JP3373723B2 - Method for producing noble metal-containing composite oxide catalyst - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the production of a noble metal-containing composite oxide catalyst, and more particularly to a cost-effective noble metal-containing composite oxide catalyst having improved collection efficiency and improved durability and catalytic properties. A method of manufacturing advantageously.

[0002]

2. Description of the Related Art Conventionally, noble metals such as platinum, palladium and rhodium have been used alone or in combination as catalyst components in exhaust gas purifying catalysts for automobiles and the like.
Usually, it is configured to be supported on a catalyst carrier. However, of these, rhodium is not abundant in resources and is expensive in terms of price. Although palladium is superior in heat resistance to platinum, it is significantly inferior in poisoning resistance to lead in gasoline and phosphorus in lubricating oil. Therefore, platinum, which has more resources than rhodium, is an essential component.

However, there is a problem that platinum is oxidized in a lean atmosphere at a high temperature and the surface area is reduced due to sintering and the activity as a catalyst component is remarkably lowered. Furthermore, exhaust gas temperature rises in response to the tightening of exhaust gas regulations such as the European Step III regulation and λ = 1 regulation, so that improvement in heat resistance of the catalyst is required. In the current Pt / Al ₂ 0 ₃ catalyst was reduced significantly purification performance in lean atmosphere at high temperatures, can not satisfy this.

The present inventor has proposed in Japanese Patent Application No. 7-184134 that an alkaline earth metal or IIIA is used as an exhaust gas purifying catalyst.
We have proposed highly heat-resistant complex oxides composed of group elements.
A sol-gel method is known as a method for producing these composite oxides. However, when a complex oxide containing a noble metal is produced by the sol-gel method, a thick sol of metal oxide or hydroxide is converted into a gel, which is dried and then calcined to obtain an oxide. Therefore, it is necessary to use a noble metal complex or a metal alkoxide. In addition, a treatment in a degreasing furnace is required before drying (especially at the time of mass synthesis), and these treatment costs are usually very expensive. Therefore, there is a demand for a more inexpensive method for producing a composite oxide.

[0005]

An object of the present invention is to investigate a cost-effective production method as an alternative to the sol-gel method,
It is an object of the present invention to provide a method for producing a noble metal-containing composite oxide catalyst, which makes it possible to make the composite oxide finer and improve the collection efficiency. Another object of the present invention is to study the formation of fine particles of the above complex oxide, to spray and burn a suspension or emulsion of the catalyst oxide, and to improve the collection efficiency and to recover the powder. A method for producing a noble metal-containing composite oxide catalyst. Furthermore, another object of the present invention is to improve collection efficiency of the fine particles,
It is an object of the present invention to provide a production method for directly obtaining a noble metal-containing composite oxide catalyst by supplying fine particles to a fluidized bed together with a carrier gas and adsorbing to the carrier particles in the fluidized bed.

[0006]

[Means for Solving the Problems] The above-mentioned object is a suspension prepared by suspending a raw material containing a noble metal and other metals which are components of a noble metal-containing composite oxide in a flammable liquid, or dissolving the above raw material in a solvent. It is achieved by a method for producing a noble metal-containing complex oxide catalyst, which comprises preparing an emulsion in which the obtained solution is emulsified in a flammable liquid, and spray-burning the suspension or the emulsion in an atmosphere containing oxygen. . The above object is also achieved by a method for producing a noble metal-containing composite oxide catalyst, which is characterized in that the noble metal-containing composite oxide obtained as a result of the spray combustion is guided and adsorbed on a catalyst carrier.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an inexpensive precious metal aqueous solution or the like can be used without using an expensive precious metal complex or metal alkoxide, so that the cost can be reduced. The purification performance and durability of the obtained catalyst are equivalent to those of the sol-gel method. Further, in order to suppress the reaction between the noble metal-containing composite oxide catalysts, it is effective to mix with a catalyst carrier,
In the present invention, it is not necessary to mix it with a carrier later, and a practical catalyst can be obtained by a series of steps. Also, the yield is improved by adsorbing it on the carrier.

The raw material containing a noble metal and other metals may be those metal elements or metal salts. Examples of the flammable liquid include oils such as kerosene, kerosene, and gasoline. To make a suspension, a raw material containing the above noble metal and other metals is suspended in a flammable liquid. On the other hand, in order to prepare an emulsion, the raw materials containing the above-mentioned precious metals and other metals are dissolved in a solvent to form a solution, and the solution is emulsified in a flammable liquid. Examples of the solvent for preparing the emulsion include water and organic solvents. To emulsify the solution in a flammable liquid,
Add emulsifier.

Further, as an emulsion, a solution in which the above raw material is dissolved in a solvent in a flammable liquid becomes turbid, and the above raw material is suspended in the flammable liquid, that is, an emulsion state and a suspension state coexist. What you do can also be used. The atmosphere in which the suspension or emulsion is sprayed and burned is an atmosphere containing oxygen. As a method of spraying the suspension or emulsion in this atmosphere, a method of spraying the suspension or emulsion with an oxygen-containing gas,
Alternatively, there is a method of spraying the suspension or emulsion in an atmosphere (gas) in which oxygen exists. Among them, the method of spraying the suspension or emulsion together with the oxygen-containing gas has higher reaction efficiency and is preferable.

An example in which an aqueous solution of a noble metal or other metal, which is a component of a noble metal-containing composite oxide, is mixed with oil and an emulsifier to prepare an emulsion, and the emulsion is spray-burned in an atmosphere containing oxygen (emulsion combustion method) )
Will be described. In this emulsion combustion method, particularly inexpensive noble metal aqueous solution or the like can be used, so that the cost can be further reduced.

In the emulsion combustion method of the present invention, as shown in FIG. 1, in the emulsion preparation step of FIG. 1 (a), a noble metal oxide raw material metal salt solution (A,
Solution B), an oil immiscible therewith, and an emulsifier as a stabilizer are further added, and the mixture is stirred by the stirrer 1 to form a dispersion system. Next, a homogenizer is used to emulsify to form an emulsion having a substantially uniform dispersity. At this time, the emulsion particle size is adjusted to be 1 to 30 μm. As the emulsifier, an anionic activator or a nonionic activator that does not cause aggregation of the dispersed particles is preferably selected so that agglomeration of dispersed particles does not occur. The emulsifier may be one that reduces the interfacial tension between the dispersed particles and the solution as much as possible and has a function as a protective film. More preferably, the emulsifier should be an activator that forms a complex compound at the interface. Good. Further, the amount of the emulsifier may be an amount suitable for sufficiently covering the surface of the dispersed particles as a monomolecular layer. In the emulsion obtained in this step, the metal salt aqueous solution 8 and the oil 9 are uniformly dispersed, as shown in FIG.

Next, this emulsion is shown in FIG.
Spray the emulsion as shown and feed to the burning process
To do. The chamber 7 is provided with a sprayer 2 and a burner 4.
As shown in FIG. 2 (b), the emulsion is sprayed by the atomizer 2
From N as carrier gas ₂Atomized with gas etc.
Be done. At this time, the emulsion particles are metal covered with oil 9.
It becomes atomized particle spray 3 consisting of salt solution 8 and
It is blown to the ram 5 and burns. The combustion burner 4
O for combustion of emulsion particles₂Supply hydrogen
Flow-through or batch using synthetic fuel to generate
Type combustion furnace may be used, and the flame temperature is preferably about
Any material that generates a high temperature of about 2000 ° C. may be used.

In the present invention, atomized particles of an emulsion covered with oil such as kerosene are sprayed into the flame and the particles themselves are burned. Therefore, once the particles themselves are ignited, they form an oil film of their own. Burning is triggered. Due to this heat generation, the aqueous metal salt solution inside the atomized particles exposed to high temperature is thermally decomposed into a molecular state to cause a synthetic reaction to form a nucleus. After that, nucleation and growth processes are repeated during cooling, and fine particles of complex oxide (1 μm
The powder 6 is produced as Since the powder 10 according to the present invention shown in FIG. 2 (c) utilizes the above-mentioned synthesis reaction in the gas phase, it is relatively easy to control the crystallinity and the particle size of the produced powder, and the catalyst property has a high non-surface area. A powder having a spherical shape and crystal stability is obtained. Furthermore, in the method of the present invention, by controlling the combustion characteristics of the emulsion spray, particularly the thermal decomposition reaction by increasing the temperature and adjusting the chamber atmosphere, the resulting powder has excellent crystallinity and stability of the complex oxide. Enables manufacturing.

Next, a method of collecting fine particles of the complex oxide of the present invention will be described. FIG. 3 shows a fluidized bed as a device for collecting fine particles of the present invention. In this figure, from the bottom, the fine particles are blown up together with the carrier gas from the fine particle / carrier gas supply pipe 13 as a fluid under the control of the flow rate controller 19, and the carrier particles 11
Form a fluidized bed. At this time, the carrier particle diameter of the heat medium is
It is preferably 0.5 to 5 mmφ. In the fluidized bed, the heat transfer is good due to the violent collision with the wall surface, and as the external cooling, the cooling water inlet 16 and the cooling water outlet 17 are provided in the fluidizing device 12 to pass the circulating water. Room temperature water is usually sufficient to sufficiently cool the fine particles in the fluidizer 12, but ice water or an organic refrigerant may be used if necessary. By this cooling, the fine particles are adsorbed and collected on the carrier particles while repeatedly contacting the carrier particles. In this step, the carrier and the fine particles of the composite oxide are uniformly collected in the form of a catalyst.

At this time, in order to maintain the fluid state, it is necessary to continuously supply an appropriate amount of carrier gas from the lower portion, and when the amount of carrier gas is insufficient, buffer gas is additionally supplied. Therefore, or when the adsorption of fine particles is insufficient, an additional carrier gas supply or recirculation pipe 14 is provided to recirculate and improve the collection rate.
Are provided in parallel. Cooling may be facilitated by cooling this additional carrier gas.

The opening and closing of the supply port at the start and end of the flow state are performed by the vertical movement of the iron ball 15 due to the fluid flow. The present apparatus may be provided in a plurality or in multiple stages, and when cooling is insufficient, another coil cooling tube may be provided inside the layer. In the above ultrafine particle collection of the present invention,
How efficiently the carrier gas containing ultrafine particles is cooled is important, and the fluidized bed is extremely excellent as a heat exchange device for this purpose. Conventionally, it is considered that the fluidized bed was not applied as an ultrafine particle collecting device because it required a new step for separating the heat medium and the collected ultrafine particles. In the present invention, it is not necessary to separate the collected ultrafine particles and the heat medium (carrier oxide), and the effect of improving the collection efficiency can be maximized. In the conventional method of collecting fine particles by causing a carrier gas containing fine particles to collide with a metal baffle plate, the collection efficiency was far below 50% when the particle size was 1 μm or less. On the other hand, in the above-described production method of the present invention, the efficiency of collecting fine particles as a catalyst is improved, 70% or more of particles having a particle size of 1 μm or less can be collected, and the amount of fine particles produced is required. Calculated from the amount and loading and easily controlled. Examples of the present invention will be described below.

[0017]

【Example】

Example 1 In this example, Ba ₄ PtO ₆ / Al ₂ O ₃ (Ba ₄ PtO) is used.
₆ is for the emulsion combustion method). 37.3 g of Ba (NO ₃ ) ₂ was dissolved in 200 g of ion-exchanged water to obtain a solution A1. A solution B1 was prepared by adding 174 g of a 4 wt% dinitrodiammine Pt nitric acid aqueous solution to the solution A1. 180 g of kerosene and 7.2 g of sorbitan monolaurate (surfactant) were added to the solution B1 to prepare a solution C1. The solution C1 was mixed with a homogenizer for 10 minutes to prepare an emulsion solution D1.

The emulsion solution D1 was introduced by a liquid pump into a flow type combustion furnace equipped with a sprayer. 10 l / min of nitrogen (carrier) and about 20 l / min of oxygen (for combustion) were introduced into the combustion furnace. The combustion temperature was set to 1100 ° C. by adjusting the supply amount of the solution D1 and the oxygen supply amount. The produced complex oxide powder E1 was collected by a stainless steel baffle plate and a paper filter provided downstream of the combustion furnace. 5.31 g of powder E1 and 94.61 g of γ-Al ₂
The catalyst of Example 1 was obtained by thoroughly mixing O ₃ in a mortar.

Example 2 In this example, Sr ₂ PtO ₆ / Al ₂ O ₃ (Sr ₄ PtO) was used.
₆ is for the emulsion combustion method). 37.3 g of Ba (NO ₃ ) ₂ was dissolved in 200 g of ion-exchanged water to obtain a solution A2. 174 g of a 4 wt% dinitrodiammine Pt nitric acid aqueous solution was added to the solution A2 to prepare a solution B2. 180 g of kerosene and 7.2 g of sorbitan monolaurate (surfactant) were added to the solution B2 to prepare a solution C2. The solution C2 was mixed with a homogenizer for 10 minutes to obtain an emulsion solution D2. Emulsion solution D2
Was introduced by a liquid pump into a flow-type combustion furnace equipped with a sprayer. 10 l / min nitrogen (carrier) in the combustion furnace
And about 20 l / min of oxygen (for combustion) was introduced. Solution D
The combustion temperature is adjusted to 1150 by adjusting the supply amount of 2 and the oxygen supply amount.
℃ was made. The produced complex oxide powder E2 was collected by a stainless steel baffle and a paper filter provided downstream of the combustion furnace. 4.11 g of powder E2 and 95.8
Example catalyst 2 was obtained by thoroughly mixing 9 g of γ-Al ₂ O ₃ in a mortar.

Comparative Example 1 In this comparative example, Ba ₄ PtO ₆ / Al ₂ O ₃ (Ba ₄ Pt)
O ₆ is for synthesis by sol-gel method). 20
g of PtCl ₄ is dissolved in 200 g of ethanol to prepare a solution O
It was set to 1. 40 g of an ethanol solution (10 wt%) of Na ethoxide C ₂ H ₅ ONa was added to the solution O1 and the mixture was refluxed for another 5 hours to obtain a Pt alkoxide solution. Solution P1 to B
a Ethanol solution (10 wt%) of ethoxide Ba (OC ₂ H ₅ ) ₂ (541 g) was added to prepare a solution Q1. Ion-exchanged water (120 g) was added to the solution Q1 to obtain a precipitate. After drying and degreasing at 200 ° C for one day in a nitrogen atmosphere, 1000
Firing at 5 ° C. for 5 hours gave powder R1. 5.31g of R1
The powder and 94.61 g of γ-Al ₂ O ₃ were mixed well in a mortar to obtain Comparative Example Catalyst 1.

Comparative Example 2 In this comparative example, Sr ₄ PtO ₆ / Al ₂ O ₃ (Sr ₂ Pt)
O ₆ is for synthesis by sol-gel method). 20
g of PtCl ₄ is dissolved in 200 g of ethanol to prepare a solution O
It was set to 2. 40 g of an ethanol solution of Na ethoxide C ₂ H ₅ ONa (10 wt%) was added to the solution O2, and the mixture was refluxed for another 5 hours to obtain a Pt alkoxide solution. S in solution P2
A solution Q2 was prepared by adding 423 g of an ethanol solution (10 wt%) of r ethoxide Sr (OC ₂ H ₅ ) ₂ . Ion-exchanged water (120 g) was added to the solution Q1 to obtain a precipitate. After drying and degreasing at 200 ° C for one day in a nitrogen atmosphere, 1000
Firing at 5 ° C. for 5 hours gave powder R2. 5.31g of R2
The powder and 94.61 g of γ-Al ₂ O ₃ were thoroughly mixed in a mortar to obtain a comparative catalyst 2.

When X-ray diffraction analysis was conducted on the above-mentioned catalysts of the examples and comparative catalysts, no diffraction peak of Pt metal was observed in any of the catalysts. The performance evaluation method will be described below. CIP (normal temperature isostatic press) for the above catalyst
After pressurizing, it was crushed and molded into 1.7 to 1.0 mm. Prior to the performance evaluation, a durability treatment was performed at 1000 ° C. for 10 hours. Table 1 shows the composition of the durable processing gas (corresponding to A / F = 16).

[0023]

[Table 1]

Next, the purification rate was measured using an atmospheric pressure flow reactor. Table 2 shows the purification rate measurement gas composition (corresponding to stoichiometry).

[0025]

[Table 2]

The flow rate of the purification rate measurement gas at this time is 5 L / mi
n. The catalyst weight is 2.0 g (Pt weight: 0.025
g = 2 × 0.0125). Each catalyst bed temperature is 500
℃, 450 ℃, 400 ℃, 350 ℃, 300 ℃, 250
The purification rate in a steady state was measured at each temperature as ° C. The definition of purification rate is as follows. Purification rate = [(inlet gas concentration-outlet gas concentration) / inlet gas concentration] × 100 Next, a temperature at which the purification rate is 50% by plotting the catalyst bed temperature and the purification rate (THC-T50 <C ₃ H ₆ component >, NO
-T50 <noted as NO component>) was determined. The results are summarized in Table 3.

[0027]

[Table 3]

From Table 3, it can be seen that the implemented catalyst has a purification performance comparable to that of the comparative catalyst.

Example 3 In this example, fine particles produced by emulsion combustion were directly adsorbed and collected on a carrier oxide by a fluidized bed. Regarding Ba ₄ PtO ₆ / Al ₂ O ₃ (Ba ₄ PtO ₆ was synthesized by the emulsion combustion method), 37.3 g of Ba (NO ₃ ) ₂ was dissolved in 200 g of ion-exchanged water to obtain a solution A1. A solution B1 was prepared by adding 174 g of a 4 wt% dinitrodiammine Pt nitric acid aqueous solution to the solution A1. 180 g of kerosene and 7.2 g of sorbitan monolaurate (surfactant) were added to the solution B1 to prepare a solution C1. The solution C1 was mixed with a homogenizer for 10 minutes to prepare an emulsion solution D1. The emulsion solution D1 was introduced by a liquid pump into a flow-type combustion furnace equipped with a sprayer. 10 l / min nitrogen (carrier) and about 20 l / min in the combustion furnace
Oxygen (for combustion) was introduced. The combustion temperature was set to 1100 ° C. by adjusting the supply amount of the solution D1 and the oxygen supply amount. 470
The oxide powder F1 was recovered by a collector using g of γ-Al ₂ O ₃ as a fluidized bed. After the powder synthesis was completed, the oxide powder H1 attached to the furnace was collected and was collected in the above-mentioned γ-Al ₂ O ₃
To obtain an example catalyst.

Furthermore, Sr ₂ PtO ₆ / Al ₂ O
_{For 3} (Sr ₄ PtO ₆ was synthesized by emulsion combustion method), 37.3 g of Ba (NO ₃ ) ₂ was dissolved in 200 g of ion-exchanged water to obtain a solution A2. 174 g of a 4 wt% dinitrodiammine Pt nitric acid aqueous solution was added to the solution A2 to prepare a solution B2. 180 g of kerosene and 7.2 g of sorbitan monolaurate (surfactant) were added to the solution B2 to prepare a solution C2. The solution C2 was mixed with a homogenizer for 10 minutes to obtain an emulsion solution D2. The emulsion solution D2 was introduced by a liquid pump into a flow-type combustion furnace equipped with a sprayer. 10 l / min of nitrogen (carrier) and about 20 l / min of oxygen (for combustion) were introduced into the combustion furnace. The combustion temperature is adjusted to 11 by adjusting the supply amount of the solution D2 and the oxygen supply amount.
It was set to 50 ° C.

Oxide powder F2 was recovered by a collector using 1050 g of γ-Al ₂ O ₃ as a fluidized bed. After the completion of the powder synthesis, the oxide powder H2 adhering to the furnace was recovered and mixed with the γ-Al ₂ O ₃ to obtain the catalyst of the example.
The comparative catalyst was produced by the sol-gel method,
It is the same as the comparative catalyst 1 and the comparative catalyst 2. In the same manner as described above, the performance evaluation method was also carried out by pressing the above catalyst with a CIP (normal temperature isostatic press), crushing it, and molding it into 1.7 to 1.0 mm. 10 before performance evaluation
Durability treatment was performed at 00 ° C. for 10 hours. The composition of the durable processing gas (corresponding to A / F = 16) is the same as in Table 1 above. Next, the purification rate was measured using an atmospheric pressure flow reactor. As a result, it was found that the applied catalyst of the example has the same purification performance as that of the comparative catalyst.

[0032]

The method for producing the composite oxide catalyst of the present invention comprises:
Since it is synthesized by the method of burning the suspension or emulsion, it is cost-effective. Among them, the use of an emulsion is more cost effective. Further, by combining the method of burning the suspension or emulsion with the collection by the fluidized bed, the collection efficiency of the oxide fine particles is improved, and the composite oxide is directly adsorbed on the carrier oxide. Can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of an emulsion combustion method according to the present invention.

FIG. 2 shows states of the emulsion combustion method according to the present invention, which are (a) emulsion state, (b) emulsion spray state, and (c) powder state.

FIG. 3 is a diagram showing an outline of a fluidized bed for collecting the synthesized fine particles according to the present invention.

[Explanation of symbols]

1 ... Stirrer 2 ... atomizer 3 ... Spray 4 ... Burner 5 ... frame 6 ... powder 7 ... Chamber 8 ... Metal salt aqueous solution 9 ... oil 10 ... powder 11 ... Carrier particles 12 ... Fluidized bed equipment 13 ... Ultra fine particles, carrier gas supply pipe 14 ... Additional carrier gas supply or recirculation pipe 15 ... Iron balls 16 ... Cooling water inlet 17 ... Cooling water outlet 18 ... Exhaust or recirculation 19 ... Flow controller

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Sugiyama 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kazuma Takatori 1 in 41, Yokoshiro, Nagakute, Aichi-gun, Aichi Prefecture Toyota Central Research Institute Co., Ltd. (72) Inventor Naoyoshi Watanabe Nagachite, Aichi-gun, Aichi-gun, Nagakage-Yokohama No. 41 No. 1 at Toyota Central Research Institute Co., Ltd. No. 41 1 Toyota Central Research Institute Co., Ltd. (56) Reference JP-A-63-12353 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01J 21/00-37/36

Claims (2)

(57) [Claims] 1. A suspension obtained by suspending a raw material containing a noble metal and other metals, which are components of a noble metal-containing composite oxide, in a flammable liquid, or a solution obtained by dissolving the above raw material in a solvent, in a flammable liquid. A method for producing a noble metal-containing composite oxide catalyst, which comprises producing an emulsified emulsion, and spray-burning the suspension or emulsion in an atmosphere containing oxygen. 2. A method for producing a noble metal-containing composite oxide catalyst, which comprises introducing and adsorbing a noble metal-containing composite oxide obtained as a result of spray combustion on a catalyst carrier according to claim 1.