JP2974342B2 - High temperature combustion catalyst and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a high-temperature combustion catalyst and a method for producing the same, and more particularly, to a catalytic combustion type gas turbine combustor and the like. The present invention relates to a high-temperature combustion catalyst body which is desired to have high activity in a high temperature range and a method for producing the same.

(Prior art) In recent years, from the viewpoint of energy saving and resource saving, in a gas turbine combustor for driving a gas turbine or the like,
It is desired to burn the fuel at as high a temperature as possible.

Conventionally, a method of igniting and burning a mixture of fuel and air with a spark plug or the like has been adopted. However, there is a high temperature portion exceeding 2000 ° C. locally in the combustor, and nitrogen oxide (NO. _X ) is produced in large quantities, causing problems such as causing environmental pollution.

In order to solve such a problem, a catalytic combustion system in which a mixture of fuel and air is burned using a catalyst has been proposed. According to this method, uniform combustion of lean fuel is possible, and since the combustion temperature can be increased to about 1500 ° C., which is the upper limit temperature at which NO _X is not formed, application to the gas turbine combustor and the like is promising. ing.

As a catalyst used in this type of catalytic combustion system, γ-alumina (γ-Al ₂ O ₃ ) is applied as an active carrier on a carrier having a certain mechanical strength, and a noble metal is supported by a dipping method. Those manufactured by a method are known. However, this noble metal-based combustion catalyst is said to have a heat resistance temperature of 600 ° C., and has a problem that in a temperature range higher than that, the catalytic activity is rapidly reduced and cannot be used.

The cause of the rapid decrease in the catalytic activity at a temperature of 600 ° C. or higher is considered as follows. First, since the particles of the noble metal-based combustion catalyst on the surface of the carrier are aggregated and coarsened by heat transfer, the surface area of the noble metal-based catalyst is reduced, and the combustion performance is reduced. Second, cracks occur in the Al ₂ O ₃ layer or between the Al ₂ O ₃ and the carrier because γ-Al ₂ O ₃ undergoes a phase transition to α-Al ₂ O ₃ at a temperature of 1000 ° C. or more, The Al ₂ O ₃ layer peels off along with the catalyst metal. Third
In addition, Al ₂ O ₃ itself also sinters, and pores which are gas passages are crushed, so that the catalyst cannot contact the gas and the activity is reduced.

Therefore, the present inventors have prepared a porous carrier layer using alumina or the like as a raw material capable of forming a large number of pores inside when fired from a slurry state, a noble metal catalyst component, a rare earth element, an alkaline earth metal and A first co-catalyst component containing at least one of these oxides, a second co-catalyst component containing at least one of magnesium, silicon and these oxides, and a second co-catalyst component containing at least one of heavy metals and these oxides. Attempts have already been made to produce a high-temperature combustion catalyst supporting the three promoter components using a co-impregnation method or a co-precipitation method.

That is, in the co-impregnation method, an alumina carrier layer is formed by applying a raw material of the porous carrier layer, for example, a slurry of alumina containing a first co-catalyst component to the surface of a carrier substrate, and forming the alumina carrier layer with a noble metal catalyst. The noble metal catalyst component and the second and third co-catalyst components are immersed in a solution containing the components and the second and third co-catalyst components, and are supported on an alumina carrier layer and calcined.

Further, a mixed solution in which the alumina, the noble metal catalyst component, and the first, second, and third cocatalysts (hereinafter, referred to as three cocatalyst components) are dissolved is adjusted, and the acidity (pH) of the solution is adjusted. In the coprecipitation of the alumina and the noble metal catalyst component,
A noble metal catalyst component-containing alumina slurry is generated from the precipitate, and the alumina slurry is applied on a carrier substrate,
A coprecipitation method of drying and calcining, or a mixed solution in which the alumina and the three cocatalyst components are dissolved is prepared, and a noble metal catalyst component having a predetermined average particle size is added to the mixed solution and kneaded, and then the acidity of the solution is adjusted. (PH) is adjusted to co-precipitate the alumina and the three cocatalyst components to obtain an inorganic slurry, and apply the slurry onto a carrier substrate, and then dry and calcine the coprecipitation method. According to this coprecipitation method, particularly the latter coprecipitation method, a large amount of the noble metal catalyst component can be uniformly supported on the carrier substrate, and therefore, a certain large active surface area can be secured.

(Problems to be Solved by the Invention) However, there is still room for improvement in the high-temperature durability and the low-temperature ignitability of the high-temperature combustion catalyst of such a production method.

An object of the present invention has been made in view of such problems, and has a long-lived high-temperature combustion catalyst body having high activity at high temperatures, excellent low-temperature ignitability and high-temperature durability, and a method for producing the same. To provide.

[Constitution of the Invention] (Means for Solving the Problems) As a result of intensive studies to achieve the above object, the present inventors have found that the first co-catalyst component and the component of the porous carrier layer are different from each other. The present invention has been found to have a remarkable effect when the reaction is carried out and the second or third promoter component is attached to the particle surface of the noble metal catalyst component in a larger amount than the first promoter component. It was completed.

That is, the high-temperature combustion catalyst of the present invention comprises a porous carrier layer comprising a noble metal catalyst component, a first promoter component containing at least one of a rare earth element, an alkaline earth metal and an oxide thereof, magnesium, silicon And a second promoter component containing at least one of these oxides, and a third promoter component containing at least one of a heavy metal and these oxides. A powder is produced by reacting the first co-catalyst component with the component of the porous carrier layer, and a powder is produced by adhering the second and third co-catalyst components to the noble metal catalyst component. By mixing both powders, the first co-catalyst component reacts with the component of the porous carrier layer more than the second and third co-catalyst components, and 3 co-catalyst components And wherein the adhered number as compared to the serial first co-catalyst component to the noble metal catalyst component.

The porous carrier layer according to the present invention is not particularly limited as long as it can generate a large number of pores inside when fired from a slurry state and has heat resistance to a high temperature of about 1500 ° C. However, examples thereof include alumina, titania, zirconia, aluminum titanate, and silica.

This porous carrier layer is often used by being carried on the surface of a carrier substrate, as the carrier substrate, if it has stable properties even in a high-temperature oxidizing atmosphere at about 1500 ° C.
There is no particular limitation, for example, cordierite,
Ceramic carriers such as mullite, α-alumina, zirconia, titania and the like can be mentioned. The shape of the carrier substrate is not particularly limited as long as it is a shape usually used as a catalyst, and examples thereof include a pellet shape and a honeycomb shape.

Examples of the noble metal catalyst component supported on the porous carrier layer include noble metals such as palladium, platinum, and rhodium or a mixture thereof, and palladium is particularly desirable. The supported amount of the noble metal catalyst component is appropriately determined according to the conditions under which it is used. For example, the content is preferably 10% by weight or more based on the porous carrier layer, more preferably 20% by weight or more based on the porous carrier layer, and still more preferably 30% by weight or more. As for the upper limit of the supported amount of the catalyst component, a smaller amount is better for economic reasons, preferably 60.
% Or less.

Examples of the first co-catalyst component include rare earth elements such as lanthanum, cerium, praseodymium, and neodymium, or alkaline earth metals such as barium, strontium, and calcium, or oxides thereof. (La ₂ O ₃ , BaO) or the like is preferably used. The supported amount of the first co-catalyst component is preferably 0.05 to 1 in atomic ratio to alumina, more preferably 0.2 to 0.4. The first co-catalyst component reacts with a carrier layer such as alumina at a high temperature to form perovskite or spinel.

Examples of the second co-catalyst component include magnesium, silicon and their oxides, and an oxide of magnesium (MgO) is preferably used. This second
The supported amount of the co-catalyst component is preferably 0.5 to 1.5 in atomic ratio with respect to the noble metal catalyst component such as palladium and platinum.

Examples of the third co-catalyst component include heavy metals such as nickel, zirconium, cobalt, iron, and manganese and oxides thereof, and nickel oxide (NiO)
Is preferably used. The supported amount of the third co-catalyst component is preferably 0.5 to 1.5 in atomic ratio with respect to the noble metal catalyst component such as palladium and platinum.

The distance between the third promoter component and the noble metal catalyst component is 10
The angle is preferably 0 ° or less, and if it is more than 0 °, the function is not sufficiently exhibited.

Since the second and third co-catalyst components of the present invention are attached to the particles of the noble metal catalyst component, the particle diameter of these catalyst components is preferably small.

If the amount of the second or third promoter component is too large, the surface of the noble metal catalyst component is covered and the function of the noble metal catalyst component is not exhibited. Is set in consideration of this.

The method for producing a high-temperature combustion catalyst according to the present invention comprises the steps of: reacting a first co-catalyst component containing at least one of a rare earth element, an alkaline earth metal, and an oxide thereof with a component of a porous carrier layer; And a second co-catalyst component containing at least one of magnesium, silicon and these oxides, and a third co-catalyst component containing at least one of heavy metals and these oxides. A second step of producing a powder attached to the particles;
And a third step of mixing the powder generated in the step and the powder generated in the second step.

 Hereinafter, this method will be described more specifically.

First, as a first step, the components of the porous carrier layer are immersed in an aqueous solution in which the first promoter component is dissolved, and then dried and fired. At this time, the starting material of the porous carrier layer may be an oxide, a hydroxide, a slurry, or the like. When the porous carrier layer is made of alumina, the first co-catalyst component is added to an aqueous solution of aluminum, and the slurry is precipitated by adjusting the pH of the two components to obtain a powder of alumina in the first step. Powder can also be obtained.

The particle size of the noble metal catalyst component particles used in the second step is set according to the temperature at which the catalyst is used. For example, when the operating temperature of the catalyst is 1000 ° C., the particle size of the noble metal catalyst component particles is about 1 μm. However, the average particle size of the noble metal catalyst component particles is set to be larger than the average pore size of the alumina layer, and it is desirable that the particle size distribution and the pore size distribution do not overlap each other. The noble metal catalyst component particles are added to an aqueous solution containing the second and third cocatalyst components, and the second and third cocatalysts are added to the surface of the noble metal catalyst component particles by a wet reduction method, an electroless plating method, an immersion firing method, or the like. Precipitate the components. The order of the deposition is preferably simultaneous or the order of the third promoter component after the second promoter component. Further, if a noble metal catalyst component coated powder obtained by applying a noble metal catalyst component on inorganic particles is used as the noble metal catalyst component particles, more preferable results can be obtained. The inorganic particles are preferably oxides, particularly zirconia. If the second and third co-catalyst components can be uniformly dispersed on the surface of the noble metal catalyst component, a different method from the above method may be adopted depending on the raw materials and properties of the second and third co-catalyst components. May be.

Next, as a third step, the powder obtained in the first step and the powder obtained in the second step are mixed. To the mixture obtained by this mixing, an appropriate amount of a binder is added and water is added to form a slurry. The slurry is kneaded well, then adhered to a carrier substrate, dried, and calcined to form a catalyst. A high-temperature combustion catalyst used in a combustion type gas turbine combustor or the like can be manufactured. The supported amount of the noble metal catalyst component particles is preferably 50 g / or more per unit volume of the supported base material, and more preferably 100 g / or more.

(Operation) The sintering of the porous carrier layer buries the noble metal catalyst component and lowers the function of the catalyst, but the first promoter component reacts with the porous carrier layer at a high temperature to form a perovskite (or spinel) hard. It is believed that it functions to form a membrane and prevent sintering of the porous carrier layer. The fact that the first promoter component has been reacted with the raw material of the porous carrier layer is effective for improving the performance of the catalyst.

In addition, the aggregation of the noble metal catalyst component causes a decrease in the active surface area of the noble metal catalyst component and lowers its activity.
The co-catalyst component is considered to function to prevent the noble metal catalyst component from aggregating at a high temperature, and attaching the second co-catalyst component to the noble metal catalyst component particles is effective for improving the performance of the catalyst.

Oxygen is activated on the surface of the third promoter component and comes into good contact with the noble metal catalyst component. That is, the third promoter component is considered to have a function of supplying oxygen in the air at a high temperature to the surface of the noble metal catalyst component. Therefore, the third promoter component should be close to or attached to the noble metal catalyst component. Is effective for improving the performance of the catalyst.

Then, once a powder is produced by reacting the first promoter component with the raw material of the porous carrier layer, a powder is produced by adhering the second and third promoter components to the noble metal catalyst component, After this, both powders are mixed, so
The second and third co-catalyst components can be located in the interparticle arrangement according to their respective functions as described above with respect to the noble metal catalyst component and the porous carrier layer. Due to the effective use of the co-catalyst component, each of the first, second, and third co-catalyst components is prevented from being wasted, and
Excess amounts of the second and third cocatalyst components react with the alumina, and do not lower the heat resistance of the alumina as described above.

(Example) Example 1 (1) Production of high temperature combustion catalyst body 721 g of aluminum nitrate nonahydrate and lanthanum nitrate hexahydrate 53
While stirring the aqueous solution in which g was dissolved at 60 ° C., an appropriate amount of potassium carbonate was added to adjust the pH finally to 9.0, and alumina hydroxide was precipitated on nuclei. At room temperature
Aged for 24 hours, washed and dried at 150 ° C for 6 hours, 900 ° C
For 5 hours to produce an alumina powder containing a lanthanum oxide.

Next, an aqueous solution in which 100 g of palladium powder having an average particle size of 1 μm, 155 g of nickel nitrate hexahydrate and 128 g of magnesium nitrate hexahydrate were dried at 150 ° C., primary calcination at 400 ° C. for 2 hours, and 1000 ° C. 5 hours of secondary firing, 2nd and 3rd
A palladium powder to which the promoter component was attached was obtained.

Next, the alumina powder 120 g and the palladium powder 16
After mixing 0 g and the binder 5 g, a small amount of water was added to form a slurry, and 10 g of the slurry was applied to a honeycomb carrier (corresponding to cordierite 30 mm in diameter, 30 mm in length, 200 cells) and heated at 150 ° C.
And baked in air at 900 ° C. for 3 hours. At this time, the carried amount of the palladium powder is 100 g /.

(2) Evaluation of High-Temperature Combustion Catalyst The high-temperature combustion catalyst obtained through the above manufacturing process was incorporated into a simulated apparatus for a catalytic gas turbine combustor, and its combustion characteristics were evaluated. The combustion conditions at this time are as follows:
The combustion characteristics (ignition temperature and combustion efficiency) of methane after 5,000 hours of combustion were measured at m / s, a combustion concentration of 3%, and a catalyst amount of 30 cc, and the results are shown in Table 1.

Examples 2 to 30 Table 1 shows the types and amounts of the three promoter components used.
A high-temperature combustion catalyst was manufactured and subjected to an evaluation test in the same manner as in Example 1 except that the temperature was changed as shown in Example 1. Table 1 shows the results.
It was shown to.

Comparative Examples 1 to 30 Table 1 shows the types and amounts of the three promoter components used.
The evaluation test of the high-temperature combustion catalyst was carried out in the same manner as in Example 1 except that a high-temperature combustion catalyst was produced by the coprecipitation method in the same manner as shown in Table 2 and the results are shown in Table 2.

Examples 31 to 41 High-temperature combustion catalysts were prepared in the same manner as in the above example, except that palladium-coated powder (average particle size: about 1 μm) was used as the palladium powder, and the material of the core was changed as shown in Table 3. Was manufactured, and the same evaluation test was performed. The results are shown in Table 3. The palladium-coated powders of Examples 31 to 39 were prepared by an electroless plating method, and the palladium-coated powders of Examples 40 and 41 were manufactured by a wet reduction method and an immersion firing method.

[Effects of the Invention] As is clear from the above description, the high-temperature combustion catalyst manufactured by the method for manufacturing a high-temperature combustion catalyst according to the present invention is:
It has high activity at high temperatures, excellent low-temperature ignitability and high-temperature durability, and has a long life, so that its industrial value is extremely large.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FIF23D 14/18 B01J 23/64 104M (72) Inventor Yamanaka Ya 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Research Institute Office (72) Inventor Hiroshi Furuse 2-4-1 Nishi-Atsujigaoka, Chofu-shi, Tokyo Tokyo Electric Power Co., Inc. (72) Inventor Toshiaki Tsuchiya 2-4-1, Nishi-Atsujigaoka, Chofu-shi, Tokyo Tokyo Electric Power Co., Inc. 56) References JP-A-63-190644 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B01J 21/00-38/74 F23C 11/00 F23D 14/18

Claims (4)

(57) [Claims] 1. A powder in which a first co-catalyst component containing at least one of a rare earth element, an alkaline earth metal and an oxide thereof is supported on a porous carrier layer component, and magnesium, A mixed powder of: a second co-catalyst component containing silicon and at least one of these oxides; and a powder having a third co-catalyst component containing heavy metal and at least one of these oxides adhered thereto. A high-temperature combustion catalyst body characterized by the following. 2. The high-temperature combustion catalyst according to claim 1, wherein the amount of the noble metal catalyst component carried is not less than 10% by weight and not more than 60% by weight with respect to the porous carrier layer component. 3. The amount of the first co-catalyst component carried is 0.05 to 1 in atomic ratio with respect to the porous carrier layer component.
The supported amount of the promoter component is 0.5 to 1.5 in atomic ratio with respect to the noble metal catalyst component, and the supported amount of the third promoter component is
2. The high temperature combustion catalyst according to claim 1, wherein the atomic ratio of the catalyst component to the noble metal catalyst component is 0.5 to 1.5. 4. A first step of producing a powder by reacting a first co-catalyst component containing at least one of a rare earth element, an alkaline earth metal and an oxide thereof with a component of a porous carrier layer. A powder in which a second co-catalyst component containing at least one of magnesium, silicon and these oxides and a third co-catalyst component containing at least one of heavy metals and these oxides are attached to noble metal catalyst component particles. High-temperature combustion, comprising: a second step of generating; and a third step of mixing the powder generated in the first step and the powder generated in the second step. A method for producing a catalyst body.