JPS5952529A - High temperature combustion catalyst - Google Patents

Abstract

PURPOSE:To enhance the heat resistance of the titled catalyst, by adding a metal such as Ce, La, Sr, Sn, Zr and Mg or the like and ceramic whiskers to a gamma- Al2O3 layer. CONSTITUTION:5-30wt% metal such as Ce, La, Sr, Sn, Zr and Mg or the like and 1-30wt% ceramic whiskers comprising SiC, SiO2, Al2O3 or the like are added to an alumina coating composition comprising gamma-Al2O3. Subsequently, said composition is ground by a ballmill or the like and the obtained liquid coating composition is applied to a heat resistant carrier by operation for flowing the same onto said carrier or the like and the coated carrier is baked at a room temp. -650 deg.C after drying.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to high temperature combustion catalysts, and more particularly to
It relates to a high temperature combustion catalyst with high activity and long life in the temperature range from 0C to 1500 t:'.

[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, since the current method uses a spark plug or the like to ignite and burn a mixture of fuel and air, there are parts of the combustor with high temperatures exceeding 2000C. 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 single solvent. According to this combustion method, uniform combustion is possible and the upper limit temperature at which no NOx is generated is 1500℃.
The combustion temperature can be raised to about C.

Currently, platinum (
Pt)-based noble metal catalysts are known.

Such a noble metal combustion catalyst, for example, as shown in Fig. 1, is made of γ-alumina (γAJ20s) 2 as an active carrier on a carrier 1 having a certain 4U41 strength.
was applied, and further a noble metal 3 was supported using a dipping method. Note that Figure 1 is a cross-sectional view of the catalyst body, and Figure 2 is a cross-sectional view of the catalyst body.
The figure is a plan view of the surface.

However, the above-described noble metal combustion catalyst has the problem that its allowable temperature limit is usually said to be 600C, and that the catalyst activity rapidly decreases in a temperature range higher than that, making it unusable.

The reason why the catalyst activity rapidly decreases at temperatures above 600C can be considered as follows. First, the first
Second, the noble metal particles on the surface of the carrier aggregate (due to heat transfer) and become coarse, reducing the catalyst surface area and deteriorating combustion performance. Second, since γ-A,03 undergoes a phase transition to α-M,03 at temperatures around 1000 U or higher, 1, υ, 03 or 20. This is thought to be due to cracks occurring between the AjtOs layer and the support, and the AjtOs layer peeling off together with the catalyst metal.

Therefore, in order to improve the heat resistance of the Kikai-based combustion catalyst, the r+, υ, 01 layer was improved, and γ-A, /! 203 layer on the pt core particles A71,0. γ-AJ20. is strongly adsorbed to prevent agglomeration due to heat transfer. Attempts have been made to prevent the occurrence of cracks by preventing N from becoming alpha.

As a result, due to the addition of metal to the r − )J*Os layer.

In some automobile catalysts, heat-resistant combustion catalysts that can be used up to around 500C have been developed.

[Purpose of the invention]

An object of the present invention is to provide a high temperature combustion catalyst having high activity and long life even in the temperature range of about 800 to 1500 t:'.

[Summary of the invention]

In view of the above-mentioned current situation, the inventors of the present invention have conducted extensive studies on catalysts that can be used at high temperatures of 5ooc or higher, and have found that r-7u203I? 4 to Ce s L a bS
The present invention has been completed based on the discovery that heat resistance can be significantly improved by adding at least one metal selected from the group consisting of Zr, Sn, Zr, and Mg and a ceramic whisker. It arrived.

Namely, the high temperature combustion catalyst of the present invention has a heat-resistant carrier; cerium (Ce), lanthanum (La),
A coating of r-alumina (r-2υ, 0.) containing at least 11 ft of metal and ceramic whiskers selected from the group consisting of strontium (Sr), tin (Sn), zirconium (Zr) and magnesium (Mg). layer; and platinum (Pt) supported on the γ-alumina coating layer.
and/or palladium (Pd).

In the following, the invention will be explained in more detail.

The heat-resistant carrier used in the present invention is:

Any material may be used as long as it has stable properties even in a high temperature oxidizing atmosphere of about 1500 t:
Specific examples of these include cordierite, mullite, α
- Ceramic carriers such as aluminum, mina, zirconia spinel, titania, etc. can be mentioned. 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 pellets, honeycomb shapes, and the like.

The r-Aj203 phase containing metal and ceramic whiskers used in the present invention functions as an active carrier. r The amount of the metal added to the Altos layer is such that the total amount is γ-M, 0. It is preferably 5 to 30 weight percent, more preferably 10 to 20 weight percent. If the amount of metal added to the rAntOs layer is less than 5% by weight, no improvement in heat resistance will be observed, while if it exceeds 30% by weight, the metal oxide will be added to the rAntOs layer. A large amount precipitates at the grain boundaries of r-A,
The mechanical strength of the 03 layer decreases.

r-Q, 0. The amount of ceramic whiskers added to the layer is such that the total amount is 1 to 3 with respect to r-AJ203.
It is preferably 0 weight*chi, more preferably 1 to 1
This is 0 Jubuni-chi. When the amount of ceramic whiskers added to the AJ203 layer is less than %, no improvement in strength at high temperatures is observed;
If it exceeds 0% by weight, the strength at high temperatures will be saturated and the catalyst activity will decrease.

Examples of ceramic whiskers used in the present invention include silicon carbide (SiC), [silicon whisker]
Ceramic whiskers such as )b alumina ()J20B) can be used, and xm or two or more selected from the group consisting of these whiskers are used.

The amount of pt and/or Pd supported on the noble metal catalyst used in the present invention is not limited to 0.
．． 01 to 10% by weight is preferred.

The high-temperature combustion catalyst of the present invention described above can be manufactured, for example, as follows.

First, an alumina coating composition consisting of γ-A403 was coated with Ce% I, a, Srs Sns Zr and Mg
A predetermined amount of at least one metal whisker and a ceramic whisker selected from the group consisting of the following are added. Note that the metal is preferably its gold 1itS salt, for example.

Next, the above-mentioned composition is pulverized to form a solid substance using, for example, a D5 ball mill. The coating liquid obtained in this way is colored by pouring it onto a thermal carrier, and after sufficiently drying at room temperature, it is heated for example at 650C for 3
Time sum gt firing.

This fired carrier is immersed in a solution in which a predetermined amount of catalyst metal is dissolved, and then sufficiently dried again at room temperature, and finally, for example,
It is possible to obtain the fusion of the present invention by calcination at 550C for 3 hours in a hydrogen atmosphere.

It is preferable to use the catalyst metal in the form of a gold salt such as chloroplatinic acid or palladium chloride dissolved in water or the like.

Although the reason why the high temperature combustion catalyst of the present invention has excellent heat resistance is not clear, it can be considered as follows.

That is, r Aj! By adding it to the tOs layer, γ-A, 0. It is thought that the grain boundaries of the phase have become finer. It is believed that the added metal precipitates as oxides on the grain boundaries, and these strongly capture the noble metal catalyst particles on the grain boundaries, thereby inhibiting heat transfer to the noble metal catalyst particles. Furthermore, the miniaturized r IJ
It is believed that the tOs layer and the added ceramic whiskers prevent the generation and propagation of cracks, thereby improving heat resistance.

[Embodiments of the invention]

Example 1 An alumina coating composition having the composition shown below was prepared.

The above composition was mixed using a ball mill at room temperature for 2 hours to pulverize the solid matter.

Next, a liquid obtained by dispersing the alumina coating composition in water was poured several times onto the cordierite unicum-shaped carrier, and then dried at room temperature for about 1 day. This honeycomb-shaped carrier was fired at 650C for 3 hours.

On the other hand, an aqueous solution was prepared in which chloroplatinic acid and palladium chloride were dissolved in water so that 0.9 g of platinum and palladium were each present as metals. The honeycomb-shaped carrier was immersed in this aqueous solution for 1 hour to impregnate the carrier with the noble metal catalyst.

Next, this honeycomb-shaped carrier was dried and then heated at 550C for 3 hours in a hydrogen atmosphere to obtain a high-temperature combustion catalyst (A) according to the present invention.

Example 2 Using the same method as in Example 1, lanthanum nitrate, strontium nitrate, tin nitrate, zirconium nitrate, and magnesium nitrate were used as metal salts added to the alumina coating composition, and carbonized ceramic whiskers were added as ceramic whiskers. Using silicon whiskers, silicon oxide whiskers, and alumina whiskers, 18 types of high-temperature combustion catalysts (B) to (S) as shown in the table were prepared by changing their combinations and amounts added.

Comparative Example At the same time, as a comparative example, an alumina coating composition in which either metal or ceramic Quisker was not added, or both were added, or a large amount of metal was added was prepared using the same method as in Example 1. Four different types were prepared.

Its composition is shown in the table.

Example 3 The combustion characteristics of the 19 types of high-temperature combustion catalysts obtained in Examples 1 and 2 and the 4 types of combustion catalysts obtained in Comparative Examples were evaluated using a distribution test equipment.

The test conditions were: gas flow rate: 5 no/miR, combustion gas concentration: methane (CH,) 1%, catalyst density: 10 CC, and space velocity: 3 X iQ'hr-''.

Next, the combustion catalyst was placed in a heat treatment furnace and heat treated at 1100C and 1400C for 50 hours, respectively.
The combustion characteristics of each were evaluated in the same manner as above.

The ratio of combustion characteristics before and after heat treatment of each combustion catalyst obtained through the above test was calculated as the catalyst activity retention rate. The results are also listed in the table along with the composition.

Furthermore, the surface after the heat treatment was observed and evaluated in the following four stages, and the results are also listed in the table.

◎・・・No cracks, ○...Crack foot.

△・・・・・・Partial peeling, ×...A lot of peeling hlt feet.

As is clear from the table, the high-temperature combustion catalyst of the present invention is significantly superior to the comparative example in terms of catalyst activity retention, which is an indicator of the heat resistance of the catalyst, and the surface shape after heat treatment. was confirmed.

Although a honeycomb-shaped carrier was used in the above example, similar results were obtained when a pellet-shaped carrier was used.

〔Effect of the invention〕

The high temperature combustion catalyst of the present invention has significantly improved heat resistance compared to conventional noble metal combustion catalysts. Therefore, it is possible to save and use energy efficiently, and since it is possible to burn without generating NOx, etc., it does not cause environmental pollution.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a noble metal combustion catalyst, and FIG. 2 is a plan view thereof. 1... Support, 2... r-, υ, 03.3... Noble metal. Figure 1 2nd Place: Inside the Research Institute of Kyoshi Shibaura Electric Co., Ltd., 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki City0 Inventor: Yamanakaya Inside the Research Institute of Kyoshi Shibaura Electric Co., Ltd., 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki City 0 Invention Author: Junji Koizuka 153-1, Komukai Toshiba-cho, Saiwai-ku, Kawasaki City, Shibaura Electric Co., Ltd. General Research Center

Claims (1)

[Claims] Heat-resistant carrier; cerium (Ce) provided on the carrier;
Lanthanum (La), strontium (Sr), tin (
Sn), zirconium CZr) and magnesium (M
γ-alumina (γ-kl) containing at least one metal selected from the group consisting of g) and ceramic whiskers;
1. A high-temperature combustion catalyst comprising: a coating layer of R-alumina; and platinum (Pt) and/or palladium (Pd) supported on the r-alumina coating layer.