JPS60222145A - Method for using heat resistant catalyst - Google Patents

Abstract

PURPOSE:To suppress the flocculation of a catalytic active component even under the reactive conditions of a high temp. and the decrease in the specific surface area of a carrier contg. a specific ratio of La.beta alumina by depositing said active component on the carrier. CONSTITUTION:The catalyst is formed by depositing an active component such as copper, zinc, chromium, rare earth, etc. on the carrier contg. La.beta alumina at >=10wt% by the weight of the carrier in the method for effective chemical reaction at >=800 deg.C in the presence of the catalyst. The atomic ratio La/Al between La and Al of this carrier ranges 2/98-20/80 and the carrier contg. the La.beta alumina has >=5m<2>/g specific surface area. The above-mentioned catalyst can suppress flocculation of the active component even under the reactive conditions of a high temp. and the decrease in the specific surface area of the carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a heat-resistant catalyst or adsorbent that can be stably used in a temperature range of 800 C or more and 15,000 C or less, and a method for using the same.

The catalyst or adsorbent of the present invention has a temperature of 800C or higher, especially 90C or higher.
Suitable for use at temperatures between 0 and 1500C.

[Background of the invention]

Products that use catalysts to carry out reactions at high temperatures include automobile exhaust gas purification, hydrocarbon removal, odor removal, and oxidation and reduction in normal chemical processes.

Dehydration systems, hydrogenation systems, etc. are known. Recently, there has been a movement to apply catalytic combustion technology to large-capacity boilers, gas turbines, gas turbines for aircraft, etc.

In these methods, the reaction temperature is about 600C or higher, and depending on the conditions, it can reach up to 1400-1500G.

Therefore, there is a need for a catalyst that exhibits little reduction in catalytic activity even in such a high temperature range and has high thermal stability.

Catalysts conventionally used as high-temperature catalysts include alumina, silica, silica-alumina, etc. as carriers on which precious metals or base metal components are supported, or zirconia, aluminum titanate, cordierite, and silicon nitride. Ceramic materials have been used as carriers, the surface of which is coated with activated alumina, etc., to support sealing metal components.

However, when these catalysts have a molecular weight of 8,000 or more, the crystal structure of the support changes (for example, in the case of alumina, the crystal structure changes from r-type to α
However, the specific surface area decreases due to crystal growth (phase transition to a new type) and crystal growth, and the number of active sites decreases due to aggregation of active ingredients, resulting in a loss of catalytic activity. Catalysts using the above-mentioned ceramic materials have the drawback that although the ceramic itself has high heat resistance, the coating material has low heat resistance, so that the catalyst components are not effectively utilized.

[Purpose of the invention]

The object of the present invention is to improve the above-mentioned drawbacks of the prior art, and to provide a heat-resistant catalyst that can suppress aggregation of active ingredients and a decrease in the specific surface area of a support even under high-temperature reaction conditions, and a method for using such a catalyst. It is about providing.

[Summary of the invention]

Transitional aluminas such as , r or η have a high specific surface area and are currently widely used as carriers and coating agents. As it grows, it becomes a sintered body and its specific surface area decreases significantly, and along with this, particles of noble metals, base metals, etc., which are catalytically active components, agglomerate, resulting in a decrease in catalytic activity. For example, in the case of a conventional catalyst in which Pd is supported on an alumina support, the specific surface area is approximately 150 ry after heat treatment at 600C.
The particle size of 12/g Xp d is about 30 people,
When heated for 2 hours at 1200t:', the specific surface area is approximately 3m.
2/g, the Pd particle size is approximately 200OA. That is, by high-temperature heat treatment, the Pd particles that were highly dispersed on the carrier agglomerate into giant particles due to a decrease in specific surface area, resulting in a decrease in active sites and loss of catalytic activity.

As a heat-resistant catalyst that improves the shortcomings of activated alumina, a method is proposed in which magnesia is added to alumina and magnesia/alumina spinel is used as a carrier (% Kosho 57-341).
9), and a catalyst using a carrier prepared by adding chromium, tungsten, cerium, etc. to alumina (Japanese Unexamined Patent Publication No. 50-99988) has been proposed. Although each of these catalysts has advantages, it is necessary to further improve heat resistance.

The present inventors conducted various studies to improve the thermal instability of conventional catalysts and prevent the supported catalyst component particles from agglomerating. As a result, the present inventors discovered that lanthanum can be obtained by adding lanthanum to aluminum. β alumina (La203 ・11
~14 At20g) It has been found that a catalyst in which a carrier is combined with a catalytically active component such as a noble metal or a base metal is very effective.

The present invention is a heat-resistant catalyst in which a catalytically active component is supported on a carrier mainly composed of lanthanum/β-alumina, which is a composite compound of aluminum and lanthanum. Furthermore, it is most desirable that the carrier consists only of lanthanum and β-alumina;
Other carrier components may also be included. That is, in addition to the main components of lanthanum and β-alumina, it may contain other forms of compounds of lanthanum oxide and alumina, or it may contain uncombined surplus alumina and/or lanthanum oxide. Furthermore, one or more compounds selected from oxides such as silica, magnesia, calcia, barrier, beryllia, zirconia, titania, thoria, and tin oxide, cordierite, mullite, spongene, aluminum titanate, silicon carbide, and silicon nitride. It is possible to include.

In this case, the amount of lanthanum/β-alumina in the carrier is preferably at least 10% by weight, preferably at least 30%, based on the total weight of the substances constituting the carrier. Below 10%, the specific surface area is 5m
''/g or less, which is not preferable as a catalyst carrier.Also, one selected from rare earth elements other than lanthanum, such as cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, erbium, thulium, and lutetium. It is also possible to include the above.

Lanthanum/β alumina is L a20 a/11~14
At! This composite oxide is a compound consisting of 03, and this composite oxide is a compound consisting of 80 oc or more of these hydroxides or oxides.
In a carrier mainly composed of lanthanum and β-alumina, which is preferably produced by firing at a temperature of 900°C or higher, the composition of lanthanum and aluminum is I in terms of the atomic ratio of the metal components.
The range of a/At=2/98 to 20/80 is preferable. When the amount of lanthanum is less than this range, alumina is generated in addition to lanthanum and β-alumina, and the specific surface area decreases at high temperatures. In addition, when there is a large amount of lanthanum, in addition to lanthanum and β-alumina, a large amount of lanthanum aluminate is formed, resulting in a decrease in the specific surface area. Even when used at high temperatures, the catalytic active components coagulate due to heat and stable catalytic performance can be maintained. This is because lanthanum and β-alumina have high heat resistance, a large specific surface area, and highly dispersed active ingredients.

Lanthanum/β-alumina itself has high heat resistance and a large specific surface area, but detailed X-ray diffraction analysis shows that this compound also has the effect of suppressing the phase transition from γ-alumina to α-alumina and crystal growth. This became clear from the results of electron microscopy. In addition, nitrogen adsorption experiments have shown that the specific surface area of lanthanum and β-alumina decreases little under high-temperature conditions.As a result of observing the particle size of the active ingredient under an electron microscope, it was found that it exists in the form of fine particles. , it was revealed that it was highly dispersed. For example, a catalyst in which Pd is supported on lanthanum/β-alumina calcined at 1200 C has a specific surface area of 58 m2/g and a Pd particle size of approximately 100 A, which is much more heat resistant than the catalyst using alumina alone as described above. was excellent.

As a method for producing lanthanum and β-alumina, the usual co-precipitation method, deposition method, crosstalk method, impregnation method, etc. can be applied, but the co-precipitation method is particularly preferable. The firing temperature is 800C or higher at which lanthanum/β alumina is formed, preferably 900C or higher and 1500C or lower. Firing temperature is so
Below oC, lanthanum and β-alumina are not produced, and 150
If it exceeds 0C, sintering will progress, which is not preferable. The powder containing the above-mentioned 7/tan/β-alumina can be used after being formed into various shapes, such as spherical, 9 cylindrical, ring, . . . nicum shapes. Also, inorganic heat-resistant base materials molded into various shapes, such as mullite, cordierite,
It is also possible to use a carrier coated with powder containing tan/β alumina on ceramics such as α aluminum r1 aluminum titanate.

A catalytically active component is supported on the carrier made of the above-mentioned lanthanum and β-alumina and catalyzed. 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 raw materials for the catalytic active component, commonly used materials such as inorganic salts and organic complex salts may be used. After impregnating or crossing the carrier,
Heat and bake at desired temperature.

The catalyst obtained in the present invention is 800C or higher, preferably 90C or higher.
Use at temperatures above 0C. The upper limit of operating temperature is 1500
A temperature of tZ', preferably 1400t:' is desirable.

In this case, the catalyst needs to have a specific surface area of 5 m3/g or more. In other words, if it is less than 5 m2/g, the catalytic active components will not be highly dispersed and will aggregate, resulting in a decrease in activity. By using a catalyst with a specific surface area of 5 m2/g or more, highly active and heat-resistant components can be obtained. A chemical catalyst is obtained.

The catalyst of the present invention can be used for combustion reactions of hydrogen or carbon oxides or hydrocarbons, for removing bad odors from organic carbon compounds containing oxygen, sulfur, nitrogen, etc., and for purifying automobile exhaust gas.

Oxidation and reduction reactions used in ordinary chemical plants.

It can be used for chemical reactions of 800C or higher, such as dehydrogenation and hydrogenation reactions.

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 combustion components, the catalytic active components include manganese, chromium, and rare earths from group Ⅰ of the periodic table. elements, zirconium, tin, zinc, copper,
It is desirable to use magnesium, barium, strontium, calcium, etc. Hydrocarbons used in such combustion reactions include methane, ethane, propane butane, pentane, liquefied natural gas, petroleum gas, and the like. Although the reaction temperature varies depending on the type of gas, a wide temperature range of 800C or higher can usually be applied.

When performing a combustion reaction, the gas is brought into contact with a catalyst in the presence of oxygen.

It is desirable to use a platinum group element as the carbonization active component. Further, using the above catalyst, malodorous components such as methyl ethyl ketone, toluene, formalin, butyl acetate, hexane, aldehyde, phenol mercaptan, and ketone can be removed at 800 C or higher.

When the catalyst of the present invention is used to purify exhaust gas from an internal combustion engine, such as automobile exhaust gas, the catalytic active components include elements from group Ⅰ of the periodic table, manganese, chromium, zirconium, rare earth elements, tin, zinc, copper, etc. using at least one of magnesium, barium, strontium, and calcium,
The exhaust gas is brought into contact with the catalyst at a reaction temperature of 800C or higher. As a result, carbon monoxide and hydrocarbons in the exhaust gas can be oxidized into water and carbon dioxide, and nitrogen oxides can be reduced and converted into nitrogen and water, making them harmless.

When the catalyst of the present invention is used in a dehydrogenation reaction, at least one of chromium, zinc, vanadium, copper, silver, iron, nickel, and cobalt is used as a catalytic active component, and the Do it at temperature. In the case of methanol dehydrogenation, it is desirable to use at least one of copper and lead as the catalytically active component. -Also, the reaction temperature is preferably 800 to 100OC.

In the reaction of oxidizing an inorganic compound, for example, the reaction of oxidizing ammonia to produce nitrogen oxides, the catalyst of the present invention is used as an active ingredient of group I of the periodic table, manganese, chromium, zirconium, rare earth elements, tin, zinc, copper. , silver, magnesium,
At least one of barium, strontium, and calcium is used by contacting it with a gas containing oxygen at a temperature of 1200 C or less.

[Embodiments of the invention]

EXAMPLES The content of the present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples in the same way.

Example 1 375.1g of aluminum nitrate and 22.8g of lanthanum nitrate
Dissolve g in 1 t of distilled water (La lA1 = 5 /
95).

Add 3N ammonia water dropwise to this solution while stirring.
Neutralize to H7.5. The obtained coprecipitate of aluminum and lanthanum is thoroughly washed with water, dried, crushed, and calcined at 700C for 2 hours. The obtained powder is molded into a press molding machine with a diameter of:
It was made into a cylindrical shape with a length of 3 m and a length of 3 m, and was used as a carrier.

On the other hand, a comparative example carrier consisting only of alumina was obtained by preparing in the same manner as described above except that lanthanum nitrate was not added.

Example 2 Prepared in the same manner as in Example 1 except for changing the amounts of aluminum nitrate and lanthanum nitrate, La/At (molar ratio) = 2/98.8/92° 10/90.20/80 A carrier with the following composition was prepared.

Example 3 A spherical r-alumina carrier (commercially available) having a diameter of 3 m was impregnated with a lanthanum nitrate solution, dried at 180C, and then calcined at 700C to obtain a carrier. This carrier had I, a/A4=5/95.

The carriers obtained in Examples 1 to 3 and the comparative carrier were calcined at 1200C for 2 hours, and the specific surface area and crystal structure were examined by X-ray diffraction. The results are shown in Table 1.

As is clear from Table 1, the specific surface areas of the carriers of Examples 1 to 3 are 2 to 10 times larger than that of conventional alumina, indicating that they have excellent heat resistance. Furthermore, it is clear that lanthanum/β-alumina is produced as a compound of At and La in this region with a large specific surface area. Therefore, it can be seen that lanthanum/β-alumina is suitable as a support for a catalyst for high-temperature reactions.

Example 4 After impregnating the carrier prepared in Example 1 with a palladium nitrate solution to a concentration of 0.5% as palladium,
It was dried at 0C for about 5 hours, then fired at 1200C for 3 hours, and the performance of the methane combustion reaction was evaluated. As a comparative example, alumina alone was prepared in the same manner. A gas having the following composition was flowed at a space velocity of 25,000 h-'', and
A continuous test was conducted for 0 hours.

Gas composition: 3% dimethane, residual air In this experiment, the reaction gas was preheated to 550C. When the methane reaction rate reaches 90% or more, the temperature of the catalyst layer reaches 1200C, so the durability of the catalyst at high temperatures can be evaluated. The experimental results are shown in Table 2.

It is clearly seen from Table 2 that the catalyst according to this example is suitable for catalytic combustion reactions at high temperatures.

When the specific surface area of the Example catalyst and the Comparative Example catalyst in Table 2 was measured after 100 hours of activity measurement, the former was about 55 m''/g and the latter was less than 1 m''/g. Furthermore, as a result of measuring the surface area of palladium dispersed on the carrier, the example catalyst had a surface area of 78 m2/g-Pd, while the comparative example catalyst had a surface area of 20 m'/g-Pd.
g-Pd. As described above, it can be seen that the Example catalyst has a better specific surface area and a better PD dispersion state than the Comparative Example catalyst, and is excellent as a heat-resistant catalyst.

Example 5 3750 g of aluminum nitrate and 480 g of lanthanum nitrate are dissolved in 10 t of distilled water (La/Az=5/9s).

700C fired powder 1 obtained in the same manner as in Example 1 below
Add 2.5 tons of distilled water to the powder and grind with a vibration mill until the average diameter of the powder becomes about 11 zm to prepare a slurry-like immersion liquid. After immersing a commercially available cordierite-based structure (diameter 90, length 75M) in this immersion liquid, it was taken out from the immersion liquid and dried at 120C for 50 minutes.
Heat treatment was performed at 0C for 1 hour. This operation was repeated, and finally it was fired at 1000 C for 2 hours. The specific surface area of the catalyst at this time was 28 In"/g. The thus obtained NO-NICAM structure had a coating layer of 18.7% by weight of composite oxide. Next, the NO-NICAM structure obtained was was immersed in an aqueous solution containing chloroplatinic acid and rhodium chloride.
After drying at C, it was fired at 1000C.

The catalyst had 1.5% by weight platinum and 0.4% by weight rhodium. This catalyst was used for purifying automobile exhaust gas. It was used as a catalytic converter in a regular automobile engine (1800cc class) and tested for 10,000km (at temperatures up to 9000℃), resulting in carbon monoxide (CO) of 1.0 g/Km in 10 modes.

Hydrocarbons (HC10.19g/Km, nitrogen oxides (N
Ox ) Oyl was 5 g/Km. From this result, when the catalyst of the present invention is used, CO and HC can be oxidized, and carbon dioxide and water, and NOx can be reduced and rendered harmless to nitrogen and carbon dioxide.

Example 6 In this example, a methanol dehydrogenation catalyst was investigated. On the carrier of La/A4=20780 obtained in Example 2,
Impregnated with nitric acid steel and zinc nitrate solution, dried and fired for 1 oooc. The content of copper and zinc is 20% by weight each,
It is 10% by weight. Fill the reaction tube with these catalysts, and
After the temperature was raised to 50C, methanol was introduced and a dehydrogenation reaction was performed to produce formalin. The conversion rate of methanol was 98 or more, and the selectivity of formalin was also about 5 times that of conventional methods.

Example 7 In this example, the performance of an organic solvent as a treatment catalyst was investigated. A carrier having the composition of La/At=s/9s shown in Example 1 is impregnated with a mixed solution of chloroplatinic acid and chromium nitrate, dried and then calcined at 1000C for 2 hours. The platinum content of this catalyst is 0.5% by weight, and the chromium content is 10% as CI'a03.
Weight%. A reaction tube is filled with 5CC of this catalyst, and a gas containing 11001)I) of benzene, phenol, and methyl ethyl ketone as an organic solvent is introduced into the catalyst layer together with air. Set the reaction temperature to 95 (1?),
A continuous test was conducted at 0 o'clock, and the outlet concentration was measured at each hour. As a result, after 100 hours, the removal rate was 99.3% for benzene and 99% for phenol.
．． 6%, and 99.4% for methyl ethyl ketone, which was the same as the removal rate immediately after the start of the reaction, and no decrease in activity was observed.

Example 8 In this example, the performance as a catalyst for removing bad odor was investigated. A carrier having the composition of La/At=10/90 shown in Example 2 is impregnated with a mixed solution of cobalt nitrate and manganese nitrate, dried at 180C, and then fired at 1000C. This catalyst contains 0.3% cobalt as CoO and 5% manganese as MnO.

Air containing 200 ppm of formalin, 500 ppm of mercaptan, and 2001)I)m of toluene as malodorous components is introduced into a reaction tube filled with 10 cc of the above catalyst. The reaction temperature was set at 10ooc, and a continuous test was conducted for 50 hours. As a result, the removal rate was 99.1% for formalin, 99.7% for mercaptan, and 99.9% for toluene after 50 hours, indicating that high activity was maintained.Example 9 In this example, 800C The performance as a catalyst for the oxidation reaction in the above was investigated. The carrier of La/At=2/98 shown in Example 2 shown in Example 1 was impregnated with a mixed solution of chloroplatinic acid and rhodium chloride, and after drying, 2
Baked for an hour. This catalyst 20CQKNHs 11000
Air containing pI) was introduced and the reaction was carried out at 900C. As a result of analyzing the gas after the reaction and investigating the amount of NO produced, it was found that NO
The conversion rate was 97%.

The results show that the present catalyst exhibits high activity even in the oxidation reaction of N Hs at a high temperature of 900C.

Example 10 In this example, the oxidation reaction of carbon monoxide (CO) was investigated. Using a catalyst in which Pd was supported on the carrier of La/At=8/92 in Example 2 in the same manner as in Example 1, C010j
Air containing J was introduced into the catalyst, and the CO concentration at the outlet was measured to determine the reaction rate.

The experiment was conducted using a catalyst of 8 cc and a reaction temperature of 1,100 t.
A continuous test was conducted for 00 hours. The CO oxidation rate after 200 hours was 99.8%, which was almost the same as 99.9% at the initial stage of the reaction, and it had excellent high-temperature durability.

Additionally, the specific surface area of the catalyst after a 200-hour test was investigated.4
sm"/g, which was not much of a decrease compared to the initial value of 54 m2/g.

Example 11 In this example, the combustion reaction of hydrogen was investigated.

The La/At=20/8 (1) carrier shown in Example 2 was impregnated with a mixed solution of steel nitrate and palladium nitrate, and
After drying, it was fired at 1200C for 2 hours. This catalyst is Pd
0.3% by weight and 5% by weight of CuO.

Air containing 3.8 tons of hydrogen was added to 10 cc of this catalyst at a temperature of 11
At 00t:', four people analyzed the hydrogen gas after the reaction and determined the combustion rate. If the reaction time is 1 hour, the combustion rate is 100%.
Even after 100 hours, a combustion rate of 9999% was obtained. Furthermore, as a result of measuring the specific surface area before and after the reaction, the area before the reaction was 22m2. /g.

The reaction loss was 18 m''/g, and no significant decrease was observed.It is thus seen that the present catalyst exhibits excellent durability even in the high-temperature combustion of hydrogen.

Example 12 In this example, the propane combustion rate of catalysts in which palladium was impregnated into carriers having different contents of lanthanum and β-alumina was investigated. After adding the same amount of titanium oxide powder to the lanthanum/β-alumina powder obtained in the same manner as in Example 1 and kneading,
It was formed into a 3φ x 3h size using a tablet press and then fired at 700C to obtain a carrier. This carrier is impregnated with palladium nitrate, and after drying,
It was fired at 1200C for 2 hours. In this catalyst, the content of lanthanum/β-alumina is sowt% J, and the amount of Pd supported is 0.5% by weight based on the carrier. Main catalyst B cc
Then, air containing 3 g of propane was introduced, and a 1200 CC combustion reaction was carried out for 200 hours. As a result, the propane combustion rate after 200 hours was 99.2%, maintaining high activity. Further, the specific surface area before the reaction was 34 m2/g, and after 20 hours it was 2 sm''/g, and the decrease was small, and the present catalyst has excellent heat resistance.

Example 13 The same as Example 9, except that the content of lanthanum/β-alumina in the carrier was 1.0% by weight. In this case, the methane combustion rate after 200 hours was 99.0%. In addition, the specific surface area decreased from 21 m2/g to 10 m"/g. From this, the content of lanthanum and β-alumina in the carrier was 1.
It was found that more than 0.00% by weight is necessary.

〔Effect of the invention〕

Claims (1)

[Claims] 1. A method in which a chemical reaction is carried out at a temperature of 800 t:' or higher and in the presence of a catalyst, where the catalyst comprises an active ingredient supported on a carrier containing lanthanum/β alumina at least 10% by weight of the carrier. A method of using a heat-resistant catalyst characterized by: 2. A method of using a heat-resistant catalyst according to claim 1, wherein the carrier is made of a composite oxide of lanthanum and alumina. 3. A method of using a heat-resistant catalyst according to claim 1, characterized in that the carrier is lanthanum/β-alumina. 4. The method of using a heat-resistant catalyst according to claim 1, characterized in that the atomic ratio of lanthanum to aluminum in the carrier is 2/98 to 20/80. 5. In claim 1, the lanthanum β
A method of using a heat-resistant catalyst, characterized in that the carrier containing alumina has a specific surface area of 5 m"/g or more. 6. In claim 1, the catalytic active component is a periodic Supporting at least one of Group III, copper, silver, Group nA, zinc, aluminum, yttrium, gallium, Group II, vanadium, niobium, antimony, bismuth, chromium, molybdenum, tungsten, manganese, and rare earth elements. 7. In claim 1, the chemical reaction of 5 ooc or more includes an oxidation reaction or combustion reaction, a reduction reaction, a hydrogenation reaction of a substance made of inorganic and/or organic substances, A method for using a heat-resistant catalyst, characterized by carrying out either one of a dehydrogenation reaction and an adsorption reaction. 8. In claim 1, it is provided that the operating temperature of the catalyst is 1500 t:' or less. A method of using a heat-resistant catalyst characterized by: 9. A method of using a heat-resistant catalyst according to claim 1, characterized in that the operating temperature of the catalyst is within a range of 900 to 1500 r.