JPH0698308B2 - Cooking device - Google Patents

Description

Description: TECHNICAL FIELD The present invention can oxidize and decompose self-cleaning stains during cooking represented by oil stains under heating conditions in cooking appliances such as electric ovens, gas ovens, and grills. It relates to a cooker with the ability.

2. Description of the Related Art In the cooking oven or grill, when meat or fish is cooked, pollutants of oils are generated and are conspicuously attached to the wall surface inside the cooking chamber. It is not easy, and it is a direct cause that odors remain in the cooking chamber or stains remain forever and stand out. In order to eliminate such stains, the surface of the cooking chamber has been conventionally subjected to various surface treatments.

For example, an inorganic heat-resistant polymer such as an inorganic phosphate-based polymer is used as a binder to form a coating layer obtained from a composition in which a solid acid or a metal oxide is dispersed in the interior of a cooking chamber, or a transition metal in a enamel. There was a technique such as adding an oxide and forming a enamelous coating layer on the inner surface of the cooking chamber. In this case, solid acids and transition metal oxides are catalysts that oxidize and decompose oils above a certain temperature, and by forming a coating layer with such a catalytic action, it is possible to eliminate oil stains adhering to the inside of the cooking chamber. It is what In addition, there is a method to eliminate oil stains only by thermal decomposition without using a catalyst. In this case, a temperature of about 500 ° C and a time of 1 to 2 hours are required.

Problems to be Solved by the Invention The above-mentioned conventional techniques have problems in the following points.

First, the basic structure of oil is a triglyceride of a higher fatty acid, but the above solid acid and transition metal oxide do not decompose the oil unless the temperature is raised to 450 ° C or higher. Furthermore, by dispersing such a catalyst in a binder or enamel, the surface of the catalyst is covered and the exposed area becomes small, and the use of such a coating layer causes a decrease in activity. The effect of the coating layer becomes unclear because the oil itself will be thermally decomposed at temperatures above 450 ° C and above 500 ° C.

Secondly, when the coating layer temperature is maintained at about 400 ° C., the oil is carbonized and as a result, the coating layer is covered with tar-like material. The activity of the catalyst is low and tar-like substances do not disappear.

Thirdly, a high temperature of, for example, about 800 ° C. is required to obtain a enamel coating layer, and at such a high temperature, the surface area of the metal oxide becomes small and the activity also decreases.

As described above, the conventional coating layer has low activity and does not stain oil stains.
There was a problem that the catalyst could not be completely decomposed at 0 ° C or lower, and the cause was that the activity of the catalyst itself was low and that the surface of the catalyst was barely exposed. Obviously, the temperature during oxidative decomposition should be lower, including the problem of heat insulation in design.

The present invention solves the above problems and provides a cooker capable of decomposing oil stains at 400 ° C or lower.

Means for Solving the Problems In order to solve the above problems, the present invention forms a coating surface supporting a three-element composite oxide of Ce, Cu, and Mn on the inner surface of a cooking chamber of a heating cooker to form a composite oxide. CeCuxMn _1- x when expressed in xOy:
0 <x <1, y: 0 <y, and the coated surface has a porous film carrying a complex oxide, and the porous film has SiO ₂ , Al ₂ O ₃ , TiO ₂ , It is composed of one or more oxides of ZrO ₂ as a main component or enamel as a main component.

Action The present invention having the above-described configuration has the following actions. First, the action of a composite oxide composed of Ce, Cu, Mn (hereinafter referred to as CeCuxMn _1- xOy) will be described by taking salad oil as an oil.

Salad oil is a triglyceride of higher fatty acids such as stearic acid, palmitic acid, oleic acid, linoleic acid, and linolenic acid, and its general formula is as follows.

When triglyceride is oxidized and decomposed, not only CO ₂ and H ₂ O but also by-products such as aldehydes are generated. CeCuxM is used for oxidative decomposition of triglyceride including generation of this by-product.
n _1- x Oy is more active than conventional oxides. This is Ce
CuxMn _1- xOy has a larger surface area than conventional oxides,
Since it is composed of multiple elements, it is considered that the valence of the elements inside the oxide can be controlled and the valence state advantageous for the oxidation reaction is maintained.

Regarding the surface area, CeCuxMn _1- xOy has a surface area almost twice as large as that of MnO _X (0 <X) and CuO _X (0 <X). As a result, the activity as a catalyst is increased, and the reaction proceeds advantageously.

Regarding the valence, for example, when oxygen bound to Mn is involved in the reaction as shown in the following formula, It occurred by the formula (1) Is consumed by the reaction. However, in equation (2), from CuO Is supplied by this Is absorbed by oxygen-deficient Mn ₂ O _3- a, as shown in equation (3). Try to play Mn ₂ O ₃ . As you can see here Then Mn ₂ O ₃ will be completely regenerated. At the same time, according to the equation (4), Cu ₂ O is also oxidized and regenerated by oxygen in the air. In XPS, it is confirmed that Cu exists on the CuO rich side and Mn exists on the Mn ₂ O ₃ ich side on the surface of CeCuxMn _1- xOy.

If a coating surface containing CeCuxMn _1- xOy with high oxidative activity is formed in the cooking chamber as described above, dirt during cooking represented by oil dirt will be decomposed by the high oxidative activity of CeCuxMn _1- xOy. is there.

Example Hereinafter, the present invention will be described with reference to an example.

First, a manufacturing method of CeCuxMn _1- xOy will be described. Ce, Cu, Mn
In all cases, nitrate was mixed at a predetermined molar ratio to prepare an aqueous solution. Next, a method of coprecipitation with an alkali such as NaOH, Na ₂ CO ₃ and drying and baking (pyrolysis) was used. Of course, after coprecipitation, sufficient washing with water was performed to remove alkali. Finished
CeCuxMn _1- xOy was pulverized with a dairy bee to give a fine powder. In addition to the coprecipitation method, the oxide can be directly obtained by a thermal decomposition method.

Furthermore, when supporting CeCuxMn _1- xOy on a porous coating, a nitrate aqueous solution of each element is prepared in a predetermined molar ratio as described above, and the porous coating is immersed in this aqueous solution, dried, and baked (pyrolysis). went. In addition, a method of using an alkali to coprecipitate on the surface of the porous coating before drying was also performed.

When the size of the substrate coated with the porous film was large, a mixed aqueous solution of nitrate was sprayed instead of the dipping operation. When coprecipitating, alkali can be sprayed as well. In this way, CeCuxMn
_1- xOy can be supported.

Next, the surface area of CeCuxMn _1- xOy will be described. Table 1 shows the surface area by the BET method, but for comparison, C
The single oxides of e, Cu and Mn are also shown. All oxides were made by the coprecipitation method. Firing was carried out at 450 ° C.

The reason why the surface area as a whole is as large as about 70 to 120 m ² · g ⁻¹ is that the firing temperature is 450 ° C. and the temperature of the oxide is low. Further, the surface area of the composite oxide is larger than that of the single oxide. The cause of this is not clear so far, but it is largely due to the effect of Ce. Actually Ce / C
For uOxide and Ce / Mn Oxide, CuO and Mn ₂ O in Table 1 are used, respectively.
It was larger than the surface area of ₃ . In Table 1, CeCu _0.5 Mn _0.5 Oy
The surface area of CeCuxMn _1- xOy was shown to be dependent on x. From FIG. 2, it was found that the peak of the surface area was around x = 0.3.

Next, the XRD pattern of CeCuxMn _1- xOy and the measurement result of XPS will be described.

XRD pattern shows firing temperature of 400,450,550,650,750,900 ℃
However, there was no peak below 550 ° C. However, at 650 ° C or higher, crystallization gradually proceeded and a sharp peak was obtained. This change in the XRD pattern depending on the firing temperature is a natural result, but for reference, Mn
The carbonate (commercially available product) obtained by calcination at 550 ° C. showed a sharp peak of Mn ₂ O ₃ . Thus, CeCuxMn _1- xOy
The one baked at 450 ° C. is considered to be amorphous from a macro perspective. XPS data also showed that the valences of Mn and Cu on the surface of CeCuxMn _1- xOy varied with firing temperature. For example, when baked at 450 ° C, Mn +3, Cu +2, 7
Upon firing at 50 ° C., Mn shifted to +4 valence and Cu shifted to +1 valence. Therefore, the surface of CeCuxMn _1- xOy is
Microscopically, Mn is Mn ₂ O ₃ , and Cu is a complex oxide with a structure similar to CuO.

The oxidative activity of the above CeCuxMn _1- xOy salad oil was measured by DTA.
It was measured by. For the measurement, a commercially available salad oil and oxide were mixed at a weight ratio of 2.5: 1.0, mixed well, and put in a quartz cell to obtain a DTA curve. 4 shown in Table 1 in FIG. 3
The TG curves of various oxides are shown. In FIG. 3, it can be said that the oxidation activity is high when the weight reduction rate is high and the weight reduction is completed at the lower temperature side. Therefore, CeCu _0.5 Mn _0.5 Oy
Is clearly active and is effective as an oxidation catalyst. Figure 4 shows the dependence of CeCuxMn _1- xOy on the x of the TG curve. x = 0.3 seems to have the highest activity. This is considered to correspond to the dependence of the surface area on x. However, it is not sufficient to explain simply by the effect of the surface area alone, and it is conceivable that the schemes shown in the equations (1) to (4) will be optimal at x = 0.3 as an example.

The manufacturing method, surface area, structure, and oxidation activity of CeCuxMn _1- xOy have been briefly described above.

Hereinafter, a description will be given of a cooker in which the above oxide is supported on the porous coating and the coated surface obtained from the support is applied. The method for supporting the porous film has already been described. Here, as a multi-layered film (hereinafter referred to as a carrier), SiO ₂ , SiO ₂ -Al ₂
O ₃ , TiO ₂ , ZrO ₂ and porous enamel were used. The supported catalyst was CeCu _0.5 Mn _0.5 Oy.

The carrier (SiO ₂ , SiO ₂ —Al ₂ O ₃ , TiO ₂ , ZrO ₂ ) used here is
It can be obtained by using an inorganic polyphosphoric acid-based binder as a binder, mixing various oxides therein, coating it on a substrate, and then baking it. The oxide carrier can also be obtained by a thermal spraying technique such as a plasma spraying method. Further, in addition to the inorganic polyphosphoric acid-based binder, if necessary, a water glass-based or semi-organic-based binder (for example, one that becomes a ceramic after firing ...
Polyborosiloxane etc.) can be used.

First, a test piece was prepared by forming the above four types of carriers on a metal substrate of 5 cm × 5 cm, and using this test piece, CeCu _0.5 Mn _0.5 Oy was supported on the carrier.

FIGS. 5 and 6 show, as an example, CeCu _0.5 Mn _0.5 Oy on a SiO ₂ carrier.
The surface observation images by SEM and the distribution state of Mn by the surface analysis of XMA are shown, respectively. 5 and 6 are images on the same plane. It was confirmed by XMA that Cu and Ce were also uniformly distributed on the surface. From these observation results, it became clear that uniform loading was performed. The same was true when the carrier was SiO ₂ —Al ₂ O ₃ , TiO ₂ , ZrO ₂ , and porous enamel. Furthermore, the test piece supporting CeCu _0.5 Mn _0.5 Oy on the SiO ₂ carrier was maintained at about 370 ° C. on a hot plate, and 100 μ of salad oil was dropped on the surface for about 1 h.
It was oxidatively decomposed and the salad oil disappeared. CeCu _0.5 Mn _0.5 Oy
The supported amount was about 1 wt% with respect to SiO ₂ . However, the supported amount is not limited to 1 wt% and may be 1 wt% or less.

Next, for application to a cooking device, the above-mentioned SiO ₂ carrier is formed on a base material (metal such as stainless steel or aluminized steel plate) having a sufficient area to form a cooking chamber, and the Ce method is applied by a supporting method.
Cu _0.3 Mn _0.7 Oy was supported. Using this, a radiant heating type cooker as shown in FIG. 1 was created. The structure of the cooking device shown in FIG. 1 (a) has a coating surface 1 carrying CeCu _0.3 Mn _0.7 Oy, and heating is performed by radiant heating on a heater surface 2. First
The poultry meat was baked using the cooking device of FIG. (A), and the produced oil content was made to adhere to the coating surface 1 of the cooking chamber. After the completion of cooking, the chicken meat was taken out and the inside of the cooking chamber was maintained at a temperature of about 400 ° C. by a heater, and the oil stain disappeared in about 1 hour. The time until it disappears depends on the amount of oil, and if the amount is large, it takes about 2 hours.

FIG. 1 (b) is an enlarged conceptual view of a partial cross section of the covering surface of FIG. 1 (a). CeCu _0.5 Mn on the surface of porous SiO ₂ 4
_0.5 Oy 3 is supported. In addition, 5 is a metal base material.

In contrast to the above results, the above-mentioned chicken meat was cooked in a cooker to which a porous enamel containing a catalyst which has been conventionally used is applied, and after adhering oil, it was kept at 400 ° C. for 1 to 2 hours. However, the oil was never completely lost.

EFFECTS OF THE INVENTION As described above, according to the present invention, a coated surface containing a catalyst having high activity for oxidative decomposition of triglyceride of higher fatty acid such as salad oil, and a cooker having the coated surface can be obtained. Therefore, the following effects can be obtained.

(1) Since oil stains generated during cooking are oxidatively decomposed, the inside of the cooking chamber is kept in the initial clean state forever.

(2) In the conventional burn-out type cooker, it was necessary to raise the temperature to 500 ° C, but in the present invention, it is possible to raise the temperature to about 400 ° C, so that there is a design margin in the heat insulating structure, which leads to cost reduction and energy saving. Connect

[Brief description of drawings]

FIG. 1 (a) is a perspective view of a radiant heating type cooker as an embodiment of the present invention, FIG. 1 (b) is a conceptual view in which a partial cross section of a covering surface is enlarged, and FIG. 2 is CeCuxMn _1- Fig. 3 shows the dependence of surface area of xOy on x, Fig. 3 shows the TG curve by oxide thermobalance in Table 1, and Fig. 4 shows the TG curve of CeCuxMn _1- xOy to x. Fig. 5 shows the dependence of Ce on the SiO ₂ carrier.
SEM observation image of the surface when Cu _0.5 Mn _0.5 Oy was carried, and FIG. 6 is a distribution diagram of Mn by XMA of the surface in FIG. 1 ... CeCu _0.5 Mn _0.5 Oy-supported surface, 2 ... heater surface, 3 ... CeCu _0.5 Mn _0.5 Oy, 4 ... SiO ₂ carrier, 5 ... metal substrate.

Claims (2)

[Claims] 1. A cooking chamber inner surface of a heating cooker comprises a coating surface carrying a three-element composite oxide of Ce, Cu, Mn, and the composite oxide is represented by CeCuxMn _1- xOy, where x: 0 <x. Cooker where <1, y: 0 <y. 2. The coated surface is a porous film carrying a composite oxide, and the porous film is mainly composed of one or more oxides of SiO ₂ , Al ₂ O ₃ , TiO ₂ and ZrO _2. The cooking device according to claim 1, wherein the cooking device comprises an ingredient or an enamel ingredient as a main ingredient.