JPH06320019A - Combustion catalyst and its production - Google Patents

Abstract

PURPOSE:To produce a novel thermal shock resistant combustion catalyst used in an oil burning system ensuring a low combustion noise and capable of perfect combustion without generating NOx. CONSTITUTION:This combustion catalyst consists of a metallic substrate of copper or copper alloy, a high temp. oxidation resistant metallic layer, an undercoat layer, a porous ceramic layer and an oxidation catalyst carried on the porous ceramic layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel combustion catalyst and a method for producing the same. In particular, the present invention relates to a combustion catalyst formed on the surface of a metal part of a combustion part of an oil and / or gas combustion device and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION The major sources of consumer energy in Japan are oil, gas and electricity. The ratio of petroleum (kerosene) to the energy consumption per household is about 30%, and it is expected that it will level off or gradually decrease in the future. This is because no petroleum combustion equipment has been developed that can sufficiently counter the low pollution, high convenience, safety and cleanliness of electric and gas thermal equipment. In general, petroleum combustion equipment such as petroleum hot water supply equipment and bath kettles generate noise of about 5 to 10 dB as compared with similar products of gas and electricity. In addition, the amounts of NOx, CO, and unburned hydrocarbons emitted are large. Therefore, petroleum hot water supply equipment, bath kettles, etc. are one of the sources of noise pollution or environmental pollution in the neighborhood, which hinders the spread of oil combustion equipment. In order to solve these problems and improve the comfort and safety of oil burning equipment, it is an effective method to use the surface of heat equipment parts such as fins of a silencer or a heat exchanger as a combustion catalyst. Catalytic combustion is a new combustion method that has various features such as achievement of complete combustion and prevention of generation of thermal NOx due to low temperature combustion. If such a combustion catalyst can be provided on the surface of the combustion equipment component, the advantage of catalytic combustion can be provided to the oil combustion equipment without changing the size of the oil combustion equipment. Further, if the surface of the heat transfer surface such as the fins of the heat exchanger can be used as the combustion catalyst, not only complete combustion and generation of thermal NOx can be significantly reduced, but also heat is generated on the solid surface, It is possible to avoid the influence of the heat transfer barrier between gas and solid and to improve the heat utilization efficiency. Moreover, unlike flame combustion, catalytic combustion does not produce combustion noise, so the effect of reducing combustion noise can be expected. Catalytic combustion is an excellent new combustion technology, but it can be used for consumer use at low cost, with high activity.
Since there is no catalyst that can withstand a high temperature of 00 ° C or higher, it is considered that the load per unit volume of the combustion site (Kcal / cm ³ ) is equal to or slightly inferior to that of conventional flame combustion. Therefore, it is effective to use the combustion catalyst on the surface of the equipment parts in order to use the catalytic combustion technology by keeping the size of the conventional oil combustion equipment unchanged or by miniaturizing it. As a result, it is possible to avoid the new installation of the catalyst installation section and to reduce the size of the flame combustion section. Currently, as a combustion catalyst, a ceramic-based catalyst carrier having a surface on which a catalytic metal is carried is used, which is not suitable for using the surface of a combustion equipment component as a combustion catalyst. Further, when used in a part that is subjected to high thermal shock and pressure shock during ignition and extinguishing, it is also a big problem that cracking or breakage occurs. Furthermore, a technique of using the surface of a metal material used for a combustion equipment component as a catalyst having high heat resistance has not been put into practical use at this stage. The present inventors have applied for a technology that solves this problem by using porous ceramics as Japanese Patent Application No. 3-242717. However, although SUS (stainless steel) could be used as the metal support, if copper or a copper alloy excellent in workability and thermal conductivity is used,
There was a problem that peeling, blistering, and cracking occurred.

[0003]

[Purpose] An object of the present invention is to provide a new type of combustion catalyst for use in an oil combustion system that has a low combustion noise, is capable of complete combustion without generating NOx, and has excellent thermal shock resistance, and a method for producing the same. In point.

[0004]

[First Structure] A first aspect of the present invention comprises a metal support made of copper or a copper alloy, a high temperature oxidation resistant metal layer, an undercoat layer, a porous ceramics layer and an oxidation catalyst supported on the porous ceramics layer. The present invention relates to a characteristic combustion catalyst. The metal forming the high temperature oxidation resistant metal layer is preferably a metal of Group 8 of the periodic table, particularly Ni or Co. The metal support made of copper or a copper alloy may be a metal component for combustion equipment, especially a heat exchange fin. A second aspect of the present invention is to form an undercoat layer by plating a metal surface made of copper or a copper alloy with a high temperature oxidation resistant metal, and then plasma spraying a metal spray material, and further forming a ceramic-based spray coating on the undercoat layer. The present invention relates to a method for producing a combustion catalyst, which comprises forming a porous ceramic layer by plasma spraying a material and then supporting an oxidation catalyst on the porous ceramic layer.

When the material of the metal support is stainless steel, it is possible to form a film having sufficiently good adhesion even if the ceramic-based thermal spray material is directly sprayed on the metal surface without spraying the undercoat material. In the case of copper and copper alloys, the coating will be easily peeled off when exposed to high temperatures with only the ceramic-based thermal spray material. However, it was found that a metal-based thermal spraying material (undercoat material) was first sprayed, and then a ceramics-based thermal spraying material was sprayed thereon to obtain a film with good adhesion. However, when a combustion catalyst is carried on the thus-prepared coating as described later, the coating alone has good thermal shock resistance, but at high temperatures, the coating peels off. Therefore, as a result of intensive research conducted by the present inventors, when a surface of copper or a copper alloy is plated with another metal having high high temperature oxidation resistance, and then an undercoat material and a ceramics-based thermal spray material are sprayed, a catalyst is supported. However, they discovered that a film having sufficiently high thermal shock resistance can be obtained, and completed the present invention.

The plating method for plating the surface of copper or copper alloy with a high temperature oxidation resistant metal is not particularly limited, and Ni, C may be used.
r, Co, Mo and the like. However, the following electroless nickel plating method is most preferable. In the electroless nickel plating method, when the hypophosphite anion of acidic sodium hypophosphite comes into contact with a Group 8 metal under specific conditions, the surface serves as a catalyst to form nickel ions in an aqueous nickel salt solution such as nickel sulfate. Is applied to deposit metallic nickel on the surface of the catalytic metal. Although copper is not a Group 8 metal, it is possible to plate the copper surface with nickel by inserting a small piece of a Group 8 metal (eg iron) into the plating solution. By this plating treatment, roughening treatment (blasting) as a pretreatment for plasma spraying is not always necessary.

A commercially available plasma spraying apparatus was used as the plasma spraying apparatus. As the metal-based thermal spray material (undercoat material), Al, Ti, Ta, Mo, Ni, Ni-
Although Al, Ni-Cr, NiCr-Al, CoCr-Al, etc. were used, Ni-Al and Ni-Cr are particularly preferable. As the ceramic-based thermal spraying material, Al ₂ O ₃ , TiO
₂ , Al ₂ O ₃ -TiO ₂ , Al ₂ O ₃ -MgO, Al ₂ O ₃ -S
iO ₂ , ZrO ₂ , ZrO ₂ -Y ₂ O ₃ , ZrO ₂ -MgO, Z
rO ₂ -CaO, ZrO ₂ -SiO ₂ , Al ₂ O ₃ -CoO, A
_{l 2 O 3 -ZrO, Y 2} O 3, metal oxides such as NiO is used.

A combustion catalyst was prepared by supporting a metal on the surface of the carrier obtained as described above. The metal was loaded by the method shown in FIG. Further, for some of them, a uniform gelation method using alumina can be applied. In the uniform gelation method using alumina, an aqueous solution of aluminum nitrate is mixed with an aqueous solution of a metal salt, and the solution is immersed in a carrier and then exposed to ammonia vapor to cause gelation, so that the metal salt is uniformly dispersed. Fix it. Then bake this,
It is a method of converting an aluminum compound into alumina.

[0009]

【Example】

Comparative Example 1 A copper plate material was used, and after roughening was performed by blasting as a pretreatment, six types of undercoat materials were plasma-sprayed, and one ceramic-based spray material was plasma-sprayed thereon. The thermal spraying conditions are as follows in each case. Undercoat material ceramic-based thermal spray material the primary gas (Ar) flow rate l / min. 39~73 39 secondary gas (H ₂₎ flow rate l / min. 6.6~11.9 9.0 voltage V 68 to 80 73 Current A 500 500 Spraying distance mm 100 100 Spraying amount g / min. 21-56 40-48 Physical properties of each coating sprayed with an undercoat material and a ceramics-based spray material are measured by specific surface area, surface roughness, and K-line test (scratch strength). ) And thermal shock resistance. The K-line test was conducted according to JIS H 8663, and the thermal shock resistance test was conducted according to JIS H 8666. In the heat shock resistance test, the film was heated at 850 ° C. for 10 minutes and then rapidly cooled in water, and this operation was repeated 5 times to observe peeling of the film and swelling or cracking. The test results are shown in Table 1. As shown in the table, Al is used as the undercoat material.
Although the specific surface area was comparatively larger than those of the others, the ones obtained by thermal spraying of the above and the ceramic-based gray alumina (coarse) were cracked in the thermal shock resistance test. Further, the one obtained by spraying Ni and gray alumina (coarse) is slightly inferior in the wire test. The other undercoat materials and those sprayed with gray alumina (coarse) all showed excellent results in terms of scratch strength and thermal shock resistance.

(The margin below)

[Table 1] 1) NiCr-Al is a NiCr (20 wt%) alloy
It is a component consisting of 95 wt% and Al 5 wt%,
(M) indicates that the particle size is medium. 2) Ni-Al 1 is Ni 95 wt%, Al 5 wt
%, And (L) indicates that the particle size is coarse. 3) Ni-Al 2 is Ni 80 wt%, Al 20w
It is a component consisting of t%. 4) Draw two parallel scratch lines to indicate the minimum width at which the film does not peel. 5) After heating at 850 ° C for 10 minutes, quenching in water is repeated 5 times. ○ No peeling or blistering occurred after 5 times. × Crack once

A combustion catalyst was prepared by supporting a metal on the ceramic film which showed excellent results in the above test. The metal was carried by the method shown in FIG. However, when the thermal shock resistance test of the film supporting this catalyst was carried out,
Surprisingly, swelling or peeling occurred in one to two repeated tests. Examples of the metal salt in FIG. 1 include tetramine dichloroplatinum [Pt (NH ₃ ) ₄ Cl ₂ ].
However, as the aluminum salt, for example, aluminum nitrate sol can be used.

Example 1 A copper plate material was used, and the surface thereof was nickel-plated by an electroless plating method. The conditions are as follows. Pretreatment: 20% hydrochloric acid immersion, water washing Temperature: 90 ° C Time: 100 minutes Plating thickness: 20 μm Posttreatment: 200 ° C, heating for 60 minutes When the cross section of the nickel-plated copper plate was observed under a microscope, nickel was evenly distributed on the copper plate. It was confirmed that the film was in close contact with the thickness of. An undercoat material and a ceramics-based thermal spray material were immediately sprayed onto the nickel-plated copper plate without roughening the surface by blasting as a pretreatment. The thermal spraying conditions are the same as in Comparative Example 1. Further, a metal was supported on this surface to prepare a combustion catalyst. The supporting method is the same as the method shown in Comparative Example 1 (FIG. 1). The thermal shock resistance test of the thus prepared combustion catalyst was conducted. The test condition is to keep the temperature at 850 ° C for 10 minutes and then rapidly cool it in air 10 times.
After maintaining for 10 minutes, the operation of rapidly cooling in water is repeated 5 times. The test results are shown in Table 2. As a result, neither swelling nor peeling occurred.

[0013]

[Table 2] 6) Ni-Al is Ni 80 wt%, Al 20 wt%
(L) has a coarse particle size. 7) MoNi-Al is a composite of MoNi and Al. 8) No peeling occurs when the operation of keeping at 850 ° C. for 10 minutes and then rapidly cooling in air is repeated 10 times. 9) No peeling occurs when the operation of quenching in water after maintaining at 850 ° C for 10 minutes is repeated 5 times.

Example 2 A copper plate was nickel-plated, a layer of molybdenum-nickel-aluminum undercoat material was formed on the copper plate, and a coating of plasma-sprayed gray alumina was formed thereon.
Further, a layer supporting platinum was sequentially formed on a coating of gray alumina plasma-sprayed on stainless steel to prepare a combustion catalyst, and the combustion activity evaluation test was performed. A system as shown in FIG. 2 was used as the combustion system, and kerosene was used as the fuel. The test results are shown in FIG.
The copper plate and the stainless steel carrying the catalyst show the same excellent combustion activity.

[0015]

[Effect] According to the present invention, it is possible to provide a combustion catalyst in which copper and a copper alloy have a ceramic coating excellent in thermal shock resistance as a carrier. Further, since it is not necessary to blast the surface of copper or copper alloy, the base material is not damaged or deformed.

[Brief description of drawings]

FIG. 1 is a flow sheet for catalyst preparation.

FIG. 2 shows a combustion system used in Example 2 for evaluating catalytic combustion activity.

FIG. 3 is a graph showing the catalytic combustion activity evaluation results of Example 2.

Claims (5)

[Claims] 1. A combustion catalyst comprising a metal support made of copper or a copper alloy, a high temperature oxidation resistant metal layer, an undercoat layer, a porous ceramics layer and an oxidation catalyst carried on the porous ceramics layer. . 2. The combustion catalyst according to claim 1, wherein the metal forming the high temperature oxidation resistant metal layer is a Group 8 metal of the periodic table. 3. The combustion catalyst according to claim 1, wherein the metal support is a metal component for combustion equipment. 4. The combustion catalyst according to claim 3, wherein the metal component of the combustion device is a heat exchange fin. 5. An undercoat layer is formed by plating a metal surface made of copper or a copper alloy with a high temperature oxidation resistant metal, and then plasma spraying a metal spray material, and further, a ceramics spray material is formed thereon. A method for producing a combustion catalyst, comprising forming a porous ceramic layer by plasma spraying and then supporting an oxidation catalyst on the porous ceramic layer.