Tin co-doped mixed oxide for use in three-way catalysis

Abstract

The present disclosure provides a catalyst composition comprising a mixed oxide support material and a platinum group metal supported on the mixed oxide support material, wherein the mixed oxide support material is of the formula Ce w Zr x Sn y M z O a and comprises a solid solution mixed oxide having the formula, where 0.05 ≦ w ≦ 0.90, 0.05 ≦ x ≦ 0.90, 0.001 ≦ y ≦ 0.25, 0.001 ≦ z ≦ 0.60, w + x + y + z = 1.00, 1.0 ≦ a ≦ 2.0, and M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium, and ytterbium. 【Number 1】 JPEG2025519992000009.jpg7128

Description

[Technical field]

[0001] The present invention relates to a catalyst composition, a catalyst article, an emission treatment system, a vehicle, a method for treating exhaust gases, as well as a solid solution mixed oxide, a method for producing a solid solution mixed oxide, a method for producing a catalyst composition, and the use of the catalyst composition or the catalyst article. [Background technology]

[0002] Three-way catalysts (TWCs) are used to separate CO, HC, and NO from the exhaust of gasoline engines at a stoichiometric air-fuel ratio. x to harmless compounds (about 98%). Specifically, the oxidation of CO and HC to CO2 and water vapor (HO) is primarily catalyzed by Pd, while NO x The reduction of N2 to N2 is primarily catalyzed by Rh. Modern TWCs use supported platinum group metal (PGM) catalysts (Pd, Rh, Pt, etc.) deposited on single, bi- or multi-layer supports, with the support material consisting of high surface area metal oxides, primarily stabilized alumina, and ceria-containing oxygen storage materials. The supported catalysts are washcoated onto ceramic monolith substrates.

[0003] Ce 4+ / Ce 3+ Cerium oxide (CeO) is known for its high oxygen storage capacity (OSC) due to its redox couple function. x O y ) plays an important role in TWC performance. Ce x O y In addition to providing a high surface area for PGM metal dispersion, Ce can also assist in the feedback control of stoichiometric conditions by capturing or donating oxygen during fuel lean / rich perturbation. x O y When zirconium oxide (ZrO2) is incorporated into the fluorite structure (denoted as CZO, i.e. ceria-zirconia mixed oxide), Cex O y The thermal stability of O is improved, and the mobility of lattice oxygen is improved by the formation of oxygen vacancies.

[0004] It is known that doping a mixed oxide such as a ceria-zirconia mixed oxide with tin can improve the OSC characteristics of the mixed oxide. For example, U.S. Patent No. 2021 / 0299647(A1) relates to doping a ceria-zirconia mixed oxide with tin oxide. However, doping a mixed oxide with tin typically results in a crystal structure that is not particularly stable against phase separation of the mixed oxide(s), especially at high temperatures.

[0005] There is still a need to provide a tin-doped mixed oxide for use in TWC applications that provides improved OSC characteristics and remains more stable, especially at the high temperatures experienced by TWC during use, for example, to treat emissions from gasoline engines. SUMMARY OF THE INVENTION

[0006] One aspect of the present disclosure is a catalyst composition comprising a mixed oxide support material and a platinum group metal supported on the mixed oxide support material, wherein the mixed oxide support material has the formula Ce w Zr x Sn y M z O aRegarding a catalyst composition comprising a solid solution mixed oxide having the formula: where 0.05 ≦ w ≦ 0.90, 0.05 ≦ x ≦ 0.90, 0.001 ≦ y ≦ 0.25, 0.001 ≦ z ≦ 0.60, w + x + y + z = 1.00, 1.0 ≦ a ≦ 2.0, and M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium, and ytterbium.

[0007] Another aspect of the present disclosure relates to a catalyst article comprising a substrate and the catalyst composition of the above aspect, wherein the catalyst composition is disposed on the substrate.

[0008] Another aspect of the present disclosure relates to an exhaust treatment system comprising the catalyst article of the above aspect.

[0009] Another aspect of the present disclosure relates to a vehicle comprising the exhaust treatment system of the above aspect.

[0010] Another aspect of the present disclosure relates to a method of treating exhaust gas, the method comprising providing the catalyst article of the above aspect and contacting the catalyst article with the exhaust gas.

[0011] Another aspect of the present disclosure is the formula Ce w Zr x Sn y M z O aRegarding a solid solution mixed oxide having the formula: where 0.05 ≦ w ≦ 0.90, 0.05 ≦ x ≦ 0.90, 0.001 ≦ y ≦ 0.25, 0.001 ≦ z ≦ 0.60, w + x + y + z = 1.00, 1.0 ≦ a ≦ 2.0, and M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium, and ytterbium.

[0012] Another aspect of the present disclosure is a method for manufacturing the solid solution mixed oxide of the above aspect, comprising providing a solution containing the respective cations of Ce, Zr, Sn, and M, contacting the solution with a base to provide a slurry, heating the slurry at a temperature of 20 to 200 °C to provide a mixed oxide precursor, and heating the mixed oxide precursor at a temperature above 450 °C to provide a solid solution mixed oxide.

[0013] Another aspect of the present disclosure is a method for manufacturing the catalyst composition of the above aspect, comprising providing a solid solution mixed oxide according to the above aspect or manufacturing a solid solution mixed oxide by the method of the above aspect, and disposing a platinum group metal on the solid solution mixed oxide.

[0014] Another aspect of the present disclosure relates to the use of the catalyst composition of the above aspect or the catalyst article of the above aspect in an exhaust treatment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015]

Figure 1

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Mode for Carrying Out the Invention

[0016] The present invention aims to address at least some of the problems associated with the prior art or to provide at least a commercially acceptable alternative solution.

[0017] In a first aspect, the present invention provides a catalyst composition comprising a mixed oxide support material and a platinum group metal supported on the mixed oxide support material, wherein the mixed oxide support material comprises a solid solution mixed oxide having the formula Ce w Zr x Sn y M z O a wherein, 0.05 ≦ w ≦ 0.90, 0.05 ≦ x ≦ 0.90, 0.001 ≦ y ≦ 0.25, 0.001 ≦ z ≦ 0.60, w + x + y + z = 1.00, 1.0 ≦ a ≦ 2.0, M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium and ytterbium.

[0018] Each aspect or embodiment defined herein may be combined with any other aspect(s) or embodiment(s) unless otherwise explicitly indicated. Specifically, any feature shown to be preferred or advantageous may be combined with any other feature shown to be preferred or advantageous.

[0019] Surprisingly, compared to conventional catalyst compositions, particularly those containing a CZO support material, the catalyst compositions of the present invention can exhibit improved OSC characteristics when used, for example, as a TWC, while remaining more thermally stable against phase separation. Thus, the catalyst compositions can maintain their high OSC activity for a longer time during use.

[0020] Without being bound by theory, it is believed that tin can provide improved OSC characteristics by a mechanism similar to that of ceria, i.e., through the function of the Sn 2+ / Sn 4+ redox pair.

[0021] Furthermore, without being bound by theory, the lack of stability against phase separation of known tin-doped mixed oxides may be, at least in part, due to the fact that the cation radius of tin (i.e., Sn 4+ ) and / or cerium (i.e., Ce 3+ or Ce 4+ ) is smaller compared to the cation radius of zirconium (i.e., Zr 2+ or Sn 4+ ). Thus, in the fluorite lattice structure, the distance between tin ions and oxygen ions may be larger, for example, compared to the distance between zirconium ions and oxygen ions. Therefore, this can cause an enthalpy bond strain. In other words, the Sn-O "bond" may be weaker than, for example, the Zr-O "bond" in the crystal lattice. Thus, due to the presence of tin in the lattice causing bond strain, the mixed oxide may be more likely to phase separate due to the balance of the enthalpy contribution and entropy contribution of the Gibbs free energy of the phase separation reaction that favors phase separation.

[0022] However, the inventors of the present invention have surprisingly found that further co-doping the tin-doped CZO with a larger cation (i.e., larger than tin and typically larger than cerium and / or zirconium) can result in a more stable crystal lattice while also benefiting from the improved OSC properties introduced by tin. Thus, when a solid solution mixed oxide is used as a carrier material in a catalyst composition as in the present invention, advantageous catalyst properties, particularly advantageous catalyst properties for TWC applications, can surprisingly be shown.

[0023] Although not bound by theory, the introduction of these larger cations is thought to provide at least the following two advantages: (i) the lattice binding strain can be reduced due to the balance between the larger and smaller cations, reducing the impact of tin-only inclusion on the enthalpy contribution to the Gibbs free energy, and (ii) the inclusion of one or more additional cations can increase the disorder in the mixed oxide lattice, thereby making the entropy contribution to the Gibbs free energy less favorable for phase separation. Thus, surprisingly, it may be possible to provide a mixed oxide that is more stable, especially at high temperatures, while still providing improved OSC properties. This is advantageous in emission treatment applications, particularly in TWC applications.

[0024] Thus, advantageously, the solid solution mixed oxides of the present invention can be used in place of existing carrier materials, such as when CZO is used as a carrier material in known catalyst compositions, and can provide the catalyst with further and / or improved OSC properties while remaining relatively stable against phase separation during use. The mixed oxides can also provide a high OSC over the entire temperature range of typical operating temperatures.

[0025] As used herein, the term "carrier material" can include any known carrier material that can typically be used in powder form to support PGM in the field of the present invention. However, the carrier material of the present invention is the mixed oxide carrier material according to the appended "claims".

[0026] As used herein, the term "mixed oxide" can include oxides containing two or more chemical elements, for example, in this case, cations of at least Ce, Zr, Sn, and M. The mixed oxide can be, for example, single-phase.

[0027] Ce of the present invention w Zr x Sn y M z O ais typically crystalline. Preferably, the mixed oxide is crystalline. As used herein, the term "crystalline" is used within the scope of its ordinary meaning in the art and may include solid materials having long-range order, i.e., periodic translational order of atoms or molecules within the solid.

[0028] As used herein, the term "platinum group metal" or "PGM" may include one or more elements selected from ruthenium, rhodium, palladium, osmium, iridium, and platinum. Preferably, the PGM comprises platinum, palladium, rhodium, or mixtures or alloys thereof. Such metals may be particularly suitable for performing three-way catalysis. The PGM may be in the form of an alloy.

[0029] As used herein, the term "supported thereon" may include that the PGM is in direct contact with and stably disposed on the mixed oxide support material either on the surface and / or within the pores of the mixed oxide support material.

[0030] As used herein, the term "solid solution" may include, for example, a mixture of two crystalline solids coexisting as a new crystalline solid or crystal lattice. In other words, the mixed oxide is typically not a mixture of different phases but is substantially one phase. Preferably, the solid solution mixed oxide is at least 95% phase pure, more preferably at least 97% phase pure, even more preferably at least 99% phase pure, and still more preferably completely phase pure, allowing for the presence of unavoidable impurities. As used herein, the term "phase pure" includes that the solid solution mixed oxide contains only one type of crystal structure. The level of phase purity can be measured, for example, by X-ray diffraction. Those skilled in the art know appropriate techniques, for example, by using the Rietveld method of X-ray powder diffraction patterns. Preferably, the main phase of the solid solution mixed oxide is fluorite. Those skilled in the art will be able to identify the X-ray diffraction pattern of fluorite.

[0031] In the catalyst composition of the present invention, 1.0 ≦ a ≦ 2.0, preferably 1.3 ≦ a ≦ 2.0, more preferably 1.5 ≦ a ≦ 2.0, even more preferably 1.6 ≦ a ≦ 2.0, and most preferably "a" is about 2. "a" can typically be about 2, but the amount of oxygen present in the solid solution mixed oxide can vary between these amounts, for example, due to changes in the oxidation state of the cations. As described herein, for example, cerium can change between the Ce III oxidation state and Ce IV oxidation state, and tin can change between the Sn II oxidation state and Sn IV oxidation state. Therefore, the relative amount of oxygen can consequently change. Without being bound by theory, it is believed that the variations in oxygen and oxidation state should not substantially affect the crystal structure of the mixed oxide.

[0032]

Number

[0033] wherein b is the mole fraction of cations in the 3+ oxidation state excluding the molar contribution of O, c is the mole fraction of cations in the 2+ oxidation state excluding the molar contribution of O, and d is the mole fraction of cations in the 1+ oxidation state excluding the molar contribution of O.

[0034] M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium and ytterbium. When M is two or more of the listed elements, it should be understood that the total amount of M is encompassed by the "z" parameter. In other words, for example, M z is A z1 B z2 C z3 and in the formula, when A, B and C are each one of the listed elements, the parameter "z" encompasses z1 + z2 + z3, that is, in this case z = z1 + z2 + z3. Each of the listed elements can contribute to the stabilization of the mixed oxide, for example, due to their large cations as assumed above.

[0035] Preferably, the catalyst composition is for three-way catalysis. In other words, the catalyst composition can preferably catalyze at least one of the target reactions of a TWC. Preferably, the catalyst composition is a TWC.

[0036] In some preferred embodiments, y + z is less than 0.15, preferably 0.13 or less, more preferably 0.11 or less, even more preferably 0.10 or less, and even more preferably about 0.10. Such a balance of the components of the mixed oxide can provide a catalyst composition having particularly stable and excellent OSC characteristics.

[0037] In an alternative preferred embodiment, 0.05 ≦ y ≦ 0.15, more preferably 0.07 ≦ y ≦ 0.13, even more preferably 0.08 ≦ y ≦ 0.12. In an alternative preferred embodiment, 0.05 ≦ y ≦ 0.10. In another alternative preferred embodiment, 0.10 ≦ y ≦ 0.15. Preferably, y is 0.005 or more, more preferably 0.01 or more, even more preferably 0.02 or more, and even more preferably 0.05 or more. Such an amount of tin doping can result in a catalyst composition that is particularly stable and has excellent catalytic properties.

[0038] In an alternative preferred embodiment, 0.05 ≦ z ≦ 0.15, more preferably 0.07 ≦ z ≦ 0.13, even more preferably 0.08 ≦ z ≦ 0.12. In an alternative preferred embodiment, 0.05 ≦ z ≦ 0.10. In another alternative preferred embodiment, 0.10 ≦ z ≦ 0.15. Preferably, z is 0.005 or more, more preferably 0.01 or more, even more preferably 0.02 or more, and even more preferably 0.05 or more. Such an amount of tin doping can result in a catalyst composition that is particularly stable and has excellent catalytic properties.

[0039] Preferably, w + x is 0.80 or more, preferably 0.85 or more, more preferably 0.90 or more. For example, preferably 0.80 ≦ w + x ≦ 0.95, more preferably 0.85 ≦ w + x ≦ 0.95, and even more preferably 0.85 ≦ w + x ≦ 0.90. Such a balance of the components of the mixed oxide can provide a catalyst composition having particularly stable and excellent OSC properties.

[0040] Preferably, w + y is more than 0.5, preferably 0.51 or more, even more preferably 0.55 or more, and even more preferably 0.60 or more. Such a balance of the components of the mixed oxide can provide a catalyst composition having particularly stable and excellent OSC properties.

[0041] Preferably, 0.07 ≦ y ≦ 0.11, and more preferably, 0.07 ≦ y + z ≦ 0.11. Such a balance of the components of the mixed oxide can provide a catalyst composition having particularly stable and excellent OSC characteristics.

[0042] Preferably, 0.20 ≦ w ≦ 0.80, more preferably, 0.30 ≦ w ≦ 0.70, still more preferably, 0.40 ≦ w ≦ 0.60, and even more preferably, 0.50 ≦ w ≦ 0.60. Such a balance of the components of the mixed oxide can provide a catalyst composition having particularly stable and excellent OSC characteristics.

[0043] In some preferred embodiments, M contains two or more different elements. In other words, in such preferred embodiments, there are five or more different cations present in the solid solution mixed oxide. As described above, having a larger number of different cations can contribute to the entropy component of the Gibbs free energy for phase separation and make phase separation less favorable. Thus, a catalyst composition that is particularly stable and has excellent OSC characteristics can be provided.

[0044] In some preferred embodiments, 0.15 ≦ w, x ≦ 0.25 and 0.30 ≦ y + z ≦ 0.70. The term "0.15 ≦ w, x ≦ 0.25" means satisfying both 0.15 ≦ w ≦ 0.25 and 0.15 ≦ x ≦ 0.25. In other words, in some embodiments, it is preferred that the molar ratios of each cation in the solid solution mixed oxide are substantially equal. In this embodiment, it may also be preferred that 0.15 ≦ y ≦ 0.25 and / or 0.30 ≦ z ≦ 0.50. Preferably, 0.17 ≦ w, x ≦ 0.23, more preferably, 0.19 ≦ w, x ≦ 0.21. Preferably, 0.40 ≦ y + z ≦ 0.60. Such a balance of the components of the mixed oxide can provide a catalyst composition having particularly stable and excellent OSC characteristics. In the preferred embodiments of this paragraph, M z is M' z1 M'' z2 is even more preferred, where 0.15 ≤ z1 ≤ 0.25, 0.15 ≤ z2 ≤ 0.25, M’ is an element selected from one of calcium, strontium, barium, scandium, yttrium, hafnium, lanthanum, praseodymium, neodymium, samarium, europium, or gadolinium, M’’ is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium, and ytterbium, M’ is different from M’’. To avoid misunderstanding, it should be understood that in this embodiment, z = z1 + z2 as described elsewhere in this specification. Such a balance of the components of the mixed oxide can provide a catalyst composition having particularly stable and excellent OSC characteristics.

[0045] Preferably, M’ is yttrium. In an alternative preferred embodiment, M’ is lanthanum. In an alternative preferred embodiment, M’ is neodymium. In an alternative preferred embodiment, M’ is strontium. Such a mixed oxide can result in a catalyst composition having particularly stable and excellent OSC characteristics.

[0046] Preferably, M’’ contains only one element. Thus, the cations of the mixed oxide can preferably consist of five different elements.

[0047] Preferably, 0.17 ≦ z1 ≦ 0.23 and / or 0.17 ≦ z2 ≦ 0.23, more preferably 0.19 ≦ z1 ≦ 0.21 and / or 0.19 ≦ z2 ≦ 0.21. Such a balance of the components of the mixed oxide can provide a catalyst composition having particularly stable and excellent OSC characteristics.

[0048] In some preferred embodiments, M does not contain lanthanum. In some preferred embodiments, M does not contain yttrium. In some preferred embodiments, M contains neither lanthanum nor yttrium.In other words, in some preferred embodiments, M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium, and ytterbium. In some preferred embodiments, M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium, and ytterbium. Or, in a preferred embodiment, M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium, and ytterbium.

[0049] In a preferred embodiment described herein where 0.15 ≦ w, x ≦ 0.25 and 0.30 ≦ y + z ≦ 0.70, the average cationic radius of Ce, Zr, Sn and M in the solid solution mixed oxide is preferably 90 to 106 pm. However, this preferred feature may also be applicable to all aspects described herein. The average cationic radius can be determined by the 8 - coordinate effective ionic radius (defined in R.D. Shannon, Acta Cryst., 1976, A32, 751). The determination of such cationic radius is well - known in the art. It should be noted that the average cationic radius of Ce, Zr, Sn and M cations in the solid solution mixed oxide is weighted with respect to the molar amounts of the cations in the solid solution mixed oxide. In other words, the "average cationic radius of Ce, Zr, Sn and M in the solid solution mixed oxide" defined is wR Ce +xR Zr +yR Sn +zR M and can be defined as, where R A is the 8 - coordinate effective ionic radius of element A in the oxidation state present in the solid solution mixed oxide. Preferably, the average cationic radius of Ce, Zr, Sn and M in the solid solution mixed oxide is 92 to 98 pm, more preferably 93 to 97 pm. Alternatively, the average cationic radius of Ce, Zr, Sn and M in the solid solution mixed oxide is preferably 90 to 106 pm, more preferably 90 to 100 pm, even more preferably 92 to 98 pm or 93 to 97 pm. Such a balance of the components of the mixed oxide can provide a catalyst composition having particularly stable and excellent OSC properties.

[0050] Preferably, M is an element selected from one or more of calcium, strontium, barium, scandium, yttrium, hafnium, lanthanum, praseodymium, neodymium, samarium, europium, and gadolinium, and more preferably, M is an element selected from one or more of calcium, strontium, barium, yttrium, lanthanum, neodymium, and gadolinium. Such mixed oxides can provide a catalyst composition having particularly stable and excellent OSC properties.

[0051] In some preferred embodiments, M contains only one element. In other words, in such preferred embodiments, only four different cations are present in the solid solution mixed oxide. As described above, having a larger number of different cations contributes to the entropy component of the Gibbs free energy for phase separation and can make phase separation less favorable, but a stable solid solution mixed oxide having excellent OSC properties can still be provided with only four different cations, for example, having the balance of cations described elsewhere in this specification. Therefore, such mixed oxides may also be preferred in some cases.

[0052] Preferably, the platinum group metal contains one or more of platinum, palladium, and rhodium, and preferably, the platinum group metal contains platinum. Such PGM can result in a catalyst composition having particularly desirable catalyst properties for TWC applications and the like.

[0053] In a further aspect, the present invention provides a catalyst article comprising a substrate and the catalyst composition according to any of the preceding claims, wherein the catalyst composition is disposed on the substrate.

[0054] As used herein, the term "catalyst article" can encompass an article on or in which a catalyst is supported. The article can take the form of, for example, a honeycomb monolith or a filter, such as a wall flow filter or a flow through filter.

[0055] As used herein, the term "substrate" can include, for example, a ceramic honeycomb or a metal honeycomb, or a filter block, such as a wall flow filter or a flow through filter. The substrate can include a ceramic monolith substrate. The substrates can differ in terms of their material composition, size and configuration, cell shape and density, and wall thickness. Suitable substrates (such as cordierite) are known in the art.

[0056] The term "disposed on" in the context of this aspect can include both having a catalyst composition disposed directly on the substrate, i.e., without an intervening material, and / or having a catalyst composition disposed indirectly on the substrate, i.e., with an intervening material. When the substrate is porous, the term "disposed on" can also include having a catalyst composition disposed therein, e.g., within the pores of the substrate, i.e., the catalyst composition is disposed on and / or within. The catalyst composition is typically disposed on the substrate in the form of a washcoat. As used herein, the term "washcoat" is well known in the art and generally refers to an adhesive coating applied to the substrate during the production of the catalyst.

[0057] The preferred features of the first aspect are equally applicable to this aspect. The advantages described above with reference to the first aspect may equally be applicable to the resulting catalyst article comprising the catalyst composition.

[0058] Preferably, the catalyst article is a three-way catalyst.

[0059] The catalyst article preferably has a washcoat loading of 1 g / in 3 ~3 g / in 3 .

[0060] Preferably, the substrate includes a wall flow filter substrate. In an alternative preferred embodiment, the substrate includes a flow through substrate.

[0061] The catalyst article preferably includes two or more catalyst regions disposed on a substrate, and the catalyst composition is present in one or more of the catalyst regions.

[0062] As used herein, the term "catalyst region" can typically encompass an area on a substrate obtained by drying and / or calcining a washcoat. The "region" can be disposed or supported on the substrate, for example, as a "layer" or a "zone". The area or arrangement on the substrate is generally controlled during the process of applying the washcoat to the substrate. The "region" typically has a distinct boundary or edge (i.e., it is possible to distinguish one region from another using conventional analytical techniques).

[0063] The "catalyst region" preferably has a substantially uniform composition (i.e., when comparing one part of the region with another part of the region, on average, there is no substantial difference in the composition of the washcoat). A substantially uniform composition in this context refers to a material (e.g., a region) where, when comparing one part of the region with another part of the region, the difference in composition is 5% or less, usually 2.5% or less, and most commonly 1% or less.

[0064] The term "disposed on" in the context of this embodiment can include having a catalyst region disposed directly on the substrate, i.e., without an intervening material, and / or having a catalyst region disposed indirectly on the substrate, i.e., with an intervening material. If the substrate is porous, the term "disposed on" can also include having a catalyst region disposed therein, e.g., within the pores of the substrate, i.e., the catalyst region is disposed on and / or within it. Preferably, the catalyst region is a washcoat layer.

[0065] Other carrier materials and catalysts other than those of the present invention may also be present on and / or in the catalyst article of this aspect.

[0066] When present, the catalyst article preferably has a loading of 2 g / ft 3 ~15 g / ft3 of rhodium, more preferably 3 g / ft 3 ~10 g / ft 3 of rhodium. When present, the catalyst article preferably has 20 g / ft 3 ~200 g / ft 3 of palladium, more preferably 30 g / ft 3 ~150 g / ft 3 of palladium. When present, the catalyst article preferably has 2 g / ft 3 ~200 g / ft 3 of platinum, preferably 10 g / ft 3 ~100 g / ft 3 of platinum.

[0067] In a further aspect, the present invention provides an exhaust treatment system comprising the catalyst article described herein. Preferably, the exhaust treatment system is for a gasoline engine. Preferably, the gasoline engine operates under stoichiometric conditions.

[0068] In a further aspect, the present invention provides a vehicle comprising the exhaust treatment system described herein.

[0069] In a further aspect, the present invention provides a method of treating exhaust gas, the method comprising providing the catalyst article described herein and contacting the catalyst article with the exhaust gas. Preferably, the exhaust gas is from a gasoline engine. Preferably, the gasoline engine operates under stoichiometric conditions.

[0070] In a further aspect, the present invention provides a solid solution mixed oxide having the formula Ce w Zr x Sn y M z O a wherein, 0.05 ≦ w ≦ 0.90, 0.05 ≦ x ≦ 0.90, 0.001 ≦ y ≦ 0.25, 0.001 ≦ z ≦ 0.60, w + x + y + z = 1.00, and 1.0 ≤ a ≤ 2.0, and M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium and ytterbium.

[0071] The preferred features and advantages discussed herein with reference to the first aspect are equally applicable to this aspect. Such solid solution mixed oxides can also be advantageously used in other applications that may require stable mixed oxides with excellent OSC properties.

[0072] In a further aspect, the present invention provides a method for producing a solid solution mixed oxide as described herein, the method comprising providing a solution containing the respective cations of Ce, Zr, Sn and M, contacting the solution with a base to provide a slurry, heating the slurry at a temperature of 20 to 200 °C to provide a mixed oxide precursor, and heating the mixed oxide precursor at a temperature above 450 °C to provide a solid solution mixed oxide.

[0073] Providing a solution containing the respective cations of Ce, Zr, Sn, and M typically involves dissolving the respective soluble salts of Ce, Zr, Sn, and M in water. In other words, the solution is preferably an aqueous solution, i.e., an aqueous solution containing metal cations and their respective counterions. In the method of providing the solution, the order of addition of each cation salt is not particularly limited. Suitable salts can be in somewhat water-soluble form and include nitrates, chlorides, ammonium nitrates, and oxy nitrates, sulfates, carbonates, and any number of organic ligands such as acetates or citrates, but are not limited thereto.

[0074] Contacting the solution with a base may include, for example, adding a base in powder form to the solution and / or contacting the solution containing cations with a basic solution. Contacting the solution containing cations with a basic solution typically involves adding the solution to the basic solution, and vice versa. Preferably, contacting the solution with a base includes raising the pH of the solution to a pH of preferably about 7 to about 9. Contacting the solution with a base typically causes precipitation of the hydrous oxides of the metal cations in the solution. In other words, the slurry can contain the hydrous oxides of Ce, Zr, Sn, and M. Suitable basic solutions can contain a weak base, such as NH3, urea, or a quaternary ammonium hydroxide (e.g., tetraethylammonium hydroxide), or any strong base solution such as NaOH, KOH, Ba(OH)2, Sr(OH)2, etc. Suitable basic solutions can include, for example, a buffer containing ammonium nitrate, ammonia, and water.

[0075] Heating the slurry at a temperature of 20 to 200 °C typically results in, for example, drying of the slurry. In other words, heating the slurry preferably includes at least partially drying the slurry. Thus, the mixed oxide precursor may contain the hydrous oxide powders of Ce, Zr, Sn, and M. The slurry is typically heated at a temperature of 20 to 200 °C for 1 hour to 24 hours. The slurry may be heated in a multi-step heating process.

[0076] Heating the mixed oxide precursor at a temperature above 450 °C typically involves calcining a mixed oxide precursor / hydroxide powder of Ce, Zr, Sn and M. The mixed oxide precursor is typically heated in air for 30 minutes or more. This heating step typically causes the formation of a crystalline mixed oxide.

[0077] Advantageously, such a method is a simple one-pot synthesis. The method may also be easily scalable to larger scale production. The cations of the resulting mixed oxide are typically substantially uniformly dispersed within the solid solution mixed oxide. This cannot be achieved, for example, by production methods that include an initial infiltration impregnation of tin into CZO.

[0078] In a further aspect, the present invention provides a method for manufacturing a catalyst composition as described herein, the method comprising providing a solid solution mixed oxide as described herein, or manufacturing a solid solution mixed oxide according to the method described herein, and disposing a platinum group metal on the solid solution mixed oxide.

[0079] Disposing a platinum group metal on the solid solution mixed oxide typically involves contacting a PGM salt, such as a PGM precursor such as a nitrate, acetate or chloride salt, with the solid solution mixed oxide and depositing the PGM on the solid solution mixed oxide by incipient wetness impregnation or wet impregnation. An alternative method involves the use of a PGM complex such as a PGM-polymer complex. Suitable methods are known to those skilled in the art.

[0080] Preferably, after the step of contacting the solution with the base and before the step of heating the slurry, the method comprises (i) washing and / or filtering the slurry and contacting the resulting product with a further base to form a further slurry, and / or (ii) further comprising modifying the pH of the slurry or further slurry using a base.

[0081] Washing the slurry preferably includes washing the slurry with deionized (DI) water. Washing and / or filtering the slurry can advantageously remove any excess starting materials that did not form the hydrous oxide, for example. Thus, the resulting mixed oxide can have fewer impurities. The preferred embodiments regarding contacting the solution with a base as described above are equally applicable to these further embodiments.

[0082] Modifying the pH of the slurry or a further slurry using a base typically involves contacting the slurry or further slurry with a basic solution. Modifying the pH of the slurry preferably includes increasing the pH of the slurry to a pH of preferably from about 7 to about 9. Such modification can promote the formation of a porous network of particles that imparts thermal stability to high-temperature aging.

[0083] The method preferably includes washing and / or filtering the mixed oxide precursor before heating the mixed oxide precursor. This step can also advantageously remove any excess starting materials that did not form the hydrous oxide, for example. Thus, the resulting mixed oxide can have fewer impurities.

[0084] In a further aspect, the invention provides for the use of the catalyst composition described herein in an emissions treatment system, or the use of the catalyst article described herein. Such use can have the advantages described herein with reference to other aspects of the invention.

[0085] The invention will now be described in connection with the following non-limiting examples.

[0086] Example 1: General Preparation of a Mixed Oxide Having Four Components A solution of metal ions was prepared by dissolving the appropriate metal salts (ammonium cerium nitrate, zirconium oxynitrate, tin(IV) chloride, lanthanum nitrate, neodymium nitrate, gadolinium nitrate, yttrium nitrate, barium nitrate, strontium nitrate, calcium chloride) in DI water as described in Table 1. A buffer solution was prepared by combining ammonium nitrate, ammonia, and water in a molar ratio of 1:10:89. The metal salt solution was then added to a mechanically stirred container containing the buffer solution. A precipitate formed upon mixing the two solutions. The mixture was stirred for an additional 15 minutes. The hydrous oxide precipitate was then filtered through a filter press and washed with DI water.

[0087]

Table 1

[0088] A slurry was prepared by combining hydrous oxide (on a metal basis), ammonium nitrate, ammonia, and water in a molar ratio of 1:1:10:89 and mechanically stirred for 5 minutes. The slurry was then transferred to a Teflon sleeve and sealed in a Parr stainless steel acid digestion vessel. The slurry was then heated to 150 °C and mixed for 2 hours. After cooling to below 60 °C, the hydrous oxide was filtered and washed with DI water until the resulting filtrate reached a pH of less than 7. The hydrous oxide was then dried at 90 °C for 16 hours, pulverized into a powder, and further dried at 120 °C for 2 hours. After drying, the hydrous oxide was calcined in air at 500 °C to form a crystalline solid oxide. The resulting solid metal oxide compositions are summarized in Table 2.

[0089]

Table 2

[0090] The XRD results of the calcined solid oxide powder are shown in Figure 1. After calcination, all samples show diffraction peaks indicating the cubic fluorite phase of CeO2. The peak positions are shifted to higher or lower angles compared to pure CeO2 depending on the composition, indicating the formation of a solid solution where some lattice Ce atom positions are occupied by dopant atoms. Furthermore, no additional peaks were detected, indicating that the samples contained no impurity phase dopant oxides at all. These results demonstrate that the materials of the present invention can be synthesized with single-phase purity.

[0091] Example 2: Accelerated Aging The powdered solid oxide prepared in Example 1 was subjected to high-temperature redox conditions to simulate long-term operation in a vehicle. The powder was placed in a tubular furnace and heated at a rate of 10 °C / min to 1050 °C under a stoichiometric gas mixture consisting of 1.2% CO, 0.4% H2, 0.8% O2, 10% H2O, 10% CO2, and the balance N2 flowing at 5 L / min. The temperature was then held at 1050 °C for 40 hours, during which the flowing gas mixture was changed every 5 minutes in the order listed below. 1. Stoichiometric: 1.2% CO, 0.4% H2, 0.8% O2, 10% H2O, 10% CO2, balance N2 2. Lean: 1.2% CO, 0.4% H2, 1.6% O2, 10% H2O, 10% CO2, balance N2 3. Stoichiometric: 1.2% CO, 0.4% H2, 0.8% O2, 10% H2O, 10% CO2, balance N2 4. Rich: 2.4% CO, 0.8% H2, 0.8% O2, 10% H2O, 10% CO2, balance N2 After 40 hours, the coated core was cooled from 1050 °C to below 400 °C under a rich gas mixture and then from 400 °C to room temperature under N2 only.

[0092] The XRD results of the solid oxide powder after accelerated aging are shown in Figure 2. As a result of subjecting the powder sample to accelerated aging, the diffraction peaks became sharper, suggesting crystal growth due to sintering. However, no further peaks were formed. These results demonstrate that the materials of the present invention are phase-stable against the severe redox conditions at high temperatures typical of automotive exhaust systems.

[0093] Example 3: Oxygen Storage Capacity (OSC) Test After subjecting to the aging conditions described in Example 2, the powdered solid oxide of Example 1 was characterized by an OSC test. In this test, the sample was first heated to 600 °C and pretreated by holding in a 5% O2 (balance N2) atmosphere for 15 minutes. While still maintaining at 600 °C, the gas atmosphere was switched to pure N2 for an additional 5 minutes. Then, the test was started while measuring the amount of CO2 generated in 30 seconds when a stream of 5000 ppm CO (balance N2) was passed through the powdered solid oxide. The OSC of the solid oxide was calculated using the following formula.

[0094]

Equation

[0095] The results of the OSC test are shown in Table 3. The samples of all examples of the present invention showed higher OSC than Comparative Sample 1 containing only Ce and Zr. These results demonstrate that the materials of the present invention exhibit the beneficial oxygen storage characteristics required for use as catalysts in automotive exhaust systems.

[0096] Example 4: Addition of Platinum Group Metal (PGM) Components to Solid Oxides to Form Catalysts To demonstrate the application in reducing automotive emissions, catalysts were prepared by adding PGM to Comparative Example 1 and JM-MO-2 to produce Comparative Catalyst 1 and JM-MO-2 catalyst, respectively. 10 g of calcined solid oxide (dry basis) was dispersed in 23 g of DI water while mechanically mixing to form a slurry. Then, 0.04 g of Rh was added to the slurry in the form of rhodium(III) nitrate solution. A solution of ammonium hydroxide was added to the slurry to readjust the pH to about 7 - 8. The slurry was mixed for 2 hours and then transferred to an open crucible and dried overnight at 80 °C. The resulting catalyst powder containing solid oxide and Rh was calcined in air at 500 °C for 4 hours.

[0097] Example 5: Three-way Catalysis (TWC) Light-off Test Comparative Catalyst 1 and JM-MO-2 catalyst were subjected to the TWC light-off test. In this test, 0.05 g of powdered catalyst mixed with 0.25 g of crushed cordierite was supported on a reactor apparatus capable of heating and flowing a gas mixture designed to simulate gasoline exhaust conditions. Under a gas mixture flowing at 500 cm 3 / min, the temperature was raised from 150 to 600 °C at a rate of 5 °C / min. The volume composition of the gas was 1% CO, 1500 ppm propene (C3H6), 400 ppm NO, 0.65% O2, 6% H2O, and the balance N2. The conversion rates of NO, CO, and total hydrocarbons (THC, composed of C3H6) as a function of temperature are reported in Figures 4, 5, and 6, respectively.

[0098] A useful measure for quantifying the performance of the catalyst is the T 50 value, which is defined herein as the minimum temperature at which 50% conversion is achieved. A lower T 50 temperature indicates a catalyst demonstrating improved catalytic activity. In each case, the catalytic activity was greater for the JM-MO-2 catalyst than for Comparative Catalyst 1, as indicated by the T 50 values. The JM-MO-2 catalyst had T 50 values 40 °C, 35 °C, and 20 °C lower than those of Comparative Catalyst 1 for the NO, CO, and THC conversions, respectively.50 The value was achieved. These results demonstrate that the materials of the present invention exhibit the catalytic activity required for use as a catalyst in automotive emission systems.

[0099] Example 6: General Preparation of Mixed Oxides with Five or More Components A solution of metal ions was prepared by dissolving the appropriate metal salts (ammonium cerium nitrate, zirconium oxynitrate, tin(IV) chloride, lanthanum nitrate, neodymium nitrate, yttrium nitrate, praseodymium nitrate, barium nitrate, strontium nitrate) in DI water as described in Table 3. A buffer solution was prepared by combining ammonium nitrate, ammonia, and water in a molar ratio of 1:10:89. The metal salt solution was then added to a mechanically stirred container containing the buffer solution. A precipitate formed upon mixing the two solutions. The mixture was stirred for an additional 15 minutes. The hydrous oxide precipitate was then filtered through a filter press and washed with DI water.

[0100] [Table 3]

[0101] A slurry was prepared by combining the hydrous oxide (on a metal basis), ammonium nitrate, ammonia, and water in a molar ratio of 1:1:10:89 and mechanically stirred for 5 minutes. The slurry was then transferred to a Teflon sleeve and sealed in a Parr stainless steel acid digestion container. The slurry was then heated to 150 °C and mixed by tumbling in an oven for 2 hours. After cooling to below 60 °C, the hydrous oxide was filtered and washed with DI water until the resulting filtrate reached a pH of less than 7. The hydrous oxide was then dried at 90 °C for 16 hours, pulverized into a powder, and further dried at 120 °C for 2 hours. After drying, the hydrous oxide was calcined in air at 500 °C to form a crystalline solid oxide.

[0102] The obtained solid metal oxide compositions and their average cation radii are summarized in Table 4. A commercially available mixed oxide containing the same Ce content as the samples of this example and a total of five components without Sn was purchased from a supplier and used as Comparative Sample 2. The average cation radius (r avg ) is a useful measure for predicting the stability of doped ceria with a widely varying composition. The average cation radius of each doped ceria was calculated using the following equation.

[0103]

Equation

[0104] where n i is the mole fraction of each individual cation component (excluding the molar contribution of O), and r i is the radius of each individual cation. The method of ion radius determination used in this study is the 8-coordinate effective ion radius (defined in R.D. Shannon, Acta Cryst., 1976, A32, 751). Cerium and tin are assumed to be in the 4+ oxidation state. Lanthanum, neodymium, praseodymium, and yttrium are assumed to be in the 3+ oxidation state. Strontium and barium are assumed to be in the 2+ oxidation state.

[0105]

Table 4

[0106] The XRD results of the powders of the calcined solid oxides are shown in Figure 7. After calcination, all samples show diffraction peaks indicating the cubic fluorite phase of CeO2. The peak positions are shifted to higher or lower angles compared to pure CeO2 depending on the composition, indicating the formation of a solid solution in which some lattice Ce atom positions are occupied by dopant atoms. Furthermore, no additional peaks were detected, indicating that the samples contained no impurity phase dopant oxides at all. These results demonstrate that the materials of the present invention can be synthesized with single-phase purity.

[0107] Example 7: Perturbed Three-Way Catalysis (TWC) Light-Off Test To demonstrate the application in automotive emissions reduction, catalysts were prepared by adding PGM to Comparative Example 2 and JM-MO-2, and Comparative Catalyst 2 and JM-MO-10 catalysts were fabricated, respectively. 10 g of calcined solid oxide (dry basis) was dispersed in 23 g of DI water while mechanically mixing to form a slurry. Then, 0.3 g of Pt was added to the slurry in the form of a platinum(II) nitrate solution. A solution of ammonium hydroxide was added to the slurry to readjust the pH to about 7 - 8. The slurry was mixed for 2 hours and then transferred to an open crucible and dried overnight at 80°C. The resulting catalyst powder containing solid oxide and Pt was calcined in air at 500°C for 4 hours. Then, the powder catalyst was subjected to high-temperature redox conditions to simulate long-term operation in a vehicle as described in Example 2.

[0108] Next, these catalysts were subjected to a perturbed TWC light-off test. In this test, 0.3 g of the powder catalyst was loaded into a reactor apparatus capable of heating and flowing a gas mixture designed to simulate gasoline exhaust conditions. Under a gas mixture flowing at 3000 cm 3 / min, the temperature was raised from 150 to 600°C at a rate of 15°C / min. The flowing gas was perturbed between rich and lean conditions at a frequency of 1 Hz. The volume composition of the gas was as follows. Rich = 6% H2O, 14% CO2, 2000 ppm NO, 0.58% O2, 200 ppm propene (C3H6), 200 propane (C3H8), 2.5% CO, and 0.5% H2 (balance N2), and Lean = 6% H2O, 14% CO2, 2000 ppm NO, 1.93% O2, 200 ppm propene (C3H6), 200 propane (C3H8), 0.5% CO, and 0.5% H2 (balance N2). The temperature (T 20 ) at which a 20% conversion rate of NO, CO, and total hydrocarbons (composed of THC, C3H6, and C3H8) was reached is reported in Figure 8.

[0109] A useful measure for quantifying the performance of the catalyst is T 20value, which is defined herein as the minimum temperature at which a 20% conversion rate is achieved. Lower T 20 temperatures indicate a catalyst demonstrating improved catalytic activity. In each case, the catalytic activity is the T 20 value achieved by each catalyst. As is evident from the T 20 values, the catalysts of the present invention were greater than Comparative Catalyst 2. The JM-MO-10 catalyst had T 20 values that were 14 °C, 48 °C, and 28 °C lower, respectively, than the T

[0110] The foregoing detailed description is provided for purposes of explanation and illustration and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments shown herein will be apparent to those skilled in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. A catalyst composition comprising a mixed oxide support material and a platinum group metal supported on the mixed oxide support material, wherein the mixed oxide support material has the formula Ce ｗ Zr ｘ Sn ｙ M ｚ O ａ and contains a solid solution mixed oxide having the formula, wherein 0.05 ≤ w ≤ 0.90, 0.05 ≤ x ≤ 0.90, 0.001 ≤ y ≤ 0.25, 0.001 ≤ z ≤ 0.60, w + x + y + z = 1.00, 1.0 ≤ a ≤ 2.0, M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium and ytterbium, a catalyst composition.

2. The catalyst composition according to claim 1, which is for three-way catalysis.

3. The catalyst composition according to claim 1 or claim 2, wherein the solid solution mixed oxide is at least 95% phase pure.

4. The catalyst composition according to any one of claims 1 to 3, wherein y + z is less than 0.15, preferably 0.10 or less.

5. The catalyst composition according to any one of claims 1 to 3, wherein 0.05 ≤ y ≤ 0.

15.

6. The catalyst composition according to any one of claims 1 to 5, wherein w + x is 0.80 or more, preferably 0.85 or more, more preferably 0.90 or more.

7. The catalyst composition according to any one of claims 1 to 6, wherein w + y is more than 0.5, preferably 0.55 or more.

8. The catalyst composition according to any one of claims 1 to 7, wherein 0.07 ≤ y ≤ 0.

11.

9. The catalyst composition according to any one of claims 1 to 8, wherein 0.20 ≤ w ≤ 0.80, preferably 0.30 ≤ w ≤ 0.

70.

10. The catalyst article according to any one of claims 1 to 9, wherein M contains two or more different elements.

11. The catalyst composition according to any one of claims 1 to 3 or claim 10, wherein 0.15 ≤ w, x ≤ 0.25 and 0.30 ≤ y + z ≤ 0.

70.

12. M ｚ is M' ｚ１ M'' ｚ２ and wherein 0.15 ≤ z1 ≤ 0.25, 0.15 ≤ z2 ≤ 0.25, M' is an element selected from one of calcium, strontium, barium, scandium, yttrium, hafnium, lanthanum, praseodymium, neodymium, samarium, europium, or gadolinium, M'' is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium and ytterbium, The catalyst composition according to claim 11, wherein M' is different from M''.

13. The catalyst composition according to claim 12, wherein M' is yttrium.

14. The catalyst composition according to claim 12 or claim 13, wherein M'' contains only one element.

15. The catalyst composition according to any one of claims 11 to 14, wherein the average cationic radius of Ce, Zr, Sn and M in the solid solution mixed oxide is 90 to 106 pm.

16. The catalyst composition according to any one of claims 1 to 15, wherein M is an element selected from one or more of calcium, strontium, barium, scandium, yttrium, hafnium, lanthanum, praseodymium, neodymium, samarium, europium and gadolinium.

17. The catalyst composition according to claim 16, wherein M is an element selected from one or more of calcium, strontium, barium, yttrium, lanthanum, neodymium and gadolinium.

18. The catalyst article according to any one of claims 1 to 9, 11, 16 or 17, wherein M contains only one element.

19. The catalyst composition according to any one of claims 1 to 18, wherein the platinum group metal contains one or more of platinum, palladium and rhodium, and preferably, the platinum group metal contains platinum.

20. A catalyst article comprising a substrate and the catalyst composition according to any one of claims 1 to 19, wherein the catalyst composition is disposed on the substrate.

21. The catalyst article according to claim 20, wherein the catalyst article is a three-way catalyst.

22. 1 g / in ３ ~3 g / in ３ The catalyst article according to claim 20 or 21, having a washcoat loading of

23. The catalyst article according to any one of claims 20 to 22, wherein the substrate includes a wall flow filter substrate.

24. The catalyst article according to any one of claims 20 to 22, wherein the substrate includes a flow-through substrate.

25. The catalyst article according to any one of claims 20 to 24, comprising two or more catalyst regions disposed on the substrate, wherein the catalyst composition is present in one or more of the catalyst regions.

26. 2 g / ft ３ to 15 g / ft ３ of rhodium, preferably, 3 g / ft ３ to 10 g / ft ３ The catalyst article according to any one of claims 20 to 25, comprising rhodium.

27. 20 g / ft ３ to 200 g / ft ３ of palladium, preferably 30 g / ft ３ to 150 g / ft ３ The catalyst article according to any one of claims 20 to 26, comprising palladium.

28. 2 g / ft ３ to 200 g / ft ３ of platinum, preferably 10 g / ft ３ to 100 g / ft ３ The catalyst article according to any one of claims 20 to 27, comprising platinum.

29. An exhaust gas treatment system comprising the catalyst article according to any one of claims 20 to 28.

30. The exhaust gas treatment system according to claim 29 for a gasoline engine.

31. The exhaust gas treatment system according to claim 30, wherein the gasoline engine operates under stoichiometric conditions.

32. A vehicle comprising the exhaust gas treatment system according to any one of claims 20 to 31.

33. A method for treating exhaust gas, the method comprising: providing the catalyst article according to any one of claims 20 to 28; and contacting the catalyst article with the exhaust gas.

34. The method according to claim 33, wherein the exhaust gas is derived from a gasoline engine.

35. The method according to claim 34, wherein the gasoline engine operates under stoichiometric conditions.

36. Formula Ce ｗ Zr ｘ Sn ｙ M ｚ O ａ is a solid solution mixed oxide having, in the formula, 0.05 ≤ w ≤ 0.90, 0.05 ≤ x ≤ 0.90, 0.001 ≤ y ≤ 0.25, 0.001 ≤ z ≤ 0.60, w + x + y + z = 1.00, 1.0 ≤ a ≤ 2.0, The solid solution mixed oxide, wherein M is an element selected from one or more of sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, aluminum, gallium, thallium, silicon, germanium, lead, bismuth, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, erbium, lutetium, dysprosium, holmium, thulium and ytterbium.

37. A method for producing the solid solution mixed oxide according to claim 36, the method comprising: providing a solution containing respective cations of Ce, Zr, Sn and M; contacting the solution with a base to provide a slurry; heating the slurry at a temperature of 20 to 200 ° C to provide a mixed oxide precursor; heating the mixed oxide precursor at a temperature above 450 ° C to provide the solid solution mixed oxide.

38. A method for producing the catalyst composition according to any one of claims 1 to 19, the method comprising: providing the solid solution mixed oxide according to claim 36, or producing the solid solution mixed oxide according to the method of claim 37; disposing the platinum group metal on the solid solution mixed oxide.

39. After the step of contacting the solution with a base and before the step of heating the slurry, the method further comprises: (i) washing and / or filtering the slurry and contacting the resulting product with a further base to form a further slurry, and / or (ii) modifying the pH of the slurry or the further slurry using a base. The method according to claim 37 or claim 38.

40. The method according to any one of claims 37 to 39, further comprising washing and / or filtering the mixed oxide precursor before heating the mixed oxide precursor.

41. Use of the catalyst composition according to any one of claims 1 to 19 or the catalyst article according to any one of claims 20 to 28 in an exhaust treatment system.

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