JP2005247585A - Method for producing zirconia-ceria compound oxide powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a zirconia-ceria compound oxide exhibiting heat resistance high enough for the compound oxide to keep a high specific surface area even at a high temperature and having a homogeneous solid solution crystal phase by a process which is simple and is industrially advantageous in respect that a high concentration system and low-cost chemicals are used. <P>SOLUTION: The method comprises mixing water-insoluble cerium hydroxide with a zirconium salt in an aqueous solution, heat-treating the mixed slurry containing the cerium component and the zirconium component in a total concentration of 0.1 to 5 mol/L to form hydrated zirconia microparticles and to simultaneously dissolve the cerium hydroxide with the aid of the acid generated by the hydrolysis of the zirconium salt and/or a previously added acid to hydrolytically form zirconia-ceria compound microparticles, subjecting the reaction mixture to solid-liquid separation, drying the separated solid, and calcining the dried solid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a method for producing a zirconia-ceria composite oxide powder that uses cerium hydroxide, which has not been conventionally used, because it is insoluble in water. In addition, this zirconia-ceria composite oxide powder is used as an exhaust gas purifying co-catalyst and exhaust gas purifying catalyst carrier discharged from an internal combustion engine by taking advantage of the characteristics of having a high specific surface area even in a high temperature atmosphere and the ability to generate a uniform solid solution. It can be used for ceramic applications such as solid electrolyte applications and structural material applications.

  As a catalyst for exhaust gas purification of an internal combustion engine, particularly an automobile, a three-way catalyst that purifies by simultaneously performing oxidation reaction of CO and hydrocarbon (HC) in exhaust gas and reduction reaction of nitrogen oxide (NOx) is used. Since the oxidation reaction efficiency of CO and hydrocarbons (HC) and the reduction reaction efficiency of nitrogen oxides (NOx) are greatly affected by the oxygen concentration in the exhaust gas, ceria generally has an oxygen storage / release capacity (OSC). Is added as a cocatalyst, and CO, HC and NOx can be efficiently purified by adjusting the atmospheric fluctuation in the exhaust gas.

  By the way, the ceria used for the exhaust gas purification co-catalyst and the catalyst carrier is reduced in specific surface area due to sintering, agglomeration and grain growth of the ceria particles when exposed to a high temperature exhaust gas atmosphere for a long time. The biggest problem is that the catalyst performance is remarkably lowered due to the aggregation of the noble metal particles and the decrease in oxygen storage / release capability.

  In recent years, exhaust gas regulations have been tightened, and it has been required to improve exhaust gas purification efficiency when starting the engine. The catalyst was arranged. For this reason, the catalyst material has been increasingly required to have improved heat resistance, that is, a material having a high specific surface area at high temperatures and a material with little change.

  In response to such demands, zirconia-ceria composite oxides have been recently used to improve the heat resistance of ceria. Compared with ceria, zirconia-ceria composite oxide has the characteristics of having high heat resistance, that is, maintaining a high specific surface area even at high temperatures and having a high oxygen storage / release capability. The replacement of ceria materials is progressing at a stretch.

  Here, it is known that the oxygen storage / release ability is greatly influenced by the crystal phase of the zirconia-ceria complex, and the oxygen storage capacity is significantly improved by forming a solid solution phase of zirconia-ceria. For this reason, in order to have a high oxygen storage / release capability, it is desired to have a solid solution crystal phase.

Conventionally, the following manufacturing methods are mentioned as a manufacturing method of the zirconia-ceria complex oxide powder used for this use.
(1) A method of coprecipitation by adding ammonia to a mixed aqueous solution of a cerium salt and a zirconium salt, and optionally a third component salt, and calcining it (eg, see Patent Document 1).
(2) A method in which zirconia sol and ceria sol are mixed, alkali is added to the mixed slurry and co-precipitated, and the precipitate is calcined or obtained by using spray drying to obtain a composite dry powder and then calcining (for example, Patent Document 2 and Patent Document 3).
(3) A method in which cerium salt or zirconia salt is added to zirconia sol or ceria sol and neutralized and coprecipitated, and the precipitate is calcined (see, for example, Patent Document 4 and Patent Document 5).
(4) A method of generating various precipitates by adding oxalic acid, carbonate, bicarbonate, or the like to a mixed aqueous solution of cerium salt and zirconium salt, and calcining the precipitate (for example, Patent Document 6 and (See Patent Document 7).
(5) By using peroxodisulfate as an oxidizing agent for cerium (IV) salt and zirconium salt, or cerium (III) salt and zirconium salt, and simultaneously hydrolyzing those salts, ceria and zirconia A method of directly synthesizing powder (for example, see Patent Document 8).
(6) From a liquid mixture containing a zirconium compound and a cerium (IV) compound, heating at a temperature of 100 ° C. or higher, subsequently adding an alkali and coprecipitating, aging the precipitate at a pH higher than pH 8, and then firing (See, for example, Patent Document 9).

However, in the production method (1), a relatively uniform solid solution crystal phase can be easily obtained, but has a drawback that a high specific surface area is hardly obtained by high-temperature treatment. For example, Patent Document 1 describes that the specific surface area when calcined at 1000 ° C. is 18 to 27 m ² / g.
The method (2) is a relatively simple method, but has a disadvantage that a high specific surface area by a high temperature treatment and a uniform solid solution crystal phase cannot be obtained. For example, Patent Document 2 discloses that the specific surface area of the powder produced by this production method is ²⁰ to 25 m ² / g when calcined at 900 ° C., and Patent Document 3 discloses the case where calcined at 900 ° C. The specific surface area is 15 to 35 m ² / g, and X-ray diffraction indicates that the ceria crystal phase and the zirconia crystal phase are separated, and a uniform solid solution crystal phase is not obtained.

The method (3) is a relatively simple method, but a high specific surface area cannot be obtained at a high temperature. For example, Patent Document 5 shows a case where a zirconium salt is added to ceria particles, but there is no description regarding the crystal phase, but the specific surface area when calcined at 900 ° C. is 24-32 m ² / g. Is described. Further, as a result of examination by the present inventors, it has been found that a uniform solid solution crystal phase cannot be obtained by this production method.

In the method (4), a relatively uniform solid solution crystal phase is easily obtained, but it is difficult to achieve a high specific surface area. For example, Patent Document 6 describes that the specific surface area when calcined at 900 ° C. is 28 to 32 m ² / g, and Patent Document 7 is a uniform crystal phase and is temporarily treated at 900 ° C. It is described that the specific surface area when baked is 22 to 35 m ² / g.

In the method (5), for example, in Patent Document 8, the obtained powder is a uniform solid solution crystal phase, and the specific surface area when firing at 1000 ° C. is as high as 40 m ² / g or more. Is obtained. However, since a very dilute solution having a concentration in the solution at the time of hydrolysis of 0.005 to 0.05 mol / L is used, it is necessary to handle an enormous amount of solution, and the used drug ( A special raw material such as ceric ammonium nitrate (NH ₄ ) ₂ Ce (NO ₃ ) ₆ is used as a ceria raw material.) Is also a very expensive chemical, and is an economically disadvantageous manufacturing method.

Even in the method (6), Patent Document 9 discloses that the obtained powder has a uniform solid solution crystal phase and a high specific surface area of 25 to 51 m ² / g when fired at 1000 ° C. It is described that it is obtained. However, as the cerium (IV) compound used, ceric nitrate and ceric ammonium nitrate, which are soluble compounds, are used, but these compounds are generally not commercially available. It can be produced only by a method in which an oxidizing agent such as hydrogen, cerium nitrate and ammonia are reacted under strict conditions, or by a special treatment such as an electrolytic oxidation method.

JP-A-6-63403, page 3, table 1

Japanese Examined Patent Publication No. 8-16015, page 5, Examples, Examples 1 to 7 JP-A-6-279027, page 7, Examples, Examples 1 to 4 JP-A-10-212122, page 6, Examples 1 to 8 Japanese Patent No. 3306147 (JP-A-6-198175), page 5 (Example 1) Table 1 Japanese Patent Application Laid-Open No. H7-16452, page 3, Examples 1 to 3 Japanese National Publication No. 9-506578, page 15, examples 1 to 8 and table 20 on page 1 JP 2001-348223 A, page 5, Example 1 Japanese Patent No. 3490456, page 6, examples 1 to 9

The present invention has been made in view of such circumstances, and maintains a high specific surface area even at high temperatures. For example, the specific surface area when calcined at 800 ° C. is 50 m ² / g or more and calcined at 900 ° C. Zirconia-ceria having a high heat resistance such that the specific surface area is 40 m ² / g or more when calcined, and the specific surface area when calcined at 1000 ° C. is 25 m ² / g or more, and further has a uniform solid solution crystal phase An object of the present invention is to provide a method by which a complex oxide can be produced in an industrially advantageous manner by using a simple process and using a high-concentration and low-cost chemical.

  As a result of intensive studies on the above problems, the present inventors use cerium hydroxide that is insoluble in water as a ceria raw material, and use a zirconium salt that hydrolyzes to generate an acid as a zirconia raw material. In addition, water-insoluble cerium hydroxide and a zirconium salt that generates an acid by hydrolysis are mixed in an aqueous solution, and a mixed slurry having a combined concentration of cerium and zirconium components of 0.1 to 5 mol / L is heat-treated. In this way, hydrated zirconia fine particles are produced, and at the same time, cerium hydroxide is dissolved by the generated acid, and zirconia-ceria composite fine particles are produced by hydrolysis, followed by solid-liquid separation, drying and calcining. When the zirconia-ceria composite oxide powder is produced, the zirconia-ceria composite oxide powder exhibits a high specific surface area and exhibits a uniform solid state. Leading to the present invention found that a body crystalline phase.

  Hereinafter, the present invention will be described in more detail.

As the ceria raw material of the present invention, cerium hydroxide insoluble in water is used. Here, the cerium hydroxide is represented by the general formula _{Ce (OH) 4 · nH 2} O, CeO 2 · 2H 2 O, CeO 2 · 3H 2 O, 8CeO 2 · 10H 2 O, 8CeO 2 · 11H 2 Contains so-called hydrated ceria such as O. Cerium hydroxide is an insoluble compound, but is characterized by being reactive in the acidic region. Such cerium hydroxide is a raw material that can be obtained relatively inexpensively, and is also an economically advantageous material.

  The particle size of the cerium hydroxide is not particularly limited, but it is desirable to perform normal pulverization in advance to sharpen the particle size distribution, and the preferable particle size is from 0.1 μm to 5 μm in average particle size. This is because if it is smaller than 0.1 μm, it is difficult for ordinary pulverization treatment, and if it is larger than 5 μm, the reaction hardly occurs. The pulverization treatment is not limited at all, but wet pulverization with a ball mill or a bead mill is preferable. This is because the cerium hydroxide slurry obtained by such a treatment exhibits high activity, and thus becomes more easily reactive particles.

  Moreover, as a zirconia raw material used by this invention, the zirconium salt which hydrolyzes and produces | generates zirconia by heating in aqueous solution state is used. Specific examples include zirconium oxychloride (zirconyl chloride), zirconium chloride, zirconium oxynitrate (zirconyl nitrate), zirconium nitrate, and zirconium sulfate.

In the present invention, what is important is that a hydrolysis reaction occurs by heating the zirconium salt solution. Specifically, the hydrolysis reaction is represented by the following reaction formula.
Zr ⁴⁺ + (n + 2) H ₂ O → ZrO ₂ .nH ₂ O + 4H ⁺
ZrO ²⁺ + (n + 1) H ₂ O → ZrO ₂ .nH ₂ O + 2H ⁺
ZrO ₂ · nH ₂ O (hydrated zirconia) produced by the above reaction formula can form fine particles to form a hydrated zirconia sol.

  Here, cerium hydroxide used as a ceria raw material is generally insoluble in water and exists in a slurry state. In the present invention, it is extremely important that the hydrolysis reaction be performed in a slurry state in which cerium hydroxide present in the slurry state and a zirconia salt capable of hydrolysis reaction are mixed. By performing the hydrolysis reaction in such a state, zirconia-ceria composite fine particles having a uniform composition and high heat resistance can be formed.

The generation mechanism of the zirconia-ceria composite fine particles having a uniform composition and high heat resistance is not clear, but the following may be considered. In the zirconium salt, an acid is generated at the same time as the hydrolysis reaction is started by the above reaction formula by heating. This acid reacts with solid phase cerium hydroxide and is partially dissolved. The dissolved cerium at this time is dissolved in a state such as CeO ²⁺ or Ce (OH) ³⁺ ion, not a complete Ce ⁴⁺ ion state, although it depends on the state of aqueous solution such as acid concentration and anion. it is conceivable that. Here, the amount of the cerium hydroxide dissolved can be controlled by controlling the acid concentration, and the reaction in a high concentration system is also possible.

On the other hand, it is considered that zirconium is present in a state like ZrO ²⁺ ions at the early stage of hydrolysis of the zirconium salt, and these ionic species can be precursors of hydrated zirconia fine particles. Such a precursor of hydrated zirconia fine particles and an ionic species generated from cerium hydroxide are coexisted, thereby being easily combined and having a uniform composition. In addition, it is considered that the composite fine particles once formed are crystalline particles with a more uniform composition by repeating dissolution and precipitation by heat treatment, and are considered to be composite fine particles having excellent heat resistance. .

In the present invention, it is also possible to add an acid in advance to the mixed slurry. The addition of acid can increase the hydrolysis rate of the zirconium salt, control the amount of cerium hydroxide dissolved, reduce the processing time, and provide a highly concentrated slurry system, which is economically advantageous. Become. Examples of the acid to be added include hydrochloric acid, nitric acid, sulfuric acid, carbonic acid, and organic acids. It is preferable to use hydrochloric acid and nitric acid. The amount of acid added in advance is preferably 20 times or less of the amount of H ⁺ produced in accordance with the reaction formula. This is because if it is 20 times or more, it does not exist in a form that acts as a precursor of complex oxide fine particles such as CeO ²⁺ ions and ZrO ²⁺ ions shown in the particle generation mechanism, and it is difficult to be compounded.

Here, the mixing ratio of the cerium hydroxide and the zirconium salt can be generated with a desired composition, but in order to obtain a highly heat-resistant zirconia-ceria composite oxide, it is converted into ZrO ₂ / CeO ₂ . The molar ratio is 95/5 to 5/95, preferably 80/20 to 30/70.

  Further, by allowing the mixed slurry to coexist with at least one or more third components other than zirconia and ceria, a zirconia-ceria composite oxide powder that can further maintain high heat resistance, that is, a high specific surface area at high temperature, is obtained. be able to. Here, as the third component, hafnium, rare earth elements (especially yttrium, lanthanum, praseodymium, neodymium, gadolinium, ytterbium, samarium, scandium), alkaline earth elements (especially magnesium, calcium, barium), aluminum, bismuth, Examples include nickel, manganese, boron, and titanium. Such an element is obtained as a composite oxide by adding at least one kind of element into a mixed slurry in the form of a salt, for example, chloride, nitrate, carbonate, sulfate or the like, or an oxide sol. It becomes possible.

  The amount of the third component added is preferably 20 mol% or less. This is because the effect of preventing solid solution of ceria and zirconia works at 20 mol% or more.

  As for the said heat processing temperature, 80 to 250 degreeC is desirable. This is because the hydrolysis rate of the zirconium salt becomes extremely slow at 80 ° C. or less, and the load on the pressure device such as an autoclave becomes extremely large at 250 ° C. or more. In addition, the heat treatment time requires about 1 hour to 10 days for the reaction to proceed completely.

  The slurry concentration in the present invention is required to be 0.1 mol / L to 5 mol / L in terms of oxide by combining the zirconia-ceria component or the zirconia-ceria-third component. is there. If the concentration is 0.1 mol / L or less, the amount of slurry to be processed becomes enormous, which is economically disadvantageous. If the concentration is 5 mol / L or more, it becomes a highly viscous slurry and is extremely difficult to handle. Because it becomes.

  The resulting microparticles can then be recovered by any solid-liquid separation technique, such as filtration or centrifugation. A preferred embodiment is a method of agglomerating by adding an alkali and filtering as a precipitate. In this case, examples of the alkali used include ammonia, alkali metal hydroxides, amines, and the like, but it is desirable to use ammonia because a high-purity precipitate can be obtained. Moreover, precipitation can be efficiently produced | generated by setting pH after addition to 8-10.

  Subsequently, in the present invention, the obtained fine particles can be washed with water and dried at 60 ° C. to 200 ° C. to obtain a dried composite oxide. Although there is no restriction | limiting in particular about the washing method, For example, the method of resuspending the solid-liquid-separated deposit in pure water and re-filtering is mentioned. The amount of water for washing may be 1 to 50 times the amount of the precipitate.

  A dried product can also be obtained by directly spray-drying the zirconia-ceria composite oxide fine particle slurry. Moreover, it is also possible to wash and concentrate by using an ultrafiltration membrane in a slurry state of composite oxide fine particles before spray drying.

  Subsequently, the obtained dried product is calcined at 300 ° C. to 1000 ° C., whereby a zirconia-ceria composite powder having a uniform solid solution crystal phase can be obtained.

In the case of this calcination, it can process in a reducing atmosphere. By processing in a reducing atmosphere, it is possible to obtain a zirconia-ceria composite powder having a more uniform solid solution crystal phase. The reducing atmosphere can be easily achieved by coexisting a reducing gas such as H ₂ or CO. If the H ₂ or CO gas concentration is about 10% or less, the effect of promoting solid solution can be obtained.

As described above, by the production method of the present invention, a high specific surface area is maintained even at a high temperature. For example, the specific surface area when calcined at 800 ° C. is 50 m ² / g or more and calcined at 900 ° C. A zirconia-ceria composite oxide having a specific surface area of 40 m ² / g or more and high heat resistance such that the specific surface area when calcined at 1000 ° C. is 25 m ² / g or more and further having a uniform solid solution crystal phase Can be produced industrially advantageous by using a simple process and using a high-concentration and low-cost chemical.

  Hereinafter, although an Example demonstrates in detail, this invention is not limited to this Example at all.

Example 1
To 500 g of distilled water, 21.7 g of cerium (IV) hydroxide hydrate (first grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) (corresponding to 16.7 g in terms of cerium oxide), zirconium oxychloride octahydrate (Kishida Chemical) 46.0 g (equivalent to 17.6 g in terms of zirconium oxide) and 4.6 g (equivalent to 2.0 g in terms of lanthanum oxide) of lanthanum chloride heptahydrate (first grade reagent made by Kishida Chemical Co., Ltd.) That is, a mixed slurry having a concentration of 0.5 mol / L was prepared. Subsequently, the mixed slurry was heated to 100 ° C. with stirring, and then hydrolyzed for 168 hours to obtain a solution containing zirconia-ceria composite fine particles. Next, after cooling the solution, a 2.8% aqueous ammonia solution was added while stirring until the pH of the solution reached 9.0, thereby agglomerating the composite fine particles. After filtering this aggregate, it was washed with 800 mL of distilled water (22 times the amount of complex oxide), and the resulting precipitate was dried at 110 ° C. Next, the obtained dry powder was baked at 800 ° C. for 5 hours in an air atmosphere to obtain a zirconia-ceria-based composite oxide powder. The resulting composite powder had a BET specific surface area of 60 m ² / g. Also, the powder 900 ° C., was fired for 5 hours at 1000 ° C., and the BET specific surface area, respectively ^47m 2 / g, was ^{28 m} 2 / g.

Example 2
500 g of distilled water was mixed with 21.7 g of cerium hydroxide (IV) n hydrate (equivalent to 16.7 g in terms of cerium oxide), 46.0 g of zirconium oxychloride octahydrate (equivalent to 17.6 g in terms of zirconium oxide) and chloride 4.6 g of lanthanum heptahydrate (corresponding to 2.0 g in terms of lanthanum oxide) was added, that is, a mixed slurry having a concentration of 0.5 mol / L was prepared. Subsequently, the mixed slurry was heated to 100 ° C. with stirring, and then hydrolyzed for 168 hours to obtain a solution containing zirconia-ceria composite fine particles. Next, the solution was cooled to room temperature, and then spray-dried under conditions of an inlet gas temperature of 180 ° C. to obtain a dry powder of composite fine particles.

The obtained dry powder was baked at 800 ° C. for 5 hours in an air atmosphere to obtain a zirconia-ceria based composite oxide powder. The obtained composite powder had a BET specific surface area of 55 m ² / g. Also, the powder 900 ° C., was fired for 5 hours at 1000 ° C., and the BET specific surface area, respectively ^41m 2 / g, was ^26m 2 / g.

Example 3
The dried powder obtained in Example 1 was reduced and fired at 700 ° C. for 2 hours in a 2 vol% hydrogen-nitrogen atmosphere. It was 82 m < ² > / g when the BET specific surface area of the obtained powder was measured. Subsequently, it was calcined at 800 ° C., 900 ° C., and 1000 ° C. for 5 hours in an air atmosphere to obtain a zirconia-ceria based composite oxide powder. The BET specific surface areas of the obtained composite powder were 59 m ² / g, 42 m ² / g and 29 m ² / g, respectively.

Comparative Example 1
1000 g of distilled water, 64.4 g of cerium (III) nitrate hexahydrate (special grade reagent manufactured by Kishida Chemical Co., Ltd.) (corresponding to 25.5 g in terms of cerium oxide), zirconium nitrate dihydrate (special grade reagent manufactured by Kishida Chemical Co., Ltd.) ) 54.8 g (equivalent to 25.3 g in terms of zirconium oxide) and 2.7 g (equivalent to 0.8 g in terms of yttrium oxide) of yttrium nitrate n hydrate (99.99% reagent, Wako Pharmaceutical Co., Ltd.) While stirring this mixed solution, 1 L of 150 g / L aqueous ammonium bicarbonate solution was quickly added to obtain a composite carbonate precipitate. The precipitate was filtered, washed with water, and dried at 110 ° C.

The obtained dry powder was baked at 800 ° C. for 5 hours in an air atmosphere to obtain a zirconia-ceria based composite oxide powder. The BET specific surface area of the obtained composite powder was 43 m ² / g. The powder addition 900 ° C., was calcined for 5 hours at 1000 ° C., BET specific surface area was respectively ^{35m 2 / g, 16m 2 /} g.

Comparative Example 2
Dissolve 26.0 g (corresponding to 13.3 g in terms of cerium oxide) of cerium (III) acetate monohydrate (first grade reagent manufactured by Kishida Chemical Co., Ltd.) in 1500 g of distilled water, and then 22.7 g of 35% aqueous hydrogen peroxide. Was added. This solution was heated to 100 ° C. and subjected to a hydrolysis reaction for 1 hour to obtain a cerium oxide sol. The average particle size was 100 angstroms. Separately, a 0.05 mol / L zirconium oxychloride solution was prepared, heated to 100 ° C. with stirring, and subjected to a hydrolysis reaction for 168 hours to obtain a zirconium oxide sol. The average particle diameter of the obtained zirconium oxide was 660 angstroms. This zirconia sol is separated by an ultrafiltration membrane, washed with water, and distilled water is added again to obtain 281 g of zirconium oxide sol (corresponding to 9.6 g in terms of zirconium oxide) containing 3.4% by weight of zirconium oxide. It was. This zirconium oxide sol was added to the cerium sol solution and mixed. Next, the mixed sol was spray-dried at an inlet gas temperature of 180 ° C. to obtain a dry powder of mixed fine particles.

The obtained dried powder was baked at 800 ° C. for 5 hours in an air atmosphere to obtain a zirconia-ceria composite oxide powder. The BET specific surface area of the obtained composite powder was 39 m ² / g. When this powder was fired at 900 ° C. and 1000 ° C., the BET specific surface area was 29, 19 m ² / g.

Comparative Example 3
Dissolve 74.0 g of cerium (III) nitrate hexahydrate in 311 g of distilled water. Separately, zirconia sol having an average particle size of 660 angstroms obtained by hydrolysis reaction of zirconium oxychloride is filtered, washed with water, and washed with ZrO. ₂ , 615 g of zirconia sol contained in 3.4% by weight was added and mixed. Next, while stirring the mixed solution, 2.8% aqueous ammonia solution was added until the pH of the solution reached 9.0 to obtain a mixed precipitate. The precipitate was filtered, washed with water, and dried at 110 ° C.

The obtained dried powder was baked at 800 ° C. for 5 hours in an air atmosphere to obtain a zirconia-ceria composite oxide powder. The obtained composite powder had a BET specific surface area of 46 m ² / g. The resulting powder was 900 ° C., was calcined for 5 hours at 1000 ° C., BET specific surface area was respectively ^{34m 2 / g, 23m 2 /} g.

Comparative Example 4
Dissolve 64.4 g of cerium (III) nitrate hexahydrate (equivalent to 25.5 g in terms of cerium oxide) and 54.8 g of zirconium nitrate dihydrate (equivalent to 25.3 g in terms of zirconium oxide) in 1000 g of distilled water, While stirring the mixed solution, 1 L of 150 g / L aqueous ammonium bicarbonate solution was quickly added to obtain a composite carbonate precipitate. The precipitate was filtered, washed with water, and dried at 110 ° C.

The obtained dried powder was reduced and fired at 700 ° C. for 2 hours in a 2 vol% hydrogen-nitrogen atmosphere. The BET specific surface area of the obtained powder was 50 m ² / g. Next, it was calcined at 800 ° C., 900 ° C., and 1000 ° C. for 5 hours in an air atmosphere to obtain a zirconia-ceria composite oxide powder. The BET specific surface areas of the obtained composite powder were 45 m ² / g, 36 m ² / g, and 24 m ² / g, respectively.

Claims (6)

Water-insoluble cerium hydroxide and zirconium salt are mixed in an aqueous solution, and a mixed slurry having a combined concentration of cerium and zirconium components of 0.1 to 5 mol / L is heat-treated to produce hydrated zirconia fine particles. At the same time, cerium hydroxide is dissolved with an acid, and zirconia-ceria composite fine particles are formed by hydrolysis, followed by solid-liquid separation, drying and calcining. Manufacturing method. The zirconia-ceria composite oxide powder according to claim 1, wherein the acid is an acid generated by hydrolysis of a zirconium salt and / or an acid added in advance before heat-treating the mixed slurry. Method. Adding a salt or sol of a third component other than cerium and zirconium to the aqueous solution, and subjecting the mixed slurry having a concentration of 0.1 to 5 mol / L to the combined concentration of the cerium component, the zirconium component and the third component to heat treatment. The method for producing a zirconia-ceria composite oxide powder according to claim 1 or 2, wherein the zirconia-ceria composite oxide powder is characterized. The zirconia-ceria composite according to claim 3, wherein the third component contains at least one of hafnium, rare earth elements, alkaline earth elements, aluminum, bismuth, nickel, manganese, boron, and titanium. Manufacturing method of oxide powder. The rare earth element is any element of yttrium, lanthanum, praseodymium, neodymium, gadolinium, ytterbium, samarium, or scandium, and the alkaline earth element is any element of magnesium, calcium, or barium. The manufacturing method of the zirconia-ceria complex oxide powder of Claim 4. The method for producing a zirconia-ceria composite oxide powder according to any one of claims 1 to 5, wherein the atmosphere during the calcination is a reducing atmosphere.