JPH05212294A - Catalytic body and its production - Google Patents

Abstract

PURPOSE:To increase volume resistivity, to reduce variance and to appropriately use the catalytic body for sterilization and deodorization by forming the catalytic body with a carrier and a metallic component having catalytic activity and dispersed in the carrier and specifying the volume resistivity. CONSTITUTION:The catalytic body is formed with a carrier and a metallic component having catalytic activity and dispersed in the carrier, and the volume resistivity is controlled to >=1X10<6>OMEGAcm. Iron, manganese, nickel, cobalt, chromium and copper are exemplified as the metallic component. Silica, alumina, titania and zirconia are exemplified as the component of the carrier. Although the catalytic body is obtained by highly and uniformly dispersing the metallic component in the carrier, high-degree uniform dispersion is attained by coprecipitation or coprecipitation and kneading. Since the metallic component is uniformly dispersed in the entire catalytic body, the variance of volume resistivity is reduced, and a high voltage can be impressed on the catalytic body.

Description

Detailed Description of the Invention

[0001]

The present invention has a volume resistivity of 1 × 10 ⁶
The present invention relates to a catalyst body having an Ωcm or more and suitable for sterilization and deodorization.

[0002]

2. Description of the Related Art Conventionally, as a catalyst body in which a metal component having a catalytic activity is carried on a carrier, the carrier is molded and sintered from a raw material powder, and then impregnated with an aqueous metal salt solution having a catalytic activity. , Which are manufactured by firing or drying again are known.

[0003]

As a method of utilizing such a catalyst body, it is known to dispose a plurality of catalyst bodies facing each other and apply a high voltage to sterilize and deodorize them. .. However, since the catalyst body obtained by the above-mentioned impregnation method has a non-uniform distribution of catalytically active metal on the surface of the carrier, even if it is produced under the same conditions, the volume resistivity varies by three digits or more, and the moisture content in the air When adsorbed, the resistance value fluctuates considerably and the insulation stability is lacking. Therefore, high voltage cannot be applied, and required sterilization and deodorizing ability cannot be obtained. Therefore, an object of the present invention is to provide a catalyst body which is suitable for sterilization and deodorization because it has a sufficiently high volume resistivity and a small variation, and a method for producing the same.

[0004]

According to the present invention, there is provided a catalyst body comprising a carrier and a component having a catalytic activity dispersed in the carrier and having a volume resistivity of 1 × 10 ⁶ Ωcm or more. It Examples of the catalytically active metal component include iron, manganese, nickel, cobalt, chromium and copper. Examples of the component constituting the carrier include silica, alumina, titania, zirconia and the like. This catalyst body is obtained as a result of extremely highly uniformly dispersing the catalytically active metal component in the carrier. Such a highly uniform dispersion can be obtained by coprecipitation method or by using a kneading method in combination therewith. To be achieved.

That is, the present invention is, firstly, as a method for producing the above-mentioned catalyst body, (A) a metal compound having catalytic activity and (B) a metal compound constituting a carrier are dissolved in an aqueous medium or A step of adding a precipitating agent to the dispersed aqueous solution or dispersion to coprecipitate the metal components of (A) and (B);
There is provided a production method including a step of firing the obtained coprecipitate to form a composite oxide, and a step of firing the composite oxide after molding.

Examples of the metal compound (A) used as a raw material include water-soluble nitrates, sulfates, chlorides and oxalates. Examples of the metal (B) include silicon, aluminum, zirconium, titanium, and the like, and compounds of these metals are preferably selected from oxides, hydroxides, chlorides, sulfates, and the like. Specifically, it can be used in the state of colloidal silica, colloidal aluminum, colloidal zirconium, aluminum hydroxide, colloidal aqueous solution of zirconium hydroxide, titanium tetrachloride, titanium sulfate or titanyl sulfate.

Examples of the precipitant include ammonia, sodium hydroxide, ammonium carbonate and the like, and ammonia water is preferable. The precipitating agent may be used in an appropriate amount and in an appropriate amount so that the required pH at which the metal compound used causes coprecipitation can be achieved. The coprecipitate may be generally calcined at a temperature of about 200 to 800 ° C. in an oxidizing atmosphere such as oxygen or air. The firing time is usually about 0.5 to 2 hours. The above production method is suitable when most components form a coprecipitate in the coprecipitation operation.

Further, the present invention provides (A) a metal compound having catalytic activity and
(B) A precipitant was added to an aqueous solution or dispersion prepared by dissolving or dispersing a part of the metal component compound (however, at least two compounds) constituting the carrier in an aqueous medium, and then dissolved or dispersed. A step of coprecipitating a metal component, a step of firing the resulting coprecipitate to form a composite oxide, the composite oxide, the aqueous solution of the compound of (A) and (B) or And a step of kneading with the remaining metal compound that has not been used in the dispersion and baking the obtained kneaded product after molding.

In this manufacturing method, a precipitate is formed by a coprecipitation method.
It is suitable for cases where it is difficult to obtain a coprecipitate of all components, such as when the pH value varies greatly or the coprecipitate dissolves due to a change in pH. Therefore, the metal compound used in the coprecipitation step is, for example, TiCl ₄ , SiO ₂ , ZrO ₂ , Al ₂ O ₃ , and the metal compound used in the next kneading step is, for example, Mn (NO ₃ ) ₂ , NiNO ₃
Is suitable.

The above kneading step is preferably carried out by using a kneading machine capable of giving a high shear stress (preferably using a continuous kneader) to the material to be kneaded. Other conditions are the same as those described in the first manufacturing method described above. According to these production methods, in the coprecipitation method, the carrier component and the catalytically active metal component are mixed in advance in an aqueous solution state to form a coprecipitate, so that the respective components show a uniform distribution without bias.

In the method using the above-mentioned kneading, the catalytically active metal component is added to the carrier component afterwards, but since a kneader capable of giving a high shearing force such as a continuous kneader is used, the catalytically active metal component is coprecipitated. Similar to the method, it shows a relatively uniform distribution. Since the catalytically active metal component mainly exhibits conductivity, the volume resistivity of the catalyst is considered to be greatly influenced by the distribution state of this component.

In the production method of the present invention, since the catalytically active metal component is uniformly distributed over the entire catalyst body, even if the volume resistivity is measured for a plurality of samples, the variation in the value becomes extremely small. As a result, a high voltage can be applied to the catalyst body, and high deodorizing ability and sterilizing ability can be achieved. The structure and shape of the catalyst body of the present invention are not particularly limited, and can be formed into various structures such as a honeycomb shape, a corrugated shape, a three-dimensional knitted shape, and a granular shape. In order to use the catalyst body for deodorization and / or sterilization, an electrode is attached to a part thereof.

[0013]

【Example】

Example 1 Ferric nitrate, colloidal silica and cobalt chloride were added to F
e (NO ₃ ) ・ 9H ₂ O 0.431 mol (174.1 g), SiO ₂ 0.43
1 mol (123.8 g) and CoCl ₂ · 6H ₂ O 0.431 mol (10
1 kg of an aqueous solution containing 2.5 g) was prepared. With this, the concentration is about 10
% Ammonia water was mixed while controlling the pH of the solution to be maintained at 7 to 9 to coprecipitate the metal component. After stirring the obtained suspension for 1 hour, solid-liquid separation was performed with a high-speed centrifuge. The solid obtained was again dispersed in water to dissolve the soluble component and then subjected to centrifugation to repeat the operation several times to wash the coprecipitate. The coprecipitate thus obtained was then calcined at 500 ° C. for 1 hour to produce Fe ₂ O ₃ --SiO _2.
A composite oxide powder consisting of _2- CoO was obtained. This powder had a specific surface area of 230 m ² / g, and it was found from an electron diffraction image that it had a very fine crystal structure.

When the characteristics of the obtained composite powder were measured, the following results were obtained. However, only the volume resistivity was press-molded into a cylindrical shape having a diameter of 20 mm and a length of 14 mm, baked at 500 ° C., coated with dotite on both end faces, dried, and measured. 1) Volume resistivity (500 V, 60 seconds applied): 3.5 × 10 ⁶
Ωcm 2) Saturated adsorption amount of triethylamine: 32.9 mg / g 3) Ozone decomposing ability: The time during which 1 g of the composite powder can decompose 100% of ozone while ozone of 3 mg / hr was generated was measured. 5
Time was measured. A powder of a ternary composite oxide having a molar ratio of 1: 1: 1 was produced in the same manner as above except that the raw materials were changed, and the characteristics were measured in the same manner. The results shown in Table 1 were obtained. ..

[0015]

[Table 1]

Example 2 (1) An aqueous solution of 65.5 wt% TiCl ₄ (4 mol as Ti content) (11
58g) and 20% by weight aqueous collodal silica solution (Si content is 1
Mol) (300 g) was dissolved in water to prepare 1458 g of an aqueous solution. Ammonia water having a concentration of about 10% was added to this aqueous solution so that the pH after the addition was 7 to 9 to obtain a titanium-silica coprecipitate. The coprecipitate was subjected to solid-liquid separation by centrifugation, and the obtained solid was calcined at 600 ° C for 1 hour to obtain 380 g of a titania-silica composite oxide.

(2) Next, 380 g of this titania-silica composite oxide and manganese nitrate Mn (NO ₃ ) ₂ 1 mol (287 g)
After kneading and were preliminarily kneaded, they were sufficiently kneaded with a continuous kneader. The resulting kneaded product is dried, pulverized, granulated, and further press-molded into a cylindrical shape having an outer diameter of 20 mm and a length of 14 mm, and
Sintered at ° C. In this way, the dimension after sintering is 17 mm outer diameter,
A catalyst body consisting of a sintered body having a length of 12 mm was obtained. Silver-based conductive paint (trade name: Doudite; manufactured by Fujikura Kasei Co., Ltd.) was applied to both upper and lower end surfaces of the catalyst body thus obtained, and dried to form electrodes. A direct current voltage of 500 V was applied thereto, and the resistance value after 1 minute was measured to be 13 MΩ, which was 24.5 × 10 ⁶ Ωcm in terms of volume resistivity.

Example 3 As starting materials, TiCl ₄ , colloidal silica and MnCl ₂
Was used in the same manner as in Example 1 except that Ti: Si: Mn was used in a molar ratio of 4: 1: 1 to produce a ternary composite oxide by the coprecipitation method only. Five catalyst bodies with electrodes were prepared in the same manner as in Example 2, and the volume resistivity was determined for each.
I checked the variations. The obtained results are shown in FIG.

Example 4 A complex oxide was prepared by combining the coprecipitation method and the kneading method in the same manner as in Example 2 except that Ti: Si: Mn was used in a molar ratio of 4: 1: 1. Obtained. Five catalyst bodies with electrodes were produced from this composite oxide in the same manner as in Example 2, and the volume resistivity was determined for each, and the variation was examined. The obtained results are shown in FIG.

Comparative Example A titania-silica composite oxide was produced in the same manner as in Example 2 (1). This was molded and calcined in the same manner as in Example 2, then immersed in a 62% concentration manganese nitrate solution for impregnation, dried, and further calcined at 500 ° C. to obtain a catalyst body. An electrode was attached. In the same manner, five electrode-attached catalyst bodies were produced, the volume resistivity was determined for each, and the variation was examined. The results are shown in Figure 1.

Example 5 A Ti-Si-Mn-based catalyst powder obtained by the coprecipitation method of Example 3, the kneading method of Example 4, and the impregnation method according to the comparative example was used.
mm, 2 mm thick disk-shaped, and then surface analysis (Computer Micro Analysis: CMA) of the composition using a computer,
The bias of the composition distribution was investigated for each component of Ti, Si, and Mn. The bias of composition distribution was converted into CV (coefficient of variation) for evaluation. CV
The smaller the value is, the less the composition bias is. The results are shown in Table 2. The catalysts prepared by the kneading method and the coprecipitation method have smaller CV values than those prepared by the impregnation method for any of the elements, indicating that the composition is less biased. Considering together with the result of FIG. 1, it seems that the deviation of the distribution of Mn is deeply related to the variation of the volume resistivity.

[0022]

[Table 2]

[0023]

EFFECTS OF THE INVENTION The catalyst of the present invention has a sufficiently high volume resistivity and a small variation, and is therefore suitable for sterilization and deodorization.

[Brief description of drawings]

FIG. 1 shows the volume resistivity and its variation of the catalyst bodies obtained in Examples 3 and 4 and Comparative Example.

Claims (3)

[Claims] 1. A carrier and a catalytically active metal component dispersed in the carrier, and has a volume resistivity of 1 × 10 ⁶ Ω.
A catalyst body that is at least cm. 2. A metal compound having (A) catalytic activity, and
(B) a step of coprecipitating the metal components of (A) and (B) by adding a precipitant to an aqueous solution or dispersion obtained by dissolving or dispersing a metal compound constituting the carrier in an aqueous medium, The method for producing a catalyst body according to claim 1, comprising a step of calcining the obtained coprecipitate to produce a composite oxide, and a step of calcining the composite oxide after molding. 3. A solution of (A) a compound of a metal component having catalytic activity and (B) a part of a metal compound constituting the carrier (however, at least two compounds) are dissolved or dispersed in an aqueous medium. A step of adding a precipitating agent to an aqueous solution or a dispersion to coprecipitate a metal component dissolved or dispersed therein; a step of firing the obtained coprecipitate to form a composite oxide; A step of kneading (A) and (B) compounds with the remaining metal compound that has not been used in the aqueous solution or dispersion, and firing the resulting kneaded product. A method for producing the catalyst body according to 1.