Zirconia-containing alumina-based composite oxide and method for producing zirconia-containing alumina-based composite oxide

Abstract

Provided is a zirconia-containing alumina-based composite oxide which contains zirconia and alumina and which, in an XRD pattern A after heating at 1200 DEG C for 12 hours under atmospheric pressure, satisfies the following formula [1]: 0.25 lt, where X is the peak intensity derived from a theta-Al2O3 phase near 2 [theta] = 33 DEG, Y is the peak intensity derived from an alpha-Al2O3 phase near 2 [theta] = 26 DEG, and R is [X / Y]; rlt; 5.0.

Description

Technical Field

[0001] The present invention relates to an alumina-based composite oxide containing zirconium oxide and a method for preparing the alumina-based composite oxide containing zirconium oxide. Background Art

[0002] As reflected in recent emission control models, exhaust gas temperatures rise significantly during high and ultra-high speed driving. Consequently, the operating temperature of exhaust gas purification catalysts has also increased significantly compared to previous generations, making it difficult to suppress the melting of precious metals such as Rh.

[0003] Conventionally, it is known that a composite oxide containing zirconium oxide and aluminum oxide can be used as a catalyst support (for example, see Patent Documents 1 to 5).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-184125

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2014-552

[0008] Patent Document 3: Japanese Patent Application Laid-Open No. 2016-209858

[0009] Patent Document 4: Japanese Patent Application Laid-Open No. 2017-132663

[0010] Patent Document 5: Japanese Patent Application No. 2020-514217 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] When conventional composite oxides containing zirconium oxide and aluminum oxide are exposed to high temperatures, their specific surface area generally decreases. This decrease in specific surface area also reduces catalytic performance. Therefore, there is a need for a zirconium oxide-containing alumina composite oxide that maintains a high specific surface area commensurate with the aluminum oxide content, even when exposed to high temperatures.

[0013] The present invention has been made in view of the above-mentioned problems, and its object is to provide a zirconium-containing alumina-based composite oxide having a high specific surface area commensurate with the alumina content even when exposed to high temperatures. It is also an object to provide a method for producing the zirconium-containing alumina-based composite oxide, which can produce the zirconium-containing alumina-based composite oxide.

[0014] Solutions for solving problems

[0015] When existing composite oxides containing Al2O3 are exposed to high temperatures, α-Al2O3 undergoes significant crystallization, resulting in a decrease in specific surface area. The inventors discovered that by suppressing the crystallization of α-Al2O3, they can maintain a high specific surface area commensurate with the alumina content even under high temperature exposure, leading to the completion of the present invention.

[0016] That is, the present invention provides the following solutions:

[0017] (1) A zirconium oxide-containing alumina composite oxide characterized by comprising zirconium oxide and alumina,

[0018] In the XRD pattern A after heating at 1200°C for 12 hours under atmospheric pressure, when the peak intensity of the θ-Al2O3 phase at about 2θ = 33° is defined as X, the peak intensity of the α-Al2O3 phase at about 2θ = 26° is defined as Y, and [X / Y] is defined as R, R satisfies the following formula [1]:

[0019] Formula [1] 0.25 <R<5.0。

[0020] According to the above configuration, R is greater than 0.25. That is, after heating at 1200°C for 12 hours, the content of θ-Al2O3 relative to α-Al2O3 is higher. In the present invention, within the alumina contained in the zirconium oxide-containing alumina-based composite oxide, the content of α-Al2O3, which significantly crystallizes when exposed to high temperatures, is reduced, while the content of θ-Al2O3, which is less susceptible to crystallization at high temperatures than α-Al2O3, is increased. Consequently, even when exposed to high temperatures, the composite oxide maintains a high specific surface area commensurate with the alumina content.

[0021] (2) According to the zirconium oxide-containing alumina composite oxide described in (1), when the peak intensity of ZrO2 in the XRD pattern A originating from the vicinity of 2θ=30° is defined as Z, the mass ratio of the ZrO2 oxide component to the entire zirconium oxide-containing alumina composite oxide is defined as W, and [Z / W] is defined as Tr, Tr satisfies the following formula [2]:

[0022] Formula [2] 1.70 <Tr<25.0。

[0023] As described above, Tr is a value obtained by dividing the peak intensity (Z) derived from ZrO 2 by the mass ratio (W) of the oxide component of ZrO 2 , and this value indicates the degree of crystal growth of ZrO 2 .

[0024] The inventors discovered that when Tr reaches a certain value or above, ZrO2 becomes a diffusion barrier to Al2O3. In other words, the inventors discovered that Tr, which indicates the degree of ZrO2 crystal growth, can be used as a value indicating the contribution of ZrO2 as a diffusion barrier to Al2O3.

[0025] In the present invention, the required ZrO2 crystallite size varies depending on the ZrO2 content in the oxide, so Tr is defined as a value divided by the mass ratio of ZrO2.

[0026] When Tr is greater than 1.70, the degree of ZrO2 crystal growth is somewhat enhanced. When exposed to high temperatures, ZrO2 acts as a diffusion barrier for Al2O3, thereby inhibiting the aggregation (crystallization) of Al2O3. This allows for a higher specific surface area corresponding to the alumina content even when exposed to high temperatures.

[0027] (3) In the zirconium oxide-containing alumina composite oxide according to (1) or (2), R satisfies the following formula [3]:

[0028] Formula [3] 0.35 <R<3.5。

[0029] When R is greater than 0.35, a decrease in specific surface area due to exposure to high temperature can be further suppressed.

[0030] (4) According to any one of (1) to (3) above, the zirconium oxide-containing alumina composite oxide, wherein Tr satisfies the following formula [4]:

[0031] Formula [4] 1.72 <Tr<20.0。

[0032] If the Tr is greater than 1.72, a decrease in specific surface area due to exposure to high temperature can be further suppressed.

[0033] (5) The zirconium oxide-containing alumina composite oxide according to any one of (1) to (4), wherein the content of alumina is 15% by mass or more and 97% by mass or less.

[0034] When the aluminum oxide content is 15% by mass or more, the reduction in specific surface area caused by exposure to high temperatures can be further suppressed. Furthermore, when the aluminum oxide content is 97% by mass or less, element segregation is reduced, thereby suppressing the crystallization of aluminum oxide caused by exposure to high temperatures.

[0035] (6) The zirconium oxide-containing alumina composite oxide according to any one of (1) to (5), wherein the zirconium oxide content is 0.1% by mass or more and 75% by mass or less.

[0036] When the zirconium oxide content is 0.1% by mass or greater, the stabilizing effect of element diffusion into the alumina further suppresses the reduction in specific surface area caused by exposure to high temperatures. Furthermore, when the zirconium oxide content is 75% by mass or less, element segregation is reduced, thereby suppressing crystallization of zirconium oxide caused by exposure to high temperatures.

[0037] (7) The zirconium oxide-containing alumina-based composite oxide according to any one of (1) to (6), further comprising an oxide of a rare earth element other than Pm.

[0038] When an oxide of a rare earth element other than Pm is contained, a decrease in specific surface area due to exposure to high temperatures can be further suppressed.

[0039] Furthermore, the method for producing a zirconium oxide-containing alumina-based composite oxide of the present invention is characterized by comprising:

[0040] Step 1, adding a basic zirconium salt to an aqueous solution of a soluble carbonate and / or a soluble bicarbonate to obtain a solution A;

[0041] Step 2, obtaining a solution B, wherein the solution B contains an aluminum-containing raw material salt and a zirconium-containing raw material salt;

[0042] Step 3, mixing the solution A and the solution B to obtain a precipitate of a zirconium-containing aluminum composite hydroxide; and

[0043] Step 4, heat-treating the precipitate to obtain an alumina-based composite oxide containing zirconium oxide,

[0044] in,

[0045] The amount of the basic zirconium salt added in step 1 is such that zirconium oxide accounts for 1 to 95% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0046] The amount of the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 5 to 99% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0047] The total amount of zirconium oxide contained in the basic zirconium salt added in step 1 and the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 100% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0048] Generally speaking, when alumina is exposed to high temperature, a crystal phase transition of Boehmite → γ-Al2O3 → δ-Al2O3 → θ-Al2O3 → α-Al2O3 occurs, with the α phase being the most stable.

[0049] In the preparation of alumina composite oxides, generally speaking, metal salts including aluminum salts are precipitated as a precursor containing boehmite by an alkali neutralization method. However, in this method, a γ phase is formed during the firing process, and the crystalline phase eventually transitions to an α phase. In addition, if metal salts of multiple elements are used when obtaining alumina composite oxides by an alkali neutralization method, the element distribution in the obtained precipitate will segregate due to the different pH values ​​for generating hydroxide crystals, making it difficult to obtain a composite oxide with a uniform element distribution in the final composite oxide. When the element distribution is uneven and there are deviations, high-temperature heating will promote the crystallization of certain elements starting from the segregated portion of the element distribution.

[0050] On the other hand, in the present invention, by using Solution A (alkaline zirconium solution) as a neutralizing agent to precipitate aluminum salt, fine ZrO2 can be highly dispersed in the precursor. Since the crystallization of certain elements is suppressed during high-temperature heating, the θ phase can be maintained even after high-temperature heating.

[0051] The amount of the basic zirconium salt added in step 1 is such that zirconium oxide accounts for 1 to 95% by mass of the obtained zirconium oxide-containing alumina composite oxide. In step 2, the remaining zirconium oxide is added to control R to an appropriate value.

[0052] In summary, the zirconium oxide-containing alumina-based composite oxide obtained according to the present preparation method suppresses the crystallization of the α phase under high-temperature heating conditions and suppresses the reduction in specific surface area.

[0053] Effects of the Invention

[0054] According to the present invention, a zirconium oxide-containing alumina composite oxide having a high specific surface area corresponding to the alumina content even when exposed to high temperatures can be provided. Furthermore, a method for producing a zirconium oxide-containing alumina composite oxide can be provided, which can produce the zirconium oxide-containing alumina composite oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 1 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 1.

[0056] Figure 2 1 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 2.

[0057] Figure 3 1 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina composite oxide after heating in Comparative Example 1.

[0058] Figure 41 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 3.

[0059] Figure 5 1 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina composite oxide after heating in Comparative Example 2.

[0060] Figure 6 1 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 4.

[0061] Figure 7 3 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina composite oxide after heating in Comparative Example 3.

[0062] Figure 8 1 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 7.

[0063] Figure 9 1 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Comparative Example 4.

[0064] Figure 10 13 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 13.

[0065] Figure 11 : This is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Comparative Example 5.

[0066] Figure 12 This is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 22.

[0067] Figure 13 1 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Comparative Example 6.

[0068] Figure 14 This is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 31.

[0069] Figure 15 This is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 32.

[0070] Figure 16 This is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Example 33.

[0071] Figure 17 1 is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Comparative Example 7.

[0072] Figure 18 : This is the X-ray diffraction spectrum of the zirconium oxide-containing alumina-based composite oxide after heating in Comparative Example 8. DETAILED DESCRIPTION

[0073] The following describes embodiments of the present invention. However, the present invention is not limited to these embodiments. It should be noted that, in this specification, the zirconium oxide-containing alumina-based composite oxide refers to a conventional zirconium oxide-containing alumina-based composite oxide that contains 10% by mass or less of a hafnium-containing impurity metal compound. Furthermore, in this specification, expressions such as "containing" and "comprising" encompass the concepts of "containing," "including," "consisting essentially of," and "consisting only of."

[0074] The maximum and minimum values ​​of the content of each component shown below are independent of the contents of other components and are respectively the preferred minimum and preferred maximum values ​​of the present invention.

[0075] Furthermore, the maximum and minimum values ​​of various parameters (measured values, etc.) shown below are independent of the content (composition) of each component and are respectively the preferred minimum and maximum values ​​of the present invention.

[0076] [Zirconium oxide-containing alumina-based composite oxide]

[0077] The zirconium oxide-containing alumina-based composite oxide of this embodiment is characterized in that:

[0078] Contains zirconium oxide and aluminum oxide,

[0079] In the XRD pattern A after heating at 1200°C for 12 hours under atmospheric pressure, when the peak intensity of the θ-Al2O3 phase at about 2θ = 33° is defined as X, the peak intensity of the α-Al2O3 phase at about 2θ = 26° is defined as Y, and [X / Y] is defined as R, R satisfies the following formula [1]:

[0080] Formula [1] 0.25 <R<5.0。

[0081] The R of the zirconia-containing alumina-based composite oxide is greater than 0.25. That is, after heating at 1200°C for 12 hours, the content of θ-Al2O3 is higher than that of α-Al2O3. In this embodiment, the content of α-Al2O3, which significantly crystallizes when exposed to high temperatures, in the alumina contained in the zirconia-containing alumina-based composite oxide is reduced, while the content of θ-Al2O3, which is less susceptible to crystallization at high temperatures than α-Al2O3, is increased. Therefore, even when exposed to high temperatures, the composite oxide has a high specific surface area commensurate with the alumina content.

[0082] The R can be controlled, for example, according to the preparation method. Specifically, it can be controlled according to the following preparation method described below.

[0083] The preparation method of the alumina-based composite oxide containing zirconium oxide comprises:

[0084] Step 1, adding a basic zirconium salt to an aqueous solution of a soluble carbonate and / or a soluble bicarbonate to obtain a solution A;

[0085] Step 2, obtaining a solution B, wherein the solution B contains an aluminum-containing raw material salt and a zirconium-containing raw material salt;

[0086] Step 3, mixing the solution A and the solution B to obtain a precipitate of a zirconium-containing aluminum composite hydroxide; and

[0087] Step 4, heat-treating the precipitate to obtain an alumina-based composite oxide containing zirconium oxide,

[0088] in,

[0089] The amount of the basic zirconium salt added in step 1 is such that zirconium oxide accounts for 1 to 95% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0090] The amount of the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 5 to 99% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0091] The total amount of zirconium oxide contained in the basic zirconium salt added in step 1 and the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 100% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0092] By using Solution A (alkaline zirconium solution) as a neutralizing agent to precipitate aluminum salt, fine ZrO2 can be highly dispersed in the precursor. Since the crystallization of certain elements is suppressed during high-temperature heating, the θ phase can be maintained even after high-temperature heating. This allows the R value to be greater than 0.25.

[0093] A more detailed method of controlling R is to control the ratio of the basic zirconium solution used as a raw material within the above numerical range. Specifically, the greater the amount of basic zirconium salt added in step 1, the greater the value of R tends to be.

[0094] This can be seen, for example, from the comparison between Example 1 and Example 2, and the comparison between Example 5 and Example 6.

[0095] However, as the amount of the basic zirconium salt added in step 1 increases, the amount of the zirconium-containing raw material salt added in step 2 decreases. Furthermore, as the amount of the zirconium-containing raw material salt added in step 2 decreases, the amount of ZrO2 that acts as a diffusion barrier for Al2O3 decreases. This is because the ZrO2 derived from the basic zirconium salt added in step 1 is very fine and therefore less likely to act as a diffusion barrier for Al2O3.

[0096] Therefore, the more the amount of alkaline zirconium salt added in the process 1, the larger the value of R tends to be. However, when the amount of alkaline zirconium salt added in the process 1 exceeds a certain amount, the value of R first reaches a maximum and then gradually decreases.

[0097] This can be seen, for example, from the comparison of Examples 31 to 33, Comparative Example 7, and Comparative Example 8.

[0098] In Examples 31 to 33, Comparative Example 7, and Comparative Example 8, it can be seen that, first, in the order of Comparative Example 7 and Example 32, as the amount of the basic zirconium salt added in step 1 increases, R also increases in that order (0.20 in Comparative Example 7 and 0.40 in Example 31). Furthermore, as the amount of the basic zirconium salt added in step 1 increases, the value of R reaches a maximum near the region between Examples 31 and 32. Furthermore, it can be seen that as the amount of the basic zirconium salt added in step 1 increases, R decreases in the order of Example 32, Example 33, and Comparative Example 8 (0.29 in Example 32, 0.25 in Example 33, and 0.23 in Comparative Example 8).

[0099] As described above, R can be controlled, for example, by controlling the ratio of the alkaline zirconium solution used as a raw material within the aforementioned numerical range.

[0100] The R is preferably 0.3 or greater, more preferably 0.35 or greater, and even more preferably 0.4 or greater. The R is preferably 4.0 or less, more preferably 3.0 or less, and even more preferably 2.5 or less.

[0101] The R is preferably greater than 0.25 and less than or equal to 2.41, more preferably 0.26 to 2.4, further preferably 0.26 to 2.3, particularly preferably 0.28 to 2.29, and particularly preferably 0.29 to 2.2 and 0.30 to 1.8.

[0102] In the alumina-based composite oxide containing zirconium oxide, when the peak intensity of ZrO2 in the XRD pattern A originating from the vicinity of 2θ=30° is defined as Z, the mass ratio of the oxide component of ZrO2 to the entire alumina-based composite oxide containing zirconium oxide is defined as W (mass %), and [Z / W] is defined as Tr, Tr preferably satisfies the following formula [2]:

[0103] Formula [2] 1.70 <Tr<25.0。

[0104] As described above, Tr is a value obtained by dividing the peak intensity (Z) derived from ZrO 2 by the mass ratio (W) of the oxide component of ZrO 2 , and this value indicates the degree of crystal growth of ZrO 2 .

[0105] The inventors discovered that when Tr reaches a certain value or more, ZrO2 becomes a diffusion barrier to Al2O3. In other words, the inventors discovered that Tr, which indicates the degree of ZrO2 crystal growth, can be a value indicating the contribution of ZrO2 as a diffusion barrier to Al2O3.

[0106] In this embodiment, since the required ZrO 2 crystallite size varies depending on the ZrO 2 content in the oxide, Tr is defined as a value divided by the mass ratio of ZrO 2 .

[0107] When Tr is greater than 1.70, the degree of ZrO2 crystal growth is somewhat enhanced. When exposed to high temperatures, ZrO2 acts as a diffusion barrier for Al2O3, thereby inhibiting the aggregation (crystallization) of Al2O3. This allows for a higher specific surface area corresponding to the alumina content even when exposed to high temperatures.

[0108] The Tr is preferably greater than 1.72, more preferably greater than 1.75, further preferably greater than 1.80, particularly preferably greater than 1.85, and particularly preferably greater than 1.90. Furthermore, the larger the Tr, the better, for example, 22.0 or less, 20.0 or less, etc.

[0109] The Tr is preferably 1.75 to 18.1, more preferably 1.78 to 18.04, further preferably 1.80 to 18.0, particularly preferably 1.85 to 17.9, particularly preferably 1.87 to 17.39, and particularly preferably 1.92 to 16.34.

[0110] The Tr can be controlled, for example, according to the preparation method. Specifically, since the ZrO2 derived from the alkaline zirconium salt added in the process 1 is very fine, it is difficult to express it as the peak intensity of ZrO2 derived from the vicinity of 2θ=30°. On the other hand, since the ZrO2 derived from the zirconium-containing raw material salt added in the process 2 is very fine, it is easy to express it as the peak intensity of ZrO2 derived from the vicinity of 2θ=30°. Therefore, when the proportion of the alkaline zirconium salt added in the process 1 increases (when the proportion of the zirconium-containing raw material salt added in the process 2 decreases), Tr tends to decrease, and when the proportion of the alkaline zirconium salt added in the process 1 decreases (when the proportion of the zirconium-containing raw material salt added in the process 2 increases), Tr tends to increase.

[0111] The specific surface area of ​​the alumina-based composite oxide containing zirconium oxide after heating at 1200° C. for 12 hours under atmospheric pressure varies depending on the content of alumina, and is preferably 0.1 m 2 / g above 50m 2 / g or less. The specific surface area after heating is more preferably 0.2m 2 / g or more, more preferably 0.3m 2 / g or more. The specific surface area after heating is more preferably 45m 2 / g or less, more preferably 40m 2 / g or less.

[0112] The specific surface area of ​​the alumina-based composite oxide containing zirconium oxide before heating is preferably 10 m 2 / g above 300m 2 / g or less. The specific surface area before heating is more preferably 12m 2 / g or more, more preferably 15m 2 / g or more, particularly preferably 20m 2 / g or more, particularly preferably 25m 2 / g or more, particularly preferably 30m 2 There is no particularly preferred upper limit for the specific surface area before heating, and it can be 280 m 2 / g or less, 270m 2 / g or less, 260m 2 / g or less, 250m 2 / g or less, 240m 2 / g or less.

[0113] <Particle size D 50 >

[0114] The particle size D of the alumina composite oxide containing zirconium oxide is 50 It is preferably 2.0 μm or more and 250 μm or less. 50More preferably, it is 3.0 μm or more, and even more preferably, it is 4.0 μm or more. 50 More preferably, it is 280 μm or less, and even more preferably, it is 250 μm or less. 50 is a value obtained according to the method described in the embodiment.

[0115] The zirconium oxide-containing alumina-based composite oxide contains alumina. The alumina content is preferably 15% by mass or greater and 97% by mass or less. When the alumina content is 15% by mass or greater, a decrease in specific surface area due to exposure to high temperatures can be further suppressed. Furthermore, when the alumina content is 97% by mass or less, crystallization of the alumina due to exposure to high temperatures can be suppressed due to reduced elemental segregation.

[0116] The aluminum oxide content is more preferably 17% by mass or more, and even more preferably 19% by mass or more. Furthermore, the aluminum oxide content is more preferably 96% by mass or less, and even more preferably 95% by mass or less.

[0117] The zirconium oxide-containing alumina composite oxide contains zirconium oxide. The zirconium oxide content is preferably 0.1% by mass or more and 75% by mass or less. When the zirconium oxide content is 0.1% by mass or more, the stabilizing effect of element diffusion into the alumina further suppresses the reduction in specific surface area caused by exposure to high temperatures. Furthermore, when the zirconium oxide content is 75% by mass or less, element segregation is reduced, thereby suppressing crystallization of the zirconium oxide caused by exposure to high temperatures.

[0118] The content of zirconium oxide is more preferably 1% by mass or more, and even more preferably 2% by mass or more, and is more preferably 73% by mass or less, and even more preferably 70% by mass or less.

[0119] In the zirconium oxide-containing alumina-based composite oxide, the total content of zirconium oxide and alumina is preferably 15% by mass or more and 99% by mass or less, when the total content of the zirconium oxide-containing alumina-based composite oxide is 100% by mass. By setting the total content of zirconium oxide and alumina to 15% by mass or more and 99% by mass or less, a decrease in specific surface area due to exposure to high temperatures can be further suppressed.

[0120] When the total content of the zirconium oxide-containing alumina composite oxide is 100% by mass, the total content of zirconium oxide and alumina is more preferably 16% by mass or more, and even more preferably 17% by mass or more. When the total content of the zirconium oxide-containing alumina composite oxide is 100% by mass, the total content of zirconium oxide and alumina is more preferably 98% by mass or less, and even more preferably 97% by mass or less.

[0121] The zirconium oxide-containing alumina-based composite oxide preferably contains an oxide of a rare earth element other than Pm. When the oxide of a rare earth element other than Pm is contained, a decrease in specific surface area due to exposure to high temperatures can be further suppressed.

[0122] Among oxides of rare earth elements other than Pm, the zirconium oxide-containing alumina-based composite oxide preferably contains oxides of Ce, La, Nd, Pr, and Y. When the zirconium oxide-containing alumina-based composite oxide contains oxides of Ce, La, Nd, Pr, and Y, a decrease in specific surface area due to exposure to high temperatures can be particularly suppressed.

[0123] When containing oxides of rare earth elements other than Pm, the content of the oxides of rare earth elements other than Pm is preferably 1% by mass or more and 70% by mass or less, relative to 100% by mass of the total zirconium oxide-containing alumina-based composite oxide. When the content of the oxides of rare earth elements other than Pm is 1% by mass or more, a decrease in specific surface area due to exposure to high temperatures can be effectively suppressed. Furthermore, when the content of the oxides of rare earth elements other than Pm is 70% by mass or less, elemental segregation is reduced, thereby suppressing crystallization of alumina and zirconia due to exposure to high temperatures.

[0124] When the total amount of the zirconium oxide-containing alumina composite oxide is taken as 100% by mass, the content of the oxide of the rare earth element other than Pm is more preferably 1.5% by mass or more, and even more preferably 2% by mass or more. When the total amount of the zirconium oxide-containing alumina composite oxide is taken as 100% by mass, the content of the oxide of the rare earth element other than Pm is more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less.

[0125] The zirconium oxide-containing alumina-based composite oxide may include one or more selected from the group consisting of (A) an oxide of at least one element selected from the group consisting of In, Si, Sn, Bi, P, and Zn; (B) a transition metal oxide (excluding oxides of rare earth elements and oxides of precious metal elements); and (C) an alkaline earth metal oxide. These components (A) to (C) are hereinafter referred to as "other oxides."

[0126] The transition metal oxide may be one or more oxides selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Ta, and W. In addition, the alkaline earth metal oxide may be one or more oxides selected from the group consisting of Mg, Ca, Sr, and Ba.

[0127] When the zirconia-containing alumina-based composite oxide includes the other oxides, the content of the other oxides is preferably 0.1% by mass or more and 30% by mass or less, based on 100% by mass of the entire zirconia-containing alumina-based composite oxide. The content of the other oxides is more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, based on 100% by mass of the entire zirconia-containing alumina-based composite oxide. The content of the other oxides is more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on 100% by mass of the entire zirconia-containing alumina-based composite oxide.

[0128] The preferred composition ratio of the zirconium oxide-containing alumina composite oxide may be the following combinations, the total of which does not exceed 100% by mass:

[0129] (1) Preferably,

[0130] Alumina: more than 15% and less than 97%;

[0131] Zirconia: more than 0.1% and less than 75%;

[0132] Oxides of rare earth elements: more than 1% and less than 70%;

[0133] Other oxides: more than 0% and less than 30%;

[0134] (2) More preferably,

[0135] Alumina: more than 17% and less than 96%;

[0136] Zirconia: more than 1% and less than 73%;

[0137] Oxides of rare earth elements: more than 1.5% and less than 65%;

[0138] Other oxides: more than 0% and less than 25%;

[0139] (3) Further preferably,

[0140] Alumina: more than 19% and less than 96%;

[0141] Zirconia: more than 2% and less than 70%;

[0142] Oxides of rare earth elements: more than 2% and less than 60%;

[0143] Other oxides: more than 0% and less than 20%;

[0144] (4) Particularly preferably,

[0145] Alumina: more than 20% and less than 96%;

[0146] Zirconia: more than 3% and less than 70%;

[0147] Oxides of rare earth elements: more than 3% and less than 60%;

[0148] Other oxides: 0% to 18%.

[0149] The use of the zirconium oxide-containing alumina-based composite oxide is not particularly limited, and the composite oxide can be used, for example, as a catalyst support for an exhaust gas-purifying catalyst (exhaust gas-purifying catalyst support).

[0150] [Method for preparing zirconium oxide-containing alumina-based composite oxide]

[0151] Hereinafter, an example of a method for producing a zirconium oxide-containing alumina-based composite oxide will be described. However, the method for producing a zirconium oxide-containing alumina-based composite oxide of the present invention is not limited to the following example.

[0152] The method for preparing the zirconium oxide-containing alumina composite oxide of this embodiment includes:

[0153] Step 1, adding a basic zirconium salt to an aqueous solution of a soluble carbonate and / or a soluble bicarbonate to obtain a solution A;

[0154] Step 2, obtaining a solution B, wherein the solution B contains an aluminum-containing raw material salt and a zirconium-containing raw material salt;

[0155] Step 3, mixing the solution A and the solution B to obtain a precipitate of a zirconium-containing aluminum composite hydroxide; and

[0156] Step 4, heat-treating the precipitate to obtain an alumina-based composite oxide containing zirconium oxide, wherein:

[0157] The amount of the basic zirconium salt added in step 1 is such that zirconium oxide accounts for 1 to 95% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0158] The amount of the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 5 to 99% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0159] The total amount of zirconium oxide contained in the basic zirconium salt added in step 1 and the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 100% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0160] Hereinafter, each step of the method for producing the zirconium oxide-containing alumina-based composite oxide according to the present embodiment will be described.

[0161] (1) Process 1

[0162] In step 1, a solution A is obtained by adding a basic zirconium salt to an aqueous solution of a soluble carbonate and / or a soluble bicarbonate.

[0163] Specifically, in step 1, first, a soluble carbonate and / or a soluble bicarbonate is prepared.

[0164] The soluble carbonate may be ammonium carbonate, sodium carbonate, etc. The soluble bicarbonate may be ammonium bicarbonate, sodium bicarbonate, etc. From the perspective of suppressing residual impurities, the soluble carbonate is preferably ammonium carbonate, and the soluble bicarbonate is preferably ammonium bicarbonate.

[0165] Next, the soluble carbonate and / or the soluble bicarbonate are dispersed in water in a predetermined proportion to obtain an aqueous solution. At this time, ammonia water is preferably used to make the aqueous solution alkaline. The concentration of the aqueous solution ((w / w)%) is preferably not less than 1% and not more than 25%. By setting the concentration to not less than 1%, the concentration can be increased to a certain extent, and the treatment time can be better controlled. In addition, by setting the concentration to not more than 20%, the increase in viscosity during the neutralization process can be suppressed, and compounding can be better performed. The purity of the raw material is preferably not less than 95%, more preferably not less than 98%. The ammonia water is preferably adjusted so that the pH of the obtained aqueous solution is in the range of 7.5 to 14.0.

[0166] In addition, the aqueous solution may be a commercially available aqueous solution that has been prepared in advance as an aqueous solution.

[0167] Next, a basic zirconium salt is added to the aqueous solution to obtain a solution A.

[0168] The alkaline zirconium salt may be sodium zirconium carbonate, ammonium zirconium carbonate, potassium zirconium carbonate, ammonium zirconium oxalate, sodium zirconium oxalate, potassium zirconium oxalate, etc. The alkaline zirconium salt is preferably used as an aqueous solution.

[0169] The amount of the basic zirconium salt added in step 1 is such that zirconium oxide accounts for 1 to 95% by mass of the obtained zirconium oxide-containing alumina-based composite oxide. The reason for this will be described later.

[0170] (2) Process 2

[0171] In step 2, a solution B containing a raw material salt containing aluminum and a raw material salt containing zirconium is obtained. The solution B may contain aluminum alone as a metal or may contain two or more metals including aluminum.

[0172] The raw material salt containing aluminum may be, for example, at least one of aluminum nitrate, aluminum chloride, etc. Among them, nitrate-based raw material salts are more preferred than chloride-based raw material salts in terms of suppressing residual impurities.

[0173] The metal other than aluminum may be, for example, one or more of: 1) cerium; 2) zirconium; and 3) rare earth elements other than Pm.

[0174] The raw material salt containing cerium may be, for example, at least one of cerium nitrate, cerium chloride, cerium acetate, etc. Among them, cerium nitrate belonging to the nitrate system is preferred.

[0175] The zirconium-containing raw material salt may be at least one of zirconium oxynitrate, zirconium oxychloride, zirconium nitrate, etc., as long as it is a raw material salt that provides zirconium ions. Among them, nitrate-based zirconium oxynitrate is preferred.

[0176] The rare earth element other than Pm may be, for example, at least one of Sc, Y, La, Nd, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu.

[0177] In addition to the above elements, it may also contain (A) at least one element selected from the group consisting of In, Si, Sn, Bi, P, and Zn; (B) transition metal elements (excluding rare earth elements and precious metal elements); and (C) one or more alkaline earth metal elements.

[0178] The raw materials for rare earth elements, transition metals (excluding rare earth elements and precious metals), alkaline earth metals, In, Si, Sn, Bi, and P are not particularly limited, as long as they are water-soluble. Nitrates, sulfates, acetates, chlorides, bromides, and the like can be used, but nitrates are preferred to minimize residual impurities. The purity of these raw materials is preferably 95% or higher, more preferably 98% or higher.

[0179] The solvent used to prepare the solution B may be appropriately selected depending on the type of the raw material salt, and water (pure water, ion-exchanged water, etc., the same below) is usually preferably used.

[0180] Next, these compounds (metal salts) are mixed in predetermined proportions. The metal salt concentration in Solution B is preferably 1% to 15% as oxide. Setting the concentration to 1% or higher allows for a certain degree of concentration increase, allowing for better control of the treatment time. Furthermore, setting the concentration to 15% or lower suppresses viscosity increases during neutralization, enabling better composite formation.

[0181] The amount of the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 5 to 99% by mass of the obtained zirconium oxide-containing alumina-based composite oxide.

[0182] The total amount of zirconium oxide contained in the basic zirconium salt added in step 1 and the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 100% by mass of the obtained zirconium oxide-containing alumina composite oxide.

[0183] In step 1, the amount of basic zirconium salt added is set so that zirconium oxide accounts for 1 to 95 mass % of the obtained zirconium oxide-containing alumina composite oxide. In step 2, the remaining zirconium oxide is added to control R to an appropriate value.

[0184] (3) Process 3

[0185] In step 3, a precipitate of a zirconium-containing aluminum composite hydroxide is obtained by mixing the solution A and the solution B. Note that the hydroxide may contain carbonate.

[0186] Specifically, in step 3, solution A obtained in step 1 and solution B obtained in step 2 are first mixed and neutralized. The mixing method is not particularly limited, but from the perspective of production efficiency such as filterability in the next step, solution B prepared in step 2 is preferably added to solution A prepared in step 1.

[0187] Next, the generated zirconium-containing alumina composite hydroxide is recovered by solid-liquid separation. The solid-liquid separation may be performed by a known method such as filtration, centrifugation, or decantation.

[0188] Next, if necessary, the recovered material can be suspended in diluted ammonia water and aged at a temperature between 20°C and 80°C for a period of 10 to 1500 minutes. The concentration of the diluted ammonia water is preferably between 0.1% and 15% by mass, and more preferably between 0.2% and 10% by mass. Setting the concentration of the diluted ammonia water within this range removes impurities other than those in the target composition. Furthermore, impurities that promote the growth of alumina and zirconia crystals can be removed.

[0189] The amount of diluted ammonia added to the recyclate is preferably in the range of 0.1 g to 1000 g, preferably 1 g to 100 g, based on the oxide content per 100 g. Setting the amount of diluted ammonia added to the recyclate within this range allows for the removal of impurities other than those in the target composition. Furthermore, impurities that promote the growth of alumina and zirconia crystals can be removed.

[0190] The temperature during the aging process is more preferably 20°C to 75°C, and even more preferably 25°C to 70°C.

[0191] The aging time is more preferably from 15 minutes to 900 minutes, and even more preferably from 20 minutes to 360 minutes.

[0192] The aging can remove impurities other than the target composition and impurities that promote the growth of alumina and zirconia crystals.

[0193] After aging, the suspension is recovered by solid-liquid separation. The solid-liquid separation may be performed by a known method such as filtration, centrifugation, or decantation.

[0194] After recovery, the obtained zirconium-containing alumina-based composite hydroxide is preferably washed as necessary to remove adhering impurities.

[0195] It should be noted that the obtained zirconium-containing alumina composite hydroxide may be dried as needed. The drying method may be, for example, natural drying, heat drying, or any of the like, as long as it is carried out according to a known method. In addition, if necessary, the drying process may be followed by pulverization, classification, or the like.

[0196] (4) Process 4

[0197] In step 4, the precipitate (recovered product) is heat-treated to obtain a zirconium-containing alumina-based composite oxide.

[0198] The heat treatment temperature is preferably 400°C to 1200°C, more preferably 500°C to 1150°C, and even more preferably 600°C to 1100°C.

[0199] The heat treatment time is preferably from 1 hour to 12 hours, more preferably from 2 hours to 11 hours, and even more preferably from 3 hours to 10 hours.

[0200] The composite oxide obtained by heat treatment may be pulverized as needed. The pulverization method is not particularly limited and can be performed using a common pulverizer such as a planetary mill, a ball mill, a hammer mill, or a jet mill.

[0201] In the above-mentioned method for preparing a zirconium oxide-containing aluminum oxide composite oxide, an alkaline zirconium solution (Solution A) can be used as a neutralizing agent raw material to precipitate an aluminum salt (Step 3), thereby highly dispersing fine ZrO2 within the precursor (the zirconium-containing aluminum composite hydroxide). This suppresses the crystallization of certain elements during high-temperature heating, thereby maintaining the θ phase even after high-temperature heating.

[0202] In summary, the zirconium oxide-containing alumina-based composite oxide obtained by the production method of this embodiment can suppress the crystallization of the α phase under high-temperature heating conditions and suppress the reduction of the specific surface area.

[0203] Example

[0204] The present invention will be described in detail below with reference to the following examples. However, the present invention is not limited to the following examples without departing from the spirit of the present invention. It should be noted that in the examples and comparative examples, the obtained zirconium oxide-containing alumina-based composite oxide contains 1 to 3% by mass of hafnium as an unavoidable impurity relative to zirconium (calculated according to the following formula (X)).

[0205] <Formula (X)>

[0206] ([Mass of hafnium] / ([Mass of zirconium]+[Mass of hafnium]))×100(%)

[0207] The maximum and minimum values ​​of the content of each component shown in the following examples are irrelevant to the contents of other components and should be regarded as the preferred minimum and preferred maximum values ​​of the present invention.

[0208] Furthermore, the maximum and minimum values ​​of the measured values ​​shown in the following examples are irrelevant to the content (composition) of each component and should be regarded as the preferred minimum and maximum values ​​of the present invention.

[0209] [Preparation of Zirconia-Containing Alumina-Based Composite Oxide]

[0210] (Example 1)

[0211] 250 g of sodium carbonate was dissolved in 1750 g of water, and after adding 250 g of 20% by mass ammonia water, a sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 0.3 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution (solution A).

[0212] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 96.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 1.7 g in terms of zirconium oxide), and lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide) were dissolved in ion exchange water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution (solution B).

[0213] Next, the nitrate aqueous solution (solution B) was added to the zirconium-containing alkaline aqueous solution (solution A), thereby obtaining a precipitate of the zirconium-containing aluminum oxide composite hydroxide.

[0214] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0215] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0216] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 1.

[0217] (Example 2)

[0218] 250 g of sodium carbonate was dissolved in 1750 g of water, and after adding 250 g of 20% by mass ammonia water, sodium zirconium carbonate solution (First Rare Element Chemical Industry, 1.8 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution (solution A).

[0219] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 96.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 0.2 g in terms of zirconium oxide), and lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide) were dissolved in ion exchange water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution (solution B).

[0220] Next, the nitrate aqueous solution (solution B) was added to the zirconium-containing alkaline aqueous solution (solution A), thereby obtaining a precipitate of the zirconium-containing aluminum oxide composite hydroxide.

[0221] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0222] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0223] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 2.

[0224] (Example 3)

[0225] 230 g of sodium carbonate was dissolved in 1700 g of water, 230 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 0.6 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0226] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 90.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 3.4 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of cerium oxide), and lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxides, thereby preparing an aqueous nitrate solution.

[0227] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an alumina-based composite hydroxide containing zirconium oxide.

[0228] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0229] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0230] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 3.

[0231] (Example 4)

[0232] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (First Rare Element Chemical Industry, 1.2 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0233] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 78.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 6.8 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 8.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0234] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0235] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0236] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0237] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 4.

[0238] (Example 5)

[0239] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (First Rare Element Chemical Industry, 2.3 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0240] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 69.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 12.7 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), praseodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of praseodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0241] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0242] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0243] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 1100° C. for 10 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0244] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 5.

[0245] (Example 6)

[0246] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (First Rare Element Chemical Industry, 12.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0247] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 69.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 3.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), praseodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of praseodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0248] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0249] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0250] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 1100° C. for 10 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0251] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 6.

[0252] (Example 7)

[0253] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (produced by Daiichi Rare Element Chemical Industry, 3.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0254] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 64.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 17.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and praseodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of praseodymium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0255] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0256] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0257] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0258] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 7.

[0259] (Example 8)

[0260] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 4.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0261] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 44.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 25.5 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 20.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the content reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0262] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0263] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0264] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 8.

[0265] (Example 9)

[0266] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 7.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0267] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 30.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 42.5 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0268] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0269] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0270] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0271] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 9.

[0272] (Example 10)

[0273] 110 g of sodium carbonate was dissolved in 1090 g of water, 160 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 9.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0274] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 20.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 51.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0275] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0276] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0277] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 500° C. for 3 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0278] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 10.

[0279] (Example 11)

[0280] 110 g of sodium carbonate was dissolved in 1090 g of water, 160 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (First Rare Element Chemical Industry, 10.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0281] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 20.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 59.5 g in terms of zirconium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0282] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0283] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0284] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 600° C. for 3 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0285] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 11.

[0286] (Example 12)

[0287] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 7.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0288] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 42.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 42.5 g in terms of zirconium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of lanthanum oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0289] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0290] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0291] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 12.

[0292] (Example 13)

[0293] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (produced by Daiichi Rare Element Chemical Industry, 3.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0294] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 44.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 17.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 30.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0295] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0296] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0297] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 13.

[0298] (Example 14)

[0299] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (produced by Daiichi Rare Element Chemical Industry, 3.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0300] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 34.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 17.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 40.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0301] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0302] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0303] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 14.

[0304] (Example 15)

[0305] 170 g of sodium carbonate was dissolved in 1230 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (produced by Daiichi Rare Element Chemical Industry, 3.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0306] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 54.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 17.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of neodymium oxide), praseodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of praseodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0307] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0308] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 1100° C. for 1 hour in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0309] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 15.

[0310] (Example 16)

[0311] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (produced by Daiichi Rare Element Chemical Industry, 3.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0312] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 30.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 17.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of neodymium oxide), praseodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of praseodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0313] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0314] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0315] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 16.

[0316] (Example 17)

[0317] 170 g of sodium carbonate was dissolved in 1230 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 4.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0318] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 50.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 25.5 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide), and magnesium nitrate (4.0 g in terms of magnesium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0319] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0320] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0321] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0322] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 17.

[0323] (Example 18)

[0324] 170 g of sodium carbonate was dissolved in 1230 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 4.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0325] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 50.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 25.5 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide), and calcium nitrate (4.0 g in terms of calcium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0326] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0327] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0328] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0329] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 18.

[0330] (Example 19)

[0331] 170 g of sodium carbonate was dissolved in 1230 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 4.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0332] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 50.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 25.5 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide), and strontium nitrate (4.0 g in terms of strontium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0333] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0334] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0335] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0336] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 19.

[0337] (Example 20)

[0338] 170 g of sodium carbonate was dissolved in 1230 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 4.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0339] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 50.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 25.5 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide), and barium nitrate (4.0 g in terms of barium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0340] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0341] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0342] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0343] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 20.

[0344] (Example 21)

[0345] 170 g of sodium carbonate was dissolved in 1230 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 4.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0346] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 50.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 25.5 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide), and ammonium phosphate (4.0 g in terms of phosphate) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0347] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0348] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0349] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0350] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 21.

[0351] (Example 22)

[0352] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (First Rare Element Chemical Industry, 8.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0353] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 30.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 32.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 20.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0354] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0355] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0356] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0357] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 22.

[0358] (Example 23)

[0359] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 6.6 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0360] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 30.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 37.4 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 20.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the content reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0361] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0362] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0363] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0364] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and this was used as the zirconia-containing alumina-based composite oxide of Example 23.

[0365] (Example 24)

[0366] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 6.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0367] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 29.5 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 37.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 20.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide), and iron (III) nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 1.0 g in terms of iron oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0368] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0369] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0370] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0371] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 24.

[0372] (Example 25)

[0373] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 6.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0374] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 29.5 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 37.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 20.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide), and a dinitrodiammineplatinum nitric acid solution (Tanaka Kikinzoku, Ltd., 1.0 g in terms of platinum metal) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0375] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0376] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0377] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0378] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and this was used as the zirconia-containing alumina-based composite oxide of Example 25.

[0379] (Example 26)

[0380] 150 g of sodium carbonate was dissolved in 1150 g of water, 200 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 6.5 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0381] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 29.5 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 37.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 20.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide), and rhodium nitrate (Tanaka Kikinzoku, Ltd., 1.0 g in terms of metallic rhodium) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0382] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0383] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water having a concentration of 20% by mass to 2000 g of water, and aged at 50° C. for 180 minutes.

[0384] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0385] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 26.

[0386] (Example 27)

[0387] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 0.7 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0388] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 89.6 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 3.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 3.7 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), and strontium (II) nitrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 1.0 g in terms of strontium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0389] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0390] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0391] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 27.

[0392] (Example 28)

[0393] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 0.7 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0394] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 89.6 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 3.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 3.7 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), and ammonium dihydrogen phosphate (Wako Pure Chemical Industries, Ltd., special grade reagent, 1.0 g in terms of phosphoric acid) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxides, thereby preparing an aqueous nitrate solution.

[0395] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0396] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0397] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and this was used as the zirconia-containing alumina-based composite oxide of Example 28.

[0398] (Example 29)

[0399] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 0.7 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0400] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 89.6 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 3.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 3.7 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), and fumed silica AEROSIL (Japan AEROSIL, 1.0 g in terms of silicic acid) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxides, thereby preparing an aqueous nitrate solution.

[0401] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0402] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0403] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 29.

[0404] (Example 30)

[0405] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 0.7 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0406] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 89.6 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 3.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 3.7 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), and titanium (IV) tetrachloride (Wako Pure Chemical Industries, Ltd., 1.0 g in terms of titanium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing a nitrate aqueous solution and a chloride aqueous solution.

[0407] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0408] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0409] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 30.

[0410] (Example 31)

[0411] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 4.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0412] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 60.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 22.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0413] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0414] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water to 2000 g of water, and aged at 50° C. for 180 minutes.

[0415] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0416] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 31.

[0417] (Example 32)

[0418] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (Daichi Rare Element Chemical Industry, 10.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0419] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 60.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 16.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0420] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0421] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water to 2000 g of water, and aged at 50° C. for 180 minutes.

[0422] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0423] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 32.

[0424] (Example 33)

[0425] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (First Rare Element Chemical Industry, 16.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0426] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 60.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 10.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0427] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0428] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water to 2000 g of water, and aged at 50° C. for 180 minutes.

[0429] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0430] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Example 33.

[0431] (Comparative Example 1)

[0432] 400 g of ammonium bicarbonate was dissolved in 7600 g of water to prepare a 5% ammonium bicarbonate aqueous solution.

[0433] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 96.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 2.0 g in terms of zirconium oxide), and lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide) were dissolved in ion exchange water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0434] Next, the nitrate aqueous solution was added to the 5% ammonium bicarbonate aqueous solution to obtain a precipitate of a zirconium oxide-containing alumina-based composite hydroxide.

[0435] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0436] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill, and the zirconia-containing alumina-based composite oxide was used as the zirconia-containing alumina-based composite oxide of Comparative Example 1.

[0437] (Comparative Example 2)

[0438] 400 g of ammonium bicarbonate was dissolved in 7600 g of water to prepare a 5% ammonium bicarbonate aqueous solution.

[0439] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 90.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 4.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of cerium oxide), and lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxides, thereby preparing an aqueous nitrate solution.

[0440] Next, the nitrate aqueous solution was added to the 5% ammonium bicarbonate aqueous solution to obtain a precipitate of a zirconium oxide-containing alumina-based composite hydroxide.

[0441] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0442] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill and used as the zirconia-containing alumina-based composite oxide of Comparative Example 2.

[0443] (Comparative Example 3)

[0444] 400 g of ammonium bicarbonate was dissolved in 7600 g of water to prepare a 5% ammonium bicarbonate aqueous solution.

[0445] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 78.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 8.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 8.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0446] Next, the nitrate aqueous solution was added to the 5% ammonium bicarbonate aqueous solution to obtain a precipitate of a zirconium oxide-containing alumina-based composite hydroxide.

[0447] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0448] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill and used as the zirconia-containing alumina-based composite oxide of Comparative Example 3.

[0449] (Comparative Example 4)

[0450] 400 g of ammonium bicarbonate was dissolved in 7600 g of water to prepare a 5% ammonium bicarbonate aqueous solution.

[0451] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 64.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 20.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and praseodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of praseodymium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0452] Next, the nitrate aqueous solution was added to the 5% ammonium bicarbonate aqueous solution to obtain a precipitate of a zirconium oxide-containing alumina-based composite hydroxide.

[0453] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0454] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill and used as the zirconia-containing alumina-based composite oxide of Comparative Example 4.

[0455] (Comparative Example 5)

[0456] 400 g of ammonium bicarbonate was dissolved in 7600 g of water to prepare a 5% ammonium bicarbonate aqueous solution.

[0457] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 44.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 20.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 30.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0458] Next, the nitrate aqueous solution was added to the 5% ammonium bicarbonate aqueous solution to obtain a precipitate of a zirconium oxide-containing alumina-based composite hydroxide.

[0459] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0460] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill and used as the zirconia-containing alumina-based composite oxide of Comparative Example 6.

[0461] (Comparative Example 6)

[0462] 400 g of ammonium bicarbonate was dissolved in 7600 g of water to prepare a 5% ammonium bicarbonate aqueous solution.

[0463] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 30.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 40.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 20.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of lanthanum oxide), neodymium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of neodymium oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 4.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0464] Next, the nitrate aqueous solution was added to the 5% ammonium bicarbonate aqueous solution to obtain a precipitate of a zirconium oxide-containing alumina-based composite hydroxide.

[0465] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0466] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill and used as the zirconia-containing alumina-based composite oxide of Comparative Example 5.

[0467] (Comparative Example 7)

[0468] 400 g of ammonium bicarbonate was dissolved in 7600 g of water to prepare a 5% ammonium bicarbonate aqueous solution.

[0469] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 60.0 g in terms of aluminum oxide), zirconium oxynitrate (Mizuwa Chemical Industry, special grade reagent, 26.0 g in terms of zirconium oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxide, thereby preparing an aqueous nitrate solution.

[0470] Next, the nitrate aqueous solution was added to the 5% ammonium bicarbonate aqueous solution to obtain a precipitate of a zirconium oxide-containing alumina-based composite hydroxide.

[0471] Next, the precipitate was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0472] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill and used as the zirconia-containing alumina-based composite oxide of Comparative Example 7.

[0473] (Comparative Example 8)

[0474] 200 g of sodium carbonate was dissolved in 1300 g of water, 220 g of 20% by mass ammonia water was added, and then sodium zirconium carbonate solution (First Rare Element Chemical Industry, 26.0 g in terms of zirconium oxide) was added to prepare a zirconium-containing alkaline aqueous solution.

[0475] Next, aluminum nitrate nonahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 60.0 g in terms of aluminum oxide), cerium (III) nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 10.0 g in terms of cerium oxide), lanthanum nitrate hexahydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of lanthanum oxide), and yttrium (III) nitrate hydrate (Wako Pure Chemical Industries, Ltd., special grade reagent, 2.0 g in terms of yttrium oxide) were dissolved in ion-exchanged water until the concentration reached 5% in terms of oxides, thereby preparing an aqueous nitrate solution.

[0476] Next, the nitrate aqueous solution was added to the zirconium-containing alkaline aqueous solution to obtain a precipitate of an aluminum oxide-based composite hydroxide containing zirconium oxide.

[0477] Next, the precipitate was recovered by solid-liquid separation, suspended in diluted ammonia water obtained by adding 200 g of ammonia water to 2000 g of water, and aged at 50° C. for 180 minutes.

[0478] The aged suspension was recovered by solid-liquid separation, and the solid portion was fired in an electric furnace at 900° C. for 5 hours in the atmosphere to obtain a zirconium oxide-containing alumina-based composite oxide.

[0479] The zirconia-containing alumina-based composite oxide was pulverized using a hammer mill and used as the zirconia-containing alumina-based composite oxide of Comparative Example 8.

[0480] [X-ray diffraction spectrum]

[0481] The zirconium oxide-containing alumina composite oxides of Examples and Comparative Examples were heated at 1200°C for 12 hours under atmospheric pressure (0.1013 MPa, air atmosphere). X-ray diffraction spectra of each heated zirconium oxide-containing alumina composite oxide were obtained using an X-ray diffraction apparatus ("Ultima IV" manufactured by Rigaku). The measurement conditions are as follows.

[0482] <Measurement Conditions>

[0483] Measurement apparatus: X-ray diffraction apparatus (Rigaku Ultima IV)

[0484] Line source: CuKα line source

[0485] Tube voltage: 50kV

[0486] Tube current: 30mA

[0487] Scanning speed: 2θ=20~65°: 4° / min

[0488] Cumulative number of times: 1

[0489] Divergence slit: 1°

[0490] Scattering slit: 1°

[0491] Light receiving slit: 0.3mm

[0492] Monochromator: Use

[0493] Then, from the obtained X-ray diffraction spectrum (XRD pattern), the peak intensity originating from the θ-Al2O3 phase near 2θ = 33° was defined as X, the peak intensity originating from the α-Al2O3 phase near 2θ = 26° was defined as Y, and [X / Y] was defined as R to determine R. The results are shown in Tables 1 to 5.

[0494] Furthermore, [Z / W], or Tr, was calculated based on the peak intensity Z of ZrO2 originating near 2θ = 30° in the obtained X-ray diffraction spectrum (XRD pattern) and the mass ratio W of the ZrO2 oxide component relative to the total zirconium oxide-containing alumina composite oxide. The results are shown in Tables 1 to 5. It should be noted that "peak intensity Z" refers to the absolute value of the peak intensity, as can be seen from the fact that the unit of the ZrO2 peak intensity in Tables 1 to 5 is cps (counts per second).

[0495] The X-ray diffraction spectra of the alumina-based composite oxide containing zirconium oxide after heating in Example 1, Example 2, Comparative Example 1, Example 3, Comparative Example 2, Example 4, Comparative Example 3, Example 7, Comparative Example 4, Example 13, Comparative Example 5, Example 22, Comparative Example 6, Example 31, Example 32, Example 33, Comparative Example 7, and Comparative Example 8 are respectively Figures 1 to 18 Shown in.

[0496] [Particle size D 50 Determination of

[0497] 0.15 g of the zirconium oxide-containing alumina composite oxides from the examples and comparative examples and 40 ml of a 0.2% sodium hexametaphosphate aqueous solution were placed in a 50 ml beaker and dispersed for 5 minutes using an ultrasonic cleaner "VS-100III" (manufactured by VELVO-CLEAR). The mixture was then placed in a laser diffraction / scattering particle size distribution analyzer ("LA-950" manufactured by Horiba Ltd.) and measured. The results are shown in Tables 1 to 5.

[0498] [Measurement of specific surface area before heating]

[0499] The specific surface areas of the zirconium oxide-containing alumina composite oxides of Examples and Comparative Examples were measured by the BET method using a specific surface area meter ("Macsorb" manufactured by MOUNTECH). The results are shown in Tables 1 to 5.

[0500] [Measurement of specific surface area after heating at 1200°C for 12 hours under atmospheric pressure]

[0501] The zirconium oxide-containing alumina composite oxides of Examples and Comparative Examples were heated at 1200°C for 12 hours under atmospheric pressure (0.1013 MPa, air atmosphere). The specific surface area of ​​each zirconium oxide-containing alumina composite oxide after heating was measured using the BET method using a specific surface area meter ("Macsorb" manufactured by MOUNTECH). The results are shown in Tables 1 to 5.

[0502] Table 1

[0503] Table 2

[0504]

[0505] Table 3

[0506]

[0507] Table 4

[0508]

[0509] Table 5

[0510]

Claims

1. An alumina-based composite oxide containing zirconium oxide, characterized in that: Contains zirconium oxide and aluminum oxide, In the XRD pattern A after heating at 1200°C for 12 hours under atmospheric pressure, when the peak intensity of the θ-Al2O3 phase at about 2θ = 33° is represented by X, the peak intensity of the α-Al2O3 phase at about 2θ = 26° is represented by Y, and [X / Y] is represented by R, R satisfies the following formula [1]: Formula [1] 0.25 <R<5.0。 2. The zirconium oxide-containing alumina-based composite oxide according to claim 1, wherein In the XRD pattern A, the peak intensity of ZrO2 originating from the vicinity of 2θ=30° is defined as Z, the mass ratio of the oxide component of ZrO2 to the entire alumina-based composite oxide containing zirconium oxide is defined as W, and [Z / W] is defined as Tr. Tr satisfies the following formula [2]: Formula [2] 1.70 <Tr<25.0。 3. The zirconium oxide-containing alumina-based composite oxide according to claim 2, wherein The R satisfies the following formula [3]: Formula [3] 0.35 <R<3.5。 4. The zirconium oxide-containing alumina-based composite oxide according to claim 3, wherein The Tr satisfies the following formula [4]: Formula [4] 1.72 <Tr<20.0。 5. The zirconium oxide-containing alumina-based composite oxide according to claim 4, wherein The content of aluminum oxide is 15 mass % or more and 97 mass % or less.

6. The zirconium oxide-containing alumina-based composite oxide according to claim 5, characterized in that The content of zirconium oxide is 0.1 mass % or more and 75 mass % or less.

7. The zirconium oxide-containing alumina-based composite oxide according to claim 6, characterized in that Oxides containing rare earth elements other than Pm.

8. A method for preparing a zirconium oxide-containing alumina composite oxide, characterized in that: include: Step 1, adding a basic zirconium salt to an aqueous solution of a soluble carbonate and / or a soluble bicarbonate to obtain a solution A; Step 2, obtaining a solution B, wherein the solution B contains an aluminum-containing raw material salt and a zirconium-containing raw material salt; Step 3, mixing the solution A and the solution B to obtain a precipitate of a zirconium-containing aluminum composite hydroxide; as well as Step 4, heat-treating the precipitate to obtain an alumina-based composite oxide containing zirconium oxide, in, The amount of the basic zirconium salt added in step 1 is such that zirconium oxide accounts for 1 to 95% by mass of the obtained zirconium oxide-containing alumina composite oxide. The amount of the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 5 to 99% by mass of the obtained zirconium oxide-containing alumina composite oxide. The total amount of zirconium oxide contained in the basic zirconium salt added in step 1 and the zirconium-containing raw material salt added in step 2 is such that zirconium oxide accounts for 100% by mass of the obtained zirconium oxide-containing alumina composite oxide.

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