JPH08196905A - Particle size-adjusted noble metal-carbon catalyst - Google Patents

Abstract

PURPOSE: To provide a noble metal carbon catalyst having excellent catalytic activity and filtration separability and repeatedly usable. CONSTITUTION: The particle sizes of particles of an activated carbon-based carrier are so adjusted as to make particles with 60μm or smaller particle size occupy 90% cumulative volume in a distribution of the volume of particle sizes and as to make the cumulative value of fine particles with 3.3μm or smaller size in a distribution of the number of particle sizes be less than 40% and a noble metal catalytic component is carried on the activated carbon-based carrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noble metal carbon catalyst having a specific particle size distribution and useful for industrial chemical reactions.

[0002]

2. Description of the Related Art Powdery noble metal carbon catalysts are generally used in a state of being dispersed in a reaction solution. For example, in a hydrogenation reaction, hydrogen, a reaction solution, and a catalyst are in the gas phase in the reaction system,
The catalytic reaction proceeds in a state where they are in contact with each other in the liquid phase and the solid phase. Therefore, the contact and dispersibility of each phase have a great influence on the reaction rate. Generally, by reducing the average particle size of the catalyst, the number of catalysts per unit weight of the catalyst is increased and the dispersibility is improved. In this way, a highly active catalyst can be produced.

On the other hand, it is also important that catalysts used industrially have excellent filter separation properties. That is, after the reaction, there is a step of separating the reaction solution and the catalyst by filtration, the reaction solution proceeds to the next step, and the catalyst separated by filtration is reused until the activity decreases. When the amount of the catalyst used is large, the filtration time becomes long and the productivity decreases. At this time, even if the catalyst activity is increased and the reaction time is shortened, if the filtration time seems to exceed it, such a catalyst cannot be said to have high performance as an industrial catalyst. In order to produce a catalyst having good filterability, a catalyst having a coarse particle size is advantageous, but as described above, there is a problem in dispersibility in the reaction solution and it is also disadvantageous in terms of activity.

Since the filter paper or filter cloth usually used has a trapping particle diameter of 2 to 3 μm, the presence of fine particles of less than 3 μm causes filtration leakage and clogging of the filtration surface, resulting in a reduction in filtration speed. In such a case, it can be dealt with by coating the filter surface with a filter aid, but there arises a problem that the catalyst cannot be reused.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a particle size controlled noble metal carbon catalyst which is highly active and has excellent filterability.

[0006]

Means for Solving the Problems From the above viewpoints, the present inventors have found that a catalyst having both activity and filterability can be obtained by controlling the particle size of the catalyst, and completed the present invention.

Granular catalysts generally have a volume particle size distribution in the range 1-1000 μm. In order to increase the catalytic activity, it is advantageous that the average particle size is as small as possible. The finer the particles are, the more the activity is improved, but the amount of fine particles that cause filtration leakage and clogging of the filtration surface is increased, which hinders the filtration and separation process. In addition, when fine particles that hinder the filtration and separation process are removed in advance, the economical efficiency of the catalyst manufacturing process decreases.

The noble metal carbon catalyst of the present invention contains a carrier composed of activated carbon particles and a noble metal catalyst component supported thereon, and the activated carbon particles have a particle size of 90 μm or less in cumulative 90% in volume particle size distribution. The particle size is adjusted so that the cumulative value of fine particles having a particle size distribution of 3.3 μm or less in the number particle size distribution is less than 40%.

In the catalyst of the present invention, the noble metal catalyst component preferably contains palladium or platinum.

[0010]

In the catalyst of the present invention, the cumulative value of the number particle size distribution of fine particles having a particle size of 3.3 μm or less of the activated carbon is adjusted to less than 40%, and the cumulative value of volume distribution of particles having a particle size of 60 μm or less is adjusted. Has reached 90%,
The obtained noble metal carbon catalyst has both a catalytic activity that is excellent in practical use and a filtration separability, and can significantly improve the efficiency and productivity of the chemical reaction process. Further, when the catalyst of the present invention is used, the use of the filter aid becomes unnecessary, so that the catalyst can be reused.

In the present invention, in the volume particle size distribution of the activated carbon carrier, cumulative 90% has a particle size of 60 μm or less, and in the number particle size distribution of the activated carbon carrier,
In order to make the cumulative value of fine particles of 3.3 μm or less smaller than 40%, the raw material carbon of activated carbon is crushed to a desired particle size (60 μm or less) and finely divided using a classifier. Particles may be removed. The above pulverization and classification may be performed on activated carbon.

In the present invention, in the volume particle size distribution of the activated carbon carrier, the size of the particles contained in 90% cumulatively is 6.
When it is larger than 0 μm, the activity of the obtained catalyst becomes insufficient. Further, in the present invention, when the cumulative value of fine particles of 3.3 μm or less in the number particle size distribution of the activated carbon support is 40% or more, there is a disadvantage that the time required for the filtration and separation step increases.

The particle size adjustment (classification) of the activated carbon support used in the present invention is generally preferably performed before the catalyst production, but may be performed during the catalyst production. In the latter case,
Particle size can be adjusted by classifying with a wet or dry classifier.

As the activated carbon used in the present invention, those produced from woody materials, peat, tar, coconut shell and the like can be used.

In the present invention, palladium, platinum, ruthenium, rhodium, iridium, osmium, gold, silver, rhenium and the like can be used as the noble metal catalyst component, but palladium or platinum is preferably used.

In order to produce the catalyst of the present invention, for example, an activated carbon carrier is suspended in water, a water-soluble salt of a noble metal is added dropwise to completely adsorb it, and then formalin, formic acid, sodium borohydride or the like is used. A method of reducing with a reducing agent may be performed.

In the catalyst of the present invention, the supported amount of the noble metal catalyst component is preferably 1 to 20% (weight) in terms of metal. Further, in the catalyst of the present invention, in addition to the noble metal component,
An additive component, for example, one or more kinds of K, Na, Li, Pb, and Sb may be contained.

[0018]

The present invention will be described in more detail with reference to the following examples. Microtrac II SRA (0.7-700 μm) manufactured by Nikkiso Co., Ltd. was used for particle size measurement. In the text, "particle size distribution measurement result" output from the measuring device
Is expressed by "volume particle size distribution" and "number distribution calculation result"
Is represented as "number particle size distribution", and "MV" is represented as "volume weighted average particle diameter". Further, the "frequency" is the frequency (%) in a certain particle diameter range, and the "cumulative" is a value obtained by adding all the frequencies below a certain particle diameter. “Cumulative 90%” means that the cumulative value of particle size frequency is 90%.

Example 1 After dissolving 1.6 g of palladium in aqua regia, the solution was concentrated to obtain a 15 wt% palladium chloride solution. 2.8-176
It has a volume particle size distribution of μm and a cumulative particle size of 90% of 5
9.05 μm or less, volume-weighted average particle size is 28.62 μ
m, in the number particle size distribution, 30 g of activated carbon in which the cumulative value of fine particles of 3.3 μm or less is adjusted to 34.06% is 3
While being suspended in 00 ml of water, the palladium chloride solution was added dropwise thereto. After 16 hours, a 20 wt% caustic soda aqueous solution was added until the pH of the mixed system reached 13. After 2 hours, 7 ml of a 37 wt% formalin aqueous solution was added to the mixture, the temperature was kept at 90 ° C. for 1 hour to reduce the palladium compound, and the mixture was filtered, washed with water and dried to prepare a 5% palladium carbon catalyst.

5 g of this catalyst was added to ion-exchanged water 30 at 30 ° C.
The suspension was suspended in 0 ml, and the suspension was filtered with a circular filter paper (Toyo Roshi Kaisha, Ltd. No. 131) having a diameter of 3 cm to obtain 0.1 kgf /
It was 12 minutes when it was subjected to filtration under the condition of applying a nitrogen pressure of cm ² and the filtration time until nitrogen was ejected from the filter paper was measured.

Separately, 0.91 g of dinitrotoluene was dissolved in ethanol to a liquid volume of 25 ml, and 50 mg of the above catalyst was added to this solution. This reaction system was placed in a reaction vessel, and 10 ml of ethanol was further added. After the temperature of the reaction vessel and the entire hydrogen line leading to the reaction vessel was set to 30 ° C., the atmosphere was replaced with nitrogen and further replaced with hydrogen, and the nitro group of dinitrotoluene was subjected to hydrogenation reaction while shaking the container. At this time, when a catalyst activity test was performed for 15 minutes while adding hydrogen so that the pressure was kept at normal pressure, the hydrogen absorption amount was 550
ml.

Comparative Example 1 Has a volume particle size distribution of 2.8 to 500 μm, and has a cumulative 90%.
Example 1 except that activated carbon having a particle diameter of 225.26 μm or less and a volume weighted average particle diameter of 70.53 μm or 3.3 μm or less has a particle size distribution of 50.21% is used. A 5% palladium carbon catalyst was prepared in the same manner as in. When a filtration test of the obtained catalyst was conducted in the same manner as in Example 1, the filtration time was 30 minutes, and in the catalyst activity test with dinitrotoluene, the hydrogen absorption amount was 500 ml.

Example 2 3.38 g of palladium was dissolved in aqua regia and concentrated to 1
A 5 wt% palladium chloride solution was obtained. 30 g of activated carbon used for particle size adjustment used in Example 1 was suspended in 300 ml of water, and the palladium chloride solution was added dropwise thereto. 16 hours later,
A 20 wt% caustic soda solution was added until pH = 13. After 2 hours, 7 ml of 37 wt% formalin aqueous solution was added and the temperature was kept at 90 ° C. for 1 hour to reduce the palladium compound, followed by filtration, washing with water and drying to prepare a 10% palladium carbon catalyst.

Separately, ethanol was added to 5 g of benzyl benzoate to make the liquid volume 25 ml, and 200 mg of the catalyst was added thereto. This solution was placed in a reaction vessel, and 10 ml of ethanol was further added. After the reaction vessel and the entire hydrogen line leading to the reaction vessel were heated to 30 ° C., nitrogen substitution and then hydrogen substitution were performed, and a debenzylation reaction was performed while shaking the vessel.
When an activity test was performed for 30 minutes while adding hydrogen so that the pressure was kept at normal pressure, the hydrogen absorption amount was 400 ml.

Comparative Example 2 A 10% palladium carbon catalyst was prepared in the same manner as in Example 2 except that the activated carbon of Comparative Example 1 was used. Example 2
When the activity test of benzyl benzoate was conducted in the same manner as
The amount of absorbed hydrogen was 350 ml.

Comparative Example 3 Volume distribution of 2.8 to 125 μm, 90% cumulative
Particle size of 44.16μm or less, volume-weighted average particle size of 22.97μm, 3.3μm or less of the fine particles of the cumulative value of the activated carbon is adjusted to be 44.05% in number particle size distribution A 5% palladium carbon catalyst was prepared in the same manner as in Example 1 except that the above was used. When a filtration test was conducted in the same manner as in Example 1, the filtration time was 22.5 minutes.

Comparative Example 4 Has a volume particle size distribution of 3.9 to 125 μm and a cumulative 90%.
Particle size of 66.47 μm or less and volume-weighted average particle size of 33.04 μm or 3.3 μm or less was used. A 5% palladium carbon catalyst was prepared in the same manner as in Example 1 except that. When a filtration test was conducted in the same manner as in Example 1, the filtration time was 4.8 minutes. The hydrogen absorption amount in the catalyst activity test with dinitrotoluene was 375 ml.

Table 1 shows the volume particle size distribution of the activated carbon carriers used in Examples 1 and 2.

[0029]

[Table 1]

Table 2 shows the number particle size distribution of the activated carbon carriers used in Examples 1 and 2.

[0031]

[Table 2]

Table 3 shows the volume particle size distributions of the activated carbon carriers used in Comparative Examples 1 and 2.

[0033]

[Table 3]

Table 4 shows the number particle size distribution of the activated carbon carriers used in Comparative Examples 1 and 2.

[0035]

[Table 4]

Example 3 3.9 g of platinum was dissolved in aqua regia and then concentrated to obtain a 15 wt% chloroplatinic acid solution. 120 g of the particle size-adjusted activated carbon used in Example 1 and 23 g of sodium carbonate were put into 1200 ml of water and suspended, and the chloroplatinic acid solution was added dropwise thereto.
After 2 hours, an excess aqueous solution of sodium borohydride was added dropwise to reduce the platinum compound. It was filtered, washed with water and dried to prepare a 3% platinum carbon catalyst. When a catalytic activity test with dinitrotoluene was conducted in the same manner as in Example 1, the hydrogen absorption amount was 496 ml.

Comparative Example 5 A 3% platinum carbon catalyst was prepared in the same manner as in Example 3 except that the activated carbon of Comparative Example 1 was used. When a catalytic activity test with dinitrotoluene was conducted in the same manner as in Example 1, the hydrogen absorption amount was 446 ml.

[0038]

EFFECT OF THE INVENTION According to the present invention, the catalytic activity is high, the filtration separation is excellent, and the reaction efficiency and productivity are practically high.
Moreover, a reusable precious metal carbon catalyst is provided.

Claims (2)

[Claims] 1. A carrier comprising activated carbon particles and a noble metal catalyst component supported thereon, wherein the activated carbon particles have a cumulative volume particle size distribution of 90.
% Has a particle size of 60 μm or less, and the particle size distribution is such that the cumulative value of fine particles having a particle size of 3.3 μm or less is less than 40%. Noble metal carbon catalyst. 2. The noble metal carbon catalyst according to claim 1, wherein the noble metal catalyst component contains palladium or platinum.