Synergized PGM catalyst systems including platinum for TWC application

Abstract

Synergized Platinum Group Metals (SPGM) catalyst system for TWC application is disclosed. Disclosed SPGM catalyst system may include a washcoat that includes stoichiometric CuMn spinel structure, supported on doped ZrO.sub.2, and an overcoat that includes PGM, such as platinum (Pt) supported on carrier material oxides, such as alumina. SPGM catalyst system shows significant improvement in nitrogen oxide reduction performance under lean and also rich operating conditions. Additionally, disclosed SPGM catalyst system exhibits enhanced catalytic activity for carbon monoxide conversion. Furthermore, disclosed SPGM catalyst systems are found to have enhanced catalytic activity compared to PGM catalyst system, showing that there is a synergistic effect between PGM catalyst, such as Pt, and CuMn spinel within disclosed SPGM catalyst system, which help in activity and thermal stability of disclosed SPGM catalyst.

Claims

1. A synergized platinum group metal (SPGM) catalyst system, comprising: at least one substrate; at least one washcoat comprising at least one oxygen storage material further comprising CuMn spinel having a niobium-zirconia support oxide; and at least one overcoat comprising at least one platinum group metal catalyst and Al.sub.2O.sub.3; wherein the at least one platinum group metal catalyst has a concentration of about 6 g/ft.sup.3 to about 1 g/ft.sup.3; and wherein NOx conversion is higher as compared to a platinum group metal catalyst having substantially no CuMn spinel.

2. The catalyst system of claim 1, wherein the CuMn spinel comprises CuMn.sub.2O.sub.4.

3. The catalyst system of claim 1, wherein the CuMn spinel is stoichiometric.

4. The catalyst system of claim 1, wherein the niobium-zirconia support oxide comprises Nb.sub.2O.sub.5 ZrO.sub.2.

5. The catalyst system of claim 1, further comprising at least one impregnation layer.

6. The catalyst system of claim 1, wherein the at least one substrate comprises a ceramic.

7. The catalyst system of claim 1, wherein the conversion of NO.sub.x is substantially complete under lean exhaust conditions.

8. The catalyst system of claim 1, wherein the conversion of CO is substantially complete under lean exhaust conditions.

9. The catalyst system of claim 1, wherein the conversion of NO.sub.x is about 91% under lean exhaust conditions.

10. The catalyst system of claim 1, wherein the NO.sub.x R-value is about 0.950.

11. The catalyst system of claim 1, wherein the NO.sub.x R-value is about 1.0.

12. The catalyst system of claim 1, wherein the niobium-zirconia support oxide comprises about 15% to about 30% by weight Nb.sub.2O.sub.5.

13. The catalyst system of claim 1, wherein the niobium-zirconia support oxide comprises about 25% by weight Nb.sub.2O.sub.5.

14. The catalyst system of claim 1, wherein the niobium-zirconia support oxide comprises about 70% to about 85% ZrO.sub.2.

15. The catalyst system of claim 1, wherein the niobium-zirconia support oxide comprises about 75% ZrO.sub.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Non-limiting embodiments of the present disclosure are described by way of example with reference to the accompanying figures which are schematic and are not intended to be drawn to scale. Unless indicated as representing the background art, the figures represent aspects of the disclosure.

(2) FIG. 1 shows a SPGM catalyst system configuration including CuMn spinel referred as SPGM catalyst system Type 1, according to an embodiment.

(3) FIG. 2 illustrates a PGM catalyst system configuration with no CuMn spinel referred as catalyst system Type 2, according to an embodiment.

(4) FIG. 3 depicts NO.sub.x conversion comparison for fresh samples of SPGM catalyst systems Type 1, and PGM catalyst system Type 2, under isothermal steady state sweep condition, at inlet temperature of about 450 C., and space velocity (SV) of about 40,000 h.sup.1, according to an embodiment.

(5) FIG. 4 depicts NOx conversion comparison for hydrothermally aged samples (at 900 C. during about 4 hours) of SPGM catalyst systems Type 1 and PGM catalyst system Type 2, under isothermal steady state sweep condition, at inlet temperature of about 450 C., and SV of about 40,000 h.sup.1, according to an embodiment.

(6) FIG. 5 depicts NOx conversion comparison for fuel cut aged samples (at 800 C. during about 20 hours) of SPGM catalyst systems Type 1 and PGM catalyst system Type 2, under isothermal steady state sweep condition, at inlet temperature of about 450 C., according to an embodiment.

(7) FIG. 6 depicts CO conversion comparison for hydrothermally aged samples (at 900 C. during about 4 hours) of SPGM catalyst systems Type 1 and PGM catalyst system Type 2 under isothermal steady state sweep condition, at inlet temperature of about 450 C., and SV of about 40,000 h.sup.1, according to an embodiment.

(8) FIG. 7 depicts CO conversion comparison for fuel cut aged samples (at 800 C. during about 20 hours) of SPGM catalyst systems Type 1 and PGM catalyst system Type 2, under isothermal steady state sweep condition, at inlet temperature of about 450 C., and SV of about 40,000 h.sup.1, according to an embodiment.

DETAILED DESCRIPTION

(9) In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, which are not to scale or to proportion, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings and claims, are not meant to be limiting. Other embodiments may be used and/or and other changes may be made without departing from the spirit or scope of the present disclosure.

DEFINITIONS

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

(11) Catalyst system refers to a system of at least two layers including at least one substrate, a washcoat, and/or an overcoat.

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

(13) Washcoat refers to at least one coating including at least one oxide solid that may be deposited on a substrate.

(14) Overcoat refers to at least one coating that may be deposited on at least one washcoat layer.

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

(16) Milling refers to the operation of breaking a solid material into a desired grain or particle size.

(17) Co-precipitation refers to the carrying down by a precipitate of substances normally soluble under the conditions employed.

(18) 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.

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

(20) Synergized platinum group metal (SPGM) catalyst refers to a PGM catalyst system which is synergized by a non-PGM group metal compound under different configuration.

(21) Zero Platinum group metals (ZPGM) refers to catalyst system that is free of PGM.

(22) Treating, treated, or treatment refers to drying, firing, heating, evaporating, calcining, or mixtures thereof.

(23) Three-Way Catalyst refers to a catalyst that may achieve three simultaneous tasks: reduce nitrogen oxides to nitrogen and oxygen, oxidize carbon monoxide to carbon dioxide, and oxidize unburnt hydrocarbons to carbon dioxide and water.

(24) R-Value refers to the number obtained by dividing the reducing potential by the oxidizing potential.

(25) Lean condition refers to exhaust gas condition with an R-value below 1.

(26) Rich condition refers to exhaust gas condition with an R value above 1.

(27) Stoichiometric condition refers to the condition when the oxygen of the combustion gas or air added equals the amount for completely combusting the fuel.

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

(29) Spinel refers to any of various mineral oxides of magnesium, iron, zinc, or manganese in combination with aluminum, chromium, copper or iron with AB.sub.2O.sub.4 structure.

DESCRIPTION OF THE DRAWINGS

(30) The present disclosure may provide a synergized PGM (SPGM) catalyst system which may have enhanced catalytic performance of PGM catalyst under lean condition or rich condition, by incorporating more active components into phase materials possessing three-way catalyst (TWC) properties.

(31) Embodiments of the present disclosure provide catalyst performance comparison of disclosed SPGM catalyst system and a PGM catalyst system that may include Platinum (Pt) within the overcoat of disclosed SPGM catalyst systems, and within the PGM catalyst system.

(32) According to embodiments in the present disclosure, SPGM catalyst systems may be configured with a washcoat including CuMn stoichiometric spinel with doped ZrO.sub.2 support oxide such as Niobium-Zirconia support oxide, an overcoat including a PGM catalyst, such as Pt with alumina-based support, and suitable ceramic substrate, here referred as SPGM catalyst system Type 1. According to embodiments in the present disclosure, PGM catalyst systems may be configured with washcoat layer including doped ZrO.sub.2 support oxide such as Niobium-Zirconia support oxide, an overcoat including PGM catalyst, such as Pt with alumina-based support, and suitable ceramic substrate, here referred as PGM catalyst system Type 2.

(33) Catalyst System Configuration

(34) FIG. 1 shows a SPGM catalyst system configuration referred as SPGM catalyst system Type 1 100, according to an embodiment.

(35) As shown in FIG. 1, SPGM catalyst system Type 1 100 may include at least a substrate 102, a washcoat 104, and an overcoat 106, where washcoat 104 may include a stoichiometric CuMn spinel structure, Cu.sub.1.0Mn.sub.2.0O.sub.4, supported on doped ZrO.sub.2 and overcoat 106 may include PGM catalyst, such as Pt supported on carrier material oxides, such as alumina.

(36) In an embodiment, substrate 102 materials for SPGM catalyst system Type 1 100 may include a refractive material, a ceramic material, a honeycomb structure, a metallic material, a ceramic foam, a metallic foam, a reticulated foam, or suitable combinations, where substrate 102 may have a plurality of channels with suitable porosity. Porosity may vary according to the particular properties of substrate 102 materials. Additionally, the number of channels may vary depending upon substrate 102 used as is known in the art. The type and shape of a suitable substrate 102 would be apparent to one of ordinary skill in the art. According to the present disclosure, preferred substrate 102 materials may be ceramic material.

(37) According to an embodiment, washcoat 104 for SPGM catalyst system Type 1 100 may include a CuMn stoichiometric spinel, Cu.sub.1.0Mn.sub.2.0O.sub.4, as non PGM metal catalyst. Additionally, washcoat 104 may include support oxide such as zirconium oxide, doped zirconia. According to the present disclosure, suitable material for disclosed washcoat 104 may be Nb.sub.2O.sub.5ZrO.sub.2.

(38) According to embodiments of the present disclosure, overcoat 106 for SPGM catalyst system Type 1 100 may include aluminum oxide, doped aluminum oxide, zirconium oxide, doped zirconia, titanium oxide, tin oxide, silicon dioxide, zeolite, and mixtures thereof. According to the present disclosure, most suitable material for disclosed overcoat 106 may be alumina (Al.sub.2O.sub.3). Additionally, overcoat 106 for SPGM catalyst system Type 1 100 may include a PGM catalyst, such as Palladium (Pd), Platinum (Pt), and Rhodium (Rh), among others. According to the present disclosure, most suitable PGM for disclosed overcoat 106 may be Pt.

(39) FIG. 2 illustrates a PGM catalyst system configuration referred as PGM catalyst system Type 2 200, according to an embodiment.

(40) As shown in FIG. 2, PGM catalyst system Type 2 200 may include at least a substrate 102, a washcoat 104, and an overcoat 106, where washcoat 104 may include doped ZrO.sub.2 and overcoat 106 may include carrier material oxides, such as alumina mixed with a PGM catalyst, such as Pt.

(41) In an embodiment, substrate 102 materials for PGM catalyst system Type 2 200 may include a refractive material, a ceramic material, a honeycomb structure, a metallic material, a ceramic foam, a metallic foam, a reticulated foam, or suitable combinations. According to the present disclosure, preferred substrate 102 materials may be ceramic material.

(42) According to an embodiment, washcoat 104 for PGM catalyst system Type 2 200 may include support oxide such as zirconium oxide, doped zirconia. According to the present disclosure, suitable material for disclosed washcoat 104 may be Nb.sub.2O.sub.5ZrO.sub.2.

(43) According to embodiments of the present disclosure, overcoat 106 for PGM catalyst system Type 2 200 may include aluminum oxide, doped aluminum oxide, zirconium oxide, doped zirconia, titanium oxide, tin oxide, silicon dioxide, zeolite, and mixtures thereof. According to the present disclosure, most suitable material for disclosed overcoat 106 may be alumina (Al.sub.2O.sub.3). Additionally, overcoat 106 for PGM catalyst system Type 2 200 may include a PGM catalyst, such as Pt.

(44) According to embodiments of the present disclosure PGM catalyst system Type 2 200 has the same configuration as SPGM catalyst system Type 1 100 in which CuMn spinel is removed from washcoat 104, in order to demonstrate the effect of addition of CuMn spinel to PGM catalyst system Type 2 200.

(45) Preparation of SPGM Catalyst System Type 1 (with CuMn Spinel)

(46) The preparation of washcoat 104 may begin by milling Nb.sub.2O.sub.5ZrO.sub.2 support oxide to make aqueous slurry. The Nb.sub.2O.sub.5ZrO.sub.2 support oxide may have Nb.sub.2O.sub.5 loadings of about 15% to about 30% by weight, preferably about 25% and ZrO.sub.2 loadings of about 70% to about 85% by weight, preferably about 75%.

(47) The CuMn solution may be prepared by mixing for about 1 to 2 hours, an appropriate amount of Mn nitrate solution and Cu nitrate solution. Subsequently, CuMn nitrate solution may be mixed with Nb.sub.2O.sub.5ZrO.sub.2 support oxide slurry for about 2 to 4 hours, where CuMn nitrate solution may be precipitated on Nb.sub.2O.sub.5ZrO.sub.2 support oxide aqueous slurry. A suitable base solution may be added, such as sodium hydroxide (NaOH) solution, sodium carbonate (Na.sub.2CO.sub.3) solution, ammonium hydroxide (NH.sub.4OH) solution, tetraethyl ammonium hydroxide (TEAH) solution, (NH.sub.4).sub.2CO.sub.3, other tetraalkylammonium salts, ammonium acetate, or ammonium citrate, amongst others, to adjust pH at desired level. The precipitated CuMn/Nb.sub.2O.sub.5ZrO.sub.2 slurry may be aged for a period of time of about 12 to 24 hours under continued stirring at room temperature.

(48) Subsequently, the precipitated slurry may be coated on substrate 102. The aqueous slurry of CuMn/Nb.sub.2O.sub.5ZrO.sub.2 may be deposited on the suitable ceramic substrate 102 to form washcoat 104, employing vacuum dosing and coating systems. In the present disclosure, a plurality of capacities of washcoat 104 loadings may be coated on the suitable ceramic substrate 102. The plurality of washcoat 104 loading may vary from about 60 g/L to about 200 g/L, in the present disclosure particularly about 120 g/L. Subsequently, after deposition on ceramic substrate 102 of the suitable loadings of CuMn/Nb.sub.2O.sub.5ZrO.sub.2 slurry, washcoat 104 may be dried overnight at about 120 C. and subsequently calcined at a suitable temperature within a range of about 550 C. to about 650 C., preferably at about 600 C. for about 5 hours. Treatment of washcoat 104 may be enabled employing suitable drying and heating processes. A commercially-available air knife drying systems may be employed for drying washcoat 104. Heat treatments (calcination) may be performed using commercially-available firing (furnace) systems.

(49) Overcoat 106 may include a combination of Pt on alumina-based support. The preparation of overcoat 106 may begin by milling the alumina-based support oxide separately to make aqueous slurry. Subsequently, a solution of Pt nitrate may be mixed with the aqueous slurry of alumina with a loading within a range from about 0.5 g/ft.sup.3 to about 10 g/ft.sup.3. According to the present disclosure, suitable loading of Pt for disclosed SPGM Catalyst System Type 1 100 may be 1 g/ft.sup.3. Total loading of washcoat 104 material may be 120 g/L. After mixing of Pt and alumina slurry, Pt may be locked down with an appropriate amount of one or more base solutions, such as sodium hydroxide (NaOH) solution, sodium carbonate (Na.sub.2CO.sub.3) solution, ammonium hydroxide (NH.sub.4OH) solution, tetraethyl ammonium hydroxide (TEAH) solution, among others. Then, the resulting slurry may be aged from about 12 hours to about 24 hours for subsequent coating as overcoat 106 on washcoat 104, dried and fired at about 550 C. for about 4 hours.

(50) Preparation of PGM Catalyst System Type 2 (without CuMn Spinel)

(51) The preparation of washcoat 104 may begin by milling Nb.sub.2O.sub.5ZrO.sub.2 support oxide to make aqueous slurry. The Nb.sub.2O.sub.5ZrO.sub.2 support oxide may have Nb.sub.2O.sub.5 loadings of about 15% to about 30% by weight, preferably about 25% and ZrO.sub.2 loadings of about 70% to about 85% by weight, preferably about 75%.

(52) Subsequently, washcoat 104 slurry may be coated on substrate 102. The washcoat 104 slurry may be deposited on the suitable ceramic substrate 102 to form washcoat 104, employing vacuum dosing and coating systems. In the present disclosure, a plurality of capacities of washcoat 104 loadings may be coated on suitable ceramic substrate 102. The plurality of washcoat 104 loading may vary from about 60 g/L to about 200 g/L, in the present disclosure particularly about 120 g/L. Washcoat 104 may be dried overnight at about 120 C. and subsequently calcined at a suitable temperature within a range of about 550 C. to about 650 C., preferably at about 550 C. for about 4 hours. Treatment of washcoat 104 may be enabled employing suitable drying and heating processes. A commercially-available air knife drying systems may be employed for drying washcoat 104. Heat treatments (calcination) may be performed using commercially-available firing (furnace) systems.

(53) Overcoat 106 may include a combination of Pt on alumina-based support. The preparation of overcoat 106 may begin by milling the alumina-based support oxide separately to make aqueous slurry. Subsequently, a solution of Pt nitrate may be mixed with the aqueous slurry of alumina with a loading within a range from about 0.5 g/ft.sup.3 to about 10 g/ft.sup.3. According to the present disclosure, suitable loading of Pt for disclosed SPGM Catalyst System Type 1 100 may be 1 g/ft.sup.3. Total loading of washcoat 104 material may be 120 g/L. After mixing of Pt and alumina slurry, Pt may be locked down with an appropriate amount of one or more base solutions, such as sodium hydroxide (NaOH) solution, sodium carbonate (Na.sub.2CO.sub.3) solution, ammonium hydroxide (NH.sub.4OH) solution, tetraethyl ammonium hydroxide (TEAH) solution, among others. Then, the resulting slurry may be aged from about 12 hours to about 24 hours for subsequent coating as overcoat 106 on washcoat 104, dried and fired at about 550 C. for about 4 hours.

(54) Catalytic performance, for SPGM Catalyst System Type 1 100 and PGM catalyst system Type 2 200 may be compared by preparing fresh and aged samples for each of the catalyst formulations and configurations in present disclosure to show the synergistic effect of adding CuMn spinel to PGM catalyst materials which may be used in TWC applications.

(55) In order to compare TWC performance of disclosed SPGM catalyst system Type 1 100 and PGM catalyst system Type 2 200, isothermal steady state sweep tests may be performed.

(56) Isothermal Steady State Sweep Test Procedure

(57) The isothermal steady state sweep test may be carried out employing a flow reactor in which the inlet temperature may be increased to about 450 C., and testing a gas stream at 11-point R-values from about 2.0 (rich condition) to about 0.80 (lean condition) to measure the CO, NO.sub.x, and HC conversions.

(58) The space velocity (SV) in the flow reactor may be adjusted at about 40,000 h.sup.1. The gas feed employed for the test may be a standard TWC gas composition, with variable O.sub.2 concentration in order to adjust R-value from rich condition to lean condition during testing. The standard TWC gas composition may include 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, 10% of CO.sub.2, and 10% of H.sub.2O. The quantity of O.sub.2 in the gas mix may be varied to adjust R-value which is representative of Air/Fuel (A/F) ratio and to represent the three-way condition of the control loop.

(59) NOx Conversion Comparison of SPGM Catalyst System Type 1 and PGM Catalyst System Type 2

(60) FIG. 3 depicts NOx conversion comparison 300 for fresh samples of SPGM catalyst system Type 1 100 and fresh samples of PGM catalyst system Type 2 200, under isothermal steady state sweep condition, at inlet temperature of about 450 C. and SV of about 40,000 h.sup.1, according to an embodiment.

(61) As may be observed in FIG. 3, NOx conversion curve 302 (solid line) depicts performance of SPGM catalyst system Type 1 100, and NO conversion curve 304 (dashed line) illustrates performance of PGM catalyst system Type 2 200, under isothermal steady state sweep condition.

(62) As may be observed in NOx conversion comparison 300, disclosed SPGM catalyst system Type 1 100 may perform better than disclosed PGM catalyst system Type 2 200, because of their improved NO conversion under lean condition. For example, as shown in FIG. 3, at lean condition, R-value of about 0.9, while SPGM catalyst system Type 1 100 shows NO.sub.x conversion of about 91.7%, PGM catalyst system Type 2 200 shows NO.sub.x conversion of about 65.9%.

(63) As may be seen in lean NOx conversion comparison 300, for fresh samples, there is an improved performance in NO.sub.x conversion for disclosed SPGM catalyst system Type 1 100, under lean condition (R-value<1.00) as compared to PGM catalyst system Type 2 200. This improved performance is the result of the synergistic effect between Pt, and the CuMn spinel components in the respective composition of SPGM catalyst system Type 1 100, in which adding of CuMn spinel components is responsible for the improved performance of NO.sub.x conversion under lean condition compared with the level of NO.sub.x conversion of PGM catalyst system Type 2 200 shown in NOx conversion comparison 300.

(64) In addition, both fresh samples of SPGM catalyst system Type 1 100 and of PGM catalyst system Type 2 200 present NO.sub.x conversion of about 100% at R-value of about 1.00, which is the stoichiometric R-value for PGM catalysts.

(65) FIG. 4 depicts NOx conversion comparison 400 for hydrothermally aged samples (at 900 C. during about 4 hours) of SPGM catalyst system Type 1 100; and PGM catalyst system Type 2 200, under isothermal steady state sweep condition, at inlet temperature of about 450 C. and SV of about 40,000 h.sup.1, according to an embodiment.

(66) In FIG. 4, NOx conversion curve 402 (solid line) shows performance of SPGM catalyst system Type 1 100, NOx conversion curve 404 (dashed line) depicts performance of PGM catalyst system Type 2 200, under isothermal steady state sweep condition.

(67) As may be observed in NOx conversion comparison 400, disclosed SPGM catalyst system Type 1 100 after hydrothermal aging may perform better than disclosed PGM catalyst system Type 2 200 after same hydrothermal aging, because of their improved NO conversion under rich condition. For example, as shown in FIG. 4, at all R-values region PGM catalyst system Type 2 200 shows no activity on NO.sub.x conversion, this is because Pt catalyst may be passivated by aging treatment (at 900 C. during about 4 hours). Moreover, SPGM catalyst system Type 1 100 shows catalytic activity of about 65.5% at R value of about 1.6 and of about 64% at fully rich condition, R-value of about 2.0. Since Pt may be passivated by the aging treatment (at 900 C. during about 4 hours), the catalytic activity of aged SPGM catalyst system Type 1 100 may be achieved only by the CuMn spinel components in the composition of SPGM catalyst system Type 1 100 in which adding of CuMn spinel components is responsible for the performance of NO.sub.x conversion compared with no NO.sub.x conversion of PGM catalyst system Type 2 200 shown in NOx conversion comparison 400.

(68) FIG. 5 depicts NOx conversion comparison 500 in NO.sub.x conversion for fuel cut aged samples (aged at 800 C. during about 20 hours) of SPGM catalyst system Type 1 100, and PGM catalyst system Type 2 200, under isothermal steady state sweep condition, at inlet temperature of about 450 C. and SV of about 40,000 h.sup.1, according to an embodiment.

(69) In FIG. 5, NOx conversion comparison 500, NOx conversion curve 502 (solid line) shows performance of SPGM catalyst system Type 1 100 after fuel cut aging, NOx conversion curve 504 (dashed line) depicts performance of PGM catalyst system Type 2 200 after fuel cut aging.

(70) As may be observed in NOx conversion comparison 500, disclosed SPGM catalyst system Type 1 100 after fuel cu aging may perform better than disclosed PGM catalyst system Type 2 200 after same fuel cut aging, because of their improved NO conversion under rich condition. For example, as shown in FIG. 5, at all R-values region PGM catalyst system Type 2 200 shows very low activity on NO.sub.x conversion (below about 6.0%), this is because Pt catalyst may be passivated by fuel cut aging treatment (at 800 C. during about 20 hours). Moreover, SPGM catalyst system Type 1 100 shows catalytic activity of about 85% at R value of about 1.6 (rich condition) and of about 92.5% at fully rich condition, R-value of about 2.0. Since Pt may be passivated by the fuel cut aging treatment (at 800 C. during about 20 hours), the catalytic activity of aged SPGM catalyst system Type 1 100 may be achieved only by the CuMn spinel components in the composition of SPGM catalyst system Type 1 100 in which adding of CuMn spinel components is responsible for the performance of NO.sub.x conversion under rich condition compared with no NO.sub.x conversion of PGM catalyst system Type 2 200 shown in NOx conversion comparison 500.

(71) CO Conversion Comparison of SPGM Catalyst System Type 1 and PGM Catalyst System Type 2

(72) FIG. 6 depicts CO conversion comparison 600 in CO conversion for fresh samples of SPGM catalyst system Type 1 100, and PGM catalyst system Type 2 200, under isothermal steady state sweep condition, at inlet temperature of about 450 C. and SV of about 40,000 h.sup.1, according to an embodiment.

(73) In FIG. 6, CO conversion curve 602 (solid line) shows performance of fresh SPGM catalyst system Type 1 100, CO conversion curve 604 (dashed line) depicts performance of fresh PGM catalyst system Type 2 200, under isothermal steady state sweep condition.

(74) As may be observed in CO conversion comparison 600, disclosed SPGM catalyst system Type 1 100 may perform better than disclosed PGM catalyst system Type 2 200, because of their improved CO conversion under rich condition. For example, as shown in FIG. 6, at fully rich condition, R-value of about 2.0, while SPGM catalyst system Type 1 100 shows CO conversion of about 90.6%, PGM catalyst system Type 2 200 shows CO conversion of about 65.3%.

(75) As may be observed in CO conversion comparison 600, for fresh samples there is an improved performance in CO conversion for disclosed SPGM catalyst system Type 1 100, under rich condition as compared to PGM catalyst system Type 2 200. This improved performance of SPGM catalysts is the result of the synergistic effect between Pt, and the CuMn spinel components in the respective composition of SPGM catalyst system Type 1 100, in which adding the CuMn spinel components is responsible for the improved performance of CO conversion under rich condition compared to the level of CO conversion of PGM catalyst system Type 2 200, shown in CO conversion comparison 600.

(76) In addition, samples of fresh SPGM catalyst system Type 1 100 and of fresh PGM catalyst system Type 2 200 present CO conversion of about 100% at R-value of about 1.00, which is the stoichiometric R-value for PGM catalysts.

(77) FIG. 7 depicts CO conversion comparison 700 in CO conversion for hydrothermal aged samples (aged at 900 C. during about 4 hours) of SPGM catalyst system Type 1 100, and PGM catalyst system Type 2 200, under isothermal steady state sweep condition, at inlet temperature of about 450 C. and SV of about 40,000 h.sup.1, according to an embodiment.

(78) In FIG. 7, CO conversion curve 702 (solid line) shows performance of SPGM catalyst system Type 1 100 after hydrothermal aging, CO conversion curve 704 (dashed line) depicts performance of PGM catalyst system Type 2 200 after hydrothermal aging, under isothermal steady state sweep condition.

(79) As may be observed in CO conversion comparison 700, disclosed SPGM catalyst system Type 1 100 after hydrothermal aging may perform better than disclosed PGM catalyst system Type 2 200 after same aging, because of their improved CO conversion under rich condition. For example, as shown in FIG. 7, at all R-values region PGM catalyst system Type 2 200 shows no activity on CO conversion, this may be because Pt catalyst may be passivated by aging treatment (at 900 C. during about 4 hours). Moreover, SPGM catalyst system Type 1 100 shows catalytic activity of about 78.5% at R value of about 1.6 and of about 68.3% at fully rich condition, R-value of about 2.0. Since Pt may be passivated by the aging treatment, the catalytic activity of aged SPGM catalyst system Type 1 100 may be achieved only by the CuMn spinel components in the composition of SPGM catalyst system Type 1 100 in which adding the CuMn spinel components is responsible for the performance of CO conversion under rich condition compared to no CO conversion of PGM catalyst system Type 2 200, shown in CO conversion comparison 700.

(80) SPGM catalyst system of the present disclosure, which is suitable for TWC application, may show significant improvement in nitrogen oxide conversion under lean operating conditions, in which synergistic effect between Pt and CuMn spinel is responsible for such improvement. Furthermore, disclosed SPGM catalyst system that includes a CuMn spinel may enable the use of a catalyst converter that includes very low amounts of PGM. Furthermore, synergistic effect of CuMn on Pt results is improvement of CO conversion under both lean and rich condition. The improvement is more significant under rich condition. In addition, the significant improvement of NO and CO conversion under lean-rich condition of disclosed SPGM catalyst after hydrothermal and fuel cut aging shows thermal stability of disclosed SPGM catalyst systems, in which ZPGM component, CuMn spinel, is responsible for such stability.

(81) 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.