JP2005111336A - Heat-resistant catalyst and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant catalyst excellent in heat resistance and capable of suppressing a catalytic metal deposited on a carrier from sintering while keeping the reaction efficiency of the catalytic metal. <P>SOLUTION: The heat-resistant catalyst is manufactured by mixing the colloid of a noble metal prepared by a reversed micelle method, a metal (L) hydroxide prepared by the reversed micelle method and a hydrolysate of a metal (M) alkoxide and sintering the obtained mixture so that the noble metal and the metal (L) oxide are deposited on the surface of the metal (M) oxide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat-resistant catalyst and a method for producing the same, and more specifically, a reverse micelle solution in which a catalyst component is dissolved inside a micelle is formed, and an insolubilizing agent is added thereto to obtain noble metal particles and a metal hydroxide. And a heat-resistant catalyst characterized in that the reverse micelle solution is mixed with a support material and the noble metal particles and metal hydroxide are supported on the conductive support material.

  Catalysts in which noble metal particles such as platinum and palladium are supported on a carrier such as alumina are used in a wide range of fuel reforming catalysts, exhaust gas purification catalysts, automobile power supplies and stationary power supplies.

  In the catalytic reaction using such a catalyst, the reaction proceeds on the catalyst surface. Therefore, conventionally, it is most effective to reduce the size of the noble metal particles to about several nm or less and to use a catalyst having a large particle surface area. In order to exhibit high catalyst performance, it is desirable that the noble metal particles maintain a predetermined particle size on the support and are uniformly dispersed.

  As a general method for producing the catalyst, a heat-resistant inorganic oxide-supported noble metal catalyst is produced by impregnating a heat-resistant inorganic carrier with an aqueous solution of a water-soluble noble metal compound and performing firing or the like. However, the impregnation method has a problem that the size of the noble metal particles is not uniform and the particle surface area cannot be sufficiently increased.

  The catalyst is required to maintain the catalyst performance over a long period of time, and is said to be 5000 hours for an automotive power source and 40,000 hours for a stationary power source. However, the surface state of the noble metal particles is very unstable. Therefore, when thermal energy is applied, the noble metal particles easily move on the surface of the support and are sintered or dissolved in the support, so that there is a problem that the catalyst performance is deactivated.

  As a method for solving these problems, there is a microemulsion method (reverse micelle method) as described in Patent Documents 1 and 2. The microemulsion method uses a microemulsion in which an aqueous solution containing a catalytic element such as a noble metal is present as ultrafine droplets, precipitates or reduces the noble metal to insolubilize it, and creates a solution containing the insolubilized noble metal. In this method, a dispersion liquid dispersed as ultrafine droplets (microemulsion) is used. As a result, a catalytic element such as a noble metal can be supported in a highly dispersed manner with a predetermined particle size on the surface of the support.

  For example, in Patent Document 1, after obtaining a noble metal colloid by the microemulsion method, it is supported and calcined on a carrier precursor, and the surface of the metal oxide carrier 101 is schematically shown in FIG. Describes a catalyst having a structure in which precious metal particles 102 are adsorbed.

Further, Patent Document 2 describes a catalyst having a structure in which noble metal particles 102 are buried in a carrier 101 as shown in FIG. The catalyst further has a reaction inhibitor (not shown) attached to the surface of the support 101 for suppressing the reaction between the support 101 and the noble metal particles 102. In Example 8 of Patent Document 2, such a catalyst is prepared by mixing a microemulsion containing a palladium nitrate solution, which is a compound containing a noble metal as a catalytic element, and a microemulsion containing a palladium reducing agent and barium nitrate. A method is used in which barium carbonate is precipitated as a reaction inhibitor by bubbling with a gas, and palladium and barium carbonate are aggregated.
JP-A-7-246343 JP-A-10-216517

  However, since the catalyst described in Patent Document 1 has a structure in which only the noble metal particles 102 are supported on the surface of the support 101, the sintering of the noble metal particles 102 easily occurs as shown in FIG. It is easy to suppress sintering.

  Further, in the method described in Patent Document 2, 20 to 90% of the noble metal particles 102 are buried in the surface of the carrier 101, and the noble metal particles may react with the carrier and be dissolved. Furthermore, since barium is supported as a reaction inhibitor around the noble metal particles, the contact area between the noble metal and the reaction gas is reduced, and the reaction efficiency may be reduced.

  The present invention has been made in view of the above problems, and provides a heat-resistant catalyst excellent in heat resistance by suppressing sintering of the catalyst metal supported on the support while maintaining the reaction efficiency of the catalyst metal. Objective.

  The inventors of the present invention consider that the sintering of the catalyst metal is caused by the movement of the catalyst metal with the volume change due to the change in the crystal structure of the support in the firing step performed after the catalyst metal particles are supported on the support. In view of the above, the present invention has been achieved.

  That is, the present invention relates to a noble metal colloid prepared using the reverse micelle method, a metal (L) hydroxide prepared using the reverse micelle method, and a gel metal (M) obtained by hydrolysis of a metal (M) alkoxide. By providing a heat-resistant catalyst in which a noble metal and a metal (L) oxide are supported on the surface of a metal (M) oxide by mixing the hydroxide and firing the obtained mixture, Is a solution.

  The heat-resistant catalyst of the present invention is obtained by supporting a metal (L) hydroxide between noble metal particles on the surface of a carrier raw material and firing it to suppress or prevent sintering of noble metal particles due to heating or the like. In addition, oxidation of the noble metal particles can be prevented.

  Further, since the noble metal particles and the metal (L) hydroxide are independently strongly bonded to the support surface, a sufficient contact area between the noble metal particles and the reactive gas can be ensured.

  Therefore, the heat-resistant catalyst can maintain excellent catalytic performance even in a high temperature atmosphere.

  The first of the present invention is a noble metal colloid prepared using a reverse micelle method, a metal (L) hydroxide prepared using a reverse micelle method, and a gel metal (M) obtained by hydrolysis of a metal (M) alkoxide. ) A heat-resistant catalyst in which a noble metal and a metal (L) oxide are supported on the surface of a metal (M) oxide by mixing a hydroxide and firing the resulting mixture.

  The catalyst produced by the conventional method uses a hydrolyzate of metal alkoxide as a carrier raw material, and supports the noble metal particles by an impregnation method, followed by a calcination step. In the firing step, as the support material is dehydrated from the hydrate form and changed to the oxide form, a volume change occurs in the support material. At this time, there was a possibility that sintering would occur easily due to movement of the noble metal particles carried on the carrier raw material. In order to exhibit high catalytic activity, it is desired that the noble metal particles on the support surface maintain a predetermined particle size and are uniformly dispersed. Therefore, sintering of the noble metal particles causes an increase in the noble metal particles, a decrease in dispersibility, and the like, causing deterioration of the catalytic activity.

  For example, the catalyst described in Patent Document 1 first forms reverse micelles containing insoluble noble metal salts in the form of ultrafine particles, and then adds a reducing agent to the reverse micelles to reduce the noble metal salts to noble metal colloids. The noble metal colloid is obtained by immobilizing it on a metal oxide. As shown in FIG. 1A, such a catalyst has a structure in which the noble metal particles 102 are adsorbed on the surface of the support 101, and thus it is difficult to prevent or suppress the movement of the noble metal particles 102. Therefore, as shown in FIG. 1B, sintering of the noble metal particles 102 is likely to occur.

  The catalyst described in Patent Document 2 describes a catalyst having a structure in which noble metal particles 102 are buried in a carrier 101 as shown in FIG. In the catalyst, a reaction inhibitor for suppressing the reaction between the support 101 and the noble metal particles 102 is attached to the surface of the support 101 (not shown). Such a catalyst is produced by mixing a reverse micelle containing a compound containing a catalytic element such as a noble metal with a reverse micelle containing a noble metal reducing agent and a reaction inhibitor and bubbling with carbon dioxide gas to suppress the reaction. Is precipitated as a carbonate to agglomerate a noble metal and a reaction inhibitor. In the catalyst obtained by the above method, 20 to 90% of the noble metal particles 102 are buried on the surface of the support 101, and the reaction suppressing substance is supported on the surface of the noble metal supported on the support. There is a problem that the contact area is reduced and the reaction efficiency is lowered.

  However, the heat-resistant catalyst of the present invention is a heat-resistant catalyst in which the noble metal particles 102 and the metal oxide 103 are separately supported on the surface of the carrier 101 using the reverse micelle method as shown in FIG. . In the heat-resistant catalyst, the noble metal particles 102 and the metal (L) oxide 103 are independently firmly bonded to the support 101, so that a sufficient contact area with the reaction gas can be secured. Furthermore, even under severe use conditions such as in a high temperature atmosphere, the metal (L) oxide 103 serves as a barrier, and sintering of the noble metal particles 102 can be suppressed. Therefore, the catalyst of the present invention has high catalyst performance and heat resistance.

  Hereinafter, the heat resistant catalyst of the present invention will be described in more detail.

  The heat-resistant catalyst of the present invention is obtained by mixing a noble metal colloid prepared using the reverse micelle method, a metal (L) hydroxide prepared using the reverse micelle method, and a hydrolyzate of metal (M) alkoxide. In addition, the obtained mixture is fired, whereby a noble metal and a metal (L) oxide are supported on the surface of the metal (M) oxide.

  In the present invention, the “reverse micelle method” means using a reverse micelle solution in which an aqueous solution containing a desired metal ion is present as ultrafine droplets, precipitating or reducing the metal ion, and insolubilizing the metal ion. This is a method of using a dispersion (reverse micelle solution) in which a metal-containing solution is highly dispersed as ultrafine particulate reverse micelles.

  The reverse micelle solution contains micelles formed by assembling the amphiphile by mixing an amphiphile such as a surfactant molecule in an organic solvent, and contains the desired metal in the micelle. Solution. In the organic solvent phase, the hydrophobic group is oriented to the outside, that is, the organic solvent phase side, the hydrophilic group is oriented to the inside, and the orientation of the hydrophobic group and the hydrophilic group is opposite to that in the aqueous solvent phase. Use reverse micelle solution. FIG. 4 schematically shows the reverse micelle solution. Such a reverse micelle solution can be prepared by adding an aqueous solution to a solution obtained by dissolving a surfactant in an organic solvent and stirring the solution. The portion where the hydrophilic groups are gathered has the ability to retain polar molecules such as water. The aqueous solution becomes extremely small water droplets having a diameter of several nanometers to several tens of nanometers and is uniformly dispersed in the organic solvent. However, the size of the microstructure of the reverse micelle is controlled by the molar ratio of the injected aqueous solution and the surfactant. be able to.

  In the present invention, “a noble metal colloid prepared using the reverse micelle method” means that a noble metal ion insolubilizing agent is added to a reverse micelle solution containing an aqueous noble metal ion solution inside the micelle, whereby the noble metal ion is added inside the micelle. Is a noble metal colloid obtained by reducing to noble metal. The insolubilizing agent for the noble metal ions is one that can convert the noble metal ions inside the micelles into colloidal noble metal particles, and can be appropriately prepared depending on the noble metal used. The insolubilizing agent may be added as an aqueous solution or a reverse micelle solution containing the insolubilizing agent inside the micelle.

  The “metal (L) hydroxide prepared using the reverse micelle method” means that the metal (L) ion is added to a metal (L) into a reverse micelle solution containing a metal (L) ion aqueous solution inside the micelle. By adding an insolubilizing agent to make the hydroxide insolubilized, the metal (L) ion is reduced to the metal (L) hydroxide inside the micelle, and the metal (L) ion precipitate (hydroxide) and Become. In the present invention, the insolubilizing agent precipitates metal (L) ions as hydroxides. By supporting the metal (L) hydroxide on the surface of the carrier raw material, the metal (L) hydroxide is dehydrated to form the metal (L) oxide in the firing step, preventing the oxidation of the noble metal particles and catalytic activity. Can be suitably maintained. Moreover, it can be set as a particulate precipitate by setting it as pH 6-10 using precipitation agents, such as aqueous ammonia, as an insolubilizing agent. The precipitate thus obtained can be uniformly dispersed without agglomeration of the noble metal particles and the metal (L) hydroxide, and the noble metal particles and the metal (L) hydroxide on the surface of the carrier raw material. Can be carried separately.

  In the present invention, a hydrolyzate of metal (M) alkoxide is used as the carrier material. A metal (M) alkoxide can be easily reacted with water and hydrolyzed to obtain a particulate homogeneous metal (M) hydroxide.

  Therefore, a homogeneous metal can be obtained by mixing a noble metal colloid prepared using the reverse micelle method, a metal (L) hydroxide prepared using the reverse micelle method, and a hydrolyzate of metal (M) alkoxide. (M) A mixture of a hydroxide, a particulate noble metal colloid and a metal (L) hydroxide can be obtained. By calcining such a mixture, a heat-resistant catalyst in which a noble metal and a metal (L) oxide are highly dispersed and supported at predetermined intervals on the surface of the metal (M) oxide can be obtained.

  The heat-resistant catalyst of the present invention is not limited to the one described above, but a reverse micelle solution containing a noble metal colloid aqueous solution inside the micelle, a reverse micelle solution containing a metal (L) hydroxide aqueous solution inside the micelle, and a metal ( M) It is obtained by mixing alkoxide and firing the resulting mixture.

  By mixing a reverse micelle solution containing a noble metal colloid aqueous solution inside the micelle and a reverse micelle solution containing a metal (L) hydroxide aqueous solution inside the micelle, the micelles are combined, and the noble metal colloid and the micelle inside A reverse micelle solution containing metal (L) hydroxide is obtained. When such a reverse micelle solution and a metal (M) alkoxide are mixed, hydrolysis is caused by water (soluble water) in the reverse micelle, and a metal (M) hydroxide as a support material is generated. As a result, a mixture containing homogeneous metal (M) hydroxide, fine noble metal colloid and metal (L) hydroxide is obtained.

  As the mixture, it is preferable to use a mixture in which a noble metal and a metal (L) hydroxide are supported on the surface of a metal (M) hydroxide which is a carrier raw material. In the firing step, the noble metal may be oxidized and lose its catalytic activity. However, after the metal (L) hydroxide supported on the surface of the support raw material is dehydrated and changed into an oxide form, By performing the heat treatment at, the oxidation of the noble metal can be effectively suppressed.

  The mixture is preferably such that the water content of the metal (L) hydroxide is smaller than that of the metal (M) hydroxide as the carrier raw material.

  The metal (M) hydroxide and metal (L) hydroxide, which are carrier raw materials, exist in a hydrate form, and crystal structure due to heat shrinkage from the hydrate form to the oxide form in the firing step. A change in volume occurs due to the change in. At this time, the metal (L) hydroxide is smaller in volume than the metal (M) hydroxide by making the water content of the metal (L) hydroxide smaller than that of the metal (M) hydroxide. A crystal structure with small change can be obtained. Thereby, the range in which the noble metal particles move on the support surface can be narrowed, sintering can be prevented and suppressed, and the catalytic activity can be maintained.

  Here, the “moisture content” is the sum of OH groups contained as hydroxide per mole of metal and OH groups contained as coordination water (structural water) in the metal hydroxide. The amount of the hydroxyl group and the coordination water (structural water) can be adjusted by adjusting the temperature, water vapor pressure, and the like to predetermined conditions. Thereby, the water content of the metal (L) hydroxide can be made smaller than that of the metal (M) hydroxide.

  In the heat-resistant catalyst of the present invention, when the average particle diameter of the metal (L) oxide supported on the support surface is R1, and the average particle diameter of the metal (M) oxide of the support is R2, R2 / R1 It is good to make 2-100, especially 2-50. When R2 / R1 is smaller than 2, the metal (L) oxide does not exhibit the effect of inhibiting and suppressing the sintering of the carrier metal (M) oxide, and when it exceeds 100, the metal (L) oxide particles are conspicuous. If it is small, the sintering preventing and suppressing effects cannot be maintained, so the above range is preferable.

  Further, when the average particle diameter of the noble metal is R3, it is more preferable that R2 / R1 is 2 to 100 and R1 / R3 is 1 to 50, particularly 2 to 20. This makes it possible for the noble metal particles supported on the support metal oxide to narrow the range of movement of the noble metal particles on the support surface, significantly improve the action of preventing and suppressing sintering, improve the initial catalytic activity, and improve durability. It can be maintained later. At this time, if R1 / R3 is smaller than 1, it is difficult to suppress sintering of the noble metal particles, and if it exceeds 50, the dispersibility of the noble metal is lowered, so the above range is preferable.

  The noble metal is at least one noble metal selected from the group consisting of platinum, palladium, rhodium, osmium, ruthenium, and iridium. Among these, platinum, rhodium, and palladium are preferably used because of their excellent catalytic activity.

  The average particle diameter of the noble metal supported on the support surface is 1 to 10 nm, preferably 2 to 6 nm. If the average particle diameter is within this range, a surface area sufficient for catalytic activity can be secured, and the amount of catalytic activity per unit mass of the noble metal can be increased.

  The metal (L) supported on the support surface is at least one metal selected from gallium, cerium, zirconium, vanadium, manganese, iron, cobalt, nickel, germanium, chromium, copper, zinc, and tungsten. Such a metal (L) is hardly dissolved in a carrier and is advantageous in terms of improving mass activity (activity per unit mass of noble metal). Furthermore, the metal oxide composed of such a metal (L) can exhibit a co-catalytic action for reducing the oxygen concentration on the surface of the noble metal particles and preventing oxidation of the noble metal in an oxygen-excess atmosphere. More preferably, zirconium, cerium, or titanium is used as the metal (L).

  The average particle size of the metal (L) oxide supported on the support surface is 10 to 50 nm, preferably 10 to 30 nm. When the average particle diameter is within this range, volume change due to change in crystal structure accompanying thermal contraction of the support metal oxide can be suppressed.

  The metal (M) used as the carrier is one or more metals selected from aluminum, silica, gallium, titanium, cerium, zirconium, vanadium, and tungsten. The average particle size of the metal (M) oxide is 100 to 1000 nm, more preferably 100 to 500 nm.

  In the present invention, the average particle diameter can be calculated by the crystallite diameter determined from the half-value width of the metal diffraction peak in X-ray diffraction or the average value of the metal particle diameter examined by a transmission electron microscope. it can.

  The amount of metal supported on the carrier in the heat-resistant catalyst of the present invention is 1 to 40% by mass, more preferably 1 to 20% by mass as the total amount of noble metal and metal (L) per heat-resistant catalyst. It is good. When the amount of metal is less than 1% by mass, the catalytic activity is insufficient, and when it exceeds 40% by mass, the catalytic activity is saturated, so the above range is preferable.

  The noble metal and metal (L) oxide supported on the surface of the support may have a mass ratio of 1: 1 to 20: 1, preferably 2: 1 to 10: 1. This is because if the ratio of the noble metal to the metal (L) oxide is out of this range, the catalytic activity may be insufficient.

  Since the noble metal and the metal (L) oxide are highly dispersed and supported on the support surface, the heat-resistant catalyst in the present invention can suppress the movement of noble metal particles due to high temperature atmosphere or strong impact. Moreover, since the noble metal and the metal (L) oxide are separately supported on the surface of the support, a sufficient contact area between the noble metal and the reaction gas can be secured, and the reaction efficiency can be maintained. Furthermore, the metal (L) oxide supported on the surface of the carrier can reduce the oxygen concentration on the surface of the catalyst and prevent the oxidation of the noble metal in an oxygen-excess atmosphere. Can do.

  Therefore, the heat-resistant catalyst of the present invention having such various characteristics is suitable for various applications that require excellent catalyst performance even under severe usage environments such as exhaust gas purification catalysts, fuel reforming catalysts, automobiles and stationary power supplies. Can be used.

  The second of the present invention is a method for producing a heat-resistant catalyst. The first heat-resistant catalyst can also be produced according to the second aspect of the present invention.

  The production method of the present invention includes a reverse micelle solution A containing a noble metal ion aqueous solution inside a micelle and a solution obtained by adding a reducing agent of the noble metal ion aqueous solution, and a reverse micelle solution B containing metal (L) ions inside the micelle. And a solution added with a precipitating agent that generates a metal (L) hydroxide is mixed with a reverse micelle C containing a metal (M) alkoxide solution or a hydrolyzate of metal (M) alkoxide. The method of mixing and carrying | supporting a noble metal and a metal (L) hydroxide on the hydrolyzate of a metal (M) alkoxide is mentioned.

  In the said method, the schematic diagram until mixing the solution which added the reducing agent to the reverse micelle solution (A) and the solution which added the precipitant to the reverse micelle solution (B) is shown in FIG.

  First, as shown in FIG. 5 (A), a surfactant 2 is mixed with an organic solvent 1, and when an aqueous noble metal ion solution is added and stirred, micelles having a hydrophilic group 3 on the inside and a hydrophobic group 4 on the outside are mixed. 5 is formed, and a noble metal ion aqueous solution is encapsulated inside the micelle. When a reducing agent aqueous solution is used instead of the noble metal ion aqueous solution, micelles 6 containing the reducing agent aqueous solution shown in FIG. 5B are generated. When the two reverse micelle solutions are mixed, the reverse micelles are bonded to each other and the reduction reaction proceeds in the micelles (FIG. 5C). Further, when the reduced particles 7 are aged, the colloidal noble metal controlled by the micelle size is formed. The contained micelle 8 can be obtained (FIG. 5D). Noble metal ultrafine particles are excellent in dispersibility of noble metal ultrafine particles inside the micelle, and even when two or more kinds of noble metal ions are contained, noble metal ultrafine particles having an extremely uniform composition can be obtained.

  Next, when a metal (L) ion aqueous solution is used instead of the noble metal ion aqueous solution, micelles 9 including the metal (L) ions shown in FIG. 5E are formed. Similarly, when a precipitant aqueous solution capable of precipitating metal (L) ions as metal (L) hydroxide is used instead of the noble metal ion aqueous solution, the micelle 10 enclosing the precipitant aqueous solution shown in FIG. Generated. When these reverse micelles are mixed, the reverse micelles bind to each other and a precipitation reaction proceeds in the micelles (FIG. 5 (G)), and further ripening of the precipitates results in micelles as shown in FIG. 5 (H). A micelle 11 containing metal (L) hydroxide controlled by size can be obtained. A metal (L) hydroxide having a uniform composition is obtained inside the micelle, and a metal (L) hydroxide having an extremely uniform composition can be obtained even when two or more kinds of metal (L) ions are contained.

  Next, as shown in FIG. 5 (I), when both micelles are mixed and stirred, the micelles are combined to obtain micelles having a uniform composition. Furthermore, by aging, as shown in FIG. 5 (J), micelles 12 containing noble metal particles and metal (L) hydroxide controlled by the micelle size are obtained. In the micelle, the noble metal particles and the metal hydroxide are dispersed very uniformly in a monodispersed state.

  The reverse micelle solution containing the noble metal colloid and the metal (L) hydroxide thus obtained is mixed with the metal (M) alkoxide solution in which the metal (M) alkoxide is dispersed in an organic solvent or the like. When added to water, the metal (M) alkoxide is easily hydrolyzed to obtain a metal (M) hydroxide that is homogeneous in particle units. Therefore, hydrolysis of the metal (M) alkoxide occurs at the very wide interface of the reverse micelle by the aqueous solution in the micelle. At this time, metal (M) hydroxide as a support material is generated so as to surround the particles and precipitates in the micelle. Thereby, the mixture which the noble metal and the metal (L) hydroxide carry | supported on the metal (M) hydroxide surface is obtained.

  Thereafter, the mixture is separated and washed by a method such as centrifugation, filtration, washing, etc., followed by a separation step, followed by pulverization after drying in the drying step to obtain a precursor of a heat-resistant catalyst, and further firing the precursor When calcined by the process, a heat-resistant catalyst can be produced.

  Various substances can be used as the organic solvent that can be used to form reverse micelles. For example, cyclohexane, methylcyclohexane, cycloheptane, heptanol, octanol, dodecyl alcohol, cetyl alcohol, isooctane, and n-heptane. N-hexane, n-decane, benzene, toluene, xylene and the like. Moreover, you may add alcohol etc. in order to adjust the magnitude | size of the water droplet in a reverse micelle solution. The organic solvent can be used alone or in combination of two or more. Furthermore, it can be used for the preparation of reverse micelle solution A and reverse micelle solution B, and when supplying a reducing agent for precious metal ions and a precipitating agent for metal (L) ions as a reverse micelle solution, It can also be used for the preparation of solutions. At this time, the organic solvent used for any of the reverse micelle solutions and the organic solvent used for the other reverse micelle solutions may be the same or different.

  Surfactants that form reverse micelle solutions include polyoxyethylene nonylphenyl ether, magnesium laurate, zinc caprate, zinc myristate, sodium phenyl stearate, aluminum dicaprylate, tetraisoamylammonium thiocyanate. Net, n-octadecyltri-n-butylammonium formate, n-amyltri-n-butylammonium iodide, sodium bis (2-ethylhexyl) succinate, sodium dinonylnaphthalenesulfonate, calcium cetyl sulfate, dodecyl Amine oleate, dodecylamine propionate, cetyltrimethylammonium bromide, stearyltrimethylammonium bromide, cetyltrimethylammonium chloride, stearyltrimethylan Nium chloride, dodecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, didodecyldimethylammonium bromide, ditetradecyldimethylammonium bromide, didodecyldimethylammonium chloride, ditetradecyldimethylammonium chloride, ( 2-octyloxy-1-octyloxymethyl) polyoxyethylene ethyl ether and the like. The surfactant can also be used for preparing any reverse micelle solution, and two or more kinds can be used in combination. In addition, the addition amount of surfactant with respect to an organic solvent is 10-300 mass with respect to 100 mass parts of organic solvents. If the amount is less than 10 parts by mass, it is difficult to form reverse micelles. On the other hand, if the amount exceeds 300 parts by mass, rod-like micelles are formed, which is disadvantageous in that the noble metal particle diameter is controlled to a specific size to prevent aggregation.

  The size of the micelle can be adjusted by the type of solvent and surfactant used and the amount added. In addition, the smaller the amount of noble metal and metal (L) hydroxide contained in the micelle, the smaller the particle size of the noble metal and metal (L) hydroxide to be supported. Accordingly, it may be appropriately prepared so as to obtain a desired particle diameter, but the number of moles of noble metal or metal (L) hydroxide contained in the reverse micelle per mole of the surfactant is about 2 to 20 moles. It is good to make it.

  The noble metal ion is at least one kind of noble metal ion selected from the group consisting of platinum, palladium, rhodium, osmium, ruthenium and iridium, and the source of these ions is not particularly limited and is a compound containing these ions widely. Can be used. Examples of such compounds include chlorides, nitrates, sulfates, chlorides, acetates and amine compounds of the noble metals.

  More specifically, platinum chloride (hexachloroplatinic acid hexahydrate), chlorides such as palladium chloride, rhodium chloride, ruthenium chloride, nitrates such as palladium nitrate, rhodium nitrate, iridium nitrate, palladium sulfate, rhodium sulfate, etc. Acetates such as sulfate and rhodium acetate, amine compounds such as dinitrodiammine platinum nitrate solution and dinitrodiammine palladium solution are preferable. The concentration of these noble metal ions is preferably 0.1 to 50% by mass, more preferably 0.5 to 20% by mass in terms of metal.

  Moreover, as a reducing agent for noble metal ions, hydrogen, hydrazine, sodium borohydride, sodium thiosulfate, citric acid, sodium citrate, L-ascorbic acid, sodium borohydride, formaldehyde, methanol, ethanol, ethylene, monoxide Carbon etc. are mentioned. What can be prepared as an aqueous solution of hydrazine or the like may be added directly to the reverse micelle solution as an aqueous solution having a concentration of 0.1 to 40% by weight. You may add to. If the aqueous solution has a concentration of 0.1 to 40% by mass, it can be colloidally dispersed in the micelle even when the noble metal ion becomes noble metal particles in the micelle. Note that a powdered substance such as sodium borohydride can be supplied as it is. A gaseous substance at room temperature such as hydrogen can be supplied by bubbling.

Examples of the metal (L) ion include at least one transition metal ion selected from the group consisting of vanadium, manganese, iron, cobalt, nickel, chromium, copper, and zinc. These ions are nitrates, sulfates, ammonium salts, amines, carbonates, bicarbonates, halogen salts, nitrites, inorganic salts such as oxalic acid, carboxylates and hydroxides such as formate, It is preferable to supply as a compound such as alkoxide and oxide.
These can be appropriately selected depending on the type of solvent to be dissolved and pH.

  As the metal (L) ion precipitating agent, one that produces a metal (L) hydroxide precipitate such as ammonia water or tetramethylammonium hydroxide is used. By supporting the metal (L) hydroxide on the surface of the carrier raw material, the metal (L) hydroxide is dehydrated and becomes a metal (L) oxide in the firing step, thereby preventing oxidation of the noble metal particles. Thus, the catalytic activity can be suitably maintained.

  Moreover, it is preferable to adjust pH of reverse micelle aqueous solution to 6-12, Preferably it is 7-10 using such a precipitant. As a result, the noble metal particles and the metal (L) hydroxide can be uniformly dispersed in the reverse micelle without agglomeration, and the noble metal particles and the metal (L) hydroxide are supported separately on the surface of the support material. Can be made. Ammonia water, tetramethylammonium hydroxide or the like may be added directly to the reverse micelle solution as an aqueous solution having a concentration of 0.1 to 30% by mass, but the reverse micelle solution may be prepared and added using the solution. Good. In addition, if it is an aqueous solution with a density | concentration of 0.1-30 mass%, a metal (L) hydroxide of a uniform composition will be obtained within a micelle.

  The metal (M) constituting the metal (M) alkoxide that is the carrier material is not particularly limited as long as the metal (M) oxide is suitably used as the carrier. Examples thereof include one or more metals selected from aluminum, silica, gallium, titanium, cerium, zirconium, vanadium, and tungsten. When hydrolysis is performed using a metal alkoxide mixture composed of two or more metals, a composite oxide can be obtained. At this time, the hydrolysis rate of the metal alkoxide varies depending on the type of metal. Therefore, in the case of a composite oxide, it is preferable that the hydrolysis rate be made comparable by adding a hydrolysis catalyst. Further, the metal (L) and the metal (M) are selected so as not to be the same.

  In the present invention, specific examples of the metal (M) alkoxide include aluminum alkoxides such as aluminum triethoxide, aluminum triisopropoxide, and aluminum tributoxide; silicon tetraethoxide, silicon tetraisopropoxide, silicon tetrabutoxide, and the like. Silicon alkoxide; Gallium alkoxide such as gallium isopropoxide; Titanium alkoxide such as titanium tetraethoxide, titanium tetraisopropoxide and titanium butoxide; Zirconium alkoxide such as zirconium ethoxide, zirconium tetraisopropoxide and zirconium tetrabutoxide; Vanadium oxy Vanadium alkoxide such as isopropoxide; Tungsten alkoxide such as tungsten ethoxide Such as soil and the like.

As the metal (M) alkoxide, a metal (M) alkoxide solution dispersed in an organic solvent is preferably used. Examples of the organic solvent include cyclohexane, methylcyclohexane, cycloheptane, heptanol, octanol, dodecyl alcohol, cetyl alcohol, isooctane, n-heptane, n-hexane, n-decane, benzene, toluene, xylene and the like.
The metal (M) alkoxide is added in an amount of 1 to 40 parts by mass, preferably 5 to 20 parts by mass with respect to 100 parts by mass of the organic solvent.

  The metal (M) alkoxide undergoes a hydrolysis reaction at a wide interface of reverse micelles to form a metal (M) hydroxide as a hydrolyzate. The total amount of water used in the hydrolysis reaction of the metal (M) alkoxide is 1 to 10 mol times, preferably 1 to 3 mol times the theoretical amount required for the hydrolysis reaction of the metal (M) alkoxide. Further, when the hydrolysis reaction is slow, a catalyst for promoting the hydrolysis may be added. In this case, water containing about 0.01 to 1% by mass of ammonia water or about 0.01 to 1% by mass of dilute nitric acid may be used as the water for hydrolysis. You may add in a micelle solution.

  The metal (M) alkoxide is not limited to the above-described method of adding as a dispersion dispersed in an organic solvent such as cyclohexane when mixed with the reverse micelle containing the noble metal and the metal (L) hydroxide, A reverse micelle solution containing a hydrolyzate of metal (M) alkoxide may be added. Also by such a method, the noble metal and the metal (L) hydroxide can be supported on the surface of the metal (M) hydroxide. The organic solvent and surfactant used for the reverse micelle solution may be the same as the reverse micelle solution containing a noble metal ion aqueous solution.

  However, since a metal (M) hydroxide having a uniform particle diameter can be obtained, it is preferable to use a dispersion liquid in which a metal (M) alkoxide is dispersed in an organic solvent.

  Further, the mixing of the reverse micelle solution containing the noble metal and the metal (L) hydroxide and the metal (M) alkoxide solution may be performed by adding the reverse micelle solution to the metal (M) alkoxide solution. The reverse micelle solution is preferably added to the metal (M) alkoxide solution. Thereby, a metal (M) hydroxide having a uniform particle diameter is obtained.

  The hydrolysis temperature varies depending on the type of metal alkoxide, but is generally 20 to 60 ° C, preferably 30 to 50 ° C. When water is added to the reverse micelle solution, the added water is desirably added in portions from 0 to 8 hours, preferably from 1 to 2 hours from the start of the reaction. Further, after completion of the addition of water, the hydrolysis reaction is completed by maintaining at 20 to 60 ° C., preferably 30 to 50 ° C. with stirring for 0 to 12 hours, preferably 1 to 8 hours, and thereafter 0 to 3 hours, preferably It is good to age at the said temperature for 1-2 hours. In this hydrolysis reaction, the reaction proceeds and a colloidal product is formed. The pH of the reaction solution during the hydrolysis reaction varies depending on the type of metal alkoxide and the like, but is generally 3 to 11, preferably 7 to 11, and more preferably 8 to 10.

  The hydrolyzate of metal (M) alkoxide, which is a support material, and the metal (L) hydroxide supported on the surface of the support material exist in a hydrate form. Accordingly, they undergo volume changes as the crystal structure changes to an oxide form by dehydration in a subsequent firing step. At this time, as described above, it is preferable that the metal (L) hydroxide has a lower water content than the metal (M) hydroxide of the carrier material. Thereby, a movement of a noble metal can be suppressed effectively.

  The reverse micelle solution A, reverse micelle solution B, reducing agent, and precipitating agent are added in the order of adding noble metal ions to the reverse micelle solution A and adding a precipitant to the reverse micelle solution B. ) Since the ion becomes a hydroxide, (1) In addition to the above-described method of adding a reducing agent to the reverse micelle solution A, adding a precipitant to the reverse micelle solution B, and then mixing them, (2) A method of adding a reducing agent to the reverse micelle solution A, mixing the reverse micelle solution B thereto, and then adding the precipitating agent for the metal (L) ions, and (3) the reverse micelle solution A and the reverse micelle solution B A method in which a reducing agent is first added to the mixed solution and a precipitant is added later. (4) A precipitant is first added to a mixed solution of reverse micelle solution A and reverse micelle solution B, and then reduced. (5) A precipitant is added to the reverse micelle solution B. In addition a reverse micellar solution A, and a method of further adding a reducing agent. Schematic diagrams of the above (2) to (4) are shown in FIGS. 6, 7, and 8, respectively. Since the noble metal and the metal (L) hydroxide can be supported on the surface of the carrier raw material while maintaining dispersibility without agglomeration, the method (1) is preferably used.

  In the present invention, after the noble metal and the metal (L) hydroxide are attached to the surface of the support material, the support material is isolated from the solution and the support is dried. As the drying method, for example, natural drying, evaporation to dryness, rotary evaporator, spray dryer, drying with a drum dryer, or the like can be used. What is necessary is just to select drying time suitably according to the method to be used. Depending on the case, it is good also as drying in a baking process, without performing a drying process.

  The firing step is performed at a temperature of 400 to 800 ° C, preferably 400 to 600 ° C. The firing is preferably performed in an air circulation atmosphere. This is because formation of the metal hydroxide is facilitated. However, when firing in an air circulation atmosphere, the noble metal is easily oxidized, and if the noble metal is oxidized, the catalytic activity may decrease.

  Therefore, it is preferable that the calcination is performed in an air atmosphere and then in an inert gas atmosphere such as argon, nitrogen, and helium. Thereby, a metal oxide can be formed from a metal hydroxide, and furthermore, a heat-resistant catalyst carrying a non-oxidized noble metal can be obtained. Moreover, the firing temperature in the air circulation atmosphere and in the inert gas atmosphere may be the same or different.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.

<Example 1>
Using 44 g of polyoxyethylene (5) nonylphenyl ether as a surfactant, cyclohexane was added to 1.0 L (0.1 mol / L), and this was mixed and stirred. To this, 10.0 g of dinitrodiammine platinum aqueous solution (Pt concentration 8.0 mass%) was added and stirred for 1 hour until it became transparent to prepare reverse micelle solution A.

  Using 44 g of polyoxyethylene (5) nonylphenyl ether as a surfactant, cyclohexane was added to 1.0 L (0.1 mol / L), and this was mixed and stirred. To this was added 13.2 g of a 0.5% by mass hydrazine aqueous solution (1/2 molar amount of Pt) as a reducing agent, and the mixture was stirred for 1 hour to obtain reverse micelle solution B.

  Using 44 g of polyoxyethylene (5) nonylphenyl ether as a surfactant, cyclohexane was added to 1.0 L (0.1 mol / L), and this was mixed and stirred. To this, 28.4 g of 1.0 mass% aqueous ammonia solution was added as a precipitant and stirred for 1 hour until it became transparent to prepare reverse micelle solution C.

Using 44 g of polyoxyethylene (5) nonylphenyl ether as a surfactant, cyclohexane was added to 1.0 L (0.1 mol / L), and this was mixed and stirred. To this, 21.9 g of a 5% by mass zirconium oxynitrate (ZrO (NO ₃ ) ₂ .2H ₂ O) aqueous solution was added and stirred for 1 hour until it became transparent, whereby a reverse micelle solution D was obtained.

  At this time, the molar ratio in the reverse micelle aqueous solution with respect to 1 mol of the surfactant was adjusted to about 2 to 20, respectively.

  Next, while stirring the reverse micelle solution A, the reverse micelle solution B was added and stirred for 1 hour, and then a solution 1 containing platinum particles in the reverse micelle was obtained.

  Further, while stirring the reverse micelle solution D, the reverse micelle solution C was added and stirred for 1 hour, and then a solution 2 having a pH of 8 to 9 containing the zirconia precursor in the reverse micelle was obtained.

  While stirring Solution 1, Solution 2 was added and stirred for 1 hour, and then Solution 3 containing platinum particles and zirconia hydroxide in reverse micelles was obtained. The solution 3 was added to the aluminum isopropoxide-dissolved cyclohexane solution while stirring, followed by stirring for 1 hour and further stirring and aging for 24 hours. As a result, an aluminum hydroxide supported by platinum particles and zirconia hydroxide was obtained.

Then, it centrifuged for 6 hours using the centrifuge (Hitachi Ltd. CENTRIFUGE05P-20B), isolate | separated precipitation, filtered, and wash | cleaned with ethanol and water. The obtained solid was dried at 85 ° C. under reduced pressure for 12 hours, pulverized in a mortar, calcined at 400 ° C. for 2 hours in an air circulation atmosphere, and further calcined at 600 ° C. for 5 hours to obtain a heat-resistant catalyst. It was. The heat-resistant catalyst contains precious metal fine particles (average particle size of Pt particles is 1.5 nm, Pt supported concentration is 5%) and zirconia fine particles (average particle size of ZrO ₂ particles is 20 nm, Zr supported concentration is 5%). Alumina particles (average particle size 100 nm). The results are shown in Table 1.

<Example 2>
Instead of reverse micelle solution B, powder of sodium borohydride 0.2g (equal molar amount of Pt) as a reducing agent was directly added to obtain aluminum hydroxide supported by platinum particles and zirconia hydroxide. In the same manner as in Example 1, noble metal fine particles (average particle size of Pt particles is 1.5 nm, Pt supported concentration is 5%) and zirconia fine particles (average particle size of ZrO ₂ particles is 20 nm, Zr supported concentration is 5%) ) -Containing alumina particles (average particle size 300 nm). The results are shown in Table 1.

<Example 3>
5 wt% cerium nitrate _{(Ce (NO 3) 3 ·} 6H 2 O) was added an aqueous solution 35.6g to give a reverse micelle solution D, except that the platinum particles and the cerium hydroxide to obtain an aluminum hydroxide carrying In the same manner as in Example 1, noble metal fine particles (average particle size of Pt particles is 2.0 nm, Pt supported concentration 5%) and cerium fine particles (average particle size of CeO ₂ particles is 15 nm, Ce supported concentration 5%. ) -Containing alumina particles (average particle size 200 nm) were obtained. The results are shown in Table 1.

<Example 4>
A reverse micelle solution D was obtained by adding 1.22 g of 97 mass% titanium tetraisopropoxide (Ti (OC ₂ H ₅ ) ₄ ) solution, and an aluminum hydroxide supported by platinum particles and titanium hydroxide was obtained. In the same manner as in Example 1, noble metal fine particles (average particle size of Pt particles is 3.5 nm, Pt supported concentration 5%) and titanium fine particles (average particle size of TiO ₂ particles is 15 nm, Ti supported concentration 5). %) Containing alumina particles (average particle size 150 nm). The results are shown in Table 1.

<Example 5>
Instead of the dinitrodiammine platinum aqueous solution, a rhodium nitrate aqueous solution (Rh concentration: 8% by mass) was added to obtain an aluminum hydroxide supported by rhodium particles and zirconia hydroxide. , Alumina particles (average) containing noble metal fine particles (Rh particles have an average particle size of 1.5 nm, Rh carrying concentration of 5%) and zirconia fine particles (ZrO ₂ particles have an average particle size of 20 nm, Zr carrying concentration of 5%) A heat-resistant catalyst having a particle size of 500 nm) was obtained.

<Example 6>
Instead of the dinitrodiammine platinum aqueous solution, a dinitrodiammine palladium aqueous solution (Pd concentration of 8% by mass) was added to obtain an aluminum hydroxide supported by palladium particles and zirconia hydroxide. , Alumina particles (average) containing noble metal fine particles (average particle size of Pd particles is 5.0 nm, Pd supported concentration 5%) and zirconia fine particles (average particle size of ZrO ₂ particles is 30 nm, Zr supported concentration 5%) A heat-resistant catalyst having a particle size of 300 nm was obtained.

<Comparative Example 1>
Reverse micelle solution A and reverse micelle solution B were prepared in the same manner as Example 1.

  Next, the reverse micelle solution B was added while stirring the reverse micelle solution A, and after stirring for 1 hour, a solution 1 containing platinum particles in the reverse micelle was obtained.

  While the solution 1 was stirred, an aluminum isopropoxide-dissolved cyclohexane solution was added and stirred for 1 hour, followed by further stirring and aging for 24 hours.

Then, it centrifuged for 6 hours using the centrifuge (Hitachi Ltd. CENTRIFUGE05P-20B), isolate | separated precipitation, filtered, and wash | cleaned with ethanol and water. The obtained solid was dried at 85 ° C. under reduced pressure for 12 hours, pulverized in a mortar, calcined at 400 ° C. for 2 hours in an air circulation atmosphere, and further calcined at 600 ° C. for 5 hours to obtain a heat-resistant catalyst. It was. This catalyst was alumina particles (average particle size 200 nm) containing noble metal fine particles (average particle size of Pt particles was 1.5 nm, Pt support concentration 5%). The results are shown in Table 1.

<Example 7>
Using 44 g of polyoxyethylene (5) nonylphenyl ether as a surfactant, cyclohexane was added to 1.0 L (0.1 mol / L), and this was mixed and stirred. To this, 10.0 g of dinitrodiammine platinum aqueous solution (Pt concentration 8.0 mass%) was added and stirred for 1 hour until it became transparent to prepare reverse micelle solution E.

  Using 44 g of polyoxyethylene (5) nonylphenyl ether as a surfactant, cyclohexane was added to 1.0 L (0.1 mol / L), and this was mixed and stirred. To this was added 13.2 g (0.5 times the molar amount of Pt) of a 0.5% by mass hydrazine aqueous solution as a reducing agent, and the mixture was stirred for 1 hour to obtain reverse micelle solution F.

  Using 44 g of polyoxyethylene (5) nonylphenyl ether as a surfactant, cyclohexane was added to 1.0 L (0.1 mol / L), and this was mixed and stirred. To this, 28.4 g of a 1.0 mass% aqueous ammonia solution as a precipitant was added and stirred for 1 hour until it became transparent to prepare a reverse micelle solution G.

Using 44 g of polyoxyethylene (5) nonylphenyl ether as a surfactant, cyclohexane was added to 1.0 L (0.1 mol / L), and this was mixed and stirred. To this, 21.9 g of a 5 mass% zirconium oxynitrate (ZrO (NO ₃ ) ₂ .2H ₂ O) aqueous solution was added and stirred for 1 hour until it became transparent, whereby a reverse micelle solution H was obtained.

  At this time, the molar ratio in the reverse micelle aqueous solution with respect to 1 mol of the surfactant was adjusted to about 2 to 20, respectively.

  Next, while stirring the reverse micelle solution E, the reverse micelle solution F was added and stirred for 1 hour, and then a solution 4 containing platinum particles in the reverse micelle was obtained.

  Furthermore, while stirring the reverse micelle solution H, the reverse micelle solution G was added and stirred for 1 hour, and then a solution 5 having a pH of 8 to 9 containing the zirconia precursor in the reverse micelle was obtained.

  While stirring Solution 4, Solution 5 was added and stirred for 1 hour, and then Solution 6 containing platinum particles and zirconia hydroxide in reverse micelles was obtained. This solution 6 was added to the aluminum isopropoxide-dissolved cyclohexane solution while stirring, followed by stirring for 1 hour and further stirring and aging for 24 hours. As a result, an aluminum hydroxide supported by platinum particles and zirconia hydroxide was obtained.

Then, it centrifuged for 6 hours using the centrifuge (Hitachi Ltd. CENTRIFUGE05P-20B), isolate | separated precipitation, filtered, and wash | cleaned with ethanol and water. The obtained solid was dried at 85 ° C. under reduced pressure for 12 hours, pulverized in a mortar, calcined at 400 ° C. for 2 hours in an air circulation atmosphere, further calcined at 600 ° C. for 5 hours, and then inert gas of argon A heat resistant catalyst was obtained by calcination at 600 ° C. for 2 hours in an atmosphere. The heat-resistant catalyst contains precious metal fine particles (average particle size of Pt particles is 2.5 nm, Pt supported concentration is 5%) and zirconia fine particles (average particle size of ZrO ₂ particles is 20 nm, Zr supported concentration is 5%). Alumina particles (average particle size 300 nm). The results are shown in Table 2.

<Example 8>
Instead of reverse micelle solution F, powder of sodium borohydride 0.2g (equal molar amount of Pt) as a reducing agent was directly added to obtain aluminum hydroxide supported by platinum particles and zirconia hydroxide. In the same manner as in Example 7, noble metal fine particles (average particle size of Pt particles is 3.0 nm, Pt supported concentration 5%) and zirconia fine particles (average particle size of ZrO ₂ particles is 20 nm, Zr supported concentration 5%) ) -Containing alumina particles (average particle size 300 nm). The results are shown in Table 2.

<Example 9>
5 wt% cerium nitrate _{(Ce (NO 3) 3 ·} 6H 2 O) was added an aqueous solution 35.6g to give a reverse micelle solution H, except that the platinum particles and the cerium hydroxide to obtain an aluminum hydroxide carrying In the same manner as in Example 7, noble metal fine particles (average particle size of Pt particles is 2.5 nm, Pt supported concentration is 5%) and cerium fine particles (average particle size of CeO ₂ particles is 20 nm, Ce supported concentration is 5%. ) -Containing alumina particles (average particle size 300 nm). The results are shown in Table 2.

<Example 10>
A reverse micelle solution H was obtained by adding 1.22 g of 97 mass% titanium tetraisopropoxide (Ti (OC ₂ H ₅ ) ₄ ) solution, and an aluminum hydroxide supported by platinum particles and titanium hydroxide was obtained. In the same manner as in Example 7, noble metal fine particles (average particle size of Pt particles is 3.5 nm, Pt supported concentration 5%) and titanium fine particles (average particle size of TiO ₂ particles is 20 nm, Ti supported concentration 5). %) Containing alumina particles (average particle size 300 nm). The results are shown in Table 2.

<Example 11>
Instead of the dinitrodiammine platinum aqueous solution, a rhodium nitrate aqueous solution (Rh concentration: 8% by mass) was added to obtain an aluminum hydroxide supported by rhodium particles and zirconia hydroxide. , Alumina particles (average) containing noble metal fine particles (average particle size of Rh particles is 2.0 nm, Rh supported concentration 5%) and zirconia fine particles (average particle size of ZrO ₂ particles is 20 nm, Zr supported concentration 5%) A heat-resistant catalyst having a particle size of 300 nm was obtained. The results are shown in Table 2.

<Example 12>
Instead of the dinitrodiammine platinum aqueous solution, a dinitrodiammine palladium aqueous solution (Pd concentration of 8% by mass) was added to obtain an aluminum hydroxide supported by palladium particles and zirconia hydroxide. , Alumina particles (average) containing noble metal fine particles (average particle size of Pd particles is 5.5 nm, Pd supported concentration of 5%) and zirconia fine particles (average particle size of ZrO ₂ particles is 20 nm, Zr supported concentration of 5%) A heat-resistant catalyst having a particle size of 300 nm was obtained.

<Evaluation>
The heat resistance of the catalyst was evaluated as follows.

  The catalysts obtained in Example 1 and Comparative Example 1 were calcined at each temperature for 2 hours while raising the temperature from 700 ° C. to 1300 ° C. in an air circulation atmosphere. The change in the BET specific surface area with respect to the change in the firing temperature at this time is shown in FIG. Thereby, even if a calcination temperature becomes high temperature, it turns out that the specific surface area where the direction of the catalyst of Example 1 is larger than the comparative example 1 is maintained.

  Next, after calcining the catalysts obtained in Examples 1 to 12 and Comparative Example 1 at 1000 ° C. for 10 hours, the average particle diameter of the noble metal was measured by X-ray analysis (XRD), and the obtained results were obtained. It shows in Table 1 and Table 2. FIG. 10 shows XRD diffraction patterns of the catalysts of Example 1 and Comparative Example 1. Accordingly, it can be seen that the catalyst of Example 1 has a small peak intensity and a small peak width, so that the particle diameter (crystallite diameter) of the Pt particles is small. On the other hand, the catalyst of Comparative Example 1 has a large peak intensity and a narrow peak width, so that it can be seen that the particle diameter (crystallite diameter) of the Pt particles is large.

  Therefore, it can be seen that the heat-resistant catalyst of the present invention has a noble metal and a metal oxide on the surface of the carrier, so that sintering is effectively suppressed and excellent heat resistance is exhibited.

Schematic diagram of a catalyst prepared by a conventional method with a noble metal adsorbed on the support surface The schematic diagram of the catalyst which the noble metal produced by the conventional method was buried in the support | carrier surface is shown. It is a schematic diagram of the heat resistant catalyst of this invention. It is the figure which showed the reverse micelle solution typically. It is a figure which shows the process of including a noble metal and a metal (L) hydroxide from the reverse micelle solution which includes a noble metal ion corresponding to Example 1, and the reverse micelle solution which includes a metal (L) hydroxide. is there. It is a figure which shows the process of including a noble metal and a metal (L) hydroxide from the reverse micelle solution which includes a noble metal ion, and the reverse micelle solution which includes a metal (L) hydroxide. It is a figure which shows the process of including a noble metal and a metal (L) hydroxide from the reverse micelle solution which includes a noble metal ion, and the reverse micelle solution which includes a metal (L) hydroxide. It is a figure which shows the process of including a noble metal and a metal (L) hydroxide from the reverse micelle solution which includes a noble metal ion, and the reverse micelle solution which includes a metal (L) hydroxide. The BET specific surface area with respect to the change of the calcination temperature of the catalyst obtained in Example 1 and Comparative Example 1 is shown. The XRD diffraction pattern of the catalyst of the catalyst obtained in Example 1 and Comparative Example 1 is shown.

Explanation of symbols

1 organic solvent,
2 surfactant,
3 hydrophilic groups,
4 Hydrophobic group,
5 Noble metal ion inclusion reverse micelle,
6 Reducing agent-containing reverse micelles,
7 reduced particles,
8 Noble metal colloid inclusion reverse micelle,
9 Metal (M) ion inclusion reverse micelle,
10 Reverse micelles containing precipitants,
11 Metal (M) hydroxide inclusion reverse micelle,
12 Noble metal colloid / metal (M) hydroxide inclusion reverse micelle,
101 carrier,
102 noble metal particles,
103 Metal (L) oxide.

Claims (16)

  A precious metal colloid prepared using the reverse micelle method, a metal (L) hydroxide prepared using the reverse micelle method, and a hydrolyzate of metal (M) alkoxide are mixed, and the resulting mixture is fired. Thus, a heat-resistant catalyst comprising a noble metal and a metal (L) oxide supported on the surface of the metal (M) oxide.   A reverse micelle solution containing a noble metal colloid aqueous solution inside the micelle, a reverse micelle solution containing a metal (L) hydroxide aqueous solution inside the micelle, and a metal (M) alkoxide are mixed, and the resulting mixture is baked. Thus, a heat-resistant catalyst comprising a noble metal and a metal (L) oxide supported on the surface of the metal (M) oxide.   The mixture includes a metal (M) hydroxide obtained by hydrolysis of a metal (M) alkoxide, the noble metal colloid, and the metal (L) hydroxide, and more preferably the metal (M) hydroxide than the metal (M) hydroxide. The method for producing a heat-resistant catalyst according to claim 1 or 2, wherein the water content of the metal (L) hydroxide is small.   The average particle diameter of the metal (L) oxide is R1, the average particle diameter of the metal (M) oxide is R2, and R2 / R1 = 2 to 100. The heat-resistant catalyst.   The heat-resistant catalyst according to claim 4, wherein R3 is an average particle diameter of the noble metal, and R1 / R3 = 1 to 50.   The said noble metal is 1 or more types of noble metals chosen from the group which consists of platinum, palladium, rhodium, osmium, ruthenium, and iridium, and an average particle diameter is 1-10 nm, In any one of Claims 1-5. Heat resistant catalyst.   The metal (L) is at least one metal selected from gallium, cerium, zirconium, vanadium, manganese, iron, cobalt, nickel, germanium, chromium, copper, zinc and tungsten, and the metal (L) oxide The heat resistant catalyst according to any one of claims 1 to 6, which has an average particle diameter of 10 to 50 nm.   The metal (M) is at least one metal selected from aluminum, silica, gallium, titanium, cerium, zirconium, vanadium, and tungsten (provided that the metal (L) and the metal (M) are not the same). ), The heat resistant catalyst according to claim 1, wherein the metal (M) oxide has an average particle size of 100 to 1000 nm.   Metal (L) water is added to a reverse micelle solution A containing a noble metal ion aqueous solution inside the micelle and a solution obtained by adding the reducing agent of the noble metal ion aqueous solution to the reverse micelle solution B containing metal (L) ions inside the micelle. A solution to which a precipitant that generates an oxide is added, and the mixed solution is mixed with a metal (M) alkoxide solution or reverse micelle C containing a hydrolyzate of metal (M) alkoxide to obtain a metal (M ) A method for producing a heat-resistant catalyst, comprising a step of supporting a noble metal and a metal (L) hydroxide on a hydrolyzate of alkoxide.   To the reverse micelle solution A containing a noble metal ion aqueous solution inside the micelle, a reducing agent of the noble metal ion aqueous solution is added, and then the reverse micelle solution B containing metal (L) ions inside the micelle is mixed with the solution, (L) adding a precipitating agent to form a hydroxide, and further mixing the solution with a metal (M) alkoxide solution or reverse micelle C containing a hydrolyzate of metal (M) alkoxide; A method for producing a heat-resistant catalyst, comprising a step of supporting a noble metal and a metal (L) hydroxide on a hydrolyzate.   A reverse micelle solution A containing a noble metal ion aqueous solution inside the micelle and a reverse micelle solution B containing a metal (L) ion aqueous solution inside the micelle are mixed, and a noble metal ion reducing agent is added to the mixture, A precipitant that generates the metal (L) hydroxide is added, and the solution is mixed with a metal (M) alkoxide solution or reverse micelle C containing a hydrolyzate of metal (M) alkoxide, and the metal (M ) A method for producing a heat-resistant catalyst, comprising a step of supporting a noble metal and a metal (L) hydroxide on a hydrolyzate of alkoxide.   A reverse micelle solution A containing a noble metal ion aqueous solution inside the micelle and a reverse micelle solution B containing a metal (L) ion aqueous solution inside the micelle are mixed to produce a metal (L) hydroxide in the mixed solution. A precipitant is added, then a reducing agent for the noble metal ions is added, and the solution is mixed with a metal (M) alkoxide solution or reverse micelle C containing a hydrolyzate of metal (M) alkoxide to obtain a metal (M ) A method for producing a heat-resistant catalyst, comprising a step of supporting a noble metal and a metal (L) hydroxide on a hydrolyzate of alkoxide.   A reverse micelle containing a noble metal ion aqueous solution inside the micelle is added to the reverse micelle solution B containing the metal (L) ion aqueous solution inside the micelle, and then the precipitating agent that generates the metal (L) hydroxide is added to the solution. The solution A is mixed, the noble metal ion reducing agent is added, and the solution is further mixed with the metal (M) alkoxide solution or the reverse micelle C containing the hydrolyzate of the metal (M) alkoxide to obtain the metal (M). A method for producing a heat-resistant catalyst, comprising a step of supporting a noble metal and a metal (L) hydroxide on a hydrolyzate of an alkoxide.   The method for producing a heat-resistant catalyst according to any one of claims 9 to 13, wherein a water content of the metal (L) hydroxide is smaller than that of the metal (M) hydroxide.   Separating the hydrolyzate of the metal (M) alkoxide carrying the noble metal and the metal (L) hydroxide from the solution, washing, drying, and then baking at 400 to 800 ° C; The manufacturing method of the heat-resistant catalyst in any one of Claims 9-14 containing.   The method for producing a heat-resistant catalyst according to claim 15, wherein the calcination is further performed in an inert gas atmosphere.

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