JP2009029684A - Method for producing mesoporous silica carrying rhodium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing mesoporous silica carrying rhodium uniformly on its pore structure through a reaction under relatively mild conditions. <P>SOLUTION: Mesoporous silica carrying rhodium, in which rhodium is carried on mesoporous silica having a mesopore structure with 10-100 Å mean pore size and ≥500 m<SP>2</SP>/g nitrogen adsorption specific surface area measured by BET method, is obtained by conducting a first process for preparing activated silica by bringing a sodium silicate aqueous solution into contact with a cation exchange resin, then a second process for subjecting the activated silica, a cationic surfactant and a rhodium precursor to hydrothermal reaction preferably at a temperature exceeding 100°C but not higher than 200°C to produce a composite of rhodium-containing silica and the cationic surfactant, a third process for firing the composite, in this order. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing rhodium-supported mesoporous silica. Specifically, rhodium is uniformly supported on a porous structure of mesoporous silica. For example, the reduction of nitrogen oxides by carbon monoxide in the presence of excess oxygen. The present invention relates to a method for producing rhodium-supported mesoporous silica useful as a catalyst having high activity.

  Conventionally, as a method for producing silica having a porous structure called mesoporous silica, the following two methods are typically known depending on the type of silica source used. The first method uses a layered silicate as a starting silica source. For example, a complex of kanemite and alkyltrimethylammonium, which is one of layered silicates, is synthesized, calcined, By removing organic substances, mesoporous silica is obtained (see Non-Patent Document 1). However, according to this method, it is necessary to first synthesize kanemite as a starting material, and since a large amount of Na is present in the reaction system, the Na component has a silica structure during firing of the composite. There is a problem that the surface area of the porous body is reduced by breaking. Further, Na is used as a catalyst poison in a catalyst or the like, and causes a decrease in catalyst activity.

  The second method uses various silica sources such as amorphous silica powder and alkaline silicate aqueous solution. For example, a mixture of precipitated silica and tetramethylammonium silicate aqueous solution is reacted with alkyltrimethylammonium at 150 ° C. In the same manner as described above, this was baked to remove organic substances to obtain mesoporous silica, and sodium silicate was neutralized with sulfuric acid to obtain silica gel, which was combined with alkyltrimethylammonium and 100 ° C. The mixture is reacted for 6 days to form a composite, which is baked to remove organic substances to obtain mesoporous silica (see Non-Patent Document 2).

  However, even in this method, when amorphous silica powder is used as a raw material, heating at 100 ° C. or higher and a long-time reaction in an autoclave are required. Therefore, energy costs increase, and tetramethylammonium silicate is an alkali. Since it is an alkali silicate aqueous solution that does not contain a metal, it is a preferable reaction material, but it is expensive, and since all the tetramethylammonium in the raw material is contained in the wastewater, industrial wastewater treatment is required. It is hard to say that it is an advantageous method. In the method of obtaining silica gel by neutralizing sodium silicate with sulfuric acid, a long aging operation of 6 days at 100 ° C. is required, and the presence of a large amount of Na in the reaction system reduces the heat resistance of silica. There is a problem such as.

  In addition to the above, various silica sources such as a commercially available silica sol can be reacted with alkyltrimethylammonium in the presence of sodium hydroxide at 95 ° C. for 7 to 20 days, or at 150 ° C. for 2 days to obtain mesoporous silica. A synthesis method is known (see Patent Document 1). However, this method also has problems such as that the reaction takes a long time, a large amount of Na component remains, and the specific surface area of the obtained mesoporous silica is relatively small.

  Therefore, in order to solve these problems, an active silica is prepared by bringing a sodium silicate aqueous solution into contact with a cation exchange resin, and this active silica and a cationic surfactant are mixed and reacted in an alkaline region. There has been proposed a method in which a composite of a surfactant is formed and then the composite is fired to obtain mesoporous silica (see Patent Document 2). According to this method, unlike the above-described method, mesoporous silica having a high specific surface area and a low Na content can be obtained without requiring a reaction under high temperature and high pressure.

  On the other hand, mesoporous structure catalysts such as mesoporous silica have a large pore diameter compared to crystalline structure catalysts such as zeolite, so that the diffusion rate of reactants in the pores is large, resulting in a high reaction rate. Therefore, use in various applications has been studied (see, for example, Patent Documents 3 and 4).

  However, mesoporous silica, like zeolite, does not have an ion exchange capability, so in order to support catalyst components such as noble metals on mesoporous silica, first, the catalyst precursor aqueous solution is impregnated in the mesoporous pores. Then, the method of converting the precursor into a noble metal by heat reduction or the like must be used. Therefore, in the above method, a pressure impregnation method in which mesoporous silica is impregnated with an aqueous catalyst precursor solution under reduced pressure has been proposed in order to support the catalyst component as uniformly as possible in the mesoporous pores (see Patent Document 5). ).

According to such a method, although the catalyst precursor aqueous solution is impregnated relatively uniformly into the mesoporous pores during impregnation, the catalyst precursor aqueous solution moves to the surface layer of the mesoporous pores as the drying proceeds. The catalyst component cannot be uniformly supported in the mesoporous pores, and the catalyst component is aggregated and supported in the vicinity of the surface layer of the pores of the mesoporous silica. There are various problems.
Japanese National Patent Publication No. 5-503499 JP-A-8-34607 JP 2003-320245 A JP 2004-148166 A JP 2003-320245 A T. Yanagisawa., Bull. Chem. Soc. Jpn., Vol. 63, 988-992 (1990) JS Beck et al., J. Am. Chem. Soc., Vol. 114, 10834-10843 (1992)

  Thus, conventionally, an effective method for uniformly supporting a catalyst component, particularly a noble metal, on the pore structure of mesoporous silica has not been known. Therefore, the present inventors paid attention to the above-described method using activated silica, and as a result of earnestly researching the results, a comparison of reacting activated silica, a cationic surfactant, and a rhodium precursor at a predetermined temperature in an alkaline region. It has been found that rhodium-supported mesoporous silica in which rhodium is uniformly supported on mesoporous silica having a large specific surface area can be easily obtained by reaction under mild and practical conditions. is there. Accordingly, an object of the present invention is to provide a method for producing rhodium-supported mesoporous silica in which rhodium is uniformly supported on mesoporous silica having a large specific surface area by a reaction under relatively mild and practical conditions. .

According to the present invention, a first step of preparing an active silica by bringing a sodium silicate aqueous solution into contact with a cation exchange resin, and then the active silica, the cationic surfactant, and the rhodium precursor at 50 to 200 ° C. in an alkaline region. The second step of producing a complex of silica containing rhodium and a cationic surfactant by reacting at a temperature in the range and the third step of firing the complex are carried out in this order, and the average pore diameter is There is provided a method for producing rhodium-supported mesoporous silica having mesoporous structure of 10 to 100 angstroms and rhodium supported on mesoporous silica having a nitrogen adsorption specific surface area of 500 m ² / g or more by BET method.

According to such a method of the present invention, rhodium is uniform in a porous structure having a mesopore structure having an average pore diameter in the range of 10 to 100 angstroms and a nitrogen adsorption specific surface area of 500 m ² / g or more. The rhodium-supported mesoporous silica supported on the catalyst can be obtained. Such rhodium-supported mesoporous silica is superior in catalytic activity to, for example, those obtained by supporting rhodium on mesoporous silica by a conventional impregnation method.

The method for producing rhodium-supported mesoporous silica according to the present invention comprises a first step of preparing an active silica by bringing a sodium silicate aqueous solution into contact with a cation exchange resin, and then the active silica, the cationic surfactant and the rhodium precursor in the alkaline region. The second step for producing a complex of rhodium-containing silica and a cationic surfactant by the reaction at a temperature in the range of 50 to 200 ° C. and the third step for firing the complex are performed in this order. And a rhodium-supported mesoporous silica having a mesoporous structure with an average pore size of 10 to 100 angstroms and a rhodium supported on mesoporous silica having a nitrogen adsorption specific surface area of 500 m ² / g or more by the BET method. Can do.

In the method of the present invention, the active silica used as a starting material can be obtained as a sol by bringing sodium silicate into contact with a hydrogen ion cation exchange resin in the first step. As sodium silicate, one having a SiO ₂ / Na ₂ O molar ratio of 2 to 4 is usually used, but No. 3 sodium silicate has a relatively low Na content and is inexpensive, and is therefore advantageous in the present invention. Used. Examples of the hydrogen ion cation exchange resin include sulfonated polystyrene divinylbenzene-based strongly acidic cation exchange resin (“Amberlite IR-120B” manufactured by Rohm & Haas) and carboxylated polyacrylic acid-based weakly acidic cation. Exchange resin ("Amberlite IRC-76" manufactured by Rohm & Haas) is preferably used.

Thus, by bringing sodium silicate into contact with the hydrogen ion cation exchange resin, substantially all Na ions in the sodium silicate can be removed, and active silica can be obtained as a sol. However, this active silica sol is composed of a silicic acid oligomer (in many cases) having a siloxane bond (Si-O-Si) generated by partial condensation of silicic acid together with many silanol groups (Si-OH). Therefore, unlike a completely grown stable sol particle, the degree of polymerization is 11 or less), and is in an unstable sol form with many silanol groups. The active silica sol has a particle size of 3 nm or less and a specific surface area of 2000 m ² / g or more according to the measurement of the amount of adsorbed NaOH by the Sears method. Moreover, NaOH content in active silica sol is 0.01 weight% or less, sol has acidity, and pH is the range of 2-5 normally.

  Next, using this active silica prepared in the first step, in the second step, a complex of rhodium-supported silica and a cationic surfactant is prepared. That is, active silica, a cationic surfactant and a water-soluble rhodium precursor such as rhodium nitrate are reacted at a predetermined temperature in an alkaline region to form a complex of silica containing rhodium and a cationic surfactant. If this is filtered, washed and dried, the composite is obtained as a powder.

  More specifically, if necessary, an alkaline agent for pH adjustment is added to the cationic surfactant to prepare an alkaline aqueous solution of the cationic surfactant, and the aqueous solution of the rhodium precursor is added thereto, followed by thorough stirring. After mixing, the active silica is added dropwise to the aqueous solution with stirring to react the active silica, the cationic surfactant, and the rhodium precursor in a predetermined alkaline region. This is separated, washed and dried and recovered as a powder. The rhodium precursor is usually used in a range in which the amount of rhodium supported on mesoporous silica is 0.1 to 5% by weight.

As the cationic surfactant, a quaternary ammonium compound or an alkylamine hydrohalide is preferably used. The quaternary ammonium compound is preferably a compound of the general formula (I)
_{[R n (CH 3) 4} -n N] + X - (I)
(In the formula, R represents a long-chain alkyl group, X represents a halogen atom or a hydroxyl group, and n is an integer of 1 to 3.)
A quaternary ammonium halide or a quaternary ammonium hydroxide.

  In the quaternary ammonium compound represented by the general formula (I), the long chain alkyl group R preferably has 8 to 24 carbon atoms. When the carbon number is 25 or more, it is insoluble in water and difficult to handle. N is preferably 1 or 2, and particularly preferably 1. Furthermore, when X is a halogen atom, the halogen atom is preferably a chlorine atom or a bromine atom.

Therefore, according to the present invention, the quaternary ammonium compound represented by the general formula (I) is preferably represented by the general formula (II).
[R (CH ₃ ) ₃ N] ⁺ X ⁻ (II)
(In the formula, R and X are the same as described above.)
Or an alkyltrimethylammonium hydroxide represented by the formula:

  Specific examples of the alkyltrimethylammonium halide include octyltrimethylammonium chloride, octyltrimethylammonium bromide, decyltrimethylammonium chloride, decyltrimethylammonium bromide, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexa Examples include decyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.

  Specific examples of the alkyltrimethylammonium hydroxide include octyltrimethylammonium hydroxide, decyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide, hexadecyltrimethylammonium hydroxide, and octadecyltrimethylammonium hydroxide.

  These quaternary ammonium compounds are used alone or in combination of two or more.

The alkylamine hydrohalide is preferably a compound of the general formula (III)
[RNH ₃ ] ⁺ X ⁻ (III)
(In the formula, R and X are the same as described above.)
It is represented by

  Specific examples of such alkylamine hydrohalates include, for example, trimethylamine hydrochloride, triethylamine hydrochloride, triethylamine hydrochloride hydrofluoride, 2-chloroethylamine hydrochloride, 3-chloropropyl. Examples thereof include amine hydrochloride, methylamine hydrobromide, docosylamine hydrobromide, propylamine hydrobromide, and the like.

  In the present invention, as the cationic surfactant, the quaternary ammonium compound has higher basicity than alkylamine hydrohalide, is excellent in reactivity, and gives mesoporous silica having a uniform pore diameter. A quaternary ammonium compound is preferably used.

  As the alkaline agent for adjusting the pH, sodium hydroxide, sodium silicate, sodium aluminate, tetraethylammonium hydroxide, quaternary ammonium silicate, organic amine, and the like are used. In particular, tetraethylammonium hydroxide is preferably used. . However, in the present invention, the alkaline agent for pH adjustment is not limited to those exemplified above.

According to the present invention, the reaction of the cationic surfactant, activated silica and rhodium precursor under the alkaline region is preferably carried out by the following method.
(1) If necessary, an alkaline agent is added to an aqueous solution of a cationic surfactant to prepare an alkaline aqueous solution of the cationic surfactant.
(2) The rhodium precursor aqueous solution is added to the alkaline aqueous solution of the cationic surfactant and sufficiently stirred.
(3) Next, active silica is added dropwise to the aqueous solution prepared in the above (2) under stirring to prepare a mixture in a predetermined alkaline region.
(4) The mixture obtained in the above (3) is reacted at a temperature in the range of 50 to 200 ° C. while stirring.

  However, the reaction between the cationic surfactant, the active silica, and the rhodium precursor in the alkaline region can be performed by the above-described method as long as the rhodium precursor and the active silica do not gel and a uniform composite is obtained. It is not limited.

  According to the present invention, the alkaline range suitable for obtaining a complex composed of silica carrying rhodium and a cationic surfactant by the above reaction has a pH value of 8-12. In this pH range, water-based silica molecules are smoothly cleaved, polymerized, and reconstructed into a homogeneous structure. However, when the pH exceeds 12, it is not preferable because the solubility of silica increases.

  In the present invention, the reaction between the cationic surfactant, the active silica and the rhodium precursor under the alkaline region is usually at a temperature in the range of 50 to 200 ° C, preferably at a temperature in the range of 70 to 200 ° C. Particularly preferred is a temperature in the range of more than 100 ° C. and 180 ° C. or less. Since the active silica has a very high reactivity, the above reaction proceeds easily even at a temperature of about 50 ° C., however, according to the present invention, it is particularly preferable to use a pressure reactor such as an autoclave. Thus, by carrying out a hydrothermal reaction at a temperature exceeding 100 ° C. and under 200 ° C. under pressure, a rhodium-supporting mesoporous silica having a high catalytic activity based on rhodium is obtained. Can do. However, when hydrothermal reaction is performed under a pressure exceeding 200 ° C., the surfactant used is decomposed and the desired mesoporous structure is not formed, so that the resulting product has a significantly reduced BET specific surface area. Also, the catalyst performance is significantly reduced.

  Although the reaction time depends on the reaction temperature, it is usually in the range of 0.5 to 3 hours including the aging time. For example, when the reaction temperature is 150 ° C., a uniform complex can be obtained by the reaction within about 3 hours.

In the reaction between the active silica and the cationic surfactant in the alkaline region, the active silica is sequentially electrostatically bonded to the cationic surfactant, and while the adjacent silica is polymerized due to silanol dehydration, A continuous connective tissue precursor is formed. During this time, rhodium is uniformly dispersed in the connective tissue precursor as a hydrated compound of rhodium oxide (Rh ₂ O ₃ or RhO ₂ ).

  In this way, by the reaction between the active silica and the cationic surfactant under the alkaline region, a slurry containing the reaction product is obtained, and this is filtered and washed with water to remove excess ionic species such as chlorine, By drying at a temperature of 100 to 120 ° C., a composite composed of silica on which rhodium oxide is dispersed and supported and a cationic surfactant can be obtained as a solid powder.

  Next, according to the present invention, as the third step, the composite powder carrying rhodium oxide is baked to remove the cationic surfactant to obtain rhodium-supported mesoborous silica. According to the present invention, the composite powder carrying the rhodium oxide is first fired in an air atmosphere. This firing temperature is not less than the temperature at which the surfactant component disappears, and generally not less than 500 ° C. Thus, by baking at a temperature exceeding 500 ° C., the structure of the obtained mesoporous silica can be stabilized and the mechanical strength can be improved. However, firing at a temperature exceeding 1200 ° C. does not contribute to stabilization of the mesoporous structure. In the present invention, the firing temperature is preferably in the range of 500 to 800 ° C.

  The firing time is usually about 10 minutes to 2 hours, although it depends on the firing temperature. In particular, according to the present invention, it is preferable that the composite powder supporting rhodium oxide is fired at a temperature in the range of 500 to 800 ° C. for a time of 1 hour or less.

  Next, as described above, after the composite powder supporting rhodium oxide is fired in an air atmosphere, the fired product is further put under an inert atmosphere or a reducing atmosphere (for example, a hydrogen concentration of about 5%). The rhodium oxide is reduced to rhodium at a temperature in the range of 300 to 500 ° C. for 1 hour or less, and thus rhodium-supported mesoporous silica can be obtained as a powder.

  For example, when preparing a honeycomb structure having rhodium-supported mesoporous silica as a catalyst component on the surface, an aqueous wash coat slurry is prepared by mixing the rhodium oxide-supported mesoporous silica powder with an appropriate inorganic binder. A honeycomb structure in which rhodium-supported mesoporous silica is supported on a honeycomb substrate by applying it to the honeycomb substrate, drying, then firing in air, and further firing in a reducing atmosphere. You can get a body.

Thus, the rhodium-supported mesoporous silica obtained by the method of the present invention has a mesopore structure having an average pore diameter of 10 to 100 angstroms and a porous structure having a nitrogen adsorption specific surface area of 500 m ² / g or more by the BET method. Rhodium is uniformly supported at a supported amount in the range of 0.1 to 5% by weight.

In particular, according to the present invention, to have a high activity as a catalyst, it is preferred that the nitrogen adsorption specific surface area by the BET method is in the range of 600~900m ² / g, in the range of 650~850m ² / g Is most preferred. According to the present invention, the specific surface area of nitrogen adsorption by the BET method is such that active silica, cationic surfactant, and rhodium precursor are mixed and reacted in a predetermined alkaline region, and rhodium supported silica and cationic surfactant. It can be controlled by adjusting the reaction temperature at the time of producing the complex, the alkyl group chain length of the cationic surfactant, the amount of use thereof, and the like.

  Thus, the rhodium-supported mesoporous silica obtained according to the method of the present invention is, for example, a nitrogen oxide by carbon monoxide under an excess of oxygen, as compared with the rhodium-supported mesoporous silica obtained by the impregnation method described above, for example. In particular, it has high catalytic activity for the reduction reaction of nitric oxide.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the following, the average pore diameter of the obtained rhodium oxide-supported mesoporous silica was determined by the BJH method based on the adsorption isotherm, and the specific surface area was determined by the BET method.

Example 1
34.4 g of No. 3 sodium silicate (10 g in terms of silica) was diluted with 100 g of ion-exchanged water, and 350 g of hydrogen ion-type ion exchange resin Amberlite IR-120B was added thereto and stirred about once every 5 minutes. Ion exchange was performed for 3 hours. Thus, after ion-exchange, it filtered and obtained active silica as sol. The pH of this active silica sol was 3.48.

  Separately, 4.0 g of octadecyltrimethylammonium chloride and 16.1 g of hexadecyltrimethylammonium chloride were dissolved in 200 g of ion-exchanged water, and a 40% aqueous solution of tetraethylammonium hydroxide was added to the resulting solution to adjust the pH to 13.02. Adjusted. Next, 10 g of a 0.5 wt% aqueous rhodium nitrate solution was added dropwise to the solution. Thus, the pH of the obtained aqueous solution was 13.00.

Under stirring, the active silica sol was added dropwise to the aqueous solution of the cationic surfactant, and the whole amount was added to obtain a slurry of active silica containing the surfactant. When this slurry was stirred at room temperature for 30 minutes, the pH of the slurry was 9.24. This slurry was put into a beaker placed on a hot stirrer and reacted at 75 ° C. for 3 hours. After completion of the reaction, the slurry was filtered and washed with water, and the resulting solid was dried overnight. The obtained dried product was calcined in air at 500 ° C. for 1 hour to obtain mesoporous silica supporting 0.5 wt% rhodium oxide based on rhodium as a powder. This powder had an average pore diameter of 34 Å and a specific surface area of 1033 m ² / g.

Example 2
In the same manner as in Example 1, a slurry of active silica sol containing a surfactant was obtained. This slurry was placed in a polytetrafluoroethylene beaker and installed in an autoclave (MMJ-200, manufactured by OM Lab Tech). The hydrothermal reaction was performed at 125 ° C. for 3 hours while stirring at 60 rpm. After completion of the reaction, the slurry was filtered, washed with water, and dried overnight. The obtained dried product was calcined in air at 500 ° C. for 1 hour to obtain mesoporous silica supporting 0.5 wt% rhodium oxide based on rhodium as a powder. The average pore diameter of this powder was 33 Å, and the specific surface area was 899 m ² / g.

Example 3
In the same manner as in Example 2, except that the hydrothermal reaction was performed at 150 ° C. for 3 hours, mesoporous silica supporting 0.5 wt% rhodium oxide based on rhodium was obtained as a powder. The average pore diameter of this powder was 33 Å, and the specific surface area was 853 m ² / g.

Example 4
In the same manner as in Example 2, except that the hydrothermal reaction was performed at 170 ° C. for 3 hours, mesoporous silica supporting 0.5 wt% rhodium oxide based on rhodium was obtained as a powder. The average pore diameter of this powder was 34 Å, and the specific surface area was 708 m ² / g.

Reference example 1
In the same manner as in Example 2, except that the hydrothermal reaction was performed at 250 ° C. for 3 hours, mesoporous silica supporting 0.5% by weight of rhodium oxide based on rhodium was obtained as a powder.

Reference example 2
5 g of mesoporous silica (SILFAM) manufactured by Nippon Chemical Industry Co., Ltd. and 50 g of a 0.05 wt% rhodium nitrate aqueous solution based on rhodium were mixed and evaporated to dryness while stirring on a hot stirrer. After drying overnight, the obtained dried product was calcined in air at 500 ° C. for 1 hour to obtain mesoporous silica supporting 0.5 wt% rhodium oxide based on rhodium as a powder.

Reference example 3
(Preparation of honeycomb catalyst structure)
Honeycomb catalyst structures A1 to A4, B1 and B2 were prepared using the rhodium oxide-supported mesoporous silica powders obtained in Examples 1 to 4 and Reference Examples 1 and 2, respectively. That is, 3 g of the above powder, 0.8 g of alumina sol (# 520) manufactured by Nissan Chemical Co., Ltd., 0.4 g of silica sol (Snowtex O) manufactured by Nissan Chemical Co., Ltd., and an appropriate amount of water were mixed. Using a few grams of alumina balls as a grinding medium, the mixture was shaken by hand to loosen the agglomerated powder to obtain a wash coat slurry. The above-mentioned slurry for wash coat was applied to a honeycomb substrate made of cordierite having 400 cells per square inch, dried, fired at 500 ° C. for 1 hour in air, and further 5% by volume of hydrogen and 95%. A honeycomb catalyst structure having 100 g of rhodium-supported mesoporous silica catalyst per liter of the honeycomb substrate was obtained by firing at 500 ° C. for 10 minutes in an air stream composed of nitrogen in a volume%.

(Catalyst nitrogen oxide removal performance test)
A mixed gas containing nitrogen oxides consisting of 100 ppm NO, 1 ppm SO ₂ , 9% O ₂ , 1.5% CO and 6% H ₂ O at a temperature of 250 ° C., 300 ° C., 350 ° C. or 400 ° C. Then, the catalyst was brought into contact with the honeycomb catalyst structure under a space velocity of 50000 h ⁻¹ , and the nitrogen oxide removal performance of the catalyst was examined. The conversion rate (removal rate) from nitrogen oxides to nitrogen was calculated based on the concentration analysis of NO, NO ₂ and N ₂ O using a FT-IR gas analyzer manufactured by Gasmet. The results are shown in Table 1.

Claims (5)

A first step of preparing an active silica by bringing a sodium silicate aqueous solution into contact with a cation exchange resin, and then reacting the active silica, the cationic surfactant and the rhodium precursor at a temperature in the range of 50 to 200 ° C. in the alkaline region. The mesopore having an average pore size of 10 to 100 angstroms is performed in this order by performing a second step of forming a complex of silica containing rhodium and a cationic surfactant, and a third step of firing the complex. A method for producing rhodium-supported mesoporous silica having a structure and rhodium supported on mesoporous silica having a nitrogen adsorption specific surface area of 500 m ² / g or more by BET method.   The method for producing rhodium-supported mesoporous silica according to claim 1, wherein the active silica, the cationic surfactant, and the rhodium precursor are hydrothermally reacted at a temperature in the alkaline region exceeding 100 ° C and not more than 200 ° C.   The method for producing rhodium-supported mesoporous silica according to claim 1 or 2, wherein active silica, a cationic surfactant and a rhodium precursor are reacted in an alkaline region of pH 8-12.   The method for producing rhodium-supported mesoporous silica according to claim 1, wherein the rhodium precursor is used so that the supported amount of rhodium is in the range of 0.1 to 5% by weight. Cationic surfactant is general formula (II)
[R (CH ₃ ) ₃ N] ⁺ X ⁻ (II)
(In the formula, R represents a long-chain alkyl group, and X represents a halogen atom or a hydroxyl group.)
The method for producing rhodium-supported mesoporous silica according to claim 1, wherein the alkyltrimethylammonium halide or alkyltrimethylammonium hydroxide is represented by the formula: