is cordierite. Examples include those having a chemical composition range of 44 to 51% by weight of silica, 34 to 48% by weight of alumina, and 10 to 18% by weight of magnesia with respect to the light composition point, and the mixing ratio with rehydratable alumina is 9O-1.
o weight percent, preferably 70 to 30 weight percent.

The amount of cordierite added to rehydratable alumina is 1
If it is less than 0% by weight, it will not contribute to reducing the coefficient of thermal expansion and sufficient thermal shock resistance will not be obtained, while if it exceeds 90% by weight, the specific surface area will be small and sufficient catalytic activity will not be obtained. .

The particle size of cordierite is such that it provides easy sinterability at low temperatures and does not significantly reduce the amount of macropores when formed into a molded body. ~0.1μ, preferably 30~0.5μ is used.

When carrying out the method of the present invention, rehydratable alumina and cordierite form an aggregate composition within the above composition range, which is then shaped into a catalyst or catalyst support through rehydration treatment and sintering treatment. Aggregates other than rehydratable alumina and cordierite can be used as long as the physical properties targeted by the invention are not impaired.

These aggregates are not particularly limited as long as they are aggregates used in the field of photocatalyst carriers, but α
−Alumina, silica, alumina hydrate, clay, talc,
bentonite, diatomaceous earth, zeolite, subodumene, titania, zirconia, silica sol, alumina sol,
Examples include mullite, activated carbon, etc., and the content thereof in the aggregate composition is less than 50% by weight, preferably less than 30 times, more preferably 2
Used at less than 0% by weight.

Furthermore, as necessary, for the purpose of increasing the specific surface area and pore volume of the (catalyst or) catalyst carrier, organic crystalline cellulose and synthetic resins are added, inorganic fibers are added to increase strength, and catalyst components are added after the carrier is formed. Catalyst components may be added for the purpose of omitting the supporting step or for the purpose of strengthening the catalytic ability. It may be prepared accordingly.

In the practice of this invention, the rehydratable alumina is partially or completely coated with an anti-rehydration agent prior to contact with water or water-containing materials.

When the rehydratable alumina in the aggregate composition is kneaded directly with water or water-containing substances, a rehydration reaction occurs during this process.

For this reason, even if a rehydration treatment is performed after molding, desired strength cannot be imparted.

If the rehydration inhibitor can suppress the rehydration of such rehydratable alumina, specifically, in the case of organic substances that are solid at room temperature, the solubility in water at room temperature is about 20% by weight or less. %, preferably about 10% by weight or less.

Further, in the case of organic substances that are liquid at room temperature, examples thereof include those whose mutual solubility in water at room temperature is at most 50% or less, preferably 25% or less.

More specifically, caproic acid, palmitic acid, oleic acid, glycolic acid, caprylic acid, stearic acid, salicylic acid, trimethylacetic acid, lauric acid, cerotic acid, cinnamic acid, malonic acid, myristic acid, sebacic acid, benzoic acid,
Fatty acids and their salts such as maleic anhydride and wax, or sulfonic acids, phosphoric acid substituted products thereof, alcohols such as t-butyl alcohol, lauryl alcohol, cetyl alcohol, stearyl alcohol, cyclohexanol, menthol, cholesterin, and naphthol, Amines such as laurylamine, tetramethylenediamine, jetanolamine, diphenylamine, alkanes such as n-heptadecane, n-octadecane, n-nonadecane, n-eicosane, aromatic compounds such as naphthalene, diphenyl, anthcene, starch, casein, cellulose and its derivatives,
Natural polymer compounds such as alginate, synthetic polymer compounds such as polyethylene, polyvinyl alcohol, polyvinyl chloride, polypropylene, sodium polyacrylate, polybutadiene, isoprene rubber, urethane resin, liquid paraffin, soybean oil, white squeeze oil, light oil , paraffins such as kerosene,
Examples include carboxylic acids such as caprylic acid and pelargonic acid, and aromatic hydrocarbons such as benzene, toluene, xylene, and cumene.

These rehydration inhibitors are added and mixed in such a proportion that they can partially or completely cover the rehydrating alumina surface.
Coating methods include adding and mixing directly to the powder, or kneading to coat the powder, or if the rehydration inhibitor is a solid substance that is difficult to coat directly on the powder, an appropriate coating method such as alcohol or ether may be used. The anti-rehydration agent is dissolved in a solvent in advance and then coated, or in the case of a liquid, it is directly immersed in the anti-rehydration agent, or the liquid is vaporized and coated on the powder surface. There are various methods such as

The amount of rehydration inhibitor added depends on the aggregate particle size distribution, composition, rehydration treatment conditions, etc., but is usually in the range of 0.01 to 30% by weight based on rehydration alumina. used in

If the amount added is less than 0.01% by weight, the rehydration prevention effect will not be sufficient, and the desired bonding strength will not be achieved by rehydration treatment after molding into the desired molded article.

The molding method in the method of the present invention can be carried out by any method that is generally used for manufacturing catalyst carriers, and includes dish granulation method, extrusion molding method, pressing method, casting method, etc. Naturally, the form of the molded product is not limited.

Further, operations up to forming a molded body, such as mixing of aggregates, kneading method, added binder, molding aid, etc., may be carried out by known methods for each molding method.

The molded body after molding is subjected to a rehydration treatment.

This treatment can also be carried out using a method already known for the production of activated alumina carriers, and can be carried out in water at room temperature to 100°C or in water at room temperature to 100°C.
The test is carried out in water vapor at 50°C or in a water vapor-containing gas for 1 minute to 1 week.

It is also possible to rehydrate by leaving it in a closed container at room temperature and pressure for a long time.

The molded body rehydrated in this manner is then sintered at a temperature of 1100 to 1350°C after removing adhering moisture by a known method such as natural drying, hot air drying, or high frequency drying.

If the sintering temperature is less than 1100℃, sufficient pressure resistance,
If the temperature exceeds 1350° C., the specific surface area will drop significantly, which is not preferable.

The sintering time varies depending on the sintering temperature, the constituent composition of the molded body, and the physical properties of the final molded body, but it is usually sintered for 30 minutes to 24 hours.

The molded product thus obtained has a specific surface area of 5 to 100 r.
rr/g, compressive strength 100kt/cd or more, thermal shock resistance temperature 500℃ or more, and the alumina component after sintering is mainly r-5θ.
- It has physical properties consisting of alumina.

Although it is not clear why the molded product obtained in the present invention is able to improve compressive strength and specific surface area more than the arithmetic average of the mixing ratio of rehydratable alumina and cordierite, Perhaps the surface of the fine alumina particles activated by the rehydration reaction is dragged by the shrinkage of the cordierite particles due to sintering, increasing their contact surface area and starting sintering at a previously unimaginable low temperature, or the cordierite particles Sintering is promoted by the chemical reaction with the material, and the strength is significantly increased due to the interparticle bonds formed, and the thermal shock resistance is also increased depending on the decrease in the apparent coefficient of thermal expansion and the increase in strength. considered to be a thing.

Furthermore, it is also assumed that the presence of cordierite suppresses the alpha conversion of the rehydratable alumina particles, and that the specific surface area decreases little despite the progress of sintering.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples.

In the present invention, thermal shock resistance, compressive strength, and specific surface area were measured by the following methods.

Thermal shock resistance: The highest temperature at which cracks did not occur was taken out of a furnace kept at a high temperature and placed on a brick at room temperature, which was defined as the thermal shock resistance temperature.

Compressive strength: 2fl/ using an Instron strength tester
Based on the jBET method, where the compressive strength is the average value of about 10 samples obtained at a strain rate of min.

Example 1 50 parts by weight of activated alumina powder containing 30 parts by weight of ρ-alumina with an average particle size of 6 μ obtained by baking gibbsite-type alumina hydrate was mixed with ρ-alumina during kneading raw material aggregate and in an extrusion molding machine. 50 parts by weight of cordierite powder with an average particle size of 3μ, to which 2 parts by weight of wax was added for the purpose of preventing the rehydration reaction from occurring (hereinafter referred to as a rehydration inhibitor);
Furthermore, 4.5 parts by weight of methylcellulose as an extrusion aid;
A mixture to which 32 parts by weight of water was added was kneaded for 30 minutes using a screw kneader and then fed to a screw extruder with a wall thickness of 0.
A honeycomb-shaped catalyst carrier measuring approximately 95 mm in diameter and 100 mm in length and having a square near unit with a length of 25 m and a side of 1 side was molded.

Next, this carrier was rehydrated in warm water at 90°C for 24 hours, and then heated to 1000°C at 100°C/hour, 120°C.
The temperature was increased to 0°C at a rate of 30°C/hour, and then further heated to 120°C.
It was baked at 0°C for 3 hours.

The physical properties of the honeycomb-shaped catalyst carrier obtained in this way were first evaluated.
Shown in the table.

For comparison, the mixing ratio of the above activated alumina powder and cordierite powder was changed to (95 parts by weight of activated alumina powder, 5 parts by weight of cordierite powder), (5 parts by weight of activated alumina powder, and 95 parts by weight of cordierite powder). A honeycomb-shaped catalyst carrier was manufactured in the same manner as in Example 1 above.

The physical properties at this time are shown in Table 1.

Table 1 Example 2 2.8 parts by weight of wax as a rehydration inhibitor was added to 70 parts by weight of the same activated alumina powder as in Example 1, and the center particle size (
30 parts by weight of cordierite powder (50% particle size) 3 μm, 4.7 parts by weight of methylcellulose as an extrusion aid, and 3 parts by weight of water.
Using a screw kneader, the mixture containing 5 parts by weight of
After kneading for a minute, a honeycomb catalyst carrier was molded in the same manner as in Example 1.

This carrier was then rehydrated under the same conditions as in Example 1,
Next, the temperature was raised to 1220° C. under the same temperature raising conditions as in Example 1, and firing was performed at the same temperature for 2 hours.

The honeycomb-shaped catalyst carrier obtained in this way has a bulk density of 1
．． 68 g/cm", specific surface area 45 rrf/g, compressive strength 320 kg/ai, and thermal shock resistance temperature 700°C.

Example 3 501 φ x 40 dragon φ x 300 ■■ using the same method as Example 1
1 of tubular catalyst carriers were molded.

Next, this carrier was rehydrated under the same conditions as in Example 1, and then the temperature was raised to 1250° C. for 3 hours.

The tubular catalyst carrier obtained in this way has a bulk density of 1
．． 90 g/cta", specific surface area 20 rrr/g,
Pressure strength 600kir/cd (tube axial direction) 55k
g/ad (tube axis perpendicular direction), thermal shock resistance temperature 105
It was 0°C.

Comparative Example 1 50 parts by weight of cordierite powder with an average particle size of 3 μm was added to 50 parts by weight of calcined alumina powder mainly composed of γ-alumina with an average particle size of 8 μm obtained by baking boehmite type alumina hydrate at 600°C. Further, a mixture containing 4 parts by weight of methylcellulose and 30 parts by weight of water as extrusion aids was kneaded for 30 minutes using a screw kneader, and then fed to a screw extruder to form the same honeycomb-shaped catalyst carrier as in Example 1.

This carrier was then sintered under the same conditions as in Example 1.

The honeycomb-shaped catalyst carrier obtained in this way has a bulk density of 1
-5 g/cm", specific surface area of 15 rrr/g, compressive strength of 120 kg/cd, and thermal shock resistance of 300°C.

Comparative Example 2 A honeycomb-shaped catalyst carrier molded under the same conditions as in Example 1 was fired under the same conditions as in Example 1 without performing rehydration treatment.

The honeycomb-shaped catalyst carrier obtained in this way has a bulk density of 1
．． 55 g/cm! , specific surface area specific surface area 20 resistance/strength 150 kg/aJ, and thermal shock resistance temperature 350°C.

Comparative Example 3 A honeycomb-shaped catalyst carrier that had been molded and rehydrated under the same conditions as Example 1 was heated to 1050 ml under the same conditions as Example 1.
It was baked at ℃ for 5 hours.

The honeycomb-shaped catalyst carrier obtained in this way has a bulk density of 1
．． 40 g/cm", specific surface area 60 n?/g, compressive strength 80 kg/cd, and thermal shock resistance temperature 200°C.

Comparative Example 4 The honeycomb-shaped catalyst carrier of Comparative Example 3 was fired at 1400° C. for 1 hour.

The honeycomb-shaped catalyst carrier obtained in this way has a bulk density of 2
．． Q g/cm", specific surface area of 1 rrr/g or more, and pressure resistance of 390 kg/-.

Example 4 50 parts by weight of the same activated alumina powder and 50 parts by weight of cordierite powder as in Example 1 were mixed, 28 parts by weight of water was further added, and a spherical catalyst carrier with a diameter of 4 to 6 cranes was molded using a dish-type granulator. .

Next, this carrier was preliminarily rehydrated at room temperature (20°C) for 24 hours, and then rehydrated in warm water at 90°C for 24 hours.

Firing up to 1000℃ 100℃/Hr up to 1200℃ 5
The temperature was raised at a temperature increase rate of 0°C/Hr, and further baked at 1200°C for 3 hours.

The spherical catalyst carrier obtained in this way has a bulk density of 1.85.
g/c+s3, specific surface area 30bo/g, pressure resistance 90
kg (5 mφ particle size product).

Comparative Example 5 35 parts by weight of water was added to 100 parts by weight of the same activated alumina powder as in Example 1.
A spherical catalyst carrier was formed by the same method and conditions as in Example 4, rehydrated, and then fired.

The spherical catalyst carrier obtained in this way has a bulk density of 1.40.
g/cm'', specific surface area 8n?/g, pressure resistance 10k
g (5×1φ particle size product).

Example 5 1.6 parts by weight of wax was added as a rehydration inhibitor to 40 parts by weight of the same activated alumina powder as in Example 1 to give an average particle size of 3 μm.
30 parts by weight of cordierite powder, α with an average particle size of 6μ
- A mixture of 30 parts by weight of alumina, 4.4 parts by weight of methyl cellulose and 30 parts by weight of water as extrusion aids was kneaded for 30 minutes using a screw kneader, and then a honeycomb-shaped catalyst carrier was formed in the same manner as in Example 1.

Next, this carrier was rehydrated under the same conditions as in Example 1, and then
Subsequently, the temperature was raised to 1200° C. for 3 hours.

The honeycomb-shaped catalyst carrier obtained in this way has a bulk density of 1
．． 90 g/cm2. The specific surface area was 25 rrr/g, the compressive strength was 280 kg/d, and the thermal shock resistance temperature was 65 (1).

Claims (1)

[Claims] 1) Molding an aggregate composition consisting of 90 to 10% by weight of rehydratable alumina and 10 to 90% by weight of cordierite, in which the total of rehydratable alumina and cordierite is at least 50% by weight, and the molding. After rehydrating the body, use this 1
A method for producing a catalyst and a catalyst carrier, comprising sintering at a temperature of 100 to 1350°C.