JPH04322744A - Catalyst for combustion of hydrocarbon - Google Patents

Abstract

PURPOSE:To offer a catalyst for combustion of hydrocarbon high in combustion activity and excellent in heat resistance. CONSTITUTION:The catalyst for combustion of hydrocarbon obtained by making a metal of platinum group carried on a catalyst carrier containing alumina, zirconia or these double oxide sintered at >=1200 deg.C is used.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a catalyst for the combustion of hydrocarbons, and in particular a catalyst with high combustion activity that can be used in high-temperature combustors such as boilers, jet engines for aircraft, gas turbines for automobiles, and gas turbines for power generation. This invention relates to a hydrocarbon combustion catalyst with high heat resistance.

0002

[Prior Art] The most active catalyst for completely oxidizing hydrocarbons into carbon dioxide gas and water vapor in the presence of oxygen is a catalyst in which platinum metals such as platinum and palladium are supported on inorganic heat-resistant materials such as alumina and silica. It is widely used because of its high Furthermore, various catalysts have been widely studied and proposed to improve combustion activity and heat resistance. For example, as disclosed in JP-A-60-222145, a method has been proposed in which a rare earth element such as La is added to alumina to improve heat resistance. However, when a catalyst using an inorganic heat-resistant material such as alumina or silica as a carrier is used for high-temperature combustion, there is a problem in that the combustion activity is significantly reduced.

0003

[Problems to be Solved by the Invention] It is generally believed that combustion activity depends on the dispersibility of the catalytically active metal, and that the dispersibility of the catalytically active metal also depends on the surface area of the carrier. From this point of view, in the development of catalysts for high-temperature combustion, it is important to develop catalyst carriers that have a large surface area even at high temperatures and have excellent heat resistance.

The present invention solves the above-mentioned problems of the prior art and provides a hydrocarbon combustion catalyst that has high activity even at high temperatures and has excellent heat resistance for use in catalytic combustion type high-temperature combustors. With the goal.

[0005]

[Means for Solving the Problems] As a result of extensive research into catalysts for hydrocarbon combustion, the present inventors found that combustion activity can be increased by firing at a specific temperature before supporting a catalytically active metal on a specific catalyst carrier. It was discovered that a hydrocarbon combustion catalyst with high heat resistance and excellent heat resistance can be obtained, and the present invention was achieved based on this knowledge.

That is, the present invention relates to a catalyst for combustion of hydrocarbons obtained by supporting a platinum group metal on a catalyst carrier containing alumina, zirconia, or a composite oxide thereof that has been calcined at a temperature of 1200° C. or higher.

Alumina, zirconia, or a composite oxide thereof as used in the present invention is used as a catalyst carrier.

[0008] As alumina, α, β, γ, δ, η, θ
, κ, χ, etc. crystal forms can be used. Preferably, α, β, γ, η, etc. are used. Especially γ, η
is preferred.

In the present invention, the mixing ratio of alumina and zirconia is preferably 30 to 70 wt%:70 to 30 wt%.

In the present invention, the catalyst carrier may contain a small amount of a refractory inorganic oxide such as silica, magnesia or titania.

A platinum group metal is used as the active metal in the catalyst of the present invention. Ruthenium (
Ru), rhodium (Rh), palladium (Pd), osminium (Os), iridium (Ir), platinum (Pt)
can be mentioned. The active metals may be used alone or in combination of two or more. Palladium, rhodium, and platinum are preferred, with palladium being particularly preferred.

[0012] The catalyst preparation method of the present invention will be described. First, alumina, zirconia, or a composite oxide thereof is heated in air at a temperature of 1200°C or higher, preferably 1300°C to 1300°C.
A catalyst carrier is produced by firing at a temperature of 800°C. 12
When calcined at a temperature below 00°C, the surface area of the catalyst carrier decreases during use, and the combustion activity also decreases. Although the reason for this is not clear, it is thought that the carrier is sintered at high temperature during the combustion reaction, and the catalytically active metal is buried in the carrier layer.

[0013] The shape of the catalyst carrier may be any of extruded products, tablets, spherules, granules, powders, honeycomb structures, etc., and can be used in any desired size.

Next, a platinum group metal is supported on the catalyst carrier. A conventional method can be used for supporting the particles. For example, an impregnation method is preferably used in which the catalyst carrier is immersed in an aqueous solution containing a platinum group metal salt. Preferred salts include chlorides and nitrates.

The amount of platinum group metal supported as an oxide is 0.01 to 20 of the catalyst weight (total weight of catalyst carrier and active metal).
It is preferably 0.1 to 10 wt%, more preferably 0.1 to 10 wt%.

Next, in air, preferably at a temperature of 200 to
Dry at 500°C, preferably in air at a temperature of 90°C.
A catalyst can be obtained by firing at a temperature in the range of 0 to 1300°C.

Hydrocarbons as used in the present invention include methane, propane, butane, city gas, natural gas, kerosene, light oil, etc., which can be used as fuel for high-temperature combustors.

[0018]

EXAMPLES The present invention will be explained in detail below with reference to Examples, but the present invention is not limited to these Examples. Support materials used in the present invention include alumina,
Examples include zirconia and composite oxides thereof.

Example 1 Zirconia powder calcined at 1300°C in air was impregnated with an aqueous solution containing palladium chloride, dried and heated at 90°C in air.
A completed catalyst A was obtained by firing at 0° C. and supporting 0.5 g of palladium per 100 g of zirconia.

Example 2 Zirconia powder calcined at 1600°C in air was impregnated with an aqueous solution containing palladium chloride, dried and heated at 90°C in air.
A completed catalyst B was obtained by firing at 0° C. and supporting 0.5 g of palladium per 100 g of zirconia.

Example 3 Zirconia powder calcined at 1600°C in air was impregnated with an aqueous solution containing palladium chloride, dried and heated at 1300°C in air.
A completed catalyst C was obtained by firing at 00° C. and supporting 0.5 g of palladium per 100 g of zirconia.

Example 4 Alumina powder calcined at 1300°C in air was impregnated with an aqueous solution containing palladium chloride, dried and heated at 900°C in air.
C. to support 0.5 g of palladium per 100 g of alumina to obtain a finished catalyst D.

Example 5 Alumina powder calcined at 1600°C in air was impregnated with an aqueous solution containing palladium chloride, dried and heated at 900°C in air.
C. to support 0.5 g of palladium per 100 g of alumina to obtain a finished catalyst E.

Example 6 Mixing ratio 50% by weight, fired at 1300°C in air: 50
A mixture powder of zirconia and alumina consisting of % by weight is impregnated in an aqueous solution containing palladium chloride, dried and calcined in air at 900°C to support 0.5 g of palladium per 100 g of the zirconia-alumina mixture. Catalyst F was obtained.

Example-7 Mixing ratio 50% by weight, fired at 1600°C in air: 50
A mixture powder of zirconia and alumina consisting of % by weight is impregnated in an aqueous solution containing palladium chloride, dried and calcined in air at 900°C to support 0.5 g of palladium per 100 g of the zirconia-alumina mixture. Catalyst G was obtained.

Comparative Example-1 Zirconia powder calcined at 1100°C in air was impregnated with an aqueous solution containing palladium chloride, dried and heated at 90°C in air.
The catalyst was fired at 0° C. to support 0.5 g of palladium per 100 g of zirconia to obtain a finished catalyst H.

Comparative Example-2 Zirconia powder calcined at 1150°C in air was impregnated with an aqueous solution containing palladium chloride, dried and heated at 90°C in air.
The catalyst was calcined at 0° C. to support 0.5 g of palladium per 100 g of zirconia to obtain a completed catalyst I.

Comparative Example 3 Alumina powder calcined at 1100°C in air was impregnated with an aqueous solution containing palladium chloride, dried and heated at 900°C in air.
C. to support 0.5 g of palladium per 100 g of alumina to obtain a completed catalyst J.

Comparative Example-4 Baked in air at 1100°C Mixing ratio 50% by weight: 50
A mixture powder of zirconia and alumina consisting of % by weight is impregnated in an aqueous solution containing palladium chloride, dried and calcined in air at 900°C to support 0.5 g of palladium per 100 g of the zirconia-alumina mixture. Catalyst K was obtained.

The catalysts obtained in Example 1 to Example 7 and Comparative Example 1 to Comparative Example 4 were placed in a cylindrical combustor at 0.0.
The combustion activity was measured by charging 3 g of methane-air mixture gas containing 5% by volume of methane and introducing 9 liters per hour. The methane conversion rate was determined from the difference in the methane concentration in the inlet gas and the methane concentration in the outlet gas. Table 1 shows the reaction temperatures at which the methane conversion was 10% and 90%.

[0031]

[Table 1]

As is clear from the examples and comparative examples,
When the catalyst firing temperature is 900 to 1300°C, a catalyst obtained by supporting a platinum group metal on a catalyst carrier fired at a temperature of 1200°C or higher has a higher combustion rate than a catalyst fired at a temperature below 1200°C. It can be seen that it has high activity and excellent heat resistance.

[0033]

[Effect of the invention] A hydrocarbon combustion catalyst with high combustion activity and excellent heat resistance is obtained by supporting an active metal on a catalyst carrier made of alumina, zirconia, or a composite oxide thereof calcined at a temperature of 1200°C or higher. is obtained.

Claims (1)

[Claims] 1. A catalyst for combustion of hydrocarbons obtained by supporting a platinum group metal on a catalyst carrier containing alumina, zirconia, or a composite oxide thereof calcined at a temperature of 1200° C. or higher.