JPH0512021B2 - - 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 300 to 1500°C.
The present invention relates to a combustion catalyst for gas turbines having high activity.

[Technical background of the invention and its problems]

In recent years, with the depletion of petroleum resources and the like, in order to use energy resources efficiently, for example, in gas turbines and the like, it is desired to burn fuel at as high a temperature as possible.

However, in the conventional combustion method, a mixture of fuel and air is ignited using a spark plug or the like to cause gas phase combustion, so there are parts of the combustor with high temperatures exceeding 2000℃. I will do it. In this case, in the high temperature section,
It is known that large amounts of nitrogen oxides (NO _x ) are produced, 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 _x is not generated.

When this catalytic combustion method is applied to a gas turbine, the combustion catalyst used is required to have two contradictory characteristics. That is, 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. The flaming mixture is then cooled to about 1200°C and then 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.

Such combustion catalysts for gas turbines include:
Noble metal catalysts having a structure as illustrated in FIG. 1 are known. That is, γ is applied to the surface of a heat-resistant support 1 such as α-alumina that has a certain mechanical strength.
- A porous layer 2 of an active carrier such as alumina is provided, and one or more kinds of noble metal particles 3 are attached and supported on the surface of the carrier layer 2 by a dipping method or the like. In this case, when providing the carrier layer 2, a noble metal catalyst source may be mixed with the material and the surface of the heat-resistant carrier 1 may be coated with this mixture. In any case, the noble metal having catalytic ability is uniformly supported on the surface of the carrier layer 2, or is uniformly dispersed in the carrier layer 2 with a portion exposed on the surface.

In particular, in this type of catalyst, platinum (Pt), palladium (Pd), or an alloy thereof is often used as a noble metal. In particular, catalysts that support Pt and Pd in a mixed state are known.

However, catalysts that support a mixture of Pt and Pd have the following problems. That is, it does not exhibit high activity over the entire temperature range from low to high temperatures.

Therefore, such a catalyst is suitable for temperatures between 300℃ and 1500℃
It is not necessarily effective as a combustion catalyst for gas turbines that require high activity even in a wide temperature range of °C.

[Purpose of the invention]

The present invention eliminates the drawbacks of conventional combustion catalysts for gas turbines as described above, and provides a gas turbine with a novel structure that has excellent ignition performance at low temperatures and is highly active even in the temperature range of 300 to 1500 degrees Celsius. The purpose is to provide combustion catalysts for

[Summary of the invention]

The present inventors have conducted extensive research to solve the above-mentioned problems with catalysts supporting Pt and Pd, and have found that Pd has excellent activity in the low temperature range of 600℃ or less when natural gas is used as fuel. They discovered that Pt exhibits excellent activity in the high temperature range of 600℃ or higher, and also found that when Pt and Pd are mixed in the active carrier layer, they are located close to each other, so it is difficult to use during use. Pt and Pd in the catalyst transfer heat and finally
It was discovered that a Pt/Pd alloy is formed which has lower activity at low temperatures than Pd. From these facts, if Pt and Pd are present in the active carrier layer in a state where they are separated from each other rather than in a mixed state, alloying will not occur during use.
Based on the idea that each activity can be effectively utilized, we have developed the combustion catalyst for gas turbines of the present invention.

That is, the combustion catalyst for gas turbines of the present invention comprises a heat-resistant carrier, an active carrier layer formed by coating the surface of the carrier, and platinum and palladium dispersed and supported within or on the carrier layer. A combustion catalyst for a gas turbine consisting of particles, characterized in that the platinum and palladium particles are not mixed and dispersed in or on the carrier layer, but are present in separate layers. shall be.

An example of the catalyst of the present invention is shown in FIG. In the figure, 1 is a heat-resistant carrier. The heat-resistant carrier used in the present invention may be any carrier as long as it has stable properties even in a high-temperature oxidizing atmosphere of about 1500°C, and specific examples thereof include cordierite, mullite, α- Examples include ceramic carriers made of 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, and examples thereof include pellet shape, honeycomb shape, etc.

2 is an active carrier layer formed by coating the surface of the heat-resistant carrier 1, and is a layer made of porous ceramics such as γ-alumina, α-alumina, and zirconia, or a layer containing various rare earth elements therein. ,
The present invention is not particularly limited.

4 and 5 are Pd and Pt particles, respectively. In the present invention, Pd and Pt are not present in a mixed manner on the surface of the carrier layer 2, but each metal is separately present in a layer-like manner spread over the catalyst surface at certain intervals in the direction perpendicular to the surface of the carrier 1. Its greatest feature is that it exists.

Pd and Pt can be supported on the active carrier layer 2 in the following manner. First method. First, a carrier layer material such as alumina sol or γ-alumina is mixed with fine powder of Pd or PdO or fine powder of Pd salt, and the surface of the carrier 1 is coated with a slurry of this mixture, and then dried and fired. A carrier layer is formed and Pd4 is supported thereon. Pd used at this time
The salts include palladium chloride, PdCl ₂ (NH ₃ ) ₂ ,
Examples include (NH ₄ ) ₂ PdCl ₄ and Pd(OH) ₂ .

Next, this carrier layer is coated with a slurry of a mixture consisting of a fine powder of Pt or PdO, or a fine powder of its salt, and a carrier layer material such as alumina sol or γ-alumina, and then dried and fired. Examples of the Pt salt used include hexachloroplatinic acid, platinum chloride, and tetrachloroplatinic acid.

In this way, as shown in FIG. 2, a carrier layer is formed in which Pd is supported on the inside of the carrier layer 2, and Pd is supported on the outside at a certain interval.

Second method. An active carrier layer 2 is formed on the surface of the carrier 1 using only a slurry of, for example, alumina sol or γ-alumina. Next, this is immersed in, for example, a palladium chloride solution of a predetermined concentration to form an active carrier layer 2.
Pd is supported on the surface. Thereafter, an active carrier layer is formed thereon again in the same manner as above, and it is immersed in, for example, a hexachloroplatinum solution to support Pt on the second active carrier layer. Thus, the carrier,
a first active carrier layer, a layer of Pd, a second active carrier layer,
Pt layers are formed at predetermined intervals. That is, in this case as well, Pd and Pt exist without being close to each other. In this case, since the active carrier layer is porous, the fuel-air mixture can also come into contact with the Pd inside.

In addition, in the two methods, the active carrier layer is
It goes without saying that no inconvenience will occur even if the order of existence of Pd and Pt is reversed.

[Embodiments of the invention]

(1) Preparation of catalyst A slurry () was prepared by dispersing 100 g of alumina sol, 7 g of cerium nitrate, and 20 g of an aqueous palladium chloride solution in an appropriate amount of water. Also, alumina sol
A slurry () was prepared by dispersing 100 g of cerium nitrate, 7 g of cerium nitrate, and 15 g of hexachloroplatinic acid solution in an appropriate amount of water.

A cordierite honeycomb carrier with an inner diameter of 25 mm and a length of 150 mm was coated with slurry (), and after drying it was
Calcined at ℃. Further, this was coated with slurry (), dried and then fired at 1000°C. This was designated as catalyst A.

Catalyst B is a similar honeycomb carrier coated with slurry (), dried and calcined at 1000℃, and catalyst C is a mixture of slurry () and slurry (). Catalyst D was obtained by coating with slurry, drying, and firing.

Among these catalysts, catalyst A is the catalyst of the present invention.

(2) Effect of catalyst A methane gas flow with a concentration of 3% was introduced into the four types of catalysts at an inlet flow rate of 20 m/sec, and the methane conversion rate at each catalyst temperature was measured. The results are shown in Figure 3. As is clear from the figure, catalyst A
(Curve a) and Catalyst D (Curve d) had a large methane conversion rate in the low temperature range and the gas was completely combusted at 500°C or higher.
Catalyst B (curve b) converts methane gas from a low temperature range, but does not completely burn even at temperatures above 600°C.
Catalyst C (curve c) hardly converted methane at temperatures below 500°C, but completely burned at temperatures above 600°C.

Next, these four types of catalysts were heated in air for 1000 min.
℃ for 30 hours, and then used to measure the methane conversion rate under the same conditions as above. The results are shown in Figure 4. Catalyst A (curve a') had a high methane conversion rate in the low temperature range and was completely combusted at temperatures above 520°C. Catalyst B (curve b') converts methane from the low temperature range.
Even at high temperatures of over 600℃, the gas was not completely combusted. Catalyst C (curve c') hardly converted methane in the low temperature range below 550°C;
The gas was completely combusted at 620℃. And catalyst D
(Curve d') is completely different from curve d in Figure 3,
Almost no methane was converted in the low temperature range of 540°C, and methane was completely combusted for the first time in the high temperature range of 650°C or higher.

〔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 it is possible to burn it without generating NO _x etc., so it is useful without causing problems such as environmental pollution.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams each schematically showing the surface portion of a combustion catalyst for a gas turbine, with FIG. 1 being a conventional one and FIG. 2 being an inventive one. Figure 3 is a diagram showing the relationship between the inlet temperature and methane conversion rate of the catalyst of the example, and Figure 4 shows the relationship between the catalyst of the example and the methane conversion rate in air.
30C is a diagram showing the relationship between inlet temperature and methane conversion rate after heating for 30 hours. DESCRIPTION OF SYMBOLS 1... Heat-resistant carrier, 2... Active carrier layer, 3... Precious metal particles, 4... Pd, 5... Pt.

Claims (1)

[Claims] 1. A gas consisting of a heat-resistant carrier, an active carrier layer formed by coating the surface of the carrier, and platinum and palladium particles dispersed and supported within or on the carrier layer. A combustion catalyst for a gas turbine, characterized in that the platinum and palladium particles are not dispersed in a mixed manner within or on the surface of the carrier layer, but are present in separate layers. combustion catalyst.