JPS5818147B2 - Manufacturing method of rhodium catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a rhodium catalyst, and more particularly to a method for producing a rhodium catalyst in which rhodium is supported on the particle surface of a silica-based or titania-based carrier or in a layer near the particle surface.

Catalysts in which noble metals such as hexagonal gold, palladium, and rhodium are supported on porous inorganic carriers are widely used industrially as catalysts for various reactions.

Incidentally, in many reactions, most of the reaction takes place on the outer surface or surface layer of the catalyst particles, and the noble metals inside the catalyst particles often do not participate much in the reaction.

Therefore, it is not economical to impregnate the interior of the carrier particles with expensive noble metals, and it is therefore desirable to support the noble metals only on the surface of the carrier particles or in a layer near the surface.

For example, in Japanese Patent Publication No. 47-35670, alkali carbonate is added to an acidic aqueous solution of a palladium salt to adjust the pH of the solution to a range of 2.8 to 4.8, and then added to an inorganic porous carrier and added to the surface of the carrier. It is disclosed that a palladium catalyst is produced in which palladium is supported on the surface of the carrier particles by impregnating the catalyst with a catalyst and further carrying out a ring treatment. It is described that the catalyst has higher activity than a catalyst in which palladium is almost uniformly dispersed and supported inside the carrier particles.

1 Japanese Patent Publication No. 48-10135 also discloses that a suitable ring metal (for example, palladium metal) is precipitated on a carrier in a weight ratio of 0.001 to 0.2, and then a necessary amount of palladium is deposited on the carrier. It has been disclosed that vinyl acetate is produced using a catalyst on which palladium has a modulus of 90 or more attached to the surface of a carrier obtained by attaching a catalyst component, and by using such a catalyst, palladium can be deposited deep into the porous carrier. It is stated that the reaction results are far superior to those of impregnated catalysts.

1 In this way, by using a supported catalyst in which a noble metal catalyst component such as palladium is substantially supported only on the surface layer of porous carrier particles or a layer near it, the catalyst component can reach the inside or deep part of the catalyst. It is already known that the catalyst efficiency 1 (e.g., yield per unit weight of catalyst) is significantly higher than that of impregnated catalysts, and the cost of the catalyst can be significantly reduced because it does not contain catalyst components inside the carrier that do not substantially function effectively. It is being

By the way, catalysts made of rhodium supported on porous carriers are also useful for the synthesis of oxygenated compounds such as ethylene glycol, ethanol, acetaldehyde, acetic acid, etc.
Purification of automobile exhaust gas, various hydrogenation reactions such as selective hydrogenation of carbonyl groups such as aldehydes and ketones, nuclear hydrogenation of aromatic compounds, hydrogenation of unsaturated bonds such as olefins, acetylenes, nitriles, etc. Used as a catalyst in reactions.

Rhodium is a precious metal mainly extracted from platinum ore. Therefore, like platinum and palladium, using a supported catalyst in which rhodium is supported only on the surface of the carrier particle or a layer near it improves catalytic efficiency. It is also highly desirable economically.

However, in the case of a rhodium catalyst in which rhodium is supported on a silica-based or titania-based support, it is of course possible to support rhodium on a porous support according to a conventional general catalyst preparation method, and also to use palladium or platinum as mentioned above. Even when using the method used to support rhodium on the surface of porous carrier particles or a layer near the same, it was not possible to substantially support rhodium only on the surface of the carrier particle or a layer near the same.

Therefore, in view of the current state of the prior art, the present inventors
The present invention was achieved as a result of intensive research into a method for producing a catalyst in which rhodium is supported only on the surface of porous carrier particles or a layer in the vicinity thereof.

In the method for producing a rhodium catalyst according to the present invention, in producing a rhodium catalyst in which rhodium is supported on a silica-based or titania-based carrier, a silica-based or titania-based carrier is
Immerse in an aqueous solution of a water-soluble rhodium salt with an acid added to adjust the pH to 1 or less. Then, use an alkali of an equivalent amount or more necessary for neutralizing the acid impregnated in the carrier and converting the rhodium salt to rhodium hydroxide. immersed in an alkaline aqueous solution containing
The method is characterized in that the carrier is dried and then subjected to a ring treatment to produce a catalyst in which rhodium is unevenly distributed on the surface of the carrier particles or in a layer near the carrier particles.

As the heather soluble rhodium salt used in the method of the present invention, any rhodium salt conventionally used in the preparation of rhodium catalysts can be used.

Typical examples of such rhodium salts include, for example.

Examples include rhodium chloride, rhodium bromide, rhodium iodide, rhodium nitrate, rhodium sulfate, and rhodium acetate.

According to the method of the present invention, these rhodium salts are first dissolved in water, and a mineral acid such as hydrochloric acid, nitric acid, or sulfuric acid is added thereto to adjust the pH of the aqueous solution to 1 or less.

However, if the acid concentration is too high, the carrier itself may be attacked and the mechanical strength may be reduced, so it is desirable to keep the acid concentration at a factor of 10 or less.

) Next, a silica-based or titania-based carrier is immersed in this aqueous solution by a general method, and the rhodium salt aqueous solution is impregnated into the pores of the porous carrier.

The silica-based carrier or titania-based carrier may be a carrier consisting of a single component of silica or titania, or a mixture or composite oxide containing these as the main component).

In this case, examples of other components include alumina, magnesia, thoria, and zirconia.

If necessary, the carrier particles impregnated with an aqueous solution of rhodium salt can be dried in air after draining, for example, with caustic soda, caustic potash, etc.
Immerse in an alkaline aqueous solution containing a suitable alkali such as soda carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, calcium hydroxide, etc.

The amount of alkali used at this time is 1. The amount of acid impregnated into the carrier must be equal to or greater than the equivalent required for converting the rhodium salt into rhodium hydroxide; on the other hand, if the amount is too much, some of the rhodium impregnated into the carrier may be dissolved in the alkaline aqueous solution. Since there is a risk of elution, the theoretical amount is usually 1.0
It is desirable to use an amount of alkali of ~3.0 times, preferably 1.2 to 2.0 degrees of eccentricity.

After being immersed in an alkali, the carrier is dried and subjected to a ring treatment according to a conventional method.

For example, carrier particles taken out from an aqueous alkaline solution are drained, air-dried, and further dried in a dryer if necessary.

In this case, rapid drying at high temperatures promotes agglomeration and crystallization of the impregnated rhodium particles and prevents the rhodium from being uniformly dispersed as fine particles in the final catalyst. It is desirable to dry relatively gently at the following temperatures.

The carrier particles dried in this way are usually subjected to a cyclic treatment at a temperature of 50 to 500°C under a hydrogen stream, so that the surface of the carrier particles or its vicinity can be removed, for example, as shown in FIGS. 1 and 2. It is possible to obtain the desired rhodium catalyst in which supported rhodium is unevenly distributed in the layer.

The method for treating the ring element is not limited to the above-mentioned method, and various methods commonly used for preparing metal catalysts may be used, such as treating the ring element with hydrazine, formalin, methanol vapor, etc. I can do it.

As explained above, the feature of the method of the present invention is that after adjusting the pH of a water-soluble rhodium salt aqueous solution to 1 or less, a silica-based or titania-based carrier is immersed to impregnate it with the rhodium salt aqueous solution, and before carrying out the ring-forming treatment. It consists in alkali treatment.

If the pH of the rhodium salt aqueous solution in which the silica-based or titania-based support is immersed exceeds 1, even if an alkali treatment is performed, a catalyst with a structure in which metallic rhodium is appropriately unevenly distributed on the surface of the support particles or in a layer near it cannot be obtained. Otherwise, the object of the present invention cannot be achieved.

On the other hand, even if the carrier is immersed in an aqueous rhodium salt solution having a pH of below pH 1, the object of the present invention cannot be achieved even if the alkali treatment is not performed before the ring treatment.

By using a catalyst in which rhodium is substantially supported only on the surface or a layer near the surface of the carrier particles produced according to the present invention, the catalytic efficiency (e.g., the desired product per unit catalyst weight) in the various reactions using the rhodium catalyst described above can be improved. This is extremely advantageous in practice, as the yield (yield of

The case in which rhodium is supported on a silica-based or titania-based support has been described in detail above, but it goes without saying that the method of the present invention can also be applied when supporting other components as co-catalysts in addition to rhodium. .

For example, alkaline earth metals such as calcium, magnesium, barium, noble metals such as platinum, palladium, iridium, ruthenium, gold, iron, nickel, cobalt, cerium, manganese, etc. After supporting a co-catalyst component such as a metal or a salt, rhodium can be supported on the surface of the carrier particles or a layer in the vicinity thereof as described above, or rhodium can be supported on the surface of the carrier particles or in the vicinity thereof as described above. After rhodium is supported on the layer, for example, a co-catalyst component can be supported thereon in accordance with a conventional method.

Alternatively, in some cases, a solution obtained by adding a co-catalyst component to an aqueous rhodium salt solution may be used as the impregnating solution.

Hereinafter, the present invention will be explained in more detail according to examples.
It goes without saying that the technical scope of the present invention is not limited to these examples.

Example 1 Metallic rhodium was supported on a silica carrier having a bulk density of 0.5733 kg/l, a diameter of approximately 5 mmφ, a specific surface area of 150 ml/g, and a pore volume of 0.55 ml/g in the following manner.

RhCI 3" 3H20 aqueous solution (metallic rhodium content in the liquid: 15.68 g/A') in a 100ml beaker 2
0.7ml! and add 1.3 m of 12N concentrated hydrochloric acid to it.
After adjusting the pH to 0.3, pure water was added to make the liquid volume 38.5 ml.

Next, 100 ml of the above-mentioned silica carrier was added to the RhCl3 aqueous solution prepared in this manner and thoroughly stirred to impregnate the RhCl3 aqueous solution into the carrier.

The rhodium-impregnated silica carrier was taken out from the beaker and air-dried, followed by 80 ml of a 0.4N aqueous sodium hydroxide solution (equivalent to about 1.3 times the total amount of rhodium chloride and hydrochloric acid).
It was placed in a container and left to stand for 24 hours.

After standing still, drain the water, air dry, and then heat in a drying mold at 110℃.
for 1 hour at 150°C and 2 hours at 150°C.

The thus dried rhodium-impregnated silica carrier was subjected to ring reduction at 300° C. under hydrogen flow to obtain a catalyst in which metallic rhodium was supported on the silica carrier.

The metallic rhodium content in the catalyst was approximately 0.5% by weight.

When the cross section of the obtained catalyst was observed with an optical microscope (magnification: 5x), it was found that catalyst particles 1 were observed as schematically shown in Figure 1.
It was confirmed that metal rhodium was unevenly distributed in the surface layer 11 of 0, and the amount of metal rhodium present in the interior 12 was small.

On the other hand, the distribution of metallic rhodium in the cross section of this catalyst was measured using EPMA (
Electron Probe Micro Analysis
As shown in FIG. 2, most of the metal rhodium was unevenly distributed in a layer 0.4 mm deep from the surface (a layer about 16% of the particle radius from the surface).

Comparative Example l RhCl3.3H20 aqueous solution (metallic rhodium content in the liquid: 15.68 g/l) 20.7 yd was placed in a 100 ml beaker, and pure water was added to it to prepare Rh at pH=1.2.
A Cl3 aqueous solution was prepared.

In this liquid, the silica carrier 1007717 used in Example 1 was added.
1! was added and thoroughly stirred to impregnate the RhCl3 aqueous solution into the carrier.

The rhodium-impregnated silica carrier thus obtained was calcined and cyclized in the same manner as in Example 1, except that it was not treated with an alkali using an aqueous solution of caustic soda. Obtained.

The metallic rhodium content in the catalyst was approximately 0.5% by weight.

When the cross section of the obtained catalyst was observed using an optical microscope (magnification: 5x) in the same manner as in Example 1, it was found that metal rhodium was distributed over the entire cross section of the catalyst particles 13, as shown in FIG. Further, the results of EPMA analysis in the same manner as in Example 1 are shown in FIG.

Example 2 100 ml of the silica carrier used in Example 1 was mixed with MgC12
・Prepare a carrier containing magnesium by immersing it in 36.7 ml of an aqueous solution containing 75 g of 6H2010, air-dry it, dry it at 150°C in a drying mold, and dry it at 900°C in a Matsufuru furnace for 30 minutes.
Baked for 0 minutes.

A metallic rhodium-supported catalyst was prepared in the same manner as in Example 1 using the carrier thus obtained.

The metallic rhodium content in the obtained catalyst was approximately 0.5% by weight, and when the metallic rhodium distribution in the cross section of the catalyst was investigated in the same manner as in Example 1, results similar to those shown in Figs. 1 and 2 were obtained. Example 3 In place of the silica carrier, commercially available spherical titania (TiO□: carrier (manufactured by Sakai Chemical Co., Ltd., particle size 4 to 6 mmφ, Bulk density 1.1kg/
A', surface area s o m/g) was used in the same manner as in Example 1, except that approximately 0.0.
A catalyst supporting 5 weight fractions was prepared.

When the distribution of metallic rhodium in the obtained catalyst was investigated in the same manner as in Example 1, results similar to those shown in Figures 1 and 2 were obtained, indicating that most of the rhodium was supported on the surface layer of the carrier particles. I confirmed that it was.

Comparative Example 2 A catalyst in which about 0.5% by weight of metal rhodium was supported on a titania support was prepared in the same manner as in Comparative Example 1, except that the commercially available spherical titania support used in Example 3 was used instead of the silica support. .

The distribution of metallic rhodium in the obtained catalyst was investigated in the same manner as in Example 1, and it was found that metallic rhodium was found in Figures 3 and 4.
Similar to the results shown in the figure, it was almost uniformly distributed inside the carrier.

Example 4 A catalyst in which about 0.5% by weight of metallic rhodium was supported on a silica carrier was prepared in the same manner as in Example 1 except that +-59 silica manufactured by Davison was used as the silica carrier. When the distribution of metallic rhodium was investigated in the same manner as in Example 1, results similar to those shown in Figures 1 and 2 were obtained, indicating that most of the rhodium was supported on the surface layer of the carrier particles. confirmed.

Comparative Example 3 A catalyst in which about 0.5% by weight of metal rhodium was supported on a silica carrier was prepared in the same manner as in Comparative Example 1, except that ≠59 silica manufactured by Davison was used as the silica carrier.

When the distribution state of metallic rhodium in the obtained catalyst was investigated in the same manner as in Example 1, it was found that metallic rhodium was almost uniformly distributed inside the carrier, similar to the results shown in FIGS. 3 and 4. Ta.

Comparative Example 4 20.7 ml of RhCl3.3H20 aqueous solution (metallic rhodium content in the liquid: 15.6 g/l) was mixed with 10011
11, add pure water to it and adjust the pH to 1.
A RhCl3 aqueous solution of No. 2 was prepared.

100 ml of the silica carrier used in Example 1 was added to this liquid and thoroughly stirred to impregnate the aqueous RhCl3 solution into the carrier.

The rhodium-impregnated silica carrier thus obtained was treated with an alkali using a caustic soda aqueous solution in the same manner as in Example 1, and then calcined and cyclized to support approximately 0.5% by weight of metal rhodium on the silica carrier. A catalyst was prepared.

When the distribution of metallic rhodium in the obtained catalyst was investigated in the same manner as in Example 1, metallic rhodium was found to be almost uniformly distributed inside the carrier, similar to the results shown in FIGS. 3 and 4. .

Comparative Example 5 RhC13・3H20 aqueous solution (metallic rhodium content in the liquid: 15.6 g/l!) 20.7 rul was added to 100 m/l
! into a beaker, add concentrated hydrochloric acid and pure water, and
A RhCl3 aqueous solution with H=0.3 was prepared.

The silica carrier 100 used in Example 1 was added to this solution and thoroughly stirred to impregnate the RhCl3 aqueous solution into the carrier.

Except that the rhodium-impregnated silica support thus obtained was not subjected to alkali treatment using a caustic soda aqueous solution.
In the same manner as in Example 1, a catalyst in which approximately 0.5% by weight of metallic rhodium was supported on a silica carrier was prepared by calcination and ring removal.

When the distribution of metallic rhodium in the obtained catalyst was investigated in the same manner as in Example 1, it was found that metallic rhodium was uniformly distributed inside the carrier, similar to the results shown in Figures 3 and 4. Ta.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing the results of observing the distribution state of metal rhodium in the catalyst obtained in Example 1 using an optical microscope. FIG. 2 is a graph showing the results of EPMA analysis of the distribution state of metal rhodium in the catalyst in Example 1. FIG. 3 is a cross-sectional view schematically showing the results of observing the distribution state of metal rhodium in the catalyst obtained in Comparative Example 1 using an optical microscope. FIG. 4 is a graph showing the results of EPMA analysis of the distribution state of metal rhodium in the catalyst obtained in Comparative Example 1. 10.13...Catalyst, 11...Metal rhodium unevenly distributed layer.

Claims (1)

[Claims] 1. When producing a rhodium catalyst in which rhodium is supported on a silica-based or titania-based support, the silica-based or titania-based support is immersed in an aqueous solution of a water-soluble rhodium salt whose pH is adjusted to 1 or less by adding an acid to the aqueous solution. The carrier is then immersed in an alkaline aqueous solution containing an alkali equivalent or more than that necessary for neutralizing the acid impregnated in the carrier and converting the rhodium salt into rhodium hydroxide, and after drying, the carrier is subjected to a ring-forming treatment. A method for producing a rhodium catalyst, characterized by producing a catalyst in which rhodium is unevenly distributed on the surface of particles or in a layer near the particle surface.