JPH0813334B2 - Self-cleaning coated surface - Google Patents

Description

TECHNICAL FIELD The present invention provides a coated surface having a catalytic action for preventing oil stains on the inner surface of a box-type heating cooker such as various ovens.

2. Description of the Related Art Conventionally, as a coated surface having such a catalytic action, a catalyst coating in which a catalyst substance containing an oxide or a complex oxide, an oxide of a rare earth metal, etc. as a main component is added to an enamel or glassy film. is there. All of these are intended to apply a catalyst dispersed in an inorganic binder to the inner wall surface of the chamber to form a coating layer to catalytically decompose oil and food residues at high temperature.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Oxygen diffusion is indispensable for effectively exhibiting catalytic activity, but in the prior art it is a state in which the catalyst is covered in a film such as enamel, glass, and paint. There is a need to make the coating as porous as possible.

Therefore, although it is effective in terms of catalytic ability, there is a big problem that the physical properties of the film, that is, the adhesiveness, the corrosion resistance, the wear resistance and the like must be sacrificed. This is a big problem in practical use. The two-coat, two-bake method is used in the conventional catalyst coating for the purpose of enhancing the adhesion or improving the corrosion resistance, but the film thickness is several hundreds μ, which makes it difficult to process the complicated shape and the baking temperature. Becomes extremely high temperature, making it difficult to process thin plates. Further, since it is formed of enamel or glass, it is vulnerable to thermal shock, has problems in mass productivity, and has a problem of high cost.

Means for Solving the Problems In order to solve the above problems, the present invention is a Mn, Cu, Ce-based complex oxide or Mn, Cu, Ce, Co-based complex oxide on the heat-resistant substrate surface by plasma spraying. Which forms a coating surface for self-cleaning consisting of a sprayed layer of this catalyst either alone or in combination, and which continuously decomposes oil scattered from the cooked product on this coating surface. Is.

Action The following action is obtained by the configuration of the coated surface. The catalyst of the present invention is an oxidation catalyst having an extremely strong oxidation ability and forms a single film of the oxidation catalyst by plasma spraying.
Since the film itself is a catalyst, it is not hardened by covering the catalyst with frit or binder like enamel, glass or paint.

In order to proceed the catalytic reaction most effectively, increase the contact area with the catalyst to increase the reaction rate and reaction efficiency, and more importantly, constantly supply oxygen to the reaction interface between the catalyst and oil. Is. When there is a certain temperature and it is in an oxidation reaction state, it is carried out with oxygen of the oxide itself, which is a catalyst, but with conventional oxidation catalysts, the composition of the catalyst itself gradually becomes a lower oxide in a relatively short time and lacks stability. However, there was a change in color, and performance was to drop sharply. This was even more the case when the catalyst surface was covered with frit or binder as described above, or when the catalyst surface was covered with a large amount of oil or dirt.

Oxygen in the bulk is consumed by the reaction of hydrocarbons such as oil and the catalyst, the consumed oxygen is easily replenished from the surface, and the coating layer according to the present invention does not stop the supply of oxygen from the bulk. In the case of the catalyst structure, the inconvenience that the catalytic reaction efficiency is reduced in a short time and the catalytic activity is not exhibited does not occur at all.

The serif-cleaning coated surface of the present invention in which the film itself is a catalyst is that the catalyst and the oil content are in direct contact, oxygen is sufficiently supplied to the reaction interface, and Ce that supplements oxygen in the catalytic reaction in the bulk is Ce. And Co are contained and dispersed in the coating film, and these stabilize the Mn and the like, thereby dramatically improving the catalytic performance.

Examples Examples of the present invention will be described in detail below.

The catalyst was prepared by the precipitation method. Carbonates, acetates, nitrates and the like are used as starting materials, but nitrates were used here. For 5 kinds of Mn, Cu, Mn-Cu, Mn-Cu-Ce and Mn-Cu-Ce-Co, PH was almost 7 after precipitation of each hydroxide by adding excess NaOH to the aqueous nitrate solution. It was thoroughly washed until it became dry, dried and calcined at 450 ° C. for 2 hours to obtain the above-mentioned five kinds of catalysts. The composition of the catalyst is 1: 1 (molar ratio) for Mn-Cu, 1: 1: 2 (the same) for Mu-Cu-Ce, and 1: 1 for Mn-Cu-Ce-Co.
1: 2: 0.25 (same).

Plasma spraying was performed on a stainless steel substrate (plate thickness: 1 mm) that had been subjected to blast treatment using the above five types of catalyst powder to form a catalyst sprayed film with a film thickness of 20 μm.

The plasma spraying was performed using an NT30 type DC plasma spray device manufactured by Nagata Iron Works Co., Ltd.

Using this as a test piece, the ability to purify oil at 370 ° C was confirmed. A certain amount of salad oil was dropped on the test piece and 370 ℃
It was kept in an oven to see the change in salad oil.

 The results are shown in the table below.

From the above results, Mn-Cu-Ce composite oxide and Mn-Cu-Ce-
It can be seen that the promoting effect on the oxidation reaction of the Co composite oxide is extremely large. Mn-Cu-Ce
The -Co system seems to be superior, but the difference is slight.

About 1 μ of salad oil was added dropwise to the catalyst powder to heat it, and it was confirmed at what temperature the combustion of the salad oil started.

In the Mn-Cu-Ce system, the development of combustion was confirmed at about 240-250 ℃. Combustion also occurred at almost the same temperature in the Mn-Cu-Ce-Co system. With Mn oxide and Cu oxide, the same phenomenon does not occur even at 300 ° C, and the difference in catalytic activity is clear.
It can be seen that the -Cu-Ce-Co system is particularly suitable for the decomposition of oil. Since it is a complex oxide, it promotes the oxidation reaction due to the complex effect, and Ce and Co serve as a supply source of oxygen to Mn, especially in the bulk. It is thought that it is.

As described above, according to the present invention as described above, the catalytic activity of the Mn-Cu-Ce-based or Mn-Cu-Ce-Co-based composite oxide having extremely high catalytic activity on the surface of the substrate by plasma spraying is used. Since the self-cleaning coating layer consisting of the sprayed layer of the catalyst is formed, the contact area of the catalyst and the oil content is large, and the plasma spray coating is a porous film with suitable porosity, so the reaction interface between the catalyst and the oil content is large. Sufficient oxygen is supplied. Therefore, the oxygen consumed in the oxidation reaction is also replenished from the inside of the film and from the air, so that the catalytic activity can be maintained for a long time without deterioration in performance.

By applying the self-cleaning coated surface of the present invention to the inner wall surface of an oven or the like, it was necessary to maintain the temperature at 500 to 550 ° C. in the case of performing thermal self-cleaning in a conventional baking oven, but this was 400 It is possible to reduce the temperature to below ℃, which has a great effect on energy saving and heat insulation. Further, since the oil stains can be completely decomposed, the inside of the oven can be kept long and can be maintained in a state like a new one.

[Brief description of drawings]

FIG. 1 is a sectional view of a self-cleaning covering surface according to an embodiment of the present invention. 1 ... Insulating base material, 2 ... Plasma spray catalyst coating.

Claims (1)

[Claims] 1. A composite metal oxide of Mn, Cu, Ce or Mn, which is a self-cleaning coated surface for forming a sprayed layer of a catalyst on the surface of a heat-resistant substrate by plasma spraying to continuously decompose dirt. A coating surface for self-cleaning, which is composed of a sprayed layer formed by a catalyst of any one of the complex metal oxides of Cu, Ce, and Co.