High oxygen storage capacity cerium and zirconium containing oxides

Abstract

This specification discloses compositions having improved oxygen storage capacity (OSC). The high-OSC compositions comprise zirconium oxide, cerium oxide, and optionally one or more rare earth oxides other than cerium. These optionally added rare earth oxides may be yttrium oxide, lanthanum oxide, neodymium oxide, praseodymium oxide, or mixtures thereof. These compositions have an oxygen storage capacity of approximately 40 μmol-O2 / g to approximately 300 μmol-O2 / g after calcination at approximately 900°C in air for approximately 5 hours. Methods for producing these compositions having improved oxygen storage capacity (OSC) are further disclosed. The compositions may be used as catalyst supports or as part of a catalyst system.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application was filed as a PCT international patent application on March 25, 2024 (March 24, 2024 being a Sunday), claiming the priority and benefit of U.S. Provisional Patent Application No. 63 / 492,135, filed on March 24, 2023, the disclosure of which is hereby incorporated by reference in its entirety.

[0002] This application relates to a composition comprising zirconium oxide, cerium oxide, and optionally one or more rare earth oxides other than cerium, which exhibits a high oxygen storage capacity. This mixed oxide composition surprisingly exhibits an improved oxygen storage capacity (OSC) even after aging at high temperatures. This application further relates to a method for producing this composition and its use.

Background Art

[0003] Oxygen storage / release (OSC) capacity is an important property for many catalysts. For example, catalysts for vehicle exhaust gas purification are composed of catalyst materials that have the property of absorbing oxygen in an oxidizing atmosphere and desorbing oxygen in a reducing atmosphere. Due to this oxygen adsorption - desorption ability, the catalyst material can purify harmful components in exhaust gases such as hydrocarbons, carbon monoxide, nitrogen oxides, etc. with excellent efficiency. These catalysts can oxidize carbon monoxide and hydrocarbons present in the exhaust gas and can also reduce nitrogen oxides present in the exhaust gas. Therefore, these catalyst materials are mainly used in the catalytic converters of vehicles for purifying exhaust gases.

[0004] Generally, catalyst materials require a sufficiently large specific surface area and sufficiently high oxygen adsorption / desorption capacity even at high temperatures. Cold start emissions are the most toxic part of the engine operating cycle. Furthermore, more than 70% of total harmful gas emissions from an average single run occur during the vehicle's cold start. Catalysts with lower light-off temperatures can more effectively remove engine exhaust gases in the initial stages of engine starting. High oxygen storage capacity at low temperatures (e.g., 400°C) results in a better catalyst light-off temperature. Having a catalyst with high oxygen storage capacity at low temperatures also leads to a better catalyst light-off temperature. As hybrid internal combustion / electric vehicles become more widespread, it is becoming increasingly important to develop catalyst materials that improve oxygen storage capacity (OSC) characteristics at low temperatures while maintaining industry-standard high-temperature performance and emission control, thereby addressing increased on / off cycles and improved cold-start hydrocarbon conversion.

[0005] Therefore, there is still a need to develop compositions with high oxygen storage capacity and simple and efficient methods for preparing such high oxygen storage capacity compositions with higher thermal stability. [Overview of the project]

[0006] This specification discloses a composition comprising zirconium oxide, cerium oxide, and optionally one or more rare earth oxides other than cerium, which exhibits an oxygen storage capacity of about 40 μmol-O2 / g to about 300 μmol-O2 / g after calcination (i.e., heat treatment) at a temperature of about 900°C in air for about 5 hours. In one embodiment, the optionally selected rare earth oxide can be selected from the group consisting of La2O3, Y2O3, Nd2O3, Pr2O3, and mixtures thereof.

[0007] In some embodiments, the composition essentially consists of zirconium oxide, cerium oxide, and one or more of yttrium oxide, lanthanum oxide, neodymium oxide, and praseodymium oxide, and after calcination (i.e., heat treatment) at a temperature of about 900°C in air for about 5 hours, the composition exhibits an oxygen storage capacity of about 40 μmol-O2 / g to about 300 μmol-O2 / g.

[0008] Furthermore, this specification discloses a method for producing an oxide composition having a high oxygen storage capacity, comprising: (a) mixing an aqueous solution of oxalic acid with a zirconium salt solution, a cerium salt solution, and optionally a rare earth salt solution other than cerium to obtain a precursor solution; (b) adding an oxidizing agent to the precursor solution; (c) adding ammonium hydroxide to form a precipitate and autoclaving the precipitate; (d) dispersing the precipitate in glycol ether; and (e) calcining (i.e., heat treating) the precipitate to obtain an oxide composition containing zirconium oxide, cerium oxide, and optionally one or more rare earth oxides other than cerium, and having a high oxygen storage capacity. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows a flowchart of the prior art, as illustrated in Comparative Example 1.

[0010] [Figure 2] This figure shows a flowchart of one embodiment of a method for producing cerium and zirconium-containing oxides with improved oxygen storage capacity, as disclosed herein. [Modes for carrying out the invention]

[0011] This disclosure relates to mixed oxide compositions containing zirconium and cerium that generally exhibit remarkably improved / high oxygen storage capacity (OSC) both during preparation (i.e., fresh) and after aging at high temperatures.

[0012] Before a composition comprising zirconium oxide and cerium oxide and having a high oxygen storage capacity, and a method for producing the same, is disclosed and described, it should be understood that this disclosure is not limited to the specific structures, methods, processes, or materials disclosed herein, but extends to their equivalents as recognized by those skilled in the art. It should also be understood that the terms used herein are used solely for the purpose of describing specific embodiments and are not intended to limit them. Note that, where used herein, the singular forms "a," "an," and "the" refer to multiple subjects unless otherwise explicitly indicated by the context. Thus, for example, a reference to "process" may include multiple processes, a reference to "product" or "product" of a reaction or process should not be interpreted as all of the products of the reaction / process, and a reference to "process" may include one or more such processing steps. Thus, a processing step may include multiple or repeated processing of similar materials / flows to produce a specified processing product.

[0013] Numerical values ​​with "approximately" include typical experimental variance. As used herein, the term "approximately" means within a statistically significant range of a given value, such as particle size, concentration range, time frame, molecular weight, temperature, or pH. Such a range may be within one order of magnitude of the indicated value or range, typically within 10%, and more typically within 5%. Sometimes, such a range may be within the typical experimental error of the standard method used to measure and / or determine a given value or range. The acceptable variation encompassed by the term "approximately" depends on the particular system under study and will be readily apparent to those skilled in the art. Whenever a range is enumerated in this application, all integers within that range are contemplated as embodiments of the invention.

[0014] This application relates to compositions containing zirconium oxide and cerium oxide and having improved oxygen storage capacity (OSC). These compositions may also contain one or more rare earth oxides other than cerium. With respect to improved oxygen storage capacity, the compositions disclosed herein have an oxygen storage capacity of about 40 μmol-O2 / g to about 300 μmol-O2 / g after calcination (i.e., heat treatment) at a temperature of about 900°C in air for about 5 hours.

[0015] The compositions disclosed herein comprise zirconium oxide, cerium oxide, and optionally one or more rare earth oxides other than cerium, and exhibit an oxygen storage capacity of approximately 40 μmol-O2 / g to approximately 300 μmol-O2 / g after calcination (i.e., heat treatment) at a temperature of approximately 900°C in air for approximately 5 hours.

[0016] In one embodiment, the compositions disclosed herein have an oxygen storage capacity (OSC) of about 42 μmol-O2 / g to about 250 μmol-O2 / g after calcination (i.e., heat treatment) in air at a temperature of about 900°C for about 5 hours, and in another embodiment, the compositions disclosed herein have an oxygen storage capacity of about 42 μmol-O2 / g to about 125 μmol-O2 / g after calcination (i.e., heat treatment) in air at a temperature of about 900°C for about 5 hours. In one embodiment, the compositions disclosed herein have an oxygen storage capacity of about 42 μmol-O2 / g to about 80 μmol-O2 / g after calcination (i.e., heat treatment) in air at a temperature of about 900°C for about 5 hours. It should be noted that these calcination / heat treatment temperatures for OSC are those used in the calcination / heat treatments used in the methods for preparing the compositions disclosed herein. Therefore, these OSC properties are those of the prepared compositions or the "fresh" compositions.

[0017] Oxygen storage capacity is measured using a Micrometrics Autochem 2920 system. The sample is subjected to pretreatment. During pretreatment, 50 cm³ is used. 3The temperature is first raised to 400°C under a flow of He gas per minute, then the sample is subjected to 10 pulses of 10% O2 / He, followed by another 20 pulses of 10% CO / He while maintaining the temperature at 400°C. The sample is then subjected to pulses of 10% O2 / He until saturation is reached, and the oxygen storage capacity is measured by the cumulative amount of O2 absorbed at 400°C.

[0018] In some embodiments, the compositions disclosed herein may undergo further calcination (i.e., aging). In these embodiments, after further calcination or aging, the compositions exhibit an OSC of about 21 μmol-O2 / g to about 250 μmol-O2 / g after further calcination (i.e., aging) at a temperature of about 1000°C in air for about 10 hours. In some embodiments, after further calcination or aging, the compositions exhibit an OSC of about 25 μmol-O2 / g to about 100 μmol-O2 / g after further calcination (i.e., aging) at a temperature of about 1000°C in air for about 10 hours. In further embodiments, after further calcination or aging, the compositions exhibit an OSC of about 25 μmol-O2 / g to about 70 μmol-O2 / g after further calcination (aging) at a temperature of about 1000°C in air for about 10 hours.

[0019] In additional embodiments, when further calcined or aged, the composition exhibits an OSC of approximately 10 μmol-O2 / g to approximately 200 μmol-O2 / g after further calcination (aging) at a temperature of approximately 1100°C in air for approximately 10 hours. In some embodiments, when further calcined or aged, the composition exhibits an OSC of approximately 10 μmol-O2 / g to approximately 100 μmol-O2 / g after further calcination (aging) at a temperature of approximately 1100°C in air for approximately 10 hours. In further embodiments, when further calcined or aged, the composition exhibits an OSC of approximately 12.5 μmol-O2 / g to approximately 50 μmol-O2 / g after further calcination (aging) at a temperature of approximately 1100°C in air for approximately 10 hours.

[0020] In another embodiment, when further calcined or aged, the composition exhibits an OSC of approximately 6 μmol-O2 / g to approximately 150 μmol-O2 / g after further calcination (aging) at a temperature of approximately 1150°C in air for approximately 5 hours. In one embodiment, when further calcined or aged, the composition exhibits an OSC of approximately 6 μmol-O2 / g to approximately 80 μmol-O2 / g after further calcination (aging) at a temperature of approximately 1150°C in air for approximately 10 hours. In yet another embodiment, when further calcined or aged, the composition exhibits an OSC of approximately 6 μmol-O2 / g to approximately 40 μmol-O2 / g after further calcination (aging) at a temperature of approximately 1150°C in air for approximately 10 hours.

[0021] These further firing processes (i.e., aging processes) are performed individually or in any combination cumulatively, in conjunction with an initial firing at approximately 900°C in air for approximately 5 hours. The initial firing is part of the method for preparing the composition, while the further firing processes (i.e., aging processes) are for testing the OSC capacity of the composition in a manner that simulates use.

[0022] For example, a single sample may be calcined in air at approximately 900°C for approximately 5 hours (as part of the initial preparation method), and then calcined in air at approximately 1000°C for approximately 10 hours. Alternatively, a single sample may be calcined in air at approximately 900°C for approximately 5 hours, and then calcined in air at approximately 1100°C for approximately 10 hours. Alternatively, a single sample may be calcined in air at approximately 900°C for approximately 5 hours, and then calcined in air at approximately 1150°C for approximately 10 hours. Alternatively, a single sample may be calcined in air at approximately 900°C for approximately 5 hours, and then calcined in air at approximately 1000°C for approximately 10 hours, and then calcined in air at approximately 1100°C for approximately 10 hours. Alternatively, a single sample may be calcined in air at approximately 900°C for approximately 5 hours, then calcined in air at approximately 1000°C for approximately 10 hours, then calcined in air at approximately 1100°C for approximately 10 hours, and finally calcined in air at approximately 1150°C for approximately 10 hours.

[0023] In addition to zirconium oxide and cerium oxide, the compositions disclosed herein may optionally contain one or more rare earth oxides other than cerium. These additional and optional rare earth oxides include oxides of any of the rare earth elements other than cerium. The additional rare earth oxides can be selected from the group consisting of yttrium (Y), lanthanum (La), neodymium (Nd), praseodymium (Pr), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and mixtures thereof.

[0024] In certain embodiments, the additional one or more rare earth oxides are yttrium oxide, lanthanum oxide, neodymium oxide, praseodymium oxide, or mixtures thereof. Thus, the composition includes zirconium oxide, cerium oxide, and an additional rare earth oxide selected from the group consisting of yttrium oxide, lanthanum oxide, neodymium oxide, praseodymium oxide, and mixtures thereof.

[0025] In one embodiment, the composition may contain zirconium oxide, cerium oxide, lanthanum oxide, and neodymium oxide. In other embodiments, the composition may contain zirconium oxide, cerium oxide, lanthanum oxide, and yttrium oxide. In additional embodiments, the composition may contain zirconium oxide, cerium oxide, lanthanum oxide, neodymium oxide, and yttrium oxide. In further embodiments, the composition may contain zirconium oxide, cerium oxide, lanthanum oxide, and praseodymium oxide.

[0026] The composition can contain about 15 wt% to about 60 wt% cerium oxide, about 40 wt% to about 85 wt% zirconium oxide, and optionally, one or more rare earth oxides other than cerium, based on the total weight of the composition. In certain embodiments, the composition includes one or more of the rare earth oxides yttrium oxide, lanthanum oxide, neodymium oxide, praseodymium oxide, or mixtures thereof. In these embodiments, the one or more additional rare earth oxides may be present in an amount of about 2 wt% to about 15 wt% based on the total weight. In certain embodiments, the one or more additional rare earth oxides may be present in an amount of about 5 wt% to about 12 wt% based on the total weight. In certain specific embodiments, the one or more additional rare earth oxides may be present in an amount of about 7 wt% to about 10 wt% based on the total weight.

[0027] These oxide compositions disclosed herein may contain trace amounts of impurities. These impurities are typically present in an amount of about 1 wt% or less (from about 0 or an undetectable amount) based on the total weight of the mixed oxide composition. These impurities include residual solvents, salts, other metals, and the like. These other metals include those commonly found in water, such as magnesium, iron, calcium, silicon, sodium, and the like. These impurity amounts (from about 1 wt% to about zero or an undetectable amount) can be present in any of the described embodiments of the mixed oxide composition. If present and detectable, any impurities can be present in an amount of about less than 100 ppm.

[0028] In one embodiment, the composition disclosed herein consists essentially of zirconium oxide, cerium oxide, and one or more of yttrium oxide, lanthanum oxide, neodymium oxide, and praseodymium oxide, and the composition exhibits an oxygen storage capacity of about 40 μmol-O2 / g to about 300 μmol-O2 / g after firing at a temperature of about 900 °C in air for about 5 hours.

[0029] In certain embodiments, the composition contains zirconium oxide, cerium oxide, lanthanum oxide, and neodymium oxide. In this embodiment, the composition may have a Ce / Zr / La / Nd ratio of about 71.2% by weight of ZrO2 to about 73.2% by weight of ZrO2, about 20.1% by weight of CeO2 to about 21.5% by weight of CeO2, about 1.2% by weight of La2O3 to about 2.2% by weight of La2O3, and about 4.8% by weight of Nd2O3 to about 5.8% by weight of Nd2O3, on an oxide basis.

[0030] In another embodiment, the composition contains zirconium oxide, cerium oxide, lanthanum oxide, and yttrium oxide. In this embodiment, the composition may have a Zr / Ce / La / Y ratio of about 66.5 wt% to about 68.5 wt% ZrO2, about 24 wt% to about 26 wt% CeO2, about 3 wt% La2O3 to about 4 wt% La2O3, and about 3.5 wt% Y2O3 to about 4.5 wt% Y2O3 on an oxide basis.

[0031] In yet another embodiment, the composition contains zirconium oxide, cerium oxide, lanthanum oxide, neodymium oxide, and yttrium oxide. In this embodiment, the composition may have a Zr / Ce / La / Nd / Y ratio of about 49 wt% to about 51 wt% ZrO2, about 39 wt% to about 41 wt% CeO2, about 3.5 wt% La2O3 to about 4.5 wt% La2O3, about 3.5 wt% Nd2O3 to about 4.5 wt% Nd2O3, and about 1.8 wt% Y2O3 to about 2.2 wt% Y2O3 on an oxide basis.

[0032] In another embodiment, the composition contains zirconium oxide, cerium oxide, lanthanum oxide, and praseodymium oxide. In this embodiment, the composition may have a Zr / Ce / La / Pr ratio of about 49 wt% to about 51 wt% ZrO2, about 39 wt% to about 41 wt% CeO2, about 4.75 wt% La2O3 to about 5.25 wt% La2O3, and about 4.75 wt% Pr2O3 to about 5.25 wt% Pr2O3 on an oxide basis.

[0033] The compositions of the present disclosure may further comprise zirconium oxide, cerium oxide, and one or more oxides of lanthanum, neodymium, praseodymium, and yttrium in various proportions.

[0034] The improved oxygen storage capacity makes these compositions particularly suitable for use in catalytic action, either as part of a catalytic system or as a catalyst support. Catalysts are used in vehicles to purify exhaust gases and for other related applications. When used as a catalyst support or as part of a catalytic system, the catalytic composition further comprises platinum group metals (PGMs). Platinum group metals (PGMs) are selected from the group consisting of platinum, palladium, rhodium, iridium, osmium, ruthenium, and mixtures thereof.

[0035] The compositions having improved OSC disclosed herein are produced by a specific method that provides compositions having an oxygen storage capacity of about 40 μmol-O2 / g to about 300 μmol-O2 / g after calcination in air at a temperature of about 900°C for about 5 hours. Figure 2 is a flowchart of one embodiment of the method for preparing these compositions having improved OSC.

[0036] The method includes the steps of (a) mixing an aqueous solution of oxalic acid with a zirconium salt solution, a cerium salt solution, and optionally a rare earth salt solution other than cerium to obtain a precursor solution; (b) adding an oxidizing agent to the precursor solution; (c) adding ammonium hydroxide to form a precipitate and autoclaving the precipitate; (d) dispersing the precipitate in glycol ether; and (e) calcining or heat-treating the precipitate to obtain an oxide composition containing zirconium oxide, cerium oxide, and optionally one or more rare earth oxides other than cerium, and having a high oxygen storage capacity.

[0037] An aqueous solution of oxalic acid is mixed with a zirconium salt solution, a cerium salt solution, and optionally a rare earth salt solution to obtain a precursor solution. The zirconium salt, cerium salt, and optionally additional rare earth salts are water-soluble, and in this method, the salts are dissolved in water before being mixed with the aqueous oxalic acid solution. The salts may be inorganic or organic acids, such as water-soluble chlorides, sulfates, nitrates, or acetates. In some embodiments, a zirconyl oxychloride solution is used. In some embodiments, the rare earth salt may be either a chloride salt or a nitrate. As described herein, the additional rare earths may be Pr, La, Nd, Y, or mixtures thereof.

[0038] The oxalic acid aqueous solution is mixed in an amount of about 50 to about 100% by weight relative to the zirconium oxide content. The rare earth salt solution, which includes the cerium salt solution and an optional rare earth salt solution, may have a rare earth concentration of about 10 g / L to about 150 g / L, and in some embodiments may have a rare earth concentration of about 100 g / L. The precursor solution of step (a) may have an oxide concentration of about 50 g / L to about 100 g / L.

[0039] The order in which the oxalic acid solution, zirconium salt solution, cerium salt solution, and one or more rare earth salt solutions other than cerium are added to obtain the precursor solution in step (a) is not important; any order of addition may be used, or all may be added simultaneously. Furthermore, the rate of addition is not important. In one embodiment, an aqueous solution of oxalic acid can be prepared to form a mixture containing oxalic acid and zirconium salt solution. Then, the rare earth salt solution can be added to obtain the precursor solution.

[0040] The oxidizing agent is added to the precursor solution formed in step (a). The oxidizing agent may be a hypochlorite, sodium chlorate, ammonium perchlorate, ozone, hydrogen peroxide, or a mixture thereof. The oxidizing agent is added so that the molar ratio of oxidizing agent to rare earth ions is about 7 to about 12, in some embodiments about 8 to about 11. In other specific embodiments, the oxidizing agent is added so that the molar ratio of oxidizing agent to rare earth ions is about 10.

[0041] After adding the oxidizing agent, ammonium hydroxide can be added to form a precipitate, or a mixture containing the oxidizing agent can be added to the ammonium hydroxide solution. The ammonium hydroxide used may be about 5M to about 10M, and the amount of ammonium hydroxide may be added in an amount of about 700 to about 1250% by weight relative to the amount of oxide. NH4OH / M + The ratio is approximately 10.1, where M + This represents the total metal ions in the mixture.

[0042] Next, the precipitate is autoclaved. The precipitate may be autoclaved at a temperature of approximately 50°C to approximately 100°C for approximately 45 minutes to approximately 2 hours. In one embodiment, the precipitate may be autoclaved at a temperature of approximately 70°C to approximately 80°C for approximately 1 hour.

[0043] In one embodiment, the precipitate may be autoclaved and then washed with deionized water to remove any remaining bound or adsorbed ions, such as nitrates and chlorides. In one embodiment, the precipitate is particularly pure and free of anionic impurities, characterized by a conductivity of less than about 10 mS / cm after washing. The precipitate may be isolated by filtration, such as vacuum filtration.

[0044] The precipitate is dispersed in the glycol ether. The precipitate may be dispersed in an amount of glycol ether of about 150% to about 500% by weight relative to the oxide content. The glycol ether has an evaporation rate of less than 0.05, a boiling point above 230°C, a surface tension of less than 34 dynes / cm, and water solubility of more than 50% by weight at 25°C. In one embodiment, the glycol ether has an evaporation rate of about 0.0002 to about 0.005, a boiling point of about 230°C to about 300°C, a surface tension of about 25 to about 34 dynes / cm, and water solubility of about 50% to about 100% by weight at about 25°C.

[0045] The precipitate is calcined or heat-treated. Calcination may be carried out at a temperature of about 750°C to about 1100°C for about 3 to 7 hours. In certain embodiments, calcination may be carried out at a temperature of about 900°C for about 5 hours. Calcination after the above method step yields the oxide composition described herein having improved OSC.

[0046] The oxide compositions produced by the methods disclosed herein have an OSC of approximately 40 μmol-O2 / g to approximately 300 μmol-O2 / g after calcination in air at a temperature of approximately 900°C for approximately 5 hours. This OSC is for the (fresh) composition at the time of preparation.

[0047] The addition of the oxidizing agent and the dispersion of the solid in the glycol ether in step (b) characterize the method of the present invention and assist in the production of the compositions disclosed herein having improved oxygen storage capacity.

[0048] The following examples are provided to illustrate in more detail the methods of the present invention for preparing and characterizing compositions having improved oxygen storage capacity, but the scope of the present invention is not limited in any way thereby.

[0049] In the examples disclosed herein, compositions were prepared and tested for all OSCs. Characterization was performed using a Micrometrics Autochem 2920 system. Here, 0.1 g of the samples obtained in the examples and comparative examples were weighed into quartz sample tubes equipped with a packed quartz wool bed. The samples were then subjected to pretreatment. In the pretreatment, 50 cm 3 The temperature was first raised to 400°C under a flow of He gas per minute, then the sample was subjected to 10 pulses of 10% O2 / He, followed by another 20 pulses of 10% CO / He while maintaining the temperature at 400°C. Subsequently, the sample was subjected to pulses of 10% O2 / He until saturation was reached, and the oxygen storage capacity was measured by the cumulative amount of O2 absorbed at 400°C.

[0050] Comparative Example 1: Oxide composition with Zr / Ce / La / Nd = 72.2 / 20.8 / 1.7 / 5.3 The following was done: 1) A mixed oxide was prepared having an oxide composition corresponding to 72.2 wt% ZrO2, 20.8 wt% CeO2, 1.7 wt% La2O3, and 5.3 wt% Nd2O3. 2) An aqueous solution of oxalic acid was mixed with a zirconyl oxychloride solution. 3) Solutions of cerium(III) nitrate, lanthanum nitrate, and neodymium nitrate were combined with the above mixture in appropriate ratios to achieve the target elemental composition of zirconium, cerium, lanthanum, and neodymium. 4) A precipitate was formed using 273 mL of NH4OH (5.5 M). 5) The precipitate was autoclaved for 1 hour. 6) The aged precipitate was washed with deionized water to remove impurities. 7) The washed precipitate was filtered. 8) The filtered solid was calcined in air at 900°C for 5 hours. The conventional method described above is shown in Figure 1.

[0051] Example 1: Oxide composition of Zr / Ce / La / Nd = 72.2 / 20.8 / 1.7 / 5.3 The following was done: 1) A mixed oxide composition was prepared containing oxides equivalent to 72.2% by weight of ZrO2, 20.8% by weight of CeO2, 1.7% by weight of La2O3, and 5.3% by weight of Nd2O3. 2) An aqueous solution of oxalic acid was mixed with a zirconyl oxychloride solution. 3) Solutions of cerium(III) nitrate, lanthanum nitrate, and neodymium nitrate were combined with the above mixture in appropriate ratios to achieve the target elemental composition of zirconium, cerium, lanthanum, and neodymium. 4) 25 mL of H2O2 solution (30% by weight) was added to the above mixture. 5) A precipitate was formed using 273 mL of NH4OH (5.5 M). 6) The precipitate was autoclaved for 1 hour. 7) The aged precipitate was washed with deionized water to remove impurities. 8) The washed precipitate was filtered. 9) The filtered solid was dispersed in triethylene glycol ethyl ether. 10) The dispersed paste was baked in air at 900°C for 5 hours.

[0052] Example 2: Oxide composition of Zr / Ce / La / Y = 67.5 / 25 / 3.5 / 4 The following was done: 1) A mixed oxide composition was prepared containing oxides equivalent to 67.5% by weight of ZrO2, 25% by weight of CeO2, 3.5% by weight of La2O3, and 4% by weight of Y2O3. 2) An aqueous solution of oxalic acid was mixed with a zirconyl oxychloride solution. 3) Solutions of cerium(III) nitrate, lanthanum nitrate, and yttrium nitrate were combined with the above mixture in appropriate ratios to achieve the target elemental composition of zirconium, cerium, lanthanum, and yttrium. 4) 19 mL of H2O2 solution (35% by weight) was added to the above mixture. 5) A precipitate was formed using 205 mL of NH4OH (5.5 M). 6) The precipitate was autoclaved for 1 hour. 7) The aged precipitate was washed with deionized water to remove impurities. 8) The washed precipitate was filtered. 9) The filtered solid was dispersed in tripropylene glycol methyl ether. 10) The dispersed paste was baked in air at 900°C for 5 hours.

[0053] Example 3: Oxide composition of Zr / Ce / La / Nd / Y = 50 / 40 / 4 / 4 / 2 The following was done: 1) A mixed oxide composition was prepared containing oxides equivalent to 50 wt% ZrO2, 40 wt% CeO2, 4 wt% La2O3, 4 wt% Nd2O3, and 2 wt% Y2O3. 2) An aqueous solution of oxalic acid was mixed with a zirconyl oxychloride solution. 3) Solutions of cerium(III) nitrate, lanthanum nitrate, neodymium nitrate, and yttrium nitrate were combined with the above mixture in appropriate ratios to achieve the target elemental composition of zirconium, cerium, lanthanum, neodymium, and yttrium. 4) 71 mL of H2O2 solution (30% by weight) was added to the above mixture. 5) A precipitate was formed using 386 mL of NH4OH (5.5 M). 6) The precipitate was autoclaved for 1 hour. 7) The aged precipitate was washed with deionized water to remove impurities. 8) The washed precipitate was filtered. 9) The filtered solid was dispersed in triethylene glycol n-butyl ether. 10) The dispersed paste was baked in air at 900°C for 5 hours.

[0054] Example 4: Oxide composition of Zr / Ce / La / Pr = 50 / 40 / 5 / 5 The following was done: 1) A mixed oxide composition was prepared containing oxides equivalent to 50 wt% ZrO2, 40 wt% CeO2, 5 wt% La2O3, and 5 wt% Pr2O3. 2) An aqueous solution of oxalic acid was mixed with a zirconyl oxychloride solution. 3) Solutions of cerium(III) nitrate, lanthanum nitrate, and praseodymium nitrate were combined with the above mixture in appropriate ratios to achieve the target elemental composition of zirconium, cerium, lanthanum, and praseodymium. 4) 47 mL of H2O2 solution (30% by weight) was added to the above mixture. 5) A precipitate was formed using 255 mL of NH4OH (5.5 M). 6) The precipitate was autoclaved for 1 hour. 7) The aged precipitate was washed with deionized water to remove impurities. 8) The washed precipitate was filtered. 9) The filtered solid was dispersed in diethylene glycol hexyl ether. 10) The dispersed paste was baked in air at 900°C for 5 hours.

[0055] Summary of results regarding oxygen storage capacity at 400°C The following table summarizes the oxygen storage capacity results at 400°C for Examples 1-4 versus Comparative Example 1. The results confirm that the oxygen storage capacity of the examples disclosed herein is significantly higher than that of the comparative example prepared by the methods disclosed in the prior art. [Table 1]

[0056] As shown herein, compositions comprising zirconium oxide, cerium oxide, and optionally one or more rare earth oxides other than cerium exhibit an oxygen storage capacity of approximately 42.5 μmol-O2 / g or higher after calcination in air at a temperature of approximately 900°C for approximately 5 hours. These high oxygen storage capacities are in contrast to those of comparative oxides. The higher oxygen storage capacities of the compositions disclosed herein are maintained even after further air aging / calcination at 1000°C for 10 hours, 1100°C for 10 hours, and 1150°C for 10 hours. This higher oxygen storage capacity provides the compositions with improved catalytic materials for catalytic converters for gas purification and for vehicles.

[0057] Unless otherwise specified, all figures used in this specification and the claims, such as quantities, molecular weights, and other properties of the components, as well as reaction conditions, should be understood to be modified in all cases by the term "approximately." Therefore, unless otherwise indicated, the numerical parameters described in the following specification and the attached claims are approximations that may vary depending on the desired properties to be obtained.

[0058] Although the numerical ranges and parameters representing a wide range of techniques are approximations, the numbers shown in specific examples are reported as accurately as possible. However, any given number inherently contains a certain error that inevitably arises from the standard deviation observed in each test measurement.

[0059] It will be apparent that the compositions and methods described herein are well adapted to achieve the purposes and benefits mentioned, as well as those inherent to them. Those skilled in the art will recognize that the methods and systems herein can be carried out in many ways and are therefore not limited to the exemplary embodiments and examples described herein. In this regard, any number of features from the different embodiments described herein can be combined into a single embodiment, and fewer or more alternative embodiments than all of the features described herein are possible.

[0060] While various embodiments have been described for the purposes of this disclosure, various changes and modifications can be made within the scope that is readily conceivable by this disclosure. Numerous other changes that are encompassed in the spirit of this disclosure will be readily conceivable to those skilled in the art.

Claims

1. A composition comprising zirconium oxide, cerium oxide, and optionally one or more rare earth oxides other than cerium, wherein after firing at a temperature of approximately 900°C in air for approximately 5 hours, approximately 40 μmol-O ２ / g ~ about 300 μmol-O ２ A composition exhibiting an oxygen storage capacity of / g.

2. A composition essentially consisting of zirconium oxide, cerium oxide, and one or more of yttrium oxide, lanthanum oxide, neodymium oxide, and praseodymium oxide, wherein after firing at a temperature of about 900°C in air for about 5 hours, about 40 μmol-O ２ / g ~ about 300 μmol-O ２ A composition exhibiting an oxygen storage capacity of / g.

3. CeO ２ and ZrO ２ and La ２ O ３、 Y ２ O ３ Nd ２ O ３ and Pr ２ O ３ The composition according to claim 1, comprising one or more of the above.

4. The oxygen storage capacity of the oxide is approximately 21 μmol-O after further calcination at a temperature of approximately 1000°C in air for approximately 10 hours. ２ / g ~ about 250 μmol-O ２ The composition according to any one of claims 1 to 3, wherein the amount is / g.

5. The oxygen storage capacity is approximately 10 μmol-O after further firing at a temperature of approximately 1100°C in air for approximately 10 hours. ２ / g ~ about 200 μmol-O ２ The composition according to any one of claims 1 to 3, wherein the amount is / g.

6. The oxygen storage capacity is approximately 6 μmol-O after further firing at a temperature of approximately 1150°C in air for approximately 5 hours. ２ / g ~ about 150 μmol-O ２ The composition according to any one of claims 1 to 3, wherein the amount is / g.

7. CEO ２ La ２ O ３ , Nd ２ O ３、 and ZrO ２ Essentially, it consists of Ce / Zr / La / Nd, with a ratio of approximately 71.2% by weight of ZrO on an oxide basis. ２ ~Approximately 73.2% by weight of ZrO ２ Approximately 20.1% by weight of CeO ２ ~Approximately 21.5% by weight of CeO ２ , approximately 1.2% by weight of La ２ O ３ ~Approximately 2.2% by weight of La ２ O ３ , and approximately 4.8% by weight of Nd ２ O ３ ~Approximately 5.8% by weight of Nd ２ O ３ The composition according to any one of claims 1 to 6.

8. CEO ２ La ２ O ３ , Y ２ O ３ , and ZrO ２ Essentially, it consists of Zr / Ce / La / Y, with a Zr / Ce / La / Y ratio of approximately 66.5% by weight on an oxide basis. ２ ~Approximately 68.5% by weight of ZrO ２ Approximately 24% by weight of CeO ２ ~Approximately 26% by weight of CeO ２ Approximately 3% by weight of La ２ O ３ ~Approximately 4% by weight of La ２ O ３ and approximately 3.5% by weight of Y ２ O ３ ~Approximately 4.5% by weight of Y ２ O ３ The composition according to any one of claims 1 to 6.

9. CEO ２ La ２ O ３ , Y ２ O ３ , Nd ２ O ３ , and ZrO ２ Essentially, the ratio of Zr / Ce / La / Nd / Y is approximately 49% by weight of ZrO on an oxide basis. ２ ~Approximately 51% by weight of ZrO ２ Approximately 39% by weight of CeO ２ ~Approximately 41% by weight of CeO ２ Approximately 3.5% by weight of La ２ O ３ ~Approximately 4.5% by weight of La ２ O ３ , approximately 3.5% by weight of Nd ２ O ３ ~Approximately 4.5% by weight of Nd ２ O ３ and approximately 1.8% by weight of Y ２ O ３ ~Approximately 2.2% by weight of Y ２ O ３ The composition according to any one of claims 1 to 6.

10. CeO ２ 、 La ２ O ３ 、 Pr ２ O ３ 、 and ZrO ２ and consists essentially of, with the ratio of Zr / Ce / La / Pr, on an oxide-equivalent basis, from about 49 wt% ZrO ２ to about 51 wt% ZrO ２ 、 about 39 wt% CeO ２ to about 41 wt% CeO ２ 、 about 4.75 wt% La[[ID=2​​​​​​​​​​​​​​​

11. A method for producing an oxide with a high oxygen storage capacity, (a) A precursor solution is obtained by mixing an aqueous solution of oxalic acid with a zirconium salt solution, a cerium salt solution, and optionally a rare earth salt solution other than cerium. (b) Adding an oxidizing agent to the precursor solution, (c) Add ammonium hydroxide to form a precipitate, and autoclave the precipitate, (d) Dispersing the precipitate in a glycol ether, (e) A method comprising calcining the precipitate to obtain an oxide composition having a high oxygen storage capacity, comprising zirconium oxide, cerium oxide, and optionally one or more rare earth oxides other than cerium.

12. After the oxide composition is calcined in air at a temperature of approximately 900°C for approximately 5 hours, approximately 40 μmol-O ２ / g ~ about 300 μmol-O ２ The method according to claim 11, having an oxygen storage capacity of / g.

13. The method according to claim 11 or 12, wherein the glycol ether has an evaporation rate of about 0.0002 to about 0.005, a boiling point of about 230°C to about 300°C, a surface tension of about 25 to about 34 dynes / cm, and water solubility of about 50% to about 100% by weight at about 25°C.

14. The method according to any one of claims 11 to 13, wherein the glycol ether is added in an amount of about 150 to about 500% by weight relative to the amount of oxide.

15. The method according to any one of claims 11 to 14, wherein the oxidizing agent is selected from the group consisting of hypochlorite, sodium chlorate, ammonium perchlorate, ozone, hydrogen peroxide, and mixtures thereof.

16. The method according to claim 15, wherein the oxidizing agent is added such that the molar ratio of the oxidizing agent to the rare earth ions is about 7 to about 12.

17. The method according to claim 16, wherein the oxidizing agent is added such that the molar ratio of the oxidizing agent to the rare earth ions is approximately 10.

18. The method according to any one of claims 11 to 16, wherein in step (a), an aqueous solution of oxalic acid, a zirconyl oxychloride solution, a cerium nitrate solution, and a rare earth nitrate solution selected from the group consisting of yttrium, lanthanum, praseodymium, neodymium, and mixtures thereof are mixed.

19. The method according to any one of claims 11 to 18, further comprising washing the precipitate with deionized water before dispersing the precipitate in glycol ether.

20. The method according to any one of claims 11 to 19, wherein oxalic acid is mixed in an amount of about 50 to about 100% by weight relative to the amount of zirconium oxide.

21. The method according to any one of claims 11 to 20, wherein the ammonium hydroxide is about 5 M to about 10 M, and the ammonium hydroxide is added in an amount of about 700% to about 1250% by weight relative to the amount of oxide.

22. The method according to any one of claims 11 to 21, wherein the firing is carried out at a temperature of about 750°C to about 1100°C for about 3 to 7 hours.

23. The method according to claim 22, wherein the firing is carried out at a temperature of approximately 900°C for approximately 5 hours.

24. The method according to any one of claims 11 to 23, wherein the autoclave treatment is performed at a temperature of about 50°C to about 100°C for about 45 minutes to about 2 hours.

25. The method according to any one of claims 11 to 24, wherein the precursor solution in step (a) has an oxide concentration of about 50 g / L to about 100 g / L.

26. An oxide composition produced by the method of any one of claims 11 to 25, wherein after calcination at a temperature of about 900°C in air for about 5 hours, about 40 μmol-O ２ / g ~ about 300 μmol-O ２ An oxide composition having an oxygen storage capacity of / g.

27. A catalyst composition comprising the composition according to any one of claims 1 to 10 or 26.

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