JPH0884930A - Preparation of platinum-supported catalyst - Google Patents

Abstract

PURPOSE: To uniformly support platinum fine particles at a desired concentration without increasing the number of processes. CONSTITUTION: Into a nitric acid solution of dinitro-diamine platinum containing a support is added ethanol in a ratio of 4-280mol to 1mol of platinum, 6-60vol.% of a total reduction reaction solution, the temperature of the reduction reaction liquid is adjusted at 60 deg.C-boiling point, and platinum fine particles is reduced and supported on the support. In this way, platinum is reduced at a high rate of reduction and supported, and the reduced platinum fine particles are prevented from coagulating even in the absence of a surfactant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a platinum-supported catalyst in which platinum fine particles are supported on a carrier.

[0002]

2. Description of the Related Art Conventionally, platinum-supported catalysts are generally prepared by adding a reducing agent such as formic acid, sodium formate, hydrazine or sodium borohydride to an aqueous solution of chloroplatinic acid containing a carrier such as alumina or carbon to form fine platinum particles. It is produced by reducing and supporting it on a carrier. In the above production, the reduced platinum fine particles agglomerate to increase the particle size and reduce the catalytic activity. Therefore, a surfactant or the like is added to prevent the platinum fine particles from aggregating.

[0003]

However, in the conventional method for producing a platinum-supported catalyst, although a surfactant is added to prevent the aggregation of platinum fine particles, the aggregation prevention effect is insufficient and the platinum concentration varies. On the other hand, there are problems that cleaning for removing the surfactant from the final product is complicated, and that heating is required. Therefore,
The present invention is characterized by providing a method for producing a platinum-supported catalyst capable of uniformly supporting platinum fine particles at a desired concentration without increasing the number of steps.

[0004]

In order to solve the above-mentioned problems, the method for producing a platinum-supported catalyst of the present invention comprises: a dinitrodiamine platinum nitric acid solution containing a carrier;
~ 280 mol of ethanol is added to the entire reduction reaction solution at 1-60 vol.
%, And the temperature of the reduction reaction solution is set to 60 ° C. to the boiling point to reduce the fine platinum particles and support them on a carrier. The temperature of the reduction reaction liquid is preferably the boiling point. The ethanol is preferably 6 to 15 vol. Of the whole reduction reaction solution.
%. Further, the reduction reaction is preferably continued until the reduction reaction liquid becomes colorless.

[0005]

In the method for producing the platinum-supported catalyst of the present invention,
Since platinum is reduced and supported at a high support rate, a catalyst having a desired supported platinum concentration can be prepared, and reduced platinum fine particles do not aggregate even if a surfactant is not used. Absent. Ethanol is 4 per mole of platinum
If it is less than the molar amount, the platinum fine particles are not reduced, and 2
If it exceeds 80 moles, a large amount of platinum ions remain in the reaction solution,
Not supported by the carrier. If ethanol is less than 1 vol.% Of the entire reduction reaction solution, the concentration product with platinum ions becomes too small to reduce platinum, and if it exceeds 60 vol.%,
On the contrary, the concentration of ethanol is too high and a large amount of platinum ions remain in the reaction solution, so that they are not sufficiently supported. If the reduction reaction is continued even after the reduction reaction liquid becomes colorless, the platinum fine particles agglomerate.

[0006]

EXAMPLES Examples of the present invention will be described below together with comparative examples and conventional examples.

[0007]

Example 1 First, a dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to obtain a solution of 4685 ml, and 123.2 g of acetylene black powder as a carbon carrier was added thereto and mixed. Then, 318 ml of special grade ethanol (Pt: EtOH (mol) =
1: 34.5, 6.4 vol.%) Was added and mixed, and the mixture was heated under reflux and kept at the boiling point for 6 hours to carry out reduction / support of platinum fine particles. The boiling point was 94.6 ° C. Next, after allowing to cool for 1 hour, the carbon carrier supporting the platinum fine particles was collected by filtration, washed, and dried in air at a temperature of 60 ° C. for 16 hours to obtain a platinum-supported catalyst. The obtained platinum-supported catalyst had a reduction / support ratio of platinum of 99.9% or more from the analysis result of the reduction waste liquid, and the particle size of platinum fine particles supported by X-ray powder diffraction measurement was 18 angstrom. When the dispersed state of the platinum particles was observed with an electron microscope (TEM), the particles did not aggregate.

[0008]

Example 2 First, a dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to obtain a solution of 4380 ml, to which 110.0 g of acetylene black powder as a carbon carrier was added and mixed. Then, 625 ml of special grade ethanol (Pt: EtOH (mol) =
1: 34.5, 6.4 vol.%) Was added and mixed, and the mixture was heated under reflux and kept at the boiling point for 4 hours to reduce / support platinum fine particles. The boiling point was 91.2 ° C. Next, after allowing to cool for 1 hour, the carbon carrier supporting the platinum fine particles was collected by filtration, washed, and dried in air at a temperature of 60 ° C. for 16 hours to obtain a platinum-supported catalyst. The obtained platinum-supported catalyst showed that the reduction / support ratio of platinum was 99.9% or more based on the analysis result of the reduction waste liquid, the particle size of platinum fine particles supported by X-ray powder diffraction measurement was 16 angstrom, and the TEM When the dispersed state of the platinum particles was observed, the particles did not aggregate.

[0009]

Example 3 First, a dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to make a 4110 ml solution, and 123.2 g of acetylene black powder as a carbon carrier was added thereto and mixed. Then, 900 ml of special grade ethanol (Pt: EtOH (mol) =
1: 97.6, 18.0 vol.%) Was added and mixed, and the mixture was heated under reflux and kept at the boiling point for 4 hours to carry out reduction / support of platinum fine particles. The boiling point was 90.3 ° C. Next, after allowing to cool for 1 hour, the carbon carrier supporting the platinum fine particles was collected by filtration, washed, and dried in air at a temperature of 60 ° C. for 16 hours to obtain a platinum-supported catalyst. The obtained platinum-supported catalyst showed that the reduction / support ratio of platinum was 98.3% based on the analysis result of the reduction waste liquid.
The particle size of the supported platinum fine particles was 19 angstrom from the linear powder diffraction measurement, and when the dispersed state of the platinum particles was observed by TEM, the particles did not aggregate.

[0010]

Example 4 First, a dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to obtain a solution of 2510 ml, and 110.0 g of acetylene black powder as a carbon carrier was added thereto and mixed. Then, 2500 ml of reagent grade ethanol (Pt: EtOH (mol) =
1: 271.2, 50.0 vol.%) Was added and mixed, and the mixture was heated under reflux and kept for 20 hours until no platinum ions remained at the boiling point to carry out reduction / support of platinum fine particles. The boiling point was 82.8 ° C. Next, after allowing to cool for 1 hour, the carbon carrier supporting the platinum fine particles was collected by filtration, washed, and dried in air at a temperature of 60 ° C. for 16 hours to obtain a platinum-supported catalyst. The obtained platinum-supported catalyst was a reduction waste liquid (it did not become colorless because platinum ions remained).
According to the analysis results, the reduction / support ratio of platinum was 96.7%, the particle size of the platinum fine particles supported by X-ray powder diffraction measurement was 17 Å, and the dispersion state of the platinum particles was observed by TEM. There was no aggregation between them.

[0011]

Example 5 First, a dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to a solution of 4930 ml, and 123.2 g of acetylene black powder as a carbon carrier was added thereto and mixed. Then, 70 ml of reagent grade ethanol (Pt: EtOH (mol) = 1.7
(6, 1.4 vol.%) Was added and mixed, and the mixture was heated under reflux and kept at the boiling point for 20 hours to reduce and support the platinum fine particles. The boiling point was 98.7 ° C. Next, after allowing to cool for 1 hour, the carbon carrier supporting the platinum fine particles was collected by filtration, washed, and dried in air at a temperature of 60 ° C. for 16 hours to obtain a platinum-supported catalyst. The obtained platinum-supported catalyst was found to have a platinum reduction / support ratio of 99.9% from the analysis result of the reduction waste liquid, and the particle size of the platinum fine particles supported by X-ray powder diffraction measurement was 28 Å.

[0012]

Example 6 First, a dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to a solution of 4725 ml, and 123.2 g of acetylene black powder as a carbon carrier was added and mixed. Then, 275 ml of special grade ethanol (Pt: EtOH (mol) =
1: 29.8, 5.5 vol.%) Was added and mixed, and the mixture was heated under reflux and kept at the boiling point for 7 hours to reduce and support platinum fine particles. The boiling point was 96.1 ° C. Next, after allowing to cool for 1 hour, the carbon carrier supporting the platinum fine particles was collected by filtration, washed, and dried in air at a temperature of 60 ° C. for 16 hours to obtain a platinum-supported catalyst. In the obtained platinum-supported catalyst, the reduction / support ratio of platinum was 99.9% based on the analysis result of the reduction waste liquid, and the particle size of platinum fine particles supported by X-ray powder diffraction measurement was 23 Å.

[0013]

Example 7 First, dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to obtain a solution of 4380 ml,
Acetylene black powder as a carbon carrier to this 1
10.0 g was added and mixed. Then, 625 ml of reagent grade ethanol (Pt: EtOH (mol) = 1: 6) was added to the above mixture.
7.8, 12.5vol.%) And mix, and reflux at 85 ℃
The temperature was maintained at 20 ° C. and kept for 20 hours to reduce and support the platinum fine particles. Next, after allowing to cool for 1 hour, the carbon carrier supporting the platinum fine particles was collected by filtration, washed, and dried in air at a temperature of 60 ° C. for 16 hours to obtain a platinum-supported catalyst. The obtained platinum-supported catalyst had a platinum reduction / support ratio of 94.8% based on the analysis result of the reduction waste liquid (since platinum ions remained, it was not colorless), and the platinum supported by X-ray powder diffraction measurement was carried out. The particle size of the microparticles was 21 Å.

[0014]

Example 8 First, a dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to obtain a solution of 2510 ml, and 110.0 g of acetylene black powder as a carbon carrier was added thereto and mixed. Then, 2500 ml of reagent grade ethanol (Pt: EtOH (mol) =
1: 271.2, 50vol.%) Is added, mixed and refluxed.
Reduce the platinum particles by heating to 60 ° C and holding for 16 hours.
Loading was carried out. Next, after allowing to cool for 1 hour, the carbon carrier supporting the platinum fine particles was collected by filtration, washed, and dried in air at a temperature of 60 ° C. for 16 hours to obtain a platinum-supported catalyst. In the obtained platinum-supported catalyst, the reduction / support ratio of platinum was 88% based on the analysis result of the reduction waste liquid, and the particle size of the supported platinum fine particles was 17 angstrom according to the X-ray powder diffraction measurement.

[0015]

[Comparative Example 1] A dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to a solution of 2475 ml, and acetylene black powder 123.2 was used as a carbon carrier.
g was added and mixed. Then, 25 ml of reagent grade ethanol (Pt: EtOH (mol) = 1: 2.7, 1
vol.%) was added and mixed, and the mixture was heated under reflux and kept at the boiling point for 20 hours to reduce and support the platinum fine particles. The boiling point was 99.0 ° C. However, after cooling for 1 hour and then filtering, the waste liquid was also yellow and it was found from the analysis result of the waste liquid that 90% or more of the charged platinum was not supported and remained in the liquid.

[0016]

[Comparative Example 2] A dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to obtain a solution of 3970 ml, on which acetylene black powder 123.2 was used as a carbon carrier.
g was added and mixed. Next, 3250 ml of reagent grade ethanol (Pt: EtOH (mol) = 1: 352.
(6, 45 vol.%) Was added and mixed, and the mixture was heated under reflux and kept at the boiling point for 20 hours to reduce and support the platinum fine particles. The boiling point was 83.0 ° C. However, when the solution was left standing to cool for 1 hour and then filtered, the waste solution was yellow again, and the platinum reduction / support ratio was about 60% from the analysis result of the waste solution.

[0017]

[Comparative Example 3] A dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to obtain a solution of 4380 ml, on which acetylene black powder 110.0 as a carbon carrier was added.
g was added and mixed. Then, to the above mixture, 625 ml of special grade ethanol (Pt: EtOH (mol) = 1: 67.8,
12.5vol.%) And mix and heat to reflux 55
The platinum fine particles were reduced and supported by holding at 20 ° C for 20 hours. However, after cooling for 1 hour and then filtering, the waste liquid was also yellow, and it was found from the analysis result of the waste liquid that 95% or more of the introduced platinum was not supported and remained in the liquid.

[0018]

[Comparative Example 4] A dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to prepare a solution of 9930 ml, and acetylene black powder 123.2 was used as a carbon carrier.
g was added and mixed. Then, 70 ml of reagent grade ethanol (Pt: EtOH (mol) = 1: 7.6,
0.7 vol.%) Was added and mixed, and the mixture was heated under reflux and kept at the boiling point for 20 hours to reduce and support the platinum fine particles.
The boiling point was 99.3 ° C. However, after cooling for 1 hour and then filtering, the waste liquid was also yellow and it was found from the analysis result of the waste liquid that 90% or more of the charged platinum was not supported and remained in the liquid.

[0019]

[Comparative Example 5] A dinitrodiamine platinum nitric acid solution containing 30.80 g of platinum was diluted with pure water to obtain 1070 ml of a solution, and acetylene black powder 123.2 was used as a carbon carrier.
g was added and mixed. Then, 2500 ml of reagent grade ethanol (Pt: EtOH (mol) = 1: 271.
(2, 70 vol.%) Was added and mixed, and the mixture was heated under reflux and kept at the boiling point for 20 hours to reduce and support the platinum fine particles. The boiling point was 80.2 ° C. However, when the solution was left standing to cool for 1 hour and then filtered, the waste solution was yellow again, and the reduction / support ratio of platinum was about 80% from the analysis result of the waste solution.

[0020]

[Prior art example] First, 250 ml of isopropyl alcohol and water
2 g of polyvinyl alcohol was dissolved in 100 ml of the mixed solution, 100 ml of a chloroplatinic acid solution having a platinum concentration of 20 g / 1 was added thereto, the pH was adjusted to 2.2 with aqueous ammonia, and the total amount was adjusted to 500 ml with distilled water. Then, 20 g of acetylene black powder as a carbon carrier was added to the above mixture and mixed well. Then, the mixed solution was refluxed and heated at a temperature of 70 ° C. and held for 6 hours to reduce and support the platinum fine particles. Next, after allowing to cool for 1 hour, the carbon carrier supporting the platinum fine particles was collected by filtration, washed, and further dried to obtain a platinum-supported catalyst. The obtained platinum-supported catalyst had a reduction / support ratio of platinum of 94% from the analysis result of the reduction waste liquid, and the particle size of the platinum fine particles supported by X-ray powder diffraction measurement was as large as 30 to 50 angstroms, and there were variations. As a result of observing the dispersion state of the platinum particles with a TEM, aggregation of platinum fine particles was found in some places.

[0021]

As described above, according to the method for producing a platinum-supported catalyst of the present invention, platinum is reduced and supported at a high reduction rate, and reduced platinum is used without using a surfactant. Since the agglomeration of the fine particles does not occur, the number of steps can be reduced as compared with the conventional method, and a platinum-supported catalyst in which platinum fine particles are uniformly supported at a desired concentration can be obtained.

Claims (4)

[Claims] 1. A dinitrodiamine platinum nitric acid solution containing a carrier is added with 4 to 280 mol of ethanol per mol of platinum in an amount of 1 to 60 vol.% Of the entire reduction reaction liquid, and the temperature of the reduction reaction liquid is 60 ° C. to boiling. In particular, a method for producing a platinum-supported catalyst, characterized in that fine platinum particles are reduced and supported on a carrier. 2. The method for producing a platinum-supported catalyst according to claim 1, wherein the temperature of the reduction reaction liquid is at a boiling point. 3. The total amount of ethanol contained in the reduction reaction solution is 6%.
It is -15 vol.%, Claim 1 or 2 characterized by the above-mentioned.
A method for producing the platinum-supported catalyst described. 4. The reduction reaction is continued until the reduction reaction liquid becomes colorless.
A method for producing the platinum-supported catalyst described.