JPH11147720A - Production of metal oxide including platinum or palladium in supperfine particles state - Google Patents

Abstract

PROBLEM TO BE SOLVED: To readily and efficiently obtain a metal oxide including superfine particles composed of platinum or palladium in a shape particle diameter distribution by hydrolyzing a metal alkoxide in a water-in-oil type micro emulsion including platinum-containing superfine particles compressing an insoluble complex of a platinum compound and a specific ammonium halide. SOLUTION: This water-in-oil type emulsion including platinum-containing superfine particles comprising an insoluble complex of a platinum compound and a specific ammonium halide is obtained by adding 5-250 pts.wt. oily liquid and 1-55 pts.wt. nonionic surfactant to 1 pt.wt. aqueous solution containing 0.001-0.2 wt.% water-soluble platinum compound (expressed in term of Pt), stirring the added product, adding 0.5-50 mol quarternary ammonium halide (per 1 mol Pt) of formula I (R<1> to R<4> are each an alkyl or an alkenyl; X is a halogen; with the proviso that the total of numbers of carbon of R<1> to R<4> is >=12) to the stirred material. A metal alkoxide is added to the obtained emulsion and hydrolyzed to provide the objective metal oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a metal oxide containing platinum or palladium in the form of ultrafine particles, a water-in-oil microemulsion containing platinum or palladium used for the production, and a method for producing the same. Related to a given product.

[0002]

2. Description of the Related Art Refractory metal oxides containing ultra-fine precious metal particles (silica, alumina, titania, zirconia, etc.)
Is advantageously used as a hydrogenation catalyst or the like. As a method for manufacturing such a micro-emulsion, first, a microemulsion containing ultra-fine particles of an insoluble noble metal salt is prepared, and then hydrazine monohydrate (N ₂ H ₄ .H ₂ O) is added to the micro-emulsion. In addition, a method is known in which the noble metal salt is reduced to noble metal ultrafine particles, and the noble metal ultrafine particles are immobilized on a metal oxide (JP-A-7-24634).
3). In the case of this method, it is very difficult to fix the noble metal to the metal oxide in the form of ultrafine particles having a uniform diameter because the insoluble noble metal salt is very easily aggregated. Of the noble metals, platinum and palladium were particularly difficult.

[0003]

The present invention provides a stable microemulsion containing ultrafine particles of a platinum compound or a palladium compound, and converts platinum or palladium from the microemulsion into ultrafine particles. It is an object of the present invention to provide a metal oxide and a method for producing the same.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, a platinum compound and the following general formula (1)

Embedded image (Wherein R ¹ , R ² , R ³ and R ⁴ represent an alkyl group or an alkenyl group, X represents a halogen atom, and the total number of carbon atoms contained in R ^{1 to} R ⁴ is 12 or more). The fourth represented
A water-in-oil type microemulsion containing platinum-containing ultrafine particles comprising an insoluble complex with a quaternary ammonium halide is provided. Further, according to the present invention, a palladium compound and the following general formula (2)

Embedded image (Wherein, R ¹ , R ² , R ³ and R ⁴ represent an alkyl group or an alkenyl group, X represents a halogen atom, and the total number of carbon atoms contained in R ^{1 to} R ⁴ is 19 or more). The fourth represented
Provided is a water-in-oil type microemulsion containing ultrafine palladium-containing particles comprising an insoluble complex with a quaternary ammonium halide. Further, according to the present invention, there is provided a method for producing a metal oxide containing ultrafine platinum particles, comprising a step of hydrolyzing a metal alkoxide in a microemulsion containing the ultrafine platinum particles. Furthermore, according to the present invention, there is provided a method for producing a metal oxide containing ultrafine palladium particles, comprising a step of hydrolyzing a metal alkoxide in a microemulsion containing ultrafine palladium particles.
Furthermore, according to the present invention, there is provided a metal oxide containing platinum or palladium obtained by the above method in the form of ultrafine particles.

[0005]

DETAILED DESCRIPTION OF THE INVENTION In order to prepare a water-in-oil microemulsion containing ultrafine particles comprising a platinum compound according to the present invention, first, an aqueous solution containing a water-soluble platinum compound is prepared. In this case, examples of the water-soluble platinum compound include chloroplatinic acid and chloroplatinate (ammonium salt, sodium salt, potassium salt, etc.). The concentration of the water-soluble platinum compound in the aqueous solution is 0.001 to 0.2% by weight, preferably 0.05 to 0.1% by weight in terms of platinum metal. next,
An oily liquid and a surfactant are added to the aqueous solution of the water-soluble platinum compound, and the mixture is stirred uniformly. Thereby, a water-in-oil type microemulsion in which water droplets containing a water-soluble platinum compound are dispersed in an oily liquid is obtained. In this case, the oily liquid has 5 to 18 carbon atoms, preferably 6 to 12 carbon atoms.
Aliphatic alcohols having 6 to 20 carbon atoms, preferably 8 to
12 aliphatic hydrocarbons; aromatic hydrocarbons and the like. Specific examples thereof include, for example, hexanol,
Heptanol, octanol, dodecyl alcohol, cetyl alcohol, cyclohexane, cycloheptane, n
-Hexane, n-heptane, isooctane, n-decane, benzene, toluene, xylene and the like. The ratio of the oily liquid used is an aqueous solution 1 containing a water-soluble platinum compound.
5 to 250 parts by weight, preferably 30 to 11 parts by weight per part by weight
0 parts by weight. As the surfactant, a nonionic surfactant is used. As a specific example,
Polyoxyethylene compounds having a structure in which ethylene oxide is added to a hydroxyl group of alcohol or phenol such as polyoxyethylene-p-nonylphenol and polyoxyethylene dodecyl ether. In this case, the weight of the oxyethylene group is 2 to 20, preferably 3 to 10.
It is. The proportion of the surfactant used is 1 to 55 parts by weight, preferably 5 to 5 parts by weight, per 1 part by weight of the aqueous solution of the water-soluble platinum compound.
25 parts by weight.

[0006] A precipitate-forming agent is added to the water-in-oil microemulsion obtained as described above. According to the study of the present inventor, as a precipitate forming agent in this case,
It has been found that an alkylammonium halide represented by the following general formula (1) is effective for forming a microemulsion containing ultrafine platinum particles having good stability without aggregation.

Embedded image In the general formula (1), R ¹ , R ² , R ³ and R ⁴ are an alkyl group or an alkenyl group, and the total number of carbon atoms contained in R ¹ , R ² , R ³ and R ⁴ is 12 or more. , Preferably 19 or more. The upper limit is about 26. X represents a halogen such as chlorine, bromine or iodine. Specific examples of such a precipitate forming agent include, for example, tetrapropylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium iodide, tetraamylammonium bromide, didodecyldimethylammonium bromide, cetyltrimethylammonium Bromide, cetyltrimethylammonium chloride and the like. Tetramethylammonium bromide, tetraethylammonium bromide and the like do not provide insoluble ultrafine particles with good stability. The addition amount of the quaternary ammonium halide is 0.5 to 5 per mol of platinum metal in the platinum compound contained in the aqueous solution.
0 mol, preferably 1 to 10 mol. The quaternary ammonium halide is preferably added as a mixture with an oily liquid.

[0007] By the addition of the quaternary ammonium halide, a water-insoluble conjugate (complex) of the platinum compound and the quaternary ammonium chloride is formed. To form The microemulsion containing ultrafine particles composed of a complex of the platinum compound and a quaternary ammonium halide has a significantly improved stability, and the platinum compound is maintained in an ultrafine state without agglomeration and coarsening. You. This microemulsion is applied as a raw material for producing a metal oxide containing ultrafine platinum particles.

The microemulsion containing the palladium compound in the form of ultrafine particles according to the present invention can be prepared in the same manner as the microemulsion containing the platinum compound in the form of ultrafine particles. In this case, examples of the water-soluble palladium compound include a soluble palladium salt such as palladium chloride. Examples of the precipitant include those represented by the following general formula (2).

Embedded image In the general formula (1), R ¹ , R ² , R ³ and R ⁴ are an alkyl group or an alkenyl group, and the total number of carbon atoms contained in R ¹ , R ² , R ³ and R ⁴ is 16 or more; Preferably 1
9 or more. The upper limit is about 26. X represents halogen such as chlorine, bromine and iodine. Specific examples of the precipitation-forming agent include didodecyldimethylammonium bromide, didodecyldimethylammonium chloride, cetyltrimethylammonium bromide, and cemetitrimethylammonium chloride. The metal oxide containing ultrafine palladium particles is produced using the microemulsion as a raw material.

In the metal oxide containing platinum or palladium in the form of ultrafine particles according to the present invention, the platinum or palladium exists in a compound or metal state. Palladium existing in a metal state is formed by reduction with a reducing agent (hydrogen, hydrazine, or the like). The average particle diameter of the ultrafine particles made of platinum or palladium is about 3 to 5 nm. The content of platinum or palladium in the metal oxide is not particularly limited, but is usually 0.05 to 10% by weight, preferably 0.5 to 5% by weight.

As a method for producing a metal oxide containing ultrafine platinum particles or ultrafine palladium particles according to the present invention, a microemulsion containing the insoluble platinum compound or palladium compound is impregnated with the metal oxide, and then dried, Baking, and then, if necessary, a method of reducing hydrogen, or adding a metal alkoxide to the microemulsion,
Hydrolysis is performed to obtain a metal oxide colloid containing an insoluble platinum compound or palladium compound, which is dried, calcined, and optionally reduced with hydrogen. In the present invention, it is preferable to use a method using a metal alkoxide, and this method will be described in detail below.

The metal alkoxide is not particularly limited as long as the metal oxide can be used as a catalyst carrier or the like. For example, a silicon alkoxide forming silica having a large surface area or an aluminum alkoxide forming alumina is preferably used, and a titanium alkoxide forming titania and a zirconium alkoxide forming zirconia can also be used. Further, metal alkoxides giving magnesia, boria, niobia, lanthanum oxide and the like can be used. The metal alkoxides may be used alone or as a mixture of two or more kinds. When a metal alkoxide mixture composed of different metals is hydrolyzed,
A composite oxide such as silica-alumina or silica-alumina-magnesia is obtained. Since the hydrolysis rate of metal alkoxide often differs greatly depending on the type,
When a composite oxide is obtained, a hydrolysis catalyst is preferably added to make the hydrolysis rate the same.

The following are specific examples of metal alkoxides used as raw materials for producing metal oxide colloids. Silicon alkoxides such as silicon tetraethoxide, silicon tetraisopropoxide and silicon tetrabutoxide; aluminum alkoxides such as aluminum triethoxide, aluminum triisopropoxide and aluminum tributoxide; titanium tetraethoxide, titanium tetraisopropoxide, and titanium Titanium alkoxides such as butoxide; zirconium alkoxides such as zirconium ethoxide, zirconium tetraisopropoxide and zirconium tetrabutoxide; magnesium dibutoxide, pentabutoxy niobium, tributoxy borane, tributoxy lanthanum and others. These metal alkoxides may be appropriately selected and used depending on the kind of a desired metal oxide colloid.

In the hydrolysis reaction of the metal alkoxide in the microemulsion, water required for the hydrolysis reaction of the metal alkoxide can be present in the microemulsion in advance, or in the hydrolysis reaction of the metal alkoxide. Can be added to the microemulsion. Water required for the hydrolysis reaction may be present in the microemulsion in its entirety at the start of the reaction, or may be gradually added as the reaction proceeds. The total amount of water used in the hydrolysis reaction of the metal alkoxide is 1 to 10 times, preferably 1 to 3 times the theoretical amount required for the hydrolysis reaction of the metal alkoxide. Depending on the type of metal alkoxide, the use of a catalyst may be preferred because of the slow hydrolysis rate.
In this case, water containing about 0.01 to 1% by weight of ammonia water or about 0.01 to 1% by weight of diluted nitric acid may be used as the water for hydrolysis.

The hydrolysis temperature varies depending on the type of the metal alkoxide, but is generally 20 to 60 ° C., preferably 3 to 60 ° C.
0-50 ° C. When water is added to the dispersion, it is desirable to add the water in portions during 0 to 8 hours, preferably 1 to 2 hours from the start of the reaction. After the addition of water is completed, the mixture is stirred for 20 to 12 hours, preferably 1 to 8 hours.
The hydrolysis reaction is completed by maintaining the temperature at 60 ° C., preferably 30 to 50 ° C., and then aging at the above temperature for 0 to 3 hours, preferably 1 to 2 hours. In this hydrolysis reaction, the reaction proceeds to form a colloidal product.
The pH of the reaction solution during the hydrolysis reaction varies depending on the type of metal alkoxide and the like, but is generally 3 to 11, preferably 7 to 11, and more preferably 8 to 10.

As described above, a metal oxide colloid containing platinum or palladium in the form of ultrafine particles is formed, which is present in the form of precipitated particles in the reactor after the aging period. This product is subjected to solid-liquid separation, the precipitate is separated from the mother liquor by filtration, washed with alcohol or the like to remove impurities such as surfactants, and then heated and dried under normal pressure or reduced pressure to obtain water or water. A supported catalyst can be obtained by removing the contained oily liquid and the like. The metal oxide containing ultrafine particles obtained in this way is crushed to a desired particle size and then, if necessary, calcined under a desired atmosphere, or formed into a desired shape after treatment such as hydrogen reduction, etc. It is good. The paste-like metal oxide colloid purified by washing with alcohol or the like may be processed into a honeycomb shape or the like, and then dried and used as a catalyst.

[0016]

Next, the present invention will be described in more detail with reference to examples. In addition, all the parts and% shown below are based on weight.

EXAMPLE 1 H ₂ Pt chloroplatinic acid was placed in a beaker having a capacity of 5.0 liters.
1 part of Cl ₄ and 5 parts of ion-exchanged water were added, and the mixture was stirred well to form a homogeneous solution. Then, 306 parts of 1-hexanol and a surfactant polyoxyethylene (5) -p-nonylphenyl ether (= NP-) were added to the aqueous solution. 5) Add 106 parts, 25 ° C
Immediately, a microemulsion containing 0.11 g of platinum as an ion in 100 g is formed. A stirrer was used for stirring. The microemulsion is of the single-phase water-in-oil type with a droplet diameter of 23 mm.
(Average value), and the average number of platinum ions contained in one droplet is 0.40. To this microemulsion are added 4 parts of cetyltrimethylammonium chloride (CTAC) and 392 parts of 1-hexanol,
Pt-
A dispersion containing ultrafine particles composed of a CTAC complex compound was prepared. 28% aqueous ammonia (catalyst) in the dispersion
0.5 part and 72 parts of ion-exchanged water are added and sufficiently stirred,
The pH was set to 4.5. Then, 192 parts of aluminum triisopropoxide and 392 parts of 1-hexanol were added and dissolved, and the resultant was immersed in a warm bath whose temperature could be controlled at 5 to 80 ° C. The reaction temperature was 25 ° C, and after stirring for 10 minutes,
The precipitate formed was immediately separated from the mother liquor. The obtained precipitate was washed three times with 200 parts of ethanol to sufficiently remove the surfactant and the oily liquid contained in the precipitate. The precipitate is dried at 80 ° C. for 12 hours, and then
Baking at 00 ° C for 2 hours, and further heating at 400 ° C in a hydrogen stream for 1 hour
When reduced for a long time, the supported ultrafine particles become platinum metal,
48 parts of an alumina gel containing 1.0% by weight of platinum were obtained. The alumina gel yield from the starting material aluminum triisopropoxide was 100% of the theoretical amount. Further, the yield of platinum from chloroplatinic acid was 100% of the theoretical amount.

EXAMPLE 2 H ₂ Pt chloroplatinic acid was placed in a beaker having an internal volume of 5.0 liters.
1 part of Cl ₄ and 5 parts of ion-exchanged water were added, and the mixture was stirred well to form a homogeneous liquid. Then, 306 parts of 1-hexanol and a surfactant polyoxyethylene (5) -p-nonylphenyl ether (= NP- 5) Add 106 parts, 25 ° C
Immediately, a microemulsion containing 0.11 g of platinum as an ion in 100 g is formed. A stirrer was used for stirring. The microemulsion is of the single-phase water-in-oil type with a droplet diameter of 23 mm.
(Average value), and the average number of platinum ions contained in one droplet is 0.40. 1.5 parts of tetrapropylammonium bromide (TPAB) and 392 parts of 1-hexanol are added to the microemulsion, and the mixture is maintained at 25 ° C. for 0.5 hour with sufficient stirring.
A dispersion containing ultrafine particles made of a t-TPAB complex compound was prepared. To the dispersion, 0.5 part of 28% ammonia water (catalyst) and 72 parts of ion-exchanged water were added and sufficiently stirred to adjust the pH to 4.5. Then, 192 parts of aluminum triisopropoxide and 392 parts of 1-hexanol were added and dissolved, and the resultant was immersed in a warm bath whose temperature could be controlled at 5 to 80 ° C. The reaction temperature was 25 ° C., and after stirring for 10 minutes, the formed precipitate was immediately separated from the mother liquor. The obtained precipitate was washed three times with 200 parts of ethanol to sufficiently remove the surfactant and the oily liquid contained in the precipitate.
The precipitate is dried at 80 ° C. for 12 hours, and then calcined at 600 ° C. for 2 hours under a stream of air.
For 1 hour, the supported ultrafine particles became platinum metal, and 48 parts of an alumina gel containing 1.0% by weight of platinum were obtained. The alumina gel yield from the starting material aluminum triisopropoxide was 100% of the theoretical amount. Further, the yield of platinum from chloroplatinic acid was 100% of the theoretical amount.

Example 3 Palladium chloride (Pd) was placed in a beaker having a capacity of 5.0 liters.
1 part of Cl ₂ , 0.5 part of concentrated hydrochloric acid and 9 parts of ion-exchanged water were added, and the mixture was stirred well to form a homogeneous solution. Then, 361 parts of 1-hexanol and a surfactant polyoxyethylene (2
3) 60 parts of dodecyl ether is added and stirred at 25 ° C., immediately forming a microemulsion containing 0.14 g of palladium as an ion in 100 g.
A stirrer was used for stirring. The microemulsion is of a single-phase water-in-oil type, the droplet diameter is calculated to be 67 ° (average value), and the number of platinum ions contained in one droplet is calculated to be 13 on average. Cetyltrimethylammonium chloride (CTA) was added to this microemulsion.
C) 2 parts and 1 part of 1-hexanol were added, and the mixture was kept at 25 ° C. for 0.5 hour with sufficient stirring to prepare a dispersion containing ultrafine particles composed of a Pd-CTAC complex compound. To the dispersion, 6 parts of 28% aqueous ammonia (catalyst) and 101 parts of ion-exchanged water were added, and the mixture was sufficiently stirred to adjust the pH to 9.5. 185 parts of silicon tetraethoxide was added and dissolved therein, and the resultant was immersed in a warm bath capable of controlling the temperature between 5 and 80 ° C. The reaction temperature was 50 ° C., and after stirring for 4 minutes,
The resulting precipitate was separated from the mother liquor. The resulting precipitate is 2
After washing three times with 00 parts of ethanol, the surfactant and oily liquid contained in the precipitate were sufficiently removed. This precipitate is
After drying at 0 ° C. for 12 hours, baking at 500 ° C. for 2 hours under flowing air, and further reducing at 350 ° C. for 2 hours in a hydrogen stream, the supported ultrafine particles become palladium metal,
45 parts of silica gel containing 1.3% by weight of palladium were obtained. The yield of silica gel from the starting material silicon tetraethoxide was 88% of the theoretical amount. The palladium yield from palladium chloride was 100% of the theoretical amount.

Comparative Example 1 H ₂ Pt chloroplatinate was placed in a beaker having an inner volume of 0.2 liter.
1 part of Cl ₄ and 5 parts of ion-exchanged water were added, and the mixture was stirred well to form a homogeneous solution. Then, 306 parts of 1-hexanol and a surfactant polyoxyethylene (5) -p-nonylphenyl ether (= NP-) were added to the aqueous solution. 5) Add 106 parts, 25 ° C
Immediately after stirring, a microemulsion containing 0.11 g of platinum as an ion in 100 g (hereinafter referred to as microemulsion A) is formed. A stirrer was used for stirring. The microemulsion is a one-phase water-in-oil type droplet, and the diameter of the droplet is calculated to be 23 ° (average value), and the number of platinum ions contained in one droplet is 0.1 mm on average.
It is calculated as 40. 4 parts of ammonium chloride NH ₄ Cl, 0.1 part of 0.1 N hydrochloric acid and ion-exchanged water 24 are placed in a beaker having an inner volume of 0.2 liter, and the mixture is stirred well to form a homogeneous solution. 306 parts and 106 parts of a surfactant polyoxyethylene (5) -p-nonylphenyl ether (= NP-5) were added, and the mixture was stirred at 25 ° C. and immediately, 0.9 g of NH ₄ Cl was added in 100 g.
A microemulsion containing 1 g (hereinafter referred to as microemulsion B) is formed. Simultaneously add beaker microemulsion A and microemulsion B having an inner volume of 0.5 liter and mix for 2 minutes for 10 minutes.
While maintaining the temperature at 5 ° C., a dispersion liquid of (NH ₄ ) ₂ PtCl ₆ ultrafine particles was prepared. 72 parts of ion-exchanged water was added to the dispersion and stirred sufficiently. Then, 192 parts of aluminum triisopropoxide and 392 parts of 1-hexanol were added and dissolved, and the resultant was immersed in a warm bath whose temperature could be controlled at 5 to 80 ° C.
The reaction temperature was 25 ° C., and after stirring for 10 minutes, the formed precipitate was immediately separated from the mother liquor. The resulting precipitate is
The precipitate was washed three times with 200 parts of ethanol to sufficiently remove the surfactant and the oily liquid contained in the precipitate. The precipitate is dried at 80 ° C. for 12 hours, and then dried at 600 ° C.
For 2 hours, and further reduced in a hydrogen stream at 400 ° C. for 1 hour, whereby the supported ultrafine particles become platinum metal,
Forty-eight parts of an alumina gel containing platinum by weight was obtained. The alumina gel yield from the starting material aluminum triisopropoxide was 100% of the theoretical amount. Further, the yield of platinum from chloroplatinic acid was 100% of the theoretical amount.

Comparative Example 2 An alumina gel containing no platinum was prepared in the same manner as in Example 1 except that chloroplatinic acid was not added. Using this alumina gel as a carrier, after supporting chloroplatinic acid by a dipping method according to a conventional method, drying at 80 ° C. for 12 hours, and calcining it at 600 ° C. for 2 hours under an air flow,
Further reduction was carried out in a hydrogen stream at 400 ° C. for 1 hour to produce a platinum-alumina catalyst supporting 1.0% by weight of platinum.

Comparative Example 3 Palladium-free silica gel was prepared in the same manner as in Example 3, except that palladium chloride and concentrated hydrochloric acid were not added. Using this silica gel as a carrier, palladium chloride is supported by an immersion method according to a conventional method, and then dried at 80 ° C. for 12 hours.
By calcining at 0 ° C. for 2 hours and further reducing at 350 ° C. for 2 hours in a hydrogen stream, a palladium-silica catalyst supporting 1.3% by weight of palladium was produced.

Comparative Example 4 In Comparative Example 2, a silica gel Cariact-50 manufactured by Fuji Silysia was used as a carrier, and palladium supported on 1.3% by weight of palladium was impregnated by the same impregnation method.
A silica catalyst was prepared.

The platinum particles of the catalysts obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were compared. As the particle diameter measuring method, a particle diameter measurement by transmission electron microscope (TEM) observation and a half width method by X-ray diffraction measurement were used. Also,
The standard deviation representing the width of the particle size distribution was determined from TEM observation. Table 1 shows the results. As can be seen from Table 1,
It can be seen that the average particle size of platinum contained in the metal oxide prepared by the method of the present invention is much smaller than that prepared by the immersion method. Further, it can be seen that the standard deviation is extremely small. That is, it can be seen that the particle size distribution of platinum prepared by the method of the present invention is very sharp. It can also be seen that Comparative Example 1, which is almost the same as the preparation method of the present invention, increases when the type of fine particles is different. Therefore, it is understood that the use of ultrafine particles of a complex of alkylammonium halide and platinum makes it possible to efficiently prepare a metal oxide containing small fine particles of platinum with a sharp particle size distribution.

[0025]

[Table 1]

The results for palladium are shown in Table 2.
Also in this case, the same result as in the case of platinum was obtained.

[0027]

[Table 2]

[0028]

According to the present invention, a metal oxide containing ultrafine particles of platinum or palladium with a sharp particle size distribution can be efficiently produced. Further, the microemulsion containing platinum or palladium in the form of ultrafine particles used as a raw material in the present invention has extremely excellent dispersion stability, and the ultrafine particles do not easily aggregate and coarsen. Therefore, by using the microemulsion of the present invention, a metal oxide containing ultrafine particles of platinum or palladium with a sharp particle size distribution can be easily and efficiently produced. The metal oxide containing platinum or palladium in the form of ultrafine particles according to the present invention is advantageously used in various applications, for example, as a catalyst, especially as a hydrogenation catalyst.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C07F 15/00 C07F 15/00 F

Claims (6)

[Claims] 1. A platinum compound and the following general formula (1): (Wherein R ¹ , R ² , R ³ and R ⁴ represent an alkyl group or an alkenyl group, X represents a halogen atom, and the total number of carbon atoms contained in R ^{1 to} R ⁴ is 12 or more). The fourth represented
A water-in-oil type microemulsion containing platinum-containing ultrafine particles comprising an insoluble complex with a quaternary ammonium halide. 2. A palladium compound and the following general formula (2): (Wherein, R ¹ , R ² , R ³ and R ⁴ represent an alkyl group or an alkenyl group, X represents a halogen atom, and the total number of carbon atoms contained in R ^{1 to} R ⁴ is 19 or more). The fourth represented
A water-in-oil microemulsion containing palladium-containing ultrafine particles comprising an insoluble complex with a quaternary ammonium halide. 3. A method for producing a metal oxide containing ultrafine platinum particles, comprising a step of hydrolyzing a metal alkoxide in the microemulsion according to claim 1. 4. A method for producing a metal oxide containing ultrafine palladium particles, comprising a step of hydrolyzing a metal alkoxide in the microemulsion according to claim 2. 5. A metal oxide containing ultrafine platinum particles obtained by the method of claim 3. 6. A metal oxide containing ultrafine palladium particles obtained by the method of claim 4.