JP2007130525A - Inclusion catalyst and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inclusion catalyst provided with a shell having a plurality of mesopores and a catalyst material included by the shell, and its manufacturing method. <P>SOLUTION: The inclusion catalyst is provided with the shell having a plurality of mesopores, and the catalyst material included in the shell. The inclusion catalyst provided with the shell having a plurality of mesopores and the catalyst material included in the shell has an average mesopore diameter of 2-30 nm. The manufacturing method of the inclusion catalyst is provided. The method comprises a step of carrying out a synthesis using a precursor of the catalyst material and a water-in-oil (W/O) emulsion containing raw materials of the shell to obtain the inclusion catalyst. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inclusion catalyst and a method for manufacturing the same, and more particularly, to an inclusion catalyst including a shell having a plurality of mesopores and a catalyst material included in the shell, and a method for manufacturing the same.

Conventionally, as a method for highly activating a catalyst, a method in which a metal particle size is reduced and highly dispersed on a metal oxide carrier is generally known.
On the other hand, since the affinity between the metal and the metal oxide carrier is not good, the particle size increases due to the aggregation of the metal during the firing, reduction or reaction of the catalyst, and the reaction activity and selectivity of the catalyst are reduced. It is also known that the problem of decline occurs.
As means for solving this problem, a method has been proposed in which ultrafine metal particles are included and immobilized with a metal oxide using a microemulsion (see Patent Document 1 and Non-Patent Document 1).
JP-A-7-246343 “Catalyst”, Catalysis Society of Japan, Vol. 39, no. 4, 1997, p268-273

  However, in the above conventional catalyst, since the metal particles are almost covered with the metal oxide, there is a problem that the active metal particles and the reactant are difficult to contact and the reaction activity as a catalyst is low. It was.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a package including a shell having a plurality of mesopores and a catalytic material enclosed by the shell. It is an object of the present invention to provide a catalytic catalyst and a production method thereof.

  As a result of intensive studies to achieve the above object, the present inventor conducted synthesis using a water-in-oil (W / O) emulsion containing a shell raw material and a precursor of a catalyst substance, and the like. The present inventors have found that the object can be achieved and have completed the present invention.

  That is, the clathrate catalyst of the present invention comprises a shell having a plurality of mesopores and a catalyst material clathrated in the shell.

  The clathrate catalyst production method of the present invention is a method for producing the clathrate catalyst of the present invention, wherein a water-in-oil (W / O) emulsion containing a shell material and a precursor of a catalyst material are provided. It is a method of obtaining a desired clathrate catalyst by performing synthesis.

  According to the present invention, since a clathrate catalyst is synthesized using a water-in-oil (W / O) emulsion containing a shell raw material and a precursor of a catalytic material, a shell having a plurality of mesopores is obtained. In addition, it is possible to provide a clathrate catalyst comprising a catalyst material clathrated in its shell and a method for producing the same.

Hereinafter, the inclusion catalyst of the present invention will be described in detail. In the present specification and claims, “%” represents mass percentage unless otherwise specified.
As described above, the inclusion catalyst of the present invention includes a shell having a plurality of mesopores and a catalyst material included in the shell.
Here, “mesopore” means a pore having a diameter of 2 to 50 nm as defined by IUPAC.

FIG. 1 conceptually shows the structure of the inclusion catalyst of the present invention. (A) is a perspective view, (b) is a partial cross-sectional view, and (c) is an enlarged view.
In this figure, the inclusion catalyst 10 has a shell 12 and a catalyst material 14, and the shell 12 encloses the catalyst material 14 in the hollow portion H. The shell 12 has a plurality of mesopores 12p distributed almost uniformly on the surface thereof. The mesopores 12p penetrate the shell 12 and communicate the hollow portion H with the outside.
The catalyst material 14 included in the shell 12 is usually attached to the inner wall of the shell 12, but the case where the catalyst material 14 is included in the hollow portion H apart from the inner wall is also included in the scope of the present invention.

In the inclusion catalyst of the present invention having such a structure, since the catalyst material 14 is included in the shell 12, for example, in the case where the catalyst material 12 is typical active metal particles, aggregation hardly occurs. The durability of the clathrate catalyst can be improved.
Further, the reactant can be transferred from the outside to the hollow portion H through the mesopores 12p, and the surface area of the catalyst substance 14 is increased, so that the reactant and the catalyst substance 14 can be easily contacted with each other. The reaction activity of the contact catalyst 10 can also be improved.
Furthermore, since the shell 12 having the mesopores 12p is provided, the selectivity of the reaction in the inclusion catalyst can be improved by the molecular sieve effect, and the pore diameter of the mesopores 12p can be controlled. It is also possible to control the reaction in the hollow portion H of the catalytic catalyst 10.

The clathrate catalyst of the present invention typically has a structure as shown in FIG. 1, but the mesopores 12p preferably have an average pore diameter of 2 to 30 nm, More preferably, it is 10 nm.
If the pore diameter is less than 2 nm, large molecules such as decalin do not enter and exit sufficiently, and it is difficult to effectively use the catalyst substance 14 included in the shell 12, and if it exceeds 30 nm, the mechanical strength is poor. This is likely to be sufficient, and the hollow portion H may be destroyed.

In the inclusion catalyst of the present invention, it is preferable that 80% or more of the total number of mesopores exist within the range of ± 1 nm of the average pore diameter.
Thus, in the clathrate catalyst of the present invention, since the mesopore diameter distribution is concentrated in a narrow range, the molecular sieve effect can be expected more. For example, the effect of introducing only small molecules into the hollow part and not introducing large molecules, or introducing linear hydrocarbons into the hollow part but not hydrocarbons having side chains, is utilized. Thus, it is possible to improve the selectivity of the catalytic reaction and the selectivity of the adsorbent.

Furthermore, the inclusion catalyst of the present invention preferably has an average particle size of 0.1 to 5 μm.
If the average particle diameter is less than 0.1 μm, the mechanical strength tends to be insufficient, and if it exceeds 5 μm, it is difficult to significantly improve the specific surface area.
In the inclusion catalyst of the present invention, the thickness of the shell is preferably 10 to 1000 nm, and more preferably 10 to 500 nm.
If the thickness is less than 10 nm, the mechanical strength tends to be insufficient, and the hollow portion tends to be broken. If the thickness exceeds 1000 nm, mesopores may not be formed.

The clad catalyst shell material of the present invention is not particularly limited as long as it satisfies the above-mentioned structure and characteristics, but silicon (Si), aluminum (Al), titanium (Ti) or zirconium (Zr). And metal oxides containing any of these mixed elements can be suitably used.
Thus, mechanical strength can be improved by forming a shell with a metal oxide. Moreover, since the said metal oxide can function also as a promoter, it becomes possible to improve reaction activity and selectivity.

The material of the catalyst material of the clathrate catalyst of the present invention is not particularly limited as long as it shows a reaction activity with respect to the reactant, and it is not particularly limited. For example, platinum (Pt), palladium (Pd), rhodium ( Rh), ruthenium (Ru), nickel (Ni), cobalt (Co), copper (Cu), silver (Ag), iron (Fe) and rhenium (Re), and those containing any mixed elements thereof The metal and metal oxide containing such an element can be used suitably.
Such a catalyst substance has a particularly remarkable effect on a catalytic reaction including a fuel reforming reaction and a CO selective oxidation reaction, and can improve reaction activity and durability.

Next, the manufacturing method of the clathrate catalyst of this invention is demonstrated in detail.
The clathrate catalyst production method of the present invention is a method for producing the clathrate catalyst of the present invention, wherein a water-in-oil emulsion (W / O emulsion) containing a shell material and a precursor of a catalyst substance are used. It is used to synthesize.
More specifically, for example, a water-in-oil salt of a catalytic metal that is a precursor of a catalytic substance, a water-in-oil in which a metal alkoxide or an organometallic halide containing an element constituting the shell that is a raw material of the shell is dissolved. A desired inclusion catalyst can be obtained by dissolving in an emulsion and synthesizing by hydrolysis or the like.
For example, when the catalyst metal is rhodium, rhodium nitrate can be used as the water-soluble salt. For example, when the shell is silica, a chlorosilane derivative containing silicon as an element constituting the shell is used. be able to.
Such W / O type emulsion is easy to control the emulsion size by adjusting the production conditions. Therefore, by using this and the precursor of the catalyst material, an inclusion catalyst having a particle size suitable for the purpose is produced. be able to.
Furthermore, by appropriately selecting the raw material of the shell and the precursor of the catalyst substance, it is possible to produce an inclusion catalyst corresponding to various purposes.

In the method for producing an inclusion catalyst of the present invention, it is desirable to add an organic template in the process of producing a water-in-oil emulsion.
By adding such an organic template, it is possible to synthesize hollow particles having mesopores of uniform diameter in the shell. It is also possible to control the pore diameter by changing the type of organic template.

  Such an organic template is not particularly limited as long as it is a template agent used in general mesoporous materials, but nonionic surfactants such as sorbitan acid monostearate and alkyltrimethylammonium Can be mentioned.

Furthermore, in the method for producing an inclusion catalyst of the present invention, it is preferable to carry out a step of hydrolyzing the organometallic halide in a water-in-oil emulsion.
By hydrolyzing the organometallic halide in a water-in-oil emulsion, a more stable spherical inclusion catalyst can be synthesized.

  Hereinafter, the present invention will be described in more detail with reference to some examples.

Example 1
A water-in-oil emulsion was prepared by mixing 100 ml of toluene, 1.5 ml of distilled water, 0.075 g of nitric acid Rh, 24 mmol of octyltrichlorosilane, and 0.24 mmol of sorbitan acid monostearate and stirring ultrasonically.
Next, 24 mmol of methyltrichlorosilane was added to the resulting emulsion, and the inclusion catalyst of this example was obtained by stirring, filtering, washing, drying and firing in air.

  Further, FIG. 2 shows the pore size distribution (mesopore size distribution) of the clathrate catalyst obtained in this example. A sharp peak with an average pore diameter of about 4 nm was observed, confirming the presence of uniform mesopores.

(Example 2)
100 ml of toluene, 1.5 ml of distilled water, 0.075 g of nitric acid Rh and 24 mmol of octyltrichlorosilane were mixed and ultrasonically stirred to prepare a water-in-oil emulsion.
Next, 24 mmol of methyltrichlorosilane was added to the resulting emulsion, and the inclusion catalyst of this example was obtained by stirring, filtering, washing, drying and firing in air.

  Further, FIG. 3 shows the pore size distribution (mesopore size distribution) of the clathrate catalyst obtained in this example. A plurality of pore diameter peaks were observed at 5 nm or less, and it was confirmed that most of the pores were 1 nm or less and no uniform mesopores were present.

(Example 3)
A water-in-oil emulsion was prepared by mixing 100 ml of toluene, 1.5 ml of distilled water, 0.075 g of dinitrodiamine Pt, 24 mmol of octyltrichlorosilane, and 0.24 mmol of sorbitan acid monostearate, and stirring them ultrasonically.
Next, 24 mmol of methyltrichlorosilane was added to the resulting emulsion, and the inclusion catalyst of this example was obtained by stirring, filtering, washing, drying and firing in air.

Example 4
A water-in-oil emulsion was prepared by mixing 100 ml of toluene, 1.5 ml of distilled water, 0.075 g of dinitrodiamine Pt, and 24 mmol of octyltrichlorosilane, and stirring them ultrasonically.
Next, 24 mmol of methyltrichlorosilane was added to the produced emulsion, and the clathrate catalyst of this example was obtained by stirring, filtering, washing, drying and firing in air.

[Performance evaluation]
(Ethanol steam reforming characteristics evaluation)
The clathrate catalysts obtained in Examples 1 and 2 were sized to 32-42 mesh, and 0.3 g of this catalyst was evaluated for ethanol water vapor reaction characteristics using a fixed bed normal pressure flow reactor.
The partial pressure of ethanol contained in the reaction gas was 1.7 kPa, the partial pressure of water was 7.2 kPa, and helium was supplied as a carrier gas to the catalyst at a flow rate of 40 ml / min. The catalyst temperature was 400 ° C. The obtained results (ethanol conversion and product composition) are shown in Table 1. The “C2 product” in Table 1 is a product having 2 carbon atoms, and typically includes ethylene, acetaldehyde, unreacted ethanol, and the like.

As shown in Table 1, it can be seen that Example 1 has improved reaction activity and increased ethanol conversion compared to Example 2 in which no uniform mesopores exist. Moreover, _{H 2} and C1 products _{(CO 2, CO, CH 4} ) production ratio also increased, and it is understood that selectivity is improved.

(Characteristic evaluation of CO selective oxidation reaction)
The clathrate catalyst obtained in Examples 3 and 4 above was sized to 32-42 mesh, and 0.3 g of this catalyst was subjected to CO selective acid reaction characteristics at each catalyst temperature using a fixed bed normal pressure flow reactor. Evaluated.
The composition of the gas used in the _{evaluation, CO: 0.5vol%, H 2} : 30vol%, CO 2: 15vol%, H 2 O: 27vol%, O 2: 0.5vol%, N 2: 27vol% And was supplied to the catalyst at a flow rate of 50 ml / min. The obtained results (CO conversion) are shown in Table 2.

  As shown in Table 2, it can be seen that Example 3 has improved reaction activity and selectivity and increased CO conversion compared to Example 4 in which no uniform mesopores exist.

Although the present invention has been described in detail with reference to some examples, the present invention is not limited to these examples, and various modifications can be made within the scope of the gist of the present invention.
For example, in the above embodiment, an ethanol steam reforming catalyst or a CO selective oxidation catalyst using a model gas typical as a fuel reforming gas has been described as an example. The inclusion catalyst of the present invention is not limited to the quality, and it can be applied to fields where the excellent durability and selectivity of such a catalyst are effectively exhibited. It can be used as an exhaust gas purification catalyst for fuel, an electrode catalyst for fuel cells, and a catalyst in heterogeneous chemical reactions of petroleum refining and organic synthesis.

It is explanatory drawing which shows notionally the structure of the clathrate catalyst of this invention. 2 is a graph showing the pore size distribution of the clathrate catalyst obtained in Example 1. FIG. 3 is a graph showing the pore size distribution of an inclusion catalyst obtained in Example 2. FIG.

Explanation of symbols

H hollow part 10 inclusion catalyst 12 shell 12p mesopore 14 catalyst substance

Claims (10)

  An inclusion catalyst comprising: a shell having a plurality of mesopores; and a catalyst material included in the shell.   The inclusion catalyst according to claim 1, wherein the mesopores have an average pore diameter of 2 to 30 nm.   The inclusion catalyst according to claim 2, wherein 80% or more of the total number of mesopores is included within a range of ± 1 nm of the average pore diameter.   The inclusion catalyst according to any one of claims 1 to 3, wherein an average particle diameter is 0.1 to 5 µm.   The clathrate catalyst according to any one of claims 1 to 4, wherein the shell has a thickness of 10 to 1000 nm.   6. The clathrate according to claim 1, wherein the shell is made of a metal oxide containing at least one element selected from the group consisting of silicon, aluminum, titanium and zirconium. catalyst.   The catalyst material contains at least one element selected from the group consisting of platinum, palladium, rhodium, ruthenium, nickel, cobalt, copper, silver, iron and rhenium. The inclusion catalyst according to one item.   A clath characterized in that, in the production of the clathrate catalyst according to any one of claims 1 to 7, a synthesis is carried out using a water-in-oil emulsion containing a shell material and a precursor of a catalyst substance. A method for producing a catalytic catalyst.   The method for producing an inclusion catalyst according to claim 8, wherein an organic template is added in the process of forming the water-in-oil emulsion.   The method for producing an inclusion catalyst according to claim 8 or 9, comprising a step of hydrolyzing the organometallic halide in the water-in-oil emulsion.

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