JPH02169029A - Method for manufacturing combustion catalyst - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing a catalyst for combustion of various fuels.

More specifically, the present invention relates to a method for producing a combustion catalyst used to combust gaseous fuels such as methane and propane, or vaporized liquid fuels such as liquefied natural gas, liquefied petroleum gas, and alcohol.

(Prior Art and its Problems) A noble metal catalyst made by supporting a noble metal on an inorganic fibrous carrier is widely used as a combustion catalyst (for example, Japanese Patent Laid-Open No. 63-65951).

Inorganic fibrous laminates or low-density mat-like carriers are used as catalyst carriers in catalytic combustors that burn the fuels flamelessly and at low temperatures on catalysts to obtain thermal radiation rich in far-infrared rays. The materials used include alumina, alumina-silica, and alumina-silica, which have good far-infrared radiation properties.
Fibers whose main component is activated alumina, such as zirconia or alumina-titania, are often used.

In order to produce a catalyst using the carrier, the inorganic fibrous carrier is impregnated with, for example, a dinitrodiammine complex solution of the noble metal, dried and smoked, and fired in the atmosphere. However, in this loading method, (1) the noble metal is not loaded uniformly due to unevenness of the liquid during drying, resulting in unevenness and diffusion into parts of the fuel supplied from the fuel supply path where the precious metal particles are densely distributed; Although some substances are completely combusted, those that are dispersed in areas with a sparse distribution become incompletely combusted, resulting in a decrease in catalyst efficiency and the generation of incompletely combusted oxides such as unburned hydrocarbons, aldehydes, and carbon oxides. 2) When drying, the support becomes flattened, the porosity decreases, and the surface area decreases, which worsens gas diffusion during fuel combustion. (3) When fired in the atmosphere, noble metals aggregate and activity decreases. (4) The dinitrodiammine complex liquid has the drawback that unless it is calcined at a high temperature of about 800° C., it will not be completely decomposed and nitrate groups will remain and the catalyst performance will deteriorate.

In order to solve the drawbacks of this method, a method has also been proposed in which the noble metal ions in the nitric acid solution of the dinitrodiammine noble metal complex are ion-exchanged with a support such as alumina (U.
(Japanese Patent Application Laid-open No. 63-65951), some chemical species are adsorbed to the ion exchange resin and some are not, and complex chemical species are likely to be generated in the solution during treatment, and only chemical species that undergo ion exchange are It is very difficult to remove it from the solution.

(Object of the Invention) The present invention has been made to solve each of the above-mentioned problems, and consists of a high-density polymer containing substantially no impurities such as nitrate radicals, in which precious metal particles as a catalyst component are uniformly supported on a carrier. An object of the present invention is to provide a method for relatively easily manufacturing a combustion catalyst having catalytic efficiency.

(Means for Solving the Problems) The present invention provides a method for producing a combustion catalyst comprising a noble metal catalyst component supported on an inorganic fibrous carrier, in which a dinitrodiammine complex of the noble metal is added with an aldehyde and a surfactant. The method for producing a combustion catalyst is characterized in that the carrier is immersed in a nitric acid solution, the noble metal complex is reduced, and the corresponding noble metal is precipitated and supported on the carrier; This method performs reduction in a hydrogen stream.

The present invention will be explained in detail below.

In the present invention, instead of the conventional calcination of the dinitrodiammine complex solution in the atmosphere, an aldehyde is added to the solution, thereby reducing the noble metal ion in the noble metal complex to the corresponding noble metal atom. It is characterized in that it is supported on a carrier.

The inorganic fibrous carrier used in the present invention is not particularly limited,
Alumina, silica, zirconia, titania, alumina
Conventionally used fibers of inorganic oxides such as silica, alumina-zirconia, and zirconia-silica can be used without limitation. The noble metal catalyst component includes platinum group metals such as platinum, palladium, ruthenium, and osmium, and in addition to these, a small amount of a promoter such as nickel may be contained. Two nitro groups and two ammonium groups are coordinated to the noble metal catalyst component by a conventional method to prepare a dinitrodiammine complex in nitric acid solution.

The aldehyde used in the present invention is not particularly limited as long as it can reduce the noble metal in the noble metal dinitrodiammine complex to the corresponding noble metal element and support it on the inorganic fibrous carrier, but formaldehyde Preference is given to using lower aldehydes such as , acetaldehyde and probionaldehyde. In addition, the surfactant has the function of weakening the surface tension of the solution and suppressing a decrease in the porosity of the carrier, and includes quaternary ammonium salt compounds such as alkyl)IJ methylammonium chloride and alkyldimethylpentylammonium chloride, and alkylaminoethanol. Cationic surfactants such as cationic surfactants have the best functions, and other surfactants such as anionic surfactants, amphoteric surfactants, and nonionic surfactants have almost no such functions. Therefore, it is undesirable.

In order to prepare the above-described combustion catalyst according to the present invention, an aldehyde, a surfactant, and an inorganic fibrous carrier are added to the nitric acid solution of the noble metal dinitrodiammine complex.
The dinitrodiammine noble metal complex is reduced by the aldehyde by standing or heating at a temperature of 20° C. to form noble metal particles, and the particles are supported on the carrier. Thereafter, if necessary, it is dried at a temperature of about 100 to 300°C to obtain a combustion catalyst.

The mixing ratio of each component is not particularly limited, but the aldehyde is about 5 to 50% by weight based on the inorganic fibrous carrier.
, the surfactant is the dinitrodiammine nitric acid solution I
Preferably, it is about 0.1 to 2 cc relative to E.

If the noble metal ions are not completely reduced by the reduction with aldehyde alone, the reduction can be made more complete by further treating the noble metal-supported inorganic fibrous carrier at a hydrogen flow width of about 200 to 400°C.

According to the production method of the present invention described above, since the reduction of noble metal ions by aldehyde occurs in the liquid phase, the reduced noble metal particles are not biased during the reduction operation, and since high temperature treatment is not performed, there is no aggregation of the noble metal and the noble metal is The catalyst carrier is supported on the carrier in the form of ultrafine particles, and the surface tension of the solution is further reduced by the action of the surfactant, suppressing a decrease in the porosity of the carrier, thereby making it possible to obtain a catalyst carrier with a large surface area. Therefore, it is possible to obtain a combustion catalyst with superior catalytic performance compared to conventional combustion catalysts. Furthermore, there is almost no possibility that impurities will remain in the combustion catalyst obtained by almost complete decomposition of the dinitrodiammine by reduction, and if there is a possibility that impurities remain, the resulting catalyst is further heated in a hydrogen stream. By carrying out the reduction treatment inside, impurities can be completely removed and a good catalyst with high selectivity can be obtained.

(Actual example) Examples of the present invention will be described below, but the examples do not limit the present invention.

Example I 800 CC of dinitrodiammine platinum in nitric acid aqueous solution (
1.6g/β content as platinum) and formalin 20 at room temperature.
0g and l alkyltrimethylammonium chloride
cc added, and further specific surface area 100 m''/g.

50 g of T-alumina fibers containing 5% silica and having an average fiber diameter of 3 μm were immersed and left at 80° C. for 16 hours to reduce the dinitrodiammine platinum and precipitate platinum particles on the alumina sacrificial fiber carrier. . Thereafter, the carrier was dried at 120° C. for 4 hours to obtain a combustion catalyst.

The catalyst had no uneven appearance and no decrease in porosity was observed. The particle size of platinum was calculated by X-ray diffraction and was 458. This catalyst has a diameter of 50 mm and a length of 25 mm.
When air containing 2% methane was flowed into a cylindrical combustion tube cut out to a diameter of 1.5 cm, the tube was ignited at 250°C.

Comparative Example 1 Using the same dinitrodiammine platinum nitric acid aqueous solution and T-alumina fibers as in Example 1, the latter was immersed in the former, heated to 120°C, and then heat-treated at 800°C to obtain a combustion catalyst. Ta. This catalyst has some unevenness,
The porosity was also reduced.

When the particle size of platinum was calculated by X-ray diffraction method, it was found to be 95 people. When this catalyst was used for methane combustion in the same manner as in Example 1, the ignition temperature was 330°C.

Example 2 Nitric acid acidic aqueous solution of dinitrodiammine palladium 800
The same aldehyde, surfactant and fiber as in Example I were added to cc (containing 1.6 g/l as palladium), the dinitrodiammine palladium was reduced under the same conditions, and further dried to support palladium particles. An alumina fiber supported catalyst was obtained.

The catalyst had no uneven appearance and no decrease in porosity was observed. When the particle size of palladium was calculated by X-ray diffraction method, it was 4.5A. The ignition temperature of this catalyst was measured in the same manner as in Example 1 and found to be 250°C.

Comparative Example 2 A combustion catalyst was obtained by performing the same reduction treatment as in Comparative Example 1 using dinitrodiammine palladium instead of dinitrodiammine platinum. The palladium particle size was 95 mm and the ignition temperature was 330°C.

Comparative Example 3 Using the same dinitrodiammine palladium nitric acidic aqueous solution and T-alumina fiber as in Example 2, polyethylene glycol mono-p, which is a nonionic surfactant, was used.
-nonylphenyl ether 0.8cc (lee/
After that, the mixture was treated in the atmosphere at 800° C. for 1 hour to obtain a combustion catalyst. The particle size of palladium particles was measured by X-ray diffraction and found to be 94 people. This catalyst was uneven in places and had a low porosity. The ignition temperature of this catalyst was measured in the same manner as in Example 1 and was 310°C.
Met.

Example 3 Nitric acid acidic aqueous solution of dinitrodiammine palladium 800
cc (containing 1.6 g/β as palladium), 7.2 g of formalin and alkyltrimethylammonium chloride were added to 0.8 cc of C liquid, and silica 5 with a specific surface area IHm'/g and an average fiber diameter of 3 μm was added. % T-alumina fiber was soaked for 16 hours at 50°C.
After drying for 24 hours, the mixture was treated in a hydrogen stream at 300°C for 1 hour to obtain a combustion catalyst. The catalyst had no uneven appearance and no decrease in porosity was observed. The particle size of palladium was calculated by X-ray diffraction and was 45A.

The ignition temperature of this catalyst was measured in the same manner as in Example 1, and the ignition temperature was 240°C.

(Effects of the Invention) In the method for producing a combustion catalyst according to the present invention, when preparing a combustion catalyst, instead of the conventional calcination in the atmosphere, a noble metal dinitrodiammine complex is reduced with an aldehyde in a solution or further By reducing in a hydrogen stream, a combustion catalyst in which fine precious metal particles are uniformly supported on an inorganic fibrous carrier is prepared. Furthermore, by using a cationic surfactant during the preparation, it is possible to lower the surface tension of the solution, suppress the decrease in the porosity of the carrier, and prepare a highly active combustion catalyst with a large surface area. I have to.

Therefore, there is almost no aggregation of precious metal particles or a decrease in the porosity of the carrier due to high-temperature firing, and there is also no possibility that dinitrodiammine, etc., which is a raw material, may remain in the final product and produce a catalyst with unfavorable characteristics. Almost never occurs. Furthermore, since the reduction by aldehyde occurs in the liquid phase, non-uniformity of particle precipitation is almost eliminated, making it possible to provide a highly active combustion catalyst with extremely good performance in which particles are evenly distributed.

Claims (5)

[Claims] (1) In a method for producing a combustion catalyst comprising a noble metal catalyst component supported on an inorganic fibrous carrier, the carrier is immersed in a nitric acid solution of the dinitrodiammine complex of the noble metal to which an aldehyde and a surfactant have been added; A method for producing a combustion catalyst, which comprises reducing a noble metal complex to precipitate and support the corresponding noble metal on the carrier. (2) The method according to claim 1, wherein the noble metal is at least one selected from platinum, palladium, and ruthenium. (3) The method according to claim 1 or 2, wherein the aldehyde is at least one selected from formaldehyde, acetaldehyde, and probionaldehyde. (4) The method according to any one of claims 1 to 3, wherein the surfactant is at least one selected from alkyltrimethylammonium chloride, alkyldimethylpentylammonium chloride, and alkylaminoethanol. (5) A method for producing a combustion catalyst comprising a noble metal catalyst component supported on an inorganic fibrous carrier, wherein the carrier is immersed in a nitric acid solution of the dinitrodiammine complex of the noble metal to which an aldehyde and a surfactant are added. A method for producing a combustion catalyst, which comprises reducing a noble metal complex and further reducing the carrier in a hydrogen stream to precipitate and support the noble metal on the carrier.