WO2012037526A2

WO2012037526A2 - Nitric oxide oxidation catalysts

Info

Publication number: WO2012037526A2
Application number: PCT/US2011/052040
Authority: WO
Inventors: Geoffrey Mccool; Xianghong Hao
Original assignee: Nanostellar, Inc.
Priority date: 2010-09-17
Filing date: 2011-09-16
Publication date: 2012-03-22
Also published as: WO2012037526A3

Abstract

A nitric oxide oxidation catalyst contains a brownmillerite compound modified with an additional transition metal. In one embodiment, the additional transition metal is selected from cobalt or manganese. The nitric oxide oxidation catalyst may be used as an engine exhaust catalyst.

Description

NITRIC OXIDE OXIDATION CATALYSTS

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] Embodiments of the present invention are directed to metal oxide oxidation catalysts and more particularly nitric oxide oxidation catalysts containing mixed metal oxides. More particularly still, embodiments of the present invention are directed to engine exhaust catalysts containing a brown millerite compound modified with an additional transition metal.

2. Description of the Related Art

[0002] Nitrogen oxides (NOx) abatement is one of the key concerns for lean burn engines such as diesel engines. One solution has been to oxidize the nitric oxide in the emission gases, as the oxidized NO₂ assists the oxidation of soot and promotes denox reactions in the downstream devices like SCR and LNT. Platinum based catalysts have been successfully used to oxidize the nitric oxide. However, platinum is a relatively high cost material.

[0003] In this respect, catalyst developers are continually exploring ways to use alternative metals that are less costly. Therefore is, therefore, suitable non- precious group metals for use as catalysts.

SUMMARY OF THE INVENTION

[0004] Embodiments of the present invention provide nitric oxide oxidation catalysts containing a brownmillerite compound modified with an additional transition metal. In one embodiment, the brownmillerite compound is modified by the addition of Cobalt or Manganese.

[0005] A nitric oxide oxidation catalyst according to another embodiment has the general formula

wherein A is a metallic element selected from the group consisting of elements from Alkali metals, Alkaline earth metals and the Lanthanide Series of the lUPAC Periodic Table of the Elements;

B is a metallic element selected from the group consisting of elements from the Alkali metals, Alkaline earth metals, transition metals, poor metals, and the Lanthanide Series;

C is a metallic element selected from the group consisting of the transition metals, wherein A, B, and C are different metals;

x is a number from 1 to 5, and

y is a number that renders the catalyst substantially charge neutral.

[0006] In another variation, the nitric oxide oxidation catalyst does not include a precious metal such as platinum, palladium, or gold.

[0007] In another embodiment, any of the above nitric oxide oxidation catalysts may be used as an engine exhaust catalyst and may be applied to a selected brick, zone, or layer in a multi-brick, multi-zoned, or multi-layered emission control systems to provide a boost in oxidation performance of the overall system and/or a cost reduction. In yet another embodiment, a platinum based catalysts or other suitable catalysts may be included in a different one of the washcoat zones or layers. Zeolites may be added as a hydrocarbon absorbing component in any one of the bricks, zones, or layers.

[0008] A method of producing an engine exhaust catalyst includes preparing a metal salt solution including Cobalt or Manganese and metal salts of the general formula:

A₂B₂0₅

wherein A is a metallic element selected from the group consisting of elements from Alkali metals, Alkaline earth metals and the Lanthanide Series of the lUPAC Periodic Table of the Elements; and B is a metallic element selected from the group consisting of elements from the Alkali metals, Alkaline earth metals, transition metals, poor metals, and the Lanthanide Series. The method also includes adding sodium hydroxide, sodium carbonate, or ammonium oxalate to precipitate the metal salts; oxidizing the metal salts with hydrogen peroxide; and separating the oxidized metal salts.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0010] FIGS. 1A-1 D are schematic representations of different engine exhaust systems in which embodiments of the present invention may be used.

[0011] FIG. 2 is an illustration of a catalytic converter with a cut-away section that shows a substrate onto which emission control catalysts according to embodiments of the present invention are coated.

[0012] FIGS. 3A-3D illustrate different configurations of a substrate for an emission control catalyst.

DETAILED DESCRIPTION

[0013] In the following, reference is made to embodiments of the invention. However, it should be understood that the invention is not limited to specific described embodiments. Instead, any combination of the following features and elements, whether related to different embodiments or not, is contemplated to implement and practice the invention. Furthermore, in various embodiments the invention provides numerous advantages over the prior art. However, although embodiments of the invention may achieve advantages over other possible solutions and/or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the invention. Thus, the following aspects, features, embodiments and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in the claims. Likewise, reference to "the invention" shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in the claims.

[0014] Figures 1A-1 D are schematic representations of different engine exhaust systems in which embodiments of the present invention may be used. The combustion process that occurs in an engine 102 produces harmful pollutants, such as CO, various hydrocarbons, particulate matter, and nitrogen oxides (NO_x), in an exhaust stream that is discharged through a tail pipe 108 of the exhaust system.

[0015] In the exhaust system of Figure 1A, the exhaust stream from an engine 102 passes through a catalytic converter 104, before it is discharged into the atmosphere (environment) through a tail pipe 108. The catalytic converter 104 contains supported catalysts coated on a monolithic substrate that treat the exhaust stream from the engine 102. The exhaust stream is treated by way of various catalytic reactions that occur within the catalytic converter 104. These reactions include the oxidation of CO to form CO2, burning of hydrocarbons, and the conversion of NO to NO₂.

[0016] In the exhaust system of Figure 1 B, the exhaust stream from the engine 102 passes through a catalytic converter 104 and a particulate filter 106, before it is discharged into the atmosphere through a tail pipe 108. The catalytic converter 104 operates in the same manner as in the exhaust system of Figure 1A. The particulate filter 106 traps particulate matter that is in the exhaust stream, e.g., soot, liquid hydrocarbons, generally particulates in liquid form. In an optional configuration, the particulate filter 106 includes a supported catalyst coated thereon for the oxidation of NO and/or to aid in combustion of particulate matter.

[0017] In the exhaust system of Figure 1 C, the exhaust stream from the engine 102 passes through a catalytic converter 104, a pre-filter catalyst 105 and a particulate filter 106, before it is discharged into the atmosphere through a tail pipe 108. The catalytic converter 104 operates in the same manner as in the exhaust system of Figure 1A. The pre-filter catalyst 105 includes a monolithic substrate and supported catalysts coated on the monolithic substrate for the oxidation of NO. The particulate filter 06 traps particulate matter that is in the exhaust stream, e.g., soot, liquid hydrocarbons, generally particulates in liquid form.

[0018] In the exhaust system of Figure 1 D, the exhaust stream passes from the engine 102 through a catalytic converter 104, a particulate filter 106, a selective catalytic reduction (SCR) unit 107 and an ammonia slip catalyst 1 10, before it is discharged into the atmosphere through a tail pipe 108. The catalytic converter 104 operates in the same manner as in the exhaust system of Figure 1A. The particulate filter 106 traps particulate matter that is in the exhaust stream, e.g., soot, liquid hydrocarbons, generally particulates in liquid form. In an optional configuration, the particulate filter 106 includes a supported catalyst coated thereon for the oxidation of NO and/or to aid in combustion of particulate matter. The SCR unit 107 is provided to reduce the NO_x species to N2. The SCR unit 107 may be ammonia/urea based or hydrocarbon based. The ammonia slip catalyst 1 10 is provided to reduce the amount of ammonia emissions through the tail pipe 108. An alternative configuration places the SCR unit 107 in front of the particulate filter 106.

[0019] Alternative configurations of the exhaust system includes the provision of SCR unit 107 and the ammonia slip catalyst 1 10 in the exhaust system of Figure 1A or 1 C, and the provision of just the SCR unit 107, without the ammonia slip catalyst 1 10, in the exhaust system of Figures 1A, 1 B or 1 C. As a further alternative, a NO_x storage reduction (NSR) catalyst may be used in place of the SCR unit 107.

[0020] As particulates get trapped in the particulate filter within the exhaust system of Figure 1 B, 1 C or 1 D, it becomes less effective and regeneration of the particulate filter becomes necessary. The regeneration of the particulate filter can be either passive or active. Passive regeneration occurs automatically in the presence of NO₂. Thus, as the exhaust stream containing NO₂ passes through the particulate filter, passive regeneration occurs. During regeneration, the particulates get oxidized and NO₂ gets converted back to NO. In general, higher amounts of NO₂ improve the regeneration performance, and thus this process is commonly referred to as N0₂ assisted oxidation. However, too much N0₂ is not desirable because excess NO₂ is released into the atmosphere and N0₂ is considered to be a more harmful pollutant than NO. The NO used for regeneration can be formed in the engine during combustion, from NO oxidation in the catalytic converter 104, from NO oxidation in the pre-filter catalyst 105, and/or from NO oxidation in a catalyzed version of the particulate filter 106.

[0021] Active regeneration is carried out by heating up the particulate filter 106 and oxidizing the particulates. At higher temperatures, NO₂ assistance of the particulate oxidation becomes less important. The heating of the particulate filter 106 may be carried out in various ways known in the art. One way is to employ a fuel burner which heats the particulate filter 106 to particulate combustion temperatures. Another way is to increase the temperature of the exhaust stream by modifying the engine output when the particulate filter load reaches a predetermined level.

[0022] The present invention provides catalysts that are to be used in the catalytic converter 104 shown in FIGS. 1A-1 D, or generally as catalysts in any vehicle emission control system, including as a diesel oxidation catalyst, a diesel filter catalyst, an ammonia-slip catalyst, an NSR catalyst, an SCR catalyst, or as a component of a three-way catalyst. The present invention further provides a vehicle emission control system, such as the ones shown in FIGS. 1A-1 D, comprising an emission control catalyst comprising a monolith and a supported catalyst coated on the monolith.

[0023] FIG. 2 is an illustration of a catalytic converter with a cut-away section that shows a substrate 210 onto which supported metal catalysts are coated. The exploded view of the substrate 210 shows that the substrate 210 has a honeycomb structure comprising a plurality of channels into which washcoats containing supported metal catalysts are flowed in slurry form so as to form coating 220 on the substrate 210.

[0024] In one embodiment of the present invention, a single layer of washcoat containing one or more supported metal catalysts is coated on substrate 210. FIGS. 3A-3D illustrate multi-layered, multi-zoned, and multi-brick embodiments of the present invention. In the embodiment of FIG. 3A, coating 220 comprises two washcoat layers 221 , 223 on top of substrate 210. Washcoat layer 221 is the bottom layer that is disposed directly on top of the substrate 210. Washcoat layer 223 is the top layer that is in direct contact with the exhaust stream. Based on their positions relative to the exhaust stream, washcoat layer 223 encounters the exhaust stream before washcoat layer 221.

[0025] In the embodiment of FIG. 3B, coating 220 comprises three washcoat layers 221 , 222, 223 on top of substrate 210. Washcoat layer 221 is the bottom layer that is disposed directly on top of the substrate 210. Washcoat layer 223 is the top layer that is in direct contact with the exhaust stream. Washcoat layer 222 is the middle layer that is disposed in between washcoat layers 221 , 223. The middle layer is also referred to as a buffer layer. Based on their positions relative to the exhaust stream, washcoat layer 223 encounters the exhaust stream before washcoat layers 221 , 222, and washcoat layer 222 encounters the exhaust stream before washcoat layer 221.

[0026] In the embodiment of FIG. 3C, the substrate 210 is a single monolith that has two coating zones 21 OA, 210B. A first washcoat is coated onto a first zone 21 OA and a second washcoat is coated onto a second zone 210B. In the embodiment of FIG. 3D, the substrate 210 includes first and second monoliths 231 , 232, which are physically separate monoliths. A first washcoat is coated onto the first monolith 231 and a second washcoat is coated onto the second monolith 232.

[0027] Embodiments of the nitric oxide oxidation catalyst according to the present invention may be included in a washcoat that is applied to zones or layers of a multi-zoned or multi-layered system, such as the ones illustrated in FIGS. 3A- 3D. In these embodiments, the washcoat containing the NOx oxidation catalyst is coated onto a downstream zone or layer, e.g., downstream zone or monolith in a two-zone , or two-brick system, the bottom layer in a two-layered system, or the middle layer or the bottom layer in a three-layered system. A platinum-based catalyst may be included in one of the other zones or layers. Also, zeolites may be included in any one of the zones, bricks, or layers as a hydrocarbon absorbing component. Zeolites include at least one of ZSM-5 zeolite, beta zeolite, and Y zeolite.

[0028] The nitric oxide oxidation catalyst contains an ion conducting brownmillerite compound modified with an additional transition metal, wherein the catalyst has the general formula

x is a number from 1 to 5, and

y is a number that renders the catalyst substantially charge neutral.

[0029] Exemplary metallic element A includes Ba, Sr, Mg and Ca. Exemplary metallic element B includes Lathanide series (such as Ce, Gd, Yb, Nd) and Zr, Ti, Hf, Ga, Cr, Sc, Al, Nb, Zn, In, Y, and mixtures thereof. Exemplary metallic element C includes Co and Mn.

[0030] In another embodiment, a portion of metallic elements A and/or B of the brownmillerite compound may be partially substituted with one or more metallic elements select from within each respective group of potential metallic elements. In this respect, the brownmillerite structure may be modified as ΑΑΈ2Ο5_, AA'A"B₂0₅, Α2ΒΒΌ5, A₂BB'B"0₅, AA'BBOs, AA'BB'CxO(₅₊y), and variations thereof, wherein A' and A" represent metallic elements which have been substituted for a portion of metallic element A, and B' and B" represent metallic element which have been substituted portion of metallic element B. Exemplary substituted brownmillerite compound include Ba₂Ln_xZr_2-x0₅ and Sr₂Ln_xZr2_-x05. Additional exemplary Brown millerite compounds and their respective oxygen ion conductivities are shown in Table 1 below.

[0031] Table 1 above is taken from Table 1 of K. Kendall, et al., "Recent developments in perovskite-based oxide ion conductors," Solid State Ionics 82 (1995) 215-223.

[0032] In one embodiment, the nitric oxide oxidation catalyst does not include a precious metal such as platinum or palladium. In this respect, the nitric oxide oxidation catalyst may provide a lower cost alternative to precious metal oxidation catalysts. It is expected the non-precious metal nitric oxide oxidation catalyst disclosed herein will exhibit a similar level of nitric oxide oxidation performance.

[0033] The transition metal in the nitric oxide oxidation catalyst may be present in molar ratio from 3:1 to 1 :3 of the total metal in the brownmillerite compound. Preferably, the transition metal is present in a molar ratio of 2:1 to 1 :2 of the total metal in the brownmillerite compound.

[0034] The nitric oxide oxidation catalyst may be synthesized using any suitable process. An exemplary synthesis method is co-precipitation method. In general, the co-precipitation method includes dissolving suitable amounts of the transition metal salts and the brownmillerite metal salt precursors such as nitrates or acetates in water. Optional polymer surfactants such as Poly Vinyl Alcohol ("PVA") or the sodium salt of Polyacrylic Acid ("Na-PAA") may be added to the solution. The metal cations are then precipitated with sodium hydroxide, sodium carbonate, oxalic acid, sodium oxalate or ammonium oxalate, and optionally oxidized with hydrogen peroxide. The resulting metal precipitant is filtered and washed using deionized water 3 or 4 times. Finally, the metal precipitant is dried and calcined at 500°C for 2 hours.

[0035] Alternatively, the NOx oxidation catalyst may be synthesized using the citric acid method. In general, the transition metal and brownmillerite metal salt precursors are dissolved in water with 10% excess of molar amounts of citric acid. Optionally, all or a portion of the citric acid may be substituted with EDTA or a mixture of PVA and sucrose. The mixture is stirred and heated until a viscous gel forms. The viscous gel is dried, processed, and calcined at 500°C for 2 hours.

[0036] A comparative study was carried out to observe the performance of nitric oxide oxidation catalyst. The performance of the nitric oxide oxidation catalyst was compared to a platinum/palladium catalyst, specifically, a 3/1.5% PtPd catalyst on AI₂O₃ (Comp. Sample). The testing conditions included mixing 10mg catalyst with 90 mg of 100 mesh a-alumina and packing the mixture with quartz wool into a flow- through glass U-tube. The catalyst is exposed to a gas mixture of 450ppm NO, 10% O₂, and the remaining balance He, flowing at a rate of 200 seem, in a furnace ramping to 350°C at 10°C/min. Table 2 below shows the performance catalysts and aged catalysts.

TABLE 2

[0037] Table 2 shows the % conversion of NO at 250°C and the maximum peak % conversion at the measured temperature, e.g., sample 1 converted 15% NO at 250°C and had a maximum conversion of 86% NO at 341 °C.

[0038] Although the data above show the fresh NO oxidation catalysts did not quite match the performance of the fresh platinum catalyst at low temperature, i.e., 250°C, the mixed oxide catalysts were shown to be sufficiently effective for oxidizing NO while possessing a lower cost advantage. Additionally, some aged NOx catalysts such as sample 1 showed good aging resistance.

[0039] In general, the nitric oxide oxidation catalysts of Samples 1-5 were prepared in the following manner: [0040] Sample 1 : Dissolve 2.7726g of Co(NO₃)₂»6H₂O, 1.1588 g Zr(C₂H₃02)2(OH)2, 2.0161 g Sr(N0₃)₂, 1 .8620 g of Ιη(ΝΟ₃)3·5Η₂0, and 0.5246 g of PVA (9,000-10,000 MW) in 50ml_ water whilst stirring. Add 9 mL 5M NaOH to reach pH 12. Add 1.68 mL 30% H₂0₂, 0.8663 g Oxalic Acid and 2.5 mL 5M NaOH to bring to pH up to 9. Filter, wash with 60mL water, dry and calcine for 2 hours at 500°C.

[0041] Sample 2: Dissolve 2.3878 g of Co(NO₃)₂»6H₂O, 0.8647 g Zr(C₂H₃O₂)₂(OH)₂, 2.0956 g Ba(C₂H₃O₂)2, 1 .8174 g of Ιη(ΝΟ₃)₃·5Η₂Ο, and 0.2259 g of PVA (9,000-10,000 MW) in 50mL water whilst stirring. Add 6.5 mL 5M NaOH and 2mL 1 M Na₂CO₃ to reach pH 10. Add 1.26 mL 30% H₂O₂, 2.05 g Oxalic Acid and 7.5 mL 5M NaOH to bring to pH up to 9.5. Filter, wash with 60mL water, dry and calcine for 2 hours at 500°C.

[0042] Sample 3: Dissolve 2.3946 g of Co(NO₃)₂»6H₂O, 1.0009 g Zr(C₂H₃O2)₂(OH)2, 2.1016 g Ba(C₂H₃O₂)₂, 1.6082 g of Ιη(ΝΟ₃)₃·5Η₂Ο, and 0.2265 g of PVA (9,000-10,000 MW) in 50mL water whilst stirring. Add 7 mL 5M NaOH and 2mL 1 M Na₂CO₃ to reach pH 1 1. Add 1.26 mL 30% H₂O₂, 0.743 g Oxalic Acid and 2.5 mL 5M NaOH to bring to pH up to 10. Filter, wash with 60mL water, dry and calcine for 2 hours at 500°C.

[0043] Sample 4: Dissolve 3.1712 g of Co(NO₃)₂*6H₂O, 0.8841 g Zr(C₂H₃O₂)₂(OH)₂, 2.7822 g Ba(C₂H₃O₂)2, 2.1201 g of Ιη(ΝΟ₃)₃·5Η₂Ο, and 0.5998 g of PVA (9,000-10,000 MW) in 50mL water whilst stirring. Add 10 mL 5M NaOH and to reach pH 10.5. Add 1.225 mL 30% H₂O₂ and 12mL 1 M Na₂CO₃ to reach a pH 1 1.5. Filter, wash with 80mL water, dry and calcine for 2 hours at 500°C.

[0044] Sample 5: Dissolve 3.955 g of Co(NO₃)₂«6H₂O, 1.0751 g Zr(C₂H₃O₂)₂(OH)₂, 2.6036 g Ba(C₂H₃O₂)2, 2.2580 g of Ιη(ΝΟ₃)₃·5Η₂Ο, and 0.6548 g of PVA (9,000-10,000 MW) in 50mL water whilst stirring. Add 12 mL 5M NaOH and to reach pH 10. Add 1.53 mL 30% H₂O₂ and 1 1.4 mL 1 M Na₂CO₃ to reach a pH 1 1. Filter, wash with 80mL water, dry and calcine for 2 hours at 500°C.

[0045] Sample 6: Dissolve 4.5478 g Co(NO₃)₂»6H₂O, 2.0420 g 1.8794 g Ba(NO₃)₂, 2.6295 g Ιη(ΝΟ₃)₃·5Η₂Ο, 1.2355 g Zr(C₂H₃O₂)₂(OH)₂, and 0.3227 g PVA. Increase the pH with 20ml_ 25% TMAOH to a pH of 10.9. Add 2.2633 g oxalic acid, followed by 4.6 mL 25% TMAOH and1.76 mL 30% H₂O₂.

[0046] Sample 7: Dissolve 6.2780 g Co(NO₃)₂«6H₂O, 1 .8794 g Ba(NO₃)₂, 0.8433 g Ιη(ΝΟ₃)₃·5Η₂Ο, 2.1857 g Ce(NO₃)₃»6H₂O and 0.1980 g PVA in water. Increase the pH with 17mL of 25% TMAOH to a pH of 11.2. Add 1.3277 g oxalic acid, followed by 2.99 mL 30% H₂O₂. Reestablish a pH of 9 with 1 mL TMAOH.

[0047] Sample 8: Dissolve 5.0363 g Co(NO₃)₂*6H₂O, 1.8313 g Sr(NO₃)₂, 2.9123 g Ιη(ΝΟ₃)₃·5Η₂Ο, 1 .3006 ZrO(NO3)2 in water. Add 1.945 mL 30% H₂O₂, 6mL 25% TMAOH and 0.8339g PVA. Add 18mL TMAOH to pH 10.8, followed by 1.861 g oxalic acid to a pH of 9.4. Filter, dry and calcine for 2 hours at 500°C.

[0048] While particular embodiments according to the invention have been illustrated and described above, those skilled in the art understand that the invention can take a variety of forms and embodiments within the scope of the appended claims.

Claims

What is claimed is:

1. A nitric oxide oxidation catalyst having the general formula

A2B₂C_xO(5+y), wherein

A is a metallic element selected from the group consisting of elements from Alkali metals, Alkaline earth metals, and the Lanthanide Series of the lUPAC Periodic Table of the Elements;

x is a number from 1 to 5, and

y is a number that renders the catalyst substantially charge neutral.

2 The catalyst of claim 1 , wherein the catalyst is of the general formula A2BB'C_xO(5₊y), wherein B' comprises substituted metal for a portion of B and is a metallic element selected from the group consisting of elements from the Alkali metals, Alkaline earth metals, transition metals, poor metals, and the Lanthanide Series.

3. The catalyst of claim 1 , wherein the catalyst is of the general formula AA'B2C_xO(₅₊y), wherein A' comprises substituted metal for a portion of A and is a metallic element selected from the group consisting of elements from Alkali metals, Alkaline earth metals and the Lanthanide Series.

4. The catalyst of claim 1 , wherein the catalyst is of the general formula AA'BB'C_xO(5₊y), wherein A' comprises substituted metal for a portion of A and is a metallic element selected from the group consisting of elements from Alkali metals, Alkaline earth metals and the Lanthanide Series, and wherein B' comprises substituted metal for a portion of B and is a metallic element selected from the group consisting of elements from the Alkali metals, Alkaline earth metals, transition metals, poor metals, and the Lanthanide Series.

5. The catalyst of claim 1 , wherein C is selected from Cobalt or Manganese.

6. The catalyst of claim 1 , wherein A is selected from the group consisting of Ba, Sr, and Ca.

7. The catalyst of claim 1 , wherein B is selected from the group consisting of Lathanide series, and Zr, Ti, Hf, Ga, Cr, Sc, Al, Nb, Zn, In, Y.

8. The catalyst of claim 1 , wherein A and B are not platinum or palladium.

9. An engine exhaust system, comprising:

a catalytic oxidation reactor having a nitric oxide oxidation catalyst supported on a substrate, wherein the engine exhaust catalyst has the general formula:

A2B2C_xO(5+y), wherein A is a metallic element selected from the group consisting of elements from Alkali metals, Alkaline earth metals and the Lanthanide Series of the lUPAC Periodic Table of the Elements;

x is a number from 1 to 5, and

y is a number that renders the catalyst substantially charge neutral.

10. The system of claim 9, wherein the substrate comprises multiple washcoat zones or layers, wherein the nitric oxide oxidation catalyst is included in one of the washcoat zones or layers.

1 1. The system of claim 10, further comprising a platinum-based catalyst included in one of the washcoat zones or layers that is different from the zone or layer containing the nitric oxide oxidation catalyst.

12. The system of claim 1 1 , wherein the zone or layer containing the nitric oxide oxidation catalyst encounters an engine exhaust flow after the platinum containing zone or layer.

13. The system of claim 10, wherein at least one of the zones or layers includes zeolites.

14. The system of claim 13, wherein the zeolites include at least one of ZSM-5 zeolite, beta zeolite, and Y zeolite.

15. A method of producing a nitric oxide oxidation catalyst comprising:

preparing a metal salt solution including Cobalt or Manganese and metal salts of the general formula:

A₂B₂0₅

wherein A is a metallic element selected from the group consisting of elements from Alkali metals, Alkaline earth metals and the Lanthanide Series of the lUPAC Periodic Table of the Elements; and B is a metallic element selected from the group consisting of elements from the Alkali metals, Alkaline earth metals, transition metals, poor metals, and the Lanthanide Series;

adding sodium hydroxide, sodium carbonate, or ammonium oxalate to precipitate the metal salts;

oxidizing the metal salts with hydrogen peroxide; and

separating the oxidized metal salts.

16. The method of claim 15, further comprising washing the separated metal salts and then drying; and calcining the separated metal salts that have been washed and dried.