JPH03157141A - Self-cleaning catalytic body and heating cooker - Google Patents

Abstract

PURPOSE:To obtain the catalytic body having cleaning performance and surface hardness by covering a catalytic body consisting of ceramic fibers carrying a catalyst with a porous body consisting of metallic fibers carrying a catalyst. CONSTITUTION:The oxides of rare-earth or transition metals such as Ce, Cu and Mn are used as the oxidation catalyst 1. The catalytic body 2 contg. the catalyst 1 and consisting of the ceramic fibers consisting essentially of SiO2, Al2O3 and ZrO2 is covered with the porous body 3 carrying the catalyst 1 and consisting of fine metallic fibers of stainless steel. Consequently, the porosity is increased, contact of the catalyst with oil is improved, oxygen is sufficiently supplied, and the strength is raised. Accordingly, the catalytic body is set on the inner wall surface of a cooker to clean off the oil deposited on the wall surface.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention provides a catalyst body having a function of decomposing and removing dirt generated during cooking in a heating cooking device such as an oven or a grill, and a catalyst body coated with the catalyst body. This relates to a heating cooker.

BACKGROUND ART There are three main methods for decomposing and removing dirt that adheres to the inner wall of a cooking appliance when cooking meat, fish, etc., using heat.

The first method is to form an enamel coating on the inner wall of the chamber, raise the temperature inside the chamber so that the enamel surface temperature is approximately 450° C. or higher, and use heat to decompose dirt on the enamel surface.

The second method uses inorganic metal phosphates, silicates, or enamel as a binder, along with Mn and Cu.

This is a case where a porous membrane in which transition metal oxides such as Fe, Co, and Ni or alkaline earth oxides are dispersed as a catalyst is formed on the inner wall surface of the refrigerator.

Such a film burns and decomposes oil stains at low temperatures using the catalytic action of metal oxides.

The third method uses inorganic metal phosphates, silicates, or enamel as a binder, and disperses metal oxide powder or noble metal powder to form a coating, which is then made into a metal porous body.
This is a case in which the catalyst body is coated thinly enough that the surface shape of the metal porous body remains and is formed on the inner wall surface of the refrigerator. (for example,
(Japanese Patent Publication No. 59-40062) Problems to be Solved by the Invention However, the above-mentioned conventional technology has the following problems. In enamel, if the temperature exceeds 500°C, cranking will occur and peeling will occur. As a result, the iron base material corrodes and becomes unusable as a cooker.

In addition, for porous membranes using phosphates or silicate as a binder, the coating must be made as porous as possible to increase the contact area between the oil and the catalyst and to improve oxygen diffusion within the coating to ensure complete combustion of oil stains. Otherwise, purification performance cannot be obtained.

However, if it is made porous, the hardness will be low and it may peel or be damaged, which poses a practical problem. Furthermore, burning causes residual tar components and ash to enter the porous spaces and settle there, which may gradually reduce purification performance.

Also, when paint is applied to a porous metal body, the oxide or noble metal powder is covered with a binder and its activity is reduced.In order to completely burn out the oil stains, a porous metal body with as high a porosity as possible is used to increase oxygen diffusion. There must be.

However, on the other hand, if the porosity is high, problems such as clogging and appearance make the wall unsuitable for practical use as an inner wall of a refrigerator. Furthermore, metals generally have poor wettability with oil, and the above method of applying an oxide using a binder requires baking at 400'C for 2 hours or more, which is not practical.

As mentioned above, there are some problems with the conventional technology, but in the present invention, by providing a catalyst body with high surface hardness on a catalyst body with high porosity, a catalyst body that has both purification performance and surface hardness is created. This is what we provide.

Means for Solving the Problems In order to solve the above problems, the present invention improves purification performance and catalysis by covering a catalyst body made of ceramic fibers carrying a catalyst with a porous body made of metal fibers also carrying a catalyst. Strength and appearance of media surface.

A catalyst body that is smooth is formed, and this catalyst body is used on the inner wall surface of a cooking appliance to clean oil stains that are generated during cooking and adhere to the inner wall surface of the refrigerator.

action The action of the catalyst body with the above configuration will be explained.

First of all, the porous body made of ceramic fibers used in the present invention (hereinafter referred to as ceramic fiber porous body) is made of laminated ceramic fine fibers and has a very high porosity. The oxidation activity of the catalyst can be fully exerted due to sufficient contact with the catalyst and sufficient supply of oxygen. However, its surface hardness is low and it is not suitable for practical use alone. Furthermore, since the porous body made of metal fibers (hereinafter referred to as metal fiber porous body) used in the present invention uses A1 or stainless steel as the material of the metal fibers, it has extremely high strength compared to ceramic fibers.

Furthermore, since the fibers are laminated with very fine fibers with an average fiber diameter of several microns, the porosity is high.

However, compared to ceramic fiber porous materials, metal fiber porous materials have poor wettability with oil and allow oil to pass through them easily.

Therefore, if a metal fiber porous body supporting a catalyst is used alone,
The oil that passes through enters the gap between the inner wall of the cooker and the porous metal fiber body, accumulates, and turns into tar.

Therefore, in the present invention, a metal fiber porous body is coated on a ceramic fiber porous body, and the oil that has passed through the ceramic fiber porous body is retained in the ceramic fiber porous body that has good wettability with oil and is oxidized and decomposed.

In addition, a catalyst was also supported on the metal fiber porous body in order to oxidize and decompose some of the oil that adhered to the metal fiber porous body.

Furthermore, since the ceramic fiber porous body, which is the site of the oxidative decomposition reaction, releases less heat than metal, the heat from the heater can be used efficiently for the oxidative decomposition.

Further, in the present invention, the oxides to be contained in the ceramic fiber porous body and the metal fiber porous body include Ce, CuMn, Co
, Ni, and Fe. At least one kind of rare earth or transition metal oxide was used. Since these oxides exhibit high activity against oxidative decomposition of hydrocarbons such as oil stains, there are no particular limitations on the composition.

However, as an example, in the present invention, Ce and Cu are used.

Mn complex oxide (hereinafter this complex oxide will be expressed as Ce
Denoted as Cu, Mn+-*o, (0<x<1.)'>O). However, it does not indicate the structure. ) was used. The composite oxide exhibits higher activity for oxidizing hydrocarbons than composite oxides of a single element or two elements. This is because in ternary oxides of Ce, Cu, and Mn, the elements on the surface of the oxide have many valences (for example, Mn is trivalent and tetravalent, Cu is monovalent and divalent, etc.). This is because valence control between different elements, which cannot be seen in single or two-component systems, is achieved, creating a more permeable surface for reactions. This is recognized in XPS.

Example The present invention will be explained below using an example.

As for the catalyst, as mentioned above, for example, CeC
u, MJ-x o, (0<x<1.y>0) was used.

First, the manufacturing method of the catalyst body will be explained.

Silica/alumina fibers (
Sin, :A1. Os! =+:l: 1. The average fiber diameter was 2.8 μm, the porosity was 92%, and the thickness was 1 mm.

The metal fiber porous material is made by laminating fine fibers of austenitic stainless steel and has a thickness of 0.5 mm (porosity: 6).
5-80%) and 1m thick AI nonwoven fabric sandwiched with AI expanded metal (porosity 50-60%).
%) was used.

In addition to this, a porous material made by sintering fine powder of stainless steel can also be used.

CeCux describes three methods for supporting catalysts.
This will be explained by taking Mn+-+t O, (0<x<1.)I>0) as an example. The first method is to mix nitrates of Ce, Cu, and Mn in a predetermined molar ratio, make an aqueous solution, and add Na
An alkaline aqueous solution such as OH or Na t COs is added to precipitate Ce, Cu, and Mn in the form of hydrates. Next, this precipitate is washed with water until it becomes neutral, dried, and then calcined at a temperature of 450° C. or higher. The resulting oxide is crushed with a pestle and turned into powder. This is a method in which the fine powder of the oxide thus obtained is directly dispersed in a porous ceramic fiber body and a porous metal fiber body.

The second method is to mix nitrates of Ce, Cu, and Mn in a predetermined molar ratio and make an aqueous solution using a spray gun.
An example of spray conditions: DeVilbiss spray gun, nozzle diameter 1.4 φ, air pressure 1, 5 to 2 g/cm'')
This is a method in which the coating is coated with water and baked at 450°C or higher for about 30 minutes.

Thirdly, nitrates of the same <Ce, Cu, and Mn are mixed in a predetermined molar ratio, and the ceramic fiber porous body and the metal fiber porous body are directly dipped in an aqueous solution.
There is a method of baking at 50°C or higher for about 30 minutes.

FIGS. 1 and 2 show conceptual cross-sectional views of a catalyst body that is an embodiment of the present invention.

Figures 1 and 2 show that fine oxide powder is directly dispersed in the ceramic fiber porous body 2 and the metal fiber porous body 3 as shown in the first of the three catalyst supporting methods described above. ,
The metal fiber porous body is made by sandwiching two layers between supports 4, and the metal fiber porous body shown in FIG. Indicated.

Next, the oil purification performance of the catalyst body thus prepared will be explained.

Fine powder of oxide (Ce:
Cu:Mn-r: 0.3: 0.7 (650°C firing)
) dispersed at 5.10.25.50% by weight, (
A, B, C, D) respectively, and a laminated plate of stainless steel mesh fine fibers dipped in a metal salt aqueous solution and fired (E) (Oxide supported amount: 20% by weight) Oxide fine powder 2
A1 nonwoven fabric in which 0% by weight is dispersed is made of AI expanded metal (F), and D and E,
The evaluation was made by stacking D and F with D facing down.

The evaluation method was to drop 0.15 g of salad oil onto a test piece of oilrr, place it in an oven maintained at a desired temperature, and give an evaluation of ○ if the salad oil was completely baked, and a × if it could not be baked.

The results are shown in the table below.

From the margin table below, it can be seen that with the catalyst used in the present invention, salad oil can be baked at 300°C if the catalyst is supported at 25% by weight or more based on the weight of the ceramic fibers. Also, this time A-D is 65
Although a catalyst calcined at 0°C was used, it has been found that the catalyst of the present invention has higher activity when calcined at a lower temperature of about 450°C to increase the amorphous portion. It is estimated that by firing the catalyst at a low temperature, the temperature at which oil stains are burned off is further lowered.

E and F were based on Ce, Cu, and Mn, and were fired at 450°C.

Judging comprehensively, both the ceramic fiber porous material and the metal fiber porous material can burn off oil stains at about 300°C.

However, since metal fibers alone have poor wettability with oil, their activity is lower than that of porous ceramic fibers.

Therefore, if metal fibers and ceramic fibers are used in layers (G
, H) The oil that has passed through the metal fiber porous body is decomposed within the ceramic fibers, and a small amount of oil adhering to the metal fibers is also decomposed, so the oil can be completely burned off.

Next, the surface strength, which is another feature of this catalyst, will be explained.

Six types of seasonings: vinegar, soy sauce, ketchup mayonnaise, sauce, and curry powder were added to the same catalyst as used in the above evaluation of the grilling performance of salad oil at 0.15% each.
g was added dropwise and heated at 380"C for 1 hour. As a result, G
, H, vinegar, soy sauce, and sauce were burnt without a trace, ketchup had hard black ash, mayonnaise had white ash, and curry powder had black ash on the catalyst. However, the ash came off cleanly when wiped with a cloth. Since the high-strength metal fiber porous body is on the top surface, the surface strength seems to pose no practical problem.

Next, the above catalyst body was actually attached to the inner wall surface of the cooking appliance. A sectional view is shown in FIG. The attachment can be done by adhesion or by welding the support of the catalyst body and the internal wall surface 6 of the refrigerator, but in this case, the support was spot welded to the internal wall surface 6 of the refrigerator.

FIG. 4 is a plan view of the surface of the catalyst used in the cooking device assembled here. Each side of the cooking chamber has the appearance shown in FIG. 4, and there is a catalyst surface 8 and a supporting frame 9, and the supporting frame 9 and the cooking chamber wall 6 shown in FIG. 3 are in contact with the gas bottle. ing.

Figure 5 is an external view of the cooker assembled here, with the cooking chamber door removed.

When we actually cooked poultry and fish 7, which tend to produce oil, and observed the stains on the surface of the catalyst after cooking, we found that almost no oil stains were observed.

In addition, the surface of the metal fiber porous material has a good feel and appearance, and it seems to be suitable as a wall material for a cooking appliance.

As explained in detail, the catalyst of the present invention is porous and has a very high ability to decompose oil stains. Yumata's surface is strengthened with metal fibers that can cleanse oil stains on the surface, giving it a good appearance and feel, and remaining ash and deposits can be easily wiped off. The inner wall surface of the cooking cabinet can be kept clean forever.

[Brief explanation of the drawing]

1 and 2 are conceptual cross-sectional views of a self-cleaning catalyst according to an embodiment of the present invention, FIG. 3 is a cross-sectional view of a cooking appliance using the same self-cleaning catalyst, and FIG.
The figure is a plan view of the surface of the self-cleaning catalyst, and
The figure is an external perspective view of the cooking device. DESCRIPTION OF SYMBOLS 1... Oxidation catalyst, 2... Porous body made of ceramic fibers, 3... Porous body made of metal fibers, 4... Support material, 5... ...Expanded metal, 7...To be cooked, 8...
Catalyst surface.

Claims (4)

[Claims] (1) Contains oxidation catalyst, SiO_2, Al_2O_3, Z
A porous body made of ceramic fibers containing at least one kind of oxide among rO_2 as a main component, a porous body made of metal fibers containing an oxidation catalyst, and a porous body made of the ceramic fibers and the metal fibers. The oxidation catalyst includes Ce, Cu,
A self-cleaning catalyst using at least one rare earth or transition metal oxide selected from Mn, Co, Ni, and Fe. (2) The porous body made of metal fibers is a laminate of fine metal fibers, a plate-shaped long metal fiber with expanded metal provided on at least one side and sintered, or a patent for sintering metal powder. A self-cleaning catalyst body according to claim (1). (3) Contains oxidative decomposition catalyst, SiO_2, Al_2O_
3. A porous body made of ceramic fibers containing at least one kind of oxide among ZrO_2 as a main component, a porous body made of metal fibers containing an oxidation catalyst, and a porous body made of the ceramic fibers and the metal fibers. a porous body and a support sandwiching the porous body, and as the oxidation catalyst, Ce,
A heating cooker in which a self-cleaning catalyst body using at least one kind of rare earth or transition metal oxide selected from Cu, Mn, Co, Ni, and Fe is provided on the inner wall of the cooking chamber. (4) The porous body made of metal fibers is a laminate of fine metal fibers, a plate-shaped long metal fiber with expanded metal provided on at least one side and sintered, or a patent for sintering metal powder. A heating cooker according to claim (3).