Novel composite oxides and oxygen storage materials containing them

Abstract

To provide an inexpensive oxygen storage material with excellent oxygen release performance at low temperatures. [Solution] One embodiment is the general formula Ce 2-w-x’ A w A' x’ B 1-y’-z B' y’ B'' z O 6-w / 2-x’-z A composite oxide having the composition represented by the formula, where A is a rare earth metal element excluding Ce, A' is an alkaline earth metal element, B is Ti and a group 14 element, B' is a group 13 element, and B'' is a group 12 element; 2-w-x', w, x', 1-y'-z, y', z, and 6-w / 2-x'-z are the molar ratios of Ce, A, A', B, B', B'', and O when B+B'+B'' is 1, respectively; w, x, y, and z satisfy 0≦w<2, 0≦x<0.5, 0≦y≦1, and 0≦z≦0.5 respectively; w+x' satisfies 0≦w+x'<2; and y'+z satisfies 0≦y'+z≦1.

Description

[Technical Field]

[0001] One aspect of the present invention relates to a novel composite oxide and an oxygen storage material containing the same. [Background technology]

[0002] Exhaust gases emitted from internal combustion engines in automobiles and other vehicles contain carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx). x ) and other harmful components are contained, and these harmful components are purified by an exhaust gas purification catalyst before being released into the atmosphere. Conventionally, this exhaust gas purification catalyst oxidizes CO, HC and NO x A three-way catalyst is used to perform reduction and resorption simultaneously. Commonly used three-way catalysts include those in which precious metals such as platinum (Pt), palladium (Pd), and rhodium (Rh) are supported on porous oxide supports such as alumina (Al2O3), silica (SiO2), zirconia (ZrO2), and titania (TiO2).

[0003] In recent years, to enhance the exhaust gas purification performance of three-way catalysts in response to fluctuations in oxygen concentration in exhaust gas, oxygen storage materials, which are inorganic materials with oxygen storage capacity (OSC capacity), have been used in exhaust gas purification catalysts. Ceria (CeO2) is known to have excellent OSC capacity and is widely used as an oxygen storage material in the form of ceria-zirconia composite oxide (CeO2-ZrO2).

[0004] As an oxygen storage material for such ceria-zirconia composite oxides, for example, Patent Document 1 describes a ceria-zirconia composite oxide comprising a ceria and zirconia composite oxide, wherein a pyrochlore-type ordered arrangement phase is formed in the composite oxide by cerium ions and zirconium ions, and the pyrochlore-type ordered arrangement phase remains at a rate of 50% or more compared to before heating after heating in air at a temperature of 1000°C for 5 hours.

[0005] Patent Document 2 discloses a ceria-zirconia-titania-based composite oxide containing cerium, zirconium, and titanium, in which at least a part of the titanium is dissolved in the composite oxide of the cerium and the zirconium, and the intensity (I 222 ) of the main peak of the diffraction line attributed to the (222) plane obtained from the X-ray diffraction pattern using CuKα obtained by X-ray diffraction measurement, relative to the intensity (I 111 ) of the superlattice peak of the diffraction line attributed to the (111) plane, the ratio (I 111 / I 222 ) satisfies the following condition (1): 2 ≤ {(I 111 / I 222 ) × 100} ≤ 15 (1). An oxygen storage material characterized by being composed of the above-mentioned ceria-zirconia-titania-based composite oxide is described.

[0006] Patent Document 3 discloses an oxygen storage material composed of a Ce-Zr-Ln-Ti-based composite oxide containing cerium (Ce), zirconium (Zr), rare earth elements (Ln: excluding cerium), and titanium (Ti), in which at least a part of the rare earth elements and at least a part of the titanium are dissolved in the composite oxide of the cerium and the zirconium, and the Ce-Zr-Ln-Ti-based composite oxide has the following chemical formula (1): Ce a-x Ln x Zr b-y Ti y O δ (1) (In Chemical Formula (1), a, b, x, and y are numbers that satisfy the conditions of a = 0.4 to 0.6, b = 0.4 to 0.6, x = 0 to a (excluding x = 0 and x = a), y = 0 to 0.3 (excluding y = 0), and a + b = 1, and δ is a number of 1.7 to 2.2.) An oxygen storage material characterized by having the composition represented thereby is described.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

[0008] However, in ceria-zirconia composite oxides where a pyrochlore-type ordered phase is formed, as described in Patent Documents 1-3, the use of the rare metal zirconium (Zr) can increase costs. Furthermore, these composite oxides have the problem of having a high activation energy for releasing excess oxygen from the crystal structure, and requiring a high temperature for oxygen release.

[0009] Therefore, one aspect of the present invention aims to provide an inexpensive oxygen storage material with excellent oxygen release performance at low temperatures. [Means for solving the problem]

[0010] As a result of various investigations into means to solve the above problems, the inventors of the present invention have found that a novel composite oxide having a Ce2TiO6 type crystal structure containing Ce and titanium (Ti) has superior oxygen storage and oxygen release properties at low temperatures compared to Ce2Zr2O7, which has a pyrochlore type crystal structure containing Ce and Zr and is useful as an existing oxygen storage material, and have completed one aspect of the present invention. Furthermore, the inventors of the present invention have found that a novel composite oxide having a Ce2TiO6 type crystal structure containing aluminum (Al) in addition to Ce and titanium (Ti) has superior oxygen storage and oxygen release properties at low temperatures compared to Ce2Zr2O7, which has a pyrochlore type crystal structure containing Ce and Zr and is useful as an existing oxygen storage material, and has an even larger oxygen storage capacity than Ce2TiO6, and have completed one aspect of the present invention.

[0011] In other words, the gist of one aspect of the present invention is as follows: (1) General formula Ce 2-x A x BO 6-yA composite oxide having the composition represented by the formula, wherein A is one or more elements selected from rare earth metal elements excluding Ce, B is one or more elements selected from the group consisting of titanium (Ti) and group 14 elements, 2-x, x, and 6-y are the molar ratios of Ce, A, and O when B is 1, and x and y satisfy 0 ≤ x < 2 and 0 ≤ y ≤ 0.5x, respectively. (2) In an X-ray diffraction pattern measured using CuKα as the X-ray source with a 2θ range of 5deg. to 90deg., the angle of the maximum X-ray diffraction peak showing the highest intensity is within the range of 2θ to 27deg. to 31deg., and the peak intensity of the maximum X-ray diffraction peak is I a Let I be the maximum peak intensity among the X-ray diffraction peaks where 2θ is in the range of 32deg. to 36deg. b When that happens, I b / I a However, 0.15≦I b / I a The composite oxide described in (1) that satisfies ≤0.85. (3) In the crystal structure determined by X-ray diffraction after heating at 500°C in air for 6 hours, when the space group is Pnma and the Z value is 4, the lattice constants a, b, and c and the lattice volume V are 10.1 Å ≤ a ≤ 11.1 Å, 3.68 Å ≤ b ≤ 3.97 Å, 10.7 Å ≤ c ≤ 11.6 Å, and 419 Å, respectively. 3 ≤V ≤ 480Å 3 A composite oxide according to (1) or (2) that satisfies (however, the numerical values ​​between lattice constants a, b, and c may be interchangeable). (4) A composite oxide according to any one of (1) to (3), wherein A is one or more elements selected from the group consisting of yttrium (Y), lanthanum (La), praseodymium (Pr), and samarium (Sm). (5) A composite oxide described in any one of (1) to (4), such that x satisfies 0 ≤ x ≤ 1.5. (6) A composite oxide according to any one of (1) to (5), wherein B is one or more elements selected from the group consisting of titanium (Ti) and silicon (Si). (7) A composite oxide according to any one of (1) to (6), wherein y is 0 ≤ y ≤ 0.2. (8) An oxygen storage material comprising a composite oxide described in any one of (1) to (7). (9) The oxygen storage material according to (8), wherein a catalyst metal is supported on the composite oxide. (10) The oxygen storage material according to (9), wherein the catalyst metal is one or more elements selected from the group consisting of rhodium (Rh), palladium (Pd), and platinum (Pd). (11) A catalyst for exhaust gas purification comprising a composite oxide described in any one of (1) to (7), or an oxygen storage material described in any one of (8) to (10). (12) A redox catalyst comprising a composite oxide described in any one of (1) to (7), or an oxygen storage material described in any one of (8) to (10). (13) A method for storing oxygen using a composite oxide described in any one of (1) to (7), or an oxygen storage material described in any one of (8) to (10). (14) A method for enriching oxygen using a composite oxide described in any one of (1) to (7), or an oxygen storage material described in any one of (8) to (10). (15) A method for removing oxygen using a composite oxide described in any one of (1) to (7), or an oxygen storage material described in any one of (8) to (10). (16) A heating and cooling method using a composite oxide described in any one of (1) to (7), or an oxygen storage material described in any one of (8) to (10). A method for producing a composite oxide according to any one of (17)(1) to (7), comprising the steps of preparing a precursor containing a metal element of the composite oxide and heating the precursor in a reducing atmosphere. (18) General formula Ce 2-w-x’ A w A' x’ B 1-y’-z B' y’ B'' z O 6-w / 2-x’-zA composite oxide having a composition represented by the formula, wherein A is one or more elements selected from rare earth metal elements excluding Ce, A' is one or more elements selected from alkaline earth metal elements, B is one or more elements selected from the group consisting of titanium (Ti) and Group 14 elements, B' is one or more elements selected from the group consisting of Group 13 elements, and B'' is one or more elements selected from the group consisting of Group 12 elements. The above elements, where 2-w-x', w, x', 1-y'-z, y', z, and 6-w / 2-x'-z are the molar ratios of Ce, A, A', B, B', B'', and O, respectively, with B+B'+B'' being 1, and w, x', y', and z satisfy 0≦w<2, 0≦x'<0.5, 0≦y'≦1, and 0≦z≦0.5 respectively, with w+x' satisfying 0≦w+x'<2 and y'+z satisfying 0≦y'+z≦1, are composite oxides. (19) In an X-ray diffraction pattern measured using CuKα as the X-ray source with a 2θ range of 5deg. to 90deg., the angle of the maximum X-ray diffraction peak showing the highest intensity is within the range of 2θ to 31deg., and the peak intensity of the maximum X-ray diffraction peak is I a Let I be the maximum peak intensity among the X-ray diffraction peaks where 2θ is in the range of 32deg. to 37deg. b When that happens, I b / I a However, 0.15≦I b / I a The composite oxide described in (18) that satisfies ≤0.85. (20) In the crystal structure obtained by X-ray diffraction after heating at 500°C in air for 6 hours, when the space group is Pnma and the Z value is 4, the lattice constants a, b, and c and the lattice volume V are 10.1 Å ≤ a ≤ 11.1 Å, 3.64 Å ≤ b ≤ 3.97 Å, 10.5 Å ≤ c ≤ 11.7 Å, and 412 Å, respectively. 3 ≤V ≤ 480Å 3 A composite oxide as described in (18) or (19), satisfying the following conditions: (however, the numerical values ​​between lattice constants a, b, and c may be interchangeable). (21) The composite oxide according to any one of (18) to (20), wherein A is at least one element selected from the group consisting of yttrium (Y), lanthanum (La), praseodymium (Pr), samarium (Sm), europium (Eu), and ytterbium (Yb). (22) The composite oxide according to any one of (18) to (21), wherein w satisfies 0 ≦ w ≦ 1.5. (23) The composite oxide according to any one of (18) to (22), wherein A is at least one element selected from the group consisting of calcium (Ca) and strontium (Sr). (24) The composite oxide according to any one of (18) to (23), wherein x' satisfies 0 ≦ x' ≦ 0.1. (25) The composite oxide according to (18) to (24), wherein B is at least one element selected from the group consisting of titanium (Ti) and silicon (Si). (26) The composite oxide according to (18) to (25), wherein B' is at least one element selected from the group consisting of aluminum (Al) and gallium (Ga). (27) The composite oxide according to (18) to (26), wherein B'' is zinc (Zn). (28) The composite oxide according to (18) to (27), wherein z satisfies 0 ≦ z ≦ 0.2. (29) The composite oxide according to (18) to (28), wherein B contains titanium (Ti) and satisfies 0 ≦ 1 - y' - z, or B' contains aluminum (Al) and satisfies 0 < y'. (30) An oxygen storage material comprising the composite oxide according to (18) to (29). (31) The oxygen storage material according to (30), on which a catalytic metal is supported. [[ID=了21]] (32) The oxygen storage material according to (30) or (31), wherein the catalytic metal is at least one element selected from the group consisting of rhodium (Rh), palladium (Pd), and platinum (Pt). (33) An exhaust gas purification catalyst comprising the composite oxide according to any one of (18) to (29), or the oxygen storage material according to any one of (30) to (32). A redox catalyst comprising a composite oxide according to any one of (18) to (29) or an oxygen storage material according to any one of (30) to (32). (35) A method for storing oxygen using a composite oxide according to any one of (18) to (29) or an oxygen storage material according to any one of (30) to (32). (36) A method for enriching oxygen using a composite oxide according to any one of (18) to (29) or an oxygen storage material according to any one of (30) to (32). (37) A method for removing oxygen using a composite oxide according to any one of (18) to (29) or an oxygen storage material according to any one of (30) to (32). (38) A heating and cooling method using a composite oxide according to any one of (18) to (29) or an oxygen storage material according to any one of (30) to (32). (39) A method for producing a composite oxide according to any one of (18) to (29), the method comprising: preparing a precursor containing a metal element of the composite oxide; and heating the precursor in a reducing atmosphere. (40) The method according to (39), wherein 0 < w + x' + y' + z.

Advantages of the Invention

[0012] According to one aspect of the present invention, an inexpensive oxygen storage material excellent in oxygen release performance at low temperatures is provided.

Brief Description of the Drawings

[0013] [Figure 1] A diagram schematically showing the crystal structure (A) of La2TiO5, the crystal structure (B) of a novel composite oxide Ce2TiO6, and the crystal structure (C) of a further novel composite oxide Ce2TiO6-type Ce2Ti0.8Al0.2O5.9. [Figure 2] An X-ray diffraction diagram of the products of Examples 1 to 5 and Comparative Examples 1 to 8. [Figure 3] An X-ray diffraction diagram of the products of Examples 1 to 3 and 6 to 11 and Comparative Example 9. [Figure 4]A shows the H2TPR results of the products before and after Pd loading in Examples 1 and 13 and Comparative Example 3, and B is a graph showing the oxygen storage amount of the products after Pd loading in Examples 1 and 13 and Comparative Example 3. [Figure 5] This graph shows the weight change of the products in Examples 1-11 and Comparative Examples 4-8. [Figure 6] These are X-ray diffraction patterns of the product from Example 1 before and after reduction. [Figure 7] These are X-ray diffraction patterns of the products from Examples 1 and 12-21 and Comparative Examples 11 and 12. [Figure 8] These are X-ray diffraction patterns of the products from Examples 1 and 22-31 and Comparative Examples 10 and 13. [Figure 9] This graph shows the oxygen storage capacity at various temperatures for Examples 1, 3, 4, 13, 19, 20, 26, and 27, and Comparative Example 3, which were supported with Pd. [Modes for carrying out the invention]

[0014] A preferred embodiment of one aspect of the present invention will be described in detail below. This specification describes the features of one aspect of the present invention with reference to the drawings as appropriate. In the drawings, the dimensions and shapes of each part are exaggerated for clarity and do not accurately depict the actual dimensions and shapes. Therefore, the technical scope of one aspect of the present invention is not limited to the dimensions and shapes of each part shown in these drawings. Furthermore, the novel composite oxide and oxygen storage material containing the same according to one aspect of the present invention are not limited to the embodiments described below, and can be implemented in various forms with modifications, improvements, etc. that can be made by those skilled in the art, without departing from the spirit of one aspect of the present invention.

[0015] One aspect of the present invention relates to the general formula Ce 2-x A x BO 6-y This invention relates to a composite oxide having a composition represented by [the given formula], and an oxygen storage material containing the same.

[0016] General formula Ce 2-x A x BO6-y A composite oxide having the composition represented by (hereinafter also referred to as "novel composite oxide") is obtained in an oxidized state, and Ce, A, B, and O, as well as x and y, are as follows.

[0017] Ce is cerium. Cerium is usually tetravalent cerium(IV). O is oxygen.

[0018] A is a rare earth metal element excluding Ce. In one embodiment, A is one or more elements selected from the group consisting of yttrium (Y), lanthanum (La), praseodymium (Pr), samarium (Sm), europium (Eu), terbium (Tb), ytterbium (Yb), and lutetium (Lu). In another embodiment, A is one or more elements selected from the group consisting of Y, La, Pr, and Sm. The valency of A is not limited. The valency of A is usually divalent, trivalent, tetravalent, or a mixture thereof.

[0019] B is one or more elements selected from the group consisting of titanium (Ti) and Group 14 elements. In one embodiment, B is one or more elements selected from the group consisting of Ti, silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). In one embodiment, B is one or more elements selected from the group consisting of Ti and Si. In one embodiment, B includes Ti. When B consists of two or more elements, their ratio is not limited. In one embodiment, B is Ti and Si, and their molar ratio is usually 95:5 to 75:25, and in one embodiment, 90:10 to 80:20. In one embodiment, B is Ti. The valency of B is not limited. The valency of B is usually tetravalent.

[0020] 2-x, x, and 6-y are the molar ratios of Ce, A, and O, respectively, with B being 1. Here, x satisfies 0 ≤ x < 2, and in one embodiment satisfies 0 ≤ x ≤ 1.5, and in another embodiment satisfies 0 ≤ x ≤ 1.0. 6-y is a number that can be changed such that the valence of the entire complex compound becomes 0 depending on the amounts and valencies of Ce, A, and B, and y satisfies 0 ≤ y ≤ 0.5x, and in one embodiment satisfies 0 ≤ y ≤ 0.2.

[0021] By ensuring that the amount of Ce, as well as the types and amounts of A and B, are as described above, sufficient oxygen storage capacity can be secured.

[0022] In one embodiment of the present invention, the novel composite oxide is Ce2TiO6, Ce2Ti 0.9 Si 0.1 O6, Ce2Ti 0.8 Si 0.2 O6, Ce 1.5 Y 0.5 TiO 5.75 CeYTiO 5.5 Ce 0.5 Y 1.5 TiO 5.25 Ce 1.5 La 0.5 TiO 5.75 CeLaTiO 5.5 Ce 0.5 La 1.5 TiO 5.25 Ce 1.5 Pr 0.5 TiO 5.75 , or Ce 1.5 Sm 0.5 TiO 5.75 That is the case.

[0023] Furthermore, one aspect of the present invention relates to the general formula Ce 2-w-x’ A w A' x’ B 1-y’-z B' y’ B'' z O 6-w / 2-x’-z This invention relates to a composite oxide having a composition represented by [the given formula], and an oxygen storage material containing the same.

[0024] General formula Ce 2-w-x’ Aw A' x’ B 1-y’-z B' y’ B'' z O 6-w / 2-x’-z A composite oxide having the composition represented by (hereinafter also referred to as "further novel composite oxides," which includes novel composite oxides) is obtained in an oxidized state, and the definitions of Ce, A, B, and O are the same as those described for novel composite oxides, while A', B', and B'', as well as x', y', z, and w are as follows.

[0025] A' is an alkaline earth metal element. In one embodiment, A' is one or more elements selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). In one embodiment, A is one or more elements selected from the group consisting of Ca and Sr. In one embodiment, A' includes Ca or Sr. If A' consists of two or more elements, the ratio is not limited. In one embodiment, A' is Ca and Sr, and their molar ratio is usually 95:5 to 5:95, and in one embodiment, 90:10 to 10:90. In one embodiment, A' is Ca or Sr. In one embodiment, A' is Ca. In one embodiment, A' is Sr. The valence of A' is usually divalent.

[0026] B' is one or more elements selected from the group consisting of Group 13 elements. In one embodiment, B' is one or more elements selected from the group consisting of boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). In one embodiment, B' is one or more elements selected from the group consisting of Al and Ga. In one embodiment, B' includes Al or Ga. If B' consists of two or more elements, the ratio is not limited. In one embodiment, B' is Al and Ga, with a molar ratio of typically 95:5 to 5:95, and in one embodiment, 90:10 to 10:90. In one embodiment, B' is Al or Ga. In one embodiment, B' is Al. In one embodiment, B' is Ga. The valency of B' is usually trivalent.

[0027] B'' is one or more elements selected from the group consisting of Group 12 elements. In one embodiment, B'' is one or more elements selected from the group consisting of zinc (Zn), cadmium (Cd), and mercury (Hg). In one embodiment, B'' is one or more elements selected from the group consisting of Zn and Cd. In one embodiment, B'' includes Zn. When B'' consists of two or more elements, their ratio is not limited. In one embodiment, B'' is Zn and Cd, and their molar ratio is usually 95:5 to 75:25, and in one embodiment, 90:10 to 80:20. In one embodiment, B'' is Zn. The valence of B'' is usually divalent.

[0028] 2 - w - x', w, x', 1 - y' - z, y', z, and 6 - w / 2 - x' - z are, respectively, the molar ratios of Ce, A, A', B, B', B'', and O when B + B' + B'' is taken as 1. Here, w satisfies 0 ≤ w < 2. x' satisfies 0 ≤ x' < 0.5. y' satisfies 0 ≤ y' ≤ 1. z satisfies 0 ≤ z ≤ 0.5. w + x' satisfies 0 ≤ w + x' < 2. y' + z satisfies 0 ≤ y' + z ≤ 1. w + x' + y' + z satisfies 0 ≤ w + x' + y' + z, and in one embodiment, 0 < w + x' + y' + z. 1 - y' - z satisfies 0 ≤ 1 - y' - z in one embodiment and 0 < 1 - y' - z in one embodiment. 6 - w / 2 - x' - z is a number that can vary such that the valence of the entire composite compound becomes 0 depending on the amounts and valences of Ce, A, A', B, B', and B''.

[0029] By having the amount of Ce and the types and amounts of A, A', B, B', and B'' as described above, sufficient oxygen storage capacity can be ensured.

[0030] In one aspect of the present invention, a further novel composite oxide is Ce2Ti 0.9 Al 0.1 O 5.95 , Ce2Ti 0.8 Al 0.2 O 5.9 , Ce2Ti 0.9 Zn 0.1 O 5.9 , Ce2Ti 0.8 Zn 0.2 O 5.8 , Ce2Ti 0.9 Ga 0.1 O 5.95 , Ce2Ti 0.8 Ga 0.2 O 5.9 , Ce2Ti 0.5 Ga 0.5 O 5.75 , Ce 1.5 Y 0.5 Ti 0.5 Al 0.5 O 5.5 , Ce 1.5 Yb 0.5 Ti 0.5 Al 0.5 O 5.5CeYAlO5, Ce 1.5 Y 0.5 TiO 5.75 Ce 1.5 La 0.5 TiO 5.75 Ce 1.5 Pr 0.5 TiO 5.75 Ce 1.5 Sm 0.5 TiO 5.75 Ce 1.5 EU 0.5 TiO 5.75 Ce 1.5 Yb 0.5 TiO 5.75 Ce2Ti 0.9 Al 0.1 O 5.95 Ce2Ti 0.9 Ga 0.1 O 5.95 Ce 1.9 Ca 0.1 TiO 5.9 Ce 1.9 Sr 0.1 TiO 5.9 That is the case.

[0031] In one embodiment of the present invention, the Ti of Ce2TiO6 4+ Al 3+ By substituting with low-valence cations such as O 2- Introducing a missing value can yield the following effects: (1)O 2- Conductivity is improved, and oxygen storage capacity at low temperatures increases. (2) As the formula weight becomes smaller relative to the Ce content, the oxygen storage capacity per unit mass increases. (3) Ease of reduction and O 2- Conductivity is improved, and a Ce2TiO6-type structure can be formed even at low firing temperatures (1,000°C).

[0032] In one embodiment of the present invention, the crystal structures of the novel composite oxide and further novel composite oxides can be determined by X-ray diffraction (XRD) analysis.

[0033] In the novel composite oxide, in the X-ray diffraction pattern measured using CuKα as the X-ray source, with a 2θ range of 5deg.(°) to 90deg., the angle of the maximum X-ray diffraction peak showing the highest intensity is within the range of 2θ to 31deg. Furthermore, in the X-ray diffraction pattern of the novel composite oxide, the peak intensity of the maximum X-ray diffraction peak is I a Let I be the maximum peak intensity among the X-ray diffraction peaks where 2θ is in the range of 32deg. to 36deg. b When that happens, I b / I a is 0.15≦I b / I a It satisfies ≤ 0.85.

[0034] In the novel composite oxides and further novel composite oxides, in the X-ray diffraction patterns measured using CuKα as the X-ray source with a 2θ range of 5deg.(°) to 90deg., the angle of the maximum X-ray diffraction peak showing the highest intensity is within the range of 2θ to 31deg. Furthermore, in the X-ray diffraction patterns of the novel composite oxides and further novel composite oxides, the peak intensity of the said maximum X-ray diffraction peak is I a Let I be the maximum peak intensity among the X-ray diffraction peaks where 2θ is in the range of 32deg. to 37deg. b When that happens, I b / I a is 0.15≦I b / I a It satisfies ≤ 0.85.

[0035] In the X-ray diffraction pattern measured using CuKα as the X-ray source for the novel composite oxide, if the novel composite oxide is, for example, Ce2TiO6, the peak appears at at least one of the following positions where 2θ is 23.3°±0.5°, 24.9°±0.5°, 29.1°±0.5°, 29.6°±0.5°, 30.5°±0.5°, 33.5°±0.5°, and 35.0°±0.5°. In one embodiment, it appears at at least two, in one embodiment at least three, in one embodiment at least four, in one embodiment at least five, in one embodiment at least six, and in one embodiment all seven. Note that the peak positions (2θ) listed above are characteristic of Ce2TiO6, which is one embodiment of the present invention, and one or more additional peaks may appear at positions (2θ) other than those listed above.

[0036] In the X-ray diffraction pattern of the novel composite oxide measured using CuKα as the X-ray source, the novel composite oxide was found to be, for example, Ce 1.5 Y 0.5 TiO 5.75 In this case, the peak appears at at least one of the positions where 2θ is 23.3°±0.5°, 25.1°±0.5°, 29.4°±0.5°, 30.4°±0.5°, 33.6°±0.5°, and 34.8°±0.5°, and in one embodiment it appears at at least two, in one embodiment at least three, in one embodiment at least four, in one embodiment at least five, and in one embodiment it appears at all six. Note that the peak positions (2θ) listed above are Ce in one embodiment of the present invention. 1.5 Y 0.5 TiO 5.75 This is characteristic of the region, and one or more additional peaks may appear at positions other than those mentioned above (2θ).

[0037] Furthermore, in the crystal structure obtained by X-ray diffraction after heating the novel composite oxide in air at 500°C for 6 hours, when the space group is Pnma and the Z value is 4, the lattice constants a, b, and c and the lattice volume V are 10.1 Å ≤ a ≤ 11.1 Å, 3.68 Å ≤ b ≤ 3.97 Å, 10.7 Å ≤ c ≤ 11.6 Å, and 419 Å, respectively. 3 ≤V ≤ 480Å3 (However, the values ​​between the lattice constants a, b, and c may be interchangeable.)

[0038] Furthermore, in the crystal structures of the novel composite oxide and further novel composite oxides, which were determined by X-ray diffraction after heating in air at 500°C for 6 hours, when the space group is Pnma and the Z value is 4, the lattice constants a, b, and c and the lattice volume V are, respectively, 10.1 Å ≤ a ≤ 11.1 Å, 3.64 Å ≤ b ≤ 3.97 Å, 10.5 Å ≤ c ≤ 11.7 Å, and 412 Å. 3 ≤V ≤ 480Å 3 (However, the values ​​between the lattice constants a, b, and c may be interchangeable.)

[0039] A novel composite oxide according to one aspect of the present invention has a novel crystal structure having the XRD pattern described above, and is also referred to as a Ce2TiO6 type crystal structure in this specification. Furthermore, another novel composite oxide according to one aspect of the present invention also has a Ce2TiO6 type crystal structure.

[0040] Furthermore, the XRD spectrum of the Ce2TiO6 type crystal structure may change its peak position depending on the composition of the novel composite oxide and further novel composite oxides. This is a matter known in the art.

[0041] The novel composite oxide and further novel composite oxide in one aspect of the present invention represent the oxidation state as described above, but in the usage mode, they exhibit oxygen storage characteristics by repeatedly changing between the oxidation state and the reduction state. The reduction state of the novel composite oxide in one aspect of the present invention is, for example, the general formula Ce 2-x A x BO 6-y-δ This is expressed as follows, where Ce, A, B, and O, as well as x and y, are as described above, but Ce includes trivalent Ce, and δ can vary depending on the degree of reduction, but usually satisfies 0 ≤ δ ≤ 1. Furthermore, the reduction state of a further novel composite oxide in one aspect of the present invention is, for example, the general formula Ce 2-w-x’ A w A' x’ B 1-y’-z B' y’B'' z O 6-w / 2-x’-z-δ This is expressed as follows, where Ce, A, A', B, B', B'', and O, as well as w, x', y', and z, are as described above, but Ce includes trivalent Ce, and δ can vary depending on the degree of reduction, but usually satisfies 0 ≤ δ ≤ 1.

[0042] Figure 1 shows La2TiO5 having a Y2TiO5 type crystal structure (Figure 1A), along with the crystal structure of Ce2TiO6, a novel composite oxide in one aspect of the present invention (Figure 1B), and Ce2TiO6 type Ce2Ti, a further novel composite oxide in one aspect of the present invention. 0.8 Al 0.2 O 5.9 The crystal structure (Figure 1C) is schematically shown. From Figure 1B, the novel composite oxide has tetravalent cerium ions (Ce) in its oxidized state. 4+ ) and tetravalent titanium ions (Ti 4+ ) contains and Y2TiO5 type (La2TiO5) oxide ions (O 2- It has a new crystal structure (Ce2TiO6 type) that incorporates ). The new composite oxide exhibits Ce in a reducing atmosphere. 4+ Ce 3+ The change to O 2- It is thought that the elimination of tetravalent titanium ions (Ti) occurs simultaneously, and as the crystal structure approaches that of Y2TiO5, oxygen is released. From Figure 1C, the tetravalent titanium ions (Ti) of Ce2TiO6 4+ ) aluminum ions (Al 3+ ) Substitution with oxide ions (O 2- ) A defect was introduced to the site Ce2Ti 0.8 Al 0.2 O 5.9 O 2- Conductivity is improved and oxygen storage capacity at low temperatures (300°C) increases. Furthermore, by substituting the Ti in Ce2TiO6 with the lighter element Al, O 2- With the introduction of the defect, Ce2Ti 0.8 Al 0.2 O 5.9 The formula weight of becomes smaller, and the maximum oxygen storage capacity (oxygen storage capacity per unit mass) at high temperatures (>400°C) also increases. In addition, Ce of Ce2TiO6 4+ to Y3+ Ya La 3+ to, or Ti 4+ Al 3+ Ya Ga 3+ Substituting with O, the charge compensation is O 2- A missing part was introduced to the site, O 2- Conductivity is improved, and a Ce2TiO6-type structure can be formed even at low firing temperatures (1,000°C).

[0043] Accordingly, one aspect of the present invention relates to an oxygen storage material comprising a novel composite oxide and / or further novel composite oxide according to one aspect of the present invention.

[0044] An oxygen storage material according to one aspect of the present invention may further contain a catalytic metal. The catalytic metal may be supported on the novel composite oxide and / or further novel composite oxide described above. Examples of catalytic metals include noble metals. Examples of noble metals include, but are not limited to, platinum group noble metals. Examples of platinum group noble metals include ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). In one embodiment, the noble metal is one or more selected from the group consisting of Rh, Pt, and Pd. The amount of noble metal supported is the same as that of conventional exhaust gas purification catalysts and is not limited to, but is usually 0.01% to 5% by weight of the total weight of the oxygen storage material, and in one embodiment is 0.5% to 2% by weight.

[0045] An oxygen storage material according to one aspect of the present invention exhibits excellent oxygen release at low temperatures. Therefore, one aspect of the present invention also relates to an exhaust gas purification catalyst and / or oxidation-reduction catalyst containing the oxygen storage material according to one aspect of the present invention.

[0046] An exhaust gas purification catalyst and / or oxidation-reduction catalyst according to one aspect of the present invention may contain a carrier material other than the oxygen storage material according to one aspect of the present invention. Examples of carrier materials other than the oxygen storage material according to one aspect of the present invention include porous metal oxides with excellent heat resistance, such as aluminum oxide (alumina: Al2O3), zirconium oxide (zirconia: ZrO2), silicon oxide (silica: SiO2), or composite oxides mainly composed of these metal oxides. In the exhaust gas purification catalyst, conventional support methods such as adsorption support and water absorption support can be used.

[0047] An exhaust gas purification catalyst and / or oxidation-reduction catalyst according to one aspect of the present invention can exhibit excellent ordered structure durability and OSC (Oxidation-Scaling) ability over a wide temperature range. An exhaust gas purification catalyst according to one aspect of the present invention is typically used in a low temperature range of approximately 200°C to 600°C.

[0048] Furthermore, in an oxygen storage material according to one aspect of the present invention, by utilizing the properties of oxygen absorption and release, and the properties that the energy states of the oxygen-adsorbing state and the oxygen-releasing state are different, it is possible to store oxygen (oxygen storage method), enrich oxygen (oxygen enrichment method), remove oxygen (oxygen removal method), and / or heat and / or cool (heating and cooling method) using the oxygen storage material according to one aspect of the present invention.

[0049] In one embodiment of the present invention, novel composite oxides and further novel composite oxides can be produced by conventional methods in the art, such as solid-phase methods, liquid-phase methods, alkoxide methods, etc., except that the calcination is carried out under a reducing atmosphere.

[0050] In one embodiment of the present invention, a novel complex oxide is produced by mixing an aqueous solution of a cerium compound, a titanium compound and / or a compound containing a Group 14 element, and optionally a compound containing elements other than Ce and Ti as described above (hereinafter also referred to as "cerium compound, etc.") with an aqueous solution of a complex-forming agent, drying the mixture to precipitate a product containing Ce and Ti, etc., and then calcining it in a reducing atmosphere. The cerium compound, etc. can also be used as a non-aqueous solvent, such as an alcohol or an organic carboxylic acid ester solution.

[0051] Examples of cerium compounds that can be used include water-soluble compounds such as nitrates (cerium nitrate, cerium diammonium nitrate, etc.), sulfates (cerium sulfate, etc.), chlorides (cerium chloride, etc.), and compounds soluble in alcohols or organic solvents such as alkoxides (cerium isopropoxide, etc.).

[0052] As silicon compounds, alkoxides such as tetraethyl orthosilicate and tetraisopropyl orthosilicate can be used.

[0053] Examples of titanium compounds that can be used include alkoxides such as titanium(IV) tetraisopropoxide, dihydroxybis(ammonium lactato)titanium(IV), titanium(IV) oxysulfate, and titanium(IV) sulfate.

[0054] Compounds containing elements other than Ce and Ti include water-soluble or alcohol-soluble compounds such as nitrates, sulfates, chlorides, and alkoxides.

[0055] The complexing agent is not particularly limited and can include, for example, polycarboxylic acids, polyhydric alcohols, and amino acids. Examples of polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, citric acid, tartaric acid, and malic acid. In one embodiment, the complexing agent is citric acid. Examples of polyhydric alcohols include ethylene glycol, glycerin, propylene glycol, and butylene glycol. In one embodiment, the complexing agent is ethylene glycol. Examples of amino acids include glycine, alanine, asparagine, and aspartic acid.

[0056] If a precipitate forms when an aqueous solution of a cerium compound or the like is mixed with an aqueous solution of a complexing agent, this precipitate may be filtered and then dried.

[0057] The mixed solution of an aqueous solution of a cerium compound or the like and an aqueous solution of a complexing agent can usually be dried at 50°C to 150°C for 5 to 48 hours. Furthermore, the product containing Ce and Ti obtained by drying may be calcined in air at 400°C to 600°C, for example 500°C, for 4 to 8 hours, for example 6 hours.

[0058] The calcination of products containing Ce and Ti can be carried out by heating and holding them in a reducing atmosphere, usually at 600°C to 1500°C, for usually 2 to 48 hours. The reducing atmosphere can be an inert gas atmosphere, a non-oxidizing atmosphere, or an atmosphere containing a reducing agent. In one embodiment, it can be an atmosphere containing a reducing gas such as H2 or CO, or an atmosphere containing carbon, such as activated carbon, or an enclosed atmosphere. This yields a novel composite oxide having a Ce2TiO6 type crystal structure.

[0059] In the case of a further method for producing a novel complex oxide according to one aspect of the present invention, the method is the same as the method for producing a novel complex oxide according to one aspect of the present invention, except that a compound containing the elements included in the further novel complex oxide is used. In the method for producing a further novel complex oxide, the compound containing A', B', or B'' is not particularly limited, and for example, water-soluble compounds such as nitrates, sulfates, chlorides, and alkoxides, or compounds soluble in alcohols or organic solvents can be used. [Examples]

[0060] The following describes several embodiments relating to one aspect of the present invention, but it is not intended that the embodiments of the present invention are limited to those shown in these embodiments.

[0061] 1. Manufacturing of oxygen storage materials containing novel composite oxides 1-1. Reagents • Cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O) (manufactured by Nacalai Tesque Co., Ltd.) ≥ 35.0% by weight (as CeO2) • Yttrium(III) nitrate hexahydrate (Y(NO3)3·6H2O) (manufactured by Kanto Chemical Co., Ltd.) > 99.99% by weight Lanthanum(III) nitrate hexahydrate (La(NO3)3·6H2O) (manufactured by Nacalai Tesque Co., Ltd.) ≥ 99.9% by weight • Praseodymium(III) nitrate hexahydrate (Pr(NO3)3·6H2O) (manufactured by Kanto Chemical Co., Ltd.) > 99.95% by weight • Samarium(III) nitrate hexahydrate (Sm(NO3)3·6H2O) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 99.5% by weight ·Europium(III) nitrate hexahydrate (Eu(NO3)2·6H2O) (manufactured by Kanto Kagaku Co., Ltd.)>99.95% by weight Ytterbium(III) nitrate pentahydrate (Yb(NO3)3·5H2O) (Sigma-Aldrich) 99.9% by weight Titanium(IV) tetraisopropoxide (Ti(iPrO)4) (manufactured by Kanto Chemical Co., Ltd.) > 97.0% by weight • Dihydroxybis(ammonium lactato)titanium(IV) ((NH4)2Ti(OH)2(Lac)2) (manufactured by Tokyo Chemical Industry Co., Ltd.) Approximately 40% by weight aqueous solution of isopropyl alcohol Aluminum nitrate notahydrate (Al(NO3)3·9H2O) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 98.0% by weight • Tetraethyl orthosilicate (Si(EtO)4) (manufactured by Tokyo Chemical Industry Co., Ltd.) > 98.0% by weight • Zinc nitrate hexahydrate (Zn(NO3)2·6H2O) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 99.0% by weight • Gallium nitrate octahydrate (Ga(NO3)3·8H2O) (manufactured by Taiyo Co., Ltd.) 99% by weight Calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 98.5% by weight Strontium nitrate (Sr(NO3)2) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 98.0-102.0% by weight • Zirconium nitrate dihydrate (ZrO(NO3)2·2H2O) (manufactured by Kanto Chemical Co., Ltd.) > 99.0% by weight • Citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 98.0% by weight • Ethylene glycol (manufactured by Nacalai Tesque Co., Ltd.) 99.5% by weight • 28% Ammonia Water (Fujifilm Wako Pure Chemical Industries, Ltd.) 25.0%~30.0% by weight Palladium(II) nitrate (Pd(NO3)2) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 97.0% by weight

[0062] 1-2. Manufacturing of complex oxides Example 1 (1) A stirring bar was placed in a 1,000 mL glass beaker, and Ce(NO3)3·6H2O (7.24 g, 16.7 mmol), Ti(iPrO)4 (2.37 g, 8.33 mmol) were added as raw materials, citric acid (19.2 g, 100 mmol), ethylene glycol (6.21 g, 100 mmol) as additives, and ethanol (100 mL) as a solvent. (2) The solution was heated and evaporated to dryness while being stirred with a hot stirrer. (3) The contents were collected, the stirring bar was removed, and the mixture was crushed and mixed in a mortar. (4) The powder was transferred to an alumina crucible and calcined in a muffle furnace at 500°C in air for 6 hours to recover the precursor. (5) The precursor (0.3g) was mixed with activated carbon pellets (0.3g), added to an alumina crucible, placed the alumina crucible inside an alumina rectangular container, covered with an excess of activated carbon pellets, covered with an alumina plate, and calcined in air at 1150°C for 16 hours. (6) The mixture of powder and activated carbon pellets was sieved to remove the larger activated carbon pellets, and the product was recovered.

[0063] Comparative Example 1 The product was recovered in the same manner as in Example 1, except that the raw material was changed to Ce(NO3)3·6H2O (10.9g, 25.0 mmol).

[0064] Comparative Example 2 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (5.43g, 12.5 mmol) and Ti(iPrO)4 (3.55g, 12.5 mmol).

[0065] Comparative Example 3 (1) A stirring bar was placed in a 1,000 mL glass beaker, and Ce(NO3)3·6H2O (8.68 g, 20.0 mmol) and ZrO(NO3)2·6H2O (5.35 g, 20.0 mmol) were added as raw materials, and distilled water (100 mL) was added as a solvent. The mixture was stirred and dissolved. (2) Dilute 28% aqueous ammonia (32 mL) with distilled water (900 mL), add the solution from (1), and continue stirring at room temperature overnight. (3) The obtained solution and precipitate were transferred to a centrifuge tube and centrifuged at 3,000 rpm for 5 minutes, and the supernatant was removed. (4) Distilled water (500 mL) was added to the obtained precipitate to redisperse it, and the centrifugation process was repeated twice to wash it. (5) The obtained precipitate was calcined in air at 250°C for 2 hours and then crushed in a mortar. (6) The obtained powder was calcined in air at 800°C for 5 hours, and the resulting powder was compacted into a 2t mass. (7) Molded body 5L·min -1 The product was recovered after calcination at 1400°C for 5 hours under a 10% H2 / N2 airflow.

[0066] Comparative Example 4 (1) A stirring bar was placed in a 1,000 mL glass beaker, and Ce(NO3)3·6H2O (10.9 g, 25.0 mmol) was added as raw material, citric acid (19.2 g, 100 mmol) and ethylene glycol (6.21 g, 100 mmol) as additives, and ethanol (100 mL) as a solvent. (2) The solution was heated and evaporated to dryness while being stirred with a hot stirrer. (3) The contents were collected, the stirring bar was removed, and the mixture was crushed and mixed in a mortar. (4) The powder was transferred to an alumina crucible and calcined in a muffle furnace at 500°C in air for 6 hours to recover the precursor. (5) The precursor (0.3g) was added to an alumina crucible and calcined in air at 1150°C for 16 hours, and the product was recovered.

[0067] Comparative Example 5 The product was recovered in the same manner as in Comparative Example 4, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24g, 16.7mmol) and Ti(iPrO)4 (2.37g, 8.33mmol).

[0068] Comparative Example 6 The product was recovered in the same manner as in Comparative Example 4, except that the raw materials were changed to Ce(NO3)3·6H2O (5.43g, 12.5 mmol) and Ti(iPrO)4 (3.55g, 12.5 mmol).

[0069] Comparative Example 7 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to La(NO3)3·6H2O (7.22g, 16.7mmol) and Ti(iPrO)4 (2.37g, 8.33mmol).

[0070] Comparative Example 8 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Pr(NO3)3·6H2O (7.25g, 16.7mmol) and Ti(iPrO)4 (2.37g, 8.33mmol).

[0071] Example 2 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (5.43g, 12.5 mmol), Y(NO3)3·6H2O (1.60g, 4.17 mmol), and Ti(iPrO)4 (2.37g, 8.33 mmol).

[0072] Example 3 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (5.43g, 12.5 mmol), La(NO3)3·6H2O (1.80g, 4.17 mmol), and Ti(iPrO)4 (2.37g, 8.33 mmol).

[0073] Example 4 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (5.43g, 12.5 mmol), Pr(NO3)3·6H2O (1.81g, 4.17 mmol), and Ti(iPrO)4 (2.37g, 8.33 mmol).

[0074] Example 5 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (5.43g, 12.5 mmol), Sm(NO3)3·6H2O (1.81g, 4.17 mmol), and Ti(iPrO)4 (2.37g, 8.33 mmol).

[0075] Example 6 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24g, 16.7mmol), Ti(iPrO)4 (2.13g, 7.50mmol), and Si(EtO)4 (0.174g, 0.833mmol).

[0076] Example 7 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24 g, 16.7 mmol), Ti(iPrO)4 (1.89 g, 6.67 mmol), and Si(EtO)4 (0.347 g, 1.67 mmol).

[0077] Comparative Example 9 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24 g, 16.7 mmol), Ti(iPrO)4 (1.18 g, 4.17 mmol), and Si(EtO)4 (0.868 g, 4.17 mmol).

[0078] Example 8 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (3.62 g, 8.33 mmol), Y(NO3)3·6H2O (3.19 g, 8.33 mmol), and Ti(iPrO)4 (2.37 g, 8.33 mmol).

[0079] Example 9 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (3.62 g, 8.33 mmol), La(NO3)3·6H2O (3.61 g, 8.33 mmol), and Ti(iPrO)4 (2.37 g, 8.33 mmol).

[0080] Example 10 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (1.81 g, 4.17 mmol), Y(NO3)3·6H2O (4.79 g, 12.5 mmol), and Ti(iPrO)4 (2.37 g, 8.33 mmol).

[0081] Example 11 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (1.81 g, 4.17 mmol), La(NO3)3·6H2O (5.41 g, 12.5 mmol), and Ti(iPrO)4 (2.37 g, 8.33 mmol).

[0082] Example 12 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24 g, 16.7 mmol), Ti(iPrO)4 (2.13 g, 7.50 mmol), and Al(NO3)3·9H2O (0.313 g, 0.833 mmol).

[0083] Example 13 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24 g, 16.7 mmol), Ti(iPrO)4 (1.89 g, 6.67 mmol), and Al(NO3)3·9H2O (0.625 g, 1.67 mmol).

[0084] Comparative Example 11 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24 g, 16.7 mmol), Ti(iPrO)4 (1.18 g, 4.17 mmol), and Al(NO3)3·9H2O (1.56 g, 4.17 mmol).

[0085] Example 14 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24 g, 16.7 mmol), (NH4)2Ti(OH)2(Lac)2 (4.43 g, 7.50 mmol), and Zn(NO3)2·6H2O (0.297 g, 1.00 mmol), and the firing temperature was changed to 1,075 °C. Since ZnO is volatile under a reducing atmosphere and at high temperatures, Zn was made 20 mol% excessive in the composition of the raw materials.

[0086] Example 15 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24g, 16.7 mmol), (NH4)2Ti(OH)2(Lac)2 (3.94g, 6.67 mmol), and Zn(NO3)2·6H2O (0.595g, 2.00 mmol), and the calcination temperature was changed to 1,075°C. Since Zn oxide is volatile in a reducing atmosphere and at high temperatures, the composition of the raw materials was increased by 20 mol% in excess of Zn.

[0087] Comparative Example 12 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24g, 16.7 mmol), (NH4)2Ti(OH)2(Lac)2 (2.46g, 4.17 mmol), and Zn(NO3)2·6H2O (1.49g, 5.00 mmol), and the calcination temperature was changed to 1,075°C. Since Zn oxide is volatile in a reducing atmosphere and at high temperatures, the composition of the raw materials was increased by 20 mol% in excess of Zn.

[0088] Example 16 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24g, 16.7mmol), (NH4)2Ti(OH)2(Lac)2 (4.43g, 7.50mmol), and Ga(NO3)3·8H2O (0.350g, 0.875mmol), and the calcination temperature was changed to 1,000°C. Since Ga oxide is volatile in a reducing atmosphere and at high temperatures, the composition of the raw materials was increased by 5 mol% in excess Ga.

[0089] Example 17 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24g, 16.7 mmol), (NH4)2Ti(OH)2(Lac)2 (3.94g, 6.67 mmol), and Ga(NO3)3·8H2O (0.700g, 1.75 mmol), and the calcination temperature was changed to 1,000°C. Since Ga oxide is volatile in a reducing atmosphere and at high temperatures, the composition of the raw materials was increased by 5 mol% in excess Ga.

[0090] Example 18 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24g, 16.7mmol), (NH4)2Ti(OH)2(Lac)2 (2.46g, 4.17mmol), and Ga(NO3)3·8H2O (1.75g, 4.38mmol), and the calcination temperature was changed to 1,075°C. Since Ga oxide is volatile in a reducing atmosphere and at high temperatures, the composition of the raw materials was increased by 5 mol% in excess Ga.

[0091] Example 19 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (5.42g, 12.5 mmol), Y(NO3)3·6H2O (1.60g, 4.17 mmol), (NH4)2Ti(OH)2(Lac)2 (2.46g, 4.17 mmol), and Al(NO3)3·9H2O (1.56g, 4.17 mmol).

[0092] Example 20 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (5.42g, 12.5 mmol), Yb(NO3)3·5H2O (1.87g, 4.17 mmol), (NH4)2Ti(OH)2(Lac)2 (2.46g, 4.17 mmol), and Al(NO3)3·9H2O (1.56g, 4.17 mmol).

[0093] Example 21 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (3.62g, 8.33mmol), Y(NO3)3·6H2O (3.19g, 8.33mmol), and Al(NO3)3·9H2O (3.13g, 8.33mmol).

[0094] Comparative Example 13 The product was recovered in the same manner as in Example 1, except that the firing temperature was changed to 1,000°C.

[0095] Example 22 The raw materials were changed to Ce(NO3)3·6H2O (5.43 g, 12.5 mmol), Y(NO3)3·6H2O (1.60 g, 4.17 mmol), and Ti(iPrO)4 (2.37 g, 8.33 mmol). The product was recovered in the same manner as in Example 1 except that the firing temperature was changed to 1,000 °C.

[0096] Example 23 The raw materials were changed to Ce(NO3)3·6H2O (5.43 g, 12.5 mmol), La(NO3)3·6H2O (1.80 g, 4.17 mmol), and Ti(iPrO)4 (2.37 g, 8.33 mmol). The product was recovered in the same manner as in Example 1 except that the firing temperature was changed to 1,000 °C.

[0097] Example 24 The raw materials were changed to Ce(NO3)3·6H2O (5.43 g, 12.5 mmol), Pr(NO3)3·6H2O (1.81 g, 4.17 mmol), and Ti(iPrO)4 (2.37 g, 8.33 mmol). The product was recovered in the same manner as in Example 1 except that the firing temperature was changed to 1,000 °C.

[0098] Example 25 The raw materials were changed to Ce(NO3)3·6H2O (5.43 g, 12.5 mmol), Sm(NO3)3·6H2O (1.81 g, 4.17 mmol), and Ti(iPrO)4 (2.37 g, 8.33 mmol). The product was recovered in the same manner as in Example 1 except that the firing temperature was changed to 1,000 °C.

[0099] Example 26 The raw materials were changed to Ce(NO3)3·6H2O (5.43 g, 12.5 mmol), Eu(NO3)3·6H2O (1.86 g, 4.17 mmol), and Ti(iPrO)4 (2.37 g, 8.33 mmol). The product was recovered in the same manner as in Example 1 except that the firing temperature was changed to 1,000 °C.

[0100] Example 27 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (5.43g, 12.5 mmol), Yb(NO3)3·5H2O (1.87g, 4.17 mmol), and Ti(iPrO)4 (2.37g, 8.33 mmol), and the calcination temperature was changed to 1,000°C.

[0101] Example 28 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24g, 16.7mmol), Ti(iPrO)4 (2.13g, 7.50mmol), and Al(NO3)3·9H2O (0.313g, 0.833mmol), and the calcination temperature was changed to 1,000°C.

[0102] Example 29 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (7.24g, 16.7mmol), (NH4)2Ti(OH)2(Lac)2 (4.43g, 7.50mmol), and Ga(NO3)3·8H2O (0.350g, 0.875mmol), and the calcination temperature was changed to 1,000°C. Since Ga oxide is volatile in a reducing atmosphere and at high temperatures, the composition of the raw materials was increased by 5 mol% in excess Ga.

[0103] Example 30 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (6.88g, 15.8mmol), Ca(NO3)2·4H2O (0.197g, 0.833mmol), and (NH4)2Ti(OH)2(Lac)2 (4.92g, 8.33mmol).

[0104] Example 31 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (6.88g, 15.8mmol), Sr(NO3)2 (0.176g, 0.833mmol), and (NH4)2Ti(OH)2(Lac)2 (4.92g, 8.33mmol).

[0105] Comparative Example 10 The product was recovered in the same manner as in Example 1, except that the raw materials were changed to Ce(NO3)3·6H2O (5.43g, 12.5 mmol), Sr(NO3)2 (0.882g, 4.17 mmol), and (NH4)2Ti(OH)2(Lac)2 (4.92g, 8.33 mmol).

[0106] 2. Analysis and evaluation of the product 2-1. X-ray diffraction measurement (confirmation of the crystal structure of the product) X-ray diffraction (XRD) measurements were performed on the products of Examples 1-31 and Comparative Examples 1-13. The measurement equipment and conditions are shown below. • Measuring device: RINT RAPID II (manufactured by Rigaku Corporation) Measurement conditions: Voltage 50V, Current 100mA, Collimator diameter φ0.3mm, Sample angle ω15°

[0107] Figure 2A shows the X-ray diffraction patterns of the products of Example 1 and Comparative Examples 1-3. For Ce2TiO6, fluorite-type CeO2, layered perovskite-type Ce2Ti2O7, and pyrochlore-type Ce2Zr2O7, the X-ray diffraction patterns predicted from the crystal structure were calculated and compared with the X-ray diffraction patterns of each product.

[0108] Figure 2B shows the X-ray diffraction patterns of the products of Example 1 and Comparative Examples 4-6. For Ce2TiO6, fluorite-type CeO2, and rutile-type TiO2, the X-ray diffraction patterns predicted from the crystal structure were calculated and compared with the X-ray diffraction patterns of each product.

[0109] From Figures 2A and 2B, the following was found: The product of Example 1 was Ce2TiO6 of the Ce2TiO6 type. The precursor was calcined in air at 500°C, and Ce 4+ and Tire 4+ It is thought to be an oxide containing Ce 4+ and Ti 4+ By calcining a precursor containing in a reducing atmosphere, at least a portion of Ce is converted to Ce 3+ La2TiO5 3+ to Ce 3+Ce2TiO5 is produced by substitution with Ce. When the activated carbon stops burning during the cooling process after firing, the reducing atmosphere is gone, and Ce 3+ Ya Ti 4+ At temperatures where there is no movement, Ce2TiO5 reacts with atmospheric O2, causing Ce 3+ Ce is oxidized 4+ This results in the generation of Ce2TiO6.

[0110] The product of Comparative Example 1 was fluorite-type CeO2, and the product of Comparative Example 2 was layered perovskite-type Ce2Ti2O7. From these results, it was found that a Ce2TiO6-type crystal structure is generated by calcining a precursor containing Ce+A:B in a ratio of 2:1 as in the general formula mentioned above.

[0111] The product of Comparative Example 3 was pyrochlore-type Ce2Zr2O7. The molded body was calcined in air at 800°C, and Ce 4+ and Zr 4+ It is thought to be an oxide containing Ce 4+ and Zr 4+ By calcining a precursor containing in a reducing atmosphere, at least a portion of Ce is converted to Ce 3+ Ce 3+ and Zr 4+ As the difference in charge and ionic radius increases, Ce 3+ and Zr 4+ A more regular arrangement of these atoms leads to greater stability, resulting in the formation of the pyrochlore-type Ce2Zr2O7.

[0112] The product of Comparative Example 4 was fluorite-type CeO2, while the products of Comparative Examples 5 and 6 were mixtures of fluorite-type CeO2 and rutile-type TiO2. 4+ and Ti 4+ When a precursor containing Ce is calcined in air, 4+ Ti is not reduced. 4+ Along with this, the states of CeO2 and TiO2 become stable, and a mixture of CeO2 and TiO2 is obtained.

[0113] These results indicate that Ce2TiO6 must be produced by first firing it in a reducing atmosphere.

[0114] Figure 2C shows the X-ray diffraction patterns of the products of Examples 1 and 2 and Comparative Examples 7 and 8. Ce2TiO6, La2TiO5, Pr2TiO5, Ce2TiO6 type Ce 1.5 Y 0.5 TiO 5.75 For each product, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0115] Figure 2D shows the X-ray diffraction patterns of the products of Examples 1 and 3-5. Ce2TiO6, Ce2TiO6-type Ce 1.5 La 0.5 TiO 5.75 , Ce2TiO6 type Ce 1.5 Pr 0.5 TiO 5.75 , Ce2TiO6 type Ce 1.5 Sm 0.5 TiO 5.75 For each product, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0116] From Figures 2C and 2D, the following was found: The product of Comparative Example 7 was La2TiO5 of the Y2TiO5 type. The precursor was calcined in air at 500°C, La 3+ and Tire 4+ It is thought to be an oxide containing La 3+ and Ti 4+ La2TiO5 is produced by calcining a precursor containing [the specified substance].

[0117] The product of Comparative Example 8 was Pr2TiO5. The precursor was calcined in air at 500°C, and Pr 3+ or Pr 4+ and Ti 4+ It is thought to be an oxide containing Pr. 3+ or Pr 4+ and Ti 4+ By calcining a precursor containing in a reducing atmosphere, at least a portion of Pr is converted to Pr 3+ La2TiO5 3+ Pr 3+This generates Pr2TiO5 with substitution.

[0118] The product of Example 2 is Ce2TiO6 type Ce 1.5 Y 0.5 TiO 5.75 The product of Example 3 is of the Ce2TiO6 type. 1.5 La 0.5 TiO 5.75 The product of Example 4 is of the Ce2TiO6 type. 1.5 Pr 0.5 TiO 5.75 The product of Example 5 is of the Ce2TiO6 type. 1.5 Sm 0.5 TiO 5.75 It was possible to substitute Ce in Ce2TiO6 with rare earth metal elements other than Ce. 4+ When it is substituted with a trivalent rare earth metal ion, the amount of oxygen decreases as a charge compensation.

[0119] Figure 3A shows the X-ray diffraction patterns of the products of Examples 1, 6, and 7 and Comparative Example 9. Ce2TiO6, Ce2TiO6-type Ce2Ti 0.9 Si 0.1 O6, Ce2TiO6 type Ce2Ti 0.8 Si 0.2 O6, apatite-type Ce 9.33 Si6O 26 For fluorite-type CeO2, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0120] From Figure 3A, the following was found: The product of Example 6 is Ce2TiO6 type Ce2Ti 0.9 Si 0.1 The product is O6, and the product of Example 7 is Ce2Ti of the Ce2TiO6 type. 0.8 Si 0.2 The product of Comparative Example 9 is Ce2TiO6 type Ce2Ti 0.8 Si 0.2 O6 and apatite-type Ce 9.33 Si6O 26It was a mixture of fluorite-type CeO2. It is possible to substitute the Ti in Ce2TiO6 with other elements such as Si. As the amount of Si substitution increases, Ce2TiO6-type Ce2Ti 0.8 Si 0.2 O6 and apatite-type Ce 9.33 Si6O 26 A mixture of CeO2 is obtained.

[0121] Figure 3B shows the X-ray diffraction patterns of the products of Examples 1, 2, 8, and 10. Ce2TiO6, Ce2TiO6-type Ce 1.5 Y 0.5 TiO 5.75 Ce2TiO6 type CeYTiO 5.5 , Ce2TiO6 type Ce 0.5 Y 1.5 TiO 5.25 For each product, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0122] Figure 3C shows the X-ray diffraction patterns of the products of Examples 1, 3, 9, and 11. Ce2TiO6, Ce2TiO6-type Ce 1.5 La 0.5 TiO 5.75 Ce2TiO6 type CeLaTiO 5.5 , Ce2TiO6 type Ce 0.5 La 1.5 TiO 5.25 For each product, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0123] From Figures 3B and 3C, the following was found: The product of Example 8 is CeYTiO of the Ce2TiO6 type. 5.5 The product of Example 9 is of the Ce2TiO6 type CeLaTiO 5.5 The product of Example 10 is of the Ce2TiO6 type. 0.5 Y 1.5 TiO 5.25 The product of Example 11 is of the Ce2TiO6 type. 0.5 La 1.5 TiO 5.25In Ce2TiO6, the Ce can be replaced with any amount of rare earth metal elements other than Ce.

[0124] Table 1 shows the raw materials, calcination conditions, and phases contained in the obtained products for Examples 1-11 and Comparative Examples 1-9.

[0125] [Table 1]

[0126] Assuming that the products of Examples 1 to 11 have a Ce2TiO6-type structure, the space group is Pnma, and the lattice constants a, b, and c, as well as the lattice volume V, were determined when the Z value is 4. The results are shown in Table 2.

[0127] [Table 2]

[0128] Figure 7A shows the X-ray diffraction patterns of the products of Examples 1, 12, 13 and Comparative Example 11. Ce2TiO6, Ce2TiO6-type Ce2Ti 0.9 Al 0.1 O 5.95 , Ce2TiO6 type Ce2Ti 0.8 Al 0.2 O 5.9 For perovskite-type CeAlO3 and fluorite-type CeO2, the X-ray diffraction patterns predicted from the crystal structures were calculated and compared with the X-ray diffraction patterns of each product.

[0129] From Figure 7A, the following was found: The product of Example 12 is Ce2TiO6 type Ce2Ti 0.9 Al 0.1 O 5.95 The product of Example 13 is Ce2TiO6 type Ce2Ti 0.8 Al 0.2 O 5.9 Therefore, the product of Comparative Example 11 is of the Ce2TiO6 type. 0.8 Al 0.2 O 5.9It was a mixture of perovskite-type CeAlO3 and fluorite-type CeO2. It is possible to substitute the Ti in Ce2TiO6 with Al. Furthermore, as the amount of Al substitution increases, the Ce2TiO6 type Ce2Ti 0.8 Al 0.2 O 5.9 This yields a mixture of perovskite-type CeAlO3 and fluorite-type CeO2.

[0130] Figure 7B shows the X-ray diffraction patterns of the products of Examples 1, 14, 15 and Comparative Example 12. Ce2TiO6, Ce2TiO6-type Ce2Ti 0.9 Zn 0.1 O 5.9 , Ce2TiO6 type Ce2Ti 0.8 Zn 0.2 O 5.8 For fluorite-type CeO2, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0131] From Figure 7B, the following was found: The product of Example 14 is Ce2TiO6 type Ce2Ti 0.9 Zn 0.1 O 5.9 Therefore, the product of Example 15 is Ce2Ti of the Ce2TiO6 type. 0.8 Zn 0.2 O 5.8 Therefore, the product of Comparative Example 12 is of the Ce2TiO6 type. 0.8 Zn 0.2 O 5.8 It was a mixture of fluorite-type CeO2. It is possible to substitute Ti in Ce2TiO6 with Zn. Furthermore, as the amount of substitution with Zn increases, the Ce2TiO6 type Ce2Ti 0.8 Zn 0.2 O 5.8 A mixture of fluorite-type CeO2 is obtained.

[0132] Figure 7C shows the X-ray diffraction patterns of the products from Examples 1 and 16-18. Ce2TiO6, Ce2TiO6-type Ce2Ti 0.9 Ga 0.1 O 5.95 , Ce2TiO6 type Ce2Ti 0.8 Ga 0.2 O5.9 , Ce2TiO6 type Ce2Ti 0.5 Ga 0.5 O 5.75 For each product, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0133] From Figure 7C, the following was found: The product of Example 16 is Ce2TiO6 type Ce2Ti 0.9 Ga 0.1 O 5.95 Therefore, the product of Example 17 is of the Ce2TiO6 type. 0.8 Ga 0.2 O 5.9 Therefore, the product of Example 18 is of the Ce2TiO6 type. 0.5 Ga 0.5 O 5.75 It was possible to substitute Ti with Ga in Ce2TiO6.

[0134] Figure 7D shows the X-ray diffraction patterns of the products from Examples 1 and 19-21. Ce2TiO6, Ce2TiO6-type Ce 1.5 Y 0.5 Ti 0.5 Al 0.5 O 5.5 , Ce2TiO6 type Ce 1.5 Yb 0.5 Ti 0.5 Al 0.5 O 5.5 For Ce2TiO6-type CeYAlO5, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0135] From Figure 7D, the following was found: The product of Example 19 is Ce2TiO6 type Ce 1.5 Y 0.5 Ti 0.5 Al 0.5 O 5.5 The product of Example 20 is of the Ce2TiO6 type. 1.5 Yb 0.5 Ti 0.5 Al 0.5 O 5.5Therefore, the product of Example 21 was CeYAlO5 of the Ce2TiO6 type. When substituting Ti with Al in Ce2TiO6, substitution was possible up to 20 mol%, but Ce 4+ Y with small ionic radius and valency 3+ Ya Yb 3+ When you substitute with Ti, 4+ Al 3+ This increases the amount that can be substituted (CeYAlO5, in particular, contains no Ti at all).

[0136] Figure 8A shows the X-ray diffraction patterns of the products of Examples 1, 22, 23 and Comparative Example 13. Ce2TiO6, fluorite-type CeO2, Ce2TiO6-type Ce 1.5 Y 0.5 TiO 5.75 , Ce2TiO6 type Ce 1.5 La 0.5 TiO 5.75 For each product, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0137] Furthermore, Figure 8B shows the X-ray diffraction patterns of the products from Examples 1 and 24-26. Ce2TiO6, Ce2TiO6-type Ce 1.5 Pr 0.5 TiO 5.75 , Ce2TiO6 type Ce 1.5 Sm 0.5 TiO 5.75 , Ce2TiO6 type Ce 1.5 EU 0.5 TiO 5.75 For each product, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0138] Furthermore, Figure 8C shows the X-ray diffraction patterns of the products from Examples 1 and 27-29. Ce2TiO6, Ce2TiO6-type Ce 1.5 Yb 0.5 TiO 5.75 , Ce2TiO6 type Ce2Ti 0.9 Al 0.1 O 5.95 , Ce2TiO6 type Ce2Ti 0.9 Ga 0.1 O 5.95For each product, the X-ray diffraction pattern predicted from the crystal structure was calculated and compared with the X-ray diffraction pattern of each product.

[0139] From Figures 8A to 8C, the following was found: The product of Comparative Example 13 was mainly composed of CeO2. Ce2TiO6 can be obtained by calcination at 1,150°C under a reducing atmosphere (Example 1), but reduction is insufficient at a calcination temperature of 1,000°C. The product of Example 22 was Ce2TiO6 type Ce 1.5 Y 0.5 TiO 5.75 The product of Example 23 is Ce2TiO6 type Ce 1.5 La 0.5 TiO 5.75 The product of Example 24 is Ce2TiO6 type Ce 1.5 Pr 0.5 TiO 5.75 The product of Example 25 is Ce2TiO6 type Ce 1.5 Sm 0.5 TiO 5.75 The product of Example 26 is Ce2TiO6 type Ce 1.5 EU 0.5 TiO 5.75 The product of Example 27 is Ce2TiO6 type Ce 1.5 Yb 0.5 TiO 5.75 The product of Example 28 is Ce2TiO6 type Ce2Ti 0.9 Al 0.1 O 5.95 The product of Example 29 is Ce2TiO6 type Ce2Ti 0.9 Ga 0.1 O 5.95 Ce2TiO6 4+ to Y 3+ Ya La 3+ For rare earth element ions such as Ti 4+ Al 3+ Ya Ga 3+ Substituting with O, the charge compensation is O 2- The site has been modified to make it easier to reduce or O 2- Conductivity is improved, and a Ce2TiO6-type structure can be formed even at low firing temperatures.

[0140] Figure 8D shows the X-ray diffraction patterns of the products of Examples 1, 30, 31 and Comparative Example 10. Ce2TiO6, Ce2TiO6-type Ce 1.9 Ca 0.1 TiO 5.9 , Ce2TiO6 type Ce 1.9 Sr 0.1 TiO 5.9 For perovskite-type SrTiO3 and fluorite-type CeO2, the X-ray diffraction patterns predicted from the crystal structures were calculated and compared with the X-ray diffraction patterns of each product.

[0141] From Figure 8D, the following was found: The product of Example 30 is Ce2TiO6 type Ce 1.9 Ca 0.1 TiO 5.9 The product of Example 31 is Ce2TiO6 type Ce 1.9 Sr 0.1 TiO 5.9 The product of Comparative Example 10 is Ce2TiO6 type Ce 1.9 Sr 0.1 TiO 5.9 It was a mixture of perovskite-type SrTiO3 and fluorite-type CeO2. It is possible to substitute Ce in Ce2TiO6 with Ca or Sr. As the amount of Sr substitution increases, Ce2TiO6-type Ce 1.9 Sr 0.1 TiO 5.9 This yields a mixture of perovskite-type SrTiO3 and fluorite-type CeO2.

[0142] Table 3 shows the raw materials, calcination conditions, and phases contained in the obtained products for Examples 12-31 and Comparative Examples 10-13.

[0143] [Table 3]

[0144] Assuming that the products of Examples 12-21, 26, 27, 30, and 31 have a Ce2TiO6-type structure, and given a space group of Pnma and a Z value of 4, the lattice constants a, b, and c, as well as the lattice volume V, were determined. The results are shown in Table 4.

[0145] [Table 4]

[0146] From Tables 1-4, the angles of the X-ray diffraction peaks and the lattice constants of the composite oxide of the present invention are as follows. Measured value of Ia's 2θ: 27.84~30.28, range ±0.5 Measured value of Ib's 2θ: 32.76~35.72+α, range ±0.5 Actual measurement: 10.22~10.93, range ±1% b. Measured value: 3.686~3.922, range ±1% c. Measured value: 10.67~11.49, range ±1% V measured: 417.0~475.1, range ±1%

[0147] 2-2. Confirmation of oxygen desorption temperature and hydrogen consumption (i.e., amount of oxygen desorption) under a reducing atmosphere. The products of Examples 1 and 13 and Comparative Example 3 were subjected to hydrogen-temperature reduction (H2TPR). The measurement equipment and conditions are shown below.

[0148] • Measuring device: BELCAT A (Microtrac, manufactured by Bell Co., Ltd.)

[0149] The measurement conditions are shown below. • Pretreatment conditions: After introducing the product (approximately 50 mg) into a sample tube, the sample was heated to 500°C under a flow of 20% O2 / He at a rate of 30 mL / min, pretreated for 10 minutes, and then cooled. • Measurement conditions: After purging with Ar, the system was heated at 10°C / min while flowing 5% H2 / Ar at a rate of 30 mL / min, and the amount of hydrogen (H2) consumed was analyzed. The analysis was performed using a TCD, and a desiccant was placed before the TCD to trap the generated water.

[0150] The products of Examples 1 and 13 and Comparative Example 3 were similarly subjected to H2TPR with Pd-supported materials. The Pd-supporting conditions are shown below.

[0151] • Pd-supported conditions (Example 1 and Comparative Example 3): 30 mL of distilled water was placed in a 100 mL beaker, and Pd(NO3)2 was added to the product so that the Pd content was 1% by weight. The mixture was stirred at room temperature to dissolve, then the product was added and heated, and evaporated to dryness. The resulting solid was dried overnight at 120°C, then ground in a mortar, and calcined at 500°C for 3 hours to obtain a Pd-supported product.

[0152] Figure 4A shows the H2TPR results of the products before and after Pd loading for Examples 1 and 13 and Comparative Example 3. The peak that appears at low temperatures after Pd loading in Figure 4A is ( * The reduction in ) is thought to be due to the reduction of the supported Pd. In the products without supported Pd, Examples 1 and 13 showed a peak in hydrogen consumption at a lower temperature than Comparative Example 3, indicating that they released oxygen at lower temperatures. When Pd is supported, the peak in hydrogen consumption shifts to the lower temperature side in all products, but Examples 1 and 13 still show a peak in hydrogen consumption at a lower temperature than Comparative Example 3, indicating that they released oxygen at even lower temperatures.

[0153] Next, for the H2TPR results of the products of Examples 1 and 13 and Comparative Example 3 before and after Pd loading, the oxygen storage amount was determined from the total hydrogen consumption (excluding the hydrogen consumption derived from Pd in ​​the case of Pd loading). Table 5 shows the oxygen storage amounts of the products of Example 1 and Comparative Example 3 before and after Pd loading.

[0154] [Table 5]

[0155] Table 5 shows that, regardless of the presence or absence of Pd support, Example 1 showed a larger oxygen storage capacity than Comparative Example 3, and Example 13 showed an even larger oxygen storage capacity than Comparative Example 3.

[0156] 2-3. Measurement of OSC (Oxygen Storage Capacity) at various temperatures The oxygen storage capacity of the products from Examples 1, 3, 4, 13, 19, 20, 26, and 27, and Comparative Example 3, which were supported with 1% by weight of Pd, was evaluated at each temperature.

[0157] The Pd loading conditions are as follows. • Pd-supported conditions: 30 mL of distilled water was placed in a 100 mL beaker, and Pd(NO3)2 was added to the product so that the Pd content was 1% by weight. The mixture was stirred at room temperature to dissolve, then the product was added and heated, and evaporated to dryness while stirring. The resulting solid was dried overnight at 120 °C, then ground in a mortar, and calcined at 500 °C for 2 hours to obtain a Pd-supported product.

[0158] The measuring device and measurement conditions are shown below. • Measuring device: Fixed-bed flow reactor equipped with FT-IR analyzer (manufactured by Best Measuring Instruments Co., Ltd.) • Pelletization conditions: The products of Example 1 and Comparative Example 3, with Pd supported on them, were compacted into powder at 196 kN using a cold isostatic pressing method. The molded bodies were then crushed and sieved, and 2 g of the resulting pellets were used for evaluation. Pretreatment conditions: 5% O2 / N2 was flowed at 200°C for 5 minutes at a rate of 10 L / min. • Measurement conditions: Oxygen storage capacity was measured at 200°C, 300°C, 400°C, 500°C, and 600°C. The flow rate was always 10 L / min, and a cycle of 1% O2 / N2 for 2 minutes, N2 for 20 seconds, 2% CO / N2 for 2 minutes, and N2 for 20 seconds was repeated 6 times at each temperature. The amount of CO2 detected while CO was flowing was accumulated over the 2nd to 5th cycles, divided by 4, and then divided by the sample amount of 2 g to determine the oxygen storage capacity.

[0159] Figure 4B shows the oxygen storage capacity at each temperature for Examples 1 and 13 and Comparative Example 3, which are supported with Pd. From Figure 4B, at all measured temperatures, Example 1 (Ce2TiO6 type) and Example 13 (Ce2TiO6 type Ce2Ti 0.8 Al 0.2 O 5.9 It was found that the oxygen storage capacity of comparative example 3 (pyrochlore type) exceeded that of comparative example 3.

[0160] Figure 9 shows the oxygen storage capacity at various temperatures for Examples 1, 3, 4, 13, 19, 20, 26, and 27, and Comparative Example 3, all of which were supported with Pd. From Figure 9, it can be seen that at all measured temperatures, Examples 1, 13, 19, and 26, which were supported with Pd, had a higher oxygen storage capacity than Comparative Example 3, which was also supported with Pd. Furthermore, Examples 3, 4, and 20, which were supported with Pd, had a higher oxygen storage capacity than Comparative Example 3, which was also supported with Pd, at 300°C. In addition, Example 27, which was supported with Pd, had a higher oxygen storage capacity than Comparative Example 3, which was also supported with Pd, at 600°C.

[0161] 2-4. Confirmation of weight change (oxygen storage capacity) under an oxidizing atmosphere The weight changes of the products of Examples 1-11 and Comparative Examples 4-8 were determined when the Pd-supported products were reduced at 500°C for 6 hours under a 10% H2 / Ar atmosphere and then oxidized at 500°C for 2 hours in air. Figure 5A shows the weight changes of Examples 1-8, and Figure 5B shows the weight changes of Examples 9-11 and Comparative Examples 4-8. The products of Examples 1-11, which contain Ce, showed a significant weight change due to oxidation, confirming their oxygen storage capacity. On the other hand, the products of Comparative Examples 4-6, which contain Ce as CeO2, did not show a significant weight change due to oxidation. The products of Comparative Examples 7 and 8, which contain rare earth elements other than Ce, did not show a significant weight change due to oxidation. From these results, it was found that compounds with a Ce2TiO6 type crystal structure containing Ce have excellent oxygen storage capacity.

[0162] 2-5. Confirmation of changes in crystal structure due to oxidation-reduction The crystal structure of the product from Example 1 was confirmed under reduced conditions. The reduction apparatus and reduction conditions are shown below.

[0163] • Reduction apparatus: Fixed-bed flow reactor • Pelletization conditions: The product from Example 1 was compacted into powder at 196 kN using a cold isostatic pressing method. The molded body was then crushed and sieved, and 1 g of the resulting pellet was used for the experiment. • Reduction conditions: The pellets were reduced by flowing 5% H2 / N2 at 750°C for 30 minutes at a rate of 10 L / min. After the pellets cooled to room temperature, they were transferred to a resealable bag filled with Ar, a hole was made in the end of the bag, and the bag was left in a refrigerator for 1 hour to oxidize only the outermost surface of the pellets.

[0164] Figure 6 shows the X-ray diffraction patterns of the product of Example 1 before and after reduction. For Ce2TiO6 and Y2TiO5-type Ce2TiO5, the X-ray diffraction patterns expected from the crystal structure were calculated and compared with the X-ray diffraction patterns before and after reduction. The product of Example 1 after reduction showed an X-ray diffraction pattern similar to that of Y2TiO5-type Ce2TiO5. From these results, it can be concluded that Ce2TiO6 is in the oxidized state and Ce2TiO5 has a crystal structure similar to that of the reduced state Y2TiO5-type. 6-δ It was found that the amount of oxygen in the product increases or decreases as the temperature changes between these two points, thus exhibiting oxygen storage capacity.

[0165] Note that the Ce2TiO2 immediately after reduction of the product from Example 1 6-δ It was found that the material is highly susceptible to oxidation, and the heat generated by oxidation further accelerates the oxidation process. Therefore, when the reduced pellets are exposed directly to room temperature air, they transform into Ce2TiO6.

[0166] 2-6. Consideration of the oxygen storage mechanism (relationship between crystal structure and oxygen storage capacity) Figure 1A shows the crystal structure of La2TiO5, and Figure 1B shows the crystal structure of Ce2TiO6. Trivalent rare earth metal ions such as La2TiO5 and tetravalent titanium ions (Ti 4+ Oxides containing ) have a Y2TiO5 type crystal structure. O in La2TiO5 2- When conduction occurs, O occurs in the b-axis direction in Figure 1A. 2- It is thought that conduction occurs, and computational studies have shown that excess O in La2TiO5 2- If such a TiO5 square pyramid exists, 4+ The position that approaches and forms a TiO6 octahedron is stable, O 2-It is expected that the conduction barrier energy will be low (E. Kendrick et al., Solid State Ionics, 179, pp. 819-822, 2008, "A computational study of oxide ion migration and water incorporation in the cuspidine system, La4(Ti2O8)O2"). Analysis of the crystal structure shows that Ce2TiO6 is similar to La2TiO5, but La 3+ to Ce 4+ Substitute with and use excess O as charge compensation 2- It is thought to be a material with a new crystal structure, the Ce2TiO6 type structure, which incorporates excess O. 2- This is a TiO5 square pyramid of Ti 4+ It is presumed to be located in a position that approaches and forms a TiO6 octahedron. When Ce2TiO6 is reduced, Ce 4+ Ce 3+ As a result, excess O is used as charge compensation. 2- It releases oxygen (O2), and the crystal structure of Ce2TiO6 is closer to that of Y2TiO5. 6-δ This is thought to indicate oxygen storage capacity.

[0167] Among the rare earth metal elements, those containing Ce, which has a stable tetravalent ion, adopt a Ce2TiO6 type structure, and depending on their composition, O 2- It is presumed that there is a deficiency. Rare earth metal elements are stable as trivalent ions, and in the oxide according to one embodiment of the present invention, Y is Y 3+ , La is La 3+ , Sm is Sm 3+ It exists in this state. Ce is stable in trivalent and tetravalent ions, and among rare earth metal elements, the tetravalent ion is the most stable; therefore, in one aspect of the present invention, after synthesis, Ce 4+ It is obtained in this state, and in a reducing atmosphere Ce 3+ Therefore, it exhibits oxygen storage capacity. Although both trivalent and tetravalent ions of Pr are stable, the tetravalent ion is less stable than that of Ce, and in the oxide of one embodiment of the present invention, almost all Pr 3+ It exists in this state, Pr 4+ Because it is not easily oxidized, it contributes very little to oxygen storage capacity.

[0168] The composition after synthesis is Ce 2-x A x TiO 6-y If (A=Y, La, Pr, or Sm), then as x increases, Ce 4+ to A 3+ This will be substituted with O as charge compensation. 2- Because it needs to be missing, for example Ce 1.5 La 0.5 TiO 5.75 The composition will be as follows.

[0169] 2-7. Relationship between firing in a reducing atmosphere and the products produced In one embodiment of the present invention, a precursor is calcined in a reducing atmosphere. 4+ and Tire 4+ Since a mixture of CeO2 and TiO2 is obtained when a precursor containing Ce is calcined in an oxidizing atmosphere, Ce2TiO6 is considered to be a metastable phase. In order to obtain Ce2TiO6, it is necessary to calcine it once in a reducing atmosphere. 4+ to Ce 3+ Reduce to Ce 3+ and Tire 4+ It is presumed that the process must proceed via Ce2TiO5, an oxide containing [unclear]. In the example, the precursor oxide is mixed with activated carbon, and a large excess of activated carbon is placed on top and calcined. It is thought that the incomplete combustion of the activated carbon consumes O2 in the atmosphere and generates CO, creating a reducing atmosphere. In a reducing atmosphere with CO present, most of the Ce is converted to Ce 3+ Therefore, it is presumed that Ce2TiO5 is formed. When the activated carbon stops burning during the cooling process after firing, the reducing atmosphere disappears, and Ce 3+ Ya Ti 4+ At temperatures where there is no movement, Ce2TiO5 reacts with atmospheric O2, causing Ce 3+ Ce is oxidized 4+ As a result, Ce2TiO6 is obtained as the product.

Claims

1. general formula Yes ２－ｗ－ｘ’ A ｗ A' ｘ’ B １－ｙ’－ｚ B' ｙ’ B'' ｚ O ６－ｗ／２－ｘ’－ｚ A composite oxide having a composition represented by, During the ceremony, A is one or more elements selected from rare earth metal elements excluding Ce. A' is one or more elements selected from alkaline earth metal elements. B is one or more elements selected from the group consisting of Ti and Group 14 elements. B' is one or more elements selected from the group consisting of Group 13 elements. B'' is one or more elements selected from the group consisting of Group 12 elements. 2-w-x', w, x', 1-y'-z, y', z, and 6-w / 2-x'-z are the molar ratios of Ce, A, A', B, B', B'', and O, respectively, when B + B' + B'' is set to 1. w, x', y', and z satisfy 0 ≤ w < 2, 0 ≤ x' < 0.5, 0 ≤ y' ≤ 1, and 0 ≤ z ≤ 0.5, respectively. w + x' satisfies 0 ≤ w + x' < 2, and y' + z satisfies 0 ≤ y' + z ≤ 1. Complex oxides.

2. In an X-ray diffraction pattern in which the range of 2θ measured using CuKα for the X-ray source is 5 deg. to 90 deg., the angle of the maximum X-ray diffraction peak showing the highest intensity is such that 2θ is in the range of 27 deg. to 31 deg., and the peak intensity of the maximum X-ray diffraction peak is I ａ is defined as, and among the X-ray diffraction peaks in which 2θ is in the range of 32 deg. to 37 deg., the maximum peak intensity is I ｂ When defined as such, I ｂ / I ａ satisfies 0.15 ≤ I ｂ / I ａ ≤ 0.

85. The composite oxide according to claim 1.

3. In the crystal structure determined by X-ray diffraction after heating at 500°C in air for 6 hours, when the space group is Pnma and the Z value is 4, the lattice constants a, b, and c and the lattice volume V are, respectively, 10.1 Å ≤ a ≤ 11.1 Å, 3.64 Å ≤ b ≤ 3.97 Å, 10.5 Å ≤ c ≤ 11.7 Å, and 412 Å. ３ ≤V ≤ 480 Å ３ The composite oxide according to claim 2, satisfying the condition that (the values ​​between lattice constants a, b, and c may be interchangeable).

4. The composite oxide according to claim 1, wherein B contains Ti and satisfies 0 ≤ 1 - y' - z.

5. The composite oxide according to claim 1, wherein B' contains Al and satisfies 0 < y'.

6. The composite oxide according to claim 1, satisfying 0 < w + x' + y' + z.

7. An oxygen storage material comprising a composite oxide according to any one of claims 1 to 6.

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