JP2010131531A - Air cleaning catalyst and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air cleaning catalyst which can efficiently remove a harmful substance present in the air such as carbon monoxide or formaldehyde, at low temperatures, e.g. not higher than 50°C and can be manufactured using a low cost raw material, at simple manufacturing facilities and by a simple manufacturing method. <P>SOLUTION: This air cleaning catalyst contains an equal density mixed oxide of manganese and cerium as a component A of the catalyst and at least one metallic element selected from the group consisting of elements belonging to groups VIII to XI of the periodic table as a component B of the catalyst. Further, the component A of the catalyst has an X-ray diffraction peak corresponding to the fluorite structure of cerium dioxide as a main peak. Besides, the equal density mixed oxide of manganese and cerium contains 10 to 60 mass% of manganese in terms of manganese dioxide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an air cleaning catalyst capable of removing harmful substances existing in the air such as carbon monoxide, ozone and volatile organic compounds at a low temperature of 50 ° C. or lower.

  Nitrogen oxides, volatile organic compounds, hydrocarbons, etc. discharged into the atmosphere from internal combustion engines and factories such as automobiles react with ultraviolet rays in sunlight to generate peroxides such as ozone, nitrogen dioxide, formaldehyde, etc. The generation of odor causes photochemical smog. Therefore, air pollution has been greatly improved by installing an exhaust gas treatment catalyst at the exhaust gas outlet of factories and automobiles. However, since the exhaust gas treatment catalyst does not function unless the exhaust gas temperature is set to 300 ° C. or higher, the fuel cost is required when the exhaust gas temperature in the factory is low, the maintenance cost becomes high, and the gas temperature at the time of starting or idling the automobile When it is low, there is a problem that harmful substances are discharged without being sufficiently treated.

  In addition, due to the improved airtightness of offices and homes, health hazards caused by harmful substances such as ozone and nitrogen oxides from copiers, unburned hydrocarbons and carbon monoxide from heating equipment, and acetaldehyde contained in cigarette smoke. I'm worried. Furthermore, it is known that interior materials such as wall materials, floor materials, curtains, and carpets generate harmful substances such as formaldehyde, toluene, and xylene that cause sick house syndrome.

  For removal of harmful substances at room temperature, methods using an adsorbent such as activated carbon, zeolite, molecular sheep, porous clay, activated alumina, and silica gel are known. However, the adsorbent has a lifetime, and it is necessary to replace the adsorbent regularly, for example, every few months, and excessive labor and cost are required to maintain its performance.

  It has also been proposed to use a photocatalyst as a method for removing harmful substances with a catalyst. Titanium oxide is generally used as a photocatalyst, but titanium oxide can oxidize and decompose harmful substances at room temperature by radicals generated by excitation with ultraviolet rays. However, since sunlight and indoor lighting contain only a small amount of ultraviolet rays, the processing speed is slow and practical effects have not been obtained.

Therefore, Patent Document 1 discloses a deodorization catalyst made of a complex oxide of manganese, iron and cerium. The composite oxide is described as being composed only of MnCeFe ₂ O ₄ , and there is no description as to whether the crystal structure by X-ray diffraction is a fluorite structure of cerium dioxide. In addition, an example of treating odorous substances such as acetaldehyde and trimethylamine at a reaction temperature of 150 ° C. is shown, and the treatment effect at a low temperature of 50 ° C. or less is not mentioned.

Further, a carbon monoxide oxidation catalyst in which palladium or platinum is supported on cerium oxide is disclosed in Patent Document 2, and monoxide is oxidized by supporting palladium or platinum on a surface layer having a depth of 0.8 mm from the surface of the molded body. It is described that carbon can be treated at a room temperature of 15 to 40 ° C.
Furthermore, Patent Document 3 discloses a room temperature purification catalyst in which a noble metal is supported on an oxide in which oxygen defects are introduced into cerium oxide or the like by reduction treatment, and an environmental load substance such as carbon monoxide or formaldehyde is efficiently produced at room temperature. It is described that it can be removed well. However, in the test results shown in the examples, the processing speed tends to decrease rapidly with time for any gas. This is considered to be due to the fact that by-products are generated without being completely oxidized, the structure of oxygen defects is not maintained by the reaction, and the performance is lowered. Further, a method of reducing at 500 ° C. for 1 hour in nitrogen containing 5% of hydrogen is exemplified, and the method for producing the catalyst is complicated.
On the other hand, in Patent Document 4, a manganese compound having a specific surface area of 150 m ² / g or more is applied to the surface of an automobile radiator or the like, and by running, it contains ozone, carbon monoxide, unsaturated hydrocarbons, etc. A method for purifying contaminants such as oxygen hydrocarbons is disclosed. In addition to ozone, the use of carbon monoxide and hydrocarbons in combination with platinum or palladium is also described. ΑMnO ₂ is said to be preferable as the manganese compound, and a cryptomelane (KMn ₈ O ₁₆ · xH ₂ O) structure measured by X-ray diffraction is disclosed as a more preferable crystal structure of manganese oxide.

Japanese Patent No. 3546766 JP 2008-264737 A JP 2001-187343 A Japanese Patent No. 4065026

  The present invention has been made to solve the above-described problems, and is an air purifier that efficiently treats low-concentration harmful substances such as carbon monoxide and formaldehyde in air at a low temperature of 50 ° C. or lower. It is to provide a catalyst for use. Moreover, the manufacturing method of this catalyst is simple and does not require complicated manufacturing equipment.

  In order to solve the above-mentioned problems, the catalyst for air purification of the present invention is selected from the elements belonging to Group 8 to 11 of the periodic table as the catalyst A component and the manganese-cerium homogeneous mixed oxide and the catalyst B component. At least one metal element, and the manganese-cerium dense mixed oxide contains 10 to 60% by mass of manganese in terms of manganese dioxide. It is identified as having a fluorite structure.

The air cleaning catalyst of the present invention contains 30 to 99.95% by mass of a manganese-cerium homogeneous mixed oxide as a catalyst A component, and at least one selected from palladium, platinum, silver and gold as a catalyst B component. It is preferable to contain 0.05-20 mass% of metal elements.
In addition to the catalyst A component and the catalyst B component, the air cleaning catalyst further includes at least one refractory selected from the group consisting of aluminum oxide, titanium oxide, zirconium oxide, zeolite, and titanium-based composite oxide as the catalyst C component. An inorganic oxide can be contained.
In the method for producing an air cleaning catalyst of the present invention, manganese-cerium is prepared by mixing cerium oxide or a precursor of cerium oxide as a catalyst A component and a manganese compound solution, drying the mixture, and firing in air at 300 to 900 ° C. It has the process of preparing an intimate mixed oxide. Under the present circumstances, it is preferable to add 0.1-2 mol organic acid with respect to 1 mol of manganese compounds to a manganese compound solution.

  The air cleaning catalyst of the present invention can efficiently remove harmful substances in the air at a low temperature of 50 ° C. or lower. Examples of the harmful substances include ozone, carbon monoxide, volatile organic compounds (VOC), hydrocarbons, sulfur compounds and nitrogen compounds.

  The manganese-cerium dense mixed oxide, which is the catalyst A component used in the catalyst for air purification of the present invention, can be produced with an inexpensive raw material, simple production equipment and production method, and is combined with the catalyst B component to be oxidized. It is possible to clean indoor air by completely oxidizing harmful substances such as carbon and formaldehyde at a low temperature of 50 ° C. or lower.

  The air cleaning catalyst of the present invention contains a manganese-cerium dense mixed oxide as a catalyst A component and at least one metal element selected from elements belonging to groups 8 to 11 of the periodic table as a catalyst B component. The manganese-cerium dense mixed oxide contains 10 to 60% by mass of manganese in terms of manganese dioxide, and has a fluorite structure of cerium dioxide by powder X-ray diffraction measurement. It is characterized by being.

  The manganese-cerium homogeneous mixed oxide of the catalyst A component of the present invention does not show a diffraction peak derived from manganese oxide when measured by powder X-ray diffraction, and is a crystal peak of fluorite-type cerium dioxide Is obtained as a main peak. The crystal structure of the powder sample can be confirmed by measuring the lattice spacing (d value). The measurement conditions for X-ray diffraction were a CuKα radiation source, a voltage of 45 KV, a current of 40 mA, a scanning range of 10 to 90 °, and a scanning speed of 0.198 ° / min. In the X-ray diffraction measurement results of the manganese-cerium dense mixed oxide obtained by the present invention, the d value of the main peak is in the range of 3.07 to 3.15, and the JCPDS (Joint Committee of Powder Diffraction Standards) card. This is almost the same as 3.12 which is the d value of the fluorite structure of cerium dioxide described in 1). The d value of cerium dioxide described on the card is 3.12, 1.91, 1.63, 2.71, etc. in descending order of relative intensity, and the positions (d value ± 0.05) a crystal peak was detected, and the crystal structure of the manganese-cerium dense mixed oxide is considered to be almost similar to the cerium dioxide fluorite structure.

  The manganese-cerium homogeneous mixed oxide which is the catalyst A component contains 10 to 60% by mass, preferably 15 to 50% by mass, more preferably 20 to 40% by mass in terms of manganese dioxide. In spite of containing manganese at such a high content, no diffraction peak derived from manganese oxide is observed, and therefore it is estimated that manganese oxide is highly dispersed on cerium oxide in an amorphous state.

  When the manganese dioxide-certain mixed oxide content in the manganese-cerium dense mixed oxide is less than 10% by mass, the oxidation rate of harmful substances becomes insufficient and efficient catalyst treatment cannot be performed. Manganese oxide tends to crystallize, leading to a decrease in heat resistance and poisoning resistance.

In general, the crystal structure of manganese oxide includes MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O _{4 and the} like, and especially MnO ₂ is known as active manganese dioxide and has a strong oxidizing power. ing. However, MnO ₂ is difficult to use in the catalytic combustion method because it easily undergoes a phase change by heat treatment. The manganese-cerium homogeneous mixed oxide obtained by the production method of the present application can only detect a fluorite-type crystal peak of cerium dioxide in the X-ray diffraction measurement even when heat-treated at a high temperature of 900 ° C. It has been found that a significant improvement effect can be obtained with respect to stability. Manganese oxide is highly reactive, and it is known that when sulfur compounds are present in the processing gas, it will be transformed into manganese sulfide or manganese sulfate, which tends to cause performance degradation. Manganese oxide is stabilized, and an improvement effect is obtained with respect to sulfur poisoning resistance.

The manganese-cerium homogeneous mixed oxide can be produced by a solid phase mixing method, a solid-liquid mixing method, a liquid phase coprecipitation method, a sol-gel method using an alkoxide, or the like. A particularly preferable production method is a solid-liquid mixing method that can produce a highly active homogeneous mixed oxide by using a simple production apparatus using an inexpensive raw material. The solid-liquid mixing method is prepared by using a solid raw material insoluble in a solvent that uses either manganese or cerium, and mixing it as a solution in which a metal salt is dissolved in a solvent such as water. Preferably, a cerium source is used as a solid raw material and a manganese source is used in a solution. Specifically, amorphous cerium oxide or a precursor of cerium oxide such as cerium carbonate or cerium hydroxide is impregnated with a manganese compound solution such as manganese nitrate, followed by drying and firing. By firing at 300 to 900 ° C. in the air, a manganese-cerium homogeneous mixed oxide having a specific surface area of 20 to 100 m ² / g can be prepared.

The metal elements belonging to groups 8 to 11 of the periodic table of catalyst B component include group 8 iron, ruthenium, osmium, group 9 cobalt, rhodium, iridium, group 10 nickel, palladium, platinum, and group 11 copper, Silver, gold, etc. can be used. It is preferable to use at least one element selected from palladium, platinum, silver and gold as the preferred catalyst B component.
The catalyst for air purification of the present invention comprises 30 to 99.5% by mass of a manganese-cerium homogeneous mixed oxide as the catalyst A component, and 0.05 to 0.05% of a metal element of Group 8 to 11 of the periodic table as the catalyst B component. It is preferable to contain 20 mass%. When the manganese-cerium homogeneous mixed oxide, which is the catalyst A component, is less than 30% by mass, the oxidation rate of harmful substances becomes slow and high treatment efficiency is difficult to obtain, preferably 50% by mass or more, more preferably 70% by mass. % Or more. In addition, when the amount of the metal element of Group 8 to 11 of the periodic table as the catalyst B component is less than 0.05% by mass, the oxidation performance at low temperature becomes insufficient, and even if it exceeds 20% by mass, the performance improvement effect is almost obtained. Therefore, it is not preferable because the dispersibility may decrease and the particles may grow. The catalyst B component is preferably contained as a metal of each element or a metal oxide.

  Moreover, it is preferable to use at least one element selected from palladium, platinum, silver and gold as the catalyst B component, and the use of these elements can improve the removal performance of carbon monoxide and VOC. It is particularly preferable that the oxidation performance at low temperature is remarkably improved by using a combination of palladium and silver as the catalyst B component, and the atomic ratio of Pd / Ag is preferably in the range of 50/50 to 1/99.

  The air cleaning catalyst of the present invention is at least selected from the group consisting of aluminum oxide, titanium oxide, zirconium oxide, zeolite, and titanium-based composite oxide as catalyst C component in addition to the above-mentioned catalyst A component and catalyst B component. One kind of refractory inorganic oxide can be contained. It is preferable to contain 0-69.95 mass% of refractory inorganic oxides. By adding a refractory inorganic oxide, it is possible to obtain an improvement in adsorption characteristics for harmful substances present in a low concentration in the air and mechanical strength of the catalyst. When the refractory inorganic oxide exceeds 69.95% by mass, the contents of the catalyst A component and the catalyst B component are decreased, and sufficient catalytic activity cannot be obtained, which is not preferable.

The refractory inorganic oxide is preferably a titanium composite oxide. The reason why the titanium-based composite oxide is excellent is not clear, but it is considered that the effect of promoting the oxidation of harmful substances at a low temperature is obtained by having a remarkable solid acidity. As the titanium-based composite oxide, it is preferable to use one selected from a Ti—Si composite oxide, a Ti—Zr composite oxide, and a Ti—Si—Zr composite oxide. In particular, Ti-Si composite oxide has a high specific surface area, is chemically and thermally stable, and is used in combination with the catalyst A component and the catalyst B component to provide an air purification catalyst having excellent adsorptivity. Can be configured. In particular, it is suitable for treating a gas containing a sulfur compound that causes a problem in oxidation treatment at a low temperature. When treating a low concentration harmful gas in the room, the specific surface area of the titanium-based composite oxide is preferably 100 m ² / g or more, and preferably 150 m ² / g or more. The titanium-based composite oxide preferably has a solid acid amount having an acid strength of pKa ≦ + 3.3 of 0.3 mmol / g or more.
Next, a method for producing an air cleaning catalyst will be described. As described above, the manganese-cerium dense mixed oxide which is the component of catalyst A can be produced by a liquid phase coprecipitation method or a sol-gel method, but is preferably produced by a simple solid-liquid mixing method shown below. .

  The specific method for producing the air cleaning catalyst of the present invention is to mix cerium oxide or a precursor of cerium oxide and a manganese compound solution sufficiently, and after drying, calcining in air at 300 to 900 ° C. It has the process of preparing a certain manganese-cerium homogeneous mixed oxide. As the cerium source, amorphous cerium oxide or a precursor of cerium oxide such as cerium carbonate and cerium hydroxide can be used. It is preferable to use as. As the manganese source, a solution of a manganese compound that can be dissolved in a solvent such as water such as manganese nitrate, manganese chloride, and manganese acetate can be used, and an aqueous manganese nitrate solution is particularly preferable. The addition amount of a solvent such as water is within a range in which solid and liquid can be homogeneously mixed, and can be appropriately changed according to the specifications of the mixing apparatus and the drying apparatus. Drying is performed to remove a solvent such as water, and is carried out in the range of 80 to 200 ° C. for 1 to 24 hours, and then calcined in air at 300 to 900 ° C., preferably 500 to 700 ° C. Close mixed oxides can be prepared.

  Further, by adding an organic acid such as acetic acid, citric acid, maleic acid, malic acid, and succinic acid to the manganese compound solution, a manganese-cerium homogeneous mixed oxide having a higher activity and a fine structure can be obtained. it can. The addition amount of the organic acid is preferably 0.1 to 2 mol, preferably 0.3 to 1.5 mol, more preferably 0.5 to 1 mol, per 1 mol of the manganese compound. When the addition amount of the organic acid is less than 0.1 mol, the addition effect cannot be obtained, and when it exceeds 2 mol, it is not preferable because it may be a reducing atmosphere during firing and adversely affect the properties of the dense mixed oxide. .

  In the method for producing an air cleaning catalyst of the present invention, the method for adding the catalyst B component is not particularly limited, and examples thereof include the methods (1) to (3). (1) The catalyst A component powder is sprayed or dipped in an aqueous solution of a metal element of the catalyst B component, such as nitrate or sulfate, dried and fired, supported, and then molded and dried and fired. To manufacture. (2) A catalyst A component powder and a catalyst B component metal compound salt solution are kneaded and molded, followed by drying and firing. (3) A catalyst composition containing the catalyst A component is molded, dried and fired, impregnated and supported on a metal compound salt solution of the catalyst B component, and dried and fired. In particular, it is preferable to support the catalyst B component on the surface layer portion of the molded body by the production method (3), whereby the content of the catalyst B component can be reduced. The catalyst may be calcined in air at 300 to 900 ° C., preferably 400 to 600 ° C. The air cleaning catalyst may have a granular shape, a pellet shape, a honeycomb shape, or the like. If necessary, an organic binder such as starch, an inorganic binder such as silica sol or alumina sol, or a ceramic fiber such as glass fiber can be added as a molding aid. The molding aid is preferably added at 15% or less, preferably 10% or less of the catalyst composition. The catalyst C component, which is a refractory inorganic oxide such as aluminum oxide, titanium oxide, zirconium oxide, zeolite, or titanium-based composite oxide, may be added in any step of the production methods (1) to (3). good.

The air cleaning method of the present invention can efficiently remove harmful substances only by bringing the air cleaning catalyst into contact with air containing harmful substances at a low temperature of 50 ° C. or lower. The space velocity of the catalyst is processable in 1,000~1,000,000hr ^-1, preferably it is preferred to treat a range of 10,000~200,000hr ^-1. The catalyst for air purification of the present invention can treat harmful substances and odorous substances such as low concentration ozone, carbon monoxide, VOC, sulfur-based compounds and nitrogen-based compounds present in indoor air. In addition, since the removal rate of the harmful component by the air cleaning catalyst increases as the temperature increases, it can be used at a temperature exceeding 50 ° C.

  The shape of the air cleaning catalyst is not limited to a molded product. For example, it is possible to effectively remove harmful substances contained in the air by coating the surface of a radiating fin such as a radiator of an automobile with the air cleaning catalyst of the present invention containing the catalyst A component and the catalyst B component. it can. At this time, the catalyst composition is wet-pulverized to form an aqueous slurry, which is applied to or sprayed on the heat dissipating fins to adhere to the surface. Since the surface temperature of the radiator fin of an automobile radiator rises to nearly 70 ° C., it is possible to efficiently remove harmful substances in the air using surplus heat. In addition to radiators, those that can use surplus heat can be applied to, for example, car air conditioners, outdoor units for home and commercial air conditioners, and heat radiating fins for personal computers. The indoor and outdoor air can be efficiently treated by covering the portion in contact with the air cleaning catalyst. The average particle diameter of the aqueous slurry is preferably 10 μm or less, and when the average particle diameter is larger than 10 μm, the adhesiveness becomes insufficient, which is not preferable. Aluminum or aluminum alloy is used as the material of the heat dissipating fins, but metal surface treatment may be performed in order to improve adhesion. Moreover, adhesiveness can be improved more by adding an inorganic or organic binder to an aqueous slurry if necessary. Examples of the inorganic binder include silica sol, alumina sol, zirconia sol, cement, and water glass. As the organic binder, various polymers generally used as a paint or a coating agent can be used.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

(Examples 1-4)
Manganese-cerium homogeneous mixed oxide as the catalyst A component was prepared by the following method by the solid-liquid mixing method. Weigh the aqueous solution of powdered cerium carbonate and manganese nitrate and mix well so that the manganese oxide content in the manganese-cerium homogeneous mixed oxide is 30% by mass in terms of MnO _2. It was dried at 150 ° C. overnight, calcined at 500 ° C. for 5 hours, and pulverized with a hammer mill to obtain a manganese-cerium homogeneous mixed oxide MC-1 powder. The obtained manganese-cerium homogeneous mixed oxide was measured for X-ray diffraction by a CuKα ray source, a voltage of 45 KV, a current of 40 mA, a scanning range of 10 to 90 °, and a scanning speed of 0.198 ° / min. A main peak was detected at a position showing a stone-type crystal structure, and no manganese-derived crystal peak was observed. The specific surface area measured by the BET method was 45 m ² / g.

  An appropriate amount of water was added to 94.5 parts by mass of the MC-1 powder obtained above, 5.0 parts by mass of glass fiber and 3.0 parts by mass of starch, mixed with a kneader, and 5 mmΦ long by an extruder. It was molded into a cylindrical pellet having a thickness of 7 mm, dried, and then fired in air at 500 ° C. for 5 hours to obtain a pellet molded body. The pellet molded body thus obtained was sprayed with a nitrate aqueous solution of metal elements shown in Table 1 as the catalyst B component, stirred while heating to 100 ° C. with a rotary evaporator, sufficiently dried, and then heated to 500 in air. C. for 2 hours to obtain finished catalysts of Examples 1 to 4 having the compositions shown in Table 1.

(Examples 5-7)
Examples 1-4 except that the addition amount of manganese nitrate was changed in the preparation of the manganese-cerium homogeneous mixed oxide of Examples 1 to 4 and 1.0 mol of citric acid was added to 1 mol of manganese. Similarly, manganese-cerium homogeneous mixed oxide MC-2 having a manganese oxide content of 50% by mass was obtained. In the obtained MC-2 powder, a main peak was detected at a position showing a fluorite-type crystal structure of cerium dioxide in X-ray diffraction measurement, and a crystal peak derived from manganese was not observed. The specific surface area of the MC-2 powder measured by the BET method was 55 m ² / g. Thereafter, in the same manner as in Examples 1 to 4, finished catalysts of Examples 5 to 7 having the compositions shown in Table 1 were obtained.

(Examples 8 to 9)
First, a Ti—Si composite oxide (Ti / Si molar ratio = 85/15) serving as a catalyst C component was prepared by the following method. After adding 21.3 kg of SNOWTEX-20 (silica sol manufactured by Nissan Chemical Co., Ltd., containing about 20% by weight of SiO ₂ ) to 700 liters of 10% by weight aqueous ammonia, stirring and mixing, a sulfuric acid solution of titanyl sulfate (TiO ₂₎ (125 g / liter, sulfuric acid concentration 550 g / liter) was gradually added dropwise with stirring. The obtained gel was allowed to stand for 3 hours, filtered, washed with water, and then dried at 150 ° C. for 10 hours. This was fired at 500 ° C. and further pulverized using a hammer mill to obtain Ti—Si composite oxide powder TS-1.
The specific surface area of the TS-1 powder is 162 m ² / g, and X-ray diffraction measurement does not show any obvious intrinsic peaks of TiO ₂ or SiO ₂ , and Ti has an amorphous microstructure due to a broad diffraction peak. It was confirmed that a —Si composite oxide was formed. Moreover, as a result of measuring the solid acid amount of TS-1 by n-butylamine titration method using p-dimethylaminoazobenzene as an indicator, the solid acid amount of acid strength of pKa ≦ + 3.3 was 0.48 mmol / g. .

  Next, the manganese-cerium homogeneous mixed oxide MC-2 powder, which is the catalyst A component obtained in Examples 5 to 7, was impregnated with a mixed aqueous solution of silver nitrate and palladium nitrate as the catalyst B component and dried, and then in the air. Calcination was carried out at 500 ° C. for 2 hours to obtain a powder having the catalyst B component supported on the catalyst A component at the ratio shown in Table 1. Hereinafter, a catalyst composition composed of a catalyst A component, a catalyst B component, a catalyst C component and glass fibers with the composition shown in Table 1 is kneaded with a kneader, formed into a pellet shape with an extruder, dried, and 500 ° C. And calcined in air for 5 hours to obtain finished catalysts of Examples 8-9.

(Comparative Example 1)
Commercially available spherical alumina pellets (specific surface area 90 m ² / g, diameter 5 mm) are sprayed with a dinitrodiamine platinum nitrate aqueous solution, heated at 100 ° C. while rotating on a rotary evaporator, dried and taken out at 400 ° C. in air. A platinum catalyst carrying 0.1% by mass of platinum was obtained by firing for 2 hours.

(Comparative Example 2)
An appropriate amount of water was added to 94.5 parts by mass of commercially available cerium oxide (specific surface area of 168 m ² / g), 5.0 parts by mass of glass fiber and 3.0 parts by mass of starch, and mixed with a kneader. Were formed into cylindrical pellets having a diameter of 5 mm and a length of 7 mm, dried, and then fired in air at 500 ° C. for 5 hours to obtain a pellet molded body. The pellet shaped body thus obtained was sprayed with an aqueous solution of palladium nitrate, stirred while being heated to 100 ° C. with a rotary evaporator, sufficiently dried and then fired in air at 500 ° C. for 2 hours, as shown in Table 1. A comparative catalyst of Comparative Example 2 having a composition was obtained.

（一酸化炭素除去試験）
実施例１〜９および比較例１〜２で得られた各触媒を用いて、以下の手順で一酸化炭素の酸化分解試験を実施した。
ペレット触媒７５ｃｃを内径２５ｍｍのガラス管の充填し、一酸化炭素が１，０００ｐｐｍ、水分２．５％を含有する空気を空間速度１０，０００ｈｒ^−１で通ガスし出口の二酸化炭素濃度を測定して二酸化炭素転化率により一酸化炭素酸化性能をもとめた。反応温度２０および５０℃の各温度で測定した性能試験結果を表１に示した。

(Carbon monoxide removal test)
Using each catalyst obtained in Examples 1 to 9 and Comparative Examples 1 and 2, an oxidative decomposition test of carbon monoxide was performed according to the following procedure.
A glass tube with an inner diameter of 25 mm was filled with 75 cc of the pellet catalyst, air containing 1,000 ppm of carbon monoxide and 2.5% of water was passed at a space velocity of 10,000 hr ⁻¹ , and the carbon dioxide concentration at the outlet was measured. The carbon monoxide oxidation performance was determined by the carbon dioxide conversion rate. The performance test results measured at each reaction temperature of 20 and 50 ° C. are shown in Table 1.

(Various hazardous substance removal test)
Using each of the catalysts obtained in Examples 5 to 8 and Comparative Examples 1 and 2, a carbon monoxide, ozone and formaldehyde removal performance test was performed according to the following procedure. The reaction temperature was 50 ° C., the space velocity was 10,000 hr ^{−1, and the} inlet gas concentration was 20 ppm of carbon monoxide, 10 ppm of ozone, 20 ppm of formaldehyde, and 2.5% of moisture, and the treatment efficiency for each component was determined. The performance test results are shown in Table 2.

以上の結果より本発明の空気清浄化用触媒は、比較触媒と比較して低温で各種有害物質を処理することができる。

From the above results, the air cleaning catalyst of the present invention can treat various harmful substances at a lower temperature than the comparative catalyst.

  In the present invention, the air cleaning catalyst can treat harmful substances such as carbon monoxide and formaldehyde present in the air at a low temperature of 50 ° C. or lower, and can be used for air cleaning indoors and outdoors.

Claims (7)

A catalyst for air purification containing at least one metal element selected from manganese-cerium homogeneous mixed oxide as catalyst A component and elements belonging to groups 8 to 11 of the periodic table as catalyst B component, The manganese-cerium homogeneous mixed oxide contains 10 to 60% by mass of manganese in terms of manganese dioxide, and is identified as having a cerium dioxide fluorite structure by powder X-ray diffraction measurement. An air purification catalyst characterized by the above. 30 to 99.95% by mass of a mixed manganese-cerium oxide which is a catalyst A component, and 0.05 to 20 at least one metal element selected from palladium, platinum, silver and gold as a catalyst B component The air cleaning catalyst according to claim 1, wherein the catalyst is contained in mass%. The catalyst C component further contains at least one refractory inorganic oxide selected from the group consisting of aluminum oxide, titanium oxide, zirconium oxide, zeolite, and titanium-based composite oxide. Air cleaning catalyst. 2. A process comprising mixing a cerium oxide or a precursor of cerium oxide and a manganese compound solution, followed by drying and firing in air at 300 to 900 ° C. to obtain a manganese-cerium homogeneous mixed oxide. The manufacturing method of the catalyst for air purification of ~ 3. The method for producing an air cleaning catalyst according to claim 4, wherein 0.1 to 2 mol of an organic acid is added to the manganese compound solution with respect to 1 mol of the manganese compound in the production method of claim 4. An air cleaning method for removing harmful substances in the air using the air cleaning catalyst according to claim 1. The air cleaning method according to claim 6, wherein harmful substances in the air in which the air cleaning catalyst is coated on the surface of the radiation fin are removed.