JPH0647283A - Catalyst carrier for combustion and its production - Google Patents

Abstract

PURPOSE:To obtain a catalyst carrier for combustion and a producing method for the catalyst carrier for combustion capable of utilizing low nitrogen oxide generating property and complete combustion property (low carbon monoxide, low odor) in a catalytic combustion at most and durable for a long period use. CONSTITUTION:This catalyst carrier for combustion contains (a) a heat-resistant inorganic material particle having 0.2-5mm particle diameter, (b) a binder and (c) an inorganic short fiber and has >1.5 gas permeability (1/min.cm<2> at 10mmH2O), >=60 three point bending strength (kgf/cm<2>) and >=10 cycles in thermal shock resistance.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a carrier for a combustion catalyst used for catalytic combustion and a method for producing the same.

[0002]

2. Description of the Related Art Catalytic combustion is a method for reducing the production of nitrogen oxides that cannot be avoided by flame combustion. This combustion system is a catalytic combustion device that is a combustion device that uses catalytic combustion, such as a consumer-use or commercial-use catalytic burner, a catalytic combustion heater, or a catalytic combustion heater, which uses liquid fuel (kerosene fraction) as fuel. Is used for. The catalyst carrier is indispensable for carrying out catalytic combustion. For the catalyst combustion, a monolith type, a honeycomb type, a particle filling type, or a particle sintering type catalyst carrier is used as a catalyst carrier. Among them, the particle-sintered catalyst carrier with the least fuel blow-through has the highest burning rate and heat radiation (JP-A-62-273).
048, 64-75039). However, if this particle-sintered catalyst is also used for a long period of time, incomplete combustion may occur. Therefore, as a result of investigating this point, the present inventors have found that the particle-sintered catalyst carrier is cracked due to thermal shock during repeated ignition and extinction.
Since the ventilation resistance at the cracked portion becomes small, the flow rate of fuel and air at this portion increases, and unburned components blow through and incomplete combustion occurs. It was found that the unburned components and incompletely burned components not only generate odors and toxic gases such as carbon monoxide, but also shorten the life of the combustion equipment.

[0003]

[Objective] An object of the present invention is to make the most of the low nitrogen oxide generation and complete combustion properties (low carbon monoxide, low odor) of catalytic combustion, and to support a combustion catalyst carrier for long-term use. The point is to provide a method for producing the combustion catalyst carrier.

[0004]

[Structure] The first aspect of the present invention comprises: (a) heat-resistant inorganic material particles having a particle size of 0.2 to 5 mm, (b) a binder (c) inorganic short fibers, and gas permeability (l / min · cm). ^{2 at} 10 mmH ₂ O)
1.5 or more Three-point bending strength (kgf / cm ² ) 60 or more Thermal shock resistance 10 cycles or more The present invention relates to a catalyst carrier for combustion. The gas permeability is indicated by the gas passage amount l / min · cm ² in a differential pressure water column of 10 mm, and the thermal shock resistance is defined as one cycle of holding at 850 ° C for 10 minutes and then cooling to room temperature. The number of cycles until cracking occurred was displayed. In the second aspect of the present invention, (a) heat-resistant inorganic material particles having a particle size of 0.2 to 5 mm, (b) a binder, (c) inorganic short fibers and (d) a low temperature curing agent are mixed and pressure-molded. After that, it is fired at 600 to 1300 ° C, and relates to a method for producing a catalyst carrier for combustion.

As the inorganic material particles (aggregates), heat-resistant inorganic materials such as particulate alumina, silica, a mixture of alumina and silica, and mullite are used. The particle size range is 0.2 to 5.0 mm in diameter, preferably 0.5 to 2.
It is 0 mm. If the particle size is smaller than 0.2 mm, the ventilation resistance becomes large and it cannot be put to practical use. Also, 5.0 mm
If it is larger, the three-point bending strength becomes small and it cannot be put to practical use.

As the binder, an inorganic material such as aluminum phosphate is usually used. The content of the binder (aluminum phosphate) is 3 to 12% by weight, preferably 5 to 9
% By weight. If the amount of the binder is less than 3% by weight, the three-point bending strength of the catalyst carrier becomes small and it cannot be practically used. If it is more than 12% by weight, the gas permeability is lowered. However, all weight ratios in the present invention are percentages (outer percentages) relative to the inorganic material particles.

As the inorganic short fibers to be added to the binder, short fibers such as alumina / silica, mullite, alumina, and quartz wool, and whiskers such as silicon carbide, silicon nitride, and potassium titanate can be used. Particularly preferred materials are Alumina and silica. Inorganic short fibers usually have a diameter of 0.1 to 10.
The length is 40 μm and the length is 5 μm to 4 mm. The amount of inorganic short fibers (alumina / silica short fibers) blended was 0.
It is 04 to 3.0% by weight, preferably 0.1 to 0.3% by weight. If the content of the inorganic short fibers is less than 0.04% by weight, the thermal shock resistance becomes small. On the other hand, if it exceeds 3.0% by weight, the strength becomes too small to be practical.

As a low temperature curing agent for the binder, MgO, Mg
Alkaline inorganic material powder such as (OH) ₂ , Al (OH) ₃ , CaO, Ca (OH) ₂ can be used. The low temperature curing agent (MgO fine powder) is blended in an amount of 0.03 to 1.2% by weight.
, And preferably 0.1 to 1.0% by weight. If the low temperature curing agent is less than 0.03% by weight, the strength of the molded product will be low, and if it is more than 1.2% by weight, the viscosity before firing will be high and the moldability will be poor.

The pressure at the time of pressure molding is required to maintain a sufficient strength of the green, usually 20 to 30 k.
It is g / cm ² , but is not limited to this.
The firing temperature is in the range of 600 to 1300 ° C, preferably 9
It is 00 to 1100 ° C. If the calcination temperature is lower than 600 ° C, the three-point bending strength of the catalyst carrier becomes small. If it is higher than 1300 ° C, the thermal shock resistance is lowered.

[0010]

The present invention will be described below with reference to examples, but the present invention is not limited thereto. The catalyst carrier used in the present invention is obtained by mixing the following materials, molding and firing. However, the mixing ratio is a percentage (outer ratio) value with respect to the aggregate. Raw material composition Aggregate: Alumina beads (average diameter about 0.8 mm) Binder: Aluminum phosphate 8% by weight Low temperature curing agent: MgO fine powder (average particle size about 0.3 μm) 0.5% by weight Inorganic short fiber: alumina Silica short fiber (average diameter of about 10 μm, average length of about 0.4 mm) 0.2% by weight Production method The raw materials shown above are aggregated and bound by a predetermined method using a rotation-revolution type mixer. , The low temperature curing agent, and the inorganic short fibers were mixed to be uniform. 100 x 100 mm of the mixture
It was uniformly filled in a mold having openings. It was pressure-molded with a hydraulic press at about 20 kgf / cm ² . The compact was fired using a muffle furnace. Calcination temperature: 1000 ° C. Catalyst carrier shape: 100 × 100 mm, plate-shaped body having a thickness of 9 mm, and the weight of the obtained catalyst carrier was 140 g. Using this catalyst carrier, gas permeability, 3-point bending strength, and thermal shock test were conducted. The test results are shown in Table 1 together with other manufacturing conditions. Further, by supporting a catalyst metal on this catalyst carrier,
A catalyst body can be obtained by performing calcination and reduction.

[0011]

[Table 1] However, in the evaluation, ◯ indicates that the conditions specified in the claims are satisfied, and x indicates that the conditions specified in the claims are not satisfied. The thermal shock resistance test is held at 850 ° C. for 10 minutes, then allowed to cool to room temperature, and this cycle is repeated 10 times. Method for producing catalyst A catalyst carrier carrying platinum, rhodium or palladium, which is the most typical metal as a catalyst for catalytic combustion and oxidation reaction, is used as a catalyst for catalytic combustion. Specifically, platinum was carried on the catalyst carrier by an immersion method using an aqueous solution of chloroplatinic acid of 0.25% by weight. The catalyst carrier is dipped in the chloroplatinic acid solution and then dried in the air while frequently being turned upside down. Then, in an electric furnace in the atmosphere, 80
The temperature is kept at 30 ° C., 100 ° C., and 120 ° C. for 30 minutes, respectively, and then the temperature is raised to 500 ° C. and firing is performed. After firing,
The catalyst is reduced under the following conditions to obtain a catalyst. Reducing gas: hydrogen 12 vol. % Nitrogen gas prepared to be calcination conditions: Temperature rising from room temperature to 400 ° C (200 ° C / H
r. After that, the mixture is held at 400 ° C. for 20 minutes, and then allowed to cool to room temperature (hydrogen is purged with nitrogen gas at about 100 ° C.) This platinum supporting operation can be repeated several times if necessary.

[0012]

[Effect] The present invention makes it possible to provide a catalytic combustion device that maximizes the low nitrogen oxide generation and complete combustion properties (low carbon monoxide, low odor) of catalytic combustion and that can withstand long-term use. . Further, the catalytic combustion system of the present invention can obtain a high heat radiation, thereby reducing the drying time in the drying process by the heat radiation. Further, since the catalytic combustion system of the present invention can perform heating by heat radiation, it can be used in a well-ventilated place.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Soichi Yamamoto 3-5 Kasumigaseki, Chiyoda-ku, Tokyo Showa Shell Sekiyu Co., Ltd.

Claims (2)

[Claims] 1. A heat-resistant inorganic material particle having a particle size of 0.2 to 5 mm, a binder, a short inorganic fiber, and a gas permeability (l / min.cm _{2 at} ¹⁰ mmH ₂ O).
1.5 or more 3-point bending strength (kgf / cm ² ) 60 or more Thermal shock resistance 10 or more cycles of combustion catalyst carrier. 2. (a) Heat-resistant inorganic material particles having a particle size of 0.2 to 5 mm (b) Binder (c) Inorganic short fiber and (d) Low temperature curing agent are mixed and pressure-molded, A method for producing a combustion catalyst carrier, which comprises firing at 600 to 1300 ° C.