Enhanced catalytic activity at the stoichiometric condition of zero-PGM catalysts for TWC applications

Abstract

The present disclosure relates to zero-PGM (ZPGM) catalysts including variations of Nickel-doped Copper-Manganese spinel for improved catalyst performance at the stoichiometric condition for use within three-way catalyst (TWC) applications. The ZPGM catalyst material compositions within the aforementioned ZPGM catalysts are expressed with general formulas of Cu.sub.1-XNi.sub.XMn.sub.2O.sub.4 (A-site substitution) and Cu.sub.1Mn.sub.2-XNi.sub.XO.sub.4 (B-site substitution). The ZPGM catalysts are subjected to a TWC isothermal steady-state sweep test to assess the catalytic performance (e.g., NO conversion). Test results indicate the ZPGM catalysts exhibit higher NO conversions, at stoichiometric condition and lean conditions, when Ni substituted the B-site cation of the CuMn spinel as compared to Ni substituted the A-site cation of the CuMn spinel. Additionally, NO conversions of the ZPGM catalysts are significantly affected, at the stoichiometric condition, by the molar ratio of the Ni dopant within the A or B-site cation of the CuMn spinel.

Claims

1. A catalyst comprising: a substrate; a washcoat layer overlying the substrate, the washcoat layer comprising a support oxide; and an impregnation layer overlying the washcoat layer, the impregnation layer comprising a doped binary spinel having the formula CuMn.sub.2-xNi.sub.xO.sub.4 wherein x is a number from 0.01 to 1.99.

2. The catalyst of claim 1, wherein x is a number ranging from 0.2 to 1.8, from 0.2 to 1.5, from 0.2 to 1.25, from 0.2 to 1.0, from 0.2 to 0.75, from 0.2 to 0.5, from 0.5 to 1.8, from 0.5 to 1.5, ranging from 0.5 to 1.25, from 0.5 to 1.0, from 0.5 to 0.75, from 0.75 to 1.8, from 0.75 to 1.5, from 0.75 to 1.25, from 0.75 to 1.0, from 1.0 to 1.8, from 1.0 to 1.5, or from 1.0 to 1.25.

3. The catalyst of claim 1, wherein the support oxide is selected from the group consisting of Al.sub.2O.sub.3, doped Al.sub.2O.sub.3, ZrO.sub.2, doped ZrO.sub.2, SiO.sub.2, doped SiO.sub.2, TiO.sub.2, doped TiO.sub.2, Al.sub.2O.sub.3ZrO.sub.2, doped Al.sub.2O.sub.3ZrO.sub.2, Nb.sub.2O.sub.5, doped Nb.sub.2O.sub.5, and mixtures thereof, and wherein the dopant in the support oxide, when present, is selected from the group consisting of calcium, strontium, barium, yttrium, lanthanum, cerium, neodymium, praseodymium, niobium, silicon, tantalum, and combinations thereof.

4. The catalyst of claim 1, wherein the washcoat layer comprises Nb-doped Al.sub.2O.sub.3ZrO.sub.2.

5. A catalyst comprising a substrate; a washcoat layer overlying the substrate, the washcoat layer comprising a support oxide; and an impregnation layer overlying the washcoat layer, the impregnation layer comprising a doped binary spinel having the formula Cu.sub.1-xNi.sub.xMn.sub.2O.sub.4 wherein x is a number from 0.01 to 0.99.

6. The catalyst of claim 5, wherein x is a number ranging from 0.01 to 0.70, from 0.01 to 0.5, from 0.01 to 0.2, from 0.01 to 0.1, from 0.1 to 0.7, from 0.1 to 0.5, from 0.1 to 0.2, from 0.2 to 0.7, or from 0.2 to 0.5.

7. The catalyst of claim 5, wherein the doped binary spinel further comprises an additional dopant selected from the group consisting of titanium, aluminum, magnesium, cobalt, barium, lanthanum, cadmium, tin, yttrium, zirconium, silver, iron, chromium, niobium, cerium, scandium, molybdenum, tungsten, and combinations thereof.

8. The catalyst of claim 5, wherein the support oxide is selected from the group consisting of Al.sub.2O.sub.3, doped Al.sub.2O.sub.3, ZrO.sub.2, doped ZrO.sub.2, SiO.sub.2, doped SiO.sub.2, TiO.sub.2, doped TiO.sub.2, Al.sub.2O.sub.3ZrO.sub.2, doped Al.sub.2O.sub.3ZrO.sub.2, Nb.sub.2O.sub.5, doped Nb.sub.2O.sub.5, and mixtures thereof, and wherein the dopant in the support oxide, when present, is selected from the group consisting of calcium, strontium, barium, yttrium, lanthanum, cerium, neodymium, praseodymium, niobium, silicon, tantalum, and combinations thereof.

9. The catalyst of claim 5, wherein the washcoat layer comprises Nb-doped Al.sub.2O.sub.3ZrO.sub.2.

10. The catalyst of claim 5, wherein the impregnation layer is deposited overlying the washcoat layer as a solution, and has been calcined at a temperature from about 600 C. to about 700 C.

11. The catalyst of claim 5, wherein the catalyst exhibits an NO percent conversion that is from about 25 to about 70%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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.

(2) FIG. 1 is a functional block diagram illustrating a catalyst configuration for zero-platinum group metals (ZPGM) catalysts, according to an embodiment.

(3) FIG. 2 is a graphical representation illustrating three-way catalyst (TWC) steady-state sweep test results comparing % NO conversions at specific % O.sub.2 values associated with aged ZPGM Type 1 catalysts employing various doping loadings of Ni within a B-site substitution of CuMn spinels, according to an embodiment.

(4) FIG. 3 is a graphical representation illustrating TWC steady-state sweep test results comparing % NO conversions at the stoichiometric condition (O.sub.2=0.49%) associated with aged ZPGM Type 1 catalysts employing various loadings of Ni within a B-site substitution of CuMn spinels, according to an embodiment.

(5) FIG. 4 is a graphical representation illustrating TWC steady-state sweep test results comparing % NO conversions at the stoichiometric condition (O.sub.2=0.49%) associated with aged ZPGM Type 2 catalysts employing various loadings of Ni within an A-site substitution of CuMn spinels, according to an embodiment.

(6) FIG. 5 is a graphical representation illustrating TWC steady-state sweep test results comparing % NO conversions at specific % O.sub.2 values associated with aforementioned aged ZPGM catalysts as well as a ZPGM reference catalyst, according to an embodiment.

DETAILED DESCRIPTION

(7) 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

(8) As used here, the following terms have the following definitions:

(9) 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.

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

(11) Impregnation refers to the process of imbuing or saturating a solid layer with a liquid compound or the diffusion of some element through a medium or substance.

(12) Platinum group metals (PGM) refers to platinum, palladium, ruthenium, iridium, osmium, and rhodium.

(13) R-value refers to the value obtained by dividing the reductant components to oxidant components within a gas flow. R-value greater than about 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.

(14) Spinel refers to any minerals of the general formulation AB.sub.2O.sub.4 where the A ion and B ion are each selected from mineral oxides, such as, for example magnesium, iron, zinc, manganese, aluminum, chromium, titanium, nickel, cobalt, or copper, amongst others.

(15) Stoichiometric condition refers to the condition when the oxygen of the combustion gas or air added equals the amount for completely combusting the fuel, an exhaust gas condition with an R-value equal to about 1.0.

(16) Substrate refers to any material of any shape or configuration that yields a sufficient surface area for depositing a washcoat layer and/or an overcoat layer.

(17) Support oxide refers to porous solid oxides, typically mixed metal oxides, which are used to provide a high surface area that aids in oxygen distribution, and exposure of catalysts to reactants, such as, for example NO.sub.X, CO, and hydrocarbons.

(18) 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.

(19) Washcoat (WC) layer refers to at least one coating including at least one oxide solid that is deposited on a substrate.

(20) Zero-platinum group metals (ZPGM) catalyst refers to a catalyst completely free of platinum group metals (PGM).

Description of the Disclosure

(21) The present disclosure is directed to zero-platinum group metals (ZPGM) catalysts, which are produced according to a catalyst configuration including a substrate, a washcoat (WC) layer, and an impregnation (IMP) layer. Further, the present disclosure describes a process for identifying suitable nickel (Ni) molar ratios employed as A or B-site cation dopants that are capable of providing improved chemical reactivity at the stoichiometric condition within a binary spinel composition to produce the aforementioned ZPGM catalysts. In some embodiments, variations in the Ni molar ratios exhibit significant effects on NO conversion activity of the ZPGM catalysts, and can be used to produce a plurality of improved catalysts for three-way catalyst (TWC) applications.

(22) ZPGM Catalyst Configuration, Material Composition, and Preparation

(23) FIG. 1 is a functional block diagram illustrating a catalyst configuration for zero-platinum group metals (ZPGM) catalysts, according to an embodiment. In FIG. 1, catalyst configuration 100 includes substrate 102, washcoat (WC) layer 104, and impregnation (IMP) layer 106. In some embodiments, WC layer 104 is coated onto substrate 102. In these embodiments, IMP layer 106 is impregnated onto WC layer 104. Further to these embodiments, the aforementioned layers within ZPGM catalysts are produced using any conventional synthesis methodologies. In an example, WC layer 104 is implemented as a support oxide. In this example, IMP layer 106 is implemented as a spinel composition.

(24) In some embodiments, WC layer 104 comprises support oxides. Examples of support oxides for use as WC layer 104 include alumina (Al.sub.2O.sub.3), doped Al.sub.2O.sub.3, zirconia (ZrO.sub.2), doped ZrO.sub.2, doped Al.sub.2O.sub.3ZrO.sub.2, CeO.sub.2, TiO.sub.2, Nb.sub.2O.sub.5, SiO.sub.2, or mixtures thereof, amongst others. Further, doping materials within doped support oxides include Ca, Sr, Ba, Y, La, Ce, Nd, Pr, Nb, or Ta oxides, amongst others. In an example, WC layer 104 is implemented as an Nb-doped Al.sub.2O.sub.3ZrO.sub.2 support oxide.

(25) In some embodiments, IMP layer 106 includes a plurality of ternary spinel compositions. In these embodiments, the IMP layer 106 includes copper (Cu) and manganese (Mn) doped with a third element (e.g., dopant element) within the spinel oxide structure. Examples of dopant elements suitable for CuMn spinel structures include aluminum (Al), magnesium (Mg), nickel (Ni), silver (Ag), cobalt (Co), iron (Fe), chromium (Cr), titanium (Ti), tin (Sn), niobium (Nb), cerium (Ce), scandium (Sc), molybdenum (Mo), tungsten (W), or mixtures thereof, amongst others.

(26) In an example, IMP layer 106 includes a Ni-doped CuMn spinel composition, where Ni partially substitutes the A-site cation of the CuMn spinel structure. In these embodiments, the Ni-doped CuMn spinel composition is produced using a general formula of Cu.sub.1-XNi.sub.XMn.sub.2O.sub.4 in which X is a variable representing different molar ratios within a range from about 0.01 to about 1.0.

(27) In another example, IMP layer 106 includes a Ni-doped CuMn spinel composition, where Ni partially substitutes the B-site cation of the CuMn spinel structure. In these embodiments, the Ni-doped CuMn spinel is produced using a general formula of Cu.sub.1Mn.sub.2-XNi.sub.XO.sub.4 in which X is a variable representing different molar ratios within a range from about 0.01 to about 2.0.

(28) In a further example, IMP layer 106 includes a CuMn spinel composition as reference catalytic material. In this example, the CuMn spinel composition is produced using a general formula Cu.sub.XMn.sub.3-XO.sub.4 in which X is a variable representing molar ratios within a range from about 0.01 to about 2.99. Further to this example, X takes a value of 1.0 to produce a Cu.sub.1Mn.sub.2O.sub.4 binary spinel composition.

(29) ZPGM Type 1 Catalysts: B-site Ni-doped CuMn Spinel Composition

(30) In some embodiments, a ZPGM catalyst, referred to as ZPGM Type 1 catalyst, includes WC layer 104 comprising an Nb-doped Al.sub.2O.sub.3ZrO.sub.2 support oxide that is deposited onto suitable 102. In these embodiments, IMP layer 106 comprises a Cu.sub.1Mn.sub.2-XNi.sub.XO.sub.4 spinel composition (B-site substitution) that is impregnated onto WC layer 104.

(31) In some embodiments, the preparation of WC layer 104 begins by milling the Nb-doped Al.sub.2O.sub.3ZrO.sub.2 support oxide with water to produce an aqueous slurry of Nb-doped Al.sub.2O.sub.3ZrO.sub.2. In these embodiments, the slurry of Nb-doped Al.sub.2O.sub.3ZrO.sub.2 is coated onto substrate 102, and further dried and calcined at about 550 C. for about 4 hours to produce WC layer 104.

(32) In some embodiments, the preparation of IMP layer 106 begins with mixing appropriate amounts of Mn nitrate solution, Ni nitrate solution, and Cu nitrate solution with water to produce a CuMnNi solution at an appropriate molar ratio to produce a catalyst composition expressed with a formula of Cu.sub.1Mn.sub.2-XNi.sub.XO.sub.4. In these embodiments, Ni partially substitutes the B-site cation of the CuMn spinel in a plurality of molar ratios (e.g., 0.0, 0.2, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, and 2.0). Further to these embodiments, the CuMnNi solution is then impregnated onto WC layer 104. In these embodiments, the impregnated CuMnNi material is calcined at a temperature of about 600 C. to 700 C. for about 6 hours to produce IMP layer 106 comprising the Cu.sub.1Mn.sub.2-XNi.sub.XO.sub.4 spinel composition (B-site substitution).

(33) Table 1.

(34) ZPGM Type 1 catalysts including IMP layers 106 comprising Cu.sub.1Mn.sub.2-XNi.sub.XO.sub.4 spinel compositions.

(35) TABLE-US-00001 Catalyst Ni loading Spinel composition Type 1A 0.20 Cu.sub.1Mn.sub.1.8Ni.sub.0.2O.sub.4 Type 1B 0.50 Cu.sub.1Mn.sub.1.5Ni.sub.0.5O.sub.4 Type 1C 0.75 Cu.sub.1Mn.sub.1.25Ni.sub.0.75O.sub.4 Type 1D 1.00 Cu.sub.1Mn.sub.1Ni.sub.1O.sub.4 Type 1E 1.25 Cu.sub.1Mn.sub.0.75Ni.sub.1.25O.sub.4 Type 1F 1.50 Cu.sub.1Mn.sub.0.5Ni.sub.1.5O.sub.4 Type 1G 1.75 Cu.sub.1Mn.sub.0.25Ni.sub.1.75O.sub.4 Type 1H 2.00 Cu.sub.1Ni.sub.2O.sub.4

(36) ZPGM Type 2 Catalysts: A-Site Ni-Doped CuMn Spinel Composition

(37) In some embodiments, a ZPGM catalyst, referred to as ZPGM Type 2 catalyst, includes WC layer 104 comprising an Nb-doped Al.sub.2O.sub.3ZrO.sub.2 support oxide that is deposited onto substrate 102. In these embodiments, IMP layer 106 comprises a Cu.sub.1-XNi.sub.XMn.sub.2O.sub.4 spinel composition (A-site substitution) that is impregnated onto WC layer 104.

(38) In some embodiments, the preparation of WC layer 104 begins by milling the Nb-doped Al.sub.2O.sub.3ZrO.sub.2 with water to produce aqueous slurry of Nb-doped Al.sub.2O.sub.3ZrO.sub.2. In these embodiments, the slurry of Nb-doped Al.sub.2O.sub.3ZrO.sub.2 is coated onto substrate 102, and further dried and calcined at about 550 C. for about 4 hours to produce WC layer 104.

(39) In some embodiments, the preparation of IMP layer 106 begins with mixing appropriate amounts of Mn nitrate solution, Ni nitrate solution, and Cu nitrate solution with water to produce a CuMnNi solution at an appropriate molar ratio to produce a catalyst composition expressed with a formula of Cu.sub.1-XNi.sub.XMn.sub.2O.sub.4. In these embodiments, Ni partially substitutes the A-site cation of the CuMn spinel in a plurality of molar ratios (e.g., 0.01, 0.02, 0.1, 0.2, 0.5, 0.7, and 1.0). Further to these embodiments, the CuMnNi solution is then impregnated onto WC layer 104. In these embodiments, the CuMnNi material is calcined at a temperature of about 600 C. to 700 C. for about 6 hours to produce IMP layer 106 comprising the Cu.sub.1-XNi.sub.XMn.sub.2O.sub.4 spinel composition (A-site substitution).

(40) Table 2.

(41) ZPGM Type 2 catalysts including IMP layers 106 comprising Cu.sub.1-XNi.sub.XMn.sub.2O.sub.4 spinel compositions.

(42) TABLE-US-00002 Catalyst Ni loading Spinel composition Type 2A 0.01 Cu.sub.0.99Ni.sub.0.01Mn.sub.2O.sub.4 Type 2B 0.02 Cu.sub.0.98Ni.sub.0.02Mn.sub.2O.sub.4 Type 2C 0.10 Cu.sub.0.9Ni.sub.0.1Mn.sub.2O.sub.4 Type 2D 0.20 Cu.sub.0.8Ni.sub.0.2Mn.sub.2O.sub.4 Type 2E 0.50 Cu.sub.0.5Ni.sub.0.5Mn.sub.2O.sub.4 Type 2F 0.70 Cu.sub.0.3Ni.sub.0.7Mn.sub.2O.sub.4

(43) ZPGM Reference Catalyst

(44) In some embodiments, a ZPGM reference catalyst includes WC layer 104 comprising an Nb-doped Al.sub.2O.sub.3ZrO.sub.2 support oxide that is deposited onto substrate 102. In these embodiments, IMP layer 106 comprises a Cu.sub.1Mn.sub.2O.sub.4 binary spinel composition that is impregnated onto WC layer 104.

(45) TWC Isothermal Steady-State Sweep Test Procedure

(46) In some embodiments, a TWC isothermal steady-state sweep test is performed employing a flow reactor at an inlet temperature of about 500 C. and using a gas stream having 11-point R-values from about 0.62 (lean condition) to about 2.28 (rich condition) to measure the CO, NO, and HC conversions. In these embodiments, the space velocity (SV) employed within the TWC isothermal steady-state sweep test is set at about 50,000 hr.sup.1. Further to these embodiments, the gas feed employed for the test is a standard TWC gas composition with variable O.sub.2 concentration to adjust R-values from lean conditions to rich conditions during testing. In these embodiments, the standard TWC gas composition includes about 8,000 ppm of CO, about 400 ppm of C.sub.3H.sub.6, about 100 ppm of C.sub.3H.sub.8, about 1,000 ppm of NO.sub.X, about 2,000 ppm of H.sub.2, about 10% of CO.sub.2, and about 10% of H.sub.2O. Further to these embodiments, the quantity of O.sub.2 within the gas mix is varied to regulate the O.sub.2 percentage within feed gas from about 0.2% to about 0.8%. In these embodiments, the stoichiometric condition is at an O.sub.2 percentage of about 0.49% (at an R-value of about 1.0).

(47) In some embodiments, the TWC isothermal steady-state sweep test is applied to ZPGM Type 1 catalysts and Type 2 catalysts to determine the NO conversion levels, after aging employing a multi-mode condition test at about 800 C. for about 10 hours.

(48) Catalytic Performance Analysis of the Aforementioned ZPGM Catalysts

(49) FIG. 2 is a graphical representation illustrating three-way catalyst (TWC) steady-state sweep test results comparing % NO conversions at specific % O.sub.2 values associated with aged ZPGM Type 1 catalysts employing various doping loadings of Ni within a B-site substitution of CuMn spinels, according to an embodiment. In FIG. 2, NO comparison graph 200 includes NO conversion curve 202 (solid bold line), NO conversion curve 204 (dot line), NO conversion curve 206 (dash line), conversion curve 208 (dot dash line), NO conversion curve 210 (dot dot dash line), and NO conversion curve 212 (solid line).

(50) In some embodiments, NO conversion 202 illustrates % NO conversions associated with the aged ZPGM reference catalyst. In these embodiments, NO conversion 204 illustrates % NO conversions associated with the aged ZPGM Type 1A catalyst. Further to these embodiments, NO conversion curve 206 illustrates % NO conversions associated with the aged ZPGM Type 1B catalyst. Still further to these embodiments, NO conversion curve 208 illustrates % NO conversions associated with the aged ZPGM Type 1D catalyst. In these embodiments, NO conversion curve 210 illustrates % NO conversions associated with the aged ZPGM Type 1E catalyst. Further to these embodiments, NO conversion curve 212 illustrates % NO conversions associated with the aged ZPGM Type 1G catalyst.

(51) In some embodiments, at the stoichiometric condition (O.sub.2=0.49%) the catalytic performance of the aforementioned ZPGM Type 1 catalysts is enhanced by increasing the Ni dopant. In these embodiments and at the stoichiometric condition, the ZPGM reference catalyst (Cu.sub.1Mn.sub.2O.sub.4) exhibits a NO conversion of about 0.06% while the ZPGM Type 1A catalyst exhibits a NO conversion of about 25.9%, the ZPGM Type 1B catalyst exhibits a NO conversion of about 37.5%, the ZPGM Type 1D catalyst exhibits a NO conversion of about 49.8%, the ZPGM Type 1E catalyst exhibits a NO conversion of about 63.57%, and the ZPGM Type 1G catalyst exhibits an improved NO conversion of about 68.06%. Further to these embodiments, the aforementioned ZPGM Type 1 catalysts exhibit higher NO oxidation activity when compared to the ZPGM reference catalyst.

(52) In some embodiments, the test results indicate that for the ZPGM Type 1 catalysts, the factor that most influences the improvement in NO conversion is the molar ratio of the Ni dopant. In these embodiments, as the Ni molar ratio increases at stoichiometric and lean conditions, the ZPGM Type 1 catalysts NO conversion performance rapidly increases. Further to these embodiments and under rich conditions, the NO conversion remains substantially similar within the aforementioned ZPGM Type 1 catalysts and the ZPGM reference catalyst, exhibiting a NO conversion level of about 100%.

(53) FIG. 3 is a graphical representation illustrating TWC steady-state sweep test results comparing % NO conversions at the stoichiometric condition (O.sub.2=0.49%) associated with aged ZPGM Type 1 catalysts employing various loadings of Ni within a B-site substitution of CuMn spinels, according to an embodiment. In FIG. 3, NO comparison curve 300 includes NO conversion point 302, NO conversion point 304, NO conversion point 306, NO conversion point 308, NO conversion point 310, NO conversion point 312, NO conversion point 314, NO conversion point 316, and NO conversion point 318.

(54) In some embodiments, NO conversion point 302 illustrates % NO conversion associated with the aged ZPGM reference catalyst. In these embodiments, NO conversion point 304 illustrates % NO conversion associated with the aged ZPGM Type 1A catalyst. Further to these embodiments, NO conversion point 306 illustrates % NO conversion associated with the aged ZPGM Type 1B catalyst. Still further to these embodiments, NO conversion point 308 illustrates % NO conversion associated with the aged ZPGM Type 1C catalyst. In these embodiments, NO conversion point 310 illustrates % NO conversion associated with the aged ZPGM Type 1D catalyst. Further to these embodiments, NO conversion point 312 illustrates % NO conversion associated with the aged ZPGM Type 1E catalyst. Still further to these embodiments, NO conversion point 314 illustrates % NO conversion associated with the aged ZPGM Type 1F catalyst. In these embodiments, NO conversion point 316 illustrates % NO conversion associated with the aged ZPGM Type 1G catalyst. Further to these embodiments, NO conversion point 318 illustrates % NO conversion associated with the aged ZPGM Type 1H catalyst.

(55) In some embodiments, at the stoichiometric condition the ZPGM Type 1 catalysts exhibit greater NO conversion when compared to the ZPGM reference catalyst (Cu.sub.1Mn.sub.2O.sub.4). In these embodiments and at the stoichiometric condition, catalytic performance of the ZPGM Type 1 catalysts is improved by increasing the Ni doping within the B-site cation of the CuMn spinel. Further to these embodiments and referring to NO comparison curve 300, each improvement in NO conversion within the associated ZPGM Type 1 catalysts is due to the Ni loading within the associated CuMn spinel composition.

(56) FIG. 4 is a graphical representation illustrating TWC steady-state sweep test results comparing % NO conversions at the stoichiometric condition (O.sub.2=0.49%) associated with aged ZPGM Type 2 catalysts employing various loadings of Ni within an A-site substitution of CuMn spinels, according to an embodiment. In FIG. 4, NO comparison curve 400 includes NO conversion point 402, NO conversion point 404, NO conversion point 406, No conversion point 408, NO conversion point 410, NO conversion point 412, and NO conversion point 414.

(57) In some embodiments, NO conversion point 402 illustrates % NO conversion associated with the aged ZPGM reference catalyst. In these embodiments, NO conversion point 404 illustrates % NO conversion associated with the aged ZPGM Type 2A catalyst. Further to these embodiments, NO conversion point 406 illustrates % NO conversion associated with the aged ZPGM Type 2B catalyst. Still further to these embodiments, NO conversion point 408 illustrates % NO conversion associated with the aged ZPGM Type 2C catalyst. In these embodiments, NO conversion point 410 illustrates % NO conversion associated with the aged ZPGM Type 2D catalyst. Further to these embodiments, NO conversion point 412 illustrates % NO conversion associated with the aged ZPGM Type 2E catalyst. Still further to these embodiments, NO conversion point 414 illustrates % NO conversion associated with the aged ZPGM Type 2F catalyst.

(58) In some embodiments, at the stoichiometric condition the ZPGM Type 2 catalysts exhibit greater NO conversion when compared to the ZPGM reference catalyst. In these embodiments, the ZPGM reference catalyst exhibits a NO conversion of about 0.06%. Further to these embodiments and at the stoichiometric condition, catalytic performance of the ZPGM Type 2 catalysts is improved and exhibits a maximum NO conversion of about 43.9% for the ZPGM Type 2C catalyst. Still further to these embodiments and referring to NO comparison curve 400, each improvement in NO conversion within the associated ZPGM Type 2 catalysts is due to the Ni loading within the associated CuMn spinel composition. In summary, a suitable Ni loading within the A-site cation of the CuMn spinel enables the achievement of improved NO conversion levels.

(59) FIG. 5 is a graphical representation illustrating TWC steady-state sweep test results comparing % NO conversions at specific % O.sub.2 values associated with aforementioned aged ZPGM catalysts as well as a ZPGM reference catalyst, according to an embodiment. In FIG. 5, NO comparison graph 500 includes NO conversion curve 502 (solid line), NO conversion curve 504 (dot line), and NO conversion curve 506 (dash line).

(60) In some embodiments, NO conversion curve 502 illustrates % NO conversions associated with the aged ZPGM reference catalyst. In these embodiments, NO conversion curve 504 illustrates % NO conversions associated with the aged ZPGM Type 1G catalyst. Further to these embodiments, NO conversion curve 506 illustrates % NO conversions associated with the aged ZPGM Type 2C catalyst.

(61) In some embodiments and at the stoichiometric condition, the ZPGM reference catalyst exhibits a NO conversion of about 0.06% while the ZPGM Type 1G catalyst exhibits a NO conversion of about 43.9% and the ZPGM Type 2C catalyst exhibits a NO conversion of about 68.1%. In these embodiments and referring to FIG. 5, test results confirm that improved NO conversions are achieved when Ni is partially substituted within B-site cation of the CuMn spinel within the aforementioned ZPGM Type 1 catalysts. Further to these embodiments and referring to FIG. 5, test results confirm there are NO conversion improvements when Ni is partially substituted within the A-site cation of the CuMn spinel within the aforementioned ZPGM Type 2 catalysts. Still further to these embodiments, the aforementioned A-site and B-site Ni-doped CuMn spinel ZPGM catalysts (especially the ZPGM Type 1 catalyst) exhibit higher NO conversion performance at stoichiometric and lean conditions when compared to the ZPGM reference catalyst.

(62) In summary, the factor that mostly influences the improvements in catalytic performance (e.g., NO conversion) within the aforementioned ZPGM catalysts is the molar ratio of the Ni dopant. Further, the site of the Ni dopant also affects the aforementioned catalytic performance. As Ni is doped within the B-site cation of the CuMn spinel, the aforementioned ZPGM Type 1 catalysts exhibit improved catalyst activity when compared to the ZPGM reference catalyst. Additionally, the aforementioned ZPGM catalysts can provide improved ZPGM catalysts for TWC applications.

(63) 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.