JP3341973B2 - Oxide solid solution particles and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oxide solid solution particle and a method for producing the same. As the oxide solid solution of the present invention, for example, a solid solution of cerium oxide (hereinafter, referred to as ceria) and zirconium oxide (hereinafter, referred to as zirconia) is exemplified, and in this case, the ability of ceria to store and discharge oxygen (oxygen storage ability). Is further improved, so that it is useful as a promoter of an exhaust gas purifying catalyst. Further, the oxide solid solution of the present invention can also be used as a diesel particulate oxidation catalyst, a solid electrolyte, an electrode material, ceramic dispersion strengthened particles, a material for shielding ultraviolet rays, and the like.

[0002]

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

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

For example, Japanese Patent Application Laid-Open No. 4-55315 discloses
There is disclosed a method for producing cerium oxide fine powder in which ceria and zirconia are coprecipitated from a mixed aqueous solution of a water-soluble salt of cerium and a water-soluble salt of zirconium, and heat-treated therewith. According to this manufacturing method, cerium and zirconium are converted into oxides by heat-treating the coprecipitate to form oxide solid solutions in which they are dissolved.

Japanese Patent Application Laid-Open No. 4-284847 discloses that
It is disclosed that an impregnation method or a coprecipitation method produces a powder in which zirconia or a rare earth element oxide and ceria are dissolved.

[0006]

However, according to the study 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 was not. In other words, for cerium and zirconium, the pH of the aqueous solution
In the method of coprecipitation from a mixed aqueous solution, the composition of the coprecipitate becomes non-uniform, and almost no solid solution occurs at the stage of coprecipitation. In addition, 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.In each case, the primary particles of the oxide powder are large, The composition as a whole becomes non-uniform, and solid solution is not easily promoted.

Therefore, in both methods, a solid solution is caused by heat treatment, and the co-precipitation method is performed at a temperature of 500 to 900 ° C. and the impregnation method is performed at a temperature of 700 to 1200 ° C., but the solid solution is not sufficient. In both methods, a heat treatment of the powder forms a neck between the particles, and the neck promotes solid solution.Accordingly, grain growth and sintering are promoted, so that the specific surface area of the powder decreases, The particle size of the particles also increases. In addition, once solid solution particles have grown, it is difficult to pulverize them easily.

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) due to ceria is 100 to 150 μmol O at most.
Unless the temperature is as low as about ₂ / g and the temperature is not higher than 500 ° C., there is a problem that oxygen storage / release capability is not sufficiently exhibited and oxygen storage capability is low.

If the heat treatment is sufficiently performed at about 1600 ° C., the solid solubility of the solid solution of ceria and zirconia becomes almost 100%.
% Is known. However, in this case, the OS
Although C is high, the average particle size of the crystallites becomes 1000 nm or more and the specific surface area becomes small, so that the
The release rate is limited by a small specific surface area, and is not practical as a cocatalyst.

[0010] The present invention has been made in view of such circumstances, and by increasing the solid solubility, the performance as a solid solution such as oxygen storage capacity is improved, and the average diameter of crystallites is small and the specific surface area is large. It is an object of the present invention to provide an oxide solid solution particle having: and a production method capable of easily and surely producing the solid solution particle.

[0011]

Means for Solving the Problems The characteristics of the oxide solid solution particles of the present invention of claim 1, wherein solving the above-cerium
Oxide solid solution in which zirconium oxide forms a solid solution with oxide
Containing cerium and zirconium in the particles
Is a molar ratio of 0.25 ≦ Zr / (Ce + Zr) ≦
0.75 for cerium oxide in the particles
The solid solubility of the zirconium oxide is 70% or more;
The average diameter of crystallites in the particles is 100 nm or less, and
The specific surface area of the particles is at least 20 m ² / g .

The oxide solid solution particles are desirably used as particles (powder) in which the particles are aggregated to form a powder. These oxide solid solution particles are
It is desirable that the solid solubility is 90% or more.

The oxide solid solution particles according to the present invention are characterized in that at least one of an oxide of an alkaline earth element and an oxide of a rare earth element other than cerium is dissolved in the ceria and zirconia according to claim 1 in a solid solution. Particles containing an oxide solid solution further dissolved in a 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 with respect to ceria and zirconia in the particles. It is desirable that the molar ratio be in the range of 0 <M / (Ce + Zr + M) ≦ 0.15 and that the average diameter of crystallites be 10 nm or less.

[0014] Incidentally, it is more desirable average diameter of the crystallite of the oxide solid solution particles in claim 1 is 12 nm or less, a specific surface area of 35 m ² / g or more, further 50 m ²
/ G or more. A feature of the production method of the present invention according to claim 7 for producing the oxide solid solution particles is that a tetravalent cerium compound and a zirconium compound are used.
Add surfactant and alkaline substance to dissolved aqueous solution
A first step of obtaining a precipitate by heating the precipitate,
The acid in which zirconium oxide is dissolved in cerium oxide
Containing cerium oxide
The solid solubility of zirconium oxide in the material is 50% or more
And the average diameter of crystallites in the particles is 100 nm or less.
And a second step of obtaining certain oxide solid solution particles .

When trivalent cerium is used as a starting material, hydrogen peroxide is added to the aqueous solution in which the trivalent cerium salt and the zirconium salt are dissolved in the first step. A precipitate is obtained by adding a surfactant and an alkaline substance, and the second step is performed in the same manner as in the above production method.

In the above-mentioned production 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 micelle formed by the surfactant preferably has a narrow space inside such as a sphere.
Further , the aqueous solution is supplied for 10 ³ sec.
It is desirable to add the alkaline substance with high-speed stirring at a high shear rate of ^-1 or more .

[0017]

[0018] The average diameter of the crystallite of the oxide solid solution particles produced in claims 7-11, more desirably 12 nm or less, a specific surface area of 35 m ² / g or more, further 50 m ² / G or more.

[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 × (the amount of zirconia dissolved in the total amount of ceria) / the total amount of zirconia (1). Here, there is a relationship represented by 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 same preparation as in Example 1 described later is performed and the lattice constant is measured 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 a composition of ceria / zirconia = 5/5 is shown in FIG. This is performed for each composition, and the lattice constant obtained in the region with a large amount of surfactant is plotted against the zirconia concentration, as shown in FIG. Equation (2) is obtained by rearranging the values by the least square method.

In FIG. 9, the zirconia concentrations are 0% and 100%.
The plot at the time of is the value shown on the JCPDS card. Each plot in FIG. 9 complies with Vegard's law, and it can be determined that 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) where x is obtained by equation (2). The zirconia content C in the sample is determined from the mixing ratio of cerium and zirconium. In the oxide solid solution particles according to the first and fourth aspects of the present invention, 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 μmol O ₂ / g or less. However, if the solid solubility is 50% or more, the OSC is 250-800 μm.
molO ₂ / g or more, which is extremely excellent in oxygen storage ability.

With respect to the oxide A, two or more oxides B,
When C,... Form a solid solution, the solid solubility of any of the two or more 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 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 also be 50% or more.

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 / (βcos 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 are solid solution particles having 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, and further 20 m ² / g.
^It is preferably at least ² / g, more preferably at least 50 m ² / g.

In the oxide solid solution particles of the present invention, for example, in the case of a solid solution of ceria and zirconia, part of the cerium position is replaced by zirconium while maintaining the fluorite structure of cerium oxide to form a zirconia. Is sufficiently dissolved. 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.

Since the average diameter of the crystallites is as small as 100 nm or less, the grain boundaries between the crystallites are large, and the oxygen ions moving through the grain boundaries are easy to move. The oxygen storage capacity is further improved. If the specific surface area is as large as 1 m ² / g or more, since oxygen is absorbed and released at the surface, the rate of oxygen absorption and release is sufficiently high, and excellent oxygen storage capability is exhibited in combination with high OSC.

In the case of a solid solution of ceria and zirconia, the molar ratio of cerium to zirconium is 0.25 ≦ Z
The range of r / (Ce + Zr) ≦ 0.75 is preferable.
The range of 4 ≦ Zr / (Ce + Zr) ≦ 0.6 is particularly preferable. When the content of zirconium becomes 25 mol% or less,
The effect of forming the skeleton of zirconium in the solid solution crystal is weakened, and it becomes difficult to maintain the cubic crystal of the fluorite structure due to the elimination of oxygen.
Decrease. 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.

Since the oxide solid solution particles of the present invention are not in a thermodynamically stable phase, their solid solubility may decrease when used 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 added alkaline earth element oxide or rare earth element oxide other than cerium coexists with the oxide solid solution particles composed of ceria and zirconia, and a part of the oxide is dissolved in the solid solution phase of the oxide solid solution particles. It is not necessary that all be dissolved in the solid solution phase of the oxide solid solution particles. The composition range is such that at least one oxide (M) of an oxide of an alkaline earth element or an oxide of a rare earth element other than cerium is 0 <M / (Ce + Z) with respect to ceria and zirconia.
(r + M) ≦ 0.15 is desirable. The average diameter of crystallites of the oxide solid solution particles is desirably 10 nm or less, and the specific surface area is desirably 20 m ² / g or more. More preferably, it is 50 m ² / g.

The addition of at least one oxide of an alkaline earth element or an oxide of a rare earth element other than cerium to ceria and zirconia improves the stability of the solid solution phase composed of ceria and zirconia in an oxidizing atmosphere at 900 ° C. or higher. With. In order to increase the OSC of the as-produced oxide solid solution particles, the addition of an oxide of an alkaline earth element or an oxide of a rare earth element other than cerium has little effect. Rather, OSC is better for solid solution particles consisting of ceria and zirconia alone. However, when used in a high-temperature oxidizing atmosphere for a long period of time, solid solution particles composed of only ceria and zirconia tend to gradually separate into two phases and lower the OSC. When used under such conditions, solid solution particles to which an oxide of a rare earth element other than an alkaline earth element or 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 oxide (M) of an oxide of an alkaline earth element or an oxide of a rare earth element other than cerium has a molar ratio of 0 <M / c with respect to ceria and zirconia.
If (Ce + Zr + M) ≦ 0.15,
OSC is rather small. In addition, the number of components increases and the cost decreases. When the average diameter of crystallites is greater than 10 nm or the specific surface area is less than 20 m ² / g, the rate of oxygen absorption and desorption decreases, and when used in an atmosphere in which the oxygen partial pressure changes rapidly, OSC becomes smaller.

When an oxide of an alkaline earth element or an oxide of a rare earth element other than cerium forms a solid solution with an oxide solid solution composed of ceria and zirconia, the lattice constant of the crystal changes. It is difficult to determine the solid solubility of. However, it can be determined from the form of the X-ray diffraction peak whether or not the generated single solid solution phase separates into a cerium-based phase and a zirconium-based phase.

[0034] Claim 7 for manufacturing the oxide solid solution particles
In the production method of the present invention described above, a tetravalent cerium compound and
Surfactant and water are added to the aqueous solution in which the zirconium compound is dissolved.
A precipitate is obtained by adding a lukaly substance . Here, the action of the surfactant is not clear, but is presumed as follows. That is, in the state just neutralized with the alkaline substance, the element which becomes an oxide precipitates in the state of a very fine hydroxide or oxide having a particle size of several nm or less. Conventionally, it is dried as it is, but in the present invention, plural kinds of precipitated particles are uniformly taken into micelles 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. Compounds of the elements that become oxides in the form of aqueous solution include cerium (III) nitrate, ammonium cerium (IV) nitrate, cerium (III) chloride, cerium (III) sulfate, cerium (IV) sulfate, zirconium oxynitrate, Zirconium oxychloride and the like are exemplified. In addition, 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, surfactants that can form a narrow space inside the micelles to be formed, such as spherical micelles, are desirable. The critical micelle concentration (cmc) is 0.1 mol
Per liter or less is desirable. More preferably,
A surfactant of 0.01 mol / liter or less is desirable.

Examples of these surfactants include alkylbenzenesulfonic acid and salts thereof, α-olefinsulfonic acid and salts thereof, alkyl sulfate salts, alkyl ether sulfate salts, phenyl ether sulfate salts, and methyl taurate salts. , 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 certain surfactant forms micelles. The addition amount of the surfactant is desirably in the range of 1 to 50 parts by weight based on 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 produced by the above production method. However, in the case of trivalent cerium, since ceria hardly forms a solid solution with zirconia, it is desirable to employ another means.

In the invention according to claim 8 , cerium (III) forms a complex with hydrogen peroxide and is oxidized to cerium (IV), so that ceria can be easily dissolved in zirconia. . The amount of added hydrogen peroxide
Desirably, it is at least 1/4 of cerium ion. If the amount of added hydrogen peroxide is less than 1/4 of the cerium ion, the solid solution of ceria and zirconia becomes 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 timing of adding hydrogen peroxide is not particularly limited, and may be before the addition of the alkaline substance and the surfactant, or simultaneously with or after these. Hydrogen peroxide is a particularly desirable oxidizing agent since post-treatment is not required, but in some cases, other oxidizing agents such as oxygen gas and peroxides such as ozone, perchloric acid, and permanganic acid can be used. .

Furthermore, in the production method of the present invention, the alkaline substance is stirred at a high shear rate of 10 ³ sec ^-1 or more, desirably 10 ⁴ sec ^-1 or more, and the aqueous solution in which plural kinds of elements to be oxides are dissolved is stirred. Rukoto obtain a precipitate by the addition is desirable. A certain amount of segregation is inevitable for components in the precipitated fine particles, which are neutralized products. In the present invention, since the segregation is made uniform and the dispersibility is improved by vigorous stirring, for example, the degree of contact between the cerium source and the zirconium source is further improved.

For example, when coprecipitating from an aqueous solution of a cerium salt and a zirconium salt, the precipitated particles of the same type tend to be aggregated because the two have different precipitation pHs. Thus, by high-speed stirring at a high shear rate, a group of the same type of precipitated fine particles is destroyed, and the precipitated particles are well mixed. Therefore, according to the present invention , the solid solubility can be improved and the average particle size of crystallites can be further reduced. When the shear rate is less than 10 ³ sec ⁻¹ , the effect of promoting solid solution is not sufficient. Note that the shear rate V is represented by V = v / D. Here, v is the speed difference between the rotor and the stator of the stirrer (m / sec).
c) and D is the gap (m) between the rotor and the stator.

The stirring at a high shear rate further promotes solid solution by being applied to the production method of the present invention .
In addition, since solid solution is promoted even when trivalent cerium is used, a solid solution having a high solid solubility even if it is not oxidized to tetravalent with hydrogen peroxide as in the invention of claim 8 according to the present invention. Particles can be produced. In the second step of the production method of the present invention ,
By heating the precipitate, the elements in the precipitate are turned into oxides. The heating atmosphere includes an oxidizing atmosphere, a reducing atmosphere,
Any neutral atmosphere may be used. The element in the precipitate becomes an oxide because 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, an oxide can be obtained even when heated in a reducing atmosphere.

Further, even if a surfactant is not added to the aqueous solution of the raw material, heating the precipitate in a reducing atmosphere in the second step increases the solid solubility of the oxide in the particles, Oxide solid solution particles having a small average crystallite diameter are 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 reduced state, cerium atoms become trivalent in the oxide and oxygen vacancies are formed, and the phase diffusion of cerium and zirconium is facilitated. As a result, the solid solution of ceria and zirconia is easily promoted. Furthermore, zirconium is regularly arranged, and the skeleton of zirconia can be reliably formed in ceria. Further, in the heat treatment in the air, 1600 is required to obtain a sufficient solid solution state.
Although a temperature of at least 100 ° C. is required, the solid solution sufficiently proceeds at a heat treatment temperature of at most 1,300 ° C. in the manufacturing method of claim 10.
Therefore, the size of the formed crystallite becomes small.

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

As the reducing atmosphere, for example, when the reducing atmosphere is made of CO, the CO concentration is preferably 0.1 to 30%. Within this range, the solid solubility is further improved. Examples of the method for collecting the precipitate include a method in which most of the water is squeezed out of the precipitate using a filter press or the like, followed by drying the filter cake, a method in which the precipitate and water are sprayed using a spray dryer or the like, and a method in which the precipitate is dried. Drying of the precipitate can be carried out promptly at 100 ° C. or higher.
Drying at a temperature of 300 ° C. or higher, more preferably 300 ° C. or higher, is preferable because ammonium nitrate generated by the neutralization is easily decomposed and removed.

In the production method of the present invention , any method may be used for heating the precipitate. The heating temperature is desirably in the range of 150 to 600C.
When the heating temperature is lower than 150 ° C., it is difficult to obtain an oxide,
If the temperature exceeds 600 ° C., the obtained oxide may be sintered, and the particles may be aggregated. When drying the precipitate at the time of collection, the drying temperature is set to the heating temperature (150 ° C.).
When the temperature reaches (−600 ° C.), the drying step and the heating step of the precipitate can be used in combination.

In the production method of the present invention , the obtained oxide solid solution particles are preferably subjected to the following post-treatment. That is, in a reducing atmosphere (for example, a state in which a gas such as carbon monoxide, hydrogen, and hydrocarbon is contained),
It is also preferable to perform a heat treatment on the oxide solid solution particles at 0 to 1300 ° C. because the solid solution is promoted. For example, a zirconia skeleton can be surely formed in ceria to increase OSC, which is preferable. As described above, during the heat treatment in the reducing atmosphere, a part of the oxygen in the obtained solid solution is missing, and a part of the cation (cerium) has a low valence (3).
Value). However, if it is heated to about 300 ° C. or more in the air thereafter, it easily returns to the original state. Therefore, during the cooling process after the heat treatment,
In the following, a process of bringing into contact with air and returning to the original valence may also be performed.

When the precipitate is heated by spray drying, oxide solid solution particles are obtained as a powder (dry matter). In the case of using other heating methods, the obtained oxide solid solution particles are in a lump,
Dry pulverization using a hammer mill, a ball mill, a vibration mill, or the like yields a powder composed of oxide solid solution particles.

[0052]

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, and ammonia water was added dropwise with stirring to neutralize the precipitate. 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 obtained slurry was introduced at an introduced air temperature of 400.
The powder was sprayed into an atmosphere at 250 ° C. and an exhaust air temperature of 250 ° C., 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 from the lattice constant by X-ray diffraction and the compounding ratio of the starting materials according to equation (3), and the solid solubility was 100%. The average diameter of the crystallites 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 at a molar ratio of Ce / Zr = 5/5, dispersed in water, and mixed using a ball mill for 48 hours. The obtained slurry was dried at 120 ° C. to obtain a mixed powder. Next, this mixed powder was placed in an alumina crucible and placed in an alumina crucible.
The mixture was heated at 00 ° C. for 5 hours to form a solid solution. After cooling, the mixture was pulverized in a mortar, and further pulverized with water in a ball mill for 48 hours 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 Example ² was 100%, the average diameter of crystallites was 1000 nm, and the specific surface area was 0.3 m ² / g.

Comparative Example 2 An oxide particle was 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, and 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 no surfactant was used. The solid solubility of the oxide particles is 38.
%, The average diameter of the crystallite is 7 nm, and the specific surface area is 70 m ² / g.
Met.

<Evaluation of Heat Resistance> The oxide solid solution particles of Example 1 were heat-treated. FIGS. 1 and 2 show the results of measuring the specific surface area and the average diameter of crystallites after the heat treatment. 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, the oxide solid solution of Example 1 has a high specific surface area of 1 m ² / g or more and a crystallite diameter of 100 nm or less even after the heat treatment at 1200 ° C., although the specific surface area is reduced by the heat treatment. You can see that it is done.

<OSC Measurement> Further, Example 1 and Comparative Examples 1 to
The OSC of each of the oxide solid solution particles No. 3 was 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 μmol O ₂
/ G, whereas the OSCs of the oxide solid solutions of Comparative Examples 1 to 3 were 100, 95, and 150 μmol O ₂ /
g and a considerably low value. It is clear that this result is due to the difference in specific surface area in Comparative Example 1 and the difference in solid solubility in Comparative Examples 2 and 3.

(Example 2) A hydrogen peroxide solution was previously added to an aqueous solution of cerium (III) nitrate and zirconyl nitrate before the aqueous ammonia was dropped, and the operation was performed in the same manner as in Example 1. 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 the crystallite was 10 nm, and the specific surface area was 45 m ² / g.

(Example 3) The same procedure as in Example 1 was carried out except that an aqueous solution of alkylbenzenesulfonic acid was added to an aqueous solution of cerium (III) nitrate and zirconyl nitrate before the aqueous ammonia was dropped. 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 diameter of crystallites was 12 nm, and the specific surface area was 35 m ² / g.

Example 4 An oxide solid solution particle of Example 4 was prepared in the same manner as in Example 1 except that an aqueous solution of α-olefinsulfonic acid was used instead of the aqueous solution of alkylbenzenesulfonic 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 35 m ² / g.

Example 5 An oxide solid solution particle of Example 5 was prepared in the same manner as in Example 1 except that an aqueous solution of polyoxyethylene polypropylalkyl ether was used instead of the aqueous solution of alkylbenzenesulfonic acid. 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 8 nm, and the specific surface area was 40 m ² / g.

Example 6 The procedure of Example 1 was repeated, except that an aqueous solution of cetyltrimethylammonium chloride was used instead of the aqueous solution of alkylbenzenesulfonic 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 was 9
5%, the average diameter of the crystallite is 7 nm, and the specific surface area is 58 m ² /
g.

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

Example 8 An oxide solid solution particle of Example 8 was prepared in the same manner as in Example 1 except that an aqueous solution of polyoxyethylene alkylphenyl ether was used instead of the aqueous solution of alkylbenzenesulfonic acid. Example 1
The solid solubility of the oxide solid solution particles measured in the same manner as described above was 95%, the average diameter of crystallites was 8 nm, and the specific surface area was 50 m.
² / g.

Example 9 An oxide solid solution particle of Example 9 was prepared in the same manner as in Example 1 except that an aqueous solution of polyoxyethylene alkyl ether was used instead of the aqueous solution of alkylbenzenesulfonic 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 is 8 nm, and the specific surface area is 54 m ² / g.
Met.

Example 10 An oxide solid solution particle of Example 10 was prepared in the same manner as in Example 1 except that an aqueous solution of polyoxyethylene alkylamine was used instead of the aqueous solution of alkylbenzenesulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 90.
%, The average diameter of the crystallite is 6 nm, and the specific surface area is 48 m ² / g.
Met.

Example 11 An oxide solid solution particle of Example 11 was 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 alkylbenzenesulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 90.
%, The average diameter of the crystallite 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 in Example 1 except that an aqueous trialkylamine oxide solution was used in place of the aqueous alkylbenzenesulfonic acid solution.
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 average diameter of the crystallite was 9 nm, and the specific surface area was 67 m ² / g.

Example 13 An oxide solid solution particle of Example 13 was prepared in the same manner as in Example 1 except that an aqueous solution of polyoxyethylene alkylmethylammonium chloride was used instead of the aqueous solution of alkylbenzenesulfonic 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, and the specific surface area was 37 m ² / g.

Example 14 An oxide solid solution particle of Example 14 was prepared in the same manner as in Example 1 except that an aqueous solution of tallow diamine dioleic 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 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 therein have the same effect as alkylbenzene sulfonic acid. Example 15 Example 15 was repeated except that the addition amount of the alkylbenzenesulfonic acid was variously selected in the range of 0 to 30% of the weight of the obtained oxide, and the ratio of Ce / Zr in the starting material was changed. In the same manner as in Example 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 is shown in FIG. 3 together with the lattice constant of the oxide solid solution particles of Example 1. FIG. 5 shows the relationship between the lattice constant and the solid solubility calculated from the composition (Ce / Zr = 5/5 in molar ratio) using equation (3).
FIG. 4 shows the relationship between the zirconia content and the lattice constant in each solid solution of ceria and zirconia in each composition. A range corresponding to claim 3 is indicated by oblique lines.

Further, the specific surface area of the oxide solid solution particles was measured for each activator addition ratio of Ce / Zr = 5/5, and is shown in FIG. <Evaluation> As shown in FIG. 3, as the addition ratio of alkylbenzenesulfonic acid increases, the lattice constant decreases, and the addition ratio becomes about 10%.
In the above, the lattice constant is almost constant at 5.275. 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 the alkylbenzenesulfonic acid is 10% or more. If so, it can be seen that they are completely dissolved.
This is supported by the results of FIG. 5 where solid solubility was actually measured. That is, it is apparent that the addition of the surfactant promotes the solid solution, and it is understood that the addition ratio of the alkylbenzenesulfonic acid of about 1% or more is sufficient.

Example 16 After squeezing out water from a slurry containing precipitates 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 to 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 the crystallite was 8 nm, and the specific surface area was 60 m ² / g.

Example 17 A slurry containing a precipitate was mixed with 2
The oxide solid solution particles of Example 17 were prepared in the same manner as in Example 1 except that the powder was brought into contact with a ceramic ball heated to 50 ° C., dried, and mechanically ground by the ball. 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 8 nm, and the specific surface area was 40 m ² / g.

(Example 18) A slurry containing a precipitate was
The oxide solid solution particles of Example 18 were placed in a heating vessel heated to 00 ° C. and heated until water 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 100.
%, The average diameter of the crystallite is 9 nm, and the specific surface area is 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% by weight of the obtained oxide.
Of polyoxyethylene polypropyl alkyl ether and a hydrogen peroxide solution containing hydrogen peroxide in an equimolar amount to Ce ion are added and mixed and stirred. Subsequently, the mixture was neutralized by dropwise addition of aqueous ammonia with stirring to form a precipitate.

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 vessel heated to 250 ° C., and heated until moisture 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 crystallites was 6 nm, and the specific surface area was 80 m ² / g.

The results obtained by subjecting the oxide solid solution particles of Example 19 to heat treatment and measuring the specific surface area and the average diameter of crystallites after the heat treatment are shown in FIG. 6 and FIG. Heat treatment temperature is 300, 60
Five levels of 0, 800, 1000, and 1200 ° C., and heat treatment times are 5 hours, respectively. (Example 20) The oxide solid solution particles obtained in Example 1 were mixed in a reducing atmosphere containing 1% by volume of carbon monoxide for 12 hours.
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 diameter of crystallites 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 of Example 21 were heat-treated at 1100 ° C. for 5 hours in a reducing atmosphere containing 1% by volume of hydrogen gas. 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 μmol O ₂ / g.

<Evaluation> That is, when the oxide solid solution particles of Example 1 were heat-treated in a reducing atmosphere, the average particle diameter was increased to some extent, but the OSC was further increased. (Example 22) The amounts of cerium (III) nitrate and zirconyl nitrate were determined by changing the molar ratio of cerium and zirconium to Ce / Zr.
= Each solid oxide solution particle was prepared in the same manner as in Example 1 except that aqueous solutions mixed variously in the range of 9/1 to 1/9 were used. OSC was measured for each oxide solid solution particle 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 ratio of Ce / Zr was 75
OSC is 250 μm if it is in the range of / 25 to 25/75
It is evident that it is at least olO ₂ / g. FIG. 4
Thus, the zirconia contained in these powders is almost 10%.
It can be seen that a solid solution exists in 0% ceria.

Example 23 Medium without using hydrogen peroxide solution
Stirring at the time of addition and addition of surfactant^Foursec ^-1Less than
As in Example 1 except that the above was performed at a high shear rate.
Thus, the oxide solid solution particles of Example 23 were prepared. Implementation
The solid solution of this oxide solid solution particle was measured in the same manner as in Example 1.
The solubility is 90%, the average diameter of the crystallite is 7 nm, and the specific surface area is 6
0m^Two/ G.

Comparative Example 4 An oxide solid solution particle of Comparative Example 4 was prepared in the same manner as in Example 1 except that no aqueous hydrogen peroxide was 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 the crystallite was 6 nm, and the specific surface area was 85 m ² / g.

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

Example 24 An aqueous solution was prepared by mixing cerium (IV) nitrate and zirconyl nitrate in a molar ratio of Ce / Zr = 5/5, and neutralized by dropwise addition of aqueous ammonia with stirring. To form a precipitate. Subsequently, an aqueous solution containing 10% of alkylbenzenesulfonic acid by weight of the obtained oxide was added and mixed and stirred.

The obtained slurry was introduced at an introduced air temperature of 400.
The solution was sprayed into an atmosphere at a temperature of 250 ° C. and a discharge air temperature of 250 ° C., dried by a spray drying method, and decomposed ammonium nitrate to prepare oxide solid solution particles. Example 1
The solid solubility of the oxide solid solution particles was 100%, the average diameter of the crystallite was 10 nm, and the specific surface area was 5%.
It was 0 m ² / g.

<Evaluation> From the comparison between Comparative Example 2 and Example 24, in the case of cerium (IV), unlike cerium (III), it is possible to form a solid solution with a high solid solubility without using hydrogen peroxide. Understand. Example 25 The procedure of Example 25 was repeated in the same manner as in Example 24, except that an aqueous solution of alkylbenzenesulfonic acid was added to the aqueous solution of cerium (IV) nitrate and zirconyl nitrate before the aqueous ammonia was dropped. 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 crystallites was 1
0 nm, and the specific surface area was 40 m ² / g.

<Evaluation> That is, in Embodiment 25, Embodiment 2
Since a solid solution equivalent to 4 is produced, the time of addition of the surfactant shows the same action regardless of before and after neutralization with the alkali, that is, the action of the surfactant is only when neutralizing with the alkali. It is also found to be effective for the state of the oxide after neutralization with alkali.

Example 26 An oxide solid solution particle of Example 26 was prepared in the same manner as in Example 24 except that an aqueous solution of α-olefinsulfonic acid was used instead of the aqueous solution of alkylbenzenesulfonic 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 crystallite was 8 nm, and the specific surface area was 60 m ² / g.

Example 27 Alkylbenzene Sulfone
Polyoxyethylene polypropyl alcohol instead of acid aqueous solution
Example 24 except that an aqueous alkyl ether solution 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 crystallite is 8 nm, and the ratio is
Surface area is 45m ^Two/ G.

Example 28 The 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 alkylbenzenesulfonic 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 procedure of Example 24 was repeated, except that an aqueous solution of monoalkylammonium acetate was used instead of the aqueous solution of alkylbenzenesulfonic 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 diameter of the crystallite was 8 nm, and the specific surface area was 60 m ^2.
/ G.

Example 30 The 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 alkylbenzenesulfonic 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 55 m ² / g.

Example 31 The procedure of Example 24 was repeated, except that an aqueous solution of polyoxyethylene alkyl ether was used instead of the aqueous solution of alkylbenzenesulfonic acid.
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 diameter of crystallites was 8 nm, and the specific surface area was 57 m ^2.
/ G.

Example 32 An oxide solid solution particle of Example 32 was 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 alkylbenzenesulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 9
0%, the average diameter of the crystallite is 6 nm, and the specific surface area is 45 m ² /
g.

Example 33 An oxide solid solution particle of Example 33 was 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 alkylbenzenesulfonic acid. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 90.
%, The average diameter of the crystallite is 7 nm, and the specific surface area is 59 m ² / g.
Met.

Example 34 The oxide solid solution particles of Example 34 were prepared in the same manner as in Example 24 except that an aqueous solution of a trialkylamine oxide was used instead of the aqueous solution of alkylbenzenesulfonic 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 crystallite is 9 nm, and the specific surface area is 62 m ² / g.
Met.

Example 35 An oxide solid solution particle of Example 35 was prepared in the same manner as in Example 24 except that an aqueous solution of polyoxyethylene alkylmethylammonium chloride was used instead of the aqueous solution of alkylbenzenesulfonic 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 and specific surface area were 30 m ² / g.

Example 36 Example 36 was repeated in the same manner as in Example 24 except that an aqueous solution of tallow diamine dioleic acid was used instead of the aqueous solution of alkylbenzene sulfonic acid.
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 the crystallite was 8 nm, and the specific surface area was 40 m ² / g.

<Evaluation> From the results of Example 24 and Examples 26 to 36, it can be seen that even when hydrogen peroxide was not used, all the surfactants used had the same effect as alkylbenzene sulfonic acid. . (Example 37) After squeezing out water from the slurry containing the precipitate using a filter press, the solid content was dried by heating to 300 ° C and mechanically pulverized, in the same manner as in Example 24. 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 A slurry containing a precipitate was mixed with 2
The oxide solid solution particles of Example 38 were prepared in the same manner as in Example 24 except that the powder was brought into contact with a ceramic ball heated to 50 ° C., dried, and mechanically ground by the ball. 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 8 nm, and the specific surface area was 40 m ² / g.

Example 39 A slurry containing a precipitate was mixed with 3
Placed in a heating vessel heated to 00 ° C., heated until water and ammonium nitrate were evaporated or decomposed and desorbed, and then mechanically pulverized, and the oxide solid solution particles of Example 39 were treated in the same manner as in Example 24. Prepared. The solid solubility of the oxide solid solution particles measured in the same manner as in Example 1 was 10
0%, the average diameter of the crystallite is 9 nm, and the specific surface area is 35 m ² /
g.

<Evaluation> Example 24 and Examples 37 to 39
It is clear from the results that there is no difference depending on the pulverizing means used even when hydrogen peroxide is not used. Example 40 The oxide solid solution particles obtained in Example 24 were mixed in a reducing atmosphere containing 1% by volume of carbon monoxide for 12 hours.
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 diameter of crystallites was 52 nm, and the specific surface area was 5 m ² / g.

Example 41 The oxide solid solution particles of Example 41 were heat-treated at 1100 ° C. for 5 hours in a reducing atmosphere containing 1% by volume of hydrogen gas. 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 44 nm, and the specific surface area was 9 m ² / g.

<Evaluation> That is, when the oxide solid solution particles of Example 24 were heat-treated in a reducing atmosphere, the average particle diameter was increased to some extent even when hydrogen peroxide was not used, but the OSC was further increased. I understand. Example 42 Each oxide solid solution particle was prepared in the same manner as in Example 24 except that the amount of the aqueous solution containing alkylbenzenesulfonic acid was variously selected. The lattice constants of the crystals of these oxide solid solution particles are similar to those shown in FIG. 3, and it is apparent that zirconia forms a solid solution with a high solid solubility without using hydrogen peroxide in the case of tetravalent cerium. is there.

(Example 43) An aqueous solution obtained by variously mixing cerium (IV) nitrate and zirconyl nitrate in a molar ratio of cerium to zirconium in the range of Ce / Zr = 9/1 to 1/9 was used. Except for the above, each oxide solid solution particle was prepared in the same manner as in Example 1. The OSC of each oxide solid solution particle was the same as in FIG. 8, and the lattice constant of the crystal was the same as in FIG.

That is, if it is tetravalent cerium, Ce / Zr
It is clear that if the ratio is in the range of 75/25 to 25/75, the OSC becomes 250 μmol O ₂ / g or more without using hydrogen peroxide. Even without using hydrogen peroxide, a zirconia skeleton is formed in the ceria crystal by solid solution of zirconia. (Example 44) An aqueous solution in which cerium (III) nitrate and zirconyl nitrate were mixed at a molar ratio of Ce / Zr = 5/5 was prepared, and ammonia water was added dropwise with stirring to neutralize the precipitate. Generated. This slurry was dried in the same manner as in Example 1, and further subjected to a heat treatment in the same manner as in Example 20. The solid solubility of the oxide solid solution particles was 80%, the average diameter of crystallites was 48 nm, and the specific surface area was 3 m ² / g.

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

(Example 46) 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 an aqueous solution of yttrium nitrate was further added in a molar ratio of Y / (Y + C
e + Zr) = 0/100 to 10/10. Further, hydrogen peroxide was added so as to have a mole number of の of the cerium ion, and 5% of the weight of the oxide to obtain polyoxyethylene polypropylalkyl ether was added. And neutralized to form respective precipitates. The precipitate was placed in an oven heated to 300 ° C. to evaporate water, and heated until ammonium nitrate and the surfactant were decomposed and eliminated. The average diameter of crystallites of the obtained oxide solid solution particles was 8 nm, and the specific surface area was 70 m ² / g.

These oxide solid solution particles were placed in air at 120
FIG. 10 shows the results of heating at 0 ° C. for 4 hours and examining changes in crystal phases by X-ray diffraction. FIG. 10 shows that the addition of yttrium makes the solid solution phase more stable. Example 47 Each oxide solid solution particle was prepared in the same manner as in Example 46 except that calcium nitrate was used instead of yttrium nitrate. The average diameter of crystallites of the obtained oxide solid solution particles was 7 nm, and the specific surface area was 80 m ² / g.

These oxide solid solution particles were placed in air at 120
FIG. 11 shows the results of heating at 0 ° C. for 4 hours and examining changes in crystal phases by X-ray diffraction. FIG. 11 shows that the addition of calcium makes the solid solution phase more stable. (Example 48) Instead of yttrium nitrate, lanthanum nitrate, magnesium nitrate, strontium nitrate, and barium nitrate were each in a molar ratio of M / (M + Ce + Zr) = 7 /
100, 10/100, 10/100, except that it was used so as to be 10/100, in the same manner as in Example 46,
Each oxide solid solution particle was prepared. The average diameter of 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 at 300 ° C. or 120 ° C. in air.
Baking for 2 hours at 0 ° C.
Was measured. Each result is shown in FIG. 12 together with the result of Example 1. FIG. 12 shows that the oxide solid solution particles of Examples 46 to 48 have the same large OSC as in Example 1, and are more excellent in durability at high temperatures than Example 1.

In the case of Examples 46 and 47, as shown in FIG. 13, it was found that the OSC decreased as the amount of yttrium and calcium increased. That is, a relatively large OSC is maintained until the amount of yttrium and calcium is up to 15 mol%, but when the amount of yttrium and calcium is more than 15 mol%, it is significantly reduced. 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 described above, and the results are shown in FIG. FIG.
The Ce / Zr ratio is 25/75 or less, or 75/25
It can be seen that in the above range, the OSC of the oxide solid solution becomes small.

Example 50 The solid oxide 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 diameter of crystallites was 9 nm, and the specific surface area was 50 m ² / g.

As described above, even when 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 a small average crystallite size. If the solid solution is a solid solution of ceria and zirconia, the ceria has a crystal structure in which a part of the cerium position is replaced by zirconium while maintaining the ceria's fluorite structure. It has a high oxygen storage / release rate and high oxygen storage capability.

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

Further, according to the production method of the present invention, it is considered that when a plurality of elements are co-precipitated, segregation of co-precipitates is suppressed by vigorously stirring the aqueous solution, and the co-precipitates are uniformly dispersed. Therefore, an almost complete solid solution can be obtained while maintaining the average particle size of the crystallites, and the oxide solid solution of the present invention can be easily and reliably produced. In addition, even when trivalent cerium is used, high solid solubility can be ensured without adding hydrogen peroxide.

Further, by heating the precipitate obtained from the aqueous solution in a reducing atmosphere, a substantially complete solid solution can be obtained while maintaining the average diameter of crystallites, and the oxide solid solution of the present invention can be easily and reliably formed. Can be manufactured. In addition, even when trivalent cerium is used, high solid solubility can be ensured without adding hydrogen peroxide.

[Brief description of the 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 a relationship between a heat treatment temperature and an average diameter of crystallites.

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

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

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 a relationship between a heat treatment temperature and a specific surface area.

FIG. 7 is a graph showing a relationship between a heat treatment temperature and an average diameter of crystallites.

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 a relationship between a zirconia concentration in oxide solid solution particles and a 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 amount of calcium added.

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

FIG. 13: Yttrium or calcium addition 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.

Continuing from the front page (72) Inventor Toshio Jintori 41, Chukumi Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Institute, Inc. (1) Inside Toyota Central R & D Laboratories Co., Ltd. (72) Inventor Masataka Sugiura 41 Toyota Chuo R & D Laboratories Co., Ltd. 41, Chuo-ji, Yokomichi, Toyoda Central Research Institute, Inc. (56) References JP-A-8-215569 (JP, A) JP-A-9-40425 (JP, A) JP-A-8-2918 (JP, A) JP-A-7-187676 (JP, A) JP-A-6-198175 (JP, A) JP-A-4-55315 (JP, A) Alloy. Compd. 193 (1993) p. 73-75 Co-hosted by The Catalysis Society of Japan and The Chemical Society of Japan, "Preliminary Proceedings of the 1989 Catalysis Research Conference" (October 13, 14 1989), 3C28, p. 176-177 Toyota Central R & D Review 27 [3] (1992) p. 43-53 J.C. Chem. Soc. Chem. Commun. (November 1995) p. 2181-2182 J.P. Catal. 151 [1] (1995), p. 168-177 (58) Field surveyed (Int. Cl. ⁷ , DB name) C01B 13/14-13/32 B01J 23/10 B01D 53/94 C01F 17/00 C01G 25/00 CA (STN) JICST file ( JOIS)

Claims (24)

(57) [Claims] 1. A particle containing an oxide solid solution in which zirconium oxide is dissolved in cerium oxide, wherein the molar ratio of cerium to zirconium is 0.25 ≦ Zr / (Ce + Zr) ≦ 0. .75, the solid solubility of the zirconium oxide in the particles is 70% or more, the average diameter of crystallites in the particles is 100 nm or less, and the particles are Has a specific surface area of 20 m ² / g or more. 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 35 m ² / g or more. 4. The oxide solid solution particles according to claim 1, wherein the specific surface area of the particles is 50 m ² / g or more. 5. The oxide solid solution particles according to claim 1, wherein the particles have a crystallite diameter of 12 nm or less. 6. The oxide solid solution particles according to claim 1, wherein the particles have a solid solubility of 90% or more. 7. A first step of obtaining a precipitate by adding a surfactant and an alkaline substance to an aqueous solution in which a tetravalent cerium compound and a zirconium compound are dissolved, and heating the precipitate to form a cerium oxide. a particle comprising an oxide solid solution of zirconium oxide is solid-solved, Se in the particles
The molar ratio of lithium and zirconium is 0.25 ≦ Zr
/(Ce+Zr)≦0.75, the solid solubility of the zirconium oxide with respect to the cerium oxide in the particles is 70% or more, and the average diameter of crystallites in the particles is 100 nm or less. And a second step of obtaining oxide solid solution particles, which is a method for producing oxide solid solution particles. 8. A first step of obtaining a precipitate by adding hydrogen peroxide, a surfactant and an alkaline substance to an aqueous solution in which a trivalent cerium compound and a zirconium compound are dissolved, and heating the precipitate. Te, a particle comprising an oxide solid solution of zirconium oxide is dissolved in the cerium oxide, particulate
The ratio of cerium and zirconium in the particles is 0.2
5 ≦ Zr / (Ce + Zr) ≦ 0.75, the solid solubility of the zirconium oxide with respect to the cerium oxide in the particles is 70% or more, and the average diameter of crystallites in the particles A second step of obtaining oxide solid solution particles having a particle size of 100 nm or less, and a method for producing oxide solid solution particles. 9. The surfactant has a critical micelle concentration of 0.5.
The method for producing oxide solid solution particles according to any one of claims 7 to 8, wherein the amount is 1 mol / liter or less. 10. The method for producing oxide solid solution particles according to claim 7, wherein the aqueous solution further contains at least one selected from a rare earth element and an alkaline earth metal. . 11. The production of oxide solid solution particles according to claim 7, wherein the alkaline substance is added while stirring the aqueous solution at a high shear rate of 10 ³ sec ⁻¹ or more at a high speed. Method. 12. Particles containing an oxide solid solution in which zirconium oxide is dissolved in cerium oxide, wherein an oxide of a rare earth element other than cerium oxide is further dissolved in the particles. The molar ratio of cerium to zirconium is in the range of 0.25 ≦ Zr / (Ce + Zr) ≦ 0.75, and the zirconia to the cerium oxide in the particles is
Solid oxide has a solid solubility of 70% or more and a specific surface area of 6 %.
Oxide solid solution particles having a particle size of 0 m ² / g or more. 13. A particle containing an oxide solid solution in which zirconium oxide is dissolved in cerium oxide, wherein at least one kind of alkaline earth metal oxide is further dissolved in the particle. The ratio between cerium and zirconium is
0.25 ≦ Zr / (Ce + Zr) ≦ 0.75
, Wherein the solid solubility of zirconium oxide with respect to the cerium oxide in the particles is 70% or more, and the average diameter of crystallites in the particles is 100 nm or less. particle. 14. The oxide of a rare earth element other than the cerium oxide or the oxide of the alkaline earth metal may be such that the metal M, which is a rare earth element or an alkaline earth metal, has a molar ratio of 0 <0.
The oxide solid solution particles according to claim 12 or 13, wherein the particles are contained in a range of M / (Ce + Zr + M) ≦ 0.15, and the average diameter of the crystallite is 10 nm or less. 15. The oxide solid solution according to claim 12, wherein the oxide of the rare earth element is yttrium oxide, and the oxide of the alkaline earth metal is calcium oxide. particle. 16. A first step of obtaining a precipitate by adding a surfactant and an alkaline substance to an aqueous solution in which a tetravalent cerium compound and a zirconium compound are dissolved, and a second step of heating the precipitate. produced by the production method, a particle comprising an oxide solid solution of zirconium oxide is dissolved in the cerium oxide, cerium in said particle and Jill
The ratio of conium is 0.25 ≦ Zr / (Ce + Z) in molar ratio.
r) is in the range of ≦ 0.75, the solid solubility of zirconium oxide in the particles is 70% or more, and the average diameter of crystallites in the particles is 100 nm or less. Oxide solid solution particles, characterized in that: 17. A first step of obtaining a precipitate by adding hydrogen peroxide, a surfactant and an alkaline substance to an aqueous solution in which a trivalent cerium compound and a zirconium compound are dissolved, and a step of heating the precipitate. produced by more become a manufacturing method and two-step, a particle comprising an oxide solid solution of zirconium oxide is dissolved in the cerium oxide, cerium in said particle and Jill
The ratio of conium is 0.25 ≦ Zr / (Ce + Z) in molar ratio.
r) is in the range of ≦ 0.75, the solid solubility of zirconium oxide in the particles is 70% or more, and the average diameter of crystallites in the particles is 100 nm or less. Oxide solid solution particles, characterized in that: 18. The particles have a specific surface area of 20 m ² / g or less.
Oxide solid solution particles according to any one of claims 16 and claim 17 is an upper. 19. The oxide solid solution particles according to claim 16, wherein the specific surface area of the particles is 35 m ² / g or more. 20. The oxide solid solution particles according to claim 16, wherein the specific surface area of the particles is 50 m ² / g or more. 21. The oxide solid solution particles according to claim 16, wherein the particles have a crystallite diameter of 12 nm or less. 22. The oxide solid solution particles according to claim 16, wherein the particles have a solid solubility of 90% or more. 23. A first step of obtaining a precipitate by adding a surfactant and an alkaline substance to an aqueous solution in which a tetravalent cerium compound and a zirconium compound are dissolved, a second step of heating the precipitate, and Oxide particles 110
Produced by more become a manufacturing method and a third step of reduction treatment between 0 to 1,200 ° C., a particle comprising an oxide solid solution of zirconium oxide is dissolved in the cerium oxide, and cerium in said particle Jill
The ratio of conium is 0.25 ≦ Zr / (Ce + Z) in molar ratio.
r) in the range of ≦ 0.75 and the ceric acid in the particles
The solid solubility of zirconium oxide in chloride is 70% or more
And the average diameter of crystallites in the particles is 100 nm or less,
Oxide solid solution particles having a specific surface area of 1 m ² / g or more. 24. A first step of obtaining a precipitate by adding hydrogen peroxide, a surfactant and an alkaline substance to an aqueous solution in which a trivalent cerium compound and a zirconium compound are dissolved, and a step of heating the precipitate. It is produced by a production method comprising two steps and a third step of reducing the obtained oxide particles at a temperature of 1100 to 1200 ° C, and contains an oxide solid solution in which zirconium oxide is dissolved in cerium oxide. Particles, wherein the cerium and the jill in the particles
The ratio of conium is 0.25 ≦ Zr / (Ce + Z) in molar ratio.
r) in the range of ≦ 0.75 and the ceric acid in the particles
The solid solubility of zirconium oxide in chloride is 70% or more
And the average diameter of crystallites in the particles is 100 nm or less,
Oxide solid solution particles having a specific surface area of 1 m ² / g or more.