JPS60202745A - Catalyst for high-temperature combustion - Google Patents

Abstract

PURPOSE:To obtain the titled catalyst for the high-temp. combustion of hydrocarbonic fuel having high activity and excellent resistance to heat and thermal shock by providing a single coating layer of a heat-resistant metallic oxide to a monolithic carrier, and depositing an active component such as platinum at the inside of the surface layer of said coatng layer. CONSTITUTION:A single coatin layer of an active heat-resistant metallic oxide such as alumina is provided to a monolithic carrier of cordierite, etc., and >=1 kind of active component selected from a group consisting of Pt and Pd is deposited at the inside of said coatig layer >=2mu off the surface layer to an amt. of 1-50g per 1l completed catalyst. The catalyst thus obtained has high activity and excellent resistance to heat and thermal shock without any increase in pressure drop, and the catalyst for the high-temp. combustion of hydrocarbonic fuel can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION 10. Background Technical Field of the Invention The present invention relates to a catalyst for completely catalytically burning a hydrocarbon fuel. Specifically, the present invention catalytically and completely burns fuel on a catalyst to remove nitrogen oxides (hereinafter referred to as NOX).
), -carbon oxide (hereinafter referred to as

The present invention relates to a catalyst that is particularly highly active and has excellent heat resistance in order to obtain combustion gas that does not substantially contain harmful components such as carbon dioxide and other harmful components, and to use its heat as a variety of energy sources.

Prior Art A catalytic combustion system is known in which a dilute mixture of hydrocarbon fuel mixed with air at a low concentration that does not fall within the combustible range is introduced into a catalyst layer and catalytically combusted to obtain highly humid combustion gas.

Furthermore, using such a catalytic combustion system, e.g.
When obtaining combustion gas at a temperature of 0°C to 1,500°C, even if air is used as the oxygen source, little or no NOx (J) is generated, and CO1J3 and U I-I C
It is also well known that λ11 does not contain substantially any of the following.

Various systems for obtaining heat or power using this clean high-temperature waste have been proposed, and some systems for treating general industrial exhaust gas and for recovering heat or power have been put into practical use. Furthermore, in recent years, systems have been proposed that are used as primary power sources such as gas turbines for power generation.

The catalysts used in these systems need to have excellent low-temperature ignition properties, high activity, and excellent heat resistance, and especially when used as a secondary power source, their thermal efficiency must be 1.000℃~1.3 for improvement
It is necessary to withstand high temperatures of 00° C. or higher, and it is also required to have high activity in order to achieve complete combustion with a small volume of catalyst because it is necessary to reduce pressure loss at high linear velocity.

Various metal oxides such as cobalt oxide, chromium oxide, and nira wool oxide have been proposed as combustion catalysts with excellent heat resistance, but these catalysts have high ignition temperatures and are not flame retardant, especially at high linear speeds. When methane or natural gas containing methane as a main component is used as a fuel, it cannot be ignited unless it is at a high temperature of 800°C or higher. Palladium in the first stage.

It is possible to burn at a low ignition temperature using an ignition catalyst such as platinum, but in this case, a considerably long catalyst layer length is required to achieve complete combustion, and as a result,
Pressure loss increases, and this is not preferable, especially for use in gas turbines for generating second-order power sources.

On the other hand, catalysts containing noble metals such as platinum and palladium as active ingredients are highly active and can achieve complete combustion at high linear velocity and with a short catalyst layer length. When methane or natural gas containing methane as a main component is used as a fuel at a high linear velocity exceeding 10111/sec, palladium, platinum, etc. can be loaded in a high amount of 1 to 50 (l) per 1°C of the finished catalyst. It is necessary that the catalyst be a catalyst with a high degree of a content.When a high temperature of 1°000°C or higher is reached, the noble metal component aggregates on the catalyst surface, forming lumps of several tens of microns, and the activity decreases. In addition, these agglomerates are physically blown away by the high linear velocity combustion gas, reducing the active ingredients and eventually deactivating them.

A phenomenon similar to this deactivation phenomenon is described in Japanese Patent Application Laid-Open No. 58-3゜641.
As a countermeasure to this problem, it has been proposed to cover the surface with a heat-resistant oxide such as alumina or zirconia.
It was confirmed that this method was effective against the loss of precious metals due to migration, condensation, and shedding as described above.

However, it is extremely difficult to uniformly coat a heat-resistant oxide such as alumina with a thickness of λ9 on the catalyst surface, which has many voids, and a considerable amount of heat-resistant oxide is required to cover the entire surface. As a result, in the case of monolithic catalysts, not only the porosity decreases and the pressure loss increases, but also, especially at high linear speeds, the fuel gas components diffuse into the inner layer where the catalytically active components are present ( As a result, it was found that the activity was at a low level.

(1) Object of the Invention Therefore, an object of the present invention is to provide a catalyst for high-humidity combustion of hydrocarbon fuel. Another object of the invention is to
It is an object of the present invention to provide a catalyst for combustion of hydrocarbon fuels which is highly active, has excellent heat resistance and thermal shock resistance, and does not cause an increase in pressure loss.

In various cases, a single coating layer of a heat-resistant metal oxide is provided on a monolithic support, and 2 μl is added from the surface layer of the coating layer.
This is achieved by a hydrocarbon fuel combustion catalyst characterized in that a noble metal catalytic active component is supported on the inner surface of the catalyst.

(8) Specific structure of the invention In the catalyst according to the invention, noble metals used as catalytically active components include, for example, platinum and palladium.

The catalyst according to the present invention also has excellent low-temperature properties and can be used alone in the case of easily combustible bamboo combustible materials such as light oil and propane, but in cases where low-temperature ignitability is required or when methane When using a flame-retardant fuel such as natural gas, it is preferable to use it in combination with an ignition catalyst containing palladium as the active main component.

Further, when the temperature of the combustion gas becomes extremely humid, a metal oxide catalyst as described above may be used in combination at the latter stage.

The shape of the catalyst of the present invention is preferably a monolith type for the purpose of reducing pressure loss. Further, the cell size is preferably large as long as the combustion efficiency does not decrease, and the cell size may be the same or a combination of cells with different cell sizes may be employed.

The monolithic carrier used in the present invention can be any carrier commonly used in the field, and in particular, dil-gelite, murai], α-alumina, zirconia 7, titania, titanium phosphate. .

Magnesium aluminum titanium 1~, mullite.

Aluminum ditanate, petalite, subodumene,
Aluminosilicate, magnesium silicate.

Heat-resistant ceramic materials such as zirconia-spinel, zircon-mullite, silicon carbide, and silicon nitride, and metal materials such as Kanthal and Feclaroy are used.

The monolithic support is used by coating an active heat-resistant metal oxide such as alumina, silica-alumina, magnesium, ditania, zirconia, silica-magnesium, or the like. Particularly preferred are alumina or zirconia, and more preferably alkaline earth metal oxides.

It is more preferable to add a rare earth metal oxide to stabilize it before use.

These metal oxide coatings have a concentration of 20 to 50% per λ of finished catalyst.
0(], preferably 50 to 300 g, and 10 to 250 μm, preferably 25 to 150 μm, on the surface of the monolithic carrier.
A coating layer with a thickness of μm is provided.

Then, an active ingredient such as platinum or palladium is supported inside the coating layer using an aqueous solution of various salts. This depth.

In other words, the I9 quality of a layer that does not contain an active ingredient is determined by the type of coating layer, its roughness, the type of active ingredient, the amount supported, or the temperature at which it is used, and the rate of movement of the active ingredient to the surface and the diffusion of fuel gas. Optimally determined by speed, but typically 2
~100μro1. Preferably, 5 to 50 μm is selected.

There are various methods for supporting catalytically active components inside the catalyst.
For example, a method disclosed in U.S. Pat. No. 3,259,589 in which a dibasic acid such as citric acid is mixed with an aqueous solution of a salt of an active ingredient and their competitive adsorption is utilized is an automatic exhaust gas treatment method. Some applications have been made in industrial catalysts.

However, this is mainly based on pellets with a low loading of precious metals (lead, phosphorus, etc.).

It is intended to protect catalytic active components from poisonous substances such as sulfur, and is intended to prevent the agglomeration of precious metal components and the falling off of agglomerates as in the present invention. It can be said that the application to type catalysts is completely new.

Jf to the inner layer of the catalytically active component used in the present invention
] Competitive adsorption with the above-mentioned dibasic acid can also be used as a method of adsorption; II by drying below the melting temperature, sublimation temperature or decomposition temperature and then immersing in an aqueous solution of the salt of the active ingredient.
I-covering method, the above two methods; J5 method using an inorganic polybasic acid such as phosphoric acid, sulfuric acid, or boric acid instead of a dibasic acid, or applying an emulsion of various waxes on the surface layer in advance and drying. There are methods such as immersing the active ingredient in an aqueous solution of the salt of the active ingredient and forcibly infiltrating the inner layer under reduced pressure.This method also requires selecting the appropriate method depending on the type of salt of the active ingredient, the amount supported, and the type of coating layer. I can do it.

Then, in air or in a reducing atmosphere gas, 300 to 1
The catalyst is activated by calcination at 200°C, preferably between 300 and 900°C to obtain the finished catalyst.

(2) Concrete Effects of the Invention The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 200 cells/' square inch opening with a diameter of 25
．． A cordierite honeycomb carrier with a diameter of 4 mm and a length of 50 mm was coated with a slurry of alumina powder containing 5% by weight of ceria, and fired in air at 700°C to form a carrier of 1°C.
19 coats each carrying 100 g and having an average thickness of about 50 μm.

Next, the carrier was immersed in 30 cc of an aqueous solution in which 0.259 trimellitic anhydride was heated and dissolved, heated to about 80°C for 10 minutes, and then dried at 100°C, so that 10 g of trimellitic acid was supported on the surface layer per 1°C of the carrier. Ta. Then, it was immersed in an aqueous solution containing chloroplatinic acid, dried, and left in the air for 7 days.
The catalyst was calcined at 00°C and loaded with platinum at an amount of 10o/°C.

As a result of analysis of this catalyst by EPMA, it was found that almost no platinum existed within about 20 μm from the surface of the coating layer.

Example 2 In the same manner as in Example 1, 14 coating layers having an average thickness of about 50 μm were formed. Next, this was mixed with chloroplatinic acid at a concentration of 0.0% per 1g of platinum.
The catalyst was immersed in an aqueous solution containing 0.5 g of phosphoric acid, dried and calcined in air at 700° C. to obtain a catalyst containing 10 g of platinum per 1a of support. As a result of EPMA analysis of this catalyst, it was found that almost no platinum existed within about 10 μm from the surface of the coating layer.

Comparative Example 1 In the same manner as in Example 1, 1 q of coating layers having an average thickness of about 50 μm were formed. Next, this was immersed in an aqueous solution containing chloroplatinic acid, dried, and calcined in air at 700°C to obtain a catalyst on which 10(+) of platinum was supported per 1°C of the carrier.

Comparative Example 2 The catalyst of Comparative Example 1 was further coated with the same slurry and calcined in air at 700°C to obtain a catalyst again coated with 30 ( ] per 11 carriers. This catalyst was partially coated with the same slurry. There were some places where the secondary coating layer did not exist.

Comparative Example 3 A catalyst was obtained in the same manner as in Comparative Example 2, in which 60 (]/C of the carrier was again coated and supported. Even in this catalyst, it was observed that the secondary coating layer was not present in a very small portion.

Example 3 The catalysts of Example 1 "-2J3 and Comparative Examples 1 to 3 were exposed in an electric furnace at 1,100°C for 200 hours, and then the state of agglomeration of platinum particles on the catalyst surface layer was observed using an electron microscope. It is exposed to an air flow with an inlet linear velocity of 4 Qm/sec at room temperature for 24 hours, and then charged into an internal cylinder type combustor, and a methane-air mixer containing 3% by volume of methane is heated at 13% per hour.
Introducing 8NI113 and gradually raising the preheating temperature to -F.
The combustion rate of methane was measured. In this case, the linear velocity at the inlet of the catalyst layer was 20 m/sec at 500°C.Furthermore, the amount of platinum supported thereon was analyzed by fluorescent X-ray analysis.The results are shown in Table 1. In the catalyst of Comparative Example 1, the agglomerated platinum lumps were blown away, and as a result, the activity decreased and the secondary coating was insufficient, and in the catalyst of Comparative Example 3, the secondary coating was insufficient. The secondary coating layer is too thin to allow sufficient gas diffusion into the interior, resulting in low activity.

On the other hand, the catalysts of Examples 1 and 2 do not have the above problems and can be said to be highly active catalysts with excellent heat resistance.

(Margin below)

Claims (1)

[Scope of Claims] (1) A heat-resistant product characterized in that a monolithic carrier is provided with a single coating layer of a heat-resistant metal oxide (), and an active ingredient is supported on the inside of the coating layer by 2 μm or more from the surface layer. (2) The catalyst according to claim 1, wherein the hydrocarbon fuel is methane or natural gas containing methane as a main component. ( 3) The catalyst according to claim 1 or 2, characterized in that the active component is supported in an amount of 1 to 50 g per 1° C. of the finished catalyst. (L4) The active component is selected from the group consisting of platinum and palladium. The catalyst according to any one of claims 1 to 3, which is at least one type of catalyst.