JP6042185B2 - Method for producing ceria-zirconia composite oxide material and ceria-zirconia composite oxide material obtained by this method - Google Patents

Description

  The present invention relates to a method for producing a ceria-zirconia composite oxide material and a ceria-zirconia composite oxide material obtained by this method.

Ceria (CeO ₂ ) has a high oxygen storage capacity (hereinafter also referred to as OSC) for releasing oxygen, and is applied as an oxygen storage material (co-catalyst) for exhaust gas purification catalysts for vehicles such as automobiles. In addition, there are various uses including abrasives.

For example, as a ceria-based material for use as the oxygen storage material described above, a composite oxide of ceria and zirconia or a solid solution thereof is known by adding zirconia (ZrO ₂ ) to ceria. By adding zirconia to ceria, a decrease in OSC due to crystal growth of ceria at high temperatures is suppressed, and high temperature durability is improved. In particular, there is a composite oxide having a pikurore phase (Patent Document 1). The ceria-zirconia composite oxide having a pi-croa phase releases oxygen and exhibits a pi-croa phase in an oxygen-poor atmosphere, but in the oxygen-rich atmosphere, the oxygen is occluded in oxygen vacancies in the bi-chloroa phase and becomes a κ phase. Therefore, a good OSC can be exhibited.

JP 2003-277059 A

  In recent years, exhaust gas regulations have become stricter year by year, and it is desired to have exhaust gas purification performance even at lower temperatures. Here, if the amount of the oxygen storage material in the catalyst is reduced, the heat capacity of the catalyst can be reduced, and the catalyst can be activated at an early stage of operation. In order to reduce the content of the oxygen storage material in the catalyst, further improvement of OSC is required.

  As for the ceria-zirconia composite oxide having the above-described picroa phase, a method in which ceria and zirconia are mixed and baked in an inert atmosphere of 1200 ° C. or higher is used. However, this method has a problem that good OSC cannot be expected because grains grow to several microns.

  Accordingly, an object of the present invention is to provide a more practical and improved ceria-zirconia composite oxide material and a method for producing the same.

  The inventors of the present invention have studied various methods for producing the composite oxide material for enhancing the properties of the ceria-zirconia composite oxide material. As a result, the ceria-zirconia composite oxide contains a hydroxy group containing at least two hydroxy groups. It has been found that a ceria-zirconia composite oxide having a pyrochlore phase can be obtained by suppressing the particle growth by synthesizing by hydrothermal reaction in the presence of a compound, followed by reduction firing and oxidation firing. According to the present invention, the following means are provided based on these findings.

  The method for producing a ceria-zirconia composite oxide material disclosed in the present specification contains water, cerium ions, zirconium ions, and a hydroxy group-containing compound containing at least two hydroxy groups, and is alkaline. Heating the raw material liquid, performing a hydrothermal reaction to obtain a complex of the ceria-zirconia complex oxide and the hydroxy group-containing compound, and firing the complex in a reducing atmosphere to ceria A step of obtaining a first fired body including a zirconia composite oxide phase and a carbide phase; and firing the first fired body in an oxidizing atmosphere to remove the carbide phase in the first fired body. And obtaining a second fired body mainly composed of a ceria-zirconia composite oxide phase.

  The manufacturing method may further include a step of holding the additional hydroxy group-containing compound in the composite after the composite acquisition step and prior to the first fired body acquisition step. The holding step may be a step of supplying a solution of an additional hydroxy group-containing compound to the complex and removing at least a part of the liquid content of the solution from the complex. Furthermore, you may perform the said hydrothermal reaction at 50 to 200 degreeC. Further, the hydroxy group-containing compound may be glycolic acid.

  The ceria-zirconia composite oxide material disclosed in this specification can be obtained by the above production method. This ceria-zirconia composite oxide material may be an oxygen storage material for an exhaust gas purification catalyst of an internal combustion engine.

  The exhaust gas purification apparatus disclosed in the present specification can include a catalyst phase containing the ceria-zirconia composite oxide material.

It is a figure which shows an example of the flow of the manufacturing method of the ceria-zirconia complex oxide material of this invention. It is a figure which shows an example of the flow of the manufacturing method of the ceria-zirconia complex oxide material of this invention. It is a figure which shows another example of the flow of the manufacturing method of the ceria-zirconia complex oxide material of this invention. It is a figure which shows another example of the flow of the manufacturing method of the ceria-zirconia complex oxide material of this invention. It is a figure which shows the X-ray-diffraction spectrum of the 1st baking body obtained in the Example, and the 2nd baking body. It is a figure which shows the evaluation result of the 2nd sintered body obtained in the Example.

  The present invention relates to a method for producing a novel ceria-zirconia composite oxide material and a ceria-zirconia composite oxide material obtained by the production method.

  One example of the method for producing the ceria-zirconia composite oxide material of the present invention is shown in FIGS. According to the production method of the present invention, for example, as shown in FIG. 1, a composite of a hydroxy group-containing compound containing at least two hydroxy groups and a cerium-zirconium hydroxide is obtained by a hydrothermal reaction. By firing the composite in a reducing atmosphere and then in an oxidizing atmosphere, a ceria-zirconia composite oxide material having a pyrochlore phase (κ phase in the oxidized state) can be obtained without particle growth. .

  That is, a hydrothermal reaction obtains a complex of a ceria-zirconia complex oxide and a hydroxy group-containing compound as an insoluble component, and the complex is fired in a reducing atmosphere to obtain a cerium-zirconium hydroxide. A first fired body having a derived ceria-zirconia composite oxide phase and a carbide phase derived from the hydroxy group-containing compound can be obtained. Furthermore, when the first fired body is fired in an oxidizing atmosphere, a second fired body mainly including a ceria-zirconia composite oxide phase having a κ phase from which the carbide phase has been removed can be obtained.

  According to this manufacturing method, since the composite in which the hydroxy group-containing compound is dispersed in cerium-zirconium hydroxide is fired in a reducing atmosphere, the particle growth of the composite oxide phase is suppressed by the carbide phase. A pyrochlore phase can be obtained. Then, the ceria-zirconia composite oxide having a κ phase in which grain growth is suppressed can be obtained by removing the carbide phase by firing in an oxidizing atmosphere.

  Furthermore, for example, as shown in FIG. 2, the complex obtained by the hydrothermal reaction is dispersed in a hydroxy group-containing compound solution and then concentrated, whereby the complex can additionally hold the hydroxy group-containing compound. . According to such a composite, it is possible to obtain a pyrochlore phase in which grain growth is further suppressed by firing in a reducing atmosphere, and thus a ceria-zirconia composite oxide phase having a κ phase.

  Hereinafter, a method for producing a ceria-zirconia composite oxide material disclosed in this specification and a ceria-zirconia composite oxide material obtained by this production method will be described with reference to the drawings as appropriate.

(Method for producing ceria-zirconia composite oxide material)
The ceria-zirconia composite oxide material of the present invention can be produced by performing the following steps. An example of the manufacturing method is shown in FIG. 1 (FIGS. 1A and 1B) and FIG. 2 (FIGS. 2A and 2B).

(A) Hydrothermal reaction step (b) First firing step (c) Second firing step

(Hydrothermal reaction process)
The hydrothermal reaction step includes water, a cerium raw material, a zirconium raw material, and a hydroxy group-containing compound containing at least two hydroxy groups. It is a process of implementing. According to this step, a complex of the ceria-zirconia complex oxide and the hydroxy group-containing compound can be obtained at least partially. In the hydrothermal reaction step, it is considered that a ceria-zirconia composite oxide is produced at least partially from the cerium raw material and the zirconium raw material through the respective hydroxides.

  The raw material liquid for the hydrothermal reaction contains water, a cerium raw material, a zirconium raw material, and a hydroxy group-containing compound containing at least two hydroxy groups, and is adjusted to be alkaline. Preferably, a cerium raw material, a zirconium raw material, and a hydroxy group-containing compound containing at least two hydroxy groups are added and mixed, and then the mixture is further made alkaline to prepare a uniform liquid.

  Examples of the cerium raw material and the zirconium raw material include, but are not limited to, various water-soluble cerium salts and zirconium salts. For example, inorganic salts such as nitrates, sulfates, sulfites, chlorides, and various inorganic complex salts, and organic salts such as carboxylates, halogenated oxoacid salts, and various organic complex salts can be used. The cerium raw material and the zirconium raw material are preferably blended so that the molar ratio of cerium (Ce) and zirconium (Zr) is approximately 1: 1.

  The raw material liquid contains a hydroxy group-containing compound. By including the hydroxy group-containing compound, nanoparticles having a uniform composition as a ceria-zirconia composite oxide can be formed in the hydrothermal reaction step. Although not restricting the disclosure of this specification, it is inferred as follows. Cerium and zirconium ions are initially in the form of bare ions (hydrated state) in aqueous solution, but they are partially insoluble in water by chelating by adding hydroxy group-containing compounds and making them alkaline. Although the hydroxide begins to be generated, the presence of the hydroxy group-containing compound allows the hydroxide to be retained in the raw material solution without precipitation. In addition, the presence of a chelate with a hydroxy group-containing compound suppresses the growth of large hydroxide particles and maintains the level at a level smaller than that of the nanoparticles. By heating this raw material liquid and carrying out a hydrothermal reaction, it is possible to grow to ceria-zirconia composite oxide nanoparticles. That is, the hydroxy group-containing compound once deviates from the ions in the solution, the ions grow as inner hydroxide particles (composite oxide particle core) as hydroxides, and the hydroxy group-containing compounds chelate with the ions on the core surface to form the core. It is considered that fine composite oxide particles can be obtained because they are adsorbed on the outside in a shell shape and continue to suppress grain growth.

  Examples of hydroxy group-containing compounds include hydroxy acids. Hydroxy acids include glycolic acid, lactic acid, tartronic acid, glyceric acid, hydroxybutyric acid, malic acid, tartaric acid, citric acid, shikimic acid and other aliphatic hydroxy acids, monohydroxybenzoic acid derivatives, dihydroxybenzoic acid derivatives, trihydroxybenzoic acid Aromatic hydroxy acids such as acid derivatives and phenylacetic acid derivatives are exemplified. Typically, for example, glycolic acid or the like is used.

  Such a hydroxy group-containing compound is preferably blended in a molar ratio of 1 mol or more and 4 mol or less with respect to cerium raw material or zirconium raw material cerium or zirconium. This is because if the amount of the hydroxy group-containing compound is less than or exceeds this range, it becomes difficult to obtain a ceria-zirconia composite oxide in which grain growth is suppressed. Moreover, it is because the problem of melt | dissolution of a ceria and a zirconia component will arise when too much. More preferably, it is 2 or more and 3 or less.

  The raw material liquid contains water and alkali in addition to the cerium raw material, the zirconium raw material, and the hydroxy group-containing compound. Although the density | concentration of the cerium raw material and zirconium raw material in a raw material liquid is respectively not specifically limited, It is preferable that it is about 0.01M-1M. More preferably, it is about 0.05 to 0.5M. The alkali may be an inorganic alkali or an organic alkali, but an organic alkali containing no metal element is preferable. Typically, an ammonia solution or the like can be used. This is because the ceria-zirconia composite oxide has good dispersibility when the pH of the raw material liquid is in the range of pH 10 or less, preferably from about pH 8 to about pH 10 or less. The raw material liquid in such a pH range can be obtained by setting the ammonia concentration in the normal raw material liquid to about 0.3M to 0.7M, typically about 0.5M.

  The raw material solution thus prepared is a clear solution in which the cerium raw material, the zirconium raw material, and the hydroxy group-containing compound are dissolved in an aqueous medium before the hydrothermal reaction.

  Hydrothermal reaction conditions are not particularly limited, and the raw material liquid is heated to 50 ° C. or higher, preferably 70 ° C. or higher, more preferably 80 ° C. or higher, still more preferably 90 ° C. or higher, more preferably 100 ° C. or higher. Furthermore, it is preferably 120 ° C. or higher, and more preferably 140 ° C. or higher. In order to secure such a heating state, a hydrothermal reaction is usually performed under a pressure vessel. Although the heating time depends on the heating temperature, it is preferably heated for several hours or more, more preferably 10 or more hours. Typically, the hydrothermal reaction is carried out in 20 hours or less.

  As shown in FIG. 1A, by performing a hydrothermal reaction, a complex of ceria-zirconia composite oxide particles and a droxy group-containing compound attached to the particles can be obtained as a water-insoluble precipitate. . By forming such a composite, when the composite is baked in a reducing atmosphere to obtain a ceria-zirconia composite oxide, a carbide phase is generated from the hydroxy group-containing compound and the composite oxide particles are bonded to each other. Thus, it is considered that the grain growth can be suppressed.

  This complex is easily obtained from the raw material liquid by solid-liquid separation from the raw material liquid after the reaction. The solid-liquid separation means is not particularly limited, and known solid-liquid separation means can be employed. Depending on the particle size of the generated insoluble matter, typically, an ultrafiltration membrane, a microfiltration membrane, a reverse osmosis membrane, or the like that generally filters fine particle-containing liquids can be appropriately used. FIG. 1B shows a more specific example of the flow described in FIG. 1A.

  The composite after solid-liquid separation is preferably dried by heating, for example, if necessary.

(Supplying process of additional hydroxy group-containing compound)
For example, as shown in FIG. 2A, the composite obtained in this manner can further hold an additional hydroxy group-containing compound as necessary. By holding the additional hydroxy group-containing compound in the composite, a pyrochlore phase can be generated more effectively while suppressing grain growth. FIG. 2B shows a more specific example of the flow described in FIG. 2A.

  The form in which the additional hydroxy group-containing compound is held in the complex is not particularly limited. Spraying the solution of the hydroxy group-containing compound toward the composite, or immersing the composite in the solution, supplying the solution to the composite, impregnating, and then at least partially distilling off the liquid content. Preferably, most of the compound can be distilled off to concentrate the additional hydroxy group-containing compound and retained in the complex.

  The additional hydroxy group-containing compound is preferably dissolved in a lower alcohol such as methanol or ethanol depending on the type and considering the ease of subsequent distillation of the liquid. The concentration of the additional hydroxy group-containing compound is preferably such that the molar ratio is 5 to 30 times the cerium or zirconium of the composite. More preferably, it is 10 times or more and 25 times or less. This is because the hydroxy group-containing compound is additionally retained, so that a higher concentration is more effective.

  When the hydroxy group-containing compound solution is brought into contact with the complex, the complex is supplied to a sufficient amount of the hydroxy group-containing compound solution and mixed well. Preferably, the composite is dispersed in the solution by sonication or the like.

  Thereafter, the complex is separated from the hydroxy group-containing compound solution using an appropriate solid-liquid separation means. In order to keep the additional hydroxy group-containing compound well in the composite, the medium of the hydroxy group-containing compound solution is then distilled off. During the distillation, heating is performed as necessary. Depending on the type of medium, for example, in the case of an ethanol solution, it is preferable to dry by heating at 200 ° C. for about 12 hours.

  The additional hydroxy group-containing compound may be the same as or different from the hydroxy group-containing compound used in the hydrothermal process. As such a hydroxy group-containing compound, typically, glycolic acid can be used.

(First firing step)
The first firing step is a step of obtaining a first fired body including a ceria-zirconia composite oxide phase and a carbide phase by firing the composite body in a reducing atmosphere. According to the first firing step, the composite has the first ceria-zirconia composite oxide phase of pyrochlore phase in which grain growth is suppressed by the carbide phase while the carbide phase is formed by firing in a reducing atmosphere. Can be obtained.

  The reducing atmosphere used in the first baking step is not particularly limited, but a known inert gas such as nitrogen or argon, or hydrogen is used, and the temperature is 1200 ° C to 1500 ° C, preferably 1200 ° C to 1300 ° C. In the range, heating is performed for about several hours, for example, for about 1 hour to 6 hours. Prior to such a heating step, a carbide phase is generated in advance by heating in a reducing atmosphere at a temperature of about 300 ° C. to 500 ° C. for about 10 hours to 30 hours, preferably about 15 hours to 30 hours. Then, by promoting the generation of the pyrochlore phase, it is possible to suppress the grain growth and generate the pyrochlore phase.

(Second firing step)
The second firing step is a step of obtaining the second fired body by further firing the first fired body in an oxidizing atmosphere. According to the second firing step, the ceria-zirconia oxide phase is made into an independent phase, that is, a particulate form by burning off the carbide phase in the first fired body by firing in an oxidizing atmosphere. A κ phase can be generated from the pyrochlore phase. The heating conditions of the second firing step are not particularly limited, and may be set to a temperature and time at which carbides can be removed from the first fired body. Typically, in the second baking step, heating is performed at 300 ° C. or higher and 600 ° C. or lower in an oxidizing atmosphere such as air. Preferably they are 350 degreeC or more and 500 degrees C or less. Although the heating time is not particularly limited, it can be about several hours to about 10 hours.

The ceria-zirconia composite oxide material thus obtained can have the following characteristics.
(1) The ceria-zirconia composite oxide particles constituting the composite oxide material are particles mainly composed of a ceria-zirconia composite oxide in a pyrochlore phase (κ phase in the reduced state). That is, it is preferable to have the pyrochlore phase as the most dominant component. Therefore, it is preferable that the particles have a pyrochlore phase exceeding 50 mol% of the whole. More preferably, it is 60 mol% or more, More preferably, it is 70 mol% or more, More preferably, it is 80 mol% or more, More preferably, it is 90 mol% or more, More preferably, it is 95 mol% or more Most preferably, it consists essentially of a pyrochlore phase. The pyrochlore phase can be confirmed by combining EDX or X-ray diffraction spectrum.
(2) It has a pyrochlore phase (κ phase in the reduced state). Specifically, it means that the 2θ angle of the X-ray diffraction pattern using CuKα has diffraction angle peaks at positions of 14 °, 28 °, 37 °, 44.5 ° and 51 °. Yes.
(3) Moreover, this complex oxide material substantially consists of a ceria-zirconia complex oxide. That is, in addition to the ceria-zirconia composite oxide, it means that only inevitable impurities are included. The amount of inevitable impurities is not particularly limited, but is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less.
(4) The average particle size is 1 μm or less, more preferably 100 μm or less, and further preferably 50 nm or less.
However, the average particle size was measured by TEM observation and evaluated in a field of view of 80 nm × 120 nm. The number of particles to be measured in one field of view is 15 and the average value is obtained. Preferably, it is preferable to obtain an average value for 30 fields of view and further average the average value.

  According to the composite oxide material disclosed in this specification, a submicron-sized ceria-zirconia composite oxide material in which grain growth is suppressed can be obtained. For this reason, the catalyst material which OSC ability improved more can be provided. The ceria-zirconia composite oxide material disclosed in the present specification can be used as an oxygen storage material of an exhaust gas purification catalyst for an internal combustion engine such as a vehicle due to the characteristics of the ceria and the effect of addition of zirconia. That is, it can be used together with a noble metal or at least a part of a support material containing such a noble metal catalyst. Therefore, the ceria-zirconia composite oxide material of the present invention can be used as, for example, a composite material for exhaust gas purification of an internal combustion engine. The metal catalyst for exhaust gas purification and the supporting material are well known to those skilled in the art, and can be appropriately selected from known materials.

  According to the present invention, an exhaust gas purification apparatus for an internal combustion engine is also provided. That is, an exhaust gas purification apparatus including a catalyst phase containing the ceria-zirconia composite oxide material of the present invention is also provided. The form of the exhaust gas purification device is not particularly limited, and various known forms can be adopted, but typically a honeycomb structure. The catalyst phase containing the ceria-zirconia composite oxide material of the present invention may be contained in a matrix constituting the honeycomb structure, or may be imparted to the surface of the inner wall or the like. Such a method for manufacturing an exhaust gas purification device is well known to those skilled in the art, and those skilled in the art can easily use the ceria-zirconia composite oxide material of the present invention as an oxygen storage material or a catalyst support material to make the exhaust gas purification device easy. Can be manufactured.

  Hereinafter, the present invention will be described with specific examples. In addition, this invention is not limited to a following example.

(Hydrothermal reaction process)
Ce (NO ₃ ) ₃ · 6H ₂ O and ZrOCl ₂ · 8H ₂ O were dissolved in water to prepare aqueous solutions of 0.1 mol / l each. In contrast, glycolic acid was added to 0.2 mol / l, and ammonia water was added to 0.5 mol / l to obtain a raw material solution for hydrothermal reaction having a pH of 10. . This liquid was heated in a pressure vessel at 100 ° C. for 12 hours to carry out a hydrothermal reaction, and a complex of cerium hydroxide, zirconium hydroxide and glycolic acid was obtained as an insoluble matter.

(Retaining process of additional hydroxy group-containing compound)
The composite was recovered by solid-liquid separation with an ultrafiltration filter (pore size: 0.1 μm), and prepared to contain 20 times the amount of glycolic acid in a molar ratio with respect to cerium in the recovered composite. The whole amount of the recovered complex was put into an acid ethanol solution and sonicated to be well dispersed. The dispersion was again passed through an ultrafiltration membrane to recover the complex and dried at 200 ° C. for 12 hours. By this drying, a complex in which glycolic acid was additionally retained was obtained.

(First firing step)
The composite obtained in the holding step of the additional hydroxy group-containing compound was initially heated at 300 ° C. to 500 ° C. for 24 hours under a nitrogen atmosphere, then heated to 1200 ° C. and heated at 1200 ° C. for 1 hour. . By such a process, since the formation of the ceria-zirconia composite oxide phase is promoted after promoting the formation of the carbide phase, the grain growth of the ceria-zirconia composite oxide phase can be effectively suppressed. The obtained fired body (first fired body) had a pyrochlore phase ceria-zirconia composite oxide phase and a carbide phase. FIG. 3 shows an X-ray diffraction spectrum of the first fired body. As shown in FIG. 3, a peak derived from a superlattice structure around 2θ = 14 ° characteristic of the pyrochlore phase was observed.

(Second firing step)
The first fired body was then heated in air at 400 ° C. for 12 hours. Through these steps, the carbide phase was burned out and the pyrochlore phase was changed to the κ phase. FIG. 3 shows an X-ray diffraction spectrum of the second fired body. In the obtained fired body (second fired body), a peak derived from a superlattice structure around 2θ = 14 ° characteristic of the κ phase was observed. Further, as shown in the lower diagram of FIG. 3, the crystallite diameter of the first fired body is 11.7 nm, and the crystallite diameter of the second fired body is 13.3 nm. It was found that the grain growth was effectively suppressed, and the average particle size of the second fired body was nano level.

  From the above, it was found that the ceria-zirconia composite oxide material of the present invention is a ceria-zirconia composite oxide mainly composed of a pyrochlore phase in the reduced state and mainly composed of κ phase in the oxidized state. Moreover, since the crystallite diameter was also sufficiently suppressed, it was found that the particle diameter of the ceria-zirconia composite oxide particles itself was also suppressed, and an improvement in the OSC function was expected.

(Evaluation of second fired body)
In this example, the oxygen release ability of the second fired body was evaluated. Specifically, using a fixed-bed flow reactor equipped with a quadrupole mass spectrometer with a mass filter (REGA-102, ULVAC), the catalyst of the catalyst by hydrogen-temperature programmed reduction (H ₂ -TPR) is used. Reduction characteristics were evaluated. A quartz reaction tube having a diameter of 10 mm was filled with 0.2 g of the catalyst (second calcined body), set in an image furnace attached to the apparatus, and a predetermined gas was circulated. The test procedure was as follows.

(1) Apply O ₂ -10% (Ar blank) at 500 ° C. for 10 minutes as pretreatment (2) Decrease the temperature to room temperature while circulating Ar (3) H ₂ -1% (Ar blank) 30 as the main test The hydrogen mass spectrum is measured at ˜800 ° C. (temperature increase rate 20 ° C./min).

In this method, hydrogen reacts with oxygen released from the oxide and turns into water. Therefore, assuming that the mass intensity of hydrogen is proportional to the hydrogen flow rate, the reduced amount of hydrogen flow is regarded as the oxygen release rate. Can do. The theoretical hydrogen consumption of κ-CZ (ceria-zirconia composite oxide) is 0.2 g / 590 = 3.4 × 10 ⁻ from Ce ₂ Zr ₂ O ₈ + H ₂ → Ce ₂ Zr ₂ O ₇ + H ₂ O. ⁴ mol. The obtained results are shown in FIG.

  When the hydrogen consumption was calculated from FIG. 4, the hydrogen consumption in the second calcined body reached 61% of the theoretical hydrogen consumption, whereas it was 25% in normal CZ. Thus, it turned out that the 2nd calcination object shows oxygen releasing ability more than double of usual CZ. It was also found that oxygen release starts from the low temperature side.

  It has been found that the ceria-zirconia composite oxide material disclosed in this specification can exhibit excellent OSC. Moreover, according to the manufacturing method of this invention, since the ceria-zirconia composite oxide material atomized by the hydrothermal treatment can be obtained, it turned out that the excellent ceria-zirconia composite oxide material can be provided efficiently. .

Claims (5)

A method for producing a ceria-zirconia composite oxide material,
Ceria-zirconia composite oxidation by water, cerium ion, zirconium ion, and hydroxy group-containing compound containing at least two hydroxy groups, heating the alkaline raw material liquid and carrying out hydrothermal reaction Obtaining a complex of the product and the hydroxy group-containing compound;
Firing the composite in a reducing atmosphere to obtain a first fired body containing a ceria-zirconia composite oxide phase that is a pyrochlore phase and a carbide phase;
A second fired body mainly composed of a ceria-zirconia composite oxide phase which is a κ phase by firing the first fired body in an oxidizing atmosphere to remove a carbide phase in the first fired body. A process of acquiring;
A manufacturing method comprising:   The manufacturing method according to claim 1, further comprising a step of holding an additional hydroxy group-containing compound in the composite after the composite acquisition step and prior to the first fired body acquisition step. Step of holding the additional hydroxy group-containing compound, the solution of the additional hydroxy group-containing compound to a complex supply, in the step of removing at least a portion of the liquid fraction of the solution from the complex The manufacturing method of Claim 2 which exists.   The said hydrothermal reaction is a manufacturing method in any one of Claims 1-3 performed at 50 to 200 degreeC.   The manufacturing method according to claim 1, wherein the hydroxy group-containing compound is glycolic acid.