Cerium oxide stabilized zirconium composition

Abstract

This cerium oxide stabilized zirconium composition is characterized by having a composition that is represented by formula [1], and is also characterized by having a specific surface area of 5 m2 / g to 20 m2 / g inclusive.　Formula [1]: (ZrO2)1-x-y(CeO2)x(M2O3)y In formula [1], x and y are numbers that satisfy 0.10 ≤ x ≤ 0.40 and 0.02 ≤ y ≤ 0.12, and M represents one or more elements that are selected from the group consisting of scandium, yttrium, and ytterbium.

Description

Cerium oxide stabilized zirconium composition

[0001] The present invention relates to cerium oxide stabilized zirconium compositions.

[0002] Conventionally, a cermet made of Ni particles and ceramic powder exhibiting oxygen ion conductivity has been used as an anode material in SOFCs (Solid Oxide Fuel Cells).

[0003] In Non-Patent Document 1, (Sc ２ O ３ ) ０．１０ (CeO ２ ) ０．０１ (ZrO ２ ) ０．８９ It is disclosed that the above was applied to an electrode cermet material and a study was carried out on an internal methane reforming fuel cell system using steam reforming.

[0004] In Non-Patent Document 2, CeO is used as a catalyst for dry reforming reactions. ２ , ZrO ２ , Al ２ O ３ , SiO ２ , TiO ２ is being investigated, and CeO ２ It has been shown that the catalyst has high reforming performance and durability due to its carbon deposition suppression effect.

[0005] In Non-Patent Document 3, Ce ０．５ Zr ０．５ O ２ The study of CeO ２ , ZrO ２ It has been shown to have higher reforming performance and carbon deposition suppression effect compared to

[0006] In Non-Patent Document 4, Mg, La, and Ca are used as Ni carriers. ０．５ Zr ０．５ O ２ It has been shown that by dissolving the catalyst in a solid solution and introducing oxygen vacancies, catalytic performance and durability have been improved.

[0007] Carbon deposition behavior on Ni-ScSZ anodes for internal reforming solid oxide fuel cellsNickel based catalysts for methane dry reforming: Effect of supports on catalytic activity and stabilityNi / CexZr1-xO2catalyst prepared via one-step co-precipitation for CO2 reforming of CH4 to produce syngas: role of oxygen storage capacity (OSC) and oxygen vacancy formation energy (OVFE)High performance NiO / MOx-Ce0.5Zr0.5O2catalysts promoted with metal oxides for CH4-H2O reforming

[0008] Currently, commercially available fuel cell systems have a reformer installed in front of the stack that generates electricity. City gas and other fuels are reformed in the reformer to produce hydrogen, which is then supplied to the stack to generate electricity. Because hydrogen is produced in a reformer installed separately from the stack and then supplied to the stack, the load on the stack is reduced. However, having a reformer separate from the stack increases the overall system size and increases the cost of the system.

[0009] In response to the above problem, internal reforming has been studied in recent years, in which unreformed fuel is directly introduced into the stack and reformed on the electrodes of the stack.

[0010] However, CH ４ and CO ２In the case of an internal reforming fuel cell system that mainly uses dry reforming to obtain hydrogen from methane, there are problems such as a decrease in reforming ability and deactivation of electrochemical reaction active sites due to carbon precipitated by the reforming reaction. In a methane internal reforming fuel cell system using a dry reforming reaction, the reforming reaction proceeds under conditions that make it easier for carbon to precipitate. Therefore, as a ceramic material for constituting the anode cermet, for example, Sc ２ O ３ ) ０．１０ (CeO ２ ) ０．０１ (ZrO ２ ) ０．８９ cannot be used.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a cerium oxide-stabilized zirconium composition that has high oxygen ion conductivity and can be used as a material for an electrode that has high reforming function (high catalytic function and long-term stability of the catalytic function) when a catalyst is supported thereon.

[0012] The present invention provides the following: (1) A composition represented by the following formula [1], having a specific surface area of ​​5 m ２ / g or more 20m ２ / g or less. ２ ) １－ｘ－ｙ (CeO ２ ) ｘ (M ２ O ３ ) ｙ [1] However, in formula [1], x and y are numbers that satisfy 0.10≦x≦0.40 and 0.02≦y≦0.12, and M is one or more elements selected from the group consisting of scandium, yttrium, and ytterbium.

[0013] The solid solution of cerium oxide in a zirconium material can improve the oxygen storage / release capacity and the reforming function when a catalyst is supported, but it cannot improve oxygen ion conductivity. On the other hand, the solid solution of scandium oxide, yttrium oxide, or ytterbium oxide in a zirconium material can introduce oxygen vacancies into the zirconium material and improve oxygen ion conductivity, but it does not have oxygen storage / release capacity. According to the configuration (1), the zirconium material has a composition represented by the above formula [1], where x and y are numbers satisfying 0.10≦x≦0.40 and 0.02≦y≦0.12, and M is one or more selected from the group consisting of scandium, yttrium, and ytterbium. Since x is 0.10 or more, the oxygen storage / release capacity can be improved, carbon deposition can be suppressed, and the reforming function when a catalyst is supported can be improved. Furthermore, since x is 0.40 or less, an appropriate amount of oxide of M can be contained, resulting in improved oxygen ion conductivity. Furthermore, since the y is 0.02 or more, the oxygen ion conductivity can be increased. Furthermore, since the y is 0.12 or less, an appropriate amount of cerium oxide can be contained, thereby improving the reforming function when a catalyst is supported. Thus, according to the above configuration, since the cerium oxide and the oxide of M are contained within a certain composition range, the material can be used as a material for an electrode that has high oxygen ion conductivity and high reforming function when a catalyst is supported.

[0014] In addition, it is generally considered preferable that a carrier used as a catalyst material has a high specific surface area from the viewpoint of preventing aggregation of the catalyst metal, but when used as an electrode material, physical defects may occur due to volume shrinkage during sintering. ２ / g or less, it is possible to prevent physical defects from occurring due to volume shrinkage during sintering when used as an electrode material. The materials disclosed in Non-Patent Documents 3 and 4 are materials intended for catalytic applications. In particular, Non-Patent Document 4 uses a 50 m ２ / g or more, but when considering use as an electrode material, physical defects caused by changes in sintering volume during sintering are considered, making it impossible to use as an electrode material. Furthermore, since the materials disclosed in Non-Patent Documents 3 and 4 are intended for catalytic use, Non-Patent Documents 3 and 4 do not consider measures to improve oxygen ion conductivity, which is necessary for use as an electrode material in a fuel cell.

[0015] As described above, according to the configuration (1), the composition and specific surface area are optimized, and therefore the carbon nanotube has high oxygen ion conductivity and can be used as an electrode material having high reforming function (high catalytic function and long-term stability of the catalytic function) when a catalyst is supported thereon.

[0016] In addition, biogas produced by fermenting waste materials is ４ and CO ２ It is a gas whose main component is CH ４ :CO ２ Dry reforming is a process for reforming methane to obtain hydrogen by CO ２ According to the configuration (1), the biogas has a high reforming function in the reforming reaction by dry reforming, and therefore the biogas can be suitably used as fuel for the fuel cell.

[0017] The present invention further provides the following: (2) The cerium oxide-stabilized zirconium composition according to (1), wherein M is one element selected from the group consisting of scandium, yttrium, and ytterbium.

[0018] Furthermore, the present invention provides the following: (3) The cerium oxide-stabilized zirconium composition according to (1) above, wherein M is scandium.

[0019] The present invention further provides the following: (4) The cerium oxide-stabilized zirconium composition according to any one of (1) to (3), wherein x and y are numbers satisfying 0.10≦x≦0.30 and 0.06≦y≦0.10.

[0020] When the x and y are numbers that satisfy the conditions of 0.10≦x≦0.30 and 0.06≦y≦0.10, the material has higher oxygen ion conductivity and can be used as an electrode material that has a higher reforming function when a catalyst is supported thereon.

[0021] Furthermore, the present invention provides the following: (5) The cerium oxide-stabilized zirconium composition according to any one of (1) to (4), wherein the y is a number satisfying 0.08≦y≦0.10.

[0022] When the y is a number that satisfies 0.08≦y≦0.10, the material has higher oxygen ion conductivity and can be used as an electrode material that has a higher reforming function when a catalyst is supported thereon.

[0023] Furthermore, the present invention provides the following: (6) An oxygen absorption / desorption capacity of 5 μmol / m at 750°C. ２ The cerium oxide-stabilized zirconium composition according to any one of (1) to (5), characterized in that:

[0024] Oxygen absorption / desorption capacity at 750°C is 5 μmol / m ２ If the amount is more than this, the reforming function when the catalyst is supported can be further improved.

[0025] Furthermore, the present invention provides the following: (7) A conductive material having a conductivity of 9.0×10 at 700°C after heat treatment under the following heat treatment condition A: －４ The cerium oxide-stabilized zirconium composition according to any one of (1) to (6) above, characterized in that the composition has a viscosity of 1.0 t / cm or more. ２ After molding at a pressure of 1000 kJ for 2 minutes, the mixture is heat-treated in air at 1450° C. for 2 hours.

[0026] After heat treatment under the heat treatment condition A, the electrical conductivity at 700°C was 9.0 × 10－４ When the oxygen ion conductivity is 25 S / cm or more, the oxide has high oxygen ion conductivity and can be suitably used as an electrode material.

[0027] Furthermore, the present invention provides the following: (8) A conductive material having a conductivity of 3.0×10 at 800°C after heat treatment under the following heat treatment condition A: －３ The cerium oxide-stabilized zirconium composition according to any one of (1) to (7), characterized in that the composition has a viscosity of 1.0 t / cm or more. ２ After molding at a pressure of 1000 kJ for 2 minutes, the mixture is heat-treated in air at 1450° C. for 2 hours.

[0028] After heat treatment under the heat treatment condition A, the electrical conductivity at 800°C was 3.0 × 10 －３ When the oxygen ion conductivity is 25 S / cm or more, the oxide has high oxygen ion conductivity and can be more suitably used as an electrode material.

[0029] Furthermore, the present invention provides the following: (9) A conductive material having a conductivity of 7.5×10 at 900°C after heat treatment under the following heat treatment condition A: －３ The cerium oxide-stabilized zirconium composition according to any one of (1) to (8) above, characterized in that the composition has a viscosity of 1.0 t / cm or more. ２ After molding at a pressure of 1000 kJ for 2 minutes, the mixture is heat-treated in air at 1450° C. for 2 hours.

[0030] After heat treatment under the heat treatment condition A, the electrical conductivity at 900°C was 7.5 × 10 －３ When the oxygen ion conductivity is 25 S / cm or more, the oxide has high oxygen ion conductivity, and can be more suitably used as an electrode material.

[0031] Furthermore, the present invention provides the following: (10) The cerium oxide-stabilized zirconium composition according to any one of (1) to (9) above, which is used as a support for supporting a transition metal.

[0032] When used as a support for supporting a transition metal, the resulting electrode has higher oxygen ion conductivity and can have a higher reforming function.

[0033] Furthermore, the present invention provides the following: (11) The cerium oxide-stabilized zirconium composition according to (10) above, wherein the transition metal is nickel.

[0034] When the transition metal is nickel, the electrode has higher oxygen ion conductivity and can have a higher modifying function.

[0035] Furthermore, the present invention provides the following: (12) After heat treatment under the following heat treatment condition B, CH ４ :CO ２ :N ２ A gas mixture of 4.5:4.5:1 was placed at a space velocity of 8000 h －１ CH when distributed ４ Conversion rate is 90% or more, CO ２ Conversion rate is 85% or more, H ２ The cerium oxide-stabilized zirconium composition according to any one of (1) to (11), characterized in that the selectivity is 40% or more and the CO selectivity is 40% or more. <Heat Treatment Condition B> Nickel oxide is mixed with the composition so that the content is 60 mass%, and the composition is heat-treated in air at 1300°C for 2 hours to form a cermet.

[0036] After heat treatment under the heat treatment condition B, CH ４ :CO ２ :N ２ A gas mixture of 4.5:4.5:1 was placed at a space velocity of 8000 h －１ CH when distributed ４ Conversion rate is 90% or more, CO ２ Conversion rate is 85% or more, H ２ When the selectivity is 40% or more and the CO selectivity is 40% or more, the raw material CH ４ , CO ２ is efficiently consumed, and H ２ It can be said that the by-product CO is efficiently obtained.

[0037] According to the present invention, it is possible to provide a cerium oxide-stabilized zirconium composition that has high oxygen ion conductivity and can be used as a material for an electrode that has high reforming function (high catalytic function and long-term stability of the catalytic function) when a catalyst is supported thereon.

[0038] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to these embodiments. In this specification, the cerium oxide-stabilized zirconium oxide composition is a general one, and contains 10 mass % or less of impurity metal compounds, including hafnium. In addition, in this specification, the expressions "contain" and "comprise" include the concepts of "contain," "comprise," "substantially consist," and "consist only of."

[0039] The maximum and minimum values ​​of the content of each component shown below are independently the preferred minimum and maximum values ​​of the present invention, regardless of the content of other components.Furthermore, the maximum and minimum values ​​of various parameters (measured values, etc.) shown below are independently the preferred minimum and maximum values ​​of the present invention, regardless of the content (composition) of each component.

[0040] [Cerium oxide-stabilized zirconium oxide composition] The cerium oxide-stabilized zirconium oxide composition according to this embodiment has a composition represented by the following formula [1], and a specific surface area of ​​5 m ２ / g or more 20m ２ / g or less. (ZrO ２ ) １－ｘ－ｙ (CeO ２ ) ｘ (M ２ O ３ ) ｙ [1] However, in formula [1], x and y are numbers that satisfy 0.10≦x≦0.40 and 0.02≦y≦0.12, and M is one or more elements selected from the group consisting of scandium, yttrium, and ytterbium.

[0041] The solid solution of cerium oxide in a zirconium material can improve the oxygen storage / release capacity and the reforming function when a catalyst is supported, but it cannot improve oxygen ion conductivity. On the other hand, the solid solution of scandium oxide, yttrium oxide, or ytterbium oxide in a zirconium material can introduce oxygen vacancies into the zirconium material and improve oxygen ion conductivity, but it does not have oxygen storage / release capacity. The cerium oxide-stabilized zirconium composition has a composition represented by the above formula [1], where x and y are numbers satisfying 0.10≦x≦0.40 and 0.02≦y≦0.12, and M is one or more selected from the group consisting of scandium, yttrium, and ytterbium. Since x is 0.10 or more, the oxygen storage / release capacity can be improved, and the reforming function when a catalyst is supported can be improved. Furthermore, since x is 0.40 or less, an appropriate amount of oxide of M can be contained, resulting in improved oxygen ion conductivity. Furthermore, since the y is 0.02 or more, oxygen ion conductivity can be increased. Furthermore, since the y is 0.12 or less, an appropriate amount of cerium oxide can be contained, thereby improving the reforming function when a catalyst is supported. Thus, since the cerium oxide-stabilized zirconium composition contains cerium oxide and the oxide of M within a certain composition range, it has high oxygen ion conductivity and can be used as a material for electrodes that have a high reforming function when a catalyst is supported.

[0042] The x is preferably 0.10 or more, more preferably 0.20 or more. The x is preferably 0.30 or less. The x is preferably a number that satisfies 0.10≦x≦0.30, more preferably 0.20≦x≦0.30.

[0043] The y is preferably 0.06 or more, more preferably 0.08 or more. The y is preferably 0.10 or less. The y is preferably a number that satisfies 0.06≦y≦0.10, more preferably 0.08≦y≦0.10.

[0044] The M is preferably one element selected from the group consisting of scandium, yttrium, and ytterbium. The M is more preferably scandium. When the M is scandium, higher electrical conductivity can be exhibited compared to other elements (yttrium, ytterbium).

[0045] The specific surface area of ​​the cerium oxide-stabilized zirconium composition is 5 m ２ / g or more 20m ２ / g or less. ２ / g or less, it is possible to prevent physical defects from occurring due to volume shrinkage during sintering when used as an electrode material.

[0046] The specific surface area is preferably 15 m ２ / g or less, more preferably 12m ２ The specific surface area is 7 m / g or less from the viewpoint of ensuring an area for carrying out the dry reforming reaction. ２ The specific surface area is preferably 5 m / g or more. ２ / g or more 15m ２ / g or less, more preferably 7m ２ / g or more 12m ２ / g or less.

[0047] The cerium oxide-stabilized zirconium oxide composition may further contain a rare earth element other than Ce, Sc, Y, and Yb. From the viewpoint of suppressing deterioration of sintering characteristics, catalytic activity, and oxygen ion conductivity, the content of the rare earth element other than Ce, Sc, Y, and Yb is preferably 1 mol % or less, more preferably 0.5 mol % or less, and even more preferably 0.1 mol % or less.

[0048] The cerium oxide-stabilized zirconium oxide composition contains Na, which is derived from the manufacturing process, etc. ２ O, SO ４ , Cl may be contained. ２ O, SO ４The content of Cl is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and even more preferably 0.005% by mass or less, from the viewpoint of suppressing a decrease in sintering characteristics, catalytic activity, and oxygen ion conductivity. ２ O, SO ４ The Cl content can be reduced to 0.1 mass % or less by controlling the synthesis conditions and the washing step.

[0049] The cerium oxide-stabilized zirconium oxide composition contains Al in order to improve sintering characteristics. ２ O ３ may be included as a sintering aid. ２ O ３ The content is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.25% by mass or less, and particularly preferably 0.01% by mass or less.

[0050] The cerium oxide-stabilized zirconium oxide composition has an oxygen storage capacity (OSC) of 5 μmol / m at 750° C. ２ It is preferable that the oxygen absorption / desorption capacity at 750°C is 5 μmol / m or more. ２ If the amount is more than this, the reforming function when the catalyst is supported can be further improved.

[0051] The oxygen absorption / desorption capacity at 750°C is more preferably 7 μmol / m ２ More preferably, 10 μmol / m ２ More preferably, 13 μmol / m ２ More than 14 μmol / m ２ More than 17 μmol / m ２ The higher the oxygen absorption / release capacity at 750°C, the better. ２ Below, 50 μmol / m ２ The oxygen absorption / release capacity at 750°C is more preferably 7 μmol / m ２ 50μmol / m or more ２ More preferably, 10 μmol / m or less ２ 50μmol / m or more ２Particularly preferably 13 μmol / m or less ２ 50μmol / m or more ２ Below, particularly preferably 14 μmol / m ２ 50μmol / m or more ２ Below 17 μmol / m ２ 40 μmol / m or more ２ The following is the result.

[0052] The cerium oxide-stabilized zirconium oxide composition has a conductivity of 9.0×10 at 700° C. after heat treatment under the following heat treatment condition A. －４ <Heat treatment condition A> Cold isostatic pressing is performed at 1.0 t / cm or more. ２ After molding at a pressure of 1000 kJ for 2 minutes, the mixture is heat-treated in air at 1450° C. for 2 hours.

[0053] After heat treatment under the heat treatment condition A, the electrical conductivity at 700°C was 9.0 × 10 －４ When the oxygen ion conductivity is 25 S / cm or more, the oxide has high oxygen ion conductivity and can be suitably used as an electrode material.

[0054] The conductivity at 700°C is more preferably 0.95 × 10 －３ S / cm or more, more preferably 1.0 × 10 －３ S / cm or more, particularly preferably 2.0 × 10 －３ S / cm or more, particularly preferably 3.0 x 10 －３ S / cm or more, especially preferably 5.0 × 10 －３ The higher the conductivity at 700°C, the more preferable it is. －２ S / cm or less, 5.0×10 －２ The conductivity at 700°C is more preferably 0.95 × 10 －３ S / cm or more 5.0×10 －２ S / cm or less, more preferably 1.0 × 10 －３ S / cm or more 5.0×10 －２ S / cm or less, particularly preferably 2.0 × 10 －３ S / cm or more 5.0×10 －２ S / cm or less, particularly preferably 3.0 x 10－３ S / cm or more 5.0×10 －２ S / cm or less, especially preferably 5.0 × 10 －３ S / cm or more 4.0×10 －２ The following is the result.

[0055] The cerium oxide-stabilized zirconium oxide composition has a conductivity of 3.0×10 at 800° C. after heat treatment under the following heat treatment condition A. －３ <Heat treatment condition A> Cold isostatic pressing is performed at 1.0 t / cm or more. ２ After molding at a pressure of 1000 kJ for 2 minutes, the mixture is heat-treated in air at 1450° C. for 2 hours.

[0056] After heat treatment under the heat treatment condition A, the electrical conductivity at 800°C was 3.0 × 10 －３ When the oxygen ion conductivity is 25 S / cm or more, the oxide has high oxygen ion conductivity and can be more suitably used as an electrode material.

[0057] The conductivity at 800°C is more preferably 3.5×10 －３ S / cm or more, more preferably 4.0 × 10 －３ S / cm or more, particularly preferably 5.0 × 10 －３ S / cm or more, particularly preferably 8.0 x 10 －３ S / cm or more, especially preferably 1.0 × 10 －２ The higher the conductivity at 800°C, the more preferable it is. －２ S / cm or less, 1.0×10 －１ The conductivity at 800°C is more preferably 3.5 × 10 －３ S / cm or more 1.0×10 －１ S / cm or less, more preferably 4.0 × 10 －２ S / cm or more 1.0×10 －１ S / cm or less, particularly preferably 5.0 × 10 －３ S / cm or more 1.0×10 －１ S / cm or less, particularly preferably 8.0 x 10 －３ S / cm or more 1.0×10 －１ S / cm or less, especially preferably 1.0 × 10 －２S / cm or more 9.0×10 －２ S / cm or less.

[0058] The cerium oxide-stabilized zirconium oxide composition has a conductivity of 7.5×10 at 900° C. after heat treatment under the following heat treatment condition A. －３ <Heat treatment condition A> Cold isostatic pressing is performed at 1.0 t / cm or more. ２ After molding at a pressure of 1000 kJ for 2 minutes, the mixture is heat-treated in air at 1450° C. for 2 hours.

[0059] After heat treatment under the heat treatment condition A, the electrical conductivity at 900°C was 7.5 × 10 －３ When the oxygen ion conductivity is 25 S / cm or more, the oxide has high oxygen ion conductivity, and can be more suitably used as an electrode material.

[0060] The electrical conductivity at 900°C is more preferably 9.0 × 10 －３ S / cm or more, more preferably 1.0 × 10 －２ S / cm or more, particularly preferably 1.5×10 －２ S / cm or more, particularly preferably 1.8 x 10 －２ S / cm or more, especially preferably 2.0 × 10 －２ The higher the conductivity at 900°C, the more preferable it is. －１ S / cm or less, 2.5×10 －１ The electrical conductivity at 900°C is more preferably 9.0 × 10 －３ S / cm or more 2.5×10 －１ S / cm or less, more preferably 1.0 × 10 －２ S / cm or more 2.5×10 －１ S / cm or less, particularly preferably 1.5 × 10 －２ S / cm or more 2.5×10 －１ S / cm or less, particularly preferably 1.8 x 10 －２ S / cm or more 2.5×10 －１ S / cm or less, especially preferably 2.0 x 10 －２ S / cm or more 2.0×10 －１ S / cm or less.

[0061] The cerium oxide-stabilized zirconium oxide composition was heat-treated under the following heat treatment condition B, and then subjected to CH ４ :CO ２ :N ２ A gas mixture of 4.5:4.5:1 was placed at a space velocity of 8000 h －１ CH when distributed ４ Conversion rate is 90% or more, CO ２ Conversion rate is 85% or more, H ２ Preferably, the selectivity is 40% or more and the CO selectivity is 40% or more. <Heat Treatment Condition B> Nickel oxide is mixed with the composition so that the content is 60 mass%, and the mixture is heat-treated in air at 1300°C for 2 hours to form a cermet.

[0062] After heat treatment under the heat treatment condition B, CH ４ :CO ２ :N ２ A gas mixture of 4.5:4.5:1 was placed at a space velocity of 8000 h －１ CH when distributed ４ Conversion rate is 90% or more, CO ２ Conversion rate is 85% or more, H ２ When the selectivity is 40% or more and the CO selectivity is 40% or more, the raw material CH ４ , CO ２ is efficiently consumed, and H ２ It can be said that the by-product CO is efficiently obtained.

[0063] Here, the CH ４ Conversion rate, ２ Conversion rate, ２ The CO selectivity is a value obtained by the following formula: [CH ４ Conversion rate (%) = [(introduced CH ４ flow rate) - (outlet side CH ４ flow rate)] / [introduction CH ４ Flow rate]]×100 [CO ２ Conversion rate (%) = [(introduced CO ２ flow rate) - (outlet side CO ２ flow rate)] / [introduced CO ２ Flow rate]]×100 [H ２ Selection rate (%)] = [(exit side H ２flow rate) / [2×[[(introduction CH ４ flow rate) - (outlet side CH ４ flow rate)] + [(introduced CO ２ flow rate) - (outlet side CO ２ Flow rate)]]]]×100 [CO selectivity (%)]=[(Outlet side CO flow rate) / [2×[[(Introduction CH ４ flow rate) - (outlet side CH ４ flow rate)] + [(introduced CO ２ flow rate) - (outlet side CO ２ flow rate)]]]]×100

[0064] The CH ４ The conversion rate is more preferably 95% or more, further preferably 96% or more, particularly preferably 96.5% or more, and particularly preferably 96.7% or more. ４ The higher the conversion rate, the more preferable, and it is, for example, 98% or less, 99% or less, etc. ４ The conversion rate is more preferably 95% to 99%, further preferably 96% to 99%, particularly preferably 96.5% to 99%, and particularly preferably 96.7% to 98%.

[0065] The CO ２ The conversion rate is more preferably 88% or more, further preferably 89% or more, particularly preferably 90% or more, and especially preferably 90.5% or more. ２ The higher the conversion rate, the more preferable, and it is, for example, 98% or less, 99% or less, etc. ２ The conversion rate is more preferably 88% to 99%, further preferably 89% to 98%, particularly preferably 90% to 99%, and especially preferably 90.5% to 98%.

[0066] The H ２ The selectivity is more preferably 43% or more, further preferably 44% or more, particularly preferably 44.5% or more, and particularly preferably 44.8% or more. ２ The higher the selectivity, the more preferable, and it is, for example, 48% or less, 49% or less, etc. ２The selectivity is more preferably 43% to 49%, further preferably 44% to 49%, particularly preferably 44.5% to 49%, and particularly preferably 44.8% to 48%.

[0067] The CO selectivity is more preferably 40.3% or more, even more preferably 40.4% or more, particularly preferably 40.5% or more, and especially preferably 40.7% or more. The higher the CO selectivity, the better, but it is, for example, 48% or less, 49% or less, etc. The CO selectivity is more preferably 40.3% or more and 49% or less, even more preferably 40.4% or more and 49% or less, particularly preferably 40.5% or more and 49% or less, and especially preferably 40.7% or more and 48% or less.

[0068] The cerium oxide-stabilized zirconium oxide composition was heat-treated under the following heat treatment condition B, and then subjected to CH ４ :CO ２ :N ２ A gas mixture of 4.5:4.5:1 was placed at a space velocity of 8000 h －１ After that, pretreatment was carried out at 200°C for 20 minutes under a He flow. ２ -He (20% by volume O ２ The temperature was raised to 950°C at 10°C / min under a flow of 50 ml / min of He containing ２ The detectable amount is preferably 20 mmol / g or less. ２ A detected amount of 20 mmol / g or less can be said to indicate low carbon deposition. <Heat Treatment Condition B> Nickel oxide is mixed with the composition so that the content is 60 mass %, and the mixture is heat-treated in air at 1300°C for 2 hours to form a cermet.

[0069] The CO ２ The detectable amount is more preferably 17 mmol / g or less, further preferably 16.5 mmol / g or less, particularly preferably 16 mmol / g or less, and especially preferably 15.5 mmol / g or less. ２ The smaller the detectable amount, the more preferable, and it is, for example, 8 mmol / g or more, 5 mmol / g or more, etc. ２The detectable amount is more preferably 5 mmol / g or more and 17 mmol / g or less, even more preferably 5 mmol / g or more and 16.5 mmol / g or less, particularly preferably 5 mmol / g or more and 16 mmol / g or less, and especially preferably 8 mmol / g or more and 15.5 mmol / g or less.

[0070] The cerium oxide-stabilized zirconium oxide composition can be used as a support for supporting a transition metal, and when used as a support for a transition metal, the resulting electrode has higher oxygen ion conductivity and a higher modifying function.

[0071] Examples of the transition metal include Ni, Ti, V, Cr, Mn, Fe, Co, Cu, and Zn. Among these, Ni (nickel) is preferable. When the transition metal is nickel, an electrode formed from nickel has higher oxygen ion conductivity and can have a higher modifying function.

[0072] [Method for producing a cerium oxide-stabilized zirconium oxide composition] An example of a method for producing a cerium oxide-stabilized zirconium oxide composition will be described below, although the method for producing a cerium oxide-stabilized zirconium oxide composition of the present invention is not limited to the following example.

[0073] In the method for producing a cerium oxide-stabilized zirconium oxide composition according to this embodiment, first, a sulfating agent is added to a zirconium salt solution to obtain basic zirconium sulfate (slurry containing basic zirconium sulfate).

[0074] The sulfating agent is not limited as long as it reacts with zirconium ions to produce sulfate (i.e., a sulfating reagent), and examples thereof include sodium sulfate, potassium sulfate, and ammonium sulfate. The sulfating agent may be in any form, such as a powder or a solution, but a solution (particularly an aqueous solution) is preferred. When a solution is used, the concentration of the solution can be appropriately set.

[0075] The free acid concentration in the mixed solution is preferably 0.2 to 2.2 N (normal). Examples of free acids include sulfuric acid, nitric acid, and hydrochloric acid. There are no limitations on the type of free acid, but hydrochloric acid is preferred because of its high productivity on an industrial scale.

[0076] The zirconium salt may be any salt capable of supplying zirconium ions, such as zirconium oxynitrate, zirconium oxychloride, zirconium nitrate, etc. These may be used alone or in combination of two or more.

[0077] The solvent for preparing the zirconium salt solution may be selected depending on the type of zirconium salt, and water (pure water or ion-exchanged water) is usually preferred.

[0078] The concentration of the zirconium salt solution is not particularly limited, but generally, zirconium oxide (ZrO ２ It is desirable that the amount of the soluble fiber contained in the water is 5 to 250 g (particularly 20 to 150 g).

[0079] The sulfating agent to be added is sulfate ion (SO ４ ２－ ) / ZrO ２ It is preferable to add them so that the weight ratio is 0.3 or more and 0.7 or less.

[0080] Next, before the neutralization step described below, a salt solution or compound of one or more metals selected from the group consisting of cerium, scandium, yttrium, and ytterbium is added to the basic zirconium sulfate (slurry containing basic zirconium sulfate) so as to have a composition represented by the following formula [1]: (ZrO ２ ) １－ｘ－ｙ (CeO ２ ) ｘ (M ２ O ３ ) ｙ [1] However, in formula [1], x and y are numbers that satisfy 0.10≦x≦0.40 and 0.02≦y≦0.12, and M is one or more elements selected from the group consisting of scandium, yttrium, and ytterbium.

[0081] Next, the basic zirconium sulfate is neutralized to produce zirconium hydroxide. Specifically, zirconium hydroxide is produced by neutralizing the basic zirconium sulfate with an alkali. The alkali is not limited, and examples that can be used include ammonium hydroxide, ammonium bicarbonate, sodium hydroxide, and potassium hydroxide. Among these, sodium hydroxide is preferred from the viewpoint of industrial cost.

[0082] The amount of alkali to be added is not particularly limited as long as it can produce zirconium hydroxide as a precipitate from the basic zirconium sulfate solution. Usually, the alkali is added so that the pH of the solution becomes 11 or higher, preferably 12 or higher.

[0083] After the neutralization reaction, the zirconium hydroxide-containing solution is preferably kept at 35 to 60° C. for at least 1 hour, which allows the produced precipitate to mature and makes it easier to filter.

[0084] Next, the zirconium hydroxide is recovered by solid-liquid separation, such as filtration, centrifugation, or decantation.

[0085] After the zirconium hydroxide is recovered, it is preferable to wash the zirconium hydroxide with water to remove any adhering impurities.

[0086] The zirconium hydroxide may be dried by natural drying or by heating.

[0087] Next, the zirconium hydroxide is heat-treated (calcined) to obtain a cerium oxide-stabilized zirconium oxide composition. The heat treatment temperature is preferably 800°C or higher, more preferably 900°C or higher. The heat treatment temperature is preferably 1300°C or lower, more preferably 1200°C or lower. The heat treatment temperature is preferably 800°C or higher and 1300°C or lower, more preferably 900°C or higher and 1200°C or lower. The heat treatment time is preferably 1 hour or higher, more preferably 2 hours or higher. The heat treatment time is preferably 10 hours or lower, more preferably 6 hours or lower. The heat treatment time is preferably 1 hour or higher and 10 hours or lower, more preferably 2 hours or higher and 6 hours or lower. By setting the heat treatment temperature and heat treatment time within the above numerical ranges, it is possible to suitably increase the specific surface area to 5 m ２ / g or more 20m ２ The heat treatment atmosphere is preferably air or an oxidizing atmosphere.

[0088] The resulting cerium oxide-stabilized zirconium oxide composition may be subjected to a treatment to deflocculate the agglomerates, if necessary, for the purpose of improving handling properties.

[0089] The method for producing a cerium oxide-stabilized zirconium oxide composition according to this embodiment has been described above.

[0090] The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. Note that the cerium oxide-stabilized zirconium compositions obtained in the examples and comparative examples contain 1 to 3 mass % of hafnium as an unavoidable impurity relative to zirconium (calculated using the following formula (X)). <Formula (X)> ([mass of hafnium] / ([mass of zirconium]+[mass of hafnium])×100(%)

[0091] The maximum and minimum values ​​of the content of each component shown in the following examples should be considered as the preferred minimum and maximum values ​​of the present invention, regardless of the content of other components. Also, the maximum and minimum values ​​of the measured values ​​shown in the following examples should be considered as the preferred minimum and maximum values ​​of the present invention, regardless of the content (composition) of each component.

[0092] [Preparation of Cerium Oxide-Stabilized Zirconium Oxide Composition] (Example 1) ZrO ２ 623 g of a 16 mass% aqueous solution of zirconium oxychloride and 805 g of a 25 mass% aqueous solution of sodium sulfate were mixed and heated to 96°C to obtain basic zirconium sulfate. ２ ) ０．８８ (CeO ２ ) ０．１０ (Sc ２ O ３ ) ０．０２ CeO ２ 79 g of a 20 wt% aqueous solution of cerium chloride and Sc ２ O ３25 g of a 10 mass % scandium chloride aqueous solution was added and mixed uniformly. Next, 500 g of a 25 mass % sodium hydroxide aqueous solution was added to the resulting mixed solution so that the pH was 13 or higher, producing a hydroxide precipitate. The resulting hydroxide precipitate was subjected to solid-liquid separation and washed with water. Next, the hydroxide was fired in an electric furnace at 1095°C in air for 5 hours. The resulting oxide was pulverized and dispersed in a wet ball mill, and the resulting slurry was dried at 120°C to obtain a cerium oxide-stabilized zirconium oxide composition according to Example 1.

[0093] (Example 2) The composition is (ZrO ２ ) ０．８５ (CeO ２ ) ０．１０ (Sc ２ O ３ ) ０．０５ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0094] (Example 3) Composition: (ZrO ２ ) ０．８２ (CeO ２ ) ０．１０ (Sc ２ O ３ ) ０．０８ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0095] (Example 4) Composition: (ZrO ２ ) ０．８０ (CeO ２ ) ０．１０ (Sc ２ O ３ ) ０．１０ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0096] (Example 5) Composition: (ZrO ２ ) ０．７８ (CeO ２ ) ０．１０ (Sc ２ O ３ ) ０．１２ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0097] (Example 6) Composition: (ZrO ２ ) ０．７８ (CeO ２ ) ０．２０ (Sc ２ O ３ ) ０．０２ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0098] (Example 7) Composition: (ZrO ２ ) ０．７５ (CeO ２ ) ０．２０ (Sc ２ O ３ ) ０．０５ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0099] (Example 8) Composition: (ZrO ２ ) ０．７２ (CeO ２ ) ０．２０ (Sc ２ O ３ ) ０．０８ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0100] (Example 9) Composition: (ZrO ２ ) ０．７０ (CeO ２ ) ０．２０ (Sc ２ O ３ ) ０．１０ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0101] (Example 10) Composition: (ZrO ２ ) ０．６８ (CeO ２ ) ０．２０ (Sc ２ O ３ ) ０．１２ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0102] (Example 11) Composition: (ZrO ２ )０．６８ (CeO ２ ) ０．３０ (Sc ２ O ３ ) ０．０２ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0103] (Example 12) Composition: (ZrO ２ ) ０．６５ (CeO ２ ) ０．３０ (Sc ２ O ３ ) ０．０５ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0104] (Example 13) Composition: (ZrO ２ ) ０．６２ (CeO ２ ) ０．３０ (Sc ２ O ３ ) ０．０８ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0105] (Example 14) Composition: (ZrO ２ ) ０．６０ (CeO ２ ) ０．３０ (Sc ２ O ３ ) ０．１０ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0106] (Example 15) Composition: (ZrO ２ ) ０．５８ (CeO ２ ) ０．３０ (Sc ２ O ３ ) ０．１２ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0107] (Example 16) Composition: (ZrO ２ ) ０．５８ (CeO ２ ) ０．４０ (Sc２ O ３ ) ０．０２ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0108] (Example 17) Composition: (ZrO ２ ) ０．５５ (CeO ２ ) ０．４０ (Sc ２ O ３ ) ０．０５ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0109] (Example 18) Composition: (ZrO ２ ) ０．５２ (CeO ２ ) ０．４０ (Sc ２ O ３ ) ０．０８ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0110] (Example 19) Composition: (ZrO ２ ) ０．５０ (CeO ２ ) ０．４０ (Sc ２ O ３ ) ０．１０ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0111] (Example 20) Composition: (ZrO ２ ) ０．４８ (CeO ２ ) ０．４０ (Sc ２ O ３ ) ０．１２ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0112] (Example 21) Composition: (ZrO ２ ) ０．８２ (CeO ２ ) ０．１０ (Y ２ O ３ ) ０．０８The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0113] (Example 22) Composition: (ZrO ２ ) ０．８１５ (CeO ２ ) ０．１２５ (Y ２ O ３ ) ０．０６ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0114] (Example 23) Composition: (ZrO ２ ) ０．７１ (CeO ２ ) ０．２５ (Y ２ O ３ ) ０．０４ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0115] (Example 24) Composition: (ZrO ２ ) ０．８２ (CeO ２ ) ０．１０ (Yb ２ O ３ ) ０．０８ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0116] (Example 25) Composition: (ZrO ２ ) ０．７５ (CeO ２ ) ０．２０ (Yb ２ O ３ ) ０．０５ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0117] (Comparative Example 1) The composition was (ZrO ２ ) ０．８９ (CeO ２ ) ０．０１ (Sc ２ O ３ ) ０．１０ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0118] (Comparative Example 2) The composition was changed to (ZrO ２ ) ０．９２ (Y ２ O ３ ) ０．０８ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0119] (Comparative Example 3) The composition was changed to (ZrO ２ ) ０．６８ (CeO ２ ) ０．２０ (Sc ２ O ３ ) ０．１２ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0120] (Comparative Example 4) The composition was changed to (ZrO ２ ) ０．６８ (CeO ２ ) ０．２０ (Sc ２ O ３ ) ０．１２ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0121] (Comparative Example 5) The composition was changed to (ZrO ２ ) ０．５０ (CeO ２ ) ０．５０ The same treatment as in Example 1 was carried out except that the firing temperature was changed as shown in Table 1.

[0122] [Measurement of Specific Surface Area] The specific surface areas of the cerium oxide-stabilized zirconium oxide compositions of the Examples and Comparative Examples were measured by the BET method using a specific surface area meter ("Macsorb" manufactured by Mountec). The results are shown in Table 1.

[0123] [Measurement of oxygen absorption / desorption capacity at 750°C] The cerium oxide-stabilized zirconium oxide compositions of the Examples and Comparative Examples were subjected to 5% H ２ After reduction treatment at 750°C for 10 minutes under a flow of O ２ The oxygen storage capacity (OSC) was calculated from the amount consumed by pulse introduction. The results are shown in Table 1.

[0124] [Measurement of Electrical Conductivity at 700°C] The cerium oxide-stabilized zirconium oxide compositions of the Examples and Comparative Examples were subjected to cold isostatic pressing at 1.0 t / cm ２ The sintered samples were molded at a pressure of 0.15 for 2 minutes, and then heat-treated in an electric furnace at 1450°C for 2 hours in the atmosphere to obtain sintered samples for measurement. The electrical conductivity of the sintered samples was measured using a four-terminal method with a Solartron Analytical SI1287. The electrical conductivity was measured in an electric furnace maintained at 700°C. The results are shown in Table 1.

[0125] [Measurement of Electrical Conductivity at 800° C.] The electrical conductivity of the sintered sample was measured in the same manner as in "Measurement of Electrical Conductivity at 700° C.," except that the measurement was carried out in an electric furnace maintained at 800° C. The results are shown in Table 1.

[0126] [Measurement of Electrical Conductivity at 900° C.] The electrical conductivity of the sintered sample was measured in the same manner as in "Measurement of Electrical Conductivity at 700° C.," except that the measurement was carried out in an electric furnace maintained at 900° C. The results are shown in Table 1.

[0127] [Evaluation of sintering characteristics] Stabilized zirconia containing 10 mol % of Sc and 1 mol % of Ce (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was mixed with 15 mass % of PVB (polyvinyl butyral) and 15 mass % of a phthalate ester, and ethanol was added to adjust the concentration of the stabilized zirconia solids to 60 mass %. The mixture was slurried in a ball mill and then cast into a green sheet.

[0128] The cerium oxide-stabilized zirconium oxide compositions of the Examples and Comparative Examples, 15% by mass of PVB and 15% by mass of phthalate ester relative to the cerium oxide-stabilized zirconium oxide, were mixed onto the resulting green sheet, and ethanol was added to adjust the solids concentration of the cerium oxide-stabilized zirconium oxide to 60% by mass. The mixture was slurried using a ball mill and cast onto the green sheet. The resulting sheet was degreased in an electric furnace at 500°C for 2 hours in air. This was followed by heat treatment in an electric furnace at 1450°C for 2 hours in air to obtain a sintered body. The resulting sintered body was visually inspected for defects, including cracks and peeling. A rating of ∘ indicates no cracks or peeling, and a rating of × indicates the presence of either cracks or peeling, or both. The results are shown in Table 1. The cerium oxide-stabilized zirconium oxide compositions of the Examples and Comparative Examples were formed onto green sheets to evaluate their sintering properties, in order to simulate the fabrication of electrodes.

[0129]

[0130] [CH ４ Conversion, CO ２ Conversion rate, H ２ Measurement of selectivity and CO selectivity] Nickel oxide was mixed with the cerium oxide-stabilized zirconium oxide compositions of Examples and Comparative Examples to a content of 60 mass %, and the mixture was heat-treated in air at 1,300°C for 2 hours to form a cermet. A quartz tube (inner diameter: 7 mm) filled with the obtained cermet sample was heated to 800°C, and CH ４ =22.5ml / min, CO ２ =22.5ml / min, N ２ = 5 ml / min mixed gas (volume ratio: CH ４ :CO ２ :N ２ = 4.5:4.5:1 mixed gas) at a space velocity of 8000 h －１ The gas that passed through the cermet sample was analyzed by gas chromatography. ４ Conversion, CO ２ Conversion rate, H ２ The selectivity and CO selectivity were calculated. The results are shown in Table 2. ４ Conversion rate (%) = [(introduced CH４ flow rate) - (outlet side CH ４ flow rate)] / [introduction CH ４ Flow rate]]×100 [CO ２ Conversion rate (%) = [(introduced CO ２ flow rate) - (outlet side CO ２ flow rate)] / [introduced CO ２ Flow rate]]×100 [H ２ Selection rate (%)] = [(exit side H ２ flow rate) / [2×[[(introduction CH ４ flow rate) - (outlet side CH ４ flow rate)] + [(introduced CO ２ flow rate) - (outlet side CO ２ Flow rate)]]]]×100 [CO selectivity (%)]=[(Outlet side CO flow rate) / [2×[[(Introduction CH ４ flow rate) - (outlet side CH ４ flow rate)] + [(introduced CO ２ flow rate) - (outlet side CO ２ flow rate)]]]]×100

[0131] [CO ２ Measurement of detection amount] ４ Conversion, CO ２ Conversion rate, H ２ The cermet sample used in the "Measurement of CO selectivity and CO selectivity" was pretreated at 200°C for 20 minutes in a He flow, and then 20% O ２ -He (20% by volume O ２ The temperature was raised to 950°C at 10°C / min under a flow of 50 ml / min of He containing ２ The amount detected was calculated. The results are shown in Table 2. ４ Conversion, CO ２ Conversion rate, H ２ In the "measurement of selectivity and CO selectivity", the mixed gas was passed through for two hours.

[0132]

Claims

1. A composition represented by the following formula [1] and a specific surface area of ​​5 m ２ / g or more 20m ２ / g or less. ２ ) １－ｘ－ｙ (CeO ２ ) ｘ (M ２ O ３ ) ｙ [1] However, in the formula [1], x and y are numbers satisfying 0.10≦x≦0.40 and 0.02≦y≦0.12, and M is one or more elements selected from the group consisting of scandium, yttrium, and ytterbium.

2. The cerium oxide-stabilized zirconium composition of claim 1, wherein M is one selected from the group consisting of scandium, yttrium, and ytterbium.

3. The cerium oxide stabilized zirconium composition of claim 1, wherein M is scandium.

4. A cerium oxide-stabilized zirconium composition according to any one of claims 1 to 3, characterized in that the x and y are numbers satisfying 0.10≦x≦0.30 and 0.06≦y≦0.

10.

5. A cerium oxide-stabilized zirconium oxide composition according to any one of claims 1 to 3, characterized in that the y is a number satisfying 0.08≦y≦0.

10.

6. Oxygen absorption / release capacity at 750℃ is 5μmol / m ２ The cerium oxide-stabilized zirconium oxide composition according to any one of claims 1 to 3, characterized in that 7. After heat treatment under the following heat treatment condition A, the electrical conductivity at 700°C is 9.0 x 10 －４ The cerium oxide-stabilized zirconium oxide composition according to any one of claims 1 to 3, characterized in that the composition has a hardness of 1.0 t / cm or more by using a cold isostatic pressing method. ２ After molding at this pressure for 2 minutes, the mixture is heat-treated in air at 1450° C. for 2 hours.

8. After heat treatment under the following heat treatment condition A, the electrical conductivity at 800°C is 3.0 x 10 －３ The cerium oxide-stabilized zirconium oxide composition according to any one of claims 1 to 3, characterized in that the composition has a hardness of 1.0 t / cm or more by using a cold isostatic pressing method. ２ After molding at this pressure for 2 minutes, the mixture is heat-treated in air at 1450° C. for 2 hours.

9. After heat treatment under the following heat treatment condition A, the electrical conductivity at 900°C is 7.5 x 10 －３ The cerium oxide-stabilized zirconium oxide composition according to any one of claims 1 to 3, characterized in that the composition has a hardness of 1.0 t / cm or more by using a cold isostatic pressing method. ２ After molding at this pressure for 2 minutes, the mixture is heat-treated in air at 1450° C. for 2 hours.

10. The cerium oxide-stabilized zirconium oxide composition according to any one of claims 1 to 3, which is used as a support for supporting a transition metal.

11. The cerium oxide stabilized zirconium oxide composition of claim 10, wherein said transition metal is nickel.

12. After heat treatment under the following heat treatment condition B, CH ４ :CO ２ :N ２ = 4.5:4.5:1 mixed gas at a space velocity of 8000 h －１ CH when distributed in ４ Conversion rate is 90% or more, CO ２ Conversion rate is 85% or more, H ２ The cerium oxide-stabilized zirconium oxide composition according to any one of claims 1 to 3, characterized in that the selectivity is 40% or more and the CO selectivity is 40% or more. <Heat treatment condition B> Nickel oxide is mixed into the composition so that the content is 60 mass%, and the composition is heat-treated in air at 1,300°C for 2 hours to form a cermet.

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