JP2559718B2 - Heat resistant catalyst for catalytic combustion reaction and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-resistant catalyst, particularly a highly active catalyst having excellent heat resistance and used for a reaction such as catalytic combustion, and a method for producing the same.

(Prior Art) Catalysts for catalytic combustion are widely used today for combustion removal of carbon monoxide and hydrocarbons in automobile exhaust gas, detoxification of factory exhaust gas, deodorization, flameless combustion, etc. Since the heat resistance of many catalysts is insufficient, the catalyst operating temperature should be about 80
It is used under special consideration, such as limiting or controlling the temperature to 0 ° C or lower to prevent the activity of the catalyst from decreasing. Accordingly, there has been a desire for a catalyst having even better heat resistance. More recently,
In the field of gas turbines, boilers, jet engines, etc., attention has been paid to performing catalytic combustion at a higher temperature.
The emergence of a heat-resistant and highly active catalyst that maintains a high activity even at a high temperature exceeding ℃ has been strongly desired.

The heat resistant catalyst is usually obtained by supporting a catalyst component on a heat resistant catalyst carrier. From the viewpoint of the present inventors,
Based on the most heat-resistant alumina carrier among the widely used catalyst carriers at present, we have been developing a heat-resistant composition with much better heat resistance. No. is MeO.6Al ₂ O ₃ (Me is Ca
And / or Ba and / or Sr) as a main component can be a catalyst carrier having particularly excellent heat resistance.

Furthermore, the present inventors have filed a MeO patent application as Japanese Patent Application No. 61-140287.
The composition containing 6Al ₂ O ₃ as a main component is aluminum and
It has been shown that an excellent heat-resistant composition can be obtained when it is produced from a composite and / or mixed alkoxide of a metal represented by Me, and a suitable production method thereof is proposed.

(Problems to be Solved by the Invention) A catalyst obtained by impregnating or coating a catalyst carrier containing MeO.6Al ₂ O ₃ (Me is Ca, Ba or Sr) as a main component with the catalyst component is a conventional alumina-supported catalyst. Although it is a catalyst with significantly superior heat resistance compared to, when it is used as a catalyst for catalytic combustion reaction at a high temperature of over 1200 ° C, the carried catalyst component sinters and the catalytic activity The decrease was inevitable, and the excellent heat resistance of the catalyst carrier was not fully utilized.

An object of the present invention is to eliminate this drawback and to provide a catalyst having more excellent heat resistance.

(Means for Solving the Problems) The inventors of the present invention have conducted diligent experiments and research to obtain such a catalyst having more excellent heat resistance, and as a result, have found that a special combination of the catalytically active component and the catalyst carrier component has been found. It was found that a catalyst having extremely high activity and excellent heat resistance can be obtained by the production, and the present invention has been completed. That is, the present invention is a composition formula AB _x Al
_12-y O _19-α (wherein A is one or more elements selected from the group consisting of Ba and Sr, B is one or more elements selected from the group consisting of Mn, Co, Fe, Cu and Cr, x is a number in the range of about 0.1 to 4, y is a number in the range of x to 2x, α is determined by the valence Z of the element B, The heat-resistant catalyst contains a composition represented by the formula (1) as a main component.

The catalyst of the present invention is particularly suitable as a catalyst for catalytic combustion, but is not limited to this application and can be used in many other reactions requiring high temperatures.

The present invention further provides that aluminum and A are Ca, Ba and Sr.
There is provided a method for producing a heat-resistant catalyst of the present invention using as a raw material a composite or mixed alkoxide of a metal represented by one or more elements selected from the group consisting of: According to this alkoxide method, it becomes possible to provide a catalyst having further excellent heat resistance as compared with the methods generally used for the production of catalysts or catalyst carriers such as the solid mixing method and the precipitation method from an aqueous solution.

The content of the element A in the heat-resistant catalyst of the present invention is such that the elements B and Al
If the total number of atoms of is 8.3 for 100 atoms, AB _x Al
_{The 12-y} O _19-α composition has the most stable and heat-resistant form, but the content of the element A is not limited to this ratio, and the ratio of A: (B + Al) is 8.3 atomically. It is particularly preferable to take a value close to: 100, that is, a value in the range of about 7 to 9: 100, but a value of a ratio of about 2.5 to 10: 100 may be used. If the ratio of element A exceeds this range, AO or AO.
Al ₂ O ₃ , if it is small, the amount of Al ₂ O ₃ present in the catalyst will be too large, and the specific surface area will decrease due to the sintering of these oxides at high temperatures, which in turn lowers the catalytic activity. It is not preferable because it will occur.

The value of x, which indicates the amount of the active ingredient B in AB _x Al _12-y O _19-α contained in the heat-resistant catalyst of the present invention, is about 0.1 to 4, particularly about 0.2 to 3.
It is desirable to be within the range. When x is less than 0.1, the active effect is not sufficient due to lack of active ingredient B,
When x is larger than 4, the active element B cannot be incorporated into the crystal structure of the AB _x Al _12-y O _19-α composition having the layered aluminate structure well, and the excess element B is precipitated as a single oxide. However, this causes a decrease in activity due to sintering. By the way, the present inventors are the main component of the heat-resistant catalyst of the present invention.
It is estimated from the X-ray diffraction results that the AB _x Al _12-y O _19-α composition has a layered aluminate structure such as a magnetoplumbite-like structure or a β-alumina-like structure represented by BaO · 6Al ₂ O _3. It is believed that this imparts heat resistance.

In addition to the alumina and the oxides of the elements A and B constituting the heat-resistant composition AB _x Al _12-y O _19-α , a third component that imparts heat resistance, such as silica, a rare earth oxide and an alkali metal oxide, is added. The inclusion of a small amount in the heat resistant catalyst does not depart from the scope of the present invention.

The composition represented by AB _x Al _12-y O _19-α contained in the heat-resistant catalyst of the present invention is, so to speak, an oxide of element A, an oxide of element B and a three-component composite oxide of alumina. Is. Next, each of the above oxides will be described.

The starting material for aluminum oxide contained as a main component in the heat-resistant catalyst of the present invention, when a solid mixing method,
Alumina, generally known as transition alumina, is preferred. Six types of transitional alumina are known, such as chi, kappa, gamma, eta, theta, and delta, but all of these types of alumina are unstable as they are, and when exposed to high temperatures, α- It is converted to alumina and causes a decrease in activity of the catalyst and embrittlement of catalyst particles.

As a starting material for aluminum oxide, when a precipitation method is used, a water-soluble compound such as aluminum nitrate, aluminum sulfate, or sodium aluminate can be generally used.

Various compounds such as oxides, hydroxides, carbonates, nitrates and sulfates of the element A are used as starting materials for the oxide of the element A as one main component of the heat resistant catalyst of the present invention. it can. Hereinafter, the element A according to the present invention will be described as Ba, but the same applies to Ca and Sr.

Starting materials for the oxide of element B, which is the main active component of the heat-resistant catalyst of the present invention, include oxides, hydroxides, carbonates, nitrates, sulfates, chlorides and complex salts of element B. Organic acid salts, complex salts such as ammine complex salts, chromic anhydride,
All compounds generally used as a raw material for producing a catalyst, such as an acid of element B such as manganate and chromate and salts thereof, can be used. Hereinafter, the element B according to the present invention will be described as Co, but the same applies to Mn, Fe, Ni, Cu and Cr.

In producing a catalyst from these aluminum compounds, barium compounds and cobalt compounds, various methods that are usually used during catalyst production can be used, such as a precipitation method such as a coprecipitation method, a solid mixing method, a kneading method and an impregnation method.

The present invention proposes an alkoxide method as a special method for producing a heat-resistant catalyst. In the case of the alkoxide method, raw materials for aluminum oxide and barium oxide are alkoxides of aluminum and barium. The alkoxide is preferably an alkoxide having 1 to 4 carbon atoms such as methoxide, ethoxide, isopropoxide and butoxide. These alkoxides may be commercially available ones, but they can also be prepared using metal aluminum and metal barium and alcohols.

The shape of the heat resistant catalyst of the present invention may be powder,
Any general shape such as tablets, rings, spheres, extruded shapes, honeycombs, etc. can be adopted as a catalyst.

The heat-resistant catalyst of the present invention is usually made into a product through a final step or an intermediate step of drying and / or calcination, but calcination is not always necessary, and sometimes it is not carried out. However, in the case of a catalyst, particularly a catalyst for catalytic combustion, calcination at a temperature around the maximum use temperature is an important operation for obtaining a thermally stable composition. For example, when the heat resistant catalyst of the present invention is a catalyst for catalytic combustion, it is naturally expected that it will be exposed to a high temperature exceeding 1300 ° C. during use. In such a case, it is preferable to bake at a temperature of 1300 ° C. or higher. At such a high firing temperature, a composition not according to the present invention, such as a γ-alumina carrier, a silica-alumina carrier, a rare-earth element, a substance to which a heat resistance improver such as an alkali is added, or the like, is converted into α-alumina, A remarkable decrease in the specific surface area and an accompanying activity, particularly a low temperature activity, cannot be avoided.

In the production of the heat-resistant catalyst of the present invention, it is usually preferable to calcine at a temperature of 900 ° C. or higher, but when calcining at a temperature higher than 1300 ° C., the correlation between the calcining temperature and the specific surface area is measured in advance. Incidentally, it is necessary to set the specific surface area to an appropriate range, for example, a specific surface area of about 2 m ² / g or more for a specific catalyst combustion carrier.

The heat-resistant catalyst of the present invention preferably contains a water-soluble aluminum salt, a water-soluble barium salt and a water-soluble cobalt salt as Al: Ba: Co.
The coprecipitant is added to an aqueous solution mixed in a ratio of 100: 2.5 to 10: 0.1 to 4 calculated as an atomic ratio of to produce a mixed composition in the form of a coprecipitate, and the mixture is washed-filtered or evaporated to dryness. Through the process,
The coprecipitate obtained is calcined at about 200 to 500 ° C. and then calcined at 1200 to 1500 ° C. for about 5 to 30 hours. in this case,
Examples of the water-soluble aluminum compound include aluminum nitrate, aluminum sulfate, and aluminum chloride, and examples of the water-soluble barium compound include barium nitrate and barium chloride. Examples of the water-soluble cobalt compound include cobalt sulfate, cobalt chloride, and cobalt nitrate. is there.

In this case, coprecipitants include caustic soda, sodium carbonate,
Caustic potash and ammonia water can be used. Further, as the water-soluble raw material, sodium aluminate, barium hydroxide, cobalt ammine complex salt and the like can be used. In this case, as the coprecipitating agent, acids such as cobalt nitrate and nitric acid are adopted. The preliminary calcination step may be omitted.

An even more preferred method for producing the heat-resistant catalyst of the present invention is an alkoxide method using a composite or mixed alkoxide of aluminum and barium as a raw material. The formation of the oxides of aluminum and barium is particularly preferably effected through hydrolysis. As a method of adding cobalt in this case, there is a method of adding cobalt simultaneously with water necessary for hydrolysis in the form of an aqueous solution of cobalt nitrate or the like.

The method of alkoxide decomposition is not limited to hydrolysis, and methods such as thermal decomposition can also be adopted. Further, it is not necessary that all of these oxides are produced from alkoxide, and alumina, barium carbonate, etc. may be added to the decomposition product of alkoxide. In the case of hydrolysis, the hydrolysis is preferably carried out by heating to about 50 to 100 ° C. rather than at room temperature. The effect of the pH of the water added for hydrolysis was not particularly observed, but the aging time after adding water greatly affected the specific surface area of the heat-resistant composition, and the longer the aging time, the higher the specific surface area I do. Therefore, the aging time is preferably at least 1 hour, and it is particularly desirable to set the aging time as long as possible within an economically acceptable range such as 5 to 10 hours. Although the specific surface area of the heat-resistant composition of the present invention is also affected by the amount of water used for hydrolysis, the amount of water required to hydrolyze the entire amount of the complex or mixed alkoxide present to hydroxides and alcohols. It has been found that an unexpectedly large specific surface area can be obtained even when less than water (hereinafter referred to as "water equivalent") is used. The amount of water to be added may be equal to or less than the equivalent of water. On the other hand, it is not preferable to use an excessively large amount of water because it causes an excessive amount of processing equipment and energy consumption, and it is preferable to set the amount of water to about 10 equivalents or less from the economical viewpoint. Therefore, the amount of water used is usually about 0.5 to 10 equivalents. However, the amount of water used is not limited to this range, and may be outside this range if it is not so suitable.

The heat-resistant catalyst according to the alkoxide method of the present invention is, in a preferred production example, aluminum alkoxide and barium alkoxide in an Al: Ba atomic ratio of 1 in each.
Cobalt nitrate dissolved in alcohol so that it is present in the ratio of 00: 2.5-10, and in the amount of water in the range of approximately 0.5-10 in the equivalent ratio, cobalt nitrate in the ratio of Co: Al atomic ratio of 1-2: 100. Was added and the mixture was hydrolyzed at a temperature in the range of 50 to 100 ° C. After aging for 5 to 10 hours, the solvent was removed by evaporation to dryness, and the resulting decomposition product mixture was added to about 200 It is obtained by calcining at about 500 ° C. and then at about 900 ° C. or higher for about 5 to 30 hours. The former calcination step may be omitted.

In order to impart low temperature activity to the heat-resistant catalyst of the present invention, it is effective to further impregnate and support a small amount of a noble metal, particularly a platinum group noble metal such as Pt, Ru, Rh, Pd. Such a noble metal-supported catalyst is also included in the present invention.

(Function) The heat resistance of the heat-resistant catalyst of the present invention is increased due to its excellent heat resistance and a composite oxide AB _x A having a layered aluminate type crystal structure.
It is believed that this is due to the formation of the l _12-y O _19-α composition. The stable layered aluminate-type crystal structure AB _x Al _12-y O _19-α in the heat-resistant catalyst of the present invention is _α of transition alumina.
-It is considered that it is formed at a relatively low temperature below the transition temperature to alumina, which suppresses the transition and sintering of alumina to α-alumina, and retains the specific surface area and activity at higher temperatures.

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 Aluminum oxide, barium carbonate and cobalt oxide (Co ₂ O ₃ ) were fed into a ball mill and ground and mixed for about 24 hours. The molar ratio of these raw materials used is Al ₂ O ₃ : BaCO ₃ : Co
O was set to 71.4: 14.3: 14.3. Then 1450 this mixture
The catalyst of Example 1 was obtained by calcination for 5 hours.

The catalyst BET specific surface area of Example 1 was 3.3 m ² / g.

Comparative Example 1 Aluminum oxide and barium carbonate were fed into a ball mill and ground and mixed for about 24 hours. Molar ratio of these two raw materials Al
₂ O ₃ : BaCO ₃ was set to 85.7: 14.3. The resulting mixture is then 13
It was calcined at 00 ° C for 5 hours to obtain a catalyst carrier. After impregnating this catalyst carrier with cobalt acetate, it was calcined at 1300 ° C. for 10 hours to obtain a catalyst of Comparative Example 1. The supported amount of cobalt was 10% by weight of the catalyst carrier as cobalt oxide (CoO). This film was that the CoO supported 10% carrier BaO · 6Al ₂ O _3.

The BET specific surface area of the catalyst of Comparative Example 1 was 6.6 m ² / g.

USE EXAMPLE 1 Using the catalysts of Example 1 and Comparative Example 1 individually, a methane combustion activity test was carried out by an atmospheric fixed bed flow reactor. The gas used for the test was 1% by volume of methane and 99% by volume of air.
The gas consisting of the gas was flown through the catalyst layer at a flow velocity of 48,000 ^-1 .

 The test results are shown in Table 1.

Although the catalysts of Example 1 and Comparative Example 1 had the same cobalt content, the activities of both catalysts were remarkably different, and the Example 1 catalyst having a poor specific surface area had a higher activity than the Comparative Example 1 catalyst. showed that.

Examples 2 and 3 Using the same starting materials as in Example 1, the same operations as in Example 1 were carried out to obtain the catalysts of Examples 2 and 3. However, while the catalyst of Example 1 has a composition represented by BaO.CoO.5Al ₂ O ₃ , the catalyst of Example 2 has BaCoAl ₁₁ O _{18.5, that} is, BaO.CoO.
A catalyst having a composition equivalent to 5.5Al ₂ O ₃ , the catalyst of Example 3 is
It has a composition corresponding to BaCoAl _11.5 O _{18.25, that} is, BaO · 0.5CoO · 5.75Al ₂ O ₃ .

The BET specific surface areas of the catalysts of Examples 2 and 3 were 3.4 m ² / g and 3.2 m ² / g, respectively, and like the catalyst of Example 1, the specific surface area was smaller than that of the catalyst of Comparative Example 1.

Use Example 2 The same activity test as in Use Example 1 was performed on the catalysts of Examples 2 and 3. The results of the activity test are shown in Table 2.

The catalyst of Example 2 is inferior in specific surface area to the catalyst of Comparative Example 1,
Moreover, the activity was excellent despite the fact that the cobalt concentrations were almost equal. It should be noted that the catalyst of Example 3 having a cobalt concentration as low as about half the amount of the catalyst of Comparative Example 1 exhibited significantly higher activity than the catalyst of Comparative Example 1.

Example 4 and Use Example 3 Under a nitrogen atmosphere, commercially available aluminum isoproxide and barium metal were dissolved in isopropyl alcohol at 80 ° C. for 5 hours, and a cobalt acetate aqueous solution was added dropwise to the resulting solution for hydrolysis. It was After aging for 12 hours, the resulting suspension was dried under reduced pressure at 80 ° C and calcined at 600 ° C, then 1350
The catalyst of Example 4 was obtained by calcination for 5 hours. This catalyst obtained by the alkoxide method is the same as the catalyst of Example 2.
It had a composition represented by the composition formula of BaCoAl ₁₁ O _18.5 .

The BET specific surface area of the catalyst of Example 4 was 15.2 m ² / g.

Example 4 Table 3 shows the results of the activity test conducted on the catalyst in the same manner as in Use Example 1.

Although the catalyst of Example 4 prepared by the alkoxide method had the same composition, the activity was remarkably improved as compared with the catalyst of Example 2 prepared by the solid mixing method, and particularly the activity in the high conversion region was significantly improved.

Example 5 and Comparative Example 2 Instead of cobalt oxide (Co ₂ O ₃ ), chromium oxide (Cr
A catalyst of Example 5 was obtained in the same manner as in Example 1 except that ₂ O ₃ ) was used. The composition of this catalyst is BaCrAl ₁₁ O ₁₉ or BaO.CrO.
_It is expressed as _1.5 · 5.5Al ₂ O ₃ .

Further, the same carrier as that of the catalyst of Comparative Example 1 was impregnated with chromic anhydride and sintered at 1300 ° C. for 5 hours to obtain a catalyst of Comparative Example 2. In this product, 10 wt% of Cr ₂ O ₃ was supported on the carrier BaO · 6Al ₂ O ₃ .

The BET specific surface areas of the catalysts of Example 5 and Comparative Example 2 were 3.0, respectively.
m ² / g and 6.4 m ² / g.

Use Example 4 Use Example 1 for the chromium catalysts of Example 5 and Comparative Example 2
The same test was carried out to compare the activities. The results are shown in Table 4.

In the case of the chromium catalyst, the catalyst of the present invention had excellent activity as compared with the simple impregnated and supported catalyst, as in the case of the cobalt catalyst.

Example 6 and Use Example 5 Barium isopropoxide and aluminum isopropoxide were dissolved in isopropyl alcohol, and an aqueous solution of manganese acetate was added dropwise thereto for hydrolysis. 12
The suspension obtained after the time aging was dried under reduced pressure at 80 ° C., and the obtained powder was pyrolyzed in a hydrogen stream at 400 ° C. for 5 hours and then calcined in a nitrogen stream at 1200 ° C. 6 catalyst was obtained.

The BET specific surface area of the catalyst of Example 6 was 10 m ² / g.

Table 5 shows the results of the methane combustion activity test conducted on the catalyst of Example 6 in the same manner as in Use Example 1.

The catalyst containing Mn as an active ingredient of Example 6 exhibited a remarkably high activity particularly in the low conversion region as compared with the catalyst containing cobalt as an active ingredient of Example 1, but the latter was rather active at a conversion rate of 100%. Was more active.

Examples 7 to 17 and use example 6 BdB _x Al _12-x O _19-α (B _x
Represents Mn, Mn ₂ , Co, Fe, Ni, Cu, Cr, Co _0.5 Mn _0.5 or Cr _0.5 Ni _0.5 ) and an isopropyl alcohol solution of barium alkoxide and aluminum alkoxide and an aqueous solution of acetate or nitrate of each metal B. Was prepared using. However, the firing temperature was 1300 ° C. for each catalyst. Then, the methane combustion activity of these catalysts was measured by the same test method as in Use Example 1.

Further, the cobalt catalyst of Example 10 was further impregnated with palladium nitrate, pyrolyzed at 500 ° C. for 5 hours, and then calcined at 1200 ° C. for 5 hours to obtain a catalyst of Example 17.

 The measurement results are shown in Table 6.

(Effects of the Invention) Thus, according to the present invention, there is provided a heat-resistant catalyst having a significantly low activity even at a high temperature of more than 1200 ° C. and having a significantly low activity.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01J 23/89 B01J 23/64 104M

Claims (17)

(57) [Claims] 1. A composition formula AB _x Al _12-y O _19-α (wherein A is at least one element selected from the group consisting of Ba and Sr, B is Mn, Co, Fe, Ni, Cu and One or more elements selected from the group consisting of Cr, x is a number in the range of about 0.1 to 4, y
Is a number in the range of x to 2x, α is determined by the valence Z of the element B, A heat-resistant catalyst for a catalytic combustion reaction, characterized in that the main component is a composition represented by the formula (1). 2. The heat-resistant catalyst according to claim 1, wherein a platinum group noble metal such as Pt, Ru, Rh, and Pd is supported on the heat-resistant catalyst. 3. The heat-resistant catalyst according to claim 1, wherein the atomic ratio of the element A to the total of the elements B and Al in the heat-resistant catalyst is in the range of about 2.5 to 10: 100. 4. The heat-resistant catalyst according to claim 3, wherein the element A is Ba and the atomic ratio of Ba to the total of the elements B and Al is in the range of about 7 to 10: 100. 5. A refractory catalyst according to claim 1 wherein x is a number in the range of about 0.2-3. 6. A decomposition product of a composite and / or mixed alkoxide in which a part or all of the elements A and Al in the composition represented by the composition formula AB _x Al _12-y O _19-α is used. The heat-resistant catalyst according to claim 1, wherein 7. Hydrolysis formation of a complex and / or mixed alkoxide of a part or all of the elements A and Al in the composition represented by the composition formula AB _x Al _12-y O _19-α. The heat-resistant catalyst according to claim 6, which is a product and / or a thermal decomposition product. 8. The heat resistant catalyst according to claim 6 or 7, wherein the complex and / or mixed alkoxide is an alkoxide having 1 to 4 carbon atoms. 9. A crystal having a layered aluminate structure in which an active element B is incorporated into a crystal lattice, part or all of the composition represented by the composition formula AB _x Al _12-y O _19-α . A heat-resistant catalyst according to range 1. 10. The heat-resistant catalyst according to claim 9, wherein the heat-resistant catalyst is a catalyst for catalytic combustion at a temperature of about 1000 ° C. or higher. 11. A water-soluble or alcohol-soluble aluminum compound, a water-soluble or alcohol-soluble compound of at least one element A selected from the group consisting of Ca, Ba and Sr, and Mn, Co, Fe, Ni, Cu. And a water-soluble or alcohol-soluble compound of at least one element B selected from the group consisting of Cr and Cr, Al: A: B atomic ratio 100: (2.5-10): (0.1-
A method for producing a heat-resistant catalyst for catalytic combustion reaction, which comprises calcining a precipitate or a hydrolysis product and / or a thermal decomposition product from a solution mixed in a ratio of 4) at a temperature of about 900 ° C. or higher. . 12. The heat resistance according to claim 11, wherein a complex and / or mixed alkoxide of an aluminum alkoxide and an alkoxide of element A is hydrolyzed with an aqueous solution of a compound of element B to obtain a hydrolysis product. Method for producing catalyst. 13. The method for producing a heat-resistant catalyst according to claim 12, wherein the complex and / or mixed alkoxide is an alkoxide having 1 to 4 carbon atoms. 14. The method for producing a heat-resistant catalyst according to claim 11, 12 or 13, wherein water is used in the hydrolysis in an amount of about 0.5 times or more the equivalent of water necessary for hydrolyzing the total amount of the alkoxide. 15. The method for producing a heat-resistant catalyst according to claim 11, 12, 13 or 14, wherein the hydrolysis is carried out at a temperature in the range of about 50 to 100 ° C. 16. A method according to claim 10, 11, 12, 13, 14, or 15 in which aging is performed for about 1 hour or more after addition of water for hydrolysis.
A method for producing the heat-resistant catalyst described. 17. The method for producing a heat-resistant catalyst according to claim 11, 12, 13, 14, 15, or 16, wherein the element A is Ba and the element B is Co.