Surface modification of mixed oxides for high PGM dispersion

Abstract

Disclosed herein are compositions having a mixed oxide core comprising ceria and zirconia, which is free of alumina. The mixed oxide core contains about 15 wt% to about 60 wt% cerium oxide and about 40 wt% to about 85 wt% zirconium oxide, based on the total weight of the mixed oxide core. The mixed oxide core has a rare earth oxide coating selected from the group consisting of cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. Further, a noble metal including palladium or rhodium is dispersed on the surface of these compositions, and the composition has a higher rhodium or palladium dispersion relative to a composition comprising a mixed oxide core without the presence of a rare earth oxide coating. Methods of producing these compositions are also disclosed. The composition may be used as part of a catalyst system.

Description

[0001] Cross-reference to related applications

[0002] This application was filed as a PCT international application on April 8, 2024 (Sunday, April 7, 2024), and claims priority and benefit to U.S. Provisional Patent Application No. 63 / 494,907, filed April 7, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This application relates to compositions comprising a mixed oxide core containing cerium oxide and zirconium oxide, and optionally additional rare earth oxides. The mixed oxide core has a rare earth oxide coating on its surface, the rare earth oxide being selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. The composition also has rhodium or palladium on its surface, wherein the composition has a higher rhodium or palladium dispersion compared to a composition without a rare earth oxide coating on the mixed oxide core.

[0004] introduce

[0005] Various conventional catalysts have been used to purify exhaust gases from internal combustion engines and other sources. These conventional catalysts are often identified as three-way catalytic converters (TWC catalysts), and they oxidize exhaust pollutants including both hydrocarbons and carbon monoxide, reducing nitrogen oxides to relatively harmless components such as water, nitrogen, and carbon dioxide. These catalysts operate at high temperatures. For this reason, these catalysts need to have a high level of heat resistance so that they maintain high catalytic activity even after prolonged use at these high temperatures.

[0006] These TWC catalysts typically consist of noble metals (Pd, Pt, or Rh) coated onto a monolithic flow path with alumina and rare earth oxides. However, deactivation of TWC catalysts occurs due to the sintering of noble metal group metal (PGM) particles when subjected to high operating conditions. High PGM dispersion is required after thermal aging, and this indicates that sintering of PGM particles is reduced, as this protects the active sites of the PGMs to provide high catalytic performance.

[0007] To date, efforts to produce catalyst compositions that remain effective for extended periods of use at high temperatures have not been entirely successful. Thus, there remains a need to develop mixed oxides that exhibit high PGM dispersion even after thermal aging and can be used as catalysts. Summary of the Invention

[0008] This document discloses mixed oxide compositions comprising cerium oxide and zirconium oxide with rare earth oxide coatings. The mixed oxide core with rare earth oxide coatings is also described herein as a mixed oxide having a surface modified with rare earth oxides. These compositions have noble metal group metals on the surface and are free of alumina. The compositions disclosed herein are typically mixed oxide compositions. These compositions exhibit high noble metal dispersion. The compositions are suitable for use in catalysts as part of catalyst systems for use in gas emission purification.

[0009] This document discloses compositions comprising a mixed oxide core comprising about 15 wt% to about 60 wt% cerium oxide and about 40 wt% to about 85 wt% zirconium oxide, based on the total weight of the mixed oxide core, and wherein the mixed oxide core and the overall composition are free of alumina. The mixed oxide core has a rare earth oxide coating on its surface, the rare earth oxide being selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. The composition of the mixed oxide core and the rare earth oxide coating has rhodium or palladium on its surface. The compositions disclosed herein exhibit higher rhodium or palladium dispersion relative to compositions with a mixed oxide core but without or without a rare earth oxide coating.

[0010] In some embodiments, for high palladium dispersion, the overall composition should contain at least about 40% by weight of cerium. In other embodiments, for high rhodium dispersion, the overall composition should contain at most about 25% by weight of cerium.

[0011] In some embodiments, the composition has rhodium dispersed on the surface, wherein the rhodium dispersion is about 18.5% to about 28.6% after calcination (i.e. aging) in air at 800°C for 2 hours, or about 14.3% to about 21.9% after further calcination (i.e. aging) in air at 1000°C for 10 hours, or about 10.3% to about 16.5% after further calcination (i.e. aging) in air at 1100°C for 10 hours.

[0012] In other embodiments, the composition has palladium dispersed on the surface, wherein the palladium dispersion is about 35.0% to about 46.1% after calcination (i.e., aging) in air at 800°C for 2 hours, or about 8.5% to about 13.0% after calcination (i.e., aging) in air at 1000°C for 10 hours, or about 3.9% to about 6.0% after calcination (i.e., aging) in air at 1100°C for 10 hours.

[0013] In some embodiments, the composition comprises a mixed oxide core consisting essentially of cerium oxide, zirconium oxide, and additional rare earth oxides selected from lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide, and mixtures thereof. The rare earth oxide coating is one or two of cerium oxide, neodymium oxide, and praseodymium oxide. The composition has rhodium or palladium on its surface. When palladium is present, the palladium content is about 35.0% to about 46.1% after calcination in air at 800°C for 2 hours, or about 8.5% to about 13% after calcination in air at 1000°C for 10 hours, or about 3.9% to about 6.0% after calcination in air at 1100°C for 10 hours. Or, when rhodium is present, the rhodium content is about 18.5% to about 28.6% after being calcined in air at 800°C for 2 hours, or about 14.3% to about 21.9% after being calcined in air at 1000°C for 10 hours, or about 10.3% to about 16.5% after being calcined in air at 1100°C for 10 hours.

[0014] This document also discloses a method for producing a composition comprising a mixed oxide core and a rare earth oxide coating on a surface, wherein the composition has rhodium or palladium on the surface. The method includes the following steps: (a) providing a mixed oxide powder of cerium oxide, zirconium oxide, and optionally one or more rare earth oxides selected from neodymium, lanthanum, praseodymium, and yttrium; (b) dissolving a rare earth salt in water, wherein the rare earth element of the salt is selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof to provide a rare earth solution; (c) combining and mixing the rare earth solution with the mixed oxide powder to provide a homogeneous powder mixture; and (d) calcining the homogeneous powder mixture at about 400-600°C, and preferably 500°C, for about 2-5 hours, and preferably 3 hours, to provide a rare earth oxide coating on the surface. (e) A mixed oxide core with a rare earth oxide coating, wherein the rare earth element in the coating is selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof; and (f) adding a rhodium or palladium salt solution to the mixed oxide core having a rare earth oxide coating; and (f) calcining at about 500°C to about 650°C and preferably 550°C for about 2 hours to about 5 hours and preferably 2 hours to provide an oxide composition comprising a mixed oxide core having a rare earth oxide coating on its surface and having a higher rhodium or palladium dispersion relative to a composition having a mixed oxide core but without or without a rare earth oxide coating.

[0015] In one embodiment, the calcination in step (d), the "first calcination," is carried out at a temperature of about 500°C for about 3 hours. In one embodiment, the calcination in step (f), the "second calcination," is carried out at a temperature of about 550°C for about 2 hours. Brief description of the attached diagram

[0016] Figure 1 A flowchart illustrating an embodiment of the method for preparing the composition as disclosed herein.

[0017] Detailed description

[0018] This disclosure generally relates to compositions comprising a mixed oxide core containing cerium oxide, zirconium oxide, and optionally additional rare earth oxides. The mixed oxide core and the overall composition are free of alumina. The mixed oxide core has a rare earth oxide coating on its surface, the rare earth oxides being selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. These compositions are typically mixed oxide compositions and have high noble metal dispersion, and particularly high rhodium or palladium dispersion. The mixed oxide core having a rare earth oxide coating is also described herein as a mixed oxide with a surface modification, which is an additional rare earth oxide coating.

[0019] Compositions with a mixed oxide core having a rare earth oxide coating have a noble metal group metal on the surface, and in some embodiments, this noble metal group metal is rhodium or palladium. The compositions disclosed herein exhibit higher noble metal group metal dispersion compared to compositions having a mixed oxide core without or without a rare earth oxide coating. In some embodiments, the compositions disclosed herein exhibit higher rhodium or palladium dispersion compared to compositions having a mixed oxide core without or without a rare earth oxide coating. For this comparison, the mixed oxide core is compositionally identical except for the rare earth oxide coating.

[0020] Before disclosing and describing compositions comprising zirconium oxide and cerium oxide and free of alumina, and methods for their preparation, it should be understood that this disclosure is not limited to the specific structures, method steps, or materials disclosed herein, but extends to their equivalents, as would be recognized by one of ordinary skill in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be restrictive. It must be noted that, as used in this specification, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” include the plural referents. Thus, for example, reference to “step” may include multiple steps, references to “preparation” or “product” of a reaction or treatment should not be considered as all products of the reaction / treatment, and references to “treatment” may include references to one or more such treatment steps. Thus, a treatment step may include multiple or repeated treatments of similar materials / flows to prepare the identified treated product.

[0021] Numerical values ​​using "about" or "approximately" include typical experimental variance, and these terms "about" and "approximately" are used interchangeably. As used herein, the term "about" or "approximately" means within the statistically significant range of values, such as particle size, concentration range, time range, molecular weight, temperature, or pH. Such ranges may be within the order of magnitude of the indicated value or range, typically within 10%, and more typically within 5%. Sometimes, such ranges may be within the typical experimental error of standard methods used to measure and / or determine a given value or range. The permissible variation covered by the term "about" will depend on the specific system being studied and will be readily understood by those skilled in the art. Whenever a range is described in this application, each integer within that range is also considered an embodiment of the invention.

[0022] The terms "based on total weight of composition" and "based on overall composition" are interchangeable, and are the opposite of "based on total weight of mixed oxide core." Surface modification using rare earth oxides is also used interchangeably with rare earth oxide coatings herein.

[0023] This application relates to oxide compositions. These compositions have a mixed oxide core, wherein the mixed oxide core has a rare earth coating on its surface. The mixed oxide core contains about 15% to about 60% cerium oxide and about 40% to about 85% zirconium oxide based on the total weight of the mixed oxide core, and is free of aluminum oxide. In fact, the compositions disclosed herein are aluminum oxide-free overall.

[0024] Alumina-free means that the composition contains less than about 0.1% by weight to about zero% by weight of alumina. In some embodiments, alumina-free means that there is no detectable amount of alumina or about zero% by weight of alumina. In all embodiments of the compositions disclosed herein, as defined above, the mixed oxide core and the overall composition are alumina-free.

[0025] In addition to zirconium oxide and cerium oxide, the mixed oxide core may optionally contain one or more rare earth oxides other than cerium. These additional and optional rare earth oxides include oxides of any rare earth element other than cerium. In a particular embodiment, the additional one or more rare earth oxides of the mixed oxide core are lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide. Thus, the mixed oxide core may optionally contain one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide. Therefore, the compositions disclosed herein comprise a mixed oxide core containing zirconium oxide and cerium oxide, and optionally additional rare earth oxides selected from yttrium oxide, lanthanum oxide, neodymium oxide, praseodymium oxide, and mixtures thereof.

[0026] In some embodiments, the mixed oxide core contains two of these additional oxides. In other embodiments, the mixed oxide core contains three of these additional oxides. In some embodiments, the composition comprises a mixed oxide core consisting essentially of cerium oxide, zirconium oxide, and additional rare earth oxides selected from lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide, and mixtures thereof.

[0027] As described, the hybrid oxide core has a rare earth oxide coating on its surface. It is also described as a hybrid oxide having its surface modified with rare earth oxides. The rare earth elements in the rare earth oxide coating are selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. In some embodiments, the rare earth oxide coating on the surface is one or two of cerium oxide, neodymium oxide, and praseodymium oxide. The rare earth oxide coating may be in an amount from about 1% to about 10% by weight based on the total weight of the composition. In some embodiments, the rare earth oxide coating may be in an amount from about 1% to about 8% by weight based on the total weight of the composition. In embodiments described herein, the rare earth oxide coating may be in an amount from about 1% to about 6% by weight based on the total weight of the composition.

[0028] The mixed oxide core contains about 15% to about 60% cerium oxide and about 40% to about 85% zirconia based on the total weight of the mixed oxide core, and is free of alumina. The composition as a whole contains about 15% to about 60% cerium oxide and about 40% to about 85% zirconia based on the total weight of the composition, and is free of alumina.

[0029] In embodiments where the mixed oxide core contains additional rare earth oxides, one or more additional rare earth oxides may be present in an amount of about 2% to about 15% by weight based on the total weight of the composition. In some embodiments, one or more additional rare earth oxides may be present in an amount of about 5% to about 12% by weight based on the total weight of the composition. In a particular embodiment, one or more additional rare earth oxides may be present in an amount of about 7% to about 10% by weight based on the total weight of the composition.

[0030] In some embodiments, the composition comprises La2O3, Y2O3, Nd2O3 and Pr6O 11 One or more of the following, and a mixed oxide core of CeO2 and ZrO2, wherein the mixed oxide core has a rare earth oxide coating on its surface, and the rare earths in the rare earth oxide coating are CeO2, Nd2O3 and Pr6O. 11 One or two of these compositions. In some of these compositions, the composition has rhodium on its surface, and in other embodiments, the composition has palladium on its surface.

[0031] In the compositions disclosed herein, the rare earth coating comprises about 1% to about 10% by weight based on the total weight of the composition. In some embodiments, the rare earth oxide coating is a single rare earth oxide, wherein the rare earth element of the single rare earth oxide is selected from cerium, lanthanum, neodymium, and praseodymium, and the rare earth oxide coating comprises about 1% to about 5% by weight based on the total weight of the composition. In other embodiments, the rare earth oxide coating comprises two rare earth oxides, wherein the two rare earth elements of the rare earth oxide coating are independently selected from cerium, lanthanum, neodymium, and praseodymium, and each rare earth oxide of the coating comprises about 1% to about 5% by weight based on the total weight of the composition (such that the total rare earth oxide coating comprises about 2% to about 10% by weight based on the total weight of the composition).

[0032] The composition also has a noble metal on its surface. These noble metals can be any noble metal group metal, including platinum, palladium, and rhodium. In specific embodiments, the composition has palladium or rhodium dispersed on its surface. As disclosed and described herein, the composition has a higher noble metal group metal dispersion compared to a composition having a mixed oxide core but without (i.e., no) a rare earth oxide coating. In specific embodiments, the composition has a higher rhodium or palladium dispersion compared to a composition having a mixed oxide core but without (i.e., no) a rare earth oxide coating. The combination of the mixed oxide core and the rare earth oxide coating of the present invention provides an improved composition with higher noble metal dispersion and, in some embodiments, higher rhodium or palladium dispersion. Thus, the oxide compositions disclosed herein are better suited for use as catalysts or in catalyst compositions.

[0033] In some embodiments, the precious metal is palladium, and in other embodiments, the precious metal is rhodium. The precious metal may be present on the surface as a metal or as an oxide. In some embodiments, the composition comprises rhodium, and rhodium is present as an oxide, and the overall composition comprises about 0.3 wt% to about 0.8 wt% Rh₂O₃ based on the total weight of the composition, and in a particular embodiment, about 0.5 wt% Rh₂O₃ based on the total weight of the composition. In other embodiments, the composition comprises palladium, and palladium is present as an oxide, and the overall composition comprises 1.0 wt% to 2.0 wt% PdO based on the total weight of the composition, and in a particular embodiment, about 1.6 wt% PdO based on the total weight of the composition.

[0034] For high palladium dispersion, the overall composition should contain at least about 40% by weight of cerium. For high rhodium dispersion, the overall composition should contain at most about 25% by weight of cerium.

[0035] In some embodiments containing palladium, the composition comprises a mixed oxide core comprising about 35% to about 60% cerium oxide, about 40% to about 65% zirconium oxide, and one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide, based on the weight of the mixed oxide core. The mixed oxide core has a rare earth oxide coating, wherein the rare earth element in the coating is selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. In some of these embodiments, the mixed oxide core additionally contains lanthanum oxide, neodymium oxide, and praseodymium oxide. In other of these embodiments, the mixed oxide core additionally contains lanthanum oxide, neodymium oxide, and yttrium oxide. In some of these embodiments, the rare earth oxide coating is neodymium oxide, cerium oxide, praseodymium oxide, or mixtures thereof. This composition exhibits higher palladium dispersion relative to compositions having a mixed oxide core without or without a rare earth oxide coating. For this comparison, the mixed oxide core is compositionally identical except for the rare earth oxide coating.

[0036] In other embodiments containing palladium, the composition comprises a mixed oxide core comprising about 35% to about 60% cerium oxide based on the total weight of the mixed oxide core; about 40% to about 65% zirconium oxide based on the total weight of the mixed oxide core; optionally one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide, and is free of aluminum oxide. The mixed oxide core has a rare earth oxide coating, wherein the rare earth element in the coating is selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. The composition has palladium dispersed on a surface, wherein the palladium dispersion is about 35.0% to about 46.1% after calcination in air at 800°C for 2 hours, or about 8.5% to about 13.0% after calcination in air at 1000°C for 10 hours, or about 3.9% to about 6.0% after calcination in air at 1100°C for 10 hours.

[0037] In some embodiments containing rhodium, the composition comprises a mixed oxide core comprising about 15% to about 25% cerium oxide, about 70% to about 85% zirconium oxide, and one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide, based on the weight of the mixed oxide core. The mixed oxide core has a rare earth oxide coating, wherein the rare earth element in the coating is selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. In some of these embodiments, the mixed oxide core additionally contains lanthanum oxide and neodymium oxide. In some of these embodiments, the rare earth oxide coating is neodymium oxide, cerium oxide, or mixtures thereof. This composition exhibits higher rhodium dispersion compared to compositions having a mixed oxide core without or without a rare earth oxide coating. For this comparison, the mixed oxide core is compositionally identical except for the rare earth oxide coating.

[0038] In other embodiments containing rhodium, the composition comprises a mixed oxide core comprising about 15% to about 25% by weight of cerium oxide based on the total weight of the mixed oxide core; about 70% to about 85% by weight of zirconium oxide based on the total weight of the mixed oxide core; optionally one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide; and is free of aluminum oxide. The mixed oxide core has a rare earth oxide coating, wherein the rare earth element in the coating is selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. The composition has rhodium dispersed on the surface, wherein the rhodium dispersion is about 18.5% to about 28.6% after calcination in air at 800°C for 2 hours, or about 14.3% to about 21.9% after calcination in air at 1000°C for 10 hours, or about 10.3% to about 16.5% after calcination in air at 1100°C for 10 hours.

[0039] The compositions disclosed herein may contain trace amounts of impurities. These impurities are typically present in amounts of about 1% by weight or less (to about zero or to undetectable amounts) based on the total weight of the composition. These impurities include residual solvents, salts, other metals, etc. These other metals include those commonly found in water, such as magnesium, iron, calcium, silicon, sodium, etc. The amount of these impurities (from about 1% by weight to about zero or to undetectable amounts) may be present in any of the embodiments of the compositions disclosed herein. When present and detectable, any impurity may be present in amounts of about 100 ppm or less.

[0040] Measurement of rhodium dispersion:

[0041] Rhodium dispersion was determined by CO adsorption measured using a CO pulse chemisorption method. Characterization was performed on aged powder using a Micrometrics Autochem 2920 system. Approximately 0.5 g of rhodium-loaded sample was weighed into a quartz sample tube filled with a quartz wool bed. Each sample was then sieved at 50 cm⁻¹. 3 Reduction at 10% H2 / Ar flow rate to 900℃ for 30 min. Subsequently, He was reduced at 50 cm⁻¹. 3 Flow at 30 min / min for 30 min. Then at 50 cm 3 The sample was cooled to 35°C under a He flow rate of / min. A 10% CO / He pulse was applied to the sample every 2 min until saturation was achieved. A 1:1 stoichiometric ratio of CO to rhodium was assumed. The mass of the sample after analysis was used to quantify the percentage of rhodium dispersion.

[0042] In some embodiments, the composition comprises a mixed oxide core comprising about 15% to about 25% by weight cerium oxide, about 70% to about 85% by weight zirconium oxide, and one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide, and is free of aluminum oxide. The mixed oxide core has a rare earth coating. The rare earth element in the rare earth oxide coating is selected from neodymium, cerium, praseodymium, or mixtures thereof. This composition is free of aluminum oxide. The composition has a higher rhodium dispersion compared to compositions having a mixed oxide core without or without a rare earth oxide coating.

[0043] In a specific embodiment, the composition comprises a mixed oxide core consisting essentially of cerium oxide, zirconium oxide, lanthanum oxide, and neodymium oxide, and the rare earth coating is one or both of cerium oxide and neodymium oxide. This composition is aluminum oxide-free and exhibits higher rhodium dispersion compared to compositions with a mixed oxide core but without or without a rare earth oxide coating.

[0044] In an additional embodiment where the composition has rhodium on its surface, the composition comprises about 20% to about 25% cerium oxide based on the total weight of the composition, and about 1% to about 10% rare earth oxide coating based on the total weight of the composition.

[0045] In a particular embodiment, the composition comprises a mixed oxide core comprising about 15% to about 25% by weight cerium oxide, about 70% to about 85% by weight zirconium oxide, based on the total weight of the mixed oxide core, and optionally one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide, and is free of aluminum oxide. The mixed oxide core has a rare earth oxide coating, wherein the rare earth elements in the coating are selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. The composition also comprises rhodium dispersed on the surface, wherein the rhodium dispersion is about 18.5% to about 28.6% after calcination (aging) in air at 800°C for 2 hours, or about 14.3% to about 21.9% after calcination (aging) in air at 1000°C for 10 hours, or about 10.3% to about 16.5% after calcination (aging) in air at 1100°C for 10 hours. These further calcinations (or agings) are aging treatments performed after the preparation of the composition. These further calcinations (or aging) can be carried out independently.

[0046] In some embodiments, the composition comprises about 20% to about 25% cerium oxide based on the total weight of the composition, and about 1% to about 10% rare earth oxide coating based on the total weight of the composition, and has rhodium dispersed on the surface. In these embodiments, the composition has a higher rhodium dispersion compared to compositions having a mixed oxide core without or without a rare earth oxide coating. The rhodium dispersion may be about 18.5% to about 28.6% after calcination (aging) in air at 800°C for 2 hours, or about 14.3% to about 21.9% after calcination (aging) in air at 1000°C for 10 hours, or about 10.3% to about 16.5% after calcination (aging) in air at 1100°C for 10 hours. These further calcinations (or agings) are aging treatments performed after the preparation of the composition. These further calcinations (or agings) may be performed independently.

[0047] In some embodiments, the rhodium dispersion may be about 21% after calcination (aging) in air at 800°C for 2 hours, about 15% after calcination (aging) in air at 1000°C for 10 hours, or about 10.5% after calcination (aging) in air at 1100°C for 10 hours.

[0048] The % of rhodium dispersion does not refer to the percentage of surface area covered by rhodium. Rather, it refers to the percentage of rhodium atoms present as surface atoms. For example, theoretically, 100% rhodium dispersion means that all rhodium atoms (added to the composition) are present as rhodium surface atoms. Typically, this parameter is used to quantify the degree of sintering of rhodium particles after calcination (aging).

[0049] As described herein, calcination (aging) conditions are not cumulative. Rhodium dispersion values ​​are achieved after the preparation of a calcined (aged) composition comprising a mixed oxide core with a rare earth oxide coating, on which rhodium is deposited. During its preparation, the composition is heat-treated or calcined prior to the addition of rhodium, and subjected to a second calcination or heat treatment after the addition of rhodium. This process provides a “fresh” or “prepared” composition. The heat treatment or calcination during composition preparation after the addition of rhodium is performed at approximately 500°C to approximately 650°C (preferably 550°C) for approximately 2 to 5 hours (preferably approximately 2 hours). Aging calcination is performed under different conditions independent of those specified herein to test the degree of sintering of the rhodium particles. These further calcinations or aging treatments may be performed in air at approximately 800°C for approximately 2 hours, in air at approximately 1000°C for approximately 10 hours, or in air at approximately 1100°C for approximately 10 hours, and are used to test rhodium sintering during simulated use.

[0050] Measurement of palladium dispersion:

[0051] Palladium dispersion was determined by CO adsorption measured using a CO pulsed chemisorption method. Characterization was performed on aged powder using a Micrometrics Autochem 2920 system. Approximately 0.5 g of Pd-loaded sample was weighed into a quartz sample tube filled with a quartz wool bed. Each sample was then sieved at 50 cm⁻¹. 3 Reduction was carried out at 400 °C for 30 min with a 10% H2 / Ar flow rate. Subsequently, He was flowed at 50 cm³ / min for 30 min. Then, at 50 cm³ / min... 3 The sample was cooled to 35°C under a He flow rate of / min. A 10% CO / He pulse was applied to the sample every 2 min until saturation was achieved. A 1:1 stoichiometric ratio of CO to palladium atoms was assumed. The mass of the sample after analysis was used to quantify the percentage of palladium dispersion.

[0052] In some embodiments, the composition comprises a mixed oxide core comprising about 35 wt% to about 60 wt% cerium oxide, about 40 wt% to about 65 wt% zirconium oxide, and one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide, and is free of aluminum oxide. The mixed oxide core has a rare earth coating. The rare earth element in the rare earth oxide coating is selected from neodymium, cerium, praseodymium, or mixtures thereof. The composition exhibits higher palladium dispersion compared to compositions having a mixed oxide core without or without a rare earth oxide coating.

[0053] In a specific embodiment, the composition comprises a mixed oxide core consisting essentially of cerium oxide, zirconium oxide, and two or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide, and the rare earth coating is cerium oxide, neodymium oxide, or praseodymium oxide. This composition is aluminum oxide-free and exhibits higher rhodium dispersion compared to compositions having a mixed oxide core but without or without a rare earth oxide coating.

[0054] In an additional embodiment where palladium is present on the surface of the composition, the composition comprises about 40% to about 60% cerium oxide based on the total weight of the composition, and about 1% to about 10% rare earth oxide coating based on the total weight of the composition.

[0055] In a particular embodiment, the composition comprises a mixed oxide core comprising about 35% to about 60% cerium oxide based on the total weight of the mixed oxide core; about 40% to about 65% zirconium oxide based on the total weight of the mixed oxide core; optionally one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide; and is free of aluminum oxide. The mixed oxide core has a rare earth oxide coating, wherein the rare earth element in the coating is selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. The composition has palladium dispersed on the surface, wherein the palladium dispersion comprises about 35.0% to about 46.1% after calcination in air at 800°C for 2 hours, or about 8.5% to about 13.0% after calcination in air at 1000°C for 10 hours, or about 3.9% to about 6.0% after calcination in air at 1100°C for 10 hours.

[0056] In a specific embodiment, the composition comprises a mixed oxide core consisting essentially of cerium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, and praseodymium oxide, and a rare earth coating of cerium oxide, neodymium oxide, or praseodymium oxide. This composition is aluminum oxide-free and exhibits higher palladium dispersion compared to compositions having a mixed oxide core but without or without a rare earth oxide coating.

[0057] In other specific embodiments, the composition comprises a mixed oxide core consisting essentially of cerium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, and yttrium oxide, and the rare earth coating is cerium oxide or neodymium oxide. This composition is free of aluminum oxide and exhibits higher palladium dispersion compared to compositions having a mixed oxide core but without or without a rare earth oxide coating.

[0058] In another specific embodiment, the composition comprises a mixed oxide core consisting essentially of cerium oxide, zirconium oxide, lanthanum oxide, and yttrium oxide, and the rare earth coating is cerium oxide or neodymium oxide. This composition is free of aluminum oxide and exhibits higher palladium dispersion compared to compositions having a mixed oxide core but without or without a rare earth oxide coating.

[0059] In some embodiments, the composition comprises a mixed oxide core comprising about 35% to about 60% cerium oxide, about 40% to about 65% zirconium oxide based on the total weight of the mixed oxide core, and optionally one or more of lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide, and is free of aluminum oxide. The mixed oxide core has a rare earth oxide coating on its surface, wherein the rare earth elements in the coating are selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. The composition also comprises palladium dispersed on the surface, wherein the palladium dispersion comprises about 35.0% to about 46.1% after calcination (aging) in air at 800°C for 2 hours, or about 8.5% to about 13.0% after calcination (aging) in air at 1000°C for 10 hours, or about 3.9% to about 6.0% after calcination (aging) in air at 1100°C for 10 hours. These further calcinations (or agings) are aging treatments performed after the preparation of the composition. These further calcinations (or aging) can be carried out independently.

[0060] In some embodiments, the composition comprises about 40% to about 60% cerium oxide based on the total weight of the composition, and about 1% to about 10% rare earth oxide coating based on the total weight of the composition, and has palladium dispersed on the surface. In these embodiments, the composition has a higher palladium dispersion compared to compositions having a mixed oxide core without or without a rare earth oxide coating. The palladium dispersion may be about 35.0% to about 46.1% after calcination (aging) in air at 800°C for 2 hours, or about 8.5% to about 13.0% after calcination (aging) in air at 1000°C for 10 hours, or about 3.9% to about 6.0% after calcination (aging) in air at 1100°C for 10 hours. These further calcinations (or agings) are aging treatments performed after the preparation of the composition. These further calcinations (or agings) may be performed independently.

[0061] In some embodiments, the palladium dispersion may be about 35.0% to about 46.1% after calcination (aging) in air at 800°C for 2 hours, or about 8.5% to about 12.3% after calcination (aging) in air at 1000°C for 10 hours, or about 3.9% to about 5.8% after calcination (aging) in air at 1100°C for 10 hours.

[0062] In some embodiments, the palladium dispersion may be about 40% after calcination (aging) in air at 800°C for 2 hours, about 10.0% after calcination (aging) in air at 1000°C for 10 hours, or about 4% after calcination (aging) in air at 1100°C for 10 hours.

[0063] The % of palladium dispersion does not refer to the percentage of surface area covered by palladium. Rather, it refers to the percentage of palladium atoms present as surface atoms. For example, theoretically, 100% palladium dispersion means that all palladium atoms (added to the composition) are present as surface atoms. Typically, this parameter is used to quantify the degree of sintering of palladium particles after calcination (aging).

[0064] As described herein, the calcination (aging) conditions are not cumulative. Palladium dispersion values ​​are achieved after calcining (aging) the composition, which comprises a mixed oxide core with a rare earth oxide coating, on which palladium is prepared. During its preparation, the composition is heat-treated or calcined before the addition of palladium, and a second calcination or heat treatment is performed after the addition of palladium. This process provides a “fresh” or “prepared” composition. The heat treatment or calcination during the preparation of the composition after the addition of palladium is performed at about 500°C to about 650°C (preferably 550°C) for about 2 to 5 hours (preferably about 2 hours). Aging calcination is performed under different conditions independent of those specified herein to test the degree of sintering of the palladium particles. These further calcination or aging treatments may be performed in air at about 800°C for about 2 hours, in air at about 1000°C for about 10 hours, or in air at about 1100°C for about 10 hours, and are used to test palladium sintering during simulated use.

[0065] In certain embodiments with rhodium dispersion, the composition comprising a mixed oxide core and a rare earth coating contains zirconium oxide, cerium oxide, lanthanum oxide, and neodymium oxide. In these embodiments, the mixed oxide core may contain zirconium oxide, cerium oxide, lanthanum oxide, and neodymium oxide, and the rare earth element in the rare earth oxide coating may be cerium, neodymium, or a mixture thereof. In this embodiment, the mixed oxide core of the composition may have a Ce / Zr / La / Nd ratio of approximately 18.5 wt% to approximately 21.5 wt% Ce, approximately 74 wt% to approximately 77 wt% Zr, approximately 1.5 wt% to approximately 2.0 wt% La, and approximately 2.0 wt% to approximately 2.5 wt% Nd, based on equivalent oxides, and the rare earth oxide coating is substantially composed of one or both of CeO2 and Nd2O3. In some of these embodiments, the rare earth oxide coating comprises approximately 3 wt% to approximately 6 wt% based on the total weight of the composition.

[0066] In specific embodiments with palladium dispersion, the composition comprising a mixed oxide core and a rare earth coating contains zirconium oxide, cerium oxide, lanthanum oxide, neodymium oxide, and praseodymium oxide. In these embodiments, the mixed oxide core may contain zirconium oxide, cerium oxide, lanthanum oxide, neodymium oxide, and praseodymium oxide, and the rare earth element in the rare earth oxide coating may be cerium, neodymium, or praseodymium. In this embodiment, the mixed oxide core of the composition may have a Ce / Zr / La / Nd / Pr ratio of approximately 36.5 wt% to approximately 41.5 wt% Ce, approximately 50 wt% to approximately 53 wt% Zr, approximately 2 wt% to approximately 2.2 wt% La, approximately 1 wt% to approximately 4.3 wt% Nd, and approximately 1 wt% to approximately 4.3 wt% Pr, based on equivalent oxides, and the rare earth oxide coating is substantially composed of CeO2, Nd2O3, and Pr6O2. 11 One or two of the components. In some of these embodiments, the rare earth oxide coating is about 1% to about 6% by weight based on the total weight of the composition.

[0067] In certain embodiments with palladium dispersion, the composition comprising a mixed oxide core and a rare earth coating contains zirconium oxide, cerium oxide, lanthanum oxide, yttrium oxide, and optionally neodymium oxide. In these embodiments, the mixed oxide core may contain zirconium oxide, cerium oxide, lanthanum oxide, yttrium oxide, and optionally neodymium oxide, and the rare earth element in the rare earth oxide coating may be cerium or neodymium. In this embodiment, the mixed oxide core of the composition may have a Ce / Zr / La / Nd / Y ratio of approximately 36.5 wt% to approximately 41.5 wt% Ce, approximately 50 wt% to approximately 53 wt% Zr, approximately 3.5 wt% to approximately 5.5 wt% La, approximately 0 wt% to approximately 1.5 wt% Nd, and approximately 1.8 wt% to approximately 5.6 wt% Y, based on equivalent oxides, and the rare earth oxide coating is substantially composed of CeO2 or Nd2O3. In some of these embodiments, the rare earth oxide coating is approximately 3 wt% to approximately 6 wt% based on the total weight of the composition.

[0068] All of the compositions described above are free of alumina. All of the compositions described above can be combined with the rhodium or palladium dispersion percentages described above after aging.

[0069] The compositions disclosed herein can be used as part of a catalyst system or incorporated into a catalyst composition. These catalysts can be used in the purification of gas emissions. Higher rhodium or palladium dispersions make these compositions particularly suitable for use as part of a catalyst system or as a catalyst support in catalysis. The catalysts are used in transportation vehicles to purify exhaust gases and for other related applications.

[0070] This document also discloses methods for producing these compositions comprising a mixed oxide core having a rare earth oxide coating on its surface, and the compositions having rhodium or palladium on the surface. These compositions, as disclosed herein, having high rhodium or palladium dispersion are produced by a method for providing a mixed oxide core having a rare earth oxide coating, and provide high rhodium or palladium dispersion. Figure 1 This is a flowchart of an embodiment of a method for preparing these compositions with high rhodium or palladium dispersion.

[0071] The method comprises the following steps: (a) providing a mixed oxide powder of one or more selected from cerium oxide, zirconium oxide, and optionally rare earth oxides, said rare earth oxides being selected from neodymium, lanthanum, praseodymium, and yttrium; (b) dissolving a rare earth salt in water, wherein the rare earth element of the salt is selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof to provide a rare earth solution; (c) combining the rare earth solution with the mixed oxide powder and mixing to provide a homogeneous powder mixture; and (d) calcining the homogeneous powder mixture at about 400 to about 600°C (preferably 500°C) for about 2 hours to 5 hours (preferably 3 hours) to provide a mixed oxide core, said mixed oxide core being selected from neodymium, lanthanum, praseodymium, and yttrium; The mixed oxide core has a rare earth oxide coating on its surface, wherein the rare earth element in the coating is selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof; (e) a rhodium or palladium salt solution is added to the mixed oxide core having the rare earth oxide coating; and (f) calcination is performed at about 500°C to about 650°C (preferably 550°C) for about 2 hours to about 5 hours (preferably 2 hours) to provide a composition comprising a mixed oxide core having a rare earth oxide coating on its surface and having a higher rhodium or palladium dispersion relative to a composition comprising a mixed oxide core without or without a rare earth oxide coating. In one embodiment, the calcination “first calcination” in step (d) is performed at a temperature of about 500°C for about 3 hours. In one embodiment, the calcination “second calcination” in step (f) is performed at a temperature of about 550°C for about 2 hours. These two specific embodiments, or steps (d) and (f), may be combined together.

[0072] The mixed oxide powder includes zirconium oxide powder and cerium oxide powder, and one or more rare earth oxide powders optionally selected from neodymium, lanthanum, praseodymium, and yttrium. The mixed oxide powder of step (a) can be divided into equal mass fractions, such as... Figure 1 The flowchart is shown.

[0073] The rare earth salt in step (b) is any rare earth salt that is soluble in water. The salt can be an inorganic salt or an organic acid salt. For example, water-soluble salts can be chlorides, sulfates, nitrates, ammonium nitrates, acetates, etc. In some embodiments, the rare earth salt can be a chloride salt, a nitrate, or an ammonium nitrate salt. The rare earth salt dissolves in water to produce a rare earth salt solution. As described herein, the rare earth element of the salt can be cerium, lanthanum, praseodymium, neodymium, yttrium, or a mixture thereof. In some embodiments, the rare earth element of the salt is cerium, neodymium, praseodymium, or a mixture thereof. The rare earth salt solution can have any suitable rare earth concentration in g / L.

[0074] In some embodiments, the rare earth salt may be cerium nitrate, cerium ammonium nitrate, neodymium nitrate, neodymium acetate, praseodymium nitrate, praseodymium acetate, or any mixture thereof.

[0075] Rare earth solutions are combined with and mixed with mixed oxide powders to provide a homogeneous mixture. Alternatively, if the mixed oxide powder is divided into small equal portions and individually combined with a small amount of rare earth salt solution, then all portions of the mixed oxide powder are then combined and mixed to obtain a homogeneous mixture. The rare earth salt solution provides a rare earth oxide coating on the mixed oxide core. It can also be described as the rare earth salt solution providing surface modification of the mixed oxide.

[0076] The homogeneous powder mixture is calcined at a temperature of about 400°C to about 600°C (about 500°C in one embodiment) for about 2 to 5 hours (about 3 hours in one embodiment) to provide a mixed oxide core having a rare earth oxide coating on its surface, wherein the rare earth elements in the coating are selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. Thus, after calcination, the mixed oxide core has a rare earth oxide coating on its surface, wherein the rare earth elements in the coating are selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof. Calcination may occur in a mixture of 2% O2 and 98% N2 gas.

[0077] Following calcination, a precious metal is added to a mixed oxide core having a rare earth coating. In some embodiments, rhodium or palladium is added to the mixed oxide core having a rare earth coating after calcination. Generally, rhodium or palladium is added to the mixed oxide core having a rare earth oxide coating as a solution of rhodium or palladium salt. After the addition / impregnation of rhodium or palladium, the composition is calcined at about 500°C to about 650°C (about 550°C in one embodiment) for about 2 hours to about 5 hours (about 2 hours in one embodiment) to provide a composition comprising a mixed oxide core having a rare earth oxide coating on its surface and exhibiting a higher rhodium or palladium dispersion compared to a composition comprising a mixed oxide core without a rare earth oxide coating.

[0078] In some embodiments, the mixed oxide powder comprises cerium oxide, zirconium oxide, neodymium oxide, and lanthanum oxide, and a rhodium salt is added in step (e). In other embodiments, the mixed oxide powder comprises cerium oxide, zirconium oxide, neodymium oxide, lanthanum oxide, and praseodymium oxide, and a palladium salt is added in step (e). In an additional embodiment, the mixed oxide powder comprises cerium oxide, zirconium oxide, neodymium oxide, lanthanum oxide, and yttrium oxide, and a palladium salt is added in step (e). In yet another embodiment, the mixed oxide powder comprises cerium oxide, zirconium oxide, lanthanum oxide, and yttrium oxide, and a palladium salt is added in step (e).

[0079] In a specific embodiment, rhodium loading / addition is performed as follows. Approximately 0.5 wt% Rh₂O₃ is loaded by impregnating 4.19 g of each sample (i.e., a mixed oxide core with a rare earth oxide coating) with a measured amount of rhodium nitrate solution (14.21% rhodium). The rhodium nitrate is then diluted in water to achieve the incipient wetness of each sample of the composition disclosed herein. The diluted rhodium nitrate solution is added dropwise to the mixed oxide powder with the rare earth coating while mixing. The powder is then dried and calcined at 550°C for 2 hours.

[0080] In a specific implementation, palladium loading / addition is performed as follows. Approximately 1.6 wt% PdO is loaded by impregnating 7.92 g of each sample (i.e., a mixed oxide core with a rare earth oxide coating) with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate is diluted in water to achieve initial wetness for each sample. The diluted palladium nitrate solution is added dropwise to the mixed oxide powder with the rare earth coating while mixing. The powder is then dried and calcined at 550°C for 2 hours.

[0081] The methods described herein provide compositions having rhodium or palladium on a surface and having a high rhodium or palladium dispersion and having any or all of the properties and characteristics described above.

[0082] The compositions disclosed herein can be used as part of a catalyst system or as part of a catalyst composition. These catalysts are used in transportation vehicles to purify exhaust gases and for other related applications.

[0083] The following examples illustrate the inventive methods for preparing compositions of rhodium or palladium dispersed on a surface as described herein, and further detail their characteristics, although the scope of the invention is by no means limited thereto.

[0084] Figure 1 This is a flowchart of an embodiment of a method for producing a composition comprising a mixed oxide core having a rare earth oxide coating on the core surface, and the composition having rhodium or palladium on the surface has high rhodium or palladium dispersion.

[0085] The rhodium and palladium dispersions in the following examples were measured using the methods described above for measuring rhodium and palladium dispersions.

[0086] Comparative Example 1: Mixed oxides containing Rh but without further surface modification (no rare earth oxide coating)

[0087] Perform the following:

[0088] 1) A mixed oxide was prepared without further surface modification with a rare earth coating (the composition is essentially composed of Ce / Zr / La / Nd in the ratio of about 20.8 wt% Ce, about 72.2 wt% Zr, about 1.7 wt% La and about 5.3 wt% Nd).

[0089] Rhodium loading / addition was performed as follows. Approximately 0.5 wt% Rh₂O₃ was loaded by impregnating a measured amount of rhodium nitrate solution onto a sample of mixed oxide. The rhodium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted rhodium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550°C for 2 hours.

[0090] Comparative Example 2: Mixed oxides containing Pd but without further surface modification (no rare earth oxide coating)

[0091] Perform the following:

[0092] 1) A mixed oxide composition comprising Ce / Zr / La / Nd / Pr in a ratio of about 40 wt% Ce, 50 wt% Zr, 2 wt% La, 4 wt% Nd and 4 wt% Pr was prepared without further surface modification by a rare earth coating.

[0093] Palladium loading / addition was performed as follows. Approximately 1.6 wt% PdO was loaded by impregnating a measured amount of palladium nitrate solution onto a sample of mixed oxide. The palladium nitrate was then diluted in water to achieve the initial wetness of each sample of the compositions disclosed herein. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550°C for 2 h.

[0094] Example 1: A mixed oxide with Rh and Nd2O3 coating (a mixed oxide with Nd2O3 surface modification)

[0095] Perform the following:

[0096] 1) 12.25 g of mixed oxide (a composition containing Ce / Zr / La / Nd in a ratio of about 21.4 wt% Ce, about 74.4 wt% Zr, about 1.8 wt% La and about 2.4 wt% Nd) was divided into equal portions.

[0097] 2) Combine 1.73 g of nitric acid Nd solution (Nd2O3=306.0 g / L, density=1.47 g / mL) with 3.8 mL of DI water.

[0098] 3) Slowly add the diluted Nd nitric acid solution to each mixed oxide portion.

[0099] 4) Combine and mix all the parts to produce a homogeneous mixture.

[0100] 5) The powder is calcined at 500°C to produce an oxide carrier.

[0101] Rhodium loading / addition was performed as follows. Approximately 0.5 wt% Rh₂O₃ was loaded by impregnating 4.19 g of a mixed oxide sample with a rare earth coating with a measured amount of rhodium nitrate solution (14.21% rhodium). The rhodium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted rhodium nitrate solution was added dropwise to the mixed oxide powder with the rare earth coating while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0102] Example 2: A mixed oxide with Rh coatings of Nd2O3 and CeO2 (a mixed oxide with Nd2O3 and CeO2 surface modified)

[0103] Perform the following:

[0104] 1) Combine 1.15 g of cerium ammonium nitrate (CAN) and 1.75 g of nitric acid Nd solution (Nd2O3=297.9 g / L, density=1.45 g / mL) with 2.9 mL of DI water.

[0105] 2) The Ce / Nd solution was added to 11.88 g of CZO (a composition containing Ce / Zr / La / Nd in a ratio of about 18.93 wt% Ce, about 76.81 wt% Zr, about 1.81 wt% La and about 2.45 wt% Nd) to obtain a homogeneous mixture.

[0106] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0107] Rhodium loading / addition was performed as follows. Approximately 0.5 wt% Rh₂O₃ was loaded by impregnating 4.19 g of a mixed oxide sample with a rare earth coating with a measured amount of rhodium nitrate solution (14.21% rhodium). The rhodium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted rhodium nitrate solution was added dropwise to the mixed oxide powder with the rare earth coating while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0108] Summary of Comparative Example 1 and Examples 1 and 2

[0109] Table 1 below summarizes the mixed oxide compositions before any surface modification (i.e., before the addition of the rare earth oxide coating). Comparative Example 1 had no surface modification (i.e., no rare earth oxide coating).

[0110] Table 1: Mixed oxide compositions of Comparative Example 1 and Examples 1 and 2

[0111] Table 2 below summarizes the mixed oxide compositions of Examples 1 and 2 and Comparative Example 1 after surface modification (i.e., after the addition of rare earth oxide coating).

[0112] Table 2: Mixed oxide compositions of Examples 1 and 2 and Comparative Example 1 after surface modification

[0113] Table 3 below summarizes the rhodium dispersion results of Comparative Example 1 and Examples 1 and 2 with surface modification (i.e. rare earth oxide coating).

[0114] Table 3: Rhodium dispersion results of Comparative Example 1 and Examples 1 and 2

[0115] As summarized in Table 3, Examples 1 and 2 exhibited significantly higher rhodium dispersions under different aging (further calcination) conditions compared to Comparative Example 1. With these higher rhodium dispersions, this composition provides an improved catalytic material for use in catalytic converters and vehicles to purify gases.

[0116] Example 3: Mixed oxide with Pd and Nd2O3 coating (Nd2O3 surface-modified mixed oxide)

[0117] Perform the following:

[0118] 1) Combine 0.389 g of nitric acid Nd solution (Nd2O3=297.9 g / L, density=1.45 g / mL) with 4.2 mL of DI water.

[0119] 2) The Nd solution was added to 7.92 g of CZO (a composition comprising Ce / Zr / La / Nd / Pr in a ratio of about 40.40 wt% Ce, about 50.51 wt% Zr, about 2.02 wt% La, about 3.03 wt% Nd and about 4.04 wt% Pr) to obtain a homogeneous mixture.

[0120] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0121] The palladium loading / addition was as follows. Approximately 1.6 wt% PdO was loaded by impregnating 7.92 g of a mixed oxide sample with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0122] Example 4: Mixed oxide with Pd and Nd2O3 coating (Nd2O3 surface-modified mixed oxide)

[0123] Perform the following:

[0124] 1) Combine 0.779 g of nitric acid Nd solution (Nd2O3=297.9 g / L, density=1.45 g / mL) with 3.0 mL of DI water.

[0125] 2) The Nd solution was added to 7.84 g of CZO (a composition comprising Ce / Zr / La / Nd / Pr in a ratio of about 40.82 wt% Ce, about 51.02 wt% Zr, about 2.04 wt% La, about 2.04 wt% Nd and about 4.08 wt% Pr) to obtain a homogeneous mixture.

[0126] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0127] The palladium loading / addition was as follows. Approximately 1.6 wt% PdO was loaded by impregnating 7.92 g of a mixed oxide sample with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0128] Example 5: A mixed oxide with Pd and Nd2O3 coatings (a mixed oxide with Nd2O3 surface modification)

[0129] Perform the following:

[0130] 1) Combine 1.168 g of nitric acid Nd solution (Nd2O3=297.9 g / L, density=1.45 g / mL) with 3.8 mL of DI water.

[0131] 2) The Nd solution was added to 7.76 g of CZO (a composition comprising Ce / Zr / La / Nd / Pr in a ratio of about 41.24 wt% Ce, about 51.55 wt% Zr, about 2.06 wt% La, about 1.03 wt% Nd and about 4.12 wt% Pr) to obtain a homogeneous mixture.

[0132] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0133] The palladium loading / addition was as follows. Approximately 1.6 wt% PdO was loaded by impregnating 7.92 g of a mixed oxide sample with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0134] Example 6: Contains Pd and Pr6O 11 The coating is a mixed oxide (Pr6O) 11 Surface-modified mixed oxides)

[0135] Perform the following:

[0136] 1) Add 0.562g of nitric acid Pr solution (Pr6O) 11 =313.85 g / L, density=1.47 g / mL) combined with 6.5 mL of DI water.

[0137] 2) Add the Pr solution to 11.88 g of CZO (a composition comprising Ce / Zr / La / Nd / Pr in a ratio of about 40.40 wt% Ce, about 50.51 wt% Zr, about 2.02 wt% La, about 4.04 wt% Nd and about 3.03 wt% Pr) to obtain a homogeneous mixture.

[0138] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0139] The palladium loading / addition was as follows. Approximately 1.6 wt% PdO was loaded by impregnating 7.92 g of a mixed oxide sample with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0140] Example 7: Contains Pd and Pr6O 11 The coating is a mixed oxide (Pr6O) 11 Surface-modified mixed oxides)

[0141] Perform the following:

[0142] 1) Add 1.124g of nitric acid Pr solution (Pr6O) 11 =313.85 g / L, density=1.47 g / mL) combined with 4.6 mL of DI water.

[0143] 2) Add the Pr solution to 11.76 g of CZO (a composition comprising Ce / Zr / La / Nd / Pr in a ratio of about 40.82 wt% Ce, about 51.02 wt% Zr, about 2.04 wt% La, about 4.08 wt% Nd and about 2.04 wt% Pr) to obtain a homogeneous mixture.

[0144] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0145] The palladium loading / addition was as follows. Approximately 1.6 wt% PdO was loaded by impregnating 7.92 g of a mixed oxide sample with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0146] Example 8: Contains Pd and Pr6O 11 The coating is a mixed oxide (Pr6O) 11 Surface-modified mixed oxides)

[0147] Perform the following:

[0148] 1) Add 1.686g of nitric acid Pr solution (Pr6O) 11 =313.85 g / L, density=1.47 g / mL) combined with 5.6 mL of DI water.

[0149] 2) Add the Pr solution to 11.64 g of CZO (a composition comprising Ce / Zr / La / Nd / Pr in a ratio of about 41.24 wt% Ce, about 51.55 wt% Zr, about 2.06 wt% La, about 4.12 wt% Nd and about 1.03 wt% Pr) to obtain a homogeneous mixture.

[0150] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0151] The palladium loading / addition was as follows. Approximately 1.6 wt% PdO was loaded by impregnating 7.92 g of a mixed oxide sample with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0152] Example 9: A mixed oxide with Pd and CeO2 coating (a mixed oxide with CeO2 surface modification)

[0153] Perform the following:

[0154] 1) Combine 1.60 g of cerium ammonium nitrate (CAN) with 5.9 mL of DI water.

[0155] 2) Add the Ce solution to 9.50 g of CZO (a composition comprising Ce / Zr / La / Nd / Pr in a ratio of about 36.84 atomic% Ce, about 52.63 wt% Zr, about 2.11 wt% La, about 4.21 wt% Nd and about 4.21 wt% Pr) to obtain a homogeneous mixture.

[0156] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0157] The palladium loading / addition was as follows. Approximately 1.6 wt% PdO was loaded by impregnating 7.92 g of a mixed oxide sample with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0158] Summary of Comparative Example 2 and Examples 3-9

[0159] Table 4 below summarizes the mixed oxide compositions before any surface modification (i.e., before the addition of the rare earth oxide coating). Comparative Example 2 had no surface modification (i.e., no rare earth oxide coating).

[0160] Table 4: Mixed oxide compositions of Comparative Example 2 and Examples 3-9

[0161] Table 5 below summarizes the mixed oxide compositions of Examples 3-9 and Comparative Example 2 after surface modification (i.e., after the addition of rare earth oxide coating).

[0162] Table 5: Mixed oxide compositions of Examples 3-9 and Comparative Example 2 after surface modification

[0163] Table 6 below summarizes the palladium dispersion results of Comparative Example 3 and Examples 3-9 with surface modification (i.e., rare earth oxide coating).

[0164] Table 6: Palladium dispersion results of Comparative Example 2 and Examples 3-9

[0165] As summarized in Table 6, Examples 3-9 exhibited significantly higher percentages of palladium dispersion when compared to Comparative Example 2 under different aging (further calcination) conditions. With these higher percentages of palladium dispersion, this composition provides an improved catalytic material for use in catalytic converters and vehicles to purify gases.

[0166] Example 10: A mixed oxide with Pd and CeO2 coating (a mixed oxide with CeO2 surface modification)

[0167] Perform the following:

[0168] 1) Combine 2.40 g of cerium ammonium nitrate (CAN) with 8.5 mL of DI water.

[0169] 2) Add the Ce solution to 14.25 g of CZO (a composition comprising Ce / Zr / La / Y in a ratio of about 36.84 wt% Ce, about 52.63 wt% Zr, about 5.26 wt% La and about 5.26 wt% Y) to obtain a homogeneous mixture.

[0170] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0171] The palladium loading / addition was as follows. Approximately 1.6 wt% PdO was loaded by impregnating 7.92 g of a mixed oxide sample with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0172] Example 11: Mixed oxide with Pd and Nd2O3 coating (Nd2O3 surface-modified mixed oxide)

[0173] Perform the following:

[0174] 1) Combine 2.34 g of nitric acid Nd solution (Nd2O3=297.9 g / L, density=1.45 g / mL) with 8.5 mL of DI water.

[0175] 2) The Nd solution was added to 15.52 g of CZO (a composition comprising Ce / Zr / La / Nd / Y in the amounts of about 41.24 wt% Ce, about 51.55 wt% Zr, about 4.12 wt% La, about 1.03 wt% Nd and about 2.06 wt% Y) to obtain a homogeneous mixture.

[0176] 3) The powder is calcined at 500°C to produce an oxide carrier.

[0177] The palladium loading / addition was as follows. Approximately 1.6 wt% PdO was loaded by impregnating 7.92 g of a mixed oxide sample with a measured amount of palladium nitrate solution (17.99% palladium). The palladium nitrate was then diluted in water to achieve initial wetness of the sample. The diluted palladium nitrate solution was added dropwise to the mixed oxide powder while mixing. The powder was then dried and calcined at 550 °C for 2 h.

[0178] Summary of Examples 10 and 11

[0179] Table 7 below summarizes the mixed oxide compositions before any surface modification (i.e., before the addition of rare earth oxide coatings).

[0180] Table 7: Mixed oxide compositions of Examples 10 and 11

[0181] Table 8 below summarizes the mixed oxide compositions of Examples 10 and 11 after surface modification (i.e., after the addition of rare earth oxide coatings).

[0182] Table 8: Mixed oxide compositions of Examples 10 and 11

[0183] Table 9 below summarizes the palladium dispersion results of Examples 10 and 11 with surface modification (i.e., rare earth oxide coating).

[0184] Table 9: Palladium dispersion results in Examples 10 and 11

[0185] As summarized in Table 9, Examples 10 and 11 exhibit significantly higher percentages of palladium dispersion under different aging (further calcination) conditions. With these higher percentages of palladium dispersion, this composition provides an improved catalytic material for use in catalytic converters and vehicles to purify gases.

[0186] Unless otherwise stated, all numerical values ​​used in the specification and claims to indicate the amount, properties, such as molecular weight, reaction conditions, etc., of an ingredient should be understood to be modified by the term "about" in all cases. Therefore, unless the contrary is indicated, the numerical parameters listed in the following specification and appended claims are approximate values ​​and may vary depending on the desired properties sought to be obtained.

[0187] While the numerical ranges and parameters listed for the broad range of techniques are approximations, the values ​​presented in the specific embodiments are reported as precisely as possible. However, any numerical value inherently contains some error that is necessarily introduced by the standard deviation found in their respective test measurements.

[0188] It will be clear that the compositions and methods described herein are highly suitable for achieving the results and advantages mentioned and inherent therein. Those skilled in the art will recognize that the methods and systems within this specification can be implemented in many ways and are therefore not limited to the foregoing exemplary embodiments and examples. In this regard, any number of features of the different embodiments described herein can be combined into a single embodiment, and alternative embodiments having fewer or more features than all those described herein are possible.

[0189] While various embodiments have been described for the purposes of this disclosure, various changes and modifications may be made fully within the scope of this disclosure. Many other changes may be made, which will be readily apparent to those skilled in the art and are embodied in the spirit of this disclosure.

Claims

1. A composition comprising a mixed oxide core, said mixed oxide core comprising about 15 wt% to about 60 wt% cerium oxide and about 40 wt% to about 85 wt% zirconium oxide based on the total weight of said mixed oxide core, and free of aluminum oxide. The mixed oxide core has a rare earth oxide coating, wherein the rare earth elements in the coating are selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof, and the composition has rhodium or palladium on its surface, wherein the composition has a higher rhodium or palladium dispersion than a composition having a mixed oxide core but without a rare earth oxide coating.

2. A composition comprising a mixed oxide core, said mixed oxide core comprising about 15% to about 25% by weight of cerium oxide based on the total weight of said mixed oxide core; about 70% to about 85% by weight of zirconium oxide based on the total weight of said mixed oxide core; optionally one or more of lanthanum oxide, neodymium oxide, praseodymium oxide and yttrium oxide; and free of aluminum oxide. The mixed oxide core has a rare earth oxide coating, wherein the rare earth elements in the coating are selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof, and the composition has rhodium dispersed on the surface. The rhodium content is approximately 18.5% to approximately 28.6% when dispersed in air and calcined at 800°C for 2 hours, or approximately 14.3% to approximately 21.9% when calcined in air at 1000°C for 10 hours, or approximately 10.3% to approximately 16.5% when calcined in air at 1100°C for 10 hours.

3. A composition comprising a mixed oxide core, said mixed oxide core comprising about 35 wt% to about 60 wt% cerium oxide based on the total weight of said mixed oxide core; about 40 wt% to about 65 wt% zirconium oxide based on the total weight of said mixed oxide core; optionally one or more of lanthanum oxide, neodymium oxide, praseodymium oxide and yttrium oxide, and free of aluminum oxide. The mixed oxide core has a rare earth oxide coating, wherein the rare earth elements in the coating are selected from cerium, lanthanum, neodymium, praseodymium, yttrium, and mixtures thereof; and the composition has palladium dispersed on the surface. The palladium content is approximately 35.0% to approximately 46.1% when dispersed in air and calcined at 800°C for 2 hours, or approximately 8.5% to approximately 13.0% when calcined in air at 1000°C for 10 hours, or approximately 3.9% to approximately 6.0% when calcined in air at 1100°C for 10 hours.

4. The composition of claim 1, wherein the mixed oxide core comprises about 15% to about 25% cerium oxide, about 70% to about 85% zirconium oxide, and one or more of lanthanum oxide, neodymium oxide, praseodymium oxide and yttrium oxide; the composition has rhodium on its surface and has higher rhodium dispersion than a composition having a mixed oxide core but without a rare earth oxide coating.

5. The composition of claim 1, wherein the mixed oxide core comprises about 35% to about 60% cerium oxide, about 40% to about 65% zirconium oxide, and one or more of lanthanum oxide, neodymium oxide, praseodymium oxide and yttrium oxide; the composition has palladium on its surface and has a higher palladium dispersion than a composition having a mixed oxide core but without a rare earth oxide coating.

6. The composition according to claim 1 or 4, having rhodium dispersed on the surface, wherein the rhodium dispersion is about 18.5% to about 28.6% after calcination in air at 800°C for 2 hours, or about 14.3% to about 21.9% after calcination in air at 1000°C for 10 hours, or about 10.3% to about 16.5% after calcination in air at 1100°C for 10 hours.

7. The composition according to claim 1 or 5, having palladium dispersed on the surface, wherein the palladium dispersion is about 35.0% to about 46.1% after calcination in air at 800°C for 2 hours, or about 8.5% to about 13.0% after calcination in air at 1000°C for 10 hours, or about 3.9% to about 6.0% after calcination in air at 1100°C for 10 hours.

8. The composition of claim 1, wherein the composition comprises a mixed oxide core consisting substantially of cerium oxide, zirconium oxide and additional rare earth oxides selected from lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide and mixtures thereof; The rare earth oxide coating is one or two of cerium oxide, neodymium oxide, and praseodymium oxide; When palladium is present, the palladium content is about 35.0% to about 46.1% after being calcined in air at 800°C for 2 hours, or about 8.5% to about 13.0% after being calcined in air at 1000°C for 10 hours, or about 3.9% to about 6.0% after being calcined in air at 1100°C for 10 hours; or When rhodium is present, the rhodium content is about 18.5% to about 28.6% after being calcined in air at 800°C for 2 hours, or about 14.3% to about 21.9% after being calcined in air at 1000°C for 10 hours, or about 10.3% to about 16.5% after being calcined in air at 1100°C for 10 hours.

9. The composition of claim 6, wherein the mixed oxide core is substantially composed of cerium oxide, zirconium oxide, lanthanum oxide, and neodymium oxide, and Rare earth coatings are one or both of cerium oxide and neodymium oxide.

10. The composition of claim 7, wherein the mixed oxide core is substantially composed of cerium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, and praseodymium oxide, and Rare earth coatings are cerium oxide, neodymium oxide, or praseodymium oxide.

11. The composition of claim 7, wherein the mixed oxide core is substantially composed of cerium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, and yttrium oxide, and The rare earth coating is cerium oxide or neodymium oxide.

12. The composition of claim 7, wherein the mixed oxide core is substantially composed of cerium oxide, zirconium oxide, lanthanum oxide, and yttrium oxide, and The rare earth coating is cerium oxide or neodymium oxide.

13. The oxide composition of claim 1, wherein the composition comprises about 20% to about 25% cerium oxide based on the total weight of the composition, and about 1% to about 10% rare earth oxide coating based on the total weight of the composition; and has rhodium on the surface.

14. The composition of claim 1, wherein the composition comprises about 40% to about 60% cerium oxide based on the total weight of the composition, and about 1% to about 10% rare earth oxide coating based on the total weight of the composition; and has palladium on the surface.

15. The composition according to any one of claims 1-11, wherein the rare earth oxide coating is about 1% to about 10% by weight based on the total weight of the composition.

16. The composition of claim 15, wherein the rare earth oxide coating is a single rare earth oxide selected from cerium, lanthanum, neodymium, and praseodymium, and the rare earth oxide coating comprises about 1% to about 5% by weight based on the total weight of the composition.

17. The composition of claim 15, wherein the rare earth oxide coating is two rare earth oxides selected from cerium, lanthanum, neodymium and praseodymium, and each rare earth oxide in the coating is present in an amount of about 1% to about 5% by weight based on the total weight of the composition.

18. The composition according to any one of claims 1-7, wherein the mixed oxide core comprises La2O3, Y2O3, Nd2O3 and Pr6O 11 One or more of the following, as well as CeO2 and ZrO2, and the rare earth oxide coating is CeO2, Nd2O3 and Pr6O 11 One or two of them.

19. The composition of claim 1, wherein rhodium or palladium is present as an oxide and the composition comprises about 0.5 wt% Rh2O3 or about 1.6 wt% PbO, based on the total weight of the composition.

20. A catalyst composition comprising the composition of any one of claims 1-19.

21. A method for producing a composition, the method comprising the following steps: (a) Provides a mixed oxide powder of one or more of cerium oxide, zirconium oxide and optional rare earth oxides, wherein the rare earth oxides are selected from neodymium, lanthanum, praseodymium and yttrium; (b) Dissolving a rare earth salt in water, wherein the rare earth element of the salt is selected from cerium, lanthanum, neodymium, praseodymium, yttrium and mixtures thereof to provide a rare earth solution; (c) Combining and mixing rare earth solutions with mixed oxide powders to provide a homogeneous powder mixture; (d) Calcination of a homogeneous powder mixture at about 400°C to about 600°C for about 2 to about 5 hours to provide a mixed oxide core having a rare earth oxide coating on its surface, wherein the rare earth of the coating is selected from cerium, lanthanum, neodymium, praseodymium, yttrium and mixtures thereof; (e) Adding a rhodium or palladium salt solution to a mixed oxide core with a rare earth oxide coating; and (f) Calcination at about 500°C to about 650°C for about 2 hours to about 5 hours to provide a composition comprising a mixed oxide core having a rare earth oxide coating on its surface and having a higher rhodium or palladium dispersion relative to a composition comprising a mixed oxide core but without a rare earth oxide coating.

22. The method of claim 21, wherein the rare earth salt in step (b) is a Ce salt, Nd salt, Pr salt or a mixture thereof, and the rare earth oxide coating is cerium oxide, neodymium oxide, praseodymium oxide or a combination thereof.

23. The method of claim 22, wherein the salt is a nitrate.

24. The method of claim 21, wherein: The mixed oxide powder comprises cerium oxide, zirconium oxide, neodymium oxide, and lanthanum oxide, and a rhodium salt is added in step (e); or The mixed oxide powder comprises cerium oxide, zirconium oxide, neodymium oxide, lanthanum oxide, and praseodymium oxide, and a palladium salt is added in step (e); or The mixed oxide powder comprises cerium oxide, zirconium oxide, neodymium oxide, lanthanum oxide, and yttrium oxide, and a palladium salt is added in step (e); or The mixed oxide powder comprises cerium oxide, zirconium oxide, lanthanum oxide and yttrium oxide, and a palladium salt is added in step (e).

25. The method of claim 21, wherein the calcination in step (d) is carried out in a mixture of 2% O2 and 98% N2 gas.

26. A composition prepared by any one of claims 21-25.

27. A catalyst composition comprising the composition of claim 26.

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