WO2016203371A1

WO2016203371A1 - Performance improvement of copper and manganese containing ternary spinel as noble metal free three way catalysts

Info

Publication number: WO2016203371A1
Application number: PCT/IB2016/053506
Authority: WO
Inventors: Zahra NAZARPOOR; Stephen J. Golden
Original assignee: Clean Diesel Technologies, Inc.
Priority date: 2015-06-15
Filing date: 2016-06-14
Publication date: 2016-12-22

Abstract

Methods for improving the stoichiometric catalytic conversion of zero-platinum group metals (ZPGM; platinum group metal free) catalyst materials including ternary spinel oxides are disclosed. The ZPGM catalyst materials comprise Cu-Mn-X ternary spinel oxides. The Cu-Mn-X ternary spinel oxides are produced by implementing a partial substitution within the B-site cation of a CuMn₂04 spinel employing a general formulation CuMn_2-yX_y04, in which y is a variable representing different molar ratios and X is a cation that is not easily reducible. yis a number from 0.01 to 1.99. X is selected from the group consisting of nickel, titanium, aluminum, magnesium, cobalt, barium, lanthanum, cadmium, tin, yttrium, zirconium, and combinations thereof. The stoichiometry conversion of the ZPGM catalyst materials are improved by cation (X) doping, by calcining the ternary spinels at suitable temperatures, by varying the spinel loadings on support oxide, and by improving the oxygen storage capacity. Test results indicate that the ZPGM catalyst materials with improved stoichiometric conversion performance are obtained by improving concentration of Cu⁺¹, the purity of spinel phase, the loading and dispersion of the spinel, and improving the OSC of the spinel.

Description

PERFORMANCE IMPROVEMENT OF COPPER AND MANGANESE CONTAINING TERNARY SPINEL AS NOBLE METAL FREE THREE WAY CATALYSTS

BACKGROUND

Field of the Disclosure

This disclosure relates generally to zero-platinum group metals (ZPGM) catalyst materials, and more particularly, to methods for improving the catalytic performance of ternary spinel oxides at stoichiometric condition for use in a plurality of catalyst applications.

Background Information

Conventional gasoline exhaust systems employ three-way catalysts (TWC) technology and are referred to as TWC systems. TWC systems convert the toxic CO, HC and NOx into less harmful pollutants. Typically, TWC systems include a substrate structure upon which a layer of supporting and sometimes promoting oxides are deposited. Catalysts, based on platinum group metals (PGM), are then deposited upon the supporting oxides. Conventional PGM materials include platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), or combinations thereof. Although PGM catalyst materials are effective for toxic emission control and have been commercialized by the emissions control industry, PGM materials are scarce and expensive. The high cost remains a critical factor for widespread applications of PGM catalyst materials. As changes in the formulation of catalysts continue to increase the cost of TWC systems, the need for catalysts of significant catalytic performance has directed efforts toward the development of catalytic materials capable of providing the required synergies to achieve greater catalytic performance. Additionally, compliance with ever stricter environmental regulations and the need for lower manufacturing costs require new types of TWC systems. Therefore, there is a continuing need to provide TWC systems exhibiting catalytic properties substantially similar to or exceeding the catalytic properties exhibited by conventional TWC systems employing PGM catalyst materials.

SUMMARY

The present disclosure describes zero-platinum group metals (ZPGM) catalyst materials compositions including binary and ternary spinel oxides to develop suitable ZPGM catalyst materials with high performance at stoichiometric condition. Further, the present disclosure describes a process for improving the catalytic conversion at stoichiometric condition by employing different methodologies, such as, for example aliovalent doping to change the cation distribution, variable spinel loadings and dispersion, variable calcination temperatures to improve phase purity, and enhancing the oxygen storage capacity (OSC). These ZPGM material compositions with improved stoichiometric catalytic conversion can be employed for a variety of catalyst applications, such as, for example oxygen storage material (OSM) applications, and ZPGM and synergized-PGM (SPGM) three-way catalyst (TWC) systems, amongst others. In some embodiments, the ZPGM catalyst materials include binary spinel oxide compositions, which are synthesized using conventional synthesis methodologies. In these embodiments, the binary spinel oxide compositions are implemented as copper (Cu)- manganese (Mn) spinel oxide compositions. Further to these embodiments, the Cu-Mn spinel oxides are produced using a general formulation Cu_xMn3-_x04 in which x is a variable representing molar ratios within a range from about 0.01 to about 2.99. In an example, x takes a value of about 1.0 for a CuMmCn spinel oxide composition.

In other embodiments, the ZPGM catalyst materials include ternary spinel oxide compositions, which are synthesized using conventional synthesis methodologies. In these embodiments, the ternary spinel oxide compositions are implemented as a partial substitution within the B-site cation of a CuMmCn binary spinel employing a general formulation CuMm-yXyCn. Further to these embodiments, y is a variable representing different molar ratios and X is an aliovalent dopant element. In these embodiments, X is selected to a cation that is not easily reducible, such as, for example nickel, aluminum, titanium, magnesium, cobalt, barium, lanthanum, cadmium, tin, yttrium, and zirconium, amongst others. In an example, X is implemented as nickel (Ni). In this example, y takes a value from about 0 to about 2.0 for a variety of Cu-Mn-X ternary spinel oxide compositions. In further embodiments, the Cu-Mn binary and Cu-Mn-X ternary spinels are deposited onto support oxides. Examples of support oxides are AI2O3, doped AI2O3, ZrC , doped ZrC"2, S1O2, doped S1O2, T1O2, doped T1O2, Al₂0₃-Zr0₂, doped Al₂03-Zr02, or mixtures thereof, amongst others. Further, doping materials within doped support oxides include Ca, Sr, Ba, Y, La, Ce, Nd, Pr, Nb, Si, or Ta oxides, amongst others. In these embodiments, Cu-Mn binary and Cu-Mn-X ternary spinels are aged employing a rich-lean mode aging protocol and further tested employing a TWC isothermal steady-state sweep testing from lean to rich conditions and compared with an aged PGM reference catalyst.

In some embodiments, as the aliovalent dopant (X) concentration increases the Cu is increasingly present as Cu⁺¹ (versus Cu⁺²) within Cu-Mn-X ternary spinels. In these embodiments, this aforementioned increase in Cu⁺¹ concentration is also confirmed by employing an X-ray photoelectron spectroscopy (XPS). Further to these embodiments, the spinel phase purity and variable spinel loading concentration deposited onto support oxides exhibit improvements in stoichiometric conversion. Still further to these embodiments, increased OSC by adding suitable rare-earth metals enhances the stoichiometric conversion of the Cu-Mn-X ternary spinels.

In one embodiment, the present invention is directed to a catalytic composition comprising a ternary spinel having the formula: CuMm-yXyC , wherein X is an aliovalent dopant element that is a cation not easily reducible, and y is a number from 0.01 to 1.99. In some embodiments, X is selected from the group consisting of nickel, titanium, aluminum, magnesium, cobalt, barium, lanthanum, cadmium, tin, yttrium, zirconium and combinations thereof. In an example, X is implemented as nickel (Ni).

In one embodiment, y is a number greater than any one or more of 0.01, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 075, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.5, 1.55, 1.6, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, and 1.95. In some embodiments, y is a number that is less than any one or more of 1.99, 1.95, 1.90, 1.85, 1.80, 1.75, 1.70, 1.65, 1.60, 1.55, 1.50, 1.45, 1.40, 1.35, 1.30, 1.25, 1.20, 1.15, 1.10, 1.05, 1.00, 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, 0.65, 0.60, 0.55, 0.50, 0.45, 0.40, 0.35, 0.30, 0.25, 0.20, 0.15, 0.10, 0.05, 0.025. In one embodiment according to anyone of the preceding paragraphs, y is a number ranging from 0.05 to 1.9. For example, y may be a number ranging from 0.1 to 1.9; a number ranging from 0.2 to 1.9; a number ranging from 0.3 to 1.9; a number ranging from 0.4 to 1.9; a number ranging from 0.5 to 1.9; a number ranging from 0.6 to 1.9; a number ranging from 0.7 to 1.9; a number ranging from 0.8 to 1.9; a number ranging from 0.9 to 1.9; a number ranging from 1.0 to 1.9; a number ranging from 1.1 to 1.9; a number ranging from 1.2 to 1.9; a number ranging from 1.3 to 1.9; a number ranging from 1.4 to 1.9; or a number ranging from 1.5 to 1.9.

In a preferred embodiment, y is a number less than 2.0 and greater than 1.0, such as a number ranging from 1.4 to 1.8.

In one embodiment, the catalytic composition according to any one or more of the four preceding paragraphs, exhibits an atomic percent of Cu⁺¹ in the ternary spinel that is from about 10 to about 500% greater than an atomic percent of Cu⁺² in the ternary spinel. For example, the catalytic composition may have an atomic percent of Cu⁺¹ in the ternary spinel that is from about 50 to about 500% greater than an atomic percent of Cu⁺² in the ternary spinel, and in particular, from about 100 to about 500% greater than an atomic percent of Cu⁺² in the ternary spinel.

In some embodiments, catalytic composition further includes a support oxide on which the ternary spinel is deposited. In one embodiment, the support oxide is selected from the group consisting of AI2O3, doped AI2O3, Zr0₂, doped Zr0₂, S1O2, doped S1O2, T1O2, doped T1O2, Al₂03-Zr0₂, doped Al₂03-Zr0₂, and mixtures thereof. Examples of dopants that may be sued in the support oxide include Ca, Sr, Ba, Y, La, Ce, Nd, Pr, Nb, Si, Ta oxides, and mixtures thereof

In one embodiment, the catalytic composition has a loading of the ternary spinel that is from about 5 to about 20 weight percent, based on the total weight of the catalytic composition. In one embodiment, the composition has been calcined at a temperature from about

500 °C to about 800 °C, and has a loading of the ternary spinel that is from about 10 to about 20 weight percent, based on the total weight of the composition. For example, in some embodiments the composition has been calcined at a temperature of about 600 °C, and has a loading of the ternary spinel that is from about 12 to about 18 weight percent, based on the total weight of the composition. In further embodiments, the catalytic composition has been calcined at a temperature from about 800 °C to 1,000 °C, and has a loading of the ternary spinel that is from about 5 to 20 weight percent, based on the total weight of the composition. For example, in one embodiment the catalytic composition has been calcined at a temperature of about 900 °C, and has a loading of the ternary spinel that is from about 5 to 20 weight percent, based on the total weight of the composition. In another embodiment, the catalytic composition has been calcined at a temperature of about 900 °C, and has a loading of the ternary spinel that is from about 6 to about 18 weight percent, based on the total weight of the composition. In a preferred embodiment, the catalytic composition has been calcined at a temperature of about 900 °C, and has a loading of the ternary spinel that is about 12 weight percent, based on the total weight of the composition.

In some embodiments, the catalytic composition may be calcined at a temperature of about 1,000 °C, and may have a loading of the ternary spinel that is from about 5 to about 20 weight percent, based on the total weight of the composition. In one particular embodiment, the catalytic composition has been calcined at a temperature of about 1,000 °C, and has a loading of the ternary spinel that is from about 6 to about 18 weight percent, based on the total weight of the composition, and more particularly, has been calcined at a temperature of about 1,000 °C, and has a loading of the ternary spinel that is from about 12 to about 18 weight percent, based on the total weight of the composition. In one embodiment, the catalytic composition: i) has a loading of the ternary spinel that is from about 10 to about 20 weight percent, based on the total weight of the composition, and the composition has been calcined at a temperature from about 600 °C to about 1,000 °C; or ii) a loading of the ternary spinel that is from about 5 to about 10 weight percent, based on the total weight of the composition, and the composition has been calcined at a temperature from about 800 °C to about 1,000 °C.

In some embodiments, the catalytic composition may further comprise a rare earth element. In one embodiment, the rare earth element is selected from the group consisting of cerium, lanthanum, praseodymium, neodymium, and mixtures thereof.

In a further aspect, embodiments of the invention are directed a catalytic converter comprising the catalyst composition of any one or more of the twelve preceding paragraphs. Aspects of the invention may also be directed to a method of preparing a catalyst composition, comprising the steps of: forming a slurry comprising copper manganese, an aliovalent dopant element, and a support oxide; depositing the slurry onto a substrate; calcining the deposited slurry to form a catalytic composition having the formula: CuMm-yXyCn, wherein X is an aliovalent dopant element that is a cation not easily reducible, and y is a number from 0.01 to 1.99. In one embodiment, the aliovalent dopant element is selected from the group consisting of nickel, titanium, aluminum, magnesium, cobalt, barium, lanthanum, cadmium, tin, yttrium, zirconium and combinations thereof.

In one embodiment, the method includes calcining the slurry at a temperature above about 800 °C, when a loading of the ternary spinel in the catalyst composition is from about 5 to about 10 weight percent, based on the total weight of the composition.

In another embodiment, the method includes calcining the slurry at a temperature from about 600 to about 1,000 °C, when a loading of the ternary spinel in the catalyst composition is from about 12 to about 18 weight percent, based on the total weight of the composition.

Numerous other aspects, features and benefits of the present disclosure may be made apparent from the following detailed description taken together with the drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure can be better understood by referring to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the disclosure. In the figures, reference numerals designate corresponding parts throughout the different views. FIG. 1 is a graphical representation illustrating oxidation states of Cu within Cu- Mn binary and Cu-Mn-X ternary spinels employing an X-ray Photoelectron Spectroscopy (XPS) analysis, according to an embodiment.

FIG. 2 is a graphical representation illustrating concentrations of Cu¹⁺ formation as a function of the B-site aliovalent dopant (X) concentration within the Cu-Mn-X ternary spinels employing an XPS analysis, according to an embodiment.

FIG. 3 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.55% 0₂) to stoichiometric (about 0.49% O2) conditions for aged CuMn2-_yX_y04 ternary spinels as well as for a PGM reference catalyst, according to an embodiment.

FIG. 4 is a graphical representation illustrating a correlation between NOx conversions at stoichiometric condition (about 0.49% O2) and concentration of Cu¹⁺ within the CuMn2-_yX_y04 ternary spinels as the aliovalent dopant molar ratio (y) increases, according to an embodiment. FIG. 5 is a graphical representation illustrating an X-ray diffraction (XRD) phase purity analysis of a Cu-Mn spinel, calcined at different temperatures, according to an embodiment.

FIG. 6 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.56% O2) to stoichiometric (about 0.49% O2) conditions for an aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% and calcined at different temperatures, as well as for an aged PGM reference catalyst, according to an embodiment.

FIG. 7 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.56% O2) to stoichiometric (about 0.49% O2) conditions for an aged Cu-Mn-X ternary spinel employing a spinel loading of about 12 wt% and calcined at different temperatures, as well as for an aged PGM reference catalyst, according to an embodiment.

FIG. 8 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.56% O2) to stoichiometric (about 0.49% 0₂) conditions for an aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% and calcined at different temperatures, as well as for an aged PGM reference catalyst, according to an embodiment.

FIG. 9 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.56% O2) to stoichiometric (about 0.49% O2) conditions for aged Cu-Mn-X ternary spinels employing different spinel loadings (e.g., 6 wt% to 18 wt%) and calcined at about 600 °C, as well as for an aged PGM reference catalyst, according to an embodiment.

FIG. 10 is a graphical representation illustrating TWC steady- state sweep test results comparing NO conversions from lean (about 0.56% O2) to stoichiometric (about 0.49% O2) conditions for aged Cu-Mn-X ternary spinels with different spinel loadings (e.g., 6 wt% to 18 wt%) and calcined at about 900 °C, as well as for an aged PGM reference catalyst, according to an embodiment.

FIG. 11 is a graphical representation illustrating TWC steady- state sweep test results comparing NO conversions from lean (about 0.56% O2) to stoichiometric (about 0.49% O2) conditions for aged Cu-Mn-X ternary spinels with different spinel loadings (e.g., 6 wt% to 18 wt%) and calcined at about 1000 °C, as well as for an aged PGM reference catalyst, according to an embodiment.

FIG. 12 is a graphical representation illustrating TWC oxygen storage capacity (OSC) isothermal oscillating test results of O2 delay times for aged Cu-Mn-X spinels with different spinel loadings (e.g., 6 wt% to 18 wt%), at about 575 °C, according to an embodiment.

FIG. 13 is a graphical representation illustrating TWC OSC isothermal oscillating test results of O2 delay times for an aged Cu-Mn-X spinel employing a spinel loading of about 6 wt% as well as for an aged Cu-Mn-X spinel including Ce and employing a spinel loading of about 6 wt%, at about 575 °C, according to an embodiment.

FIG. 14 is a graphical representation illustrating TWC steady- state sweep test results comparing NO conversions from lean (about 0.56% O2) to stoichiometric (about 0.49% O2) conditions for an aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt%, an aged Cu-Mn-X ternary spinel including Ce and employing a spinel loading of about 6 wt%, and an aged PGM reference catalyst, according to an embodiment.

DETAILED DESCRIPTION

The present disclosure is here described in detail with reference to embodiments illustrated in the drawings, which form a part here. Other embodiments may be used and/or other changes may be made without departing from the spirit or scope of the present disclosure. The illustrative embodiments described in the detailed description are not meant to be limiting of the subject matter presented here.

Definitions

As used here, the following terms have the following definitions:

"Calcination" refers to a thermal treatment process applied to solid materials, in presence of air, to bring about a thermal decomposition, phase transition, or removal of a volatile fraction at temperatures below the melting point of the solid materials.

"Catalyst" refers to one or more materials that may be of use in the conversion of one or more other materials.

"Conversion" refers to the chemical alteration of at least one material into one or more other materials.

"Incipient wetness (IW)" refers to the process of adding solution of catalytic material to a dry support oxide powder until all pore volume of support oxide is filled out with solution and mixture goes slightly near saturation point.

"Platinum Group Metals (PGM)" refers to platinum, palladium, ruthenium, iridium, osmium, and rhodium.

"R-value" refers to the value obtained by dividing the reductant components to oxidant components within a gas flow. R-value greater than 1.0 refers to rich conditions. R-value less than about 1.0 refers to lean conditions. R-value equal to about 1.0 refers to stoichiometric condition. "Spinel" refers to any minerals of the general formulation AB2O4 where the A ion and B ion are each selected from mineral oxides, such as, for example magnesium, iron, zinc, manganese, aluminum, chromium, cobalt, titanium, nickel, or copper, among others.

"Three-way catalyst (TWC)" refers to a catalyst that performs the three simultaneous tasks of reduction of nitrogen oxides, oxidation of carbon monoxide, and oxidation of unburnt hydrocarbons.

"X-ray diffraction (XRD) analysis" refers to an analytical technique for identifying the phase purity and structure of crystalline materials, including atomic arrangement, crystallite size, and identification of crystal structure of unknown materials (e.g., minerals, inorganic compounds).

"X-ray Photoelectron Spectroscopy (XPS) analysis" refers to a surface- sensitive quantitative spectroscopy technique that measures the elemental composition at the parts per thousand range, empirical formula, chemical state, and electronic state of the elements that exist within a material.

Description of the Disclosure

The present disclosure describes multiple approaches for improving stoichiometric conversion of zero-platinum group metals (ZPGM) material compositions comprising binary and ternary spinel oxides. Further, the ZPGM catalysts exhibit improvements in stoichiometric catalytic conversion of a ternary spinel produced using aliovalent doping, by changing the catalyst loading concentration deposited onto a support oxide, by changing the calcination temperature, and by improving oxygen storage capacity (OSC). These ZPGM compositions with improved stoichiometric conversion can be employed for a variety of catalyst applications, such as, for example oxygen storage material (OSM) applications, and ZPGM and synergized-PGM (SPGM) three-way catalyst (TWC) systems, amongst others.

ZPGM catalyst material composition and preparation

In some embodiments, the ZPGM catalyst materials include binary spinel oxide compositions, which are synthesized using conventional synthesis methodologies. In these embodiments, the binary spinel oxide compositions are implemented as copper (Cu)- manganese (Mn) spinel oxide compositions. Further to these embodiments, the Cu-Mn spinel oxides are produced using a general formulation Cu_xMn3-_x04 in which x is a variable representing molar ratios within a range from about 0.01 to about 2.99. In an example, x takes a value of about 1.0 for a CuMn₂0₄ spinel oxide composition.

In other embodiments, the ZPGM catalyst materials include ternary spinel oxide compositions, which are synthesized using conventional synthesis methodologies. In these embodiments, the ternary spinel oxide compositions are implemented as a partial substitution within the B-site cation of a CuMn₂0₄ binary spinel employing a general formulation CuMm-yXyCn. Further to these embodiments, y is a variable representing different molar ratios and X is an aliovalent dopant element. Still further to these embodiments, X is selected to a cation that is not easily reducible, such as, for example nickel, aluminum, titanium, magnesium, cobalt, barium, lanthanum, cadmium, tin, yttrium, and zirconium, amongst others. In an example, X is implemented as nickel (Ni). In this example, y takes a value from about 0 to about 2.0 for a variety of Cu-Mn-X ternary spinel oxide compositions. In these embodiments, Cu within CuMm-yXyCn is present in one or more of a Cu⁺¹ state and a Cu⁺² state, and the prevalence of a Cu⁺¹ state is associated with an increasing aliovalent dopant molar ratio (y) value, for example, an increase in the amount of the dopant element (e.g., Ni, Al, Ti, and Zr) within the Cu-Mn spinel (see FIG. 2 and associated discussion, below).

In further embodiments, the Cu-Mn binary and Cu-Mn-X ternary spinels are deposited onto support oxides. Examples of support oxides are AI2O3, doped AI2O3, ZrC , doped ZrC"2, S1O2, doped S1O2, T1O2, doped T1O2, AhC -ZrC , doped AhC -ZrC , or mixtures thereof, amongst others. Further, doping materials within doped support oxides include Ca, Sr, Ba, Y, La, Ce, Nd, Pr, Nb, Si, or Ta oxides, amongst others.

Functional testing and characterization of Cu-Mn binary and Cu-Mn-X ternary spinels

In some embodiments, oxidation states of Cu within the Cu-Mn binary and Cu- Mn-X ternary spinels are analyzed employing X-ray photoelectron spectroscopy (XPS) analysis. In these embodiments, the concentration of Cu¹⁺ as a function of the B-site aliovalent dopant (X) within the Cu-Mn binary spinel is determined. In some embodiments, the Cu-Mn binary and Cu-Mn-X ternary spinels as well as a

PGM reference catalyst are aged at a temperature of about 800 °C for about 10 hours employing a rich- lean mode aging protocol. In other embodiments, the aged Cu-Mn binary and Cu-Mn-X ternary spinels as well as an aged PGM reference catalyst are tested employing a TWC isothermal steady-state sweep testing from lean to rich conditions.

In further embodiments, the oxygen storage capacity (OSC) of the ZPGM catalyst compositions are tested by employing a TWC isothermal oscillating test. In these embodiments, the ZPGM catalyst compositions further comprise a rare earth element. Further to these embodiments, the rare earth element is selected from the group consisting of cerium, lanthanum, praseodymium, neodymium, and mixtures thereof. Still further to these embodiments, the rare earth element loading ranges from about 1 g/L to about 20 g/L. In an example, the rare earth element is implemented as cerium (Ce) having a loading of 2 g/L. In some embodiments, the PGM reference catalyst includes palladium (Pd) having a loading concentration of about 20 g/ft³.

Improving stoichiometric conversion by aliovalent doping

FIG. 1 is a graphical representation illustrating oxidation states of Cu within Cu- Mn binary and Cu-Mn-X ternary spinels employing an X-ray Photoelectron Spectroscopy (XPS) analysis, according to an embodiment. In FIG. 1, XPS analysis 100 includes XPS raw data 110 and de-convoluted Cu2p peaks 120. XPS raw data 110 further includes XPS spectrum 112, XPS spectrum 114, XPS spectrum 116, and Cu⁺¹ peaks 118. De-convoluted Cu2p peaks 120 further includes de-convoluted Cu Peaks 122, de-convoluted Cu Peaks 128, and de-convoluted Cu Peaks 130, where de-convoluted Cu Peaks 128 and de- convoluted Cu Peaks 130 each include associated Cu⁺¹ Peaks 124 and Cu⁺² Peaks 126.

In some embodiments and referring to XPS raw data 110, XPS spectrum 112 illustrates a spectrum associated with CuMn₂04 binary spinel powder. In these embodiments, XPS spectrum 114 illustrates a spectrum associated with CuMn1.5X0.5O4 ternary spinel powder. Further to these embodiments, XPS spectrum 116 illustrates a spectrum associated with CuMno.5X1.5O4 ternary spinel powder. In these embodiments and referring to de-convoluted Cu2p peaks 120, de-convoluted Cu Peaks 122 illustrates Cu⁺¹ Peaks 124 and Cu⁺² Peaks 126 associated with CuMn₂04 binary spinel powder. Further to these embodiments, de-convoluted Cu Peaks 128 illustrates Cu⁺¹ Peaks 124 and Cu⁺² Peaks 126 associated with CuMn1.5X0.5O4 ternary spinel powder. Still further to these embodiments, de-convoluted Cu Peaks 130 illustrates Cu⁺¹ Peaks 124 and Cu⁺² Peaks 126 associated with CuMno.5X1.5O4 ternary spinel powder. In some embodiments, as the amount of dopant is increased from y = 0 within deconvolved Cu Peaks 122 to y = 1.5 within de-convo luted Cu Peaks 130, Cu⁺¹ Peaks 124 become more prominent when compared with Cu⁺² Peaks 126, thereby indicating as the aliovalent dopant (X) concentration increases the Cu is increasingly present as Cu⁺¹ (versus Cu⁺²) within Cu-Mn-X ternary spinels.

FIG. 2 is a graphical representation illustrating concentrations of Cu¹⁺ formation as a function of the B-site aliovalent dopant (X) concentration within the Cu-Mn-X ternary spinels employing an XPS analysis, according to an embodiment. In FIG. 2, XPS analysis 200 includes Cu⁺¹ XPS data trend 202. In some embodiments, Cu⁺¹ XPS data trend 202 illustrates the percentage (%) of

Cu⁺¹ formation within the CuMm-yXyCn ternary spinels (e.g., where X is Ni, Al, Ti, Zr, etc.) as a function of the aliovalent dopant (X) concentration. In these embodiments, XPS data indicates that as the concentration of aliovalent dopant (X) concentration increases, there is a corresponding %Cu⁺¹ formation increase. Comparison of TWC conversion vs. dopant concentration (X) within Cu-Mn-X ternary spinels

FIG. 3 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.55% 0₂) to stoichiometric (about 0.49% O2) conditions for aged CuMn2-_yX_y04 ternary spinels as well as for a PGM reference catalyst, according to an embodiment. In FIG. 3, NO conversion comparison graph 300 includes conversion curve 302, conversion curve 304, conversion curve 306, conversion curve 308, conversion curve 310, conversion curve 312, conversion curve 314, conversion curve 316, and conversion curve 318. In some embodiments, conversion curve 302 illustrates NO conversion associated with aged CuMm04 spinel (y = 0). In these embodiments, conversion curve 304 illustrates NO conversion associated with aged CuMn1.sX0.2O4 spinel (y = 0.2). Further to these embodiments, conversion curve 306 illustrates NO conversion associated with aged CuMn1.5X0.5O4 spinel (y = 0.5). Still further to these embodiments, conversion curve 308 illustrates NO conversion associated with aged CuMn1.25X0.75O4 spinel (y = 0.75). In these embodiments, conversion curve 310 illustrates NO conversion associated with aged CuMnX04 spinel (y = 1.0). Further to these embodiments, conversion curve 312 illustrates NO conversion associated with aged CuMno.75X1.25O4 spinel (y = 1.25). Still further to these embodiments, conversion curve 314 illustrates NO conversion associated with aged CuMno.25X1.75O4 spinel (y = 1.75). In these embodiments, conversion curve 316 illustrates NO conversion associated with aged CUX2O4 spinel (y = 2.0). Further to these embodiments, conversion curve 318 illustrates NO conversion associated with aged PGM reference catalyst.

In some embodiments and referring to FIG. 3, the associated conversion curves tend to exhibit a greater NOx conversion performance at both stoichiometric and lean conditions as aliovalent dopant molar ratio (y) within CuMn2-_yX_y04 increases. In these embodiments, the aged CUX2O4 (y = 2) spinel (conversion curve 316) exhibits the highest catalytic performance among the aged Cu-Mn-X spinels. Further to these embodiments, the aged PGM reference catalyst (conversion curve 318) exhibits improved NO conversion when compared with the NO conversions of aged Cu-Mn-X ternary spinels (conversion curves 302-316) at stoichiometric condition. FIG. 4 is a graphical representation illustrating a correlation between NOx conversions at stoichiometric condition (about 0.49% O2) and concentration of Cu¹⁺ within the CuMn2-_yX_y04 ternary spinels as the aliovalent dopant molar ratio (y) increases, according to an embodiment. In FIG. 4, correlation analysis 400 includes NO conversion data trend 402 and Cu⁺¹ XPS data trend 202 of FIG. 2, above. In FIG. 4, elements having substantially similar element numbers from previous figures function in a substantially similar manner.

In some embodiments, NO conversion data trend 402 illustrates NO conversion at stoichiometric condition (about 0.49% O2) as a function of the aliovalent dopant molar ratio (y) within the CuMn2-_yX_y04 ternary spinels. In these embodiments, correlation analysis indicate that there is a general improvement in NO conversion at stoichiometric condition as the aliovalent dopant molar ratio (y) increases within CuMn2-_yX_y04 from about 0 to about 2.0. Further to these embodiments, by increasing the ratio of the aliovalent dopant element (X) within CuMn2-_yX_y04 more Cu¹⁺ cations are formed, thereby exhibiting a higher stoichiometric NO conversion. In summary and referring to FIGS. 1-4, adding an aliovalent dopant element (X) increases the formation of Cu⁺¹ within the CuMn2-_yX_y04 ternary spinels. Further, the formation of Cu⁺¹ is critical for the stoichiometric conversion, as illustrated by XPS analysis and TWC steady-state sweep testing, as increases in the number of Cu⁺¹ contributes to increase NO conversion at stoichiometric conditions.

Improved stoichiometric conversion by modifying spinel loading and calcination Temperature

FIG. 5 is a graphical representation illustrating an X-ray diffraction (XRD) phase purity analysis of a Cu-Mn spinel, calcined a different temperatures, according to an embodiment. In FIG. 5, XRD analysis 500 includes XRD spectrum 502, XRD spectrum 504, spectral lines 506, and spectral lines 508. In some embodiments, XRD spectrum 502 illustrates diffraction peaks of bulk powder CuMn204 spinel calcined at a temperature of about 600 °C. In these embodiments, XRD spectrum 504 illustrates diffraction peaks of bulk powder CuMn204 spinel calcined at a temperature of about 1000 °C. Further to these embodiments and after calcination at about 600 °C, a spinel phase is produced, as illustrated by spectral lines 508. Still further to these embodiments, a secondary phase Mn₂03 is detected, as illustrated by spectral lines 506. In these embodiments and after calcination at about 1000 °C, pure spinel phase is produced, as illustrated by spectral lines 508, and the spinel includes no contaminant and no separate oxide phases (e.g., Mn oxide peaks). This result confirms that increasing calcination temperatures improves the Cu-Mn spinel phase purity. FIG. 6 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.56% 0₂) to stoichiometric (about 0.49% 0₂) conditions for an aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% and calcined at different temperatures, as well as for an aged PGM reference catalyst, according to an embodiment. In FIG. 6, NO conversion comparison graph 600 includes conversion curve 602, conversion curve 604, conversion curve 606, and conversion curve 608.

In some embodiments, conversion curve 602 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a loading of about 6 wt% on support oxide and calcined at about 600 °C. In these embodiments, conversion curve 604 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a loading of about 6 wt% on support oxide and calcined at about 900 °C. Further to these embodiments, conversion curve 606 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a loading of about 6 wt% on support oxide and calcined at about 1000 °C. Still further to these embodiments, conversion curve 608 illustrates NO conversion associated with aged PGM reference catalyst. In some embodiments and referring to FIG. 6, the associated conversion curves tend to exhibit a greater NOx performance at stoichiometric condition as calcination temperature increases due to the improvements in spinel phase purity. In these embodiments, the aged PGM reference catalyst (conversion curve 608) exhibits a greater NOx conversion when compared with the NO conversions of the aged Cu-Mn-X ternary spinel (conversion curves 602-606).

FIG. 7 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.56% 0₂) to stoichiometric (about 0.49% O2) conditions for an aged Cu-Mn-X ternary spinel employing a spinel loading of about 12 wt% and calcined at different temperatures, as well as for an aged PGM reference catalyst, according to an embodiment. In FIG. 7, NO conversion comparison graph 700 includes conversion curve 702, conversion curve 704, conversion curve 706, and conversion curve 708.

In some embodiments, conversion curve 702 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a loading of about 12 wt% on support oxide and calcined at about 600 °C. In these embodiments, conversion curve 704 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a loading of about 12 wt% on support oxide and calcined at about 900 °C. Further to these embodiments, conversion curve 706 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a loading of about 12 wt% on support oxide and calcined at about 1000 °C. Still further to these embodiments, conversion curve 708 illustrates NO conversion associated with aged PGM reference catalyst.

In some embodiments and referring to FIG. 7, the associated conversion curves tend to exhibit a greater NOx performance at stoichiometric condition as calcination temperature increases due to the improvements in spinel phase purity. In these embodiments, the aged PGM reference catalyst (conversion curve 708) exhibits a greater NO conversion when compared with the NO conversions of the aged Cu-Mn-X ternary spinel (conversion curves 702-706) at different calcination temperatures. Further to these embodiments, the catalytic behavior of the aged Cu-Mn-X ternary spinels calcined at about 900 °C (conversion curve 704) and about 1000 °C (conversion curve 706) is substantially similar within the whole range of % 0₂ values. FIG. 8 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.56% O2) to stoichiometric (about 0.49% O2) conditions for an aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% and calcined at different temperatures, as well as for an aged PGM reference catalyst, according to an embodiment. In FIG. 8, NO conversion comparison graph 800 includes conversion curve 802, conversion curve 804, conversion curve 806, and conversion curve 808.

In some embodiments, conversion curve 802 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide and calcined at about 600 °C. In these embodiments, conversion curve 804 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide and calcined at about 900 °C. Further to these embodiments, conversion curve 806 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide and calcined at about 1000 °C. Still further to these embodiments, conversion curve 808 illustrates NO conversion associated with aged PGM reference catalyst.

In some embodiments and referring to FIG. 8, the associated conversion curves tend to exhibit a greater NOx performance at stoichiometric condition as calcination temperature increases due to the improvements in spinel phase purity. In these embodiments, the aged PGM reference catalyst (conversion curve 808) exhibits a greater NO conversion when compared with the NO conversions of the aged Cu-Mn-X ternary spinel (conversion curves 802-806) at different calcination temperatures. Further to these embodiments, the catalytic behavior of the aged Cu-Mn-X ternary spinels calcined at about 900 °C (conversion curve 804) and about 1000 °C (conversion curve 806) is substantially similar within the whole range of % O2 values. In summary and referring to FIGS. 6-8, increasing calcination temperature enables to improve the catalytic performance at stoichiometric condition, which is valid for the different spinel loadings employed herein. Further, the Cu-Mn-X ternary spinel employing a spinel loading of about 12 wt% and calcined at about 1000 °C (see FIG. 7) exhibits improved stoichiometric NOx conversion, thereby narrowing the gap with the PGM reference catalyst. FIG. 9 is a graphical representation illustrating TWC steady-state sweep test results comparing NO conversions from lean (about 0.56% 0₂) to stoichiometric (about 0.49% O2) conditions for aged Cu-Mn-X ternary spinels employing different spinel loadings (e.g., 6 wt% to 18 wt%) and calcined at about 600 °C, as well as for an aged PGM reference catalyst, according to an embodiment. In FIG. 9, NO conversion comparison graph 900 includes conversion curve 902, conversion curve 904, conversion curve 906, and conversion curve 908.

In some embodiments, conversion curve 902 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide and calcined at about 600 °C. In these embodiments, conversion curve 904 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 12 wt% on support oxide and calcined at about 600 °C. Further to these embodiments, conversion curve 906 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide and calcined at about 600 °C. Still further to these embodiments, conversion curve 908 illustrates NO conversion associated with aged PGM reference catalyst.

In some embodiments and referring to FIG. 9, the aged Cu-Mn-X spinel employing a spinel loading of about 12 wt% on support oxide (conversion curve 904) exhibits the most favorable overall catalytic performance at stoichiometric condition when compared with the aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% (conversion curve 902) and the aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide (conversion curve 906). In these embodiments, the aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% (conversion curve 902) exhibits significantly less NO conversion because of the very low amount of active material (about 6 wt% spinel). Further to these embodiments, the aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% (conversion curve 906) indicates that the amount of Cu-Mn spinel within the catalyst material is large enough to cause less dispersion, e.g., forming clusters of active material on the catalyst support. In these embodiments and at about 600 °C, the aged PGM reference catalyst (conversion curve 908) exhibits a greater NO conversion when compared with the NO conversions of the aged Cu-Mn-X ternary spinel (conversion curves 902-906) at different spinel loadings.

FIG. 10 is a graphical representation illustrating TWC steady- state sweep test results comparing NO conversions from lean (about 0.56% 0₂) to stoichiometric (about 0.49% O2) conditions for aged Cu-Mn-X ternary spinels with different spinel loadings (e.g., 6 wt% to 18 wt%) and calcined at about 900 °C, as well as for an aged PGM reference catalyst, according to an embodiment. In FIG. 10, NO conversion comparison graph 1000 includes conversion curve 1002, conversion curve 1004, conversion curve 1006, and conversion curve 1008.

In some embodiments, conversion curve 1002 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide and calcined at about 900 °C. In these embodiments, conversion curve 1004 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 12 wt% on support oxide and calcined at about 900 °C. Further to these embodiments, conversion curve 1006 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide and calcined at about 900 °C. Still further to these embodiments, conversion curve 1008 illustrates NO conversion associated with aged PGM reference catalyst. In some embodiments and referring to FIG. 10, the aged Cu-Mn-X spinel employing a spinel loading of about 12 wt% on support oxide (conversion curve 1004) exhibits the most favorable overall catalytic performance at stoichiometric condition when compared with the aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide (conversion curve 1002) and the aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide (conversion curve 1006). In these embodiments, the aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide (conversion curve 1002) exhibits significantly less NO conversion. Further to these embodiments, the aged Cu-Mn-X ternary spinels employing a spinel loading of about 12 wt% (conversion curve 1004) and about 18 wt% (conversion curve 1006) exhibit a substantially similar performance, thereby confirming that increasing the catalyst loading from about 12 wt% to about 18 wt% does not improve NOx conversion performance. In these embodiments and at about 900 °C, the aged PGM reference catalyst (conversion curve 1008) exhibits a greater NO conversion when compared with the NO conversions of the aged Cu-Mn-X ternary spinel (conversion curves 1002-1006) at different spinel loadings.

FIG. 11 is a graphical representation illustrating TWC steady- state sweep test results comparing NO conversions from lean (about 0.56% 0₂) to stoichiometric (about 0.49% O2) conditions for aged Cu-Mn-X ternary spinels with different spinel loadings (e.g., 6 wt% to 18 wt%) and calcined at about 1000 °C, as well as for an aged PGM reference catalyst, according to an embodiment. In FIG. 11, NO conversion comparison graph 1100 includes conversion curve 1102, conversion curve 1104, conversion curve 1106, and conversion curve 1108.

In some embodiments, conversion curve 1102 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide and calcined at about 1000 °C. In these embodiments, conversion curve 1104 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 12 wt% on support oxide and calcined at about 1000 °C. Further to these embodiments, conversion curve 1106 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide and calcined at about 1000 °C. Still further to these embodiments, conversion curve 1108 illustrates NO conversion associated with aged PGM reference catalyst. In some embodiments and referring to FIG. 11, the aged Cu-Mn-X spinel employing a spinel loading of about 12 wt% on support oxide (conversion curve 1104) exhibits the most favorable overall catalytic performance at stoichiometric condition when compared with the aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide (conversion curve 1102) and the aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide (conversion curve 1106). In these embodiments, the aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% (conversion curve 1102) exhibits significantly less NO conversion because of the low amount of active material (e.g., spinel) present within the catalyst. Further to these embodiments, the aged Cu-Mn-X ternary spinels employing a spinel loading of about 12 wt% (conversion curve 1104) and about 18 wt% (conversion curve 1106) exhibit a substantially similar catalytic performance, thereby confirming that increasing the spinel loading from about 12 wt% to about 18 wt% does not improve NOx conversion performance.

In summary and referring to FIGS. 9-11, the aged Cu-Mn-X ternary spinel employing a spinel loading of about 12 wt% on support oxide is the optimum loading and exhibits improved catalytic performance (NO conversion) at stoichiometric condition from about 600 °C to about 1000 °C. Further, increasing calcination temperature results in higher purity of spinel, thereby increasing the stoichiometric conversion. Additionally, increasing spinel loading from about 12 wt% to about 18 wt% reduces the catalytic performance, which may be caused by a decrease in dispersion. Improved stoichiometric conversion by modifying the OSC of the spinel

FIG. 12 is a graphical representation illustrating TWC oxygen storage capacity (OSC) isothermal oscillating test results of 0₂ delay times for aged Cu-Mn-X spinels with different spinel loadings (e.g., 6 wt% to 18 wt%), at about 575 °C, according to an embodiment. In FIG. 12, OSC test results 1200 includes O2 delay time bar 1202, O2 delay time bar 1204, and O2 delay time bar 1206.

In some embodiments, O2 delay time bar 1202 illustrates the O2 delay time associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide. In these embodiments, O2 delay time bar 1204 illustrates the O2 delay time associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 12 wt% on support oxide. Further to these embodiments, O2 delay time bar 1206 illustrates the O2 delay time associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% on support oxide.

In some embodiments, as the Cu-Mn loading is increased there is a corresponding increase in O2 delay time and hence OSC. In these embodiments, the aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% (O2 delay time bar 1202) exhibits a significantly lower O2 delay time (about 18 seconds) when compared with the aged Cu-Mn-X ternary spinel employing a spinel loading of about 12 wt% (O2 delay time bar 1204, about 54 seconds) and the aged Cu-Mn-X ternary spinel employing a spinel loading of about 18 wt% (O2 delay time bar 1206, about 65 seconds), thereby indicating that there are diminishing returns as loading is increased above a threshold. Further to these embodiments, spinel loadings greater than about 12 wt% may cause less dispersion of the Cu-Mn-X ternary spinel. Still further to these embodiments, the spinel loading of about 12 wt% is the optimum loading, thereby exhibiting improved dispersion and OSC.

FIG. 13 is a graphical representation illustrating TWC OSC isothermal oscillating test results of 0₂ delay times for an aged Cu-Mn-X spinel employing a spinel loading of about 6 wt% as well as for an aged Cu-Mn-X spinel including Ce and employing a spinel loading of about 6 wt%, at about 575 °C, according to an embodiment. In FIG. 13, OSC test results 1300 includes O2 delay time bar 1302 and O2 delay time bar 1304.

In some embodiments, O2 delay time bar 1302 illustrates the O2 delay time associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide. In these embodiments, O2 delay time bar 1304 illustrates the O2 delay time associated with aged Cu-Mn-X ternary spinel including Ce and employing a spinel loading of about 6 wt% on support oxide. Further to these embodiments, Ce is added to a Cu-Mn-X ternary spinel during preparation by adding cerium nitrate at a loading concentration of about 2 g/L. Still further to these embodiments, the addition of ceria to Cu-Mn-X spinel, results in an increase in O2 delay time and hence OSC. In this embodiments, the aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% exhibits an O2 delay time of about 18 seconds, whereas the aged Cu-Mn-X ternary spinel including Ce and employing a spinel loading of about 6 wt% exhibits an O2 delay time of about 28 seconds. FIG. 14 is a graphical representation illustrating TWC steady- state sweep test results comparing NO conversions from lean (about 0.56% O2) to stoichiometric (about 0.49% O2) conditions for an aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt%, an aged Cu-Mn-X ternary spinel including Ce and employing a spinel loading of about 6 wt%, and an aged PGM reference catalyst, according to an embodiment. In FIG. 14, NO conversion comparison graph 1400 includes conversion curve 1402, conversion curve 1404, and conversion curve 1406.

In some embodiments, conversion curve 1402 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide. In these embodiments, conversion curve 1404 illustrates NO conversion associated with aged Cu-Mn-X ternary spinel including Ce (2 g/L) and employing a spinel loading of about 6 wt% on support oxide. Further to these embodiments, conversion curve 1406 illustrates NO conversion associated with aged PGM reference catalyst.

In some embodiments, the aged Cu-Mn-X ternary spinel including Ce (2 g/L) and employing a spinel loading of about 6 wt% on support oxide (conversion curve 1404) exhibits a higher catalytic performance at stoichiometric and lean conditions when compared with aged Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% on support oxide (conversion curve 1402), thereby indicating an improvement associated with the inclusion of ceria within the Cu-Mn-X ternary spinel. In these embodiments, by adding small amount of Ce within the Cu-Mn-X ternary spinel employing a spinel loading of about 6 wt% results in improved NO conversion at stoichiometric condition from about 80.40% to about 92.40%, which is attributed to the improved OSC of the ternary spinel.

In summary, the conversion performance of a Cu-Mn-X ternary spinel is improved by increasing the concentration of Cu⁺¹ by means of aliovalent doping, improving the phase purity of spinel by calcining at higher temperatures, varying loading concentration of ternary spinel catalyst deposited onto support oxides, and increasing the OSC by adding rare-earth metals. Overall, increasing the ratio of aliovalent dopant elements causes increase in the formation of Cu⁺¹ that results in improvements of the catalytic activity at stoichiometric condition. Further, an increase in calcination temperature results in a high spinel phase purity thereby increasing the catalytic performance at stoichiometric condition. Additionally, the optimum loading of spinel impact the OSC and dispersion of the spinel that results in improvements in catalytic activity at stoichiometric condition. The increase in OSC of the spinel is another factor that improves the stoichiometric conversion. All these factors exhibit improved stoichiometric conversion and narrowing the gap between ZPGM and PGM catalytic performance at stoichiometric condition. While various aspects and embodiments have been disclosed, other aspects, and embodiments may be contemplated. The various aspects and embodiments disclosed here are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

CLAIMS What is claimed is:

1. A catalytic composition comprising a ternary spinel having the formula: CuMn2-yX_y04, wherein X is an aliovalent dopant element that is a cation not easily reducible, and y is a number from 0.01 to 1.99.

2. The catalytic composition of claim 1, wherein y is a number ranging from 0.05 to 1.9.

3. The catalytic composition of claim 1, wherein y is a number ranging from 0.1 to 1.9.

4. The catalytic composition of claim 1, wherein y is a number ranging from

0.2 to 1.9.

5. The catalytic composition of claim 1, wherein y is a number ranging from 0.3 to 1.9.

6. The catalytic composition of claim 1, wherein y is a number ranging from 0.4 to 1.9.

7. The catalytic composition of claim 1, wherein y is a number ranging from 0.5 to 1.9.

8. The catalytic composition of claim 1, wherein y is a number ranging from 0.6 to 1.9. 9. The catalytic composition of claim 1, wherein y is a number ranging from

0.7 to 1.

9.

10. The catalytic composition of claim 1, wherein y is a number ranging from 0.8 to 1.9.

11. The catalytic composition of claim 1, wherein y is a number ranging from 0.9 to 1.9.

12. The catalytic composition of claim 1, wherein y is a number ranging from 1.0 to 1.9.

13. The catalytic composition of claim 1, wherein y is a number ranging from

1.1 to 1.9.

14. The catalytic composition of claim 1, wherein y is a number ranging from

1.2 to 1.9.

15. The catalytic composition of claim 1, wherein y is a number ranging from

1.3 to 1.9.

16. The catalytic composition of claim 1, wherein y is a number ranging from

1.4 to 1.9.

17. The catalytic composition of claim 1, wherein y is a number ranging from 1.5 to 1.9.

18. The catalytic composition of claim 1, wherein y is a number less than 2.0 and greater than 1.0.

19. The catalytic composition of claim 1, wherein y is a number ranging from 1.4 to 1.8.

20. The catalytic composition of any one or more of the preceding claims, wherein X is selected from the group consisting of nickel, titanium, aluminum, magnesium, cobalt, barium, lanthanum, cadmium, tin, yttrium, zirconium, and combinations thereof.

21. The catalytic composition of any one or more of the preceding claims, wherein an atomic percent of Cu⁺¹ in the spinel is from about 10 to about 500% greater than an atomic percent of Cu⁺² in the spinel.

22. The catalytic composition of any one or more of the preceding claims, wherein an atomic percent of Cu⁺¹ in the spinel is from about 50 to about 500% greater than an atomic percent of Cu⁺² in the spinel.

23. The catalytic composition of any one or more of the preceding claims, wherein an atomic percent of Cu⁺¹ in the spinel is from about 100 to about 500% greater than an atomic percent of Cu⁺² in the spinel.

24. The catalytic composition of any one or more of the preceding claims, wherein the composition further includes a support oxide on which the ternary spinel is deposited.

25. The catalytic composition of claim 24, wherein the support oxide is selected from the group consisting of AI2O3, doped AI2O3, Zr0₂, doped Zr0₂, S1O2, doped

S1O2, T1O2, doped T1O2, Al₂03-Zr0₂, doped Al₂03-Zr0₂, and mixtures thereof.

26. The catalytic composition of claim 24, wherein the dopant in the support oxide is selected from the group consisting of calcium, strontium, barium, yttrium, lanthanum, cerium, neodymium, praseodymium, niobium, silicon, tantalum, and combinations thereof.

27. The catalytic composition of any one of claims 24 to 26, wherein the composition has a loading of the ternary spinel that is from about 5 to about 20 weight percent, based on the total weight of the composition.

28. The catalytic composition of any one of claims 24 to 26, wherein the composition has been calcined at a temperature from about 500 °C to about 800 °C, and has a loading of the ternary spinel that is from about 10 to about 20 weight percent, based on the total weight of the composition.

29. The catalytic composition of claim 28, wherein the composition has been calcined at a temperature of about 600 °C, and has a loading of the ternary spinel that is from about 12 to about 18 weight percent, based on the total weight of the composition.

30. The catalytic composition of any one of claims 24 to 26, wherein the composition has been calcined at a temperature from about 800 °C to 1,000 °C, and has a loading of the ternary spinel that is from about 5 to 20 weight percent, based on the total weight of the composition.

31. The catalytic composition of claim 30, wherein the composition has been calcined at a temperature of about 900 °C, and has a loading of the ternary spinel that is from about 5 to 20 weight percent, based on the total weight of the composition.

32. The catalytic composition of claim 30, wherein the composition has been calcined at a temperature of about 900 °C, and has a loading of the ternary spinel that is from about 6 to about 18 weight percent, based on the total weight of the composition.

33. The catalytic composition of claim 30, wherein the composition has been calcined at a temperature of about 900 °C, and has a loading of the ternary spinel that is about 12 weight percent, based on the total weight of the composition.

34. The catalytic composition of claim 30, wherein the composition has been calcined at a temperature of about 1,000 °C, and has a loading of the ternary spinel that is from about 5 to about 20 weight percent, based on the total weight of the composition.

35. The catalytic composition of claim 30, wherein the composition has been calcined at a temperature of about 1,000 °C, and has a loading of the ternary spinel that is from about 6 to about 18 weight percent, based on the total weight of the composition.

36. The catalytic composition of claim 30, wherein the composition has been calcined at a temperature of about 1,000 °C, and has a loading of the ternary spinel that is from about 12 to about 18 weight percent, based on the total weight of the composition.

37. The catalytic composition of any one of claims 24 to 26, wherein:

i) the composition has a loading of the ternary spinel that is from about 10 to about 20 weight percent, based on the total weight of the composition, and the composition has been calcined at a temperature from about 600 °C to about 1,000 °C; or

ii) the composition has a loading of the ternary spinel that is from about 5 to about 10 weight percent, based on the total weight of the composition, and the composition has been calcined at a temperature from about 800 °C to about 1,000 °C.

38. The catalytic composition according to any one or more of the preceding claims, further comprising a rare earth element.

39. The catalytic composition according to claim 38, wherein the rare earth element is selected from the group consisting of cerium, lanthanum, praseodymium, neodymium, and combinations thereof.

40. A catalytic converter comprising the catalyst composition of any one or more of the preceding claims.

41. A method of preparing a catalyst composition, comprising the steps of: forming a slurry comprising copper manganese, an aliovalent dopant element, and a support oxide;

depositing the slurry onto a substrate;

calcining the deposited slurry to form a catalytic composition having the formula: CuMm-yXyCn, wherein X is an aliovalent dopant element that is a cation not easily reducible, and y is a number from 0.01 to 1.99.

42. The method of claim 41, wherein the slurry is calcined at a temperature above about 800 °C, and a loading of the ternary spinel in the catalyst composition is from about 5 to about 10 weight percent, based on the total weight of the composition.

43. The method of claim 41, wherein the slurry is calcined at a temperature from about 600 to about 1,000 °C, and a loading of the ternary spinel in the catalyst composition is from about 12 to about 18 weight percent, based on the total weight of the composition.

44. The method of claim 41, wherein the aliovalent dopant element is selected from the group consisting of nickel, titanium, aluminum, magnesium, cobalt, barium, lanthanum, cadmium, tin, yttrium, zirconium, and combinations thereof.