JPS63232849A - Production of high-temperature combustion catalyst - Google Patents

Abstract

PURPOSE:To enhance catalytic activity at high temp. by adding oxide powder of rare earth elements alumina sol to Al2O3 powder contg. rare earth elements, crushing and mixing the mixture and sticking it on the surface of a carrier and thereafter calcining it. CONSTITUTION:After blending oxide powder of at least one kind of element selected from among lanthanum, praseodymium and neodymium and alumina sol with alumina powder contg. at least one kind of element selected from among lanthanum, praseodymium and neodymium, the mixture is crushed and mixed for 1-100hr. After sticking this crushed mixture on the surface of the base material of a carrier to form an alumina layer, this is calcined in the nonoxidative atmosphere and a high-temp. combustion catalyst is obtained by depositing noble metal on this carrier. As the kind of noble metal, in the case of combustion of methane, Pd is preferably used and in the case of combustion of propane, Pt is used.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for producing a high-temperature combustion catalyst.
The present invention relates to a method for producing a high-temperature combustion catalyst that has high activity in the temperature range of about 800 to 1500°C and has a long life.

(Prior Art) 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 1 at as high a temperature as possible.

However, the conventional method is to ignite and burn a mixture of fuel and air using a spark plug or the like.
Inside the combustor, there is a high temperature area that partially exceeds 2000°C. and.

It is known that nitrogen oxides (NOx) are generated in large quantities in this high temperature section, causing problems such as environmental pollution.

In order to solve these problems, catalysts are used to reduce fuel consumption.
A catalytic combustion method has been proposed in which a mixture of 1 and air is combusted. 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 increased to about ℃.

Currently, the catalyst used in catalytic combustion systems is platinum (
pt)-based noble metal catalysts are known. 11 like this
For example, the L-metallic combustion catalyst is made of γ-alumina (γ-A2) as an active carrier on a carrier having a certain mechanical strength.
03) and further, by a dipping method, a noble metal was supported.

However, the noble metal combustion catalyst obtained by applying the above manufacturing method is said to have a heat resistance temperature of 600'0, and its catalytic activity rapidly decreases in the temperature range higher than that, making it unsuitable for use. The problem is that it cannot be done.

The reason why the catalyst activity rapidly decreases at a temperature of 600° C. or higher can be considered as follows. First, the first
Second, the noble metal particles on the surface of the carrier aggregate and become coarse due to heat transfer, resulting in a decrease in the catalyst surface area and a deterioration in combustion performance. Second, since γ-AU, 03 undergoes a phase transition to α-A pattern 203 at temperatures around 1000° C. or higher, within the A1203 layer or A! L20. This is thought to be due to the fact that cracks occur between the substrate and the Al1203 layer and the Al1203 layer peels off together with the catalyst metal.

Therefore, in order to improve the heat resistance of the 111 metal combustion catalyst, the γ-AJ1203 layer was improved, and the γ-A pattern and 03
AfL20.PT particles on the layer. Attempts have been made to prevent agglomeration due to heat transfer by strongly adsorbing the γ-A layer, and also to prevent the occurrence of cracks by preventing α-ization of the γ-A texture layer.

As a result, a product with metal added to the γ-AfL203 layer has been developed, and it has been confirmed that this product can withstand use up to around 800"C as an automobile catalyst, for example. The heat resistance at high temperatures is still not sufficient, and there is still room for further improvement.

(Problems to be Solved by the Invention) As described above, in the conventional method for producing a combustion catalyst, the obtained combustion catalyst does not have sufficient heat resistance at high temperatures, for example, 800° C. or higher.

There is a problem that high activity cannot be maintained.

The present invention solves this conventional problem, and the
The object of the present invention is to provide a method for producing a high-temperature combustion catalyst that has high activity even in a temperature range of 0° C. and has a long life.

[Structure of the Invention] (Means and effects for solving the problem) As a result of intensive research to achieve the above object, the present inventors have found that when a rare earth element is blended into alumina, it should be blended. It has been found that by adopting a two-step blending method in which a part of the rare earth element is pre-contained in the A-203 powder and the remainder is mixed as an oxide powder, an excellent effect on the heat resistance of the resulting catalyst can be obtained. This discovery led to the completion of the present invention.

That is, in the method for producing a high-temperature combustion catalyst of the present invention, at least one element selected from lanthanum, praseodymium, and neodymium is added to alumina powder containing at least one element selected from lanthanum, praseodymium, and neodymium. A step of blending the oxide powder and alumina sol and pulverizing and mixing for 1 to 100 hours; A step of adhering this pulverized mixture to the surface of a carrier base material to form an alumina layer; It is characterized by comprising a step of firing and a step of supporting the noble metal on the carrier.

The manufacturing process of a combustion catalyst to which the method of the present invention is applied will be sequentially explained below.

The first step is to prepare a so-called alumina coating liquid by blending, pulverizing and mixing specified additives with alumina (AfL203) powder.

In this process, first, rare earth elements lanthanum (La) and praseodymium (Pr) are used as alumina powder.
and neodymium (Nd). At this time, the method of incorporating the rare earth element into the Humanities 203 powder is not particularly limited, and a conventional method such as an impregnation method can be applied. When applying the impregnation method, in order to sufficiently advance the reaction between the rare earth element and A9.2os, it is preferable to bake at 900 ° C. or higher after impregnation.
At this time, the content of rare earth elements in the A-mon 203 powder is converted into oxides of each element! It is preferable that the A-203 powder to be used is fine in order to increase the specific surface area of the catalyst finally obtained, but it is preferable to set the powder to 301 [-%. Since the heat resistance of the catalyst decreases when used, it is usually preferable to use particles with an average particle size of about 0.1μIR to 1μ.
Alternatively, it is preferable to use a high temperature type A or 203 having higher heat resistance, and when hydroxide type Al2O3 is used, it is preferable to use it after heat treatment at 400 to 800°C.

Next, La was added to the above rare earth element-containing/1,03 powder.
, at least one rare earth element resistant powder selected from Pr and Nd, and alumina sol,
At this time, the rare earth element is AfL20. It may be the same type as that contained in the powder or it may be different type, and for example, L
When using a oxide, Mitshu metal etc. can also be used. Further, the alumina sol to be used is not particularly limited, but it is advantageous for operation to use a neutral or alkaline one. Also,
The blending ratio of each additive to the A203 powder is not particularly limited, but 5 to 20% of the rare earth oxide powder is
It is preferable that the amount of modified alumina sol is 80 to 95% by weight.

The mixer for crushing and mixing the An203 powder and the above-mentioned additives is not particularly limited, and for example,
A ball mill, a V-shaped mixer, a screw mixer, etc. can be applied. It is necessary to set the grinding/mixing time at this time to 1 to 100 hours. If the crushing/mixing time exceeds the above range, the durability of the ultimately obtained catalyst will be reduced.

The second step is a step of depositing the pulverized mixture obtained in the first step, that is, the AjL203 coating agent onto the carrier base material to form an alumina layer. The carrier base material is not particularly limited as long as it has stable properties even in a high temperature oxidizing atmosphere of about 1500"C, and examples thereof include cordierite, mullite, α-alumina, zirconia spinel, and titania. Ceramic carriers such as
There is no particular restriction on the shape as long as the shape is normally used as a catalyst, and examples thereof include pellets, honeycomb shapes, and the like. Further, examples of methods for applying the alumina coating liquid to these carriers include a coating method, a dipping method, and a spraying method. Note that the amount of coating is preferably determined as appropriate depending on the shape, size, amount of beads, etc. of the carrier.

The third step is a step of firing the carrier base material on which the alumina layer has been formed in the second step. This firing step must be carried out in a non-disfiguring atmosphere. Here, the non-saponifiable atmosphere refers to an atmosphere that does not contain oxygen, and specifically includes an N2 gas cloud atmosphere, a CO2 gas atmosphere, an inert gas atmosphere such as Ar or He, or a mixture of two or more of these. Examples include gas atmosphere. Note that the firing temperature is not particularly limited.

In order to ensure sufficient mechanical strength of the catalyst, 600~
It is preferable to set the temperature to 1200°C, particularly 700 to 1100°C.

Step f7', 4 is a step of further supporting a noble metal on the alumina layer, and conventional method 1, such as an impregnation method, can be applied to this step. Furthermore, the noble metals used include conventionally used palladium (Pd), platinum (pt), rhodium (Rh), etc. In this case, the type of noble metal depends on the type of target fuel. For example, it is preferable to decide based on
When the fuel is methane, it is preferable to use Pd, and when the fuel is propane, it is preferable to use pt.

(Example) Example 1 (1) Production of combustion catalyst γ-A Bun 203 powder with an average particle size of about 1a+m was impregnated with an aqueous lanthanum nitrate solution, dried, and then in air.
After firing at 1000°C for 1 hour, the La oxide was heated to 5! i
A La-containing AJLz03 powder containing f% was obtained.

Next, 25 g of La oxide and alumina sol (solid content 80 g) were added to 100 g of this La-containing AJ1203 powder.
(% by weight) was blended and ground and mixed in a ball mill for 10 hours to prepare an alumina coating liquid.

2 g of this coating liquid was applied to a one-piece base material made of Nisilite (25I1mφX25a+m, 200 cells) and dried at 120°C for 2 hours, and then
It was baked at 1100°C for 4 hours.

After that, PdCJLz was added to this carrier.
Convert to 1. 600 after being supported so that it becomes Og.
The target catalyst was obtained by calcining at ℃ for 2 hours.

(2) Catalyst evaluation test (gas turbine combustion test) Commercially available PdM medium (for example, the amount of supported Pd is 10 g/l or more, and the amount of rare earth elements such as La in the A2203 layer is 15% by weight)
A two-stage combustion catalyst unit was constructed, with the combustion catalyst of the present invention manufactured as described above being the latter stage and the combustion catalyst of the present invention produced as described above.

This combustion catalyst unit was installed in a catalytic combustion type gas turbine combustor, and the combustion characteristics of the combustion catalyst were evaluated. That is, the combustion conditions at this time are Gas Ryukyu 30 m/s
ec, fuel concentration methane 3%, catalyst volume 12cc,
Measure the catalyst temperature and combustion efficiency after 100 hours of combustion time,
The results are shown in the table.

Examples 2-12. Comparative Examples 1 to 6 Types of rare earth elements contained in A-mon 203 powder, Af
A combustion catalyst was produced in the same manner as in Example 1 above, except that the type of rare earth refractory compound blended into the L, 03 powder, the crushing/mixing time, and the atmosphere during firing were varied as shown in the table. A similar Jf value test was conducted and the results are shown in the table.

[Effects of the Invention] As is clear from the above description, the combustion catalyst manufactured by applying the method of the present invention can be used for example in a gas turbine combustor for up to 100 hours, which is an index of its high-temperature durability. It was confirmed that the subsequent catalyst temperature was extremely high and the combustion efficiency was also high. Therefore, it is possible to save combustion energy and efficiently utilize combustion energy in a gas turbine combustor, etc., and furthermore, the generation of NOx is prevented, and its industrial value is extremely large.

Claims (1)

[Claims] Alumina powder containing at least one element selected from lanthanum, praseodymium, and neodymium is blended with an oxide powder of at least one element selected from lanthanum, praseodymium, and neodymium, and alumina sol. A step of time-pulverizing and mixing; A step of adhering this pulverized mixture to the surface of a carrier base material to form an alumina layer; A step of firing this in a non-oxidizing atmosphere; A step of making the carrier support a noble metal. A method for producing a high-temperature combustion catalyst, characterized by comprising: