JPH09221304A - Oxide solid solution particle and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an oxide solid solution particle high in oxygen storage ability, small in the average particle diameter of a crystallite and large in specific surface are by heating a precipitate obtained by adding a surfactant and an alkaline material into an aq. solution, in which Ce and Zr and dissolved. SOLUTION: An aq. solution is prepared by mixing cerium (III) nitrate and zirconium nitrate so as to have the molar ratio of Ce/Zr=5/5 and is neutralized to form a precipitate by dropping an ammoniacal liquor while stirring. Successively a hydrogen peroxide solution containing hydrogen peroxide of 1/2mol of Ce ion contained in the mixed solution and an aq. solution containing 10% alkyl benzene sulfonic acid by weight per an oxide to be obtained are added and mixed while stirring. The resultant slurry is sprayed in an atmosphere of 400 deg.C introduced air temp. and 250 deg.C discharged air temp. to be dried by a spray drying method and coexisting ammonium nitrate is vaporized or decomposed to prepare a powder containing the oxide solid solution. The degree of the solid solution is 100%, the average particle diameter is 10nm and the specific surface area is 45m<2> /g.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to oxide solid solution particles and a method for producing the same. Examples of the oxide solid solution of the present invention include solid solutions of cerium oxide (hereinafter referred to as ceria) and zirconium oxide (hereinafter referred to as zirconia). In this case, oxygen storage / exhaust capacity (oxygen storage capacity) by ceria is exemplified. Therefore, it is useful as a co-catalyst for an exhaust gas purifying catalyst. In addition to the above, the oxide solid solution of the present invention can be used for a diesel particulate oxidation catalyst, a solid electrolyte, an electrode material, ceramics dispersion strengthening particles, an ultraviolet shielding material and the like.

[0002]

2. Description of the Related Art Ceria, which has an oxygen storage capacity (oxygen storage / release capacity), is widely used as a cocatalyst for an exhaust gas purification catalyst for purifying exhaust gas from an internal combustion engine. Further, since it is desirable to increase the specific surface area in order to enhance the oxygen storage capacity, ceria is used in the powder state.

However, the exhaust gas purifying catalyst is required to be used at a high temperature and have a high purifying activity at a high temperature. Therefore, it is required for ceria that even if it is used as a powder with a high specific surface area, the specific surface area does not decrease when it is used at high temperatures, that is, it has excellent heat resistance. Therefore, it has been conventionally proposed to dissolve ceria with an oxide of a rare earth element other than zirconia and cerium.

For example, Japanese Patent Application Laid-Open No. 4-55315 discloses
A method for producing fine cerium oxide powder is disclosed in which ceria and zirconia are co-precipitated from a mixed aqueous solution of a water-soluble salt of cerium and a water-soluble salt of zirconium, and heat treatment is performed. According to this manufacturing method, by heat-treating the coprecipitate, cerium and zirconium become oxides, and an oxide solid solution is formed as a solid solution with each other.

Japanese Patent Application Laid-Open No. 4-284847 discloses that
It has been shown to produce a powder in which an oxide of zirconia or a rare earth element and ceria are solid-dissolved by an impregnation method or a coprecipitation method.

[0006]

However, according to the studies by the present inventors, the oxide solid solution produced by the method disclosed in the above publication has excellent heat resistance but sufficient oxygen storage capacity. It became clear that it is not. That is, the pH of the aqueous solution that precipitates with cerium and zirconium
, The composition of the coprecipitate becomes non-uniform by the method of coprecipitating from the mixed aqueous solution, and almost no solid solution occurs at the coprecipitate stage. Further, in the impregnation method, there are a method of impregnating the ceria powder with an aqueous solution containing a zirconium salt and a method of impregnating the zirconia powder with an aqueous solution of a cerium salt. The composition in the whole becomes non-uniform, and solid solution is difficult to promote.

Therefore, in both methods, a solid solution is caused by heat treatment. The coprecipitation method and the impregnation method perform heat treatment at temperatures of 500 to 900 ° C. and 700 to 1200 ° C., respectively, but the solid solution is not sufficient. In both methods, a neck is formed between the particles by heat treating the powder, and the solid solution is promoted by the neck, but the specific surface area of the powder is reduced because grain growth and sintering are promoted, and the crystal The particle size of the offspring also increases. Further, it is difficult to easily crush solid solution particles that have once grown into large particles.

For example, the solid solution obtained by the production method disclosed in Japanese Patent Application Laid-Open No. 4-55315 has a solid solubility of at most 40.
%. Further, according to the method disclosed in JP-A-4-284847, only a solid solubility of 20% or less can be obtained. In such a conventional ceria-zirconia-based oxide solid solution having a low solid solubility, the oxygen storage capacity (hereinafter referred to as OSC) of ceria is 100 to 150 μmolO at most.
_It is as small as about ₂ / g, and unless it is at a high temperature of 500 ° C. or higher, the oxygen storage / release capacity is not sufficiently expressed, and the oxygen storage capacity is low.

If the heat treatment is sufficiently performed at about 1600 ° C., the solid solution of ceria and zirconia has a solid solubility of about 100.
It is known to be%. However, in this case, the OS
Although C is high, the average particle size of the crystallite is 1000 nm or more, and the specific surface area becomes small, so transient oxygen storage
The release rate is limited by the small specific surface area, and is not practical as a promoter.

The present invention has been made in view of the above circumstances. By increasing the solid solubility, the performance as a solid solution such as oxygen storage capacity is enhanced, and the crystallite has a small average diameter and a large specific surface area. It is an object of the present invention to provide an oxide solid solution particle having: and a manufacturing method capable of easily and reliably manufacturing the solid solution particle.

[0011]

The features of the oxide solid solution particles of the present invention as set forth in claim 1 for solving the above problems are particles containing an oxide solid solution in which one oxide is in solid solution with another oxide. The solid solubility of one oxide in the particle is 50% or more, and the average diameter of the crystallite in the particle is 1
It is to be less than 00 nm.

It is desirable that the oxide solid solution particles are used as particles (powder) formed by assembling particles as described in claim 2. The oxide solid solution particles are
As described in claim 3, it is desirable that the specific surface area of the particles is 1 m ² / g or more. The oxide solid solution particles of the present invention according to claim 4 are particles containing an oxide solid solution in which ceria contains zirconia as a solid solution, and the solid solubility of zirconia to ceria in the particles is 50% or more. The average diameter of the crystallites in the particles is 100 nm or less.

As described in claim 5, the ratio of cerium to zirconium in the particles is 0.25≤mole.
It is desirable that Zr / (Ce + Zr) ≦ 0.75. Further, in the oxide solid solution particles of the present invention, one or more of an oxide of an alkaline earth element or an oxide of a rare earth element other than cerium is an oxide solid solution in which ceria and zirconia are solid-solved with each other. Further, the particles contain a solid solution of an oxide solid solution, wherein at least one (M) of an oxide of an alkaline earth element or an oxide of a rare earth element other than cerium is present in a molar ratio with respect to ceria and zirconia in the particles. It is preferable that 0 <M / (Ce + Zr + M) ≦ 0.15, and that the average crystallite diameter is 10 nm or less.

The average diameter of the crystallites of the oxide solid solution particles is preferably 10 nm or less, and the specific surface area is 20 m ² / g or more, further 50.
More preferably, it is m ² / g or more. Further, the feature of the production method of the present invention according to claim 6 for producing the oxide solid solution particles is that a precipitate is obtained by adding a surfactant and an alkaline substance to an aqueous solution in which a plurality of types of oxide elements are dissolved. In the first step, the precipitate is heated to obtain a particle containing an oxide solid solution in which one oxide is in solid solution with another oxide, and the solid solubility of the other oxide with respect to the one oxide in the particle. Is 50% or more, and the average diameter of crystallites in the particles is 10
A second step of obtaining oxide solid solution particles of 0 nm or less;
Is to become.

In the above-mentioned manufacturing method of the present invention, as described in claim 7, it is desirable that the elements to be oxides are tetravalent cerium and zirconium. When trivalent cerium is used as a starting material, as described in claim 8, hydrogen peroxide is added to the aqueous solution in which the trivalent cerium salt and the zirconium salt are dissolved in the first step, and the surface active agent. A precipitate is obtained by adding the agent and the alkaline substance, and the second step is performed in the same manner as in the above-mentioned manufacturing method.

In the above-mentioned manufacturing method of the present invention,
As described in claim 9, the surfactant preferably has a critical micelle concentration of 0.1 mol / liter or less. The shape of the micelle formed by the surfactant is preferably spherical and has a narrow space inside.
Furthermore, the feature of the manufacturing method of the present invention according to claim 10 is that 10 ³ se of an aqueous solution in which a plurality of kinds of elements to be oxides are dissolved.
The first step of obtaining a precipitate by adding an alkaline substance while stirring at a high shear rate of c ^-1 or higher and an oxidation in which one oxide is solid-dissolved with another oxide An oxide solid solution particle having a solid solution, wherein the solid solubility of one oxide in the particle is 50% or more, and the average diameter of crystallites in the particle is 100 nm or less. And the second step of obtaining. Also in that case, it is more effective if a surfactant is added to the aqueous solution in the first step.

Further, the feature of the manufacturing method of the present invention according to claim 11 is that the first step of obtaining a precipitate by adding an alkaline substance to an aqueous solution in which a plurality of kinds of oxide elements are dissolved, and the reduction of the precipitate Particles containing an oxide solid solution in which one oxide is solid-solved with another oxide when heated in an atmosphere, and the solid solubility of the other oxide with respect to one oxide in the particle is 5
0% or more and the average diameter of the crystallites in the particles is 100
The second step is to obtain oxide solid solution particles having a size of nm or less.

The average particle diameter of the crystallites of the oxide solid solution particles produced in claims 6 to 11 is more preferably 10 nm or less, and the specific surface area is 20 m ² / g or more, further 50 m ² / g. The above is more desirable.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The solid solubility refers to a value defined by the following equation. Solid solubility (%) = 100 × (amount of oxide B dissolved in the total amount of oxide A) / total amount of oxide B Here, oxide B dissolved in the total amount of oxide A is oxide A
Is assumed to be uniformly dissolved with respect to the total amount of

For example, in the case of a solid solution of ceria and zirconia, ceria corresponds to oxide A and zirconia corresponds to oxide B.
The solid solubility (%) is represented by 100 × (amount of zirconia dissolved in the total amount of ceria) / total amount of zirconia (1). Here, there is a relationship of equation (2) between the zirconia concentration x (mol%) of the ceria-zirconia solid solution (solid solubility 100%) and the lattice constant a (angstrom).

X = (5.423-a) /0.003 (2) This was derived as follows. When the lattice constant is measured by performing the same preparation as in Example 1 described later while increasing the amount of the surfactant in the mixing ratio of each ceria and zirconia, the value of the lattice constant is asymptotic to a certain value. An example of the composition of ceria / zirconia = 5/5 is shown in FIG. This is performed for each composition, and the lattice constant obtained in the region where the amount of surfactant is large is plotted against the zirconia concentration, resulting in FIG. Equation (2) is obtained by rearranging the values by the least square method.

In FIG. 9, zirconia concentrations of 0% and 100%
The plot at that time is the value shown on the JCPDS card. It can be judged that each plot in FIG. 9 follows Vegard's law, and that the equation (2) shows the relationship between the zirconia concentration and the lattice constant when the solid solubility is 100%. Based on the equations (1) and (2), the solid solubility S (%) of the ceria-zirconia solid solution is represented by the equation (3).

S = 100 × (x / C) × [(100-C) / (100-x)] (3) Here, x is obtained by the equation (2). The zirconia content C in the sample is obtained from the compounding ratio of cerium and zirconium. In the oxide solid solution particles of the present invention according to claim 1 and claim 4, the solid solubility of the oxide in the solid solution particles is 50% or more. If the solid solubility is less than 50%, desired characteristics cannot be obtained. For example, in the case of a solid solution of ceria and zirconia, if the solid solubility is less than 50%, the OSC of the solid solution particles is as low as 150 μmolO ₂ / g or less. However, if the solid solubility is 50% or more, the OSC is 250 to 800 μ.
Since it is more than molO ₂ / g, it has an extremely excellent oxygen storage capacity.

Two or more kinds of oxides B with respect to the oxide A,
When C, ... Are solid-dissolved, the solid solubility of any of two or more kinds of oxides B, C, ...
% Or more. Therefore, the solid solubility of each oxide is as follows: Solid solubility of oxide B (%) = 100 × (amount of oxide B dissolved in the total amount of oxide A) / total amount of oxide B Solid solubility (%) = 100 × (amount of oxide C dissolved in the total amount of oxide A) / total amount of oxide C. Which oxide (B, C ,. The solid solubility of ・ ・) must be 50% or more.

Further, in the oxide solid solution particles of the present invention, the average diameter of crystallites in the solid solution particles is 100 nm or less. The size of the crystallite is calculated from the half-width of the X-ray diffraction peak using the following Scherrer equation. D = kλ / (β cos θ) where k: constant 0.9, λ: X-ray wavelength (Å), β: diffraction line width of sample-diffraction line width of standard sample (radian), θ: diffraction angle (degree) When the average diameter of the crystallites is 100 nm or less, the crystallites are not densely packed and the solid solution particles have pores between the crystallites. When the average particle diameter exceeds 100 nm, the pore volume and the specific surface area decrease, and the heat resistance also decreases. This specific surface area is 1 m ² / g or more, further 20 m
It is desirable that it is ² / g or more, more preferably 50 m ² / g or more.

In the oxide solid solution particles of the present invention, for example, in the case of a solid solution of ceria and zirconia, zirconium partially substitutes zirconium at a position of cerium while maintaining the fluorite structure of ceric oxide to form a solid solution. Is a solid solution. A zirconia skeleton is formed in the solid solution. Therefore, the crystal structure of the cubic crystal becomes stable, and the cubic crystal is maintained even if the solid solution discharges a large amount of oxygen. Although the mechanism is not clear, the transfer of oxygen is considered to be easy in the case of the cubic system, and the OSC is higher than that of other tetragonal systems or monoclinic systems.

Further, since the average diameter of the crystallites is as small as 100 nm or less, the grain boundaries between the crystallites become large, and the oxygen ions moving through the grain boundaries easily move, so that the oxygen storage / release rates are sufficiently high. , The oxygen storage capacity is further improved. When the specific surface area is as large as 1 m ² / g or more, the oxygen is stored and released on the surface, so that the oxygen storage and release rates are sufficiently high, and the oxygen storage capacity is excellent in combination with the high OSC.

In the case of a solid solution of ceria and zirconia, the molar ratio of cerium and zirconium is 0.25≤Z.
The range of r / (Ce + Zr) ≦ 0.75 is preferable, and 0.
The range of 4 ≦ Zr / (Ce + Zr) ≦ 0.6 is particularly preferable. When the content of zirconium is 25 mol% or less,
The action of forming the skeleton of zirconium in the crystal of the solid solution is weakened, and it becomes difficult to maintain the cubic crystal of the fluorite structure due to the desorption of oxygen.
Is reduced. In addition, since the oxygen storage / release capability is due to a change in the valence of trivalent and tetravalent cerium, when the zirconium content is 75 mol% or more, the OSC is reduced due to a shortage of the absolute amount of cerium.

Further, since the oxide solid solution particles according to the fifth aspect are not in a thermodynamically stable phase, the solid solubility may decrease in use in an oxidizing atmosphere. In that case, at least one of an oxide of an alkaline earth element or an oxide of a rare earth element other than cerium is added to ceria and zirconia in the oxide solid solution particles to stabilize the solid solution phase in the oxide solid solution particles. can do.

The oxide of the alkaline earth element or the oxide of the rare earth element other than cerium to be added coexists with the oxide solid solution particles of ceria and zirconia, and a part of them is solid-dissolved in the solid solution phase of the oxide solid solution particles. All need not be solid-dissolved in the solid solution phase of the oxide solid solution particles. The composition range is such that at least one (M) of oxides of alkaline earth elements or oxides of rare earth elements other than cerium with respect to ceria and zirconia has a molar ratio of 0 <M / (Ce + Z.
The range of r + M) ≦ 0.15 is desirable. The average crystallite size of the oxide solid solution particles is preferably 10 nm or less, and the specific surface area is preferably 20 m ² / g or more. More preferably, it is 50 m ² / g.

The effect of adding at least one oxide of an alkaline earth element or an oxide of a rare earth element other than cerium to ceria and zirconia enhances the stability of a solid solution phase composed of ceria and zirconia in an oxidizing atmosphere at 900 ° C. or higher. With. Addition of an oxide of an alkaline earth element or an oxide of a rare earth element other than cerium has almost no effect in terms of increasing the OSC of the as-produced oxide solid solution particles. Rather, solid solution particles consisting of ceria and zirconia have a better OSC. However, when used for a long time in a high temperature oxidizing atmosphere, solid solution particles consisting of ceria and zirconia tend to gradually separate the solid solution phase into two phases and lower the OSC. When used under such conditions, the solid solution particles to which an oxide of an alkaline earth element or a rare earth element other than cerium is added, because the solid solution phase is relatively stable,
The OSC after use is relatively superior to the binary system of ceria and zirconia.

Therefore, at least one (M) of oxides of alkaline earth elements or oxides of rare earth elements other than cerium with respect to ceria and zirconia has a molar ratio of 0 <M /
When it becomes larger than the range of (Ce + Zr + M) ≦ 0.15,
On the contrary, OSC becomes smaller. In addition, the amount of ingredients increases, resulting in cost reduction. Further, if the average diameter of the crystallite is larger than 10 nm or the specific surface area is less than 20 m ² / g, the rate of oxygen absorption and desorption decreases, so that when used in an atmosphere where the oxygen partial pressure changes rapidly, OSC becomes small.

When an oxide of an alkaline earth element or an oxide of a rare earth element other than cerium is solid-dissolved in an oxide solid solution containing ceria and zirconia, the lattice constant of the crystal changes, so that the lattice constant of zirconia to ceria changes. It is difficult to determine the solid solubility of. However, it is possible to judge from the form of the X-ray diffraction peak whether or not the generated single solid solution phase is separated into the phase containing cerium and the phase containing zirconium.

6. A method according to claim 6, wherein the oxide solid solution particles are produced.
In the described production method of the present invention, a precipitate is obtained by adding a surfactant and an alkaline substance to an aqueous solution in which a plurality of types of oxide elements are dissolved. Here, the action of the surfactant is not clear, but it is presumed as follows. That is, in the state just neutralized with the alkaline substance, the element to be an oxide precipitates in the state of a very fine hydroxide or oxide having a particle diameter of several nm or less. Conventionally, it is dried as it is, but in the present invention, a plurality of kinds of precipitated particles are uniformly incorporated into the micelle of the surfactant by adding the surfactant. Then, as neutralization, aggregation and aging progress in the micelles, generation of solid solution particles proceeds in a small space in which a plurality of components are uniformly contained and concentrated. Furthermore, the dispersing effect of the surfactant improves the dispersibility of the precipitated fine particles, reduces segregation, and increases the degree of contact. As a result, the solid solubility is increased, and the average diameter of crystallites can be reduced.

The surfactant may be added before the alkaline substance, at the same time as the alkaline substance, or after the alkaline substance. However, if the surfactant is added too late, segregation will occur. Therefore, it is desirable to add the surfactant at the same time as or before the addition of the alkali substance. Examples of the compound of the element that becomes an oxide in the aqueous solution include cerium (III) nitrate, cerium (IV) ammonium nitrate, cerium (III) chloride, cerium (III) sulfate, cerium (IV) sulfate, zirconium oxynitrate, Examples include zirconium oxychloride and the like. Further, as the alkaline substance, any substance that exhibits alkalinity as an aqueous solution can be used. Ammonia, which can be easily separated on heating, is particularly desirable. However, other alkaline substances such as alkali metal hydroxides can be used because they can be easily removed by washing with water.

As the surfactant, any of anionic, cationic and nonionic surfactants can be used.
Among them, a surfactant that can easily form a narrow space inside the formed micelle, for example, a spherical micelle is preferable. The critical micelle concentration (cmc) is 0.1 mol
/ Liter or less is desirable. More preferably,
A surfactant of 0.01 mol / liter or less is desirable.

Examples of these surfactants include alkylbenzene sulfonic acid and its salt, α-olefin sulfonic acid and its salt, alkyl sulfate ester salt, alkyl ether sulfate ester salt, phenyl ether sulfate ester salt, and methyl taurate phosphate. , Sulfosuccinate, ether sulfate, alkyl sulfate, ether sulfonate,
Saturated fatty acids and their salts, unsaturated fatty acids such as oleic acid and its salts, other anionic surfactants such as carboxylic acid, sulfonic acid, sulfuric acid, phosphoric acid and phenol derivatives, polyoxyethylene polyprolene alkyl Ether, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polystyryl phenyl ether, polyoxyethylene polyoxy polypropylene alkyl ether, polyoxyethylene polyoxypropylene glycol, polyhydric alcohol; glycol; glycerin; sorbitol; Mannitol; pentaethritol; sucrose; fatty acid partial esters of polyhydric alcohols, such as polyhydric alcohol; glycol; glycerin; sorbitol; mannitol; Polyoxyethylene fatty acid partial ester of polyhydric alcohol, polyoxyethylene fatty acid ester, polyoxyethylated castor oil, polyglycene fatty acid ester, fatty acid diethanolamide, polyoxyethylene alkylamine, triethanolamine fatty acid partial ester, trialkylamine Nonionic surfactants such as oxides, primary fatty amine salts, secondary fatty amine salts, tertiary fatty amine salts, tetraalkylammonium salts; trialkylbenzylammonium salts; alkylpyrodinium salts; 2-alkyl-1 -Alkyl-1
-Hydroxyethyl imidazolinium salts; N, N-dialkylmorpholinium salts; quaternary ammonium salts such as polyethylene polyamine fatty acid amide salts; cationic surfactants such as betaine compounds; zwitterionic surfactants such as betaine compounds It is at least one selected from agents.

The critical micelle concentration (cmc) is the lowest concentration at which a surfactant forms micelles. The amount of the surfactant added is preferably in the range of 1 to 50 parts by weight with respect to 100 parts by weight of the oxide solid solution particles to be produced. When the content is 1 part by weight or more, the solid solubility is further improved. If it exceeds 50 parts by weight, the surfactant may not be able to effectively form micelles.

When producing a solid solution of ceria and zirconia, it is necessary to pay attention to the valence of cerium. In the case of tetravalent cerium, ceria relatively easily forms a solid solution with zirconia, and thus the oxide solid solution particles of the present invention can be manufactured by the above manufacturing method. However, in the case of trivalent cerium, ceria does not easily form a solid solution with zirconia, so it is desirable to adopt another means.

Therefore, in the invention described in claim 7, since cerium (III) forms a complex with hydrogen peroxide to be oxidized to cerium (IV), ceria can be easily made to form a solid solution with zirconia. . The amount of hydrogen peroxide added is
It is desirable that it is 1/4 or more of cerium ions. If the amount of hydrogen peroxide added is less than ¼ of the cerium ion, the solid solution of ceria and zirconia will be insufficient. Excessive addition of hydrogen peroxide has no particular adverse effect, but is only disadvantageous in terms of economy and has no merit, and is more preferably in the range of 1/2 to 2 times the cerium ion.

The time of addition of hydrogen peroxide is not particularly limited, and it may be added before the addition of the alkaline substance and the surfactant, or at the same time as or after the addition thereof. Further, hydrogen peroxide is a particularly desirable oxidant because it does not require post-treatment, but in some cases, other oxidants such as oxygen gas, ozone, peroxides such as perchloric acid and permanganate can be used. .

Further, in the production method of the present invention as set forth in claim 10, an aqueous solution in which a plurality of kinds of oxide elements are dissolved is high at a high shear rate of 10 ³ sec ^-1 or more, preferably 10 ⁴ sec ^-1 or more. A precipitate is obtained by adding an alkaline substance with stirring. The components in the precipitated fine particles, which are neutralization products, are inevitably segregated to some extent.
In the present invention, since the segregation is made uniform and the dispersibility is improved by vigorous stirring, the degree of contact between the cerium source and the zirconium source is further improved.

When coprecipitating from an aqueous solution of cerium salt and zirconium salt, for example, precipitated particles of the same kind tend to be aggregated because the pH of precipitation of both is different. Then, high-speed stirring at a high shear rate destroys a group of precipitated fine particles of the same type, and the precipitated particles are well mixed. Therefore, according to the invention described in claim 10, the solid solubility is improved and the average particle size of the crystallite can be further reduced. If the shear rate is less than 10 ³ sec ^-1 , the solid solution promoting effect is not sufficient. The shear rate V is V = v / D
It is represented by Here, v is the speed difference (m / sec) between the rotor and the stator of the stirrer, and D is the gap (m) between the rotor and the stator.

By applying the manufacturing method according to the tenth aspect to the manufacturing method according to the sixth aspect to the ninth aspect, the solid solution is further promoted. Further, since solid solution is promoted even when trivalent cerium is used, according to the present invention,
It is possible to produce solid solution particles having a high solid solubility without being oxidized to be tetravalent with hydrogen peroxide as in the invention of. Claims 6 to 10
In the second step of the manufacturing method of 1., the element in the precipitate is converted to an oxide by heating the precipitate. The heating atmosphere may be any of an oxidizing atmosphere, a reducing atmosphere and a neutral atmosphere. The reason why the element in the precipitate becomes an oxide is that oxygen contained in water or the like of the aqueous solution used as a raw material participates and oxidizes the element in the precipitate during heating.
Therefore, the oxide can be obtained even when heated in a reducing atmosphere.

According to the eleventh aspect of the present invention, even if the surfactant is not added to the aqueous solution of the raw material, the precipitate is heated in the reducing atmosphere in the second step to solidify the oxide in the particles. Oxide solid solution particles having a high solubility and a small average crystallite size in the particles can be obtained. This is considered to be due to the following reasons.

For example, in the case of solid solution particles of ceria and zirconia, since the heating atmosphere is in a reducing state, the cerium atom becomes trivalent in the oxide to generate oxygen defects, and the phase diffusion of cerium and zirconium is easy. Then, the solid solution of ceria and zirconia is easily promoted. Furthermore, zirconium is regularly arranged, and the skeleton of zirconia can be surely formed in ceria. Also, in the heat treatment in the atmosphere, it is 1600 to obtain a sufficient solid solution state.
A temperature of not less than 0 ° C is required, but in the manufacturing method of the tenth aspect, a solid solution proceeds sufficiently at a heat treatment temperature of not more than 1300 ° C.
Therefore, the size of the formed crystallite becomes small.

As the reducing atmosphere, carbon monoxide, hydrogen,
It is preferable that gas such as hydrocarbon is contained. Further, as described above, even in the reducing atmosphere, the oxygen contained in the water or the like in the aqueous solution used as the raw material oxidizes the element in the precipitate during heating, so that an oxide is obtained.

As the reducing atmosphere, for example, when the reducing atmosphere is CO, the CO concentration is preferably 0.1 to 30%. Within this range, the solid solubility is further improved. Examples of the method for recovering the precipitate include a method of squeezing out most of the water content from the precipitate with a filter press or the like, and a method of drying the filter cake, a method of spraying the precipitate and water with a spray dryer or the like, and drying. The precipitate can be dried quickly at 100 ° C or higher,
Drying at a temperature of not less than 0 ° C., more preferably not less than 300 ° C., is preferable because ammonium nitrate and the like generated by neutralization are decomposed and easily removed.

In the manufacturing method of claims 6 to 11, any method may be used as a method for heating the precipitate.
Further, the heating temperature is preferably in the range of 150 to 600 ° C. If the heating temperature is lower than 150 ° C., it is difficult to obtain an oxide, and if the heating temperature is higher than 600 ° C., the obtained oxide may sinter and particles may aggregate. Further, when the drying temperature reaches the above heating temperature (150 to 600 ° C.) during the drying at the time of recovering the precipitate, the drying step and the heating step of the precipitate may be combined.

Further, in the manufacturing method of claims 6 to 11, it is desirable that the obtained oxide solid solution particles are subjected to the following post-treatment. That is, it is also preferable to perform heat treatment on the oxide solid solution particles at 800 to 1300 ° C. in a reducing atmosphere (for example, a state in which a gas such as carbon monoxide, hydrogen, or hydrocarbon is contained), because the solid solution is promoted. For example, by reliably forming the zirconia skeleton in ceria, the OS
It is preferable because C can be increased. in this way,
During the heat treatment in a reducing atmosphere, some of the oxygen in the obtained solid solution is lost, and some of the cations (cerium) are reduced to a low valence (trivalent). However, if it is heated to about 300 ° C. or more in the air thereafter, it easily returns to the original state. Therefore, in the cooling process after the heat treatment, a process of bringing the material into contact with air at a temperature of about 600 ° C. or lower to restore the original valence may be performed.

When the precipitate is heated by spray drying, the oxide solid solution particles are obtained as powder (dry matter). Further, in the case of using other heating methods, the obtained oxide solid solution particles are lumpy,
By dry pulverizing with a hammer mill, a ball mill, a vibration mill or the like, a powder composed of oxide solid solution particles can be obtained.

[0052]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. Note that the present invention is not limited to the following embodiments. (Example 1) An aqueous solution was prepared by mixing cerium (III) nitrate and zirconyl nitrate in a molar ratio of Ce / Zr = 5/5. Aqueous ammonia was added dropwise with stirring to neutralize the precipitate. Was generated. Subsequently, an aqueous solution containing hydrogen peroxide containing hydrogen peroxide of half the number of moles of cerium ions contained in the mixed aqueous solution and an aqueous solution containing alkylbenzenesulfonic acid at 10% by weight of the obtained oxide were added and mixed. Stirred.

The slurry thus obtained was introduced at an air temperature of 400.
C., an exhaust air temperature of 250.degree. C. was sprayed and dried by a spray drying method, and coexisting ammonium nitrate was evaporated or decomposed to prepare a powder containing oxide solid solution particles. The solid solubility of the oxide solid solution particles was calculated by the formula (3) from the lattice constant by X-ray diffraction and the mixing ratio of the starting materials, and the solid solubility was 100%. Further, the average diameter of the crystallite was calculated from the 311 peak of the X-ray diffraction pattern using the Schuler's formula, and the average diameter was 10 nm. Further, the specific surface area of the oxide solid solution particles measured by the BET method was 45 m ² / g.

Comparative Example 1 Ceria powder and zirconia powder were mixed in a molar ratio of Ce / Zr = 5/5, dispersed in water, and mixed for 48 hours using a ball mill. The obtained slurry was dried at 120 ° C. to obtain a mixed powder. Next, this mixed powder is put into an alumina crucible and
It heated at 00 degreeC for 5 hours, and was set as the solid solution. After cooling, the mixture was ground in a mortar and further ground with water for 48 hours in a ball mill to prepare oxide solid solution particles of Comparative Example 1. Example 1
The solid solubility of the oxide solid solution particles measured in the same manner as in 100% was 100%, the average diameter of crystallites was 1000 nm, and the specific surface area was 0.3 m ² / g.

Comparative Example 2 Oxide particles were prepared in the same manner as in Example 1 except that hydrogen peroxide and a surfactant were not used. The solid solubility of these oxide particles is 18%, and the average diameter of crystallites is 6n.
m, the specific surface area was 80 m ² / g. (Comparative Example 3) Oxide particles were prepared in the same manner as in Example except that the surfactant was not used. The solid solubility of these oxide particles is 38.
%, Crystallite average diameter 7 nm, specific surface area 70 m ² / g
Met.

<Heat Resistance Evaluation> The oxide solid solution particles of Example 1 were heat treated. The results of measuring the specific surface area after heat treatment and the average diameter of the crystallites are shown in FIGS. 1 and 2. Heat treatment temperature is 3
Four levels are selected in the range of 50 to 1200 ° C., and the heat treatment time is 5 hours each. 1 and 2, although the oxide solid solution of Example 1 has a reduced specific surface area by heat treatment, it has a high specific surface area of 1 m ² / g or more even after heat treatment at 1200 ° C. and the crystallite diameter is maintained at 100 nm or less. You can see that it is done.

<OSC measurement> Further, Example 1 and Comparative Examples 1 to 1
The OSCs of the oxide solid solution particles of No. 3 were measured. The measurement of OSC was obtained by repeating the oxidation-reduction of the sample by flowing hydrogen and oxygen alternately using a thermogravimetric analyzer and measuring the weight change at that time. as a result,
The OSC of the oxide solid solution of Example 1 was 450 μmolO _2.
However, the OSCs of the oxide solid solutions of Comparative Examples 1 to 3 were 100, 95 and 150 μmolO ₂ / g, respectively.
The value was quite low as g. It is clear that this result is due to the difference in specific surface area for Comparative Example 1 and the difference in solid solubility for Comparative Examples 2 and 3.

Example 2 Example 2 was carried out in the same manner as in Example 1 except that hydrogen peroxide solution was added in advance to the aqueous solution of cerium (III) nitrate and zirconyl nitrate before dropwise addition of aqueous ammonia. The oxide solid solution particles of Example 2 were prepared.
The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average diameter of crystallites was 10 nm, and the specific surface area was 45 m ² / g.

Example 3 Example 3 was carried out in the same manner as in Example 1 except that the aqueous solution of alkylbenzene sulfonic acid was added in advance to the aqueous solution of cerium (III) nitrate and zirconyl nitrate before dropwise addition of aqueous ammonia. The oxide solid solution particles of Example 3 were prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average crystallite diameter was 12 nm, and the specific surface area was 35 m ² / g.

Example 4 Oxide solid solution particles of Example 4 were prepared in the same manner as in Example 1 except that an α-olefin sulfonic acid aqueous solution was used instead of the alkylbenzene sulfonic acid aqueous solution. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95%, the average diameter of crystallites was 8 nm, and the specific surface area was 35 m ² / g.

Example 5 Oxide solid solution particles of Example 5 were prepared in the same manner as in Example 1 except that a polyoxyethylene polypropyl alkyl ether aqueous solution was used instead of the alkylbenzene sulfonic acid aqueous solution. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average crystallite diameter was 8 nm, and the specific surface area was 40 m ² / g.

Example 6 In the same manner as in Example 1 except that an aqueous solution of cetyltrimethylammonium chloride was used instead of the aqueous solution of alkylbenzene sulfonic acid,
The oxide solid solution particles of Example 6 were prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 is 9
5%, average diameter of crystallite is 7 nm, specific surface area is 58 m ² /
g.

Example 7 Oxide solid solution particles of Example 7 were prepared in the same manner as in Example 1 except that a monoalkylammonium acetate aqueous solution was used instead of the alkylbenzene sulfonic acid aqueous solution. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 is 90.
%, The average crystallite diameter is 8 nm, and the specific surface area is 60 m ² / g.
Met.

Example 8 Oxide solid solution particles of Example 8 were prepared in the same manner as in Example 1 except that a polyoxyethylene alkylphenyl ether aqueous solution was used instead of the alkylbenzene sulfonic acid aqueous solution. Example 1
The solid solubility of the oxide solid solution particles measured in the same manner as in 95%, the average diameter of crystallites is 8 nm, and the specific surface area is 50 m.
² / g.

Example 9 Oxide solid solution particles of Example 9 were prepared in the same manner as in Example 1 except that a polyoxyethylene alkyl ether aqueous solution was used instead of the alkylbenzene sulfonic acid aqueous solution. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95.
%, The average crystallite diameter is 8 nm, and the specific surface area is 54 m ² / g.
Met.

Example 10 Oxide solid solution particles of Example 10 were prepared in the same manner as in Example 1 except that a polyoxyethylene alkylamine aqueous solution was used instead of the alkylbenzene sulfonic acid aqueous solution. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 is 90.
%, Crystallite average diameter 6 nm, specific surface area 48 m ² / g
Met.

Example 11 Oxide solid solution particles of Example 11 were prepared in the same manner as in Example 1 except that an aqueous solution of polyoxyethylene fatty acid amide was used instead of the aqueous solution of alkylbenzene sulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 is 90.
%, The average crystallite diameter is 7 nm, and the specific surface area is 62 m ² / g.
Met.

Example 12 Example 1 was repeated in the same manner as Example 1 except that an aqueous solution of trialkylamine oxide was used instead of the aqueous solution of alkylbenzene sulfonic acid.
No. 2 oxide solid solution particles were prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95%,
The crystallites had an average diameter of 9 nm and a specific surface area of 67 m ² / g.

Example 13 Oxide solid solution particles of Example 13 were prepared in the same manner as in Example 1 except that an aqueous solution of polyoxyethylene alkylmethyl ammonium chloride was used instead of the aqueous solution of alkylbenzene sulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, and the average diameter of crystallites was 9 n.
m, the specific surface area was 37 m ² / g.

Example 14 The oxide solid solution particles of Example 14 were prepared in the same manner as in Example 1 except that the tallow diamine dioleic acid aqueous solution was used instead of the alkylbenzene sulfonic acid aqueous solution. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average diameter of the crystallite was 8 nm, and the specific surface area was 35 m ² / g.

<Evaluation> From the results of Examples 2 to 14, it can be seen that all the surfactants used in these have the same effect as that of the alkylbenzene sulfonic acid. (Example 15) Example 15 except that the addition amount of alkylbenzene sulfonic acid was variously selected within the range of 0 to 30% by weight of the obtained oxide and the Ce / Zr ratio in the starting material was changed. In the same manner as in 1, each oxide solid solution particle was prepared. The lattice constant of the crystal of each oxide solid solution particle was measured by the X-ray diffraction method, and the lattice constant of the oxide solid solution particle of Example 1 is shown in FIG. Further, FIG. 5 shows the relationship between the lattice constant and the solid solubility calculated from the composition (Ce / Zr = 5/5 in terms of molar ratio) using the formula (3).
Further, the relationship between the zirconia content and the lattice constant in the solid solution of ceria and zirconia in each composition is shown in FIG. 4 for each solid solubility. The range corresponding to claim 3 is represented by diagonal lines.

Further, the specific surface area of the oxide solid solution particles was measured for each activator addition rate of Ce / Zr = 5/5, and the results are also shown in FIG. <Evaluation> From FIG. 3, the lattice constant decreases as the addition rate of alkylbenzene sulfonic acid increases, and the addition rate is about 10%.
In the above, the lattice constant is 5.275, which is almost constant. Further, FIG. 4 shows that when Ce / Zr = 5/5, the solid solubility is 100% and the lattice constant is 5.275. Therefore, the addition amount of alkylbenzenesulfonic acid is 10% or more. If so, it can be seen that the solid solution is complete.
This is supported by the result of FIG. 5 in which the solid solubility was actually measured. That is, it is clear that the solid solution is promoted by the addition of the surfactant, and it is understood that the addition rate of the alkylbenzene sulfonic acid is about 1% or more.

(Example 16) After squeezing water from a slurry containing a precipitate by using a filter press, 30
The oxide solid solution particles of Example 16 were prepared in the same manner as in Example 1 except that the solid content was dried by heating at 0 ° C. and mechanically pulverized. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95%, the average diameter of crystallites was 8 nm, and the specific surface area was 60 m ² / g.

(Example 17) Two slurry containing precipitates were added.
Oxide solid solution particles of Example 17 were prepared in the same manner as in Example 1 except that they were dried by being brought into contact with a ceramic ball heated to 50 ° C. at the same time. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average crystallite diameter was 8 nm, and the specific surface area was 40 m ² / g.

(Example 18) Three slurries containing precipitates were used.
The oxide solid solution particles of Example 18 were placed in the same manner as in Example 1 except that the mixture was heated in a heating container heated to 00 ° C. and heated until water and ammonium nitrate were evaporated or decomposed and desorbed, and then mechanically ground. Prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 is 100.
%, Crystallite average diameter 9 nm, specific surface area 35 m ² / g
Met.

<Evaluation> From the results of Example 1 and Examples 16 to 18, it is clear that particles having predetermined characteristics can be obtained by the drying and pulverizing means used. (Example 19) An aqueous solution was prepared by mixing cerium (III) nitrate and zirconyl nitrate in a molar ratio of Ce / Zr = 5/5, and further 5% of the weight of the obtained oxide was prepared.
The polyoxyethylene polypropyl alkyl ether of 1) and hydrogen peroxide solution containing Ce ions and equimolar hydrogen peroxide are added, and mixed and stirred. Subsequently, ammonia water was added dropwise with stirring to neutralize, and a precipitate was generated.

The slurry containing the precipitate was allowed to stand and the supernatant was removed. Again, the same amount of water as the removed water was added, and after stirring, the supernatant was removed. After performing this operation once again, the remaining slurry was placed in a container heated to 250 ° C. and heated until water and ammonium nitrate were evaporated or decomposed and desorbed to obtain a powder containing an oxide solid solution. The solid solubility of the oxide solid solution particles was 95%, the average diameter of the crystallites was 6 nm, and the specific surface area was 80 m ² / g.

The oxide solid solution particles of Example 19 were heat-treated, and the results of measuring the specific surface area and the average crystallite size after the heat treatment are shown in FIGS. 6 and 7. Heat treatment temperature is 300, 60
Five levels of 0, 800, 1000, and 1200 ° C., and heat treatment time is 5 hours. (Example 20) The oxide solid solution particles obtained in Example 1 were mixed with each other in a reducing atmosphere containing 1% by volume of carbon monoxide.
Heat treatment was performed at 00 ° C. for 2 hours to prepare oxide solid solution particles of Example 20. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average crystallite diameter was 55 nm, and the specific surface area was 4 m ² / g. The OSC of this powder was 800 μmol O ₂ / g.

(Example 21) The oxide solid solution particles obtained in Example 1 were heat-treated at 1100 ° C for 5 hours in a reducing atmosphere containing 1% by volume of hydrogen gas to obtain the oxide solid solution particles of Example 21. Was prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average diameter of crystallites was 48 nm, and the specific surface area was 8 m ² / g.
The OSC was 750 μmolO ₂ / g.

<Evaluation> That is, it can be seen that by heat-treating the oxide solid solution particles of Example 1 in a reducing atmosphere, the average particle diameter increases to some extent, but the OSC increases. (Example 22) The amounts of cerium (III) nitrate and zirconyl nitrate were determined so that the molar ratio of cerium and zirconium was Ce / Zr.
Each oxide solid solution particle was prepared in the same manner as in Example 1 except that various aqueous solutions were mixed in the range of 9/1 to 1/9. The OSC of each oxide solid solution particle was measured in the same manner as in Example 1, and the results are shown in FIG. The lattice constant of the crystal was measured for each oxide solid solution particle, and the results are shown in FIG.

<Evaluation> From FIG. 8, the Ce / Zr ratio is 75.
/ 25 to 25/75, OSC is 250 μm
It is clear that it becomes olO ₂ / g or more. FIG. 4
Therefore, the zirconia contained in these powders is almost 10
It can be seen that it is dissolved in 0% ceria.

Example 23 Medium without hydrogen peroxide solution
Stir 10 when mixing and adding a surfactant.^Foursec ^-1Less than
Same as Example 1 except that the above high shear rate was used.
Thus, oxide solid solution particles of Example 23 were prepared. Implementation
The solid content of the oxide solid solution particles measured in the same manner as in Example 1
Solubility 90%, average crystallite diameter 7 nm, specific surface area 6
0m^Two/ G.

Comparative Example 4 Oxide solid solution particles of Comparative Example 4 were prepared in the same manner as in Example 1 except that hydrogen peroxide solution was not used. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 40%, the average diameter of crystallites was 6 nm, and the specific surface area was 85 m ² / g.

<Evaluation> Comparative Example 4 has a lower solid solubility than Example 23 and is inferior in the progress of solid solution, but Example 23 shows a high solid solubility almost similarly to Example 1. That is, 10
By stirring at a high shear rate of ⁴ sec ^-1 or more,
It is clear that the solid solution is promoted as in the case of using hydrogen peroxide.

Example 24 Cerium (IV) nitrate and zirconyl nitrate were mixed in a molar ratio of Ce / Zr = 5/5 to prepare an aqueous solution, and ammonia water was added dropwise with stirring to neutralize the solution. And a precipitate was formed. Subsequently, an aqueous solution containing 10% of the weight of the obtained oxide by alkylbenzene sulfonic acid was added and mixed and stirred.

The slurry thus obtained was introduced at an air temperature of 400.
C., the temperature of the exhaust air was 250.degree. C., sprayed in an atmosphere and dried by a spray drying method, and coexisting ammonium nitrate was decomposed to prepare oxide solid solution particles. Example 1
The solid solubility of the oxide solid solution particles measured in the same manner as in 100%, the average diameter of crystallites is 10 nm, and the specific surface area is 5
It was 0 m ² / g.

<Evaluation> From the comparison between Comparative Example 2 and Example 24, in the case of tetravalent cerium, unlike trivalent cerium, it is possible to form a solid solution with a high solid solubility without using hydrogen peroxide. Recognize. (Example 25) The procedure of Example 25 was repeated except that the aqueous solution of alkylbenzene sulfonic acid was added in advance to the aqueous solution of cerium (IV) nitrate and zirconyl nitrate before the dropwise addition of aqueous ammonia. Oxide solid solution particles were prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, and the average diameter of the crystallite was 1.
The surface area was 0 nm and the specific surface area was 40 m ² / g.

<Evaluation> That is, in Example 25, Example 2 was used.
Since a solid solution equivalent to 4 is produced, the surfactant has the same action before and after neutralization with alkali, that is, the action of the surfactant is only when neutralizing with alkali. It can be seen that it is also effective for the oxide state after being neutralized with alkali.

(Example 26) Oxide solid solution particles of Example 26 were prepared in the same manner as in Example 24 except that an aqueous solution of α-olefin sulfonic acid was used instead of the aqueous solution of alkylbenzene sulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95%, the average diameter of crystallites was 8 nm, and the specific surface area was 60 m ² / g.

Example 27 Alkylbenzenesulfone
Instead of acid aqueous solution, polyoxyethylene polypropyl acetate
Example 24 except that an aqueous solution of rutile ether was used.
Similarly, the oxide solid solution particles of Example 25 were prepared.
Was. This oxide solid solution measured in the same manner as in Example 1.
The solid solubility of the particles is 100%, the average diameter of the crystallites is 8 nm, and the ratio is
Surface area is 45m ^Two/ G.

(Example 28) Oxide solid solution particles of Example 28 were prepared in the same manner as in Example 24, except that an aqueous solution of cetyltrimethylammonium chloride was used instead of the aqueous solution of alkylbenzene sulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95%, the average diameter of crystallites was 7 nm, and the specific surface area was 62.
m ² / g.

Example 29 The same procedure as in Example 24 was carried out except that an aqueous solution of monoalkylammonium acetate was used instead of the aqueous solution of alkylbenzene sulfonic acid.
The oxide solid solution particles of Example 29 were prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 90%, the average crystallite diameter was 8 nm, and the specific surface area was 60 m ^2.
/ G.

Example 30 Oxide solid solution particles of Example 30 were prepared in the same manner as in Example 24, except that an aqueous solution of polyoxyethylene alkylphenyl ether was used instead of the aqueous solution of alkylbenzene sulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95%, the average diameter of the crystallites was 8 nm, and the specific surface area was 55 m ² / g.

(Example 31) In the same manner as in Example 24 except that a polyoxyethylene alkyl ether aqueous solution was used instead of the alkylbenzene sulfonic acid aqueous solution,
The oxide solid solution particles of Example 31 were prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95%, the average crystallite diameter was 8 nm, and the specific surface area was 57 m ^2.
/ G.

(Example 32) Oxide solid solution particles of Example 32 were prepared in the same manner as in Example 24, except that an aqueous solution of polyoxyethylene alkylamine was used instead of the aqueous solution of alkylbenzene sulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 is 9
0%, crystallite average diameter 6 nm, specific surface area 45 m ² /
g.

Example 33 Oxide solid solution particles of Example 33 were prepared in the same manner as in Example 24, except that an aqueous solution of polyoxyethylene fatty acid amide was used instead of the aqueous solution of alkylbenzene sulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 is 90.
%, The average crystallite diameter is 7 nm, and the specific surface area is 59 m ² / g
Met.

Example 34 Oxide solid solution particles of Example 34 were prepared in the same manner as in Example 24, except that an aqueous solution of trialkylamine oxide was used instead of the aqueous solution of alkylbenzene sulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95.
%, Crystallite average diameter 9 nm, specific surface area 62 m ² / g
Met.

Example 35 Oxide solid solution particles of Example 35 were prepared in the same manner as in Example 24 except that an aqueous solution of polyoxyethylene alkylmethyl ammonium chloride was used instead of the aqueous solution of alkylbenzene sulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, and the average diameter of crystallites was 9 n.
m, the specific surface area was 30 m ² / g.

Example 36 Example 36 was carried out in the same manner as in Example 24 except that a tallow diamine dioleic acid aqueous solution was used instead of the alkylbenzene sulfonic acid aqueous solution.
The oxide solid solution particles of were prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 is 100%,
The crystallites had an average diameter of 8 nm and a specific surface area of 40 m ² / g.

<Evaluation> From the results of Example 24 and Examples 26 to 36, it is understood that all the surfactants used have the same effect as that of alkylbenzene sulfonic acid even when hydrogen peroxide is not used. . (Example 37) Similar to Example 24 except that after squeezing water from the slurry containing the precipitate using a filter press, the solid content was dried by heating to 300 ° C and mechanically pulverized. The oxide solid solution particles of Example 37 were prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 95%, the average diameter of crystallites was 8 nm,
The specific surface area was 70 m ² / g.

(Example 38) Two slurry containing precipitates were used.
The oxide solid solution particles of Example 38 were prepared in the same manner as in Example 24, except that the particles were mechanically crushed by the balls while being brought into contact with the ceramic balls heated to 50 ° C. to be dried. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average crystallite diameter was 8 nm, and the specific surface area was 40 m ² / g.

(Example 39) A slurry containing precipitates was added to 3
The oxide solid solution particles of Example 39 were placed in the same manner as in Example 24 except that the mixture was heated in a heating container heated to 00 ° C. and heated until moisture and ammonium nitrate were evaporated or decomposed and desorbed, and then mechanically pulverized. Prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 10.
0%, crystallite average diameter 9 nm, specific surface area 35 m ² /
g.

<Evaluation> Example 24 and Examples 37 to 39
From the results, it is clear that even if hydrogen peroxide is not used, there is no difference depending on the grinding means used. (Example 40) The oxide solid solution particles obtained in Example 24 were mixed with each other in a reducing atmosphere containing 1% by volume of carbon monoxide.
Heat treatment was performed at 00 ° C. for 2 hours to prepare oxide solid solution particles of Example 40. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average crystallite diameter was 52 nm, and the specific surface area was 5 m ² / g.

(Example 41) The oxide solid solution particles obtained in Example 24 were heat-treated at 1100 ° C for 5 hours in a reducing atmosphere containing 1% by volume of hydrogen gas to obtain the oxide solid solution particles of Example 41. Was prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 100%, the average crystallite diameter was 44 nm, and the specific surface area was 9 m ² / g.

<Evaluation> That is, by heat-treating the oxide solid solution particles of Example 24 in a reducing atmosphere, the average particle diameter is increased to some extent even when hydrogen peroxide is not used, but the OSC is increased. I understand. Example 42 Each oxide solid solution particle was prepared in the same manner as in Example 24 except that the addition amount of the aqueous solution containing alkylbenzene sulfonic acid was variously selected. The crystal lattice constants of these oxide solid solution particles show the same results as in FIG. 3, and it is clear that in the case of tetravalent cerium, zirconia can form a solid solution with a high solid solubility without using hydrogen peroxide. is there.

Example 43 An aqueous solution was used in which cerium (IV) nitrate and zirconyl nitrate were added in various amounts such that the molar ratio of cerium and zirconium was Ce / Zr = 9/1 to 1/9. Except for this, each oxide solid solution particle was prepared in the same manner as in Example 1. The OSC of each oxide solid solution particle was similar to that of FIG. 8, and the crystal lattice constant was similar to that of FIG.

That is, in the case of tetravalent cerium, Ce / Zr
It is clear that when the ratio is in the range of 75/25 to 25/75, the OSC becomes 250 μmolO ₂ / g or more without using hydrogen peroxide. Further, even if hydrogen peroxide is not used, the zirconia skeleton is formed in the ceria crystal by the solid solution of zirconia. (Example 44) An aqueous solution prepared by mixing cerium (III) nitrate and zirconyl nitrate in a molar ratio of Ce / Zr = 5/5 was prepared, and ammonia water was added dropwise with stirring to neutralize the precipitate. Was generated. This slurry was dried in the same manner as in Example 1, and further heat treated in the same manner as in Example 20. The solid solubility of the oxide solid solution particles was 80%, the average crystallite diameter was 48 nm, and the specific surface area was 3 m ² / g.

Example 45 An aqueous solution prepared by mixing cerium (III) nitrate and zirconyl nitrate in a molar ratio of Ce / Zr = 5/5 was prepared, and ammonia water was added dropwise with stirring to neutralize the solution. And a precipitate was formed. This slurry was dried in the same manner as in Example 1, and further heat treated in the same manner as in Example 21. The solid solubility of the oxide solid solution particles is 70.
%, The average crystallite diameter is 40 nm, and the specific surface area is 9 m ² / g.
Met.

(Example 46) In the same manner as in Example 1, cerium (III) nitrate and zirconyl nitrate were mixed at a molar ratio of Ce / Z.
A mixed aqueous solution was prepared so that r = 5/5, and then an aqueous solution of yttrium nitrate was added in a molar ratio of Y / (Y + C
e + Zr) = 0/100 to 10/10 were compounded at 5 levels. Further, hydrogen peroxide was added so that the number of moles was 1/2 of cerium ion, and 5% by weight of the oxide capable of obtaining polyoxyethylene polypropylalkyl ether was further added, and then ammonia water was added dropwise while stirring. And neutralized to form precipitates. The precipitate was placed in an oven heated to 300 ° C. to evaporate water and heated until the ammonium nitrate and the surfactant were decomposed and desorbed. The average particle size of the crystallites of the obtained oxide solid solution particles was 8 nm, and the specific surface area was 70 m ² / g.

120% of these oxide solid solution particles were placed in the atmosphere.
The results of examining the changes in the crystal phase by X-ray diffraction are shown in FIG. 10. From FIG. 10, it can be seen that the solid solution phase becomes more stable by the addition of yttrium. (Example 47) Oxide solid solution particles were prepared in the same manner as in Example 46 except that yttrium nitrate was replaced with calcium nitrate. The average particle size of the crystallites of the obtained oxide solid solution particles was 7 nm, and the specific surface area was 80 m ² / g.

120% of these oxide solid solution particles were placed in the atmosphere.
FIG. 11 shows the results of examining changes in crystal phase by X-ray diffraction after heating at 0 ° C. for 4 hours. From FIG. 11, it can be seen that the solid solution phase becomes more stable by the addition of calcium. (Example 48) Instead of yttrium nitrate, lanthanum nitrate, magnesium nitrate, strontium nitrate and barium nitrate were used in a molar ratio of M / (M + Ce + Zr) = 7 /.
Except for using 100, 10/100, 10/100, and 10/100, in the same manner as in Example 46,
Each oxide solid solution particle was prepared. The average diameter of the crystallites of the obtained oxide solid solution particles was 6 to 8 nm, and the specific surface area was 60 to 90 m ² / g.

Next, the oxide solid solution particles of Examples 46 to 48 and Example 1 were heated to 300 ° C. or 120 ° C. in the atmosphere.
Calcination was performed at 0 ° C. for 2 hours, and OSC was performed in the same manner as in Example 1.
Was measured. The respective results are shown in FIG. 12 together with the results of Example 1. From FIG. 12, it can be seen that the oxide solid solution particles of Examples 46 to 48 have a large OSC as in Example 1 and more excellent durability at high temperature as compared with Example 1.

Incidentally, in the case of Examples 46 and 47, it was found that the OSC decreased conversely as the amounts of yttrium and calcium increased, as shown in FIG. That is, a relatively large OSC is maintained until the amount of yttrium and calcium is up to 15 mol%, but the amount of yttrium and calcium is significantly reduced when the amount is larger than that. (Example 49) Each oxide solid solution particle was prepared in the same manner as in Example 47 except that the ratio of cerium nitrate to zirconyl nitrate was changed. And Example 1
The OSC was measured in the same manner as, and the result is shown in FIG. FIG.
The Ce / Zr ratio is 25/75 or less, or 75/25
It is understood that in the above range, the OSC of the oxide solid solution becomes small.

(Example 50) Oxide solid solution particles of Example 50 were prepared in the same manner as in Example 1 except that the amount of hydrogen peroxide added was 1.2 times that of cerium ions. The solid solubility of the oxide solid solution particles was 100%, the average crystallite diameter was 9 nm, and the specific surface area was 50 m ² / g.

Thus, even if the amount of hydrogen peroxide is increased from that in Example 1, oxide solid solution particles having the same solid solubility as in Example 1 can be prepared.

[0116]

According to the oxide solid solution particles of the present invention, the solid solution particles have a high solid solubility and the crystallites have a small average particle size. If the solid solution is a solid solution of ceria and zirconia, it has a crystal structure in which zirconium is substituted for part of the position of cerium while maintaining the fluorite structure of ceria. In addition, it has a high oxygen storage / release rate and a high oxygen storage capacity.

Further, according to the production method of the present invention, it is considered that by adding a surfactant, a plurality of elements are uniformly aggregated in a small space in the micelle to form particles. Therefore, a substantially complete solid solution can be obtained while maintaining the average crystallite size, and the oxide solid solution of the present invention can be easily and reliably produced. Then, by further adding hydrogen peroxide, a high solid solubility is secured even when trivalent cerium is used.

Further, according to the manufacturing method of the present invention as set forth in claim 10, by strongly stirring the aqueous solution, segregation of the coprecipitate is suppressed when a plurality of elements are coprecipitated, and the coprecipitate is uniformly dispersed. it is conceivable that. Therefore, a substantially complete solid solution can be obtained while maintaining the average crystallite size, and the oxide solid solution of the present invention can be easily and reliably produced. Further, even when trivalent cerium is used, high solid solubility can be secured without adding hydrogen peroxide.

Furthermore, according to the manufacturing method of the present invention as set forth in claim 11, the precipitate obtained from the aqueous solution is heated in a reducing atmosphere to form a substantially complete solid solution while maintaining the average crystallite size. Thus, the oxide solid solution of the present invention can be manufactured easily and reliably. Further, even when trivalent cerium is used, high solid solubility can be secured without adding hydrogen peroxide.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a heat treatment temperature and a specific surface area.

FIG. 2 is a graph showing the relationship between the heat treatment temperature and the average diameter of crystallites.

FIG. 3 is a graph showing the relationship between the addition rate of alkylbenzene sulfonic acid and the lattice constant of the crystals of the oxide solid solution particles formed.

FIG. 4 is a graph showing a relationship between a zirconia content rate and a lattice constant of crystals of oxide solid solution particles formed.

FIG. 5 is a graph showing the relationship between the surfactant addition rate and the solid solubility and specific surface area of the formed oxide solid solution particles.

FIG. 6 is a graph showing the relationship between heat treatment temperature and specific surface area.

FIG. 7 is a graph showing the relationship between heat treatment temperature and average crystallite size.

FIG. 8 is a graph showing the relationship between the Ce / Zr molar ratio and the OSC of the formed oxide solid solution particles.

FIG. 9 is a graph showing the relationship between the zirconia concentration in oxide solid solution particles and the lattice constant.

FIG. 10 is an X-ray diffraction chart showing the effect of the amount of yttrium added.

FIG. 11 is an X-ray diffraction chart showing the effect of the added amount of calcium.

FIG. 12 is a graph showing OSC when various alkaline earth elements or rare earth elements are added.

FIG. 13: Yttrium or calcium addition amount and OS
It is a graph which shows the relationship of C.

FIG. 14 is a graph showing the relationship between zirconium content and OSC.

Front Page Continuation (72) Inventor Masa Tadashi, Nagakute-cho, Aichi-gun, Aichi-gun, Nagakage, Yoko 41-chome, Toyota Central Research Institute Co., Ltd. (72) Inventor Toshio Kamtori 41, Nagakute-cho, Aichi, Aichi-gun, Nagakage Address 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Yoshio Ukyo 41, Nagakute-cho, Aichi-gun, Aichi-gun, Nagakute-machi Large Toyota Road Research Institute Ltd. (72) Inventor Masataka Sugiura Aichi-gun, Aichi Prefecture Nagakute-machi Oita Nagaminato Yokoyodo 41, 1 Toyota Central Research Laboratory (72) Inventor Norio Kimura Nagachite Aichi-gun Aichi-gun Nagakute Yokoyoji 41 Toyota Corporation

Claims (11)

[Claims] 1. A particle comprising an oxide solid solution in which another oxide is solid-dissolved in one oxide, wherein the solid solubility of the other oxide with respect to the one oxide in the particle is 50%. Above, and the average diameter of the crystallite in the particles is 100 nm or less, oxide solid solution particles. 2. The oxide solid solution particles according to claim 1, wherein the particles are aggregated to form a powder. 3. The oxide solid solution particles according to claim 1, wherein the specific surface area of the particles is 1 m ² / g or more. 4. Particles containing an oxide solid solution in which zirconium oxide is solid-dissolved in cerium oxide, wherein the zirconium oxide has a solid solubility of 50% or more with respect to the cerium oxide in the particles, and Oxide solid solution particles, wherein the crystallites in the particles have an average diameter of 100 nm or less. 5. The molar ratio of cerium to zirconium in the particles is 0.25 ≦ Zr / (Ce + Zr) ≦.
The oxide solid solution particles according to claim 4, which are in the range of 0.75. 6. A first step of obtaining a precipitate by adding a surfactant and an alkaline substance to an aqueous solution in which a plurality of kinds of oxide elements are dissolved, and heating the precipitate to form one oxide. A particle containing an oxide solid solution in which another oxide is formed as a solid solution, the solid solubility of the other oxide with respect to the one oxide in the particle is 50% or more, and the crystallite in the particle And a second step of obtaining oxide solid solution particles having an average diameter of 100 nm or less, and a method for producing oxide solid solution particles. 7. The method for producing oxide solid solution particles according to claim 6, wherein the elements forming the oxide are tetravalent cerium and zirconium. 8. A first step of obtaining a precipitate by adding hydrogen peroxide, a surfactant and an alkaline substance to an aqueous solution in which trivalent cerium and zirconium are dissolved, and heating the precipitate, A particle containing an oxide solid solution in which zirconium oxide is solid-dissolved in cerium oxide, wherein the zirconium oxide has a solid solubility of 50% or more with respect to the cerium oxide in the particle, and a crystal in the particle. A second step of obtaining oxide solid solution particles having an average particle size of 100 nm or less, and a method for producing oxide solid solution particles, comprising: 9. The surfactant has a critical micelle concentration of 0.
It is 1 mol / liter or less, The manufacturing method of the oxide solid solution particle of Claim 6, 7 or 8 characterized by the above-mentioned. 10. A first step of obtaining a precipitate by adding an alkaline substance while rapidly stirring an aqueous solution in which a plurality of kinds of oxide elements are dissolved at a high shear rate of 10 ³ sec ⁻¹ or more, and the precipitation. A particle containing an oxide solid solution in which another oxide is solid-dissolved in one oxide, and the solid solubility of the other oxide with respect to the one oxide in the particle is 50%. The method for producing oxide solid solution particles, which comprises the above second step of obtaining oxide solid solution particles in which the average diameter of crystallites in the particles is 100 nm or less. 11. A first step of obtaining a precipitate by adding an alkaline substance to an aqueous solution in which a plurality of kinds of oxide elements are dissolved, and heating the precipitate in a reducing atmosphere to obtain a single oxide. Particle containing an oxide solid solution in which the oxide of 1. is dissolved, and the solid solubility of the other oxide with respect to the one oxide in the particle is 50.
% And the average diameter of the crystallites in the particles is 100
A second step of obtaining oxide solid solution particles having a particle size of nm or less, and a method for producing oxide solid solution particles, the method comprising: