JPS5853934B2 - Self-purifying catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-purifying catalyst that is coated on the inner surface and other surfaces of cooking appliances such as electric ovens to decompose oil.

The walls of the cooking chamber of food cooking equipment such as electric ovens are easily contaminated by flying debris and gas generated from heated foods, and especially when the flying debris is oily and fat-based, heating of the inner wall and contact with a high-temperature atmosphere may occur. It oxidizes and solidifies, making it extremely difficult to remove even with chemicals and detergents.

Considering that the device is a food cooking device, it goes without saying that it is extremely important for food hygiene to keep the inner wall located close to the cooked food clean.

From this point of view, research is currently underway to coat the walls of the cooking chamber with a catalytic material that catalytically oxidizes and decomposes oil, fatty substances, and the like.

By the way, various catalysts are already known for decomposing oily substances, but this type of catalyst used in food cooking equipment has the ability to effectively decompose oil and fat substances, in addition to its normal catalytic action, especially when used in small amounts. It must be effective, that is, it must have good resolution, it must have a long lifespan with little poisoning effect against various oils, fatty substances, gases, etc. that are scattered from various miscellaneous foods, and it must be harmless to the human body. Because certain things are required, we have not yet found anything that meets these requirements.

This invention has been researched and developed in view of the above points, and is made by supporting high-purity activated alumina with an oxide of at least one transition metal selected from the transition metals in the fourth period of the periodic table. , a self-purifying catalyst that decomposes oily substances suitable for food cooking.

More specifically, this invention has great significance in that activated alumina is used as a carrier.

The component properties of the activated alumina used greatly affect its ability to decompose oily substances, and first of all, it needs to be highly pure.

For example, the following Table 1 shows the results using a catalyst in which 10% by weight of MnO2 was supported by activated alumina and the catalyst was fired at a firing temperature of 400 DEG C. for 3 hours.

As we will see, activated alumina with a purity of 99.6% or higher is suitable, and impurities include alkali metals, silicon,
Sulfur is not preferred, and any of these is Na20 (or Ni20).

It has been found that the presence of more than 0.05 weight φ in terms of S 1o2t SO3 significantly degrades the resolution.

The oil removal rate was measured as follows.

After dropping 20 drops (approximately 130η) of salad oil onto a measurement sample plate, heat it in an oven at 200°C for 30 minutes and measure it.
The oil removal rate was determined using the following formula.

Such high-purity activated alumina can be easily made from metallic aluminum or organic aluminum salts, but it can also be made from other raw materials.

The transition metal oxide supported on the above-mentioned high-purity activated alumina can be used at relatively high food cooking temperatures, i.e., 3o0t.
Cr 9Mn should have good resolution at a certain temperature and excellent stability, especially considering deterioration caused by substances other than oily substances.

An oxide of at least one transition metal selected from Fe, CotNt, and Cu is preferable, and Mn is preferable in order to make coloring caused by oily substances less noticeable.
The tCotCu oxide is the most practical.

As is clear from the following Table 2, the content of the transition metal oxide is 5 to 50 weight φ based on the total weight of the catalyst to promote oil decomposition and exhibit a sufficient effect.

MnO2 was used as the oxidation catalyst, and the impurity content (wt%) of the carrier alumina was Na2O0,04,5i020.0
3. An SO3 trace obtained by firing at 400°C for 3 hours was used.

Similar results were obtained using other oxidation catalysts.

Such transition metal oxides can be produced by generally known methods.

A representative example thereof will be explained below.

Mancan oxide (MnOx) is produced by decomposing potassium permanganate with nitric acid, and is also produced from electrolytic manganese dioxide, manganese carbonate, manganese nitrate, etc.

Among these, it is preferable to make it from electrolytic manganese dioxide in terms of price and quality stability.

Copper oxide (CuOx) is produced from hydrated oxidized steel, basic copper carbonate, and oxidized steel obtained by adding alkali to a hot solution of divalent steel salt.

It is preferable to use the above-mentioned hydrated copper oxide in view of the internal specific surface area and the ability to diffuse onto the alumina carrier.

Cobalt oxide (CoOx) is produced from hydrated cobalt oxide, which is obtained by adding a mixed solution of alkali and sodium hypochlorite to a hot solution of divalent cobalt salt, basic cobalt carbonate, and cobalt acetate. From the viewpoint of specific surface area and dispersibility on the alumina carrier, it is preferable to use the above-mentioned hydrated cobalt oxide.

By calcining such an oxidation catalyst component at 2000 to 250°C, electrolytic manganese dioxide mainly becomes β--Mn.
02 and α-Mn203, hydrated copper oxide thermally decomposes to CuO at the above temperature, and hydrated cobalt oxide transforms into CO3O4.
It is something that changes.

Regarding the specific surface area of the catalyst, in order to effectively carry out the reaction in which oil is adsorbed onto the catalyst and oxidized and decomposed, the catalyst needs to have a large specific surface area, as shown in Table 3 below. , at least 100 mg is required, and 100
When it is less than m''/f!, the effect cannot be fully exhibited.

The samples used were catalysts in which MnO2 was supported on activated alumina and were fired at each temperature for 3 hours.

The catalyst of this invention will be explained below.

Example 1 262 g of sodium aluminate is dissolved in pure water to give a concentration of 2.51 g, and 94.59 g of sodium citrate is added thereto to completely dissolve it.

Next, a 7N nitric acid solution was added dropwise to this while keeping it warm at 50°C and stirring, and when the pH reached 7, the dropping was stopped.
Then, filtration, washing, drying, and pulverization are performed by well-known methods to obtain an alumina hydrate powder having a size of 150 mesh or less.

20 g of electrolytic manganese dioxide to 217 g of this alumina hydrate.
After adding 4 g of hydroxyethyl cellulose and dry mixing, 172 g of pure water was added and thoroughly kneaded.

The mixture thus obtained is dried at 130° C. for 16 hours, calcined at 400° C. for 3 hours, and then ground to 150 meshes or less.

An activated catalyst is thus obtained.

The composition of this catalyst is MnO2:A1203-10 in weight ratio.
:90.

The oil removal rate when using this catalyst was 45%, which was much better than conventional catalysts.

Example 2 262g of sodium aluminate was taken, and Example 1. Alumina hydrate powder of 150 mesh or less is obtained in the same manner as above.

To 217 g of this alumina hydrate, 76 g of electrolytic manganese dioxide was added.
After adding 4 g of hydroxyethyl cellulose and dry mixing, 172 g of pure water was added and thoroughly kneaded.

The mixture thus obtained was used in Example 1. The catalyst was activated in the same manner as above.

The composition of this catalyst is MnO2:A1203=30 in weight ratio.
Near 0.

The oil removal rate when using this catalyst was 42%, which was better than the conventional catalyst.

Example 3 A steel nitrate solution was prepared by dissolving Cu(NO3)2" 3H201639 in 11 parts of pure water, and 91 g of the copper nitrate was dissolved in 1 l of pure water and the copper nitrate was dissolved in a caustic potash solution kept at 75°C. Drop the solution.

The precipitate thus formed was filtered and mixed with hot water (6
00-65°C) 107, thoroughly stirred, and then filtered again.

This cleaning operation is repeated until NO3 ions are no longer detected.

The precipitate thus obtained is dried at 130° C. and then ground to 150 mesh or less to obtain hydrated copper oxide.

Example 1. To 252 g of alumina hydrate obtained by the method described above, 66 g of hydrated oxidized steel, 29 g of electrolytic manganese dioxide, and 7! of hydroxyethyl cellulose were added. ! After dry mixing, 183 g of pure water was added and thoroughly kneaded.

The mixture thus obtained was used in Example 1. The catalyst was activated in the same manner as above.

The composition of this catalyst is MnO2:CuO:A#20 in weight ratio
3=10:20:70.

The oil removal rate when using this catalyst was 47%, which was much better than the conventional catalyst.

Example 4 In the same manner as in Example 3, 88 g of electrolytic manganese dioxide was added to 66 g of hydrated oxidized steel obtained from a copper nitrate solution and a caustic potassium solution.
g, Example 1. Alumina hydrate 180 obtained by the method
After adding 6 g of hydroxyethyl cellulose and dry mixing, 144 g of pure water was added and thoroughly kneaded.

The mixture thus obtained was used in Example 1. The catalyst was activated in the same manner as above.

The composition of this catalyst is MnO2:CuO:A120 in weight ratio.
3-30:20:50.

The oil removal rate when using this catalyst was 42%, which was better than the conventional catalyst.

Example 5 20181 g of Co (NO3) 2 .6H was added to 11 g of pure water
to produce a cobalt nitrate solution, 126 g of KOH
The above cobalt nitrate solution was dropped into a mixed solution of caustic potash and sodium hypochlorite in which 464 g of Na0CA and 464 g of pure water were dissolved, and the resulting precipitate was filtered, washed, and dried in the same manner as in Example 3. , and grinding to obtain hydrated cobalt oxide of 150 mesh or less.

57g of this hydrated cobalt oxide and 25g of electrolytic manganese dioxide.
g, Example 3. 57 g of hydrated oxidized steel obtained by the method of Example 1. 154 g of alumina hydrate obtained by the method described above and 6 g of hydroxyethyl cellulose are added and dry mixed, and then 144 g of pure water is added and thoroughly kneaded.

The mixture thus obtained was used in Example 1. activated in the same way.

The composition of the catalyst thus obtained was MnO2 in weight ratio.
:CuO:CO3O4:A1203=10=20=20
:50.

The oil removal rate when using this catalyst was 40%, which was better than the conventional catalyst.

These catalysts 6? The oxidative decomposition ability of oil, that is, the oil removal rate according to :1 is summarized in Table 4 below.

As can be seen from this table, when using the product of this invention,
The oil removal rate is much better than that of the conventional method.

Not only the above compositions but also other catalysts according to the invention showed similarly good oil removal rates.

As described above, the catalyst of the present invention uses activated alumina of extremely high purity as a carrier, and contains at least one oxide of a transition metal in the fourth period of the periodic table such as Mn as an oxidation catalyst.
It has a specific surface area of 100 m2/9 or more, and has an extremely good oil removal rate compared to conventional products, and its oil decomposition ability is particularly good when coated on the inner walls of cooking equipment such as electric ovens. In addition, it satisfies the above-mentioned properties and is an industrially extremely useful self-purifying catalyst.

Claims (1)

[Claims] 1. A catalyst for catalytically oxidizing oil to decompose it into water and carbon dioxide, which contains an oxide of at least one transition metal selected from transition metals in the fourth period of the periodic table. A self-purifying catalyst characterized by being supported on a highly purified activated alumina carrier. 2 Transition metal oxide content is 5 to 5 with respect to the total amount of catalyst
The self-purification type catalyst according to claim 1, characterized in that the weight φ is 0. 3. The activated alumina support contains impurities such as alkali metals, silicon, and sulfur, each containing Na20 (or Na20). Claim 1 or 2, characterized in that both SiO2 and SO3 have a weight of 0.05 tbw.
Self-purifying catalyst described in Section 1. 4. The self-purifying catalyst according to claim 1, which has a specific surface area of 100 m2/g or more.