JPH0360738A - Catalytic body for purification of smoke - Google Patents

Abstract

PURPOSE:To obtain a low cost catalytic body for purification of smoke having high activity with superior productivity by using CeO2 and a solid basic compd. as oxidation catalysts and mixing them with ceramic fibers and a binder. CONSTITUTION:CeO2 and a solid basic compd. such as SrCO3 or BaCO3 are used as oxidation catalysts. Ceramic fibers of alumina or silica are mixed with a binder and the catalysts are added to the mixture and uniformly mixed. Water is then added so as to attain proper viscosity and the resulting slurry is molded and calcined. A catalytic body for purification of smoke is obtd. at a low cost because a noble metal is not used. This catalytic body is porous, has a high degree of dispersion of the catalysts and high activity and is easily produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to the use of unburned hydrocarbon compounds and monoxide discharged from various combustion appliances that use oil, gas, etc. as fuel, and from cooking appliances such as ovens, microwave ovens, and gas stoves. This invention relates to a purification catalyst that oxidizes and decomposes carbon.

Conventional technology For example, when considering cooking appliances, ovens and grills produce a large amount of smoke, oil smoke, and other odors when cooking meat or fish, and the kitchen is filled with smoke and dirt and odors remain in the heating chamber. Unfavorable situations may arise. To prevent this, by operating an exhaust fan motor that forcibly exhausts the air inside the heating chamber from the exhaust hole outside the heating chamber, water vapor, oil, and smoke generated from the food are exhausted outside the heating chamber. A method is adopted in which the water is purified by a purification catalyst in the middle of the process. As a purification catalyst, platinum, palladium, I'l
Commonly, a noble metal such as l-dium is supported on a ceramic honeycomb structure obtained by molding and firing ceramic powder particles such as phosphoric acid or alumina. In addition, instead of noble metals, vergeskite-type composite oxides and transition metals supported alone or with composite oxides are used.

Problems to be Solved by the Invention However, as mentioned above, the cost of using precious metals is extremely high, and the surface area of velogesite-type composite oxides is small because they are generally deposited at the bottom of a mine at a high temperature of 800 to 850°C or higher. There is.

Means for Solving the Problems In order to solve the above problems, the present invention uses C as an oxidation catalyst.
Using e0z and a solid base compound, ceramic fibers and a binder are mixed in advance, a catalyst body is formed into a bottom mold, and this catalyst body is used to purify the oil smoke in the heating chamber of a cooking appliance.

action The action of the oil smoke purification catalyst body according to the present invention will be explained.

If the structure of oil is represented by formula (1), (R1, R2, and R3 are saturated and unsaturated alkyl groups), the reactions necessary for purification include cutting of C--C bonds and oxidation to carbon dioxide and water.

This purification catalyst purifies oil smoke by utilizing the oxygen supply and auxiliary combustion effect of Cent under atmospheric conditions and the function of preventing carbon radical recombination by solid base, that is, suppressing tar formation.

Furthermore, since the aforementioned mixture of CeOx and a solid base is mixed in advance into a mixture of ceramic fibers and a binder and then molded into a bottom mold to form a purification catalyst, there is no need to support the catalyst afterwards as in the conventional case. Since it is used, the porosity is high, and the degree of dispersion of the catalyst and the contact rate with air are high.

Example An embodiment of the present invention will be described below with reference to the drawings.

First, the manufacturing method will be explained.

Cent is a product with a large specific surface area (approximately 180nf) that is obtained by adding ammonia water to an aqueous cerium nitrate solution, co-precipitating it in the form of a hydrate, thoroughly washing it with water to gradually remove the alkali, and drying it at the bottom of the mine. /g), and a commercially available reagent 5rCO was used as the solid base.

First, CeOx and S r C03 were weighed in a molar ratio of 1=1 and kneaded for 2 hours using an automatic kneader.

Next, Al-softened silica-based ceramic fiber 6 caps 1%, Zn
O-B2us'S fox glass powder 10% by weight,
Mixture 3 of C e Ox and S r COx described above
After uniformly mixing 0% by weight, water was added to obtain a suitable viscosity to prepare a slurry. Next, a ceramic sheet having a thickness of about 0.5 m was formed using the above-mentioned slurry by a papermaking method, and then fired in the air at 600'C for 1 hour. Furthermore, after being processed in one stage by corrugator, it was formed into a honeycomb shape by being wrapped or laminated.

Next, the characteristics of CeO, a solid base, will be specifically explained.

First, Ce0z has a large surface area in powder form and can store a large amount of oxygen, so it is often used as a cocatalyst. Furthermore, it is known that Ce cations can easily undergo redox between trivalent and tetravalent ions, and thus serve as a catalyst for liquid phase oxidation.

When salad oil was actually dropped onto Ce0r powder and heated, it began to burn and emit smoke at around 200°C.

Figure 1 (2) shows the results of dropping 5 μl of salad oil onto 20 cm of CeOz powder and measuring the weight change characteristics of the salad oil due to temperature rise using a thermobalance.

However, when hydrocarbons such as salad oil are decomposed and recombined, cyclic bonds and unsaturated bonds are generated, which are chemically adsorbed onto the catalyst surface and remain as tar without being purified.

As shown in Figure 1, this phenomenon gradually increases from 300'C to 500'C.
This is proven by the fact that even if the temperature is raised to 1, the salad oil is not completely burnt out and its weight continues to gradually decrease. So 5r
A solid base such as COx is added to repel generated carbon radicals and the base, thereby preventing adsorption of carbon radicals to the catalyst surface, stabilizing carbon radicals, and suppressing tar formation.

Figure 1 ■: Sr COs powder: 20■: salad oil: 5 μl
The results are shown in which the weight change characteristics of salad oil due to temperature rise were measured using a thermobalance under the same conditions as in the case of C e Ox described above.

In S r COs, the weight loss of oil is small up to 350°C, but when the temperature exceeds 350'C, the weight suddenly decreases and the oil is burnt out.

Even when salad oil was added to 5rCO,I powder on a hot plate and heated, the oil gradually turned black and turned into tar.
Surf and black material were observed to disappear from the surface above 0°C.

The oil smoke purification catalyst of the present invention has a bottom type in which a mixture of CeO, which has a large specific surface area and has a strong combustion-supporting effect, and a solid base compound that suppresses tar formation is dispersed in a ceramic fiber porous body with a high porosity. . There, the catalyst body is placed in an exhaust gas stream containing mist-like oil and unburned gas from the cooked food, and when heated to the temperature required for complete oxidation, the unburned hydrocarbons in the exhaust gas that pass through the catalyst body, - Carbon oxide is catalyzed together with oxygen on the catalyst body and converted into carbon dioxide and water vapor through an oxidation reaction.

Effects of the Invention As described above, the purification catalyst of the present invention uses a mixture of oxide and carbonate as a catalyst, so catalyst preparation (including calcination) is very simple. Since it is mixed with a binder and then molded, there is no need to support a catalyst afterwards as in the conventional method.

Therefore, productivity is excellent and cost is low. Also Sera [
Because it uses tsuku fiber, it is porous, and the catalyst has a high degree of dispersion and a large number of active sites, achieving high activation.

Furthermore, since it is a compound of CeO and a fixed base, it is a white to pale yellow catalyst and can be colored in any color. Further C
eO, has a thermochromic property that turns yellow when heated and returns to its original state when the temperature drops, so it has the characteristic that the rise in temperature of the catalyst can be visually detected.

[Brief explanation of drawings]

The figure shows CeO of an oil smoke purification catalyst in one embodiment of the present invention.
, and 5rCOs using a thermobalance.

Claims (3)

[Claims] (1) An oil smoke purification catalyst body consisting of ceramic fibers, a binder, CeO_2 as an oxidation catalyst, and a solid base compound. (2) The oil smoke purification catalyst according to claim (1), wherein the ceramic fibers are made of at least one of silica and alumina. (3) The solid base compound is SrCO_3, BaCO_3,
The oil smoke purification catalyst body according to claim (1), which is any one of the following.