JPH0194945A - Catalyst of carrying superfine gold particles fixed on metal oxide and manufacture therefor - Google Patents

Abstract

PURPOSE:To enhance combustion and oxidation reactivity at low temperatures, by conducting carrying operation and aging operation of gold under the condition of pH value in the range of 7.5-9.5 to fix superfine particles of gold to metal oxide, the principal components of which being iron oxides, causing said metal oxides to be carried by carriers. CONSTITUTION:Carrying operation and/or aging operation of gold is conducted under the condition of pH value in the range of 7.5-9.5 to fix superfine particles of gold to metal oxides (MeO), the principal components of which being iron oxides. Said fixed matters are applied to the surfaces of catalyst carriers to be carried thereby, whereby catalyst wherein superfine particles of gold are fixed to metal oxide to be carried thereby is obtained. Material for carriers for catalyst are preferably, as principal components therefor, ceramics such as alumina, silica, silica-alumina, zeolite, titania etc. Content of gold contained in catalyst is preferably 0.1-20.0g/l of catalyst and the quantity of MeO carried is preferably about 20wt.% or more per total weight of MeO and carriers.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a catalyst body comprising gold and iron oxide as main components and supported on a catalyst carrier, which is particularly excellent in combustion or oxidation reactions at low temperatures. The present invention relates to a gold thread catalyst suitable for active catalytic combustion reactions and a method for producing the same.

[Conventional technology]

Catalysts for catalytic combustion are used to purify exhaust gas from various heaters, kitchen heaters, kerosene stoves, etc., burn and remove carbon monoxide and hydrocarbons from automobile exhaust gas, eliminate pollution and deodorize factory exhaust gas,
It is widely used today in many applications such as air purifying filters for air conditioners and gas masks, and its operating temperature ranges widely from room temperature or lower to high temperatures exceeding 1000°C. There are therefore a wide variety of catalysts used in catalytic combustion, but very few of them are currently in practical use as oxidation catalysts that can be used at room temperature. It can be said that the hopcalite catalyst, which is the main component, is almost the only one. However, this hopcalite catalyst has a fatal defect in that it rapidly loses its activity, especially its low-temperature activity, due to moisture.In particular, in order to expand the range of application of combustion catalysts to room temperature or below room temperature, it is necessary to use this hopcalite catalyst. It has been desired for a long time to develop a low-temperature active catalyst free from such defects, and desirably also excellent in heat resistance. Under such circumstances, the present inventors filed Japanese Patent Application No. 59-95185 (Japanese Unexamined Patent Publication No. 60-2
No. 38148), we announced a new low-temperature active combustion catalyst, that is, a gold thread oxide catalyst, which could meet the above-mentioned needs. They have announced a homogeneous precipitation method in which a carrier is immersed in an aqueous solution containing water-soluble salts of gold and other metals as components and urea and/or acetamide to precipitate catalyst components on the carrier.

[Problem that the invention seeks to solve]

In the case of a gold-containing catalyst using a catalyst carrier, especially a carrier made of an inorganic heat-resistant material, depending on the method of manufacturing or supporting the catalyst, the adhesion between the active ingredient and the carrier may be poor and the active ingredient may easily desorb, resulting in high activity. There are disadvantages such as the inability to obtain a catalyst, and the high cost of the catalyst due to the high cost of raw materials and equipment, and many problems remain in its industrial use. For example, in the case of the homogeneous precipitation method disclosed in Japanese Patent Application No. 60-192775, the activity is high and the catalyst components are firmly supported on the carrier, but it cannot necessarily be said that it is a method suitable for mass production. Finding a better method for producing highly active catalysts at low cost through simpler operations is an extremely important issue in increasing the practical value of this type of gold-containing catalyst, and the present invention is the problem we are trying to solve.

[Means for solving problems]

The inventors of the present invention have conducted intensive studies to find a simple and efficient manufacturing method that can inexpensively mass-produce catalysts with particularly excellent low-temperature combustion activity. By adopting a special manufacturing method, the catalyst carrier It has been found that even when supported on a gold-metal oxide catalyst, a highly active catalyst can be obtained which is comparable to that of a gold-metal oxide catalyst that does not use a carrier, and the cost of the catalyst can thereby be significantly reduced.

That is, the present invention allows the gold supporting operation and/or ripening operation to be performed at 7.5
Ultrafine gold particle-immobilized metal prepared by immobilizing ultrafine gold particles on a metal oxide (MeO) containing iron oxide as a main component and supporting it on a catalyst carrier in a pH range of ~9.5. It is an oxide-supported catalyst.

Regarding the gold-iron oxide system, which is expected to have the most excellent catalytic performance, the present inventors produced the catalyst body of the present invention, which supports gold in the form of ultrafine particles and firmly fixed to iron oxide. The conditions were studied in detail and the method for producing the catalyst of the present invention was completed.

That is, the present invention provides a catalyst comprising an oxide (MeO) of at least one metal from the group consisting of chromium, manganese, iron, cobalt, nickel, and copper, and gold and/or an oxide of gold supported on a catalyst carrier. In producing the medium, a catalyst carrier carrying about 10% by weight or more of MeO is placed in an alkaline solution adjusted to pH 7.5 or higher, and the pH of the solution is adjusted to about 7.5.
A gold superconductor characterized by depositing a gold compound onto the carrier by adding a gold compound solution such as chloroauric acid while maintaining the molecular weight within the range of 5 to 9.5 to obtain a catalyst precursor, and calcining the catalyst precursor. This is a method for producing a fine particle-immobilized metal oxide supported catalyst.

The temperature of the solution is preferably 40 to 90°C.

The method of the present invention makes it possible to inexpensively and mass-produce highly active, especially catalyst bodies suitable for catalytic combustion, which have excellent low-temperature activity, with good reproducibility.

As the catalyst carrier used in the production of the catalyst of the present invention, all carriers can be used, including carriers mainly made of ceramics such as alumina, silica, silica-alumina, zeolite, and titania, and carbon-based carriers such as activated carbon. But metal,
When using a carrier made of a material with poor water absorption such as cordierite, it is desirable to coat the carrier with γ-alumina to facilitate the support of the catalyst component. The shape of the carrier is also
powder, spherical, granular, honeycomb, foam, fibrous,
All shapes currently commonly used as catalyst carriers, such as cloth, plate, and ring shapes, can be used.

The catalyst manufacturing method of the present invention requires a metal oxide MeO supported on a catalyst carrier, and methods for supporting MeO include powder temperature method, kneading method, impregnation method, coating method, spraying method, All methods commonly used for supported catalysts can be used, such as precipitation methods. The amount of MeO supported is desirably about 10% by weight or more, particularly about 20% by weight or more.

Chloroauric acid is generally used as the gold starting material for the preparation of the catalyst of the present invention. When the gold content in the catalyst is relatively low, the activity increases as the gold content increases, but beyond a certain range, the activity decreases. However, a suitable gold content is, for example, 0.1 to 5 g per catalyst 11 for beaded catalysts, preferably 2 to 4 g;
In the case of honeycomb-shaped catalysts, the amount varies considerably depending on the shape, ranging from 7 to 10 g, so it is necessary to determine the content in advance that is suitable for each shape. Therefore, although it cannot be said that there is a suitable gold content, it is generally in the range of 0.1 to Log/f catalyst based on the above facts.

In the catalyst production method of the present invention, it is necessary to support gold on the carrier by a precipitation operation in an alkaline solution maintained at a pH of 7.5 or higher.

Supporting a gold compound, such as a residual hydroxide, in an alkaline solution is effective in producing ultrafine gold particles that characterize a highly active catalyst, and is an essential requirement for the present invention. However, if the pH exceeds 10.5, gold will not be deposited on the carrier, but will form complex ions with hydroxyl groups and dissolve in the liquid phase, resulting in a decrease in activity, which is undesirable. 9.5, preferably about 8.5 to 9.0.

In the production method of the present invention, all alkalis such as alkali carbonate, alkali hydroxide, and ammonia can be used as precipitants for forming gold compounds such as residual hydroxide precipitates.Among them, soda carbonate has a large particle size distribution width. This method is particularly desirable because narrow ultrafine particles of gold can be most stably immobilized and a highly active catalyst can be obtained.

The method of adding these alkalis and chloroauric acid to the solution containing the carrier is such that the pH of the solution containing the carrier is 7.5 to 7.5.
Any method may be used as long as it is kept within the range of 9.5. That is, any method can be used, such as adding the entire amount of alkali and then adding chloroauric acid, adding alkaline earth auric acid at the same time, or adding alkali and gold alternately. Sufficient stirring is particularly effective for producing a highly active catalyst during precipitation formation when both alkali and chloroauric acid solutions are added and during ripening after addition of both solutions. During this time, the temperature of the liquid may be room temperature, but it is 30℃ or higher1.
It is desirable to maintain the temperature at 00°C or lower, preferably between 40°C and 90°C. Since aging affects catalyst activity, it is desirable to carry out aging for at least 1 hour.
In some cases, it may be shorter.

The catalyst precursor, in which the metal oxide MeO is supported on a carrier and a precipitate containing gold is further deposited, undergoes finishing operations such as washing, drying, and calcination that are used in normal catalyst production to become a finished catalyst. , drying, and other operations may be omitted depending on the case.

Calcination can be carried out at a temperature in the range of about 200 to 1000°C, but in the production of the catalyst of the present invention, the activity may sometimes decrease if the calcination temperature exceeds 600°C.
A range of 00°C is desirable.

(Example) The invention will now be explained in more detail by way of example.

2 mm diameter γ-alumina beads with a specific surface area of 326 m2/g impregnated with ferric nitrate were fired at 400°C for 4 hours to obtain Fe, 0. Alumina beads carrying the were obtained. The supported amount of Fe2O3 was 21.8% by weight. 600c of this FezO3-supported alumina beads
The pH was adjusted to 8.0 using a 1 molar aqueous solution of sodium carbonate. A 0.01 molar aqueous solution containing 15 g of chloroauric acid was added to this solution, a precipitate was deposited on the beads, and the beads were aged for about 1 hour. During the precipitation and ripening, the temperature of the solution was maintained between 70 and 80° C., and sufficient stirring was performed. Further, an aqueous sodium carbonate solution was added at appropriate times to adjust pi to between 7.7 and 8.5, and as a result, the pH of this solution after aging was 8.0.

The catalyst precursor thus produced (Fe, 0 on γ-alumina)
3 and a precipitate containing gold) were washed with running water for about 1 hour, dried at a temperature of 120°C for 12 hours, and then calcined at a temperature of 400°C for 4 hours.
I got it. The specific surface area of this example catalyst 1 is 226 m"/g
Met. The gold content was 0.5% by weight, which corresponded to 3.8 g/11 catalyst.

Actual stopper weight Σl Same adjustment method as in Example 1 except that the gold content was changed to 1% by weight (7.3g/j2 catalyst) and 0.3% by weight (2.3g#!catalyst), respectively. Two types of catalysts were prepared using Example Catalysts 2 and 3, respectively. The pH of the liquid after ripening is 7.
．． 9 and 8.6.

A catalyst was prepared as Example Catalyst 4 by the same method as in Example 1, except that the amount of Jitsei Charcoal Earth Fe2O+ supported on T-alumina beads was changed to 12% by weight. The pH of the liquid after aging is 8.4
Met.

Sazuki Jb- Example catalysts 1, 2, 3. A CO oxidation activity test was conducted using the following test conditions:

Trial 11 [Distance Gas used: Wet CO gas made by bubbling air containing 1.3 to 1.4 volume% CO into water at 30°C. Temperature: Room temperature supply gas space velocity: 20,000 hours-1 The test results are shown in Table 1. .

According to the test results, the catalyst of the present invention prepared using γ-alumina beads (1) sufficiently oxidizes CO even at room temperature, and the activity does not decrease due to moisture.

(2) The larger the amount of Fe z Os supported, the better.
It is particularly desirable to set the Au content to about 20% by weight or more.
5% by weight (approximately 2-4 g/l catalyst) is preferred.

5 and 12 Example Catalyst 5 was obtained by firing Example Catalyst 1 at a temperature of 600° C. for 2 hours. Tests similar to those in Use Example 1 were conducted on this catalyst. The test results are shown in Table 1.

Those calcined at a temperature of 600'C showed somewhat lower activity than those calcined at 400C.

6 7 and 3 Two types of catalysts were prepared in the same manner as in Example 1, using an alumina-silica honeycomb carrier (200 cells/1 square inch) instead of γ-alumina beads. , Example catalysts 6 and 7 were obtained.

c under the same conditions as in Use Example 1 using these catalysts.

A combustion activity test was conducted. The catalyst composition and test results are
Shown in the table.

According to the test results, F e per unit volume of carrier light is 0.
The amount of 3 supported was about the same as in the case of alumina beads, which was sufficient. Since honeycomb is significantly lighter than beads, the amount of Fe, 03 supported is much higher than that of beads when expressed in weight percent. On the other hand, the gold content, in terms of weight per unit volume, is required to be at a higher level than in the case of beads. It is considered that the appropriate amount is 4 to 8 g/l or more, which is more than double the 2 to 4 g/l catalyst in the case of beads.

(Effect of the invention) Thus, according to the present invention, it has excellent activity even when absorbing moisture,
A catalyst with excellent heat resistance can be obtained.

Of course, various changes and modifications may be made without departing from the broader spirit and scope of the invention.

Claims (1)

[Claims] 1. The gold supporting operation and/or the aging operation are carried out within the pH range of 7.5 to 9.5, and the ultrafine gold particles are made of metal oxide (MeO) whose main component is iron oxide. A metal oxide-supported catalyst body with ultrafine gold particles immobilized on a catalyst carrier. 2. Catalyst carrier is alumina, silica, silica-alumina,
The catalyst body according to claim 1, which is a carrier mainly made of ceramics such as zeolite or titania, or a carbon-based carrier such as activated carbon. 3. The amount of gold contained in the catalyst is approximately 0.1 to 20.0 g/
3. The catalyst body according to claim 1 or 2, which is a l catalyst. 4. The catalyst body according to claim 1, 2 or 3, wherein the supported amount of MeO is about 20% by weight or more based on the total weight of MeO and the carrier. 5. The catalyst body according to claim 1, 2, 3 or 4, wherein MeO is iron oxide mainly consisting of Fe_2O_3. 6. Claims 1, 2, 3, 4 or 5 obtained by firing the catalyst precursor in air at a temperature in the range of 200 to 1000°C
Catalyst body as described. 7. Oxide of at least one metal Me from the group consisting of chromium, manganese, iron, cobalt, nickel and copper (Me
O) and gold and/or gold oxide supported on a catalyst carrier, an alkaline solution in which the catalyst carrier carrying about 10% by weight or more of MeO is adjusted to pH 7.5 or more. and adjust the pH of the solution to about 7.5-9.
Ultrafine gold particle immobilized metal, characterized in that a gold compound solution such as chloroauric acid is added to the carrier while maintaining the concentration within the range of 5 to obtain a catalyst precursor, which is then calcined. A method for producing an oxide-supported catalyst. 8. The catalyst carrier is alumina, silica, silica alumina,
8. The manufacturing method according to claim 7, wherein the carrier is mainly a ceramic carrier such as zeolite or titania, or a carbon-based carrier such as activated carbon. 9. The amount of gold contained in the catalyst is about 0.1 to 1 liter of catalyst.
The manufacturing method according to claim 7 or 8, wherein the amount is 20.0 g. 10. The manufacturing method according to claim 7, 8 or 9, wherein the addition of an alkali component and the addition of a gold compound are carried out alternately during the operation of supporting gold on the carrier. 11. The manufacturing method according to claim 7, 8, 9 or 10, wherein the temperature of the alkaline solution containing the carrier is in the range of about 60 to 80°C during the gold supporting operation and/or ripening. 12. The manufacturing method according to claim 7, wherein the supported amount of MeO is about 20% by weight or more based on the total weight of MeO and the carrier. 13. The manufacturing method according to claim 7, 8, 9, 10, 11 or 12, wherein MeO mainly consists of Fe_2O_3. 14. Claims 7, 8, 9, 10, wherein the catalyst precursor is calcined in air at a temperature in the range of 200 to 1000°C.
The manufacturing method according to 11, 12 or 13.