Patent Application
20250235853
This disclosure relates to mixed oxide compositions containing oxides of cerium, zirconium, and a mixture of iron and strontium. These compositions optionally also may contain additional rare earth dopants. These mixed oxide compositions surprisingly exhibit enhanced low temperature oxygen storage capacity (OSC), even after aging at elevated temperatures.
Catalytic materials including ceria zirconia mixed oxides have utility in a number of fields, including abatement of nitrogen oxides, primarily NO and NO2 (referred to as NOx), carbon monoxide (CO), hydrocarbons (HC), such as methane (CH4) and non-methane hydrocarbons (NMHC), other pollutants from gasoline, compressed natural gas (CNG), and diesel fueled internal combustion engines, such as on-road vehicles, cars, buses and trucks and other off-road gasoline, CNG and diesel engines used in utility vehicles, recreational vehicles and stationary source power generation applications. Emission standards for unburned hydrocarbons, carbon monoxide, and nitrogen oxide contaminants have been set by various worldwide government agencies and must be met or severe penalties will be imposed. To meet such standards, catalytic converters typically are placed in the exhaust gas line of these emission sources. Exhaust gas flows through a catalytic converter and harmful HC and CO are converted into CO2 and H2O. NOx is preferentially converted into N2 and O2 with any unconverted CO, HC, and NOx emitted from the exhaust pipe and into the atmosphere as primary pollutants. Catalytic converters contain mixtures of base metal oxides and Platinum Group Metals (PGM).
A three-way conversion (TWC) catalyst includes one or more of these precious metals/platinum group metals (PGM) combined with high surface area base metal oxide/mixed oxide carrier materials. The oxide carrier materials can contain aluminum, titanium, silicon, zirconium, cerium, and mixtures thereof. An oxide carrier material's ability to store and release oxygen helps to regulate catalysis.
There continues to be a need for effective mixed oxide supports for these platinum group metal catalysts to convert emissions more efficiently to less harmful gases. Further, these mixed oxide carrier materials to date primarily have focused on development of materials suitable for catalytic converters operating at high temperatures, which are typical of internal combustion engines. As hybrid internal combustion/electric vehicles become more abundant, it is increasingly important to develop catalytic materials with improved oxygen storage capacity (OSC) characteristics at low temperatures to handle increased on/off cycling and improved conversion of cold start hydrocarbons while maintaining industry standard high temperature stability, performance, and emissions control.
Disclosed herein are compositions comprising ceria zirconia with mixed oxides. The compositions may be used as catalytic carriers which may be used in gas exhaust purification catalysts. In particular, the ceria zirconia compositions comprise strontium oxide SrO and iron(III) oxide Fe2O3.
Also disclosed herein are washcoat suspension composition for use as a component of a catalytic coating and preparation of these washcoat compositions. The washcoats are applied as a catalyst coating to a substrate. These substrates can be of cordierite, fecralloy metal foil, or foamed ceramic materials.
Disclosed herein is a mixed oxide composition comprising: a) about 1 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 98 wt. % zirconium on an oxide basis; c) about 0.050 wt. % to about 0.50 wt. % iron on an oxide basis; d) about 0.015 wt. % to about 0.20 wt. % strontium on an oxide basis; and e) optionally an additional rare earth dopant selected from the group consisting of lanthanum, neodymium, yttrium, praseodymium, samarium, gadolinium, and mixtures thereof, and wherein when present each optional additional rare earth dopant is present in an amount of about 0.5 to about 15 wt. % on an oxide basis. In certain embodiments, the additional rare earth dopant selected from the group consisting of lanthanum, yttrium, and mixtures thereof present in an amount of about 5 to about 15 wt. % on an oxide basis. In certain embodiments, the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition.
Even though the amounts of iron and strontium are small, these small amounts impart surprisingly improved properties to the disclosed mixed oxide compositions. The mixture of iron and strontium surprisingly provides the mixed oxide composition with improved OSC even after aging at elevated temperatures, and in particular improved OSC at lower temperatures. The mixed oxide composition exhibits no detectable perovskite or pyrochlore phases as determined by XRD even after aging at 1100° C. for 10 hours in air, and the small amounts of iron and strontium can be varied accordingly.
In one embodiment, the mixed oxide composition comprises a) about 30 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 65 wt. % zirconium on an oxide basis; c) about 0.05 wt. % to about 0.50 wt. % iron on an oxide basis; d) about 0.015 wt. % to about 0.20 wt. % strontium on an oxide basis; and e) additional rare earth dopant selected from the group consisting of lanthanum, yttrium, and mixtures thereof present in an amount of about 5 to about 15 wt. % on an oxide basis.
Also disclosed is a catalyst or catalyst composition comprising the mixed oxide composition as an initial feed material.
Further disclosed is a suspension comprising: (i) a Platinum Group Metal (PGM) selected from group consisting of platinum, palladium, rhodium, iridium, osmium, ruthenium, and mixtures thereof and (ii) a mixed oxide composition comprising: a) about 1 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 98 wt. % zirconium on an oxide basis; c) about 0.05 wt. % to about 0.50 wt. % iron on an oxide basis; d) about 0.015 wt. % to about 0.20 wt. % strontium on an oxide basis; and e) optionally an additional rare earth dopant selected from the group consisting of, lanthanum, neodymium, yttrium, praseodymium, samarium, gadolinium, and mixtures thereof, and when present each optional additional rare earth dopant is present in an amount of about 0.5 to about 15 wt. % on an oxide basis.
In certain embodiments, the suspension contains rhodium or palladium as the Platinum Group Metal (PGM). In further specific embodiments, the suspension comprises about 55 wt. % to about 65 wt % of the mixed oxide composition.
When the suspension as disclosed herein is dried and calcined, the dried and calcined suspension exhibits an improved Oxygen Storage Capacity (OSC), and in particular improved OSC at lower temperatures.
This disclosure generally relates to mixed oxide compositions containing cerium, zirconium, iron, strontium, and optionally additional rare earth dopant. This disclosure also relates to a suspension comprising platinum group metals (PGM) and the mixed oxide compositions described herein, as well as supported catalysts prepared from the described mixed oxides. The described mixed oxides are useful for treating exhaust gases from internal combustion engines and exhibit surprisingly enhanced low temperature oxygen storage capacity (OSC), even after aging at elevated temperatures.
Before the compositions, catalysts, and methods are disclosed and described in detail, it is to be understood that this disclosure is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in this specification, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “an additional rare earth dopant” is not to be taken as quantitatively or source limiting, reference to “a step” may include multiple steps, reference to “producing” or “products” of a reaction or treatment should not be taken to be all of the products of a reaction/treatment, and reference to “treating” may include reference to one or more of such treatment steps.
Numerical values with “about” or “approximately” include typical experimental variances. As used herein, the terms “about” and “approximately” are used interchangeably and mean within a statistically meaningful range of a value, such as a stated weight percentage, surface area, concentration range, time frame, temperature, pH, and the like. Such a range can be within 10%, and even more typically within 5% of the indicated value or range. Sometimes, such a range can be within the experimental error typical of standard methods used for the measurement and/or determination of a given value or range. The allowable variation encompassed by the term “about” will depend upon the particular system under study, and can be readily appreciated by one of ordinary skill in the art. Whenever a range is recited within this application, at least every whole number integer within the range is also contemplated as an embodiment of the invention.
The present disclosure relates to mixed oxide compositions having improved oxygen storage capacity (OSC), even after aging at elevated temperatures. These mixed oxide compositions are mixed oxides of cerium, zirconium, iron, and strontium. The mixed oxide compositions are in powder form. Within the mixed oxide composition, the individual components are intimately mixed.
As disclosed herein, these mixed oxide compositions importantly contain iron and strontium (as oxides) and this mixture of iron and strontium surprisingly provides the mixed oxide composition with improved OSC even after aging at elevated temperatures, in particular improved OSC at lower temperatures.
In certain embodiments, the mixed oxide compositions also contain an amount of additional rare earth dopant. This additional rare earth dopant can be selected from any of the rare earths or mixtures thereof. In certain embodiments, the additional rare earth dopant is selected from the group consisting of lanthanum, neodymium, yttrium, praseodymium, samarium, gadolinium, and mixtures thereof. In particular embodiments, the additional rare earth dopant is lanthanum, yttrium, or mixtures thereof.
The mixed oxide composition is described as a mixture of oxides of cerium, zirconium, iron, strontium, and optionally one or more additional rare earth dopants, and the amounts of these individual components are measured (and reported) as oxides. However, it is not excluded that any of these components may be present at least partly in the form of hydroxides, oxyhydroxides, carbonates, and/or oxycarbonates. The compositional proportions of these components are determined by a plasma torch analytical technique using optical emission spectroscopy, as described in greater detailed within the Examples section. This technique measures and reports the components by weight percent on an equivalent oxide basis with respect to the total weight of the mixed oxide composition. This technique provides accurate elemental analysis of the small, but important, amounts of iron and strontium present in the disclosed mixed oxide compositions as described herein.
These mixed oxide compositions as disclosed herein comprise about 1 to about 45 wt. % cerium on an oxide basis; about 40 to about 98 wt. % zirconium on an oxide basis; about 0.065 wt. % to about 0.75 wt. % iron on an oxide basis; about 0.015 wt. % to about 0.25 wt. % strontium on an oxide basis; and optionally an additional rare earth dopant. In certain embodiments, the mixed oxide compositions as disclosed herein comprise about 1 to about 45 wt. % cerium on an oxide basis; about 40 to about 98 wt. % zirconium on an oxide basis; about 0.05 wt. % to about 0.50 wt. % iron on an oxide basis; about 0.015 wt. % to about 0.20 wt. % strontium on an oxide basis; and optionally an additional rare earth dopant. When present, each additional rare earth dopant may be present in an amount of about 0.5 to about 15 wt. % on an oxide basis. In certain embodiments, the additional rare earth dopant is selected from the group consisting of lanthanum, neodymium, yttrium, praseodymium, samarium, gadolinium, and mixtures thereof.
In specific embodiments, the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition. It is important that the mixed oxide composition as disclosed herein contains the mixture of strontium and iron in the recited amounts.
Even though the amounts of iron and strontium are small, these small amounts impart surprisingly improved properties to the disclosed mixed oxide compositions. The mixture of iron and strontium surprisingly provides the mixed oxide composition with improved OSC even after aging at elevated temperatures, and in particular improved OSC at lower temperatures. These improved properties are provided when both strontium and iron are present and present in the recited amounts. Too much iron leads to formation of perovskite phase when aged at elevated temperatures and this acts as a sintering aid causing a mixed oxide composition containing a higher amount of iron to sinter. After sintering there is a loss of BET surface area and that begins to negatively impact OSC resulting in a non-linear OSC response in comparison to the mixed oxide compositions within the scope of this disclosure containing the disclosed mixture of SrO and Fe2O3. The amounts of iron and strontium may be adjusted within the range disclosed herein to achieve the desired properties and avoid formation of a perovskite phase.
The mixed oxide composition comprises the above-noted components within the amounts indicated, but in certain embodiments it also may comprise other elements and/or small amounts of impurities. In other embodiments, the mixed oxide composition consists essentially of the above-noted components and the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition.
The additional rare earth dopants 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. In certain embodiments, the additional rare earth dopant is lanthanum, neodymium, yttrium, praseodymium, samarium, gadolinium, or mixtures thereof. In particular embodiments, the additional rare earth dopant is lanthanum, yttrium, or mixtures thereof. When present, each additional rare earth dopant may be present in an amount of about 0.5 to about 15 wt. % on an oxide basis. In certain embodiments, the mixed oxide composition contains an additional rare earth dopant in an amount of about 5 to about 15 wt. % on an oxide basis. In other embodiments, the mixed oxide composition contains about zero additional rare earth dopant.
The mixed oxide compositions may contain trace amounts of impurities. These impurities are typically present in an amount of about 1% by weight or less (to about zero or to an amount that is undetectable) 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 (of about 1% by weight to about zero or to an amount that is undetectable) may be present in any of the described embodiments of the mixed oxide compositions. When present and detectable, any impurities may be present in an amount of about 100 ppm or less.
In one embodiment, the mixed oxide compositions as disclosed herein comprise a) about 30 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 65 wt. % zirconium on an oxide basis; c) about 0.065 wt. % to about 0.75 wt. % iron on an oxide basis; d) about 0.015 wt. % to about 0.25 wt. % strontium on an oxide basis; and e) an additional rare earth dopant selected from the group consisting of lanthanum, yttrium, and mixtures thereof present in an amount of about 5 to about 15 wt. % on an oxide basis. In certain of these embodiments, the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition.
In another embodiment, the mixed oxide composition comprises a) about 30 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 65 wt. % zirconium on an oxide basis; c) about 0.05 wt. % to about 0.50 wt. % iron on an oxide basis; d) about 0.015 wt. % to about 0.20 wt. % strontium on an oxide basis; and e) optionally an additional rare earth dopant selected from the group consisting of lanthanum, yttrium, and mixtures thereof present in an amount of about 5 to about 15 wt. % on an oxide basis. In certain of these embodiments, the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition.
In a specific embodiment, the mixed oxide compositions as disclosed herein comprise a) about 30 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 65 wt. % zirconium on an oxide basis; c) about 0.05 wt. % to about 0.50 wt. % iron on an oxide basis; d) about 0.015 wt. % to about 0.20 wt. % strontium on an oxide basis; and e) an additional rare earth dopant selected from the group consisting of lanthanum, yttrium, and mixtures thereof present in an amount of about 5 to about 15 wt. % on an oxide basis. In certain of these embodiments, the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition.
In another embodiment, the mixed oxide compositions as disclosed herein comprise about 30 to about 45 wt. % cerium on an oxide basis, about 40 to about 65 wt. % zirconium on an oxide basis, about 0.1 wt. % to about 0.75 wt. % iron on an oxide basis, about 0.05 wt. % to about 0.25 wt. % strontium on an oxide basis, and optionally an additional rare earth dopant, with each optional additional rare earth dopant present in an amount of about 0.5 to about 15 wt. % on an oxide basis. In certain embodiments, when present, the total additional rare earth dopant is present in an amount of about 5 to about 15 wt. % on an oxide basis.
In another specific embodiment, the mixed oxide compositions as disclosed herein comprise about 30 to about 45 wt. % cerium on an oxide basis, about 40 to about 65 wt. % zirconium on an oxide basis, about 0.1 wt. % to about 0.50 wt. % iron on an oxide basis, about 0.05 wt. % to about 0.20 wt. % strontium on an oxide basis, and optionally an additional rare earth dopant, which when present is in an amount of about 5 to about 15 wt. % on an oxide basis.
In certain of these embodiments, the additional rare earth dopant is lanthanum, neodymium, yttrium, praseodymium, samarium, gadolinium, or mixtures thereof. In particular of these embodiments, the additional rare earth dopant is lanthanum, yttrium, or mixtures thereof. In certain of these embodiments, the mixed oxide composition contains the additional rare earth dopant in an amount of about 5 to about 15 wt. % on an oxide basis. And in other of these embodiments, the mixed oxide composition contains about zero additional rare earth dopant. In specific embodiments, the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition.
In further particular embodiments, the mixed oxide composition of the present disclosure consists essentially of CeO2, ZrO2, La2O3, Y2O3, Fe2O3, and SrO. In specific of these embodiments, the mixed oxide of the present disclosure consists essentially of CeO2, ZrO2, La2O3, Y2O3, Fe2O3, and SrO, wherein the ratio of Ce/Zr/La/Y/Sr/Fe is approximately 35 wt % to approximately 45 wt % cerium, approximately 45 wt % to approximately 55 wt % zirconium, approximately 3 wt % to approximately 6 wt % lanthanum, approximately 3 wt % to approximately 6 wt % yttrium, approximately 0.03 wt % to approximately 0.2 wt % strontium, and approximately 0.1 wt % to approximately 0.5 wt % iron on an oxide basis. In certain of these embodiments, the mixed oxide composition contains approximately 0.1 wt % to approximately 0.4 wt % iron on an oxide basis.
As described herein, the mixed oxide compositions containing both iron and strontium have improved OSC, even after aging at elevated temperatures, and in particular, surprisingly enhanced low temperature oxygen storage capacity (OSC). This improved or enhanced OSC is in comparison to a mixed oxide composition containing the same components (i.e., cerium, zirconium, and any optional rare earth dopants) in about the same constitutional amounts, except not containing strontium and iron, in which the amount of zirconium is varied to adjust for the absence of the strontium and iron. OSC is measured as described within the Examples.
After aging at 1100° C. for 10 hrs in air, the mixed oxide composition as disclosed herein may exhibit an Oxygen Storage Capacity (OSC) at about 200° C. to about 600° C. that is 2 to 8 times higher than an identical composition not containing a mixture of iron and strontium. In certain embodiments, after aging at 1100° C. for 10 hrs in air, the mixed oxide composition exhibits an Oxygen Storage Capacity (OSC) at about 250° C. to about 600° C. that is about 2 to about 8 times higher than an identical composition not containing a mixture of iron and strontium. In certain embodiments, after aging at 1100° C. for 10 hrs in air, the mixed oxide composition exhibits an Oxygen Storage Capacity (OSC) at about 250° C. to about 600° C. that is about 2 to about 7 times higher than an identical composition not containing a mixture of iron and strontium.
As defined above, “an identical composition not containing a mixture of iron and strontium” means a mixed oxide composition containing the same components (i.e., cerium, zirconium, and any optional rare earth dopants) in about the same constitutional amounts, except not containing strontium and iron, in which the amount of zirconium is varied to adjust for the absence of the strontium and iron.
In certain embodiments, after aging at 1100° C. for 10 hrs in air, the mixed oxide composition as disclosed herein may exhibit an Oxygen Storage Capacity (OSC) at about 250° C. to about 600° C. that is 2 to 4 times higher than an identical composition not containing a mixture of iron and strontium. As described, this improved OSC is particularly enhanced at low temperatures. As such, these improvements may be particularly evident at temperatures of about 200° C. to about 450° C. or at temperatures of about 250° C. to about 450° C.
In certain embodiments, after aging at 1150° C. for 6 hrs in air, the mixed oxide composition may exhibit an Oxygen Storage Capacity (OSC) at about 250° C. to about 600° C. that is 2 to 3 times higher than an identical composition not containing a mixture of iron and strontium. These improvements may be particularly evident at temperatures of about 200° C. to about 450° C. or at temperatures of about 250° C. to about 450° C.
Any of these improved OSC characteristics may be combined with one another and may be combined with any of the above-described embodiments of the mixed oxide compositions and/or with any of the below described properties.
The mixed oxide compositions also may exhibit other advantageous physical properties, both as prepared and after aging at elevated temperatures.
As described above, the mixed oxide compositions contain advantageously small amounts of iron and strontium, importantly such that after aging at elevated temperatures no perovskite phase is formed. As such, in certain embodiments, the mixed oxide composition exhibits no detectable perovskite or pyrochlore phases as determined by XRD after aging at 1100° C. for 10 hrs in air. The small amounts of iron and strontium may be varied such that after aging at elevated temperatures no perovskite phase is formed. The mixed oxide composition may exhibit a tetragonal phase or cubic phase as determined by XRD after aging at 1100° C. for 10 hrs in air.
In specific embodiments, the mixed oxide composition exhibits a tetragonal phase or cubic phase as determined by XRD after aging at 1150° C. for 6 hrs in air. The mixed oxide composition may exhibit no detectable perovskite or pyrochlore phases as determined by XRD after aging at 1150° C. for 6 hrs in air.
In specific embodiments, after aging at 1100° C. for 10 hrs in air, the mixed oxide compositions as disclosed herein may have a crystallite size of about 50 nm to about 100 nm.
Any of these crystalline phase embodiments may be combined and may be combined with any of the above-described embodiments of the mixed oxide compositions and/or with any of the below described properties.
As described herein formation of a detectable perovskite phase is undesirable. Too much iron (iron in amounts greater than in the presently disclosed mixed oxide composition) leads to formation of perovskite phase when aged at elevated temperatures and this acts as a sintering aid causing the mixed oxide composition to sinter. After sintering there is a loss of BET surface area that begins to negatively impact OSC. Any loss of OSC is undesirable and is avoided by the mixed oxide compositions as disclosed herein.
The mixed oxide compositions further may exhibit an advantageous BET surface area.
BET surface area is measured as described within the Examples. In certain embodiments, the mixed oxide compositions as disclosed herein exhibit a fresh BET surface area between about 40 and about 80 m2/g, and in certain embodiments, these mixed oxide compositions exhibit a fresh BET surface area of about 40 to about 50 m2/g. As described herein “fresh” means “as prepared” and is without any additional aging at elevated temperatures. In certain embodiments, the mixed oxide compositions exhibit a BET surface area of about 10 m2/g to about 20 m2/g when aged at 1100° C. for 10 hrs in air. In specific embodiments, the mixed oxide compositions exhibit a BET surface area of greater than about 2 m2/g to less than about 10 m2/g when aged at 1150° C. for 6 hrs in air. Despite the lower BET surface area after aging at 1150° C. for 6 hrs in air, OSC remains two to three times higher than identical compositions lacking SrO and Fe2O3.
Any of these BET surface areas embodiments may be combined and may be combined with any of the above-described embodiments of the mixed oxide compositions.
The mixed oxide compositions further may exhibit an advantageous particle size.
Particle size is measured as described within the Examples. In certain the mixed oxide compositions have a particle size characterized by a D90 of about 6 μm to about 20 μm and a D10 of about 1 μm to about 10 μm.
After at about 1100° C. for 4 hours in air, the mixed oxide compositions may have a H2TPR (Hydrogen Temperature Programmed Reduction) exhibiting a single symmetrical reduction peak when aged at about 1100° C. for 4 hours in air. H2TPR is measured as described within the Examples. The peak reduction temperature decreases as the mixture of iron oxide (Fe2O3) and strontium oxide (SrO) increases to within the amounts disclosed herein, which correlates with increased low temperature OSC performance, (see
Pore size is an important physical characteristic of the mixed oxide compositions. Pore size is measured as described within the Examples. Pores allow for diffusion of low molecular weight and high molecular weight macromolecule gas phase reactants. The mixed oxide compositions may exhibit advantageous pore sizes as prepared (after the initial thermal treatment/calcination associated with the manufacturing process). In some embodiments, primary, secondary, tertiary, and quaternary ammonium hydroxides are used as precipitating agents in the preparation of the mixed oxide compositions to augment pore size. As shown in
Any of the above-described embodiments of the mixed oxide compositions may be used in a catalyst or catalyst composition as an initial feed material.
The mixed oxide compositions as disclosed herein are made by methods as described in the appended Examples.
For example, in a first step a zirconium salt such as zirconium basic carbonate, a cerium compound (such as cerium hydroxide) or salts of cerium (such as cerium carbonate), and any optional additional rare earth dopant salts (such as yttrium carbonate) are dissolved in a mixture of deionized water and nitric acid. In the alternative soluble salts, such as nitrates or chlorides, can be utilized and dissolved directly in deionized water. The mixed rare earth zirconium nitrate solution is then precipitated with a mixture of deionized water, ammonium hydroxide, and lauric acid. The pH of this step is controlled to a pH of approximately 9 to approximately 11.
In a second step, any additional rare earth dopant salt (such as lanthanum carbonate) is dissolved with iron nitrate and strontium nitrate in nitric acid and deionized water. This mixture is added to the precipitate from the first step with pH controlled between approximately 9 and 11. The mixture is continuously mixed. A precipitate is formed and then filtered and washed.
The isolated precipitate is calcined/thermally treated at about 750° C. to about 1000° C. for about 4 hours to about 8 hours at temperature. In certain embodiments, the isolated precipitate is calcined/thermally treated at about 850° C. to about 1050° C. or at about 950±50° C.
The calcined material can be milled to a particular particle size if desired.
Further details of the preparation of the mixed oxide compositions are described in Examples 1-7 below.
Also disclosed herein are washcoat suspension composition for use as a component of a catalytic coating and preparation of these washcoat compositions. The washcoats are applied as a catalyst coating to a catalyst support. The washcoats as disclosed herein are applied to a substrate from a suspension, and then dried and thermally treated/calcined. The suspension also may be described as a slurry and these two terms are used interchangeably. After application to a support, the suspension is dried and calcined to create a dried and calcined washcoat powder.
This dried and calcined catalytic washcoat powder and the composite support (or substrate) can be referred to as a coated catalyst article, which once assembled or canned becomes a catalytic converter. This dried and calcined washcoat powder has improved tablOSC even after aging at elevated temperatures, in particular improved OSC at lower temperatures.
As disclosed herein, the washcoat suspension comprises: (i) a Platinum Group Metal (PGM) selected from group consisting of platinum, palladium, rhodium, iridium, osmium, ruthenium, and mixtures thereof and (ii) the mixed oxide compositions as disclosed herein. In some embodiments, the suspension can contain about 55 wt. % to about 65 wt % of the mixed oxide composition. These mixed oxide compositions include all of the embodiments of the mixed oxide compositions as described herein. As such, the mixed oxide compositions can comprise a) about 1 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 98 wt. % zirconium on an oxide basis; c) about 0.065 wt. % to about 0.75 wt. % iron on an oxide basis; d) about 0.015 wt. % to about 0.25 wt. % strontium on an oxide basis; and e) optionally an additional rare earth dopant. In certain embodiments, the mixed oxide compositions can comprise a) about 1 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 98 wt. % zirconium on an oxide basis; c) about 0.05 wt. % to about 0.50 wt. % iron on an oxide basis; d) about 0.015 wt. % to about 0.20 wt. % strontium on an oxide basis; and e) optionally an additional rare earth dopant.
The additional rare earth dopant can be any rare earth or a mixture thereof. In certain embodiments, the additional rare earth dopant selected from the group consisting of, lanthanum, neodymium, yttrium, praseodymium, samarium, gadolinium, and mixtures thereof. When present each optional additional rare earth dopant is present in an amount of about 0.5 to about 15 wt. % on an oxide basis. In specific embodiments, the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition.
It is noted that the washcoat suspensions include all of the mixed oxide compositions as disclosed herein and including all of the properties/characteristics as disclosed herein for the mixed oxide compositions.
In an embodiment, the washcoat suspensions include (i) a Platinum Group Metal (PGM) selected from group consisting of platinum, palladium, rhodium, mixtures thereof, and (ii) a mixed oxide composition comprising a) about 30 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 65 wt. % zirconium on an oxide basis; c) additional rare earth dopant selected from the group consisting of lanthanum, yttrium, and mixtures thereof present in an amount of about 5 to about 15 wt. % on an oxide basis; and d) a mixture of iron and strontium, wherein the iron is present in an amount of about 0.1 wt. % to about 0.75 wt. % on an oxide basis and the strontium is present in an amount of about 0.05 wt. % to about 0.25 wt. % on an oxide basis. In specific of these embodiments, the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition.
In certain embodiments, the washcoat suspensions include (i) a Platinum Group Metal (PGM) selected from group consisting of platinum, palladium, rhodium, mixtures thereof, and (ii) a mixed oxide composition comprising a) about 30 to about 45 wt. % cerium on an oxide basis; b) about 40 to about 65 wt. % zirconium on an oxide basis; c) additional rare earth dopant selected from the group consisting of lanthanum, yttrium, and mixtures thereof present in an amount of about 5 to about 15 wt. % on an oxide basis; and d) a mixture of iron and strontium, wherein the iron is present in an amount of about 0.1 wt. % to about 0.50 wt. % on an oxide basis and the strontium is present in an amount of about 0.05 wt. % to about 0.20 wt. % on an oxide basis. In specific of these embodiments, the amounts of the individual components will vary so that the total amount is about 100% of the mixed oxide composition.
In certain embodiments, the Platinum Group Metal (PGM) used in the washcoat suspension is rhodium or palladium, and in particular embodiments, the PGM is rhodium. In other embodiments, the PGM used in the washcoat suspension is palladium.
In embodiments in which the washcoat suspension composition contains rhodium, the suspension may comprise about 0.2 wt. % to about 0.50 wt. % rhodium as metal dispersed on a mixed oxide basis. In embodiments in which the washcoat suspension contains palladium, the suspension may comprise about 0.5 wt % to about 1.50 wt % palladium as metal dispersed on a mixed oxide basis.
The washcoat slurries as disclosed herein are prepared by adding the mixed oxide composition, an aluminum oxide (Al2O3), an insoluble alkaline earth (AE) salt, and a pseudoboehmite binder to deionized water. In certain embodiments, the aluminum oxide can be a La2O3 doped Al2O3. The deionized water also may contain a carboxylic acid and in certain embodiments, the carboxylic acid can be acetic acid. The carboxylic acid in the suspension can be utilized to adjust the pH of the suspension to about 4 to about 6. In certain embodiments, the deionized water further may contain sucrose. The final slurry has low nitric acid content.
The insoluble alkaline earth (AE) salt is used as a washcoat stabilizing agent and pore forming agent. In certain embodiments, the insoluble alkaline earth is barium sulfate (BaSO4), which minimizes solubility/interactions with the mixed oxide composition during the preparation of the washcoat slurry composition and is known to create porosity at elevated temperatures once in service.
As such, the washcoat slurry as described herein may contain one or more of La2O3 doped Al2O3, BaSO4, a pseudoboehmite binder, a carboxylic acid (such as acetic acid), and/or sucrose. In certain embodiments, the washcoat slurry has a solids content of about 40% by weight to about 50% by weight when dried and calcined at about 1000*50° C.
In some embodiments, the catalytic washcoat is prepared and the Platinum Group Metal (PGM) is added after the base slurry is prepared to minimize interactions with the mixed oxide composition. In some embodiments, the Platinum Group Metal (PGM) is selected from the group consisting of platinum, palladium, rhodium, iridium, osmium, ruthenium, as single metals, and as mixtures thereof, and in certain of these embodiments is palladium, rhodium, or a mixture thereof. The Platinum Group Metal (PGM) can be added to the base slurry as nitrate solutions prepared from nitrate salts of the Platinum Group Metal (PGM).
After the washcoat slurry compositions are prepared, these slurry compositions are dried/calcined at about 500° C. to about 600° C. for about 45 mins to about 3 hours.
The dried and calcined powders have improved OSC, even after aging at elevated temperatures, and in particular, surprisingly enhanced low temperature oxygen storage capacity (OSC). These improvements may be particularly evident at temperatures of about 250° C. to about 450° C. The dried and calcined powders exhibit an improved Oxygen Storage Capacity (OSC) at about 250° C. to about 600° C. in comparison to a dried and calcined suspension containing a mixed oxide composition with an identical composition but not containing the mixture of iron and strontium. In certain embodiments, this improvement can be particularly evident when the dried slurry powders contain rhodium as the Platinum Group Metal (PGM).
The mixed oxide compositions and slurry compositions as described herein are further characterized by and described in the following examples. These Examples also provide details on the techniques for measuring the physical characteristics of the mixed oxide compositions. However, the Examples are in no way limiting of the compositions as described herein.
Further details of the preparation of the washcoat suspensions are described in Examples 10-15 below.
OSC Measurements: OSC measurements were obtained under the following conditions. Powder samples were aged/heated under targeted conditions. 1100° C./10H Air and 1150° C./6H Air were used for data in Tables 2, 3, 4 and 7. For measurement of OSC, an O2 pulse chemisorption method was utilized with OSC measurements made at the desired temperatures. Examples include, but are not limited to, 200° C., 300° C., 350° C., 450° C., and 600° C. For instance, for OSC measurements at 350° C., characterization was performed in a Micrometrics Autochem 2920 system, where 0.1 g of the samples were weighed into a quartz sample tube with a packed quartz wool bed. The samples were then subjected to pre-treatment in which the temperature was first raised to 350° C. under the flow of 50 cm3/min He gas, then subjected to ten-time pulse application of 10% O2/He, followed by another twenty-time pulse application of 10% CO/He while being kept at the targeted temperature. Thereafter, the samples were subjected to pulse application of 10% O2/He until saturation was reached and the oxygen storage capacity was measured by the cumulative quantity of O2 absorbed at 350° C.
Compositional Content: ICP-OES (Inductively Coupled Plasma Optical Emission spectroscopy) manufactured by Agilent, Model #Agilent ICP-OES 5110 is used to provide accurate elemental analysis of the major components (e.g. Ce, Zr, La and Y), works by introducing the sample into a high temperature plasma to ionize and excite its atoms. As the excited species return into their ground state, they emit characteristic wavelengths of light, which are then dispersed and detected to create a spectrum. This allows for the identification and quantification of elements based on their unique wavelengths. The sample is first dissolved in acid to release the elements of interest, then atomized in the atomization chamber to form a fine aerosol and introduced into a plasma rectangular tube. This causes the sample to be directly excited by the argon plasma light source for spectroscopic determination, and the results are normalized. Calibration standards help relate intensity to concentration. AAS (Atomic Absorption Spectroscopy) manufactured by Agilent, Model #Agilent AAS 200 Series AA. This technique, which is used to provide accurate elemental analysis of Fe and Sr, works by introducing the sample into a flame to convert it into a fine aerosol. Next, a hollow cathode lamp is used to emit light at wavelengths corresponding to the absorption lines of the element of interest. At specific wavelengths, the atoms absorb the emitted light, and the amount of absorbed light is measured by a detector. The sample is first dissolved in acid to release the elements of interest. Strontium oxide and iron oxide are each measured by the standard curve method using a specific lamb plugged into the atomic absorption instrument then ionized in an air-acetylene flame aspirated as the dilute sample/acid medium. The decrease in intensity is proportional to the concentration of the element in the sample.
SEM Method: Scanning Electron Microscopy images were obtained using a JEOL model #JSM-6010LV with the powder sample being analyzed attached onto a sample stub via carbon tape. Scanning electron microscope (SEM) produced images of a sample by raster scanning the surface with a beam of high-energy electrons. Magnets focus the electron beam to a point several nanometers in diameter. As the electrons interact with atoms in the sample, various signals are produced and compiled by various imaging and analytical detectors. Generally, secondary electrons emitted by atoms excited by the electron beam are detected by a secondary electron detector to reveal surface topography.
SEM-EDS Method: For SEM energy-dispersed x-ray spectroscopy (EDS), the instrument used was manufactured by Oxford Instruments Model #x-act (10 mm2 Silicon Drift Detector). Sample preparation was the same as an SEM sample; powdered sample was attached onto a sample stub via carbon tape. Energy dispersive spectroscopy (EDS) makes use of the characteristic X-rays that are emitted from the sample during SEM imaging. These X-rays are emitted when outer shell electrons replace inner shell electrons which are displaced by the high-energy SEM electron beam. Because each element has a unique energy difference between outer and inner electron shells, characteristic X-rays are detected at specific energies and can be correlated with an elemental identification. A silicon drift detector (SDD) is the most common type of EDS detector used in a SEM instrument.
TEM-EDS Method: For transmission electronic microscopy EDS, the instrument used was manufactured by Thermofisher, Model #Thermofisher Talos F200X TEM with Super-X SDD detector. Transmission electron microscope (TEM) uses electron beams transmitted through a thin specimen to obtain high resolution images of its internal structure. It is often coupled with EDS technique to analyze the X-ray generated when the specimen is bombarded with electrons and provide information about the elemental composition of the sample. To prepare ultra-thin specimens (typically less than 100 nm) for electron transmission, the FIB technique is used to precisely mill and remove the material at the nanoscale with a beam of focused ion (typically gallium ions). The TEM sample was prepared by focus ion beam (FIB, Thermofisher Helios G4 UX) at 30 keV, and the final FIB cleaning of TEM lamella was performed at 5 keV to minimize the surface amorphization of the thin lamella.
XRD Method: For x-ray diffraction (XRD), the following method was used. The instrument used was manufactured by Malvern Panalytical Model #Empyrean Multipurpose X-ray diffractometer. Powder sample (1-2 g) was prepared by packing and flattening (by using a glass slide) the material being analyzed on a shallow-well sample holder. X-ray diffraction (XRD) is the result of constructive interference between X-rays and a crystalline sample. The wavelength of the X-rays used is of the same order of magnitude of the distance between the atoms in a crystalline lattice. This gives rise to a diffraction pattern that can be analyzed in several ways, the most popular being applying the famous Bragg's Law (nλ=2d sin θ) which is used in the measurement of crystals and their phases. A scan speed of 0.001395°/s and a step size of 0.0393908° was employed.
BET SA using N2 and BJH Pore Size/Radius and Pore Volume Method: This method was used to obtain BET (Brunauer, Emmett and Teller) Surface area (SA) and BJH (Barrett, Joyner, and Halenda) Pore Radius (PR) and Pore Volume (PV) data. The instrument used is the Micromeritics Model #ASAP 2460 Surface Area and Porosimetry Analyzer. To prepare a powder sample for analysis, the sample is first degassed at 350° C. for 2 hours. The technique involves exposing the material to N2 gas and measuring the amount of N2 gas adsorbed at different pressures. The BET theory, which is applied to determine the specific surface area of the material, relates to the amount of gas adsorbed at a given pressure to the monolayer coverage of N2 adsorbate on the surface. The BJH theory, which is applied to determine the pore volume and pore size distribution, analyzes the desorption isotherms over the range of relative pressures where the desorption occurs.
H2TPR Method: The following method was used to obtain H2TPR data. The instrument used was the Micrometrics Autochem H 2920 Automated Catalyst Characterization System. All samples analyzed were aged/heated at 1100° C./4H in Air. The gas used was 5% H2 in Argon, temperature program: ramping up to 1000° C. (ramp rate: 13° C./min). The reduction was repeated for two cycles, sample was oxidized before the second cycle.
Particle Size Method: Particle sizes were measured by laser using a Malvern Mastersizer. Particle size distribution does not require wet milling, thus reducing mechanical and chemical exposure during washcoat preparation stage. Additionally, dry milling reduces chemical attack caused by mechanical wet milling at elevated temperatures.
Catalytic Washcoat Simulation Test Method: Using a wire-wound rod with 1.0 mm spacing, a bead of slurry was placed on a smooth soda-lime glass sheet. The slurry was quickly drawn down evenly to produce a thin film ca. 25 μm (microns) thick. The glass plate was then quickly inserted into a drying oven controlling to 150° C. for 20 minutes to produce a dried film. The film was scraped off with a plastic spoon and collected for calcination at 550° C. for 2 hours. The calcined slurry powder was used for subsequent thermal aging studies (e.g., 1100° C. for 10 hours). This method simulates fast drying of a catalytic washcoat slurry. Slurry properties, physical properties and resulting OSC measurements can be found in Tables 5, 6, and 7 respectively, which are described in the Examples below.
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/50/5/5 CeO2/ZrO2/La2O3/Y2O3 was made by first dissolving 7.500 Kg ZBC (Zirconium basic carbonate), 3.636 Kg Ce(OH)4 (Cerium IV hydroxide), 0.545 Kg La2(CO3)3 (Lanthanum carbonate), and 0.475 Kg Y2(CO3)3 (Yttrium carbonate) in a mixture of 28 L DI H2O (deionized water) and 15 L 8M HNO3 (Nitric acid). The mixed rare earth zirconium nitrate solution was then precipitated with a mixture of 63 L DI H2O (deionized water), 31.5 L NH4OH (Ammonium hydroxide, 25% NH3 water) and 3.0 Kg C12H24O2(Lauric acid). The final pH was controlled between 9.5 and 10.0. Continuous mixing was employed throughout. The final precipitate was then filtered, washed, and calcined (calcined or calcination refers to the heat treatment during manufacturing) to 750° C. to 1000° C., with 950±50° C. preferred. The material was then milled to final particle size D90≤20 μm.
Further details are described in the Summary of Examples 1-7 below.
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/49.56/5/5/0.09/0.35 CeO2/ZrO2/La2O3/Y2O3/SrO/Fe2O3 was made by first dissolving 7.434 Kg ZBC (Zirconium basic carbonate), 3.636 Kg Ce(OH)4 (Cerium IV hydroxide) and 0.475 Kg Y2(CO3)3 (Yttrium carbonate) in a mixture of 28 L DI H2O (deionized water) and 15 L 8M HNO3 (Nitric acid). The mixed rare earth zirconium nitrate solution was then precipitated with a mixture of 63 L DI H2O (deionized water), 31.5 L NH4OH (Ammonium hydroxide, 25% NH3 water) and 3.0 Kg C12H24O2(Lauric acid). The final pH of step 1 was controlled between 9.5 and 10.0.
As a second step, a mixture of 0.545 Kg La2(CO3)3 (Lanthanum carbonate), 0.011 Kg Sr(NO3)2 (Strontium nitrate) and 0.106 Kg Fe(NO3)3.9H2O (Iron(III) Nitrate Nonahydrate) dissolved in 1.0 L 8M HNO3 (Nitric acid) and 2.6 L DI H2O (deionized water) was added to the precipitate from the first step with final pH controlled between 9.5 and 10.0. Continuous mixing was employed throughout. The resulting final precipitate was then filtered, washed and calcined to 750° C. to 1000° C., with 950±50° C. preferred. The material was then milled to final particle size D90≤20 μm.
Further details are described in the Summary of Examples 1-7 below.
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/49.67/5/5/0.33 CeO2/ZrO2/La2O3/Y2O3/Fe2O3 was made by first dissolving 7.451 Kg ZBC (Zirconium basic carbonate), 3.636 Kg Ce(OH)4 (Cerium IV hydroxide) and 0.475 Kg Y2(CO3)3 (Yttrium carbonate) in a mixture of 28 L DI H2O (deionized water) and 15 L 8M HNO3 (Nitric acid). The mixed rare earth zirconium nitrate solution was then precipitated with a mixture of 63 L DI H2O (deionized water), 31.5 L NH4OH (Ammonium hydroxide, 25% NH3 water) and 3.0 Kg C12H24O2(Lauric acid). The final pH of step 1 was controlled between 9.5 and 10.0.
As a second step, a mixture of 0.545 Kg La2(CO3)3 (Lanthanum carbonate) and 0.100 Kg Fe(NO3)3.9H2O (Iron(III) Nitrate Nonahydrate) dissolved in 1.0 L 8M HNO3 (Nitric acid) and 2.6 L DI H2O (deionized water) was added to the precipitate from the first step with final pH controlled between 9.5 and 10.0. Continuous mixing was employed throughout. The final precipitate was then filtered, washed and calcined to 750° C. to 1000° C., with 950±50° C. preferred. The material was then milled to final particle size D90≤20 μm.
Further details are described in the Summary of Examples 1-7 below.
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/49.79/5/5/0.04/0.17 CeO2/ZrO2/La2O3/Y2O3/SrO/Fe2O3 was made by first dissolving 7.469 Kg ZBC (Zirconium basic carbonate), 3.636 Kg Ce(OH)4 (Cerium IV hydroxide) and 0.475 Kg Y2(CO3)3 (Yttrium carbonate) in a mixture of 28 L DI H2O (deionized water) and 15 L 8M HNO3 (Nitric acid). The mixed rare earth zirconium nitrate solution was then precipitated with a mixture of 63 L DI H2O (deionized water), 31.5 L NH4OH (Ammonium hydroxide, 25% NH3 water) and 3.0 Kg C12H24O2(Lauric acid). The final pH of step 1 was controlled between 9.5 and 10.0.
As a second step, a mixture of 0.545 Kg La2(CO3)3 (Lanthanum carbonate), 0.005 Kg Sr(NO3)2 (Strontium nitrate) and 0.052 Kg Fe(NO3)3.9H2O (Iron(III) Nitrate Nonahydrate) dissolved in 1.0 L 8M HNO3 (Nitric acid) and 2.6 L DI H2O (deionized water) was added to the precipitate from the first step with final pH controlled between 9.5 and 10.0. Continuous mixing was employed throughout. The final precipitate was then filtered, washed and calcined to 750° C. to 1000° C., with 950±50° C. preferred. The material was then milled to final particle size D90≤20 μm.
Further details are described in the Summary of Examples 1-7 below.
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/47.82/5/5/0.45/1.73 CeO2/ZrO2/La2O3/Y2O3/SrO/Fe2O3 was made by first dissolving 7.173 Kg ZBC (Zirconium basic carbonate), 3.636 Kg Ce(OH)4 (Cerium IV hydroxide) and 0.475 Kg Y2(CO3)3 (Yttrium carbonate) in a mixture of 28 L DI H2O (deionized water) and 15 L 8M HNO3 (Nitric acid). The mixed rare earth zirconium nitrate solution was then precipitated with a mixture of 63 L DI H2O (deionized water), 31.5 L NH4OH (Ammonium hydroxide, 25% NH3 water) and 3.0 Kg C12H24O2(Lauric acid). The final pH of step 1 was controlled between 9.5 and 10.0.
As a second step, a mixture of 0.545 Kg La2(CO3)3 (Lanthanum carbonate), 0.055 Kg Sr(NO3)2 (Strontium nitrate) and 0.525 Kg Fe(NO3)3.9H2O (Iron(III) Nitrate Nonahydrate) dissolved in 1.1 L 8M HNO3 (Nitric acid) and 2.6 L DI H2O (deionized water) was added to the precipitate from the first step with final pH controlled between 9.5 and 10.0. Continuous mixing was employed throughout. The final precipitate was then filtered, washed and calcined to 750° C. to 1000° C., with 950±50° C. preferred. The material was then milled to final particle size D90≤20 μm.
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/49.12/5/5/0.18/0.70 CeO2/ZrO2/La2O3/Y2O3/SrO/Fe2O3 was made by first dissolving 7.368 Kg ZBC (Zirconium basic carbonate), 3.636 Kg Ce(OH)4 (Cerium IV hydroxide) and 0.475 Kg Y2(CO3)3 (Yttrium carbonate) in a mixture of 28 L DI H2O (deionized water) and 15 L 8M HNO3 (Nitric acid). The mixed rare earth zirconium nitrate solution was then precipitated with a mixture of 63 L DI H2O (deionized water), 31.5 L NH4OH (Ammonium hydroxide, 25% NH3 water) and 3.0 Kg C12H24O2(Lauric acid). The final pH of step 1 was controlled between 9.5 and 10.0.
As a second step, a mixture of 0.545 Kg La2(CO3)3 (Lanthanum carbonate), 0.022 Kg Sr(NO3)2 (Strontium nitrate) and 0.213 Kg Fe(NO3)3.9H2O (Iron(III) Nitrate Nonahydrate) dissolved in 1.0 L 8M HNO3 (Nitric acid) and 2.6 L DI H2O (deionized water) was added to the precipitate from the first step with final pH controlled between 9.5 and 10.0. Continuous mixing was employed throughout. The final precipitate was then filtered, washed and calcined to 750° C. to 1000° C., with 950±50° C. preferred. The material was then milled to final particle size D90≤20 μm.
Further details are described in the Summary of Examples 1-7 below.
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/49.79/5/5/0.04/0.17 CeO2/ZrO2/La2O3/Y2O3/SrO/Fe2O3 was made by first dissolving 7.469 Kg ZBC (Zirconium basic carbonate), 3.636 Kg Ce(OH)4 (Cerium IV hydroxide) and 0.475 Kg Y2(CO3)3 (Yttrium carbonate) in a mixture of 28 L DI H2O (deionized water) and 15 L 8M HNO3 (Nitric acid). The mixture was then heated to 50° C. The mixed rare earth zirconium nitrate solution was then precipitated with a mixture of 100 L DI H2O (deionized water), 5.3 Kg TMAOH (Tetra methyl ammonium hydroxide, 97%) and 3.0 Kg C12H24O2(Lauric acid), which was preheated to 50° C. The final pH of step 1 was controlled between 9.5 and 10.0.
As a second step, a mixture of 0.545 Kg La2(CO3)3 (Lanthanum carbonate), 0.005 Kg Sr(NO3)2 (Strontium nitrate) and 0.052 Kg Fe(NO3)3.9H2O (Iron(III) Nitrate Nonahydrate) dissolved in 1.0 L 8M HNO3 (Nitric acid) and 2.6 L DI H2O (deionized water) was added to the precipitate from the first step with final pH controlled between 9.5 and 10.0. Continuous mixing was employed throughout. The final precipitate was then filtered, washed and calcined to 750° C. to 1000° C., with 950±50° C. preferred. The material was then milled to final particle size D90≤20 μm.
Further details are described in the Summary of Examples 1-7 below.
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/49.87/5/5/0.03/0.10 CeO2/ZrO2/La2O3/Y2O3/SrO/Fe2O3 was made by first dissolving 7.481 Kg ZBC (Zirconium basic carbonate), 3.637 Kg (NH4)2[Ce(NO3)6](Ammonium Cerium Nitrate) and 28 L DI H2O (deionized water) and 10 L 8M HNO3 (Nitric acid) and heating for 1 h @55-65° C.
As a second step, a mixture of 0.545 Kg La2(CO3)3 (Lanthanum carbonate), 0.475 Kg Y2(CO3)3 (Yttrium carbonate), 0.0032 Kg Sr(NO3)2 (Strontium nitrate) and 0.0308 Kg Fe(NO3)3.9H2O (Iron(III) Nitrate Nonahydrate) dissolved in 5.0 L 8M HNO3 (Nitric acid) and 2.6 L DI H2O (deionized water) was added to the first step. The mixed rare earth zirconium nitrate solution was then precipitated with a mixture of 63 L DI H2O (deionized water), 31.5 L NH4OH (Ammonium hydroxide, 25% NH3 water) and 3.0 Kg C12H24O2(Laurie acid). The final pH was controlled between 9.5 and 10.0. Continuous mixing was employed throughout. The final precipitate was then filtered, washed and calcined to 750° C. to 1000° C., with 950±50° C. preferred. The material was then milled to final particle size D90≤20 μm.
Further details are described in the Summary of Examples 1-7 below.
The compositions of Examples 1-7 were characterized as described below. Data and compositional analyses are also provided.
The compositional content of the compositions of Examples 1-7 were measured by ICP spectroscopy. After aging at 1000° C./10H air, the compositions were analyzed by XRD, and the BET surface area was measured for the as-prepared compositions (i.e., fresh) and after aging/heating at 1100° C./10H air and 1100° C./10H air. This additional aging (heat) treatment is performed at for the specified time and temperature in the specified atmosphere. Particle size also was measured. Table 1 below summarizes these results.
The compositional analyses confirm that the amounts of CeO2, ZrO2, La2O3, Y2O3 SrO, and Fe2O3. XRD are illustrated in
After the compositions of Examples 1, 2, 3, 4, 5A, 5B, and 7 were aged/heated at 1100° C./10H Air, OSC measurements were obtained and the % improvements for Examples 2-7 in comparison to Example 1 were calculated. This data is summarized in Table 2 and graphed in
Table 2 shows the % OSC improvement of Examples 2 and 4 relative to Example 1, which is compositionally comparable but does not include SrO and Fe2O3 (i.e., the amount of ZrO2 is slightly adjusted for the addition of SrO and Fe2O3 but otherwise the compositions are identical within experimentally acceptable error/variation). The compositions containing the disclosed mixture of SrO and Fe2O3 (Examples 2 and 4) demonstrate superior OSC (especially at lower temperatures) in comparison to comparative Example 1. Example 2 also demonstrates superior OSC properties in comparison to comparative Example 3 (no SrO) and Example 5A (higher amount of Fe2O3 leading to perovskite formation and sintering), as well as Example 5B (slightly higher amount of Fe2O3 which also led to perovskite formation and sintering).
The composition of Examples 4 and 7 also include a disclosed mixture of SrO and Fe2O3, but in smaller amounts. Example 7 also has improved thermal stability as exemplified by high BET surface area post aging at 1100° C./10 h in air. These observed benefits are based on starting materials and the process used to produce the mixed oxides making the resulting OSC formulations tunable based on amount of SrO and Fe2O3 contained, and the preparation method used to produce the mixed oxide. The composition of Example 3 contains Fe2O3 at same amount as Example 2, but does not contain SrO, demonstrating the importance of SrO to improve OSC (especially at lower temperatures) in comparison to a composition containing Fe2O3 alone. The compositions of Example 5A (as well as Example 5B), which include a higher amount of Fe2O3, do not show the overall improved results of Examples 2 and 4 due to sintering effect (loss of BET) caused by the formation of LaFeO3 perovskite as detected via XRD. Thus, these results demonstrate the importance of using the claimed mixture of SrO and Fe2O3 to improve OSC, especially at lower temperatures.
After the compositions of Examples 1-3 were aged/heated at 1150° C./6H Air, OSC measurements were obtained and the % improvements for Examples 2 and 3 in comparison to Example 1 were calculated. This data is summarized in Table 3 and the OSC data was graphed as illustrated in
The results in Table 3 demonstrate that post 1150° C./6H Air aging the composition of Example 2 has a BET surface area significantly below 10 m2/g, but with improved OSC.
The results in Table 3 and illustrated in
Table 4 summarizes characterizations of Examples 1, 3, 4, and 6. In particular, Table 4 demonstrates the effects of changing the precipitating agent used during preparation of the compositions. Table 4 demonstrates that changing the precipitating agent used during preparation of the compositions can impact pore size. Examples 1, 3, and 4 used NH4OH as the precipitating agent. In contrast, Example 6 has the same composition as Example 4, but used quaternary ammonium hydroxide (QAH) tetra methyl ammonium hydroxide (TMAOH) as the precipitating agent.
After the compositions of Examples 1, 3, 4, and 6 were aged/heated at 1100° C./10H Air, OSC measurements were obtained. This data is summarized in Table 4 and the data was graphed as illustrated in
The results in Table 4 and illustrated in
The data in Table 4 and as illustrated in
Compositions of Examples 2, 5A, and 5B were further characterized by TEM and EDS, as well as XRD as described above and further described below.
As described above, the XRD of Examples 5A and 5B (
The presence of perovskite LaFeO3 is significant because it acts as a sintering aid causing the mixed oxide composition of Example 5A, as well as Example 5B, to sinter. Although the OSC of Examples 5A and 5B remain higher than Example 1, the loss of BET surface area begins to negatively impact OSC resulting in a non-linear OSC response in comparison to the mixed oxide compositions containing a preferred mixture of SrO and Fe2O3.
H2TPR data was obtained for slurries of Examples 1, 2, 4, and 6 as-prepared (i.e., fresh) and after aging/heating at 1100° C./4H in Air.
After the compositions of Examples 1, 2, 4, and 6 were aged/heated at 1100° C./10H Air, OSC measurements were obtained. This data is summarized in Table 5 and the data was graphed as illustrated in
The data as summarized in Table 5 and illustrated in
Importantly, and as can be seen from the OSC data in comparison to the H2TPR results, the trend for what compositions have the higher OSC at a given temperature is reversed relative to what compositions have higher H2TPR (i.e., Example 2 has the highest OSC and lowest H2TPR and Comparative Example 1 has the lowest OSC and highest H2TPR). This trend demonstrates that a lower H2TPR reduction temperature is indicative of a more active OSC material. A lower H2TPR peak temperature demonstrates a more active/lower light-off temperature and is indicative of improved low temperature OSC.
Table 6 summarizes H2TPR data for the compositions of Examples 1, 2, 4, and 6 as-prepared (i.e., fresh) and after aging/heating at 1100° C./4H Air. Table 6 also summarizes BET and XRD after aging/heating at 1000° C./10H using CO/O2 rich/lean atmosphere cycling for Examples 1, 2, 4, and 6.
The XRD results as summarized in Table 6 and illustrated in
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/49.3/5/5/0.2/0.5, CeO2/ZrO2/La2O3/Y2O3/SrO/Fe2O3 is made by first dissolving 7.395 Kg ZBC (Zirconium basic carbonate), 3.636 Kg Ce(OH)4 (Cerium IV hydroxide) and 0.475 Kg Y2(CO3)3 (Yttrium carbonate) in a mixture of 28 L DI H2O (deionized water) and 15 L 8M HNO3 (Nitric acid). The mixed rare earth zirconium nitrate solution is then precipitated with a mixture of 63 L DI H2O (deionized water), 31.5 L NH4OH (Ammonium hydroxide, 25% NH3 water) and 3.0 Kg C12H24O2(Lauric acid). The final pH of step 1 is controlled between 9.5 and 10.0.
As a second step, a mixture of 0.545 Kg La2(CO3)3 (Lanthanum carbonate), 0.025 Kg Sr(NO3)2 (Strontium nitrate) and 0.152 Kg Fe(NO3)3.9H2O (Iron(III) Nitrate Nonahydrate) dissolved in 1.0 L 8M HNO3 (Nitric acid) and 2.6 L DI H2O (deionized water) is added to the precipitate from the first step with final pH controlled between 9.5 and 10.0. Continuous mixing is employed throughout. The final precipitate is then filtered, washed and calcined at 750° C. to 1000° C., with 950±50° C. preferred. The material is then milled to final particle size D90≤20 μm.
A 6.0 Kg batch of Ceria Zirconia with targeted composition, 40/49.94/5/5/0.02/0.05 CeO2/ZrO2/La2O3/Y2O3/SrO/Fe2O3 was made by first dissolving 7.490 Kg ZBC (Zirconium basic carbonate), 3.636 Kg (NH4)2[Ce(NO3)6](Ammonium Cerium Nitrate) and 28 L DI H2O (deionized water) and 10 L 8M HNO3 (Nitric acid) and heating for 1 h @55-65° C.
As a second step, a mixture of 0.545 Kg La2(CO3)3 (Lanthanum carbonate), 0.475 Kg Y2(CO3)3 (Yttrium carbonate), 0.00018 Kg Sr(NO3)2 (Strontium nitrate) and 0.0152 Kg Fe(NO3)3.9H2O (Iron(III) Nitrate Nonahydrate) dissolved in 5.0 L 8M HNO3 (Nitric acid) and 2.6 L DI H2O (deionized water) was added to the first step. The mixed rare earth zirconium nitrate solution was then precipitated with a mixture of 63 L DI H2O (deionized water), 31.5 L NH4OH (Ammonium hydroxide, 25% NH3 water) and 3.0 Kg C12H24O2(Lauric acid). The final pH was controlled between 9.5 and 10.0. Continuous mixing was employed throughout. The final precipitate was then filtered, washed and calcined to 750° C. to 1000° C., with 950±50° C. preferred. The material was then milled to final particle size D90≤20 μm.
A 6.0 Kg oxide basis washcoat slurry was prepared by adding 3.75 Kg Example 1, 1.78 Kg La2O3/Al2O3, 0.55 Kg BaSO4 and 0.09 Kg Pseudoboehmite binder to 6.24 Kg DI water, 0.3 Kg glacial acetic acid and 0.15 Kg Sucrose. The final slurry solid content for coating was targeted at 43%, 1000° C. solids basis.
The washcoat was prepared and dried/calcined (550° C. for 2 hours). Chemical data for the composition can be found below in Table 7, and physical data for the composition can be found below in Table 8.
Then the dried slurry powder was aged 1100° C. for 10 hours in Air and OSC was measured per the method described herein. Table 9 presents OSC data for the aged mixed-oxide washcoat under three circumstances: as the mixed-oxide washcoat only (prior to addition of a PGM, i.e., ex-PGM), as the washcoat plus 1.5% wt. Pd as metal calculated on a mixed oxide basis (301.3 g Pd—N added as a solution supplied at 18% Pd metal content), and as the washcoat plus 0.5% Rh as metal calculated on a mixed oxide basis (181.9 g Rh—N added as a solution supplied at 10% Rh metal content).
A 6.0 Kg oxide basis washcoat slurry was prepared by adding 3.75 Kg Example 2, 1.78 Kg La2O3/Al2O3, 0.55 Kg BaSO4 and 0.09 Kg Pseudoboehmite binder to 6.24 Kg DI water, 0.3 Kg glacial acetic acid and 0.15 Kg Sucrose. The final slurry solid content for coating was targeted at 43%, 1000° C. solids basis.
The washcoat was prepared and dried/calcined (550° C. for 2 hours). Chemical data for the composition can be found below in Table 7, and physical data for the composition can be found below in Table 8.
Then the dried slurry powder was aged 1100° C. for 10 hours in Air and OSC was measured per the method described herein. Table 9 presents OSC data for the aged mixed-oxide washcoat described herein under three circumstances: as the mixed-oxide washcoat only (prior to addition of a PGM, i.e., ex-PGM), as the washcoat plus 1.5% wt. Pd as metal calculated on a mixed oxide basis (301.3 g Pd—N added as a solution supplied at 18% Pd metal content), and as the washcoat plus 0.5% Rh as metal calculated on a mixed oxide basis (181.9 g Rh—N added as a solution supplied at 10% Rh metal content).
A 6.0 Kg oxide basis washcoat slurry was prepared by adding 3.75 Kg Example 3, 1.78 Kg La2O3/Al2O3, 0.55 Kg BaSO4 and 0.09 Kg Pseudoboehmite binder to 6.24 Kg DI water, 0.3 Kg glacial acetic acid and 0.15 Kg Sucrose. The final slurry solid content for coating was targeted at 43%, 1000° C. solids basis.
The washcoat was prepared and dried/calcined (550° C. for 2 hours). Chemical data for the composition can be found below in Table 7, and physical data for the composition can be found below in Table 8.
Then the dried slurry powder was aged 1100° C. for 10 hours in Air and OSC was measured per the method described herein. Table 9 presents OSC data for the aged mixed-oxide washcoat described herein under three circumstances: as the mixed-oxide washcoat only (prior to addition of a PGM, i.e., ex-PGM), as the washcoat plus 1.5% wt. Pd as metal calculated on a mixed oxide basis (301.3 g Pd—N added as a solution supplied at 18% Pd metal content), and as the washcoat plus 0.5% Rh as metal calculated on a mixed oxide basis (181.9 g Rh—N added as a solution supplied at 10% Rh metal content).
A 6.0 Kg oxide basis washcoat slurry was prepared by adding 3.75 Kg Example 1, 1.78 Kg La2O3/Al2O3, 0.55 Kg BaSO4 and 0.09 Kg Pseudoboehmite binder to 6.24 Kg DI water, 0.3 Kg glacial acetic acid and 0.15 Kg Sucrose. The final slurry solid content for coating was targeted at 43%, 1000° C. solids basis.
The washcoat was prepared and dried/calcined (550° C. for 2 hours). Chemical data for the composition can be found below in Table 7, and physical data for the composition can be found below in Table 8.
Then the dried slurry powder was aged 1100° C. for 10 hours in Air and OSC was measured per the method described herein. Table 10 presents OSC data for the aged mixed-oxide washcoat plus 0.23% Rh as metal on a mixed oxide basis (83.2 g Rh—N added as a solution supplied at 10% Rh metal content).
A 6.0 Kg oxide basis washcoat slurry was prepared by adding 3.75 Kg Example 2, 1.78 Kg La2O3/Al2O3, 0.55 Kg BaSO4 and 0.09 Kg Pseudoboehmite binder to 6.24 Kg DI water, 0.3 Kg glacial acetic acid and 0.15 Kg Sucrose. The final slurry solid content for coating was targeted at 43%, 1000° C. solids basis.
The washcoat was prepared and dried/calcined (550° C. for 2 hours). Chemical data for the composition can be found below in Table 7, and physical data for the composition can be found below in Table 8.
Then the dried slurry powder was aged 1100° C. for 10 hours in Air and OSC was measured per the method described herein. Table 10 presents OSC data for the aged mixed-oxide washcoat plus 0.23% Rh as metal on a mixed oxide basis (83.2 g Rh—N added at 10% Rh content).
A 6.0 Kg oxide basis washcoat slurry was prepared by adding 3.75 Kg Example 3, 1.78 Kg La2O3/Al2O3, 0.55 Kg BaSO4 and 0.09 Kg Pseudoboehmite binder to 6.24 Kg DI water, 0.3 Kg glacial acetic acid and 0.15 Kg Sucrose. The final slurry solid content for coating was targeted at 43%, 1000° C. solids basis.
The washcoat was prepared and dried/calcined (550° C. for 2 hours). Chemical data for the composition can be found below in Table 7, and physical data for the composition can be found below in Table 8.
Then the dried slurry powder was aged 1100° C. for 10 hours in Air and OSC was measured per the method described herein. Table 10 presents OSC data for the aged mixed-oxide washcoat plus 0.23% Rh as metal on a mixed oxide basis (83.2 g Rh—N added as a solution supplied at 10% Rh metal content).
The compositional contents of the washcoats of Examples 10-15 are summarized in Table 7 below.
Table 8 summarizes the solids content, pH, and viscosity of the washcoat slurries of Examples 10-15. Table 8 also provides the particle size distribution of these washcoats after the washcoats were dried/calcined (550° C. for 2 hours). Table 8 further summarizes the SA BET after the dried slurry powders of the washcoats of Examples 10-15 were aged at 1100° C. for 10 hours in air.
As described, the example washcoats were dried/calcined (550° C. for 2 hours) and then the dried slurry powders of the washcoats of Examples 10-12 were aged at 1100° C. for 10 hours in air. After the washcoats of Examples 10-12 were aged/heated at 1100° C./10H Air, OSC measurements were obtained and the % improvements for Examples 11 and 12 in comparison to Example 10 were calculated. This data is summarized in Table 9, and the data was graphed as illustrated in
The results in Table 9 and illustrated in
The results in Table 9 and illustrated in
The results in Table 9 and illustrated in
As described, the example washcoats of Examples 13-15 were dried/calcined (550° C. for 2 hours) and then the dried slurry powders of these washcoats were aged at 1100° C. for 10 hours in air. After the washcoats of Examples 13-15 were aged/heated at 1100° C./10H Air, OSC measurements were obtained and the % improvements for Examples 14 and 15 in comparison to Example 13 were calculated. This data is summarized in Table 10, and the data was graphed as illustrated in
The results in Table 10 and illustrated in
Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the technology are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
It will be clear that the compositions and methods described herein are well adapted to attain the ends and advantages mentioned as well as those inherent therein. Those skilled in the art will recognize that the methods and systems within this specification may be implemented in many manners and as such are not to be limited by the foregoing exemplified embodiments and examples. In this regard, any number of the features of the different embodiments described herein may be combined into one single embodiment and alternate embodiments having fewer than or more than all of the features herein described are possible.
While various embodiments have been described for purposes of this disclosure, various changes and modifications may be made which are well within the scope contemplated by the present disclosure. Numerous other changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed in the spirit of the disclosure.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as disclosed. Thus, it is intended that the present invention include modifications and variations that are within the scope of the appended claims and their equivalents.
This application claims priority to U.S. Provisional Application No. 63/623,469, filed on 22 Jan. 2024, and U.S. Provisional Application No. 63/626,197, filed on 29 Jan. 2024, the complete disclosures of which are incorporated herein by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 63623469 | Jan 2024 | US | |
| 63626197 | Jan 2024 | US |
