JPH0215254B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a combustion catalyst for a gas turbine, and more particularly, in a temperature range of about 800 to 1500°C,
The present invention relates to a combustion catalyst for gas turbines having high activity and long life. [Technical background of the invention and its problems] In recent years, with the depletion of petroleum resources, etc., in order to use energy resources efficiently, it is desirable to burn fuel at as high a temperature as possible in, for example, gas turbines. It is rare. However, in the conventional method, a mixture of fuel and air is ignited and combusted using a spark plug, etc.
There are high temperature areas exceeding 2000℃. It is known that a large amount of nitrogen oxides (NOx) is generated in this high temperature section, causing problems such as environmental pollution. In order to solve these problems, a catalytic combustion method has been proposed in which a mixture of fuel and air is combusted using a catalyst. According to this combustion method, uniform combustion is possible and the combustion temperature can be increased to about 1500° C., which is the upper limit temperature at which no NOx is generated. However, when the above-mentioned catalytic combustion method is applied to a gas turbine, the combustion catalyst is required to have two contradictory characteristics, namely, low-temperature ignitability and heat resistance. In gas turbines currently in use, combustion air is preheated to about 300°C and then introduced into the combustor using a compressor blower. After the flame-combusted mixture is cooled to around 1200℃,
It is sent into the turbine. Therefore, when a combustion catalyst filling part is installed in a gas turbine combustor, the combustion catalyst is capable of igniting fuel gas at a temperature of about 300°C and can withstand temperatures of about 1200°C caused by the combustion gas. will be required. As the combustion catalyst for the gas turbine described above, it is possible to use a noble metal catalyst such as platinum (Pt). Such a noble metal catalyst is, for example, as shown in FIG. 1, a γ-
It is known that an alumina (γ-Al ₂ O ₃ ) coating layer 2 is provided and a noble metal catalyst 3 is supported by a dipping method or the like. However, for such noble metal catalysts, those whose ignition temperature is usually as low as 300°C are said to have a heat resistance temperature of 600°C or less, and their catalytic activity rapidly decreases at higher temperatures. This has the problem that it is not suitable for practical use. The reason why the catalyst activity rapidly decreases at temperatures above 600°C can be considered as follows. First, the noble metal particles on the surface of the carrier aggregate and become coarse due to heat transfer, which reduces the catalyst surface area and lowers the combustion performance. And secondly,
Since γ-Al ₂ O ₃ undergoes a phase transition to α-Al ₂ O ₃ at temperatures from around 1000°C to above, cracks occur within the Al ₂ O ₃ layer or between Al ₂ O ₃ and the support. This is thought to be caused by the Al ₂ O ₃ layer peeling off together with the catalyst metal. Therefore, in order to improve the heat resistance of noble metal combustion catalysts, we improved the γ-Al ₂ O ₃ layer and added γ-Al ₂ O ₃
Attempts have been made to strongly adsorb the Pt particles on the layer to Al ₂ O ₃ to prevent agglomeration due to heat transfer, and to prevent the formation of cracks by preventing α-ization of the γ-Al ₂ O ₃ layer. As a result, by adding metals to the γ-Al ₂ O ₃ layer, heat-resistant combustion catalysts that can be used up to around 800°C have been developed in some automotive catalysts. [Object of the invention] The object of the present invention is to have excellent low-temperature ignition characteristics, and
An object of the present invention is to provide a combustion catalyst for a gas turbine that has high activity and long life even in a temperature range of 800 to 1500°C. [Summary of the Invention] In view of the above-mentioned current situation, the present inventors have devised
As a result of intensive studies on combustion catalysts that can be used even at high temperatures, we found that metal catalysts of palladium (Pd) and cerium (Ce) were found in the γ-Al ₂ O ₃ particles that make up the γ-Al ₂ O ₃ layer. The inventors have discovered that heat resistance can be significantly improved by embedding a portion of the particles, and have completed the present invention. That is, the combustion catalyst for a gas turbine of the present invention includes a heat-resistant carrier; a γ-alumina (γ-Al ₂ O ₃ ) coating layer provided on the carrier; and a group of metal catalyst particles in a gas turbine combustor. The metal catalyst particle group consists of 4 g or more of palladium (Pd) per combustion catalyst and 1 to 10% by weight of cerium (Ce) based on the γ-alumina of the coating layer, and at least It is characterized in that some of the particles are partially embedded in the γ-alumina particles constituting the γ-alumina coating layer. In the following, the invention will be explained in more detail. The heat-resistant carrier used in the present invention is 1500
Any material may be used as long as it has stable properties even in a high-temperature oxidizing atmosphere of about °C.
Specific examples of these include ceramic carriers such as cordierite, mullite, α-alumina, zirconia spinel, and titania. The shape of the carrier is not particularly limited as long as it is a shape normally used as a catalyst, for example, pellet-like,
Examples include honeycomb shapes. The γ-Al ₂ O ₃ coating layer used in the present invention has catalytic activity itself. Then, it is formed by coating the surface of the heat-resistant carrier. The metal catalyst used in the present invention is Pd and
At least some of the particles of the metal catalyst particle group are partially embedded in the γ-Al ₂ O ₃ particles constituting the γ-Al ₂ O ₃ coating layer, and the metal catalyst particles Most of the particles in the group are γ−
It is preferable that it is partially embedded in the γ-Al ₂ O ₃ particles constituting the Al ₂ O ₃ coating layer. Metal catalyst particles are γ
-By being partially embedded in the γ-Al ₂ O ₃ particles constituting the Al ₂ O ₃ coating layer, the heat transfer of the respective metal catalyst particles of Pd and Ce is inhibited, and the decrease in catalytic activity is prevented even at high temperatures. It becomes small. The amount of Pd used in the present invention is 4 g/or more based on the total amount of the catalyst. If the amount of Pd added is less than 4 g/min, the desired catalytic activity cannot be obtained. Ce used in the present invention is γ of the coating layer.
- added in an amount of 1 to 10% by weight relative to Al ₂ O ₃ ,
It is preferably 2 to 5% by weight. γ _{- Al2O3}
If the amount of Ce contained in the coating layer is less than 1% by weight, no improvement in heat resistance will be observed;
If the value exceeds 1, a large amount of Ce oxide precipitates at the grain boundaries of Al ₂ O ₃ and the strength of the γ-Al ₂ O ₃ coating layer decreases. The above-mentioned combustion catalyst for gas turbine of the present invention includes:
For example, it can be manufactured as follows. First, predetermined amounts of Pd and Ce are added to an alumina coating composition consisting of alumina sol or γ-Al ₂ O ₃ in the form of metal salts such as chlorides or nitrates of these metals. Next, the above composition is mixed using, for example, a ball mill. The coating liquid obtained in this way is poured onto a heat-resistant carrier, or
Alternatively, the heat-resistant carrier is coated by an operation such as immersing it in a coating liquid, sufficiently dried at room temperature, and then baked at, for example, 650° C. for about 3 hours. The metal catalyst particle group in the γ-Al ₂ O ₃ layer in the gas turbine combustion catalyst of the present invention thus obtained is composed of the gaps between the γ-Al ₂ O ₃ particles constituting the γ-Al ₂ O ₃ layer, etc. , and at least some of the metal catalyst particles are partially embedded in the γ-Al ₂ O ₃ particles. That is, γ−
There are always particles that are partially buried within the Al ₂ O ₃ particles. This state cannot be obtained by conventional methods, such as a method in which a γ-Al ₂ O ₃ layer is provided and then a metal catalyst is supported by a dipping method or the like. In the case of the conventional method, the metal catalyst particles are the γ-Al ₂ O ₃ layer.
It only exists in the gaps between Al ₂ O ₃ particles,
It is simply supported on the surface of the γ-alumina particles. Furthermore, the combustion catalyst for a gas turbine of the present invention can be obtained by firing at 550° C. for about 3 hours in a hydrogen atmosphere, for example. The reason why the gas turbine combustion catalyst of the present invention has excellent heat resistance is not clear, but it can be considered as follows. That is, as shown in FIG. 2, at least some of the particles of the noble metal catalyst 3 are partially embedded in the γ-Al ₂ O ₃ particles constituting the γ-Al ₂ O ₃ coating layer 2. It is thought that the heat transfer of the noble metal catalyst particles is inhibited. In addition, Ce partially embedded in the γ-Al ₂ O ₃ particles constituting the γ-Al ₂ O ₃ coating layer increases the α- of γ-Al ₂ O ₃ .
Because it has the effect of delaying the formation of Al ₂ O ₃ and refining the grain boundaries of the γ-Al ₂ O ₃ coating layer, it is thought that the generation and propagation of cracks due to the high heat of the combustion catalyst are prevented. It will be done. [Examples of the Invention] Example 1 An alumina coating composition having the composition shown below was prepared. Alumina sol (solid content 80%) 125g Cerium nitrate (3g as metallic cerium)
8.3 g Palladium chloride 10 g The above composition was mixed at room temperature for 2 hours using a ball mill to obtain an alumina coating composition. Next, all of the alumina composition was applied to a cordierite honeycomb carrier (200 cells per square inch, carrier capacity: 1) by pouring a liquid in which the alumina coating composition was dispersed in water, and then the alumina composition was coated at room temperature for about It was dried for one day. This honeycomb-shaped carrier was fired at 650°C for 3 hours, and then fired at 550°C for 3 hours in a hydrogen atmosphere to obtain a combustion catalyst (A) for a gas turbine according to the present invention. Example 2 Using the same method as in Example 1, changing the amounts of Pt and Ce added to the alumina coating composition,
Six types of gas turbine combustion catalysts (B) to (G) as shown in the table were prepared. Comparative Example At the same time, as a comparative example, the amounts of Pd and Ce added were set outside the range of the present invention as shown in the table (a) to (c)
Three types of combustion catalysts for gas turbines were prepared in the same manner as in the examples. In addition, commercially available catalysts (d) and (e) in which Pd was supported on _three layers of γ-Al ₂ O were prepared as comparative products. Example 3 The combustion characteristics of the seven types of gas turbine combustion catalysts obtained in Examples 1 and 2 and the five types of combustion catalysts of Comparative Examples were evaluated using a flow system test device. The test conditions were: gas flow rate: 5/min, combustion gas concentration: methane (CH ₄ ) 1%, catalyst amount: 10 cc, space velocity: 3×10 ⁴ hr ^-1 , and catalyst temperature: 300°C.
The initial activity of the catalyst was measured. The results are shown in the table. Next, each of the above combustion catalysts was placed in a heat treatment furnace and heat treated at 1200° C. for 50 hours, and then the combustion characteristics of each were evaluated in the same manner as above.
The results are shown in the table as the catalyst activity retention rate (%) relative to the initial activity of the catalyst.

〔Effect of the invention〕

The combustion catalyst for gas turbines of the present invention has significantly improved heat resistance while maintaining low-temperature ignitability compared to conventional noble metal-based combustion catalysts.
Therefore, it is possible to save and use energy efficiently, and since combustion is possible without generating NOx or the like, it does not cause problems such as environmental pollution.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the structure of a conventional noble metal combustion catalyst, and FIG. 2 is a schematic diagram showing the structure of a gas turbine combustion catalyst according to the present invention. 1...Heat-resistant carrier, 2...γ-alumina coating layer, 3...Precious metal catalyst.

Claims (1)

[Claims] 1. A combustion catalyst for a gas turbine comprising a heat-resistant carrier; a γ-alumina (γ-Al ₂ O ₃ ) coating layer provided on the carrier; and a group of metal catalyst particles, comprising: The group consists of 4 g or more of palladium (Pd) per combustion catalyst and 1 to 10% by weight of cerium (Ce) based on the γ-alumina of the coating layer, and at least some particles of the metal catalyst particle group A combustion catalyst for a gas turbine, characterized in that the γ-alumina coating layer is partially embedded in γ-alumina particles constituting the γ-alumina coating layer.