JPH06134305A - Heat resistant catalyst and method for using the same - Google Patents

Abstract

PURPOSE:To prevent the flocculation of a catalytically active component and the reduction of the specific surface area during a reaction at a high temp. by carrying the catalytically active component on a carrier based on a prescribed multiple oxide consisting of lanthanum and beta-alumina. CONSTITUTION:A catalytically active component is carried on a carrier based on a multiple oxide consisting of lanthanum and beta-alumina represented by 11-14Al2O3.La2O3. In this case, the carrier is preferably made of only aluminum- lanthanum multiple oxide. Even when the resulting catalyst is used at a high temp. of >=1,000 deg.C, the flocculation of the catalytically active component by heat is inhibited and the catalytic performance is stabilized. The surface of the multiple oxide may be coated with ceramic. In the case where the catalytically active component is one or more kinds of group VIII elements of the periodic table, the resulting catalyst can be used as a heat resistant catalyst for steam reforming.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-resistant catalyst which can be stably used in a temperature range of 1500 ° C. or lower, and a method of using the same.

The catalysts of the invention are particularly suitable for use at temperatures above 800 ° C.

[0003]

BACKGROUND OF THE INVENTION Organic solvent or odorless oxidation treatment, automobile exhaust gas treatment, high temperature steam reforming, high temperature denitration and the like are known as methods for carrying out a reaction at a high temperature using a catalyst.
Recently, there has been a movement to apply the catalytic combustion technology that makes use of the above features to large-capacity boilers, gas turbines, gas turbines for aircraft, and the like.

In these treatment methods, the reaction temperature is about 60.
0 ° C or higher, depending on conditions 1400 to 1500 ° C
Reach up to. Therefore, even in such a high temperature range, a catalyst having a small decrease in catalytic activity and high thermal stability is required.

Conventionally, the catalysts used as high temperature catalysts include alumina, silica, silica-alumina, etc. as a carrier on which a noble metal or a base metal component is supported, or zirconia, aluminum titanate, silicon nitride, etc. The ceramic material of (1) and the surface of which is coated with activated alumina or the like to carry a noble metal component have been used.

[0006] However, these catalysts have a drawback that the activity of the catalyst is remarkably deteriorated at a temperature of 800 ° C or higher because of a phase transition of the carrier, a decrease in specific surface area due to crystal growth, and a decrease in surface area due to aggregation of active components. was there. The catalyst using the above-mentioned ceramic material has a high heat resistance by itself, but has a drawback that the catalyst component cannot be effectively utilized because the heat resistance of the coating material is low.

[0007]

OBJECT OF THE INVENTION The object of the present invention is to improve the above-mentioned drawbacks of the prior art and to suppress the aggregation of the active ingredient and the reduction of the specific surface area of the carrier even under the reaction conditions of high temperature, and such a heat-resistant catalyst. It is to provide a method of using the catalyst.

[0008]

SUMMARY OF THE INVENTION γ or η alumina has a high specific surface area and is often used as a carrier or a coating material. However, at 700 ° C. or higher, especially at 900 ° C. or higher, the phase transition to α alumina and the growth of crystal grain size occur. As a result, the specific surface area decreases, and along with this, the particles of the catalytically active components, such as precious metals and base metals, agglomerate and the catalytic activity decreases.

The present inventors have conducted various studies to improve the above thermal instability of alumina and prevent the particles of the supported catalyst component from aggregating. As a result, lanthanum was added to aluminum. Lanthanum β-alumina (11
_{~14Al 2 O 3 · La 2 O} 3) a noble metal as a catalyst active component on a carrier, the catalyst was such a combined base metal is found to be very effective.

The present invention is a heat-resistant catalyst comprising a carrier having a composite oxide of aluminum and lanthanum as a main component and a catalytically active component supported on the carrier.

Although lanthanum β-alumina is most preferable as the composite oxide of aluminum and lanthanum, it is not limited thereto.

Further, the carrier is most preferably composed only of a composite oxide of aluminum and lanthanum, but other carrier components may be contained.

Lanthanum β-alumina is 11-14 Al ₂
O is ₃ · La consisting ₂ O ₃ compound. This composite oxide is produced by firing a mixture of these hydroxides or oxides or a compound that gives an oxide by heat treatment at a temperature of at least 800 ° C. or higher.

A catalyst in which a catalytically active component is supported on a carrier composed of a composite oxide of aluminum and lanthanum is 1000 ° C.
Even when used at the above-mentioned high temperature, aggregation of the catalytically active component due to heat hardly occurs, and stable catalytic performance can be maintained. The reason is that the composite oxide of aluminum and lanthanum and the catalytically active component exhibit strong interaction.

Although lanthanum β-alumina itself has good heat resistance and a large specific surface area, other than that, this compound has an effect of suppressing the phase transition from activated alumina to α-alumina and crystal growth, which is detailed in detail. It became clear from the results of diffraction and electron microscopy. Therefore, not only lanthanum β-alumina but also an alumina carrier containing this composite oxide as a main component is excellent as a catalyst carrier used at high temperature.

It was revealed from the N ₂ adsorption experiment that the carrier made of a composite oxide of aluminum and lanthanum showed a small decrease in the specific surface area under high temperature conditions. Further, the dispersion state of palladium, which is the catalyst component supported on the above composite oxide, was examined by an electron microscope and a carbon monoxide chemisorption method, and it was found that the dispersion state was high even after firing at 1200 ° C.

The composite oxide of aluminum and lanthanum may be coated or composited with other ceramics. For example, α-alumina, titania, zirconia, magnesia,
It can also be used in addition to heat-resistant oxides such as cordierite, mullite and aluminum titanate. It may be coated or mixed with a material other than oxides such as silicon carbide and silicon nitride. When complexed, the amount of the complex oxide of aluminum and lanthanum is preferably 50% or more of the total weight of the carrier.

The firing temperature for forming the composite oxide of aluminum and lanthanum is 800 ° C. or higher, preferably 90.
It is 0 ° C or higher and 1500 ° C or lower. When the firing temperature is 800 ° C. or lower, lanthanum β-alumina is not formed, and when it exceeds 1500 ° C., sintering proceeds, which is not preferable.

Powders containing the above complex oxide have various shapes,
For example, it can be used after being formed into a spherical shape, a cylindrical shape, a ring shape, a honeycomb shape, or the like. Further, inorganic heat-resistant carriers formed into various shapes, for example, ceramics such as mullite, cordierite, α-alumina, zircon, aluminum titanate, silicon carbide and silicon nitride are coated with a slurry of powder containing the above complex oxide. It can also be used. The amount of the above composite oxide supported on the inorganic heat resistant carrier is 5% or more, preferably 5 to 5% of the total weight of the carrier.
It is 30% by weight.

As a method for producing the above-mentioned aluminum-lanthanum composite oxide, a usual precipitation method, a deposition method, a kneading method, an impregnation method or the like can be applied and is not particularly limited. As an example, a method of adding an alkali to a mixed aqueous solution of an aluminum salt and a lanthanum salt to form a dense coprecipitate, and heating and calcining this, intimately mixing alumina and / or alumina sol with lanthanum oxide and / or lanthanum hydroxide. Then, a method of heating and baking this, a method of impregnating alumina with a solution of a lanthanum salt, and heating and baking this are mentioned.

If an alkali is added to an aqueous solution containing alumina and lanthanum to coprecipitate an intimate mixture of both, and then calcination is carried out, a composite oxide of aluminum and lanthanum can be obtained even at a relatively low calcination temperature. is there.

As the aluminum raw material, soluble salts such as nitrates, sulfates and chlorides, organic salts such as alkoxides, hydroxides and oxides can be used. On the other hand, as the lanthanum raw material, soluble salts such as nitrates, chlorides and oxalates, hydroxides and oxides can be used. Mixed rare earths containing lanthanum can also be used.

The catalytically active components are finally supported in the form of metals or oxides.

As a method for supporting the catalytically active component, a commonly used method such as an impregnation method or a kneading method can be applied. As a raw material of the catalytically active component, an inorganic salt or a complex salt can be used.

The catalyst of the present invention can be used for combustion reaction of hydrogen or generalized carbon or hydrocarbons, odor removal, denitration reaction, high temperature steam reforming reaction, automobile exhaust gas purification and the like.

When the catalyst of the present invention is used in a combustion reaction of a gas containing at least one of hydrogen, carbon monoxide and hydrocarbons as a combustion component, it is used as a catalyst active component in Periodic Table VI.
Group II, manganese, chromium, zirconium, rare earth elements,
It is desirable to use tin, zinc, copper, magnesium, barium, strontium and calcium. Hydrocarbons used in such combustion reaction include ethane, propane, butane, pentane and the like. The reaction temperature varies depending on the type of gas, but a wide temperature range of room temperature to 1500 ° C can be applied. When carrying out the combustion reaction, the gas is brought into contact with the catalyst in the presence of a gas containing oxygen. When the hydrocarbon is methane, the reaction temperature is particularly preferably 400 to 1000 ° C., and it is desirable to use a white metal metal as the catalytically active component.

When the catalyst of the present invention is used to purify exhaust gas of an internal combustion engine such as automobile exhaust gas, it is used as a catalytically active component in Group VIII of the periodic table, manganese, chromium, zirconium, rare earth elements, tin and zinc. , Copper, magnesium,
At least one of barium, strontium and calcium is used to bring the exhaust gas and oxygen into contact with the catalyst at a reaction temperature of 150 to 1500 ° C. It is particularly desirable to use a metal selected from Group VIII of the Periodic Table as the catalytically active component.

By doing so, it is possible to oxidize carbon monoxide and hydrocarbons in the exhaust gas and convert nitrogen oxides into nitrogen and water to render them harmless.

When the catalyst of the present invention is used for steam reforming of hydrocarbons, it is used as a catalytically active component in Periodic Table No. VIII.
At least one selected from the group consisting of alkali metals and alkaline earth metals is used to carry out a reaction in the temperature range of 400 to 1500 ° C. to produce a gas composed of hydrogen and carbon monoxide. As the catalytically active component, it is desirable to use Group VIII of the Periodic Table, especially nickel, or a mixture of nickel and cobalt.

When the catalyst of the present invention is used for the reduction reaction of nitrogen oxides in the exhaust gas of boilers, gas turbines, etc., ammonia is used as a reducing agent, and the amount is 500 to 150.
The reaction is carried out at a temperature of 0 ° C. As the catalytically active component, at least one selected from Group VIII of the Periodic Table, alkaline earth metals, titanium, zirconium, vanadium, rare earth elements, Va group, VIa group, manganese, zinc, aluminum, tin and lead is used. Is desirable.

These are finally supported in the oxide form. Among the catalytically active components, at least one of tungsten, vanadium, titanium, tin, cerium, iron, nickel and cobalt is particularly preferable.

When the catalyst of the present invention is used in a methanation reaction, as a catalytically active component, Group VIII of the periodic table, zinc,
At least one selected from chromium, vanadium and cerium may be used, and the carbon monoxide-containing gas and hydrogen may be contacted with the catalyst at a temperature of 250 to 400 ° C. As the catalytically active component, it is particularly desirable to use a metal selected from Group VIII of the Periodic Table, especially nickel.

When the catalyst of the present invention is used in the dehydrogenation reaction of hydrocarbons, chromium, zinc, and
At least one of vanadium, copper, tin, iron, nickel and cobalt is used, and hydrocarbons are brought into contact with the catalyst at a temperature of room temperature or higher and 1500 ° C. or lower. When the hydrocarbon is methanol, it is desirable to use at least one of copper and zinc as the catalytically active component. The reaction temperature is preferably 300 to 1000 ° C.

[0034]

The contents of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 375.1 g of aluminum nitrate and 228 g of lanthanum nitrate
Is dissolved in 1 liter of distilled water (Al / La = 95/5
Atomic ratio). While stirring this solution, 3N aqueous ammonia was added dropwise to neutralize the solution to pH 7.5. The coprecipitate of aluminum and lanthanum obtained was thoroughly washed with water, dried, and then pulverized 1
Bake at 000 ° C. for 5 hours. The obtained powder was formed into a columnar shape having a diameter of 3 mm and a length of 3 mm by a press molding machine to obtain a carrier.

On the other hand, a comparative carrier made of only alumina was prepared in the same manner as above except that lanthanum nitrate was not added.

Each of the two types of carriers obtained by the above method was impregnated with a palladium nitrate solution as vanadium in an amount of 1% by weight, dried at 120 ° C. for about 5 hours, and then calcined at 1200 ° C. for 3 hours. The catalyst of Example 1 and the catalyst of Comparative Example 1 were prepared and the performance of the methane combustion reaction was evaluated. A gas having the following composition is circulated at a space velocity of 25,000 h ^-1 ,
A 30-hour continuous test was performed.

Gas composition Methane: 3% Air: Balance The reaction gas was preheated to 550 ° C. in this experiment. When the reaction rate of methane reaches 90% or more, the temperature of the catalyst layer reaches about 1200 ° C., so that the durability of the catalyst at high temperature can be evaluated. The experimental results are shown in Table 1.

It can be seen from Table 1 that the catalyst according to this example is suitable for catalytic combustion reaction at high temperature.

[0040]

[Table 1]

The specific surface area of the catalyst of Example 1 and the catalyst of Comparative Example 2 were measured after the activity was measured for 30 hours.
m ² / g, and the latter was 4 m ² / g. In addition, the surface area of palladium dispersed on the carrier was measured. As a result, the catalyst of Example 1 was 78 m ² / g-Pd, while the catalyst of Comparative Example 1 was 20 m ² / g-Pd. Thus, it can be seen that the catalyst of Example 1 has a better specific surface area and a dispersed state of Pd than the catalyst of Comparative Example 1, and is excellent as a heat resistant catalyst.

Example 2 3750 g of aluminum nitrate and 480 g of lanthanum nitrate were dissolved in 10 liters of distilled water. Thereafter, 25 liters of distilled water of 1 kg of 800 ° C. powder obtained in the same manner as in Example 1 was added, and the mixture was pulverized by a vibration mill until the average particle size of the powder became about 1 μm to prepare a slurry-like immersion liquid. . A honeycomb structure made of a commercially available cordierite base material (diameter 90 mm, length 75 mm) was immersed in this immersion liquid, then taken out of the immersion liquid, blown with compressed air to remove excess liquid, and dried at 120 ° C. After that, heat treatment was performed at 500 ° C. for 1 hour. This operation was repeated, and finally firing was performed at 1000 ° C. for 2 hours. The honeycomb structure thus obtained has a weight of 18.7% by weight.
Had a layer of complex oxide. Next, the obtained honeycomb structure was immersed in an aqueous solution of chloroplatinic acid and rhodium chloride, dried at 120 ° C, and reduced in a hydrogen stream at 600 ° C. The catalyst had 1.5% by weight platinum and 0.4% by weight rhodium.

This catalyst was used for oxidation of automobile exhaust gas. Ordinary car engine (1800cc class)
It was used as a catalytic converter in a vehicle and the running test was conducted for 10,000 km. As a result, CO mode was 1.0 g / km and HC was 0.10 in 10 mode.
It was 19 g / Km. From this result, it is understood that the heat-resistant catalyst according to the present invention can be used for exhaust gas treatment of an internal combustion engine and maintains stable performance in high temperature reaction.

Example 3 In this example, an example in which the heat resistant catalyst according to the present invention is used for a high temperature steam reforming reaction of hydrocarbon will be described.

The carrier 100 according to the present invention shown in Example 1
impregnated with nickel nitrate aqueous solution and dried at 120 ° C.
It was baked at 900 ° C. for 2 hours. The catalyst thus obtained contained 15% by weight of nickel in terms of NiO.

The catalyst prepared by the above method was filled in a reaction tube and reduced in an H ₂ stream at 600 ° C. for 2 hours. In the reaction, the catalyst layer inlet temperature is 580 to 600 ° C., and the catalyst layer outlet temperature is 8
The steam reforming reaction of n-butane was carried out at a pressure of 15 kg / cm ² while maintaining the temperature at 50 to 900 ° C. Water vapor / carbon (molar ratio) = 30 and space velocity 3000 h ⁻¹ . 100
As a result of a continuous test of time, the reaction rate of n-butane was 99.9.
% Or more was maintained, and after the reaction, almost no carbon deposition was observed in the catalyst layer. The reaction product gas is H ₂ , CO, C
O ₂ and CH ₄ , and the production of these was present in a proportion almost equal to the equilibrium composition under the temperature conditions at the catalyst layer outlet.

As is clear from the results of this example, the heat-resistant catalyst of the present invention exhibits excellent performance even in high temperature steam reforming reaction.

Example 4 In this example, an example of using the heat-resistant catalyst according to the present invention for high temperature denitration reaction will be described.

50 g of powder of the complex oxide before molding prepared by the same method as in Example 1 was sufficiently kneaded with 500 g of metatitanic acid slurry (150 g as TiO ₂ ) by a kneader. After that, it is dried at 150 ℃, crushed to 400
Bake at 4 ° C for 4 hours. The obtained powder is molded into a cylindrical shape having a diameter of 3 mm and a thickness of 3 mm using a press molding machine, and then immersed in an aqueous solution of ammonium tungstate in hydrogen peroxide. Then, it is calcined at 600 ° C. for 2 hours to obtain a catalyst. The catalyst thus obtained contains 5% by weight of tungsten oxide.

The reaction uses a gas having the following composition and a space velocity of 5
It was carried out for 100 hours under the conditions of 000 h ⁻¹ and reaction temperature of 600 ° C.

Reaction gas composition NOx 200ppm NH ₃ 200ppm O ₂ 3% H ₂ O 10% N ₂ balance NOx removal rate is 94.8% at the initial stage and 94.% after 100 hours.
It was 4%. From the above results, the catalyst according to the present invention exhibits excellent performance against high temperature denitration reaction. Example 5 In this example, an example used as a catalyst for a CO methanation reaction will be described.

Each of the two types of carriers obtained in Example 1 was impregnated with nickel nitrate, calcined at 500 ° C., further impregnated with ruthenium chloride, and calcined at 1000 ° C. to prepare a catalyst. This catalyst contains NiO 30% and Ru 3%. The reaction tube was filled with this catalyst, and CO 5%, H ₂ 1
A gas of 7% and N ₂ residue was introduced so that SV was 100,000 h ^−1, and a methanation reaction was carried out at a reaction temperature of 350 ° C. As a result, it was found that the CO methanation yield of the catalyst of this example was about 15 times that of the catalyst of the comparative example. As described above, it is understood that the catalyst of the present invention is very effective not only at high temperatures but also at relatively low temperatures.

Example 6 In this example, the dehydrogenation reaction of methanol was examined.

The two types of carriers obtained in Example 1 are impregnated with a copper nitrate and zinc nitrate solution, dried and calcined at 1000 ° C. The contents of Cu and Zn are 20% by weight and 10%, respectively.
% By weight. The reaction tube is filled with these catalysts, and 800
After the temperature was raised to ℃, methanol was introduced and dehydrogenation reaction was carried out to produce formalin. The conversion of methanol was 9
It was 8% or more, and the selectivity for formalin was about 5 times that of the conventional one.

[0055]

As described above, according to the present invention, 15
It is possible to obtain a heat-resistant catalyst having excellent activity in a high temperature range of 00 ° C. or lower.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B01J 23/30 A 8017-4G 23/56 301 M 8017-4G A 8017-4G 23/76 M 8017 -4G 23/80 X 8017-4G Z 8017-4G 23/89 X 8017-4G 32/00 C01B 3/40 C07C 1/04 9280-4H 1/12 9280-4H 4/06 9280-4H 9/04 9280 -4H 47/052 7457-4H F23J 15/00 Z 7367-3K H 7367-3K // C07B 61/00 300 (72) Inventor Mamoru Mizumoto 3-1-1, Saiwaicho, Hitachi City, Ibaraki Stock Company Hitachi, Ltd., Hitachi Research Laboratory (72) Inventor, Shinpei Matsuda 3-1-1, Saiwaicho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd., Hitachi Research Laboratory

Claims (12)

[Claims] The method according to claim 1] 11~14Al ₂ O ₃ · La ₂ O made of lanthanum β-alumina represented by ₃ composite oxide support mainly, heat resistance reduction, characterized in that supporting a catalyst active component Reaction catalyst. 2. The heat-resistant reduction reaction catalyst according to claim 1, wherein the carrier is substantially composed of the composite oxide. 3. A heat-resistant reduction reaction catalyst according to claim 1, wherein the surface of the composite oxide is coated with ceramics. 4. 11~14Al ₂ O ₃ · La Group VIII of the periodic table of the ₂ O ₃ composite oxide consisting of lanthanum β-alumina represented by a carrier a catalytically active component composed mainly alkali metal and alkaline The catalyst supporting at least one selected from the earth metals, the hydrocarbons and steam 400 ~ 15
A method of using a heat-resistant catalyst for steam reforming, which comprises contacting at a temperature of 00 ° C. to produce a gas composed of hydrogen and carbon monoxide. 5. The method for using a heat-resistant catalyst for steam reforming according to claim 4, wherein the catalytically active component is at least one selected from Group VIII of the periodic table. 6. 11~14Al ₂ O ₃ · La Group VIII of the periodic table of the ₂ O ₃ composite oxide consisting of lanthanum β-alumina represented by a carrier a catalytically active component composed mainly, alkaline earth metal , Titanium, zirconium, vanadium, rare earth elements, Va group, VIa group, manganese, zinc, aluminum,
The catalyst supporting at least one selected from tin and lead is mixed with exhaust gas containing nitrogen oxides and 500 parts of ammonia.
A method for using a heat-resistant catalyst for reducing nitrogen oxides, which comprises contacting at a temperature of ˜1500 ° C. to reduce and detoxify the nitrogen oxides. 7. The nitrogen oxide reducing agent according to claim 6, wherein the catalytically active component is at least one of tungsten, vanadium, titanium, tin, cerium, iron, nickel and cobalt. How to use heat resistant catalysts. 8. 11~14Al ₂ O ₃ · La Group VIII of the periodic table of the ₂ O ₃ composite oxide consisting of lanthanum β-alumina represented by a carrier a catalytically active component composed mainly of zinc, chromium, A carbon monoxide or carbon dioxide-containing gas and hydrogen are brought into contact with a catalyst supporting at least one selected from vanadium and cerium at a temperature of 250 to 400 ° C. to convert the carbon monoxide into methane. Method of using heat resistant catalyst for methanation reaction. 9. The method according to claim 8, wherein the catalytically active component is at least one selected from Group VIII of the periodic table.
A method of using a heat-resistant catalyst for methanation reaction, which comprises: 10. 11~14Al ₂ O ₃ · La ₂ chromium O ₃ made of lanthanum β-alumina represented by the composite oxide as catalytically active component on a carrier composed mainly of zinc, vanadium, copper, silver, iron , Nickel and at least one of cobalt
Alcohol over room temperature over 1,500
A method of using a heat-resistant catalyst for dehydrogenation, which comprises contacting at a temperature of ℃ or less to perform dehydrogenation. 11. The method according to claim 10, wherein the alcohol is methanol and the temperature is 300 to 1000 ° C.
A method for using a heat resistant catalyst for dehydrogenation, which comprises contacting the catalyst at the temperature of. 12. The method for using a heat resistant catalyst for dehydrogenation according to claim 11, wherein the catalytically active component comprises at least one of copper and zinc.