Abstract:
Synergized platinum group metals (SPGM) oxidation catalyst systems are disclosed. Disclosed SPGM oxidation catalyst systems may include a washcoat with a Cu—Mn spinel structure and an overcoat including PGM, such as palladium (Pd), platinum (Pt), rhodium (Rh), or combinations thereof, supported on carrier material oxides. SPGM systems show significant improvement in abatement of unburned hydrocarbons (HC) and carbon monoxide (CO), and the oxidation of NO to NO 2 , which allows reduction of fuel consumption. Disclosed SPGM oxidation catalyst systems exhibit enhanced catalytic activity compared to PGM oxidation systems, showing that there is a synergistic effect between PGM and Cu—Mn spinel composition within the disclosed SPGM oxidation catalyst systems. Disclosed SPGM oxidation catalyst systems may be available for a plurality of DOC applications.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to U.S. patent application Ser. No. 14/090,861, filed Nov. 26, 2013, entitled System and Methods for Using Synergized PGM as a Three-Way Catalyst. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates generally to low loading of PGM catalyst systems, and, more particularly, to synergized PGM catalyst systems having at least two layers of material composites and for use in diesel oxidation catalyst (DOC) applications, with improved light-off performance and catalytic activity. 
         [0004]    2. Background Information 
         [0005]    Diesel engine exhaust emissions are a heterogeneous mixture including not only carbon monoxide (CO), unburned hydrocarbons (HC) and nitrogen oxides (NO x ), but also condensed phase materials in liquid and solid form known as particulate matter (PM). 
         [0006]    Typically, DOCs provided in diesel engine exhaust systems include platinum group metals (PGM) dispersed on a metal oxide support to convert some or all of these exhaust components into less harmful components. Additional to the conversions of HC, CO and PM, DOCs including PGM promote the oxidation of NO x  to NO 2 . PGMs are used alone or in combination with other noble metals as active components in oxidation catalysts, but noble metals catalyze different oxidation reactions in the catalyst system with different effectiveness. 
         [0007]    Early diesel oxidation catalysts were composed of platinum on a high surface area support and were generally operated at temperatures up to 500° C. to 600° C. More recently, diesel oxidation catalysts have been required to operate at higher temperatures to regenerate the particulate filter that is conventionally located downstream of the oxidation catalyst. 
         [0008]    It is known that mixed platinum (Pt) and palladium (Pd) catalysts offer improved thermal stability as compared with platinum alone and hence the catalyst industry has moved to manufacture Pt/Pd-based diesel oxidation catalysts. However, currently available Pt/Pd-based oxidation catalysts suffer from the problems of poor alloying between the platinum and palladium and a tendency for the size of the metal particles to grow both as the platinum concentration is increased and during use. Both of these factors limit the performance of the catalyst and the possibility for further enhancements in thermal stability. Despite the lower cost of Pd compared to Pt, Pd-based catalyst composites typically show higher light-off temperatures for oxidation of CO and HC, potentially causing a delay in HC and/or CO light-off. Additionally, Pd-based catalyst composites may poison the activity of Pt to convert hydrocarbons and/or oxidize NO x , and may also make the catalyst composite more susceptible to sulfur poisoning when used in diesel engine exhaust systems. 
         [0009]    Rhodium (Rh) is used in catalyst systems for the reduction of NO x  by CO in the presence of excess oxygen. As Rh is a byproduct of the mining of Pt, Rh in any catalyst system must be used effectively during the catalyst system&#39;s operational life. Additionally, as Rh interacts strongly under oxidizing conditions at elevated temperatures, it may diffuse and dissolve so that Rh is only partly recovered when reducing conditions are once again established over the catalyst system. Thus, exposure of a catalyst system including Rh to high temperature conditions may result in the loss of Rh as an effective catalyst material over the life of the catalyst system. 
         [0010]    Therefore, as emissions regulations become more stringent, there is significant interest in developing diesel oxidation catalysts with improved properties for effective utilization and particularly with improved initial activity, improved thermal stability, controlled and stable metal particle size and reduced aging. The continuing goal is to develop DOC including catalyst composites that provide improved light-off performance and removal of residual hydrocarbons, carbon monoxide and NO R . Additionally, as NO emission standards tighten and PGMs become scarce with small market circulation volume, constant fluctuations in price, and constant risk to stable supply, amongst others, there is an increasing need for new compositions for DOC applications including combined catalyst systems with low amounts of PGM catalysts, which may exhibit a synergistic behavior in yielding enhanced catalyst activity under diesel oxidation condition, and which may be cost-effectively manufactured. 
       SUMMARY 
       [0011]    The present disclosure provides synergized platinum group metals (SPGM) oxidation catalyst systems which may exhibit high catalytic activity under DOC light-off condition, and thus improved light-off performance and oxidation of hydrocarbons, carbon monoxide and nitrogen oxide, when compared to PGM systems. 
         [0012]    According to various embodiment, SPGM oxidation catalysts in present disclosure may include at least a substrate, a washcoat, and an overcoat, where substrate may include a plurality of material, such as ceramic material, washcoat may include a Cu—Mn spinel structure supported on plurality of support metal oxides, such as doped ZrO 2 , and overcoat may include a specific PGM material, such as palladium (Pd), or a combination of different PGM materials, such as a bimetallic composite of platinum (Pt) and rhodium (Rh), supported on carrier material oxides, such as alumina. 
         [0013]    In order to compare performance and determine the synergistic influence of Cu—Mn spinel structure with PGM layer, a PGM oxidation catalyst without Cu—Mn spinel structure may be prepared as control sample. The PGM oxidation system may include a ceramic substrate, a washcoat that may include doped ZrO 2 , and an overcoat which may include PGM material, such as Pd or a bimetallic composite of Pt and Rh, supported on carrier material oxides, such as alumina. 
         [0014]    Disclosed SPGM oxidation catalyst and PGM control systems may be prepared using suitable synthesis method, as known in the art, such as co-milling process, and co-precipitation process, amongst others. 
         [0015]    According to one aspect of the present disclosure, to determine the influence on oxidation activity that PGM loadings and Cu—Mn spinel structure may have in the catalytic behavior of both synergized and non-synergized PGM oxidation systems, fresh samples of disclosed SPGM systems and fresh samples of PGM control systems, not including the Cu—Mn spinel structure, may be prepared using different loadings of Pd and Pt/Rh material. In present disclosure, total PGM loading may be as low as 1.0 g/ft 3 . 
         [0016]    According to another aspect of the present disclosure, a DOC standard light-off test may be performed for fresh SPGM and PGM control samples employed in present disclosure. Standard light-off test may be performed under steady state condition for catalytic activity in NO, CO, and HC conversions. Analyses of catalytic activity may be developed for fresh SPGM sample and PGM control samples, including HC and CO light-off temperatures, T 50 , resulting from light-off test procedure employed to verify influence on catalyst activity that may derive from synergistic effect of Cu—Mn spinel and to measure NO to NO 2  conversion. 
         [0017]    SPGM diesel oxidation catalyst of the present disclosure may provide significant improvements in NO conversion under lean operating conditions which is a result of the synergistic effect of the Cu—Mn spinel structure included in both Pd-based and Pt/Rh-based PGM DOCs. Furthermore, disclosed SPGM catalyst systems including Cu—Mn spinel structures may enable catalytic converters employing low amounts of PGM materials. 
         [0018]    According to the foregoing, catalytically active ZPGM material compositions used in present disclosure in the form of Cu—Mn spinel structure as synergizing material may allow high dispersion systems for SPGM oxidation catalyst, which may be manufactured cost-effectively to make them readily available for a plurality of DOC applications, because of the effect on performance provided by ZPGM compositions improving the catalytic layers in diesel oxidation catalysis. 
         [0019]    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 
         [0020]    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. 
           [0021]      FIG. 1  corresponds to an SPGM oxidation catalyst configuration with overcoat of palladium on alumina and washcoat with Cu—Mn spinel on doped Zirconia, referred as SPGM oxidation catalyst system Type 1, according to an embodiment. 
           [0022]      FIG. 2  illustrates a PGM control system configuration with overcoat of palladium on alumina and washcoat of doped Zirconia, referred as PGM system Type 2, according to an embodiment. 
           [0023]      FIG. 3  depicts an SPGM oxidation catalyst configuration with overcoat of platinum and rhodium on alumina and washcoat with Cu—Mn spinel on doped Zirconia, referred as SPGM oxidation catalyst system Type 3, according to an embodiment. 
           [0024]      FIG. 4  shows a PGM control system configuration with overcoat of platinum and rhodium on alumina and washcoat of doped Zirconia, referred as PGM system Type 4, according to an embodiment. 
           [0025]      FIG. 5  represents CO and HC conversion comparisons for fresh samples of SPGM oxidation catalyst system Type 1, and PGM control system Type 2, within a temperature range from about 150° C. to about 500° C. and space velocity (SV) of about 54,000 h −1 , and PGM loading of about 1.0 g/ft 3 , according to an embodiment.  FIG. 5A  shows the CO conversion comparison chart and  FIG. 5B  depicts the HC conversion comparison chart for fresh samples of SPGM oxidation catalyst system Type 1 and PGM control system Type 2. 
           [0026]      FIG. 6  depicts NO conversion and NO 2  production comparisons for fresh samples of SPGM oxidation catalyst system Type 1 and PGM control system Type 2 within a temperature range from about 150° C. to about 500° C. and space velocity (SV) of about 54,000 h −1 , PGM loading of about 1.0 g/ft 3 .  FIG. 6A  represents the NO conversion comparison chart and  FIG. 6B  depicts NO 2  production comparison chart for fresh samples of SPGM oxidation catalyst system Type 1 and PGM control system Type 2. 
           [0027]      FIG. 7  illustrates CO and HC conversion comparisons for fresh samples of SPGM oxidation catalyst system Type 3, and PGM control system Type 4, within a temperature range from about 150° C. to about 500° C. and space velocity (SV) of about 54,000 h −1 , and Pt loading of about 0.5 g/ft 3  and Rh loading of about 0.5 g/ft 3 , according to an embodiment.  FIG. 7A  shows the CO conversion comparison chart and  FIG. 7B  depicts the HC conversion comparison chart for fresh samples of SPGM oxidation catalyst system Type 3 and PGM control system Type 4. 
           [0028]      FIG. 8  shows NO conversion and NO 2  production comparisons for fresh samples of SPGM DOC systems Type 3 and PGM control system Type 4, within a temperature range from about 150° C. to about 500° C. and space velocity (SV) of about 54,000 h −1 , Pt loading of about 0.5 g/ft 3  and Rh loading of about 0.5 g/ft 3 .  FIG. 8A  represents the NO conversion comparison chart and  FIG. 8B  depicts NO 2  production comparison chart for fresh samples of SPGM DOC system Type 3 and PGM control system Type 4. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    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 
       [0030]    As used here, the following terms may have the following definitions: 
         [0031]    “Catalyst system” refers to a system of at least two layers including at least one substrate, a washcoat, and/or an overcoat. 
         [0032]    “Substrate” refers to any material of any shape or configuration that yields a sufficient surface area for depositing a washcoat and/or overcoat. 
         [0033]    “Washcoat” refers to at least one coating including at least one oxide solid that may be deposited on a substrate. 
         [0034]    “Overcoat” refers to at least one coating that may be deposited on at least one washcoat layer. 
         [0035]    “Catalyst” refers to one or more materials that may be of use in the conversion of one or more other materials. 
         [0036]    “Milling” refers to the operation of breaking a solid material into a desired grain or particle size. 
         [0037]    “Co-precipitation” refers to the carrying down by a precipitate of substances normally soluble under the conditions employed. 
         [0038]    “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. 
         [0039]    “Platinum group metals (PGM)” refers to platinum, palladium, ruthenium, iridium, osmium, and rhodium. 
         [0040]    “Zero platinum group (ZPGM) catalyst” refers to a catalyst completely or substantially free of platinum group metals. 
         [0041]    “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. 
         [0042]    “Treating,” “treated,” or “treatment” refers to drying, firing, heating, evaporating, calcining, or mixtures thereof. 
         [0043]    “Diesel oxidation catalyst” refers to a device which utilizes a chemical process in order to break down pollutants from a diesel engine or lean burn gasoline engine in the exhaust stream, turning them into less harmful components. 
         [0044]    “Conversion” refers to the chemical alteration of at least one material into one or more other materials. 
         [0045]    “Spinel” refers to any of various mineral oxides of magnesium, iron, zinc, or manganese in combination with aluminum, chromium, copper or iron with AB 2 O 4  structure. 
         [0046]    “T 50 ” refers to the temperature at which 50% of a material is converted. 
       DESCRIPTION OF THE DRAWINGS 
       [0047]    The present disclosure may provide material compositions including catalyst layer of stoichiometric Cu—Mn spinel at selected base metal loadings on support oxide and their influence on light-off performance of diesel oxidation catalyst (DOC) systems in order to enable suitable catalytic layers, which may ensure high chemical reactivity. Aspects that may be treated in present disclosure may show improvements in the process for overall catalytic conversion capacity for a plurality of synergized PGM (SPGM) oxidation catalyst systems which may be suitable for a plurality of DOC applications and have enhanced catalytic performance when compared with PGM systems. 
         [0048]    Embodiments of the present disclosure incorporate more active components into phase materials possessing DOC properties and provide catalyst performance comparison of disclosed SPGM systems and PGM control systems that may include different palladium (Pd) loadings, or platinum (Pt)/rhodium (Rh) loadings within the overcoat layer. 
         [0049]    According to embodiments in the present disclosure, an SPGM oxidation catalyst may be configured with a washcoat including stoichiometric Cu—Mn spinel with doped Zirconia support oxide, an overcoat including a PGM catalyst, such as Pd with alumina-based support, or Pt/Rh material composite with alumina-based support, and suitable ceramic substrate, here referred as SPGM oxidation catalyst system Type 1 and SPGM oxidation catalyst system Type 3, respectively. According to other embodiments in the present disclosure, PGM control systems may be configured with washcoat layer including doped Zirconia support oxide, an overcoat including PGM catalyst, such as such as Pd with alumina-based support, or Pt/Rh material composite with alumina-based support, and suitable ceramic substrate, here referred as PGM control system Type 2 and PGM control system Type 4, respectively. 
         [0050]    SPGM Oxidation Catalyst and PGM Control Catalyst Configurations 
         [0051]      FIG. 1  shows oxidation catalyst configuration  100 , here referred as SPGM oxidation catalyst system Type 1, according to an embodiment. 
         [0052]    As shown in  FIG. 1 , SPGM oxidation catalyst system Type 1 may include at least substrate  102 , washcoat  104 , and overcoat  106 , where washcoat  104  may include a Cu—Mn spinel structure supported on doped Zirconia and overcoat  106  may include PGM catalyst material supported on carrier material oxides. 
         [0053]    According to embodiments in present disclosure, substrate  102  materials for SPGM catalyst system Type 1 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  and its type and shape may be apparent to one of ordinary skill in the art. According to the present disclosure, preferred substrate  102  may be a ceramic substrate. 
         [0054]    Washcoat  104  for SPGM oxidation catalyst system Type 1 may include a Cu—Mn stoichiometric spinel, Cu 1.0 Mn 2.0 O 4 , on support oxide of doped Zirconia. According to present disclosure, suitable material for disclosed washcoat  104  may be Nb 2 O 5 —ZrO 2 . 
         [0055]    Overcoat  106  for SPGM oxidation catalyst system Type 1 may include a PGM catalyst, such as palladium (Pd), Platinum (Pt), Rhodium (Rh), and combinations thereof, which may be supported on carrier material oxides, such as doped aluminum oxide, zirconium oxide, doped Zirconia, titanium oxide, tin oxide, silicon dioxide, zeolite, and mixtures thereof. In present disclosure, disclosed overcoat  106  may include suitable PGM catalyst of Pd supported on alumina. 
         [0056]      FIG. 2  illustrates PGM system configuration  200 , here referred as PGM control system Type 2, according to an embodiment. 
         [0057]    As shown in  FIG. 2 , PGM control system Type 2 may include at least substrate  102 , washcoat  202 , and an overcoat  106 , where washcoat  202  may include doped Zirconia and overcoat  206  may include PGM catalyst material supported on carrier material oxides. 
         [0058]    According to embodiments in present disclosure, substrate  102  materials for PGM control system Type 2 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  may be a ceramic substrate. 
         [0059]    Washcoat  202  for PGM control system Type 2 may include support oxides such as zirconium oxide or doped Zirconia. According to the present disclosure, suitable material for disclosed washcoat  202  may be Nb 2 O 5 —ZrO 2 . 
         [0060]    Overcoat  106  for PGM control system Type 2 may include a PGM catalyst, such as palladium (Pd), Platinum (Pt), Rhodium (Rh), and combinations thereof, which may be supported on carrier material oxides, such as doped aluminum oxide, zirconium oxide, doped Zirconia, titanium oxide, tin oxide, silicon dioxide, zeolite, and mixtures thereof. In present disclosure, disclosed overcoat  106  may include suitable PGM catalyst of Pd supported on alumina. 
         [0061]      FIG. 3  depicts oxidation catalyst configuration  300 , here referred as SPGM oxidation catalyst system Type 3, according to an embodiment. 
         [0062]    As shown in  FIG. 3 , SPGM oxidation catalyst system Type 3 may include at least substrate  102 , washcoat  104 , and overcoat  302 , where washcoat  104  may include a Cu—Mn spinel structure supported on doped Zirconia and overcoat  302  may include PGM catalyst material supported on carrier material oxides. 
         [0063]    According to embodiments in present disclosure, substrate  102  materials for SPGM catalyst system Type 3 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  and its type and shape may be apparent to one of ordinary skill in the art. According to the present disclosure, preferred substrate  102  may be a ceramic substrate. 
         [0064]    Washcoat  104  for SPGM oxidation catalyst system Type 3 may include a Cu—Mn stoichiometric spinel, Cu 1.0 Mn 2.0 O 4 , on support oxide of doped Zirconia. According to present disclosure, suitable material for disclosed washcoat  104  may be Nb 2 O 5 —ZrO 2 . 
         [0065]    Overcoat  302  for SPGM oxidation catalyst system Type 3 may include a PGM catalyst, such as palladium (Pd), Platinum (Pt), Rhodium (Rh), and combinations thereof, which may be supported on carrier material oxides, such as doped aluminum oxide, zirconium oxide, doped Zirconia, titanium oxide, tin oxide, silicon dioxide, zeolite, and mixtures thereof. In present disclosure, disclosed overcoat  302  may include suitable PGM catalyst of Pt/Rh supported on alumina. 
         [0066]      FIG. 4  illustrates PGM system configuration  400 , here referred as PGM control system Type 4, according to an embodiment. 
         [0067]    As shown in  FIG. 4 , PGM control system Type 4 may include at least substrate  102 , washcoat  202 , and an overcoat  302 , where washcoat  202  may include doped Zirconia and overcoat  302  may include PGM catalyst material supported on carrier material oxides. 
         [0068]    According to embodiments in present disclosure, substrate  102  materials for PGM control system Type 4 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  may be a ceramic substrate. 
         [0069]    Washcoat  202  for PGM control system Type 4 may include support oxides such as zirconium oxide or doped Zirconia. According to the present disclosure, suitable material for disclosed washcoat  202  may be Nb 2 O 5 —ZrO 2 . 
         [0070]    Overcoat  302  for PGM control system Type 4 may include a PGM catalyst, such as palladium (Pd), Platinum (Pt), Rhodium (Rh), and combinations thereof, which may be supported on carrier material oxides, such as doped aluminum oxide, zirconium oxide, doped Zirconia, titanium oxide, tin oxide, silicon dioxide, zeolite, and mixtures thereof. In present disclosure, disclosed overcoat  302  may include suitable PGM catalyst of Pt/Rh supported on alumina. 
         [0071]    The synergistic effect of selected base metal loadings of Cu—Mn stoichiometric spinel, Cu 1.0 Mn 2.0 O 4 , may be verified preparing samples of the disclosed SPGM oxidation catalyst system and PGM control system, which may be tested under light-off conditions. 
         [0072]    DOC Standard Light-Off Test Procedure 
         [0073]    DOC standard light-off test under steady state condition may be performed employing a flow reactor in which temperature may be increased from about 100° C. to about 500° C. at a rate of about 40° C./min, feeding a gas composition of about 100 ppm of NO x , 1,500 ppm of CO, about 4% of CO 2 , about 4% of H 2 O, about 14% of O 2 , and about 430 ppm of C 3 H 6 , at space velocity (SV) of about 54,000 h −1 . During DOC light-off test neither N 2 O nor NH 3  may form. 
         [0074]    The following examples are intended to illustrate the scope of the disclosure. It is to be understood that other procedures known to those skilled in the art may alternatively be used. Examples in the present disclosure may be prepared according to the plurality of DOC system configurations previously disclosed. 
       Examples 
     Example #1 
     SPGM Oxidation Catalyst System Type 1 
       [0075]    Example #1 may illustrate preparation of fresh samples of SPGM oxidation catalyst system Type 1 having oxidation catalyst configuration  100 . 
         [0076]    The preparation of washcoat  104  may begin by milling Nb 2 O 5 —ZrO 2  support oxide to make aqueous slurry. The Nb 2 O 5 —ZrO 2  support oxide may have Nb 2 O 5  loadings of about 15% to about 30% by weight, preferably about 25%, and ZrO 2  loadings of about 70% to about 85% by weight, preferably about 75%. 
         [0077]    The Cu—Mn solution may be prepared by mixing for about 1 to 2 hours, an appropriate amount of Mn nitrate solution (Mn(NO 3 ) 2 ) and Cu nitrate solution (CuNO 3 ). Subsequently, Cu—Mn nitrate solution may be mixed with Nb 2 O 5 —ZrO 2  support oxide slurry for about 2 to 4 hours, where Cu—Mn nitrate solution may be precipitated on Nb 2 O 5 —ZrO 2  support oxide aqueous slurry. A suitable base solution, such as sodium hydroxide (NaOH) solution, sodium carbonate (Na 2 CO 3 ) solution, ammonium hydroxide (NH 4 OH) solution, and tetraethyl ammonium hydroxide (TEAH) solution, amongst others, may be added to adjust the pH of the slurry to a suitable range. The precipitated Cu—Mn/Nb 2 O 5 —ZrO 2  slurry may be aged for a period of time of about 12 to 24 hours under continued stirring at room temperature. 
         [0078]    Subsequently, the precipitated slurry may be coated on ceramic substrate  102 . The aqueous slurry of Cu—Mn/Nb 2 O 5 —ZrO 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 suitable ceramic substrate  102 . Subsequently, after deposition on ceramic substrate  102  of the suitable loadings of Cu—Mn/Nb 2 O 5 —ZrO 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. 
         [0079]    Overcoat  106  may include a combination of Pd 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 Pd nitrate may be mixed with the aqueous slurry of alumina with a loading within a range from about 0.5 g/ft 3  to about 25.0 g/ft 3 , preferably about 1.0 g/ft 3  in present disclosure. After mixing of Pd and alumina slurry, Pd may be locked down with an appropriate amount of one or more base solutions, such as sodium hydroxide (NaOH) solution, sodium carbonate (Na 2 CO 3 ) solution, ammonium hydroxide (NH 4 OH) solution, and tetraethyl ammonium hydroxide (TEAH) solution, amongst others. Then, the resulting slurry may be aged from about 12 to 24 hours for subsequent coating as overcoat  106  on washcoat  104 , dried and fired at about 550° C. for about 4 hours. 
       Example #2 
     SGM Control System Type 2 
       [0080]    Example #2 may illustrate preparation of fresh samples of PGM control system Type 2 having PGM system configuration  200 . 
         [0081]    The preparation of washcoat  202  may begin by milling Nb 2 O 5 —ZrO 2  support oxide to make aqueous slurry. The Nb 2 O 5 —ZrO 2  support oxide may have Nb 2 O 5  loadings of about 15% to about 30% by weight, preferably about 25% and ZrO 2  loadings of about 70% to about 85% by weight, preferably about 75%. Washcoat  202  particle size (d 50 ) may be adjusted within a range of about 4 μm to about 5 μm. 
         [0082]    Subsequently, washcoat  202  slurry may be coated on substrate  102 . Washcoat  202  slurry may be deposited on suitable ceramic substrate  102  to form washcoat  202 , employing vacuum dosing and coating systems. In the present disclosure, a plurality of capacities of washcoat  202  loadings may be coated on suitable ceramic substrate  102 . Washcoat  202  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. 
         [0083]    Overcoat  106  may include a combination of Pd 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 Pd nitrate may be mixed with the aqueous slurry of alumina with a loading within a range from about 0.5 g/ft 3  to about 25.0 g/ft 3 , preferably about 1.0 g/ft 3  in present disclosure. After mixing of Pd and alumina slurry, Pd may be locked down with an appropriate amount of one or more base solutions, such as sodium hydroxide (NaOH) solution, sodium carbonate (Na 2 CO 3 ) solution, ammonium hydroxide (NH 4 OH) solution, and tetraethyl ammonium hydroxide (TEAH) solution, amongst 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. 
         [0084]    DOC Light-off performance for SPGM oxidation catalyst system Type 1 and PGM control system Type 2 may be compared by preparing fresh samples for each of the catalyst formulations and configurations to measure/analyze the synergistic effect of adding Cu—Mn spinel to PGM catalyst materials, which may be used in DOC applications, and to show the resulting improvement in oxidation activity. In order to compare light-off performance and DOC activity of disclosed SPGM DOC system Type 1 and PGM control system Type 2, DOC standard light-off tests may be performed. 
       Example #3 
     SPGM Oxidation Catalyst System Type 3 
       [0085]    Example #3 may illustrate preparation of fresh samples of SPGM oxidation catalyst system Type 3 having oxidation catalyst configuration  300 . 
         [0086]    The preparation of washcoat  104  may begin by milling Nb 2 O 5 —ZrO 2  support oxide to make aqueous slurry. The Nb 2 O 5 —ZrO 2  support oxide may have Nb 2 O 5  loadings of about 15% to about 30% by weight, preferably about 25% and ZrO 2  loadings of about 70% to about 85% by weight, preferably about 75%. 
         [0087]    The Cu—Mn solution may be prepared by mixing for about 1 to 2 hours, an appropriate amount of Mn nitrate solution (Mn(NO 3 ) 2 ) and Cu nitrate solution (CuNO 3 ). Subsequently, Cu—Mn nitrate solution may be mixed with Nb 2 O 5 —ZrO 2  support oxide slurry for about 2 to 4 hours, where Cu—Mn nitrate solution may be precipitated on Nb 2 O 5 —ZrO 2  support oxide aqueous slurry. A suitable base solution, such as sodium hydroxide (NaOH) solution, sodium carbonate (Na 2 CO 3 ) solution, ammonium hydroxide (NH 4 OH) solution, and tetraethyl ammonium hydroxide (TEAH) solution, amongst others, may be added to adjust the pH of the slurry to a suitable range. The precipitated Cu—Mn/Nb 2 O 5 —ZrO 2  slurry may be aged for a period of time of about 12 to 24 hours under continued stirring at room temperature. 
         [0088]    Subsequently, the precipitated slurry may be coated on ceramic substrate  102 . The aqueous slurry of Cu—Mn/Nb 2 O 5 —ZrO 2  may be deposited on 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 . Subsequently, after deposition on ceramic substrate  102  of the suitable loadings of Cu—Mn/Nb 2 O 5 —ZrO 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. 
         [0089]    Overcoat  302  may include a combination of Pt and Rh on alumina-based support. The preparation of overcoat  302  may begin by milling the alumina-based support oxide separately to make aqueous slurry. Subsequently, a solution of Pt and Rh nitrates may be mixed with the aqueous slurry of alumina with a loading within a range from about 0.5 g/ft 3  to about 25.0 g/ft 3 , preferably about 0.5 g/ft 3  of Pt and about 0.5 g/ft 3  of Rh. After mixing of Pt/Rh and alumina slurry, Pt/Rh may be locked down with an appropriate amount of one or more base solutions, such as sodium hydroxide (NaOH) solution, sodium carbonate (Na 2 CO 3 ) solution, ammonium hydroxide (NH 4 OH) solution, and tetraethyl ammonium hydroxide (TEAH) solution, amongst others. Then, the resulting slurry may be aged from about 12 to 24 hours for subsequent coating as overcoat  106  on washcoat  104 , dried and fired at about 550° C. for about 4 hours. 
       Example #4 
     PGM Control System Type 4 
       [0090]    Example #4 may illustrate preparation of fresh samples of PGM control system Type 4 having PGM system configuration  400 . 
         [0091]    The preparation of washcoat  202  may begin by milling Nb 2 O 5 —ZrO 2  support oxide to make aqueous slurry. The Nb 2 O 5 —ZrO 2  support oxide may have Nb 2 O 5  loadings of about 15% to about 30% by weight, preferably about 25% and ZrO 2  loadings of about 70% to about 85% by weight, preferably about 75%. Washcoat  202  particle size (d 50 ) may be adjusted within a range of about 4 μm to about 5 μm. 
         [0092]    Subsequently, washcoat  202  slurry may be coated on substrate  102 . Washcoat  202  slurry may be deposited on suitable ceramic substrate  102  to form washcoat  202 , employing vacuum dosing and coating systems. In the present disclosure, a plurality of capacities of washcoat  202  loadings may be coated on suitable ceramic substrate  102 . Washcoat  202  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. 
         [0093]    Overcoat  302  may include a combination of Pt and Rh on alumina-based support. The preparation of overcoat  302  may begin by milling the alumina-based support oxide separately to make aqueous slurry. Subsequently, a solution of Pt and Rh nitrates may be mixed with the aqueous slurry of alumina with a loading within a range from about 0.5 g/ft 3  to about 25.0 g/ft 3 , preferably about 0.5 g/ft 3  of Pt and about 0.5 g/ft 3  of Rh. After mixing of Pt/Rh and alumina slurry, Pt/Rh may be locked down with an appropriate amount of one or more base solutions, such as sodium hydroxide (NaOH) solution, sodium carbonate (Na 2 CO 3 ) solution, ammonium hydroxide (NH 4 OH) solution, and tetraethyl ammonium hydroxide (TEAH) solution, amongst others. Then, the resulting slurry may be aged from about 12 to 24 hours for subsequent coating as overcoat  106  on washcoat  104 , dried and fired at about 550° C. for about 4 hours. 
         [0094]    DOC Light-off performance for SPGM oxidation catalyst system Type 3 and PGM control system Type 4 may be compared by preparing fresh samples for each of the catalyst formulations and configurations to measure/analyze the synergistic effect of adding Cu—Mn spinel to PGM catalyst materials, which may be used in DOC applications, and to show the resulting improvement in oxidation activity. In order to compare light-off performance and DOC activity of disclosed SPGM DOC system Type 3 and PGM control system Type 4, DOC standard light-off tests may be performed. 
         [0095]    Analysis of Oxidation Property for Fresh Samples of SPGM Oxidation Catalyst and PGM Control Systems 
         [0096]      FIG. 5  represents CO and HC conversion comparisons  500  for fresh samples of SPGM oxidation catalyst system Type 1, and PGM control system Type 2, respectively, under light-off condition, at a temperature range from about 150° C. to about 500° C. and space velocity (SV) of about 54,000 h −1 , according to an embodiment.  FIG. 5A  shows the CO conversion comparison curves  502  and  FIG. 5B  depicts the HC conversion comparison curves  504  for fresh samples of SPGM oxidation catalyst system Type 1 and PGM control system Type 2. 
         [0097]    Accordingly, as can be seen in  FIG. 5A , conversion curve  506  represents CO conversion for SPGM oxidation catalyst system Type 1 fresh samples and conversion curve  508  depicts CO conversion for PGM control system Type 2 fresh samples, respectively. It may be observed in  FIG. 5A  that CO T 50 , for fresh samples of SPGM oxidation catalyst system Type 1 is about 235° C., while CO T 50 , for fresh samples of PGM control system Type 2 is about 325° C. CO light off temperature of Synergized PGM samples is lower than that of PGM control samples, showing enhanced CO oxidation performance of SPGM Type 1. Even though PGM samples present desirable oxidation activity in CO conversion, synergized PGM samples significantly surpass PGM samples in regards to CO conversion, verifing the synergistic effect between Cu—Mn spinel and Pd. 
         [0098]    As can be seen in  FIG. 5B , conversion curve  510  represents HC conversion for SPGM oxidation catalyst system Type 1 fresh samples and conversion curve  512  depicts HC conversion for PGM control system Type 2 fresh samples, respectively. It may be observed in  FIG. 5B  that HC T 50 , for fresh samples of SPGM oxidation catalyst system Type 1 is about 235° C., while HC T 50 , for PGM control system Type 2 is about 350° C. HC light off temperature of synergized PGM samples is lower than that of PGM control samples showing enhanced HC oxidation activity of SPGM oxidation catalyst system Type 1 verifying the synergistic effect between Cu—Mn spinel and Pd. 
         [0099]    The resulting levels of CO and HC oxidation improvement for SPGM oxidation catalyst system Type 1 may indicate that the synergistic effect between Cu—Mn spinel and Pd may deliver improved oxidation catalyst with ultra low Pd loading of about 1.0 gift′ for DOC application. 
         [0100]      FIG. 6  depicts NO conversion and NO2 production comparisons  600  for fresh samples of SPGM oxidation catalyst system Type 1 and PGM control system Type 2 at a temperature range from about 150° C. to about 500° C. and space velocity (SV) of about 54,000 h −1  according to an embodiment.  FIG. 6A  represents NO conversion comparison  602  and  FIG. 6B  depicts NO2 production comparison  604  for fresh samples of SPGM oxidation catalyst system Type 1 and PGM control system Type 2. 
         [0101]    Accordingly, as can be seen in  FIG. 6A , conversion curve  606  represents NO conversion for SPGM oxidation catalyst system Type 1 fresh samples and conversion curve  608  depicts NO conversion for PGM control system Type 2 fresh samples under DOC light-off condition, respectively. 
         [0102]    As may be seen in  FIG. 6B , concentration profile curve  610  represents NO 2  production for SPGM oxidation catalyst system Type 1 and concentration profile curve  612  depicts NO 2  production for PGM control system Type 2 under DOC light-off condition, respectively. 
         [0103]    It may be observed in  FIG. 6A  that NO conversion for SPGM oxidation catalyst system Type 1 reach a maximum of about 34% conversion at about 390° C., while PGM control system Type 2 fresh samples reach maximum NO conversion of about 18%, at about 465° C. 
         [0104]    SPGM oxidation catalyst system Type 1 present a significantly higher catalytic activity in NO oxidation than PGM control system Type 2. A significantly high improvement of about 83% in NO x  conversion may indicate that SPGM oxidation catalyst system Type 1 may deliver enhanced oxidation activity verifying synergistic effect of Cu—Mn with pd. 
         [0105]    As may be seen in  FIG. 6B , NO 2  production from concentration profile curve  610  is about 35 ppm at about 390° C., while NO 2  production from concentration profile curve  612  is about 18 ppm, at about 465° C. By considering the concentration of NO in feed stream (100 ppm), the comparison of NO 2  concentration from  FIG. 6B  with NO conversion from  FIG. 6A  confirms NO convert to NO 2  and no other products such as NH 3  or N 2 O formed. 
         [0106]    As may be noted, SPGM oxidation catalyst system Type 1 may deliver a higher level of NO oxidation to NO 2  production level than that of PGM control system Type 2. The increased NO 2  production and the resulting level of NO conversion for SPGM oxidation catalyst system Type 1 may indicate that the synergistic effect provided by Cu—Mn spinel may also deliver improved NO oxidation activity under diesel oxidation conditions and Pd loading of about 1.0 g/ft 3 . These results may confirm that improvement is derived due to the synergistic effect between Cu—Mn spinel and Pd, which may also enable synergized PGM diesel oxidation catalyst systems for a plurality of engine applications operating under real conditions. Higher level of NO oxidation may be obtained by using higher loading of Pd in OC layer. 
         [0107]      FIG. 7  illustrates CO and HC conversion comparisons  700  for fresh samples of SPGM oxidation catalyst system Type 3, and PGM control system Type 4, respectively, under DOC light-off condition, at a temperature range from about 150° C. to about 500° C. and space velocity (SV) of about 54,000 h −1  according to an embodiment.  FIG. 7A  shows the CO conversion comparison curves  702  and  FIG. 7B  depicts the HC conversion comparison curves  704  for fresh samples of SPGM oxidation catalyst system Type 3 and PGM control system Type 4, respectively. 
         [0108]    Accordingly, as can be seen in  FIG. 7A , conversion curve  706  represents CO conversion for SPGM oxidation catalyst system Type 3 and conversion curve  708  depicts CO conversion for PGM control system Type 4 under DOC light-off condition, respectively. It may be observed in  FIG. 7A  that CO T 50 , for SPGM oxidation catalyst system Type 3 is about 245° C. while CO T 50  for PGM control system Type 4 is about 265° C. CO light off temperature of synergized PGM samples is lower than that of PGM control samples, showing enhanced CO oxidation performance of SPGM oxidation catalyst system Type 3. Even though PGM samples present a significant oxidation activity in CO conversion, synergized PGM samples surpass PGM samples in regards to CO conversion verifying the synergistic effect between Cu—Mn spinel and Pt/Rh. 
         [0109]    As can be seen in  FIG. 7B , conversion curve  710  represents HC conversion for SPGM oxidation catalyst system Type 3 and conversion curve  712  depicts HC conversion for PGM control system Type 4 under DOC light-off condition, respectively. It may be observed in  FIG. 7B  that HC T 50  for SPGM oxidation catalyst system Type 3 is about 250° C., while HC T 50  for PGM control system Type 4 is about 285° C. HC light off temperature of synergized PGM samples is lower than that of PGM control sample showing enhanced HC oxidation performance. Even though PGM sample present significant oxidation activity in HC conversion, synergized PGM samples surpass PGM samples in regards to HC conversion verifying the synergistic effect between Cu—Mn spinel and Pt/Rh. 
         [0110]    The resulting levels of CO and HC oxidation improvement for SPGM oxidation catalyst system Type 3 may indicate that the synergistic effect between Cu—Mn spinel and Pt/Rh may deliver improved oxidation catalyst with ultra low PGM loading of about 1.0 g/ft 3  for DOC application. 
         [0111]      FIG. 8  depicts NO conversion and NO2 production comparisons  800  for fresh samples of SPGM oxidation catalyst system Type 3 and PGM control system Type 4, under DOC light-off condition and space velocity (SV) of about 54,000 h −1  according to an embodiment.  FIG. 8A  represents NO conversion comparison  802  and  FIG. 8B  depicts NO2 production comparison  804  for fresh samples of SPGM oxidation catalyst Type 3 and PGM control system Type 4. 
         [0112]    Accordingly, as can be seen in  FIG. 8A , conversion curve  806  represents NO conversion for SPGM oxidation catalyst Type 3 and conversion curve  808  depicts NO conversion for PGM control system Type 4 under DOC light-off condition, respectively. 
         [0113]    As may be seen in  FIG. 8B , concentration profile curve  810  represents NO 2  production for SPGM oxidation catalyst system Type 3 and concentration profile curve  812  depicts NO 2  production for PGM control system Type 4 under DOC light-off condition, respectively. 
         [0114]    It may be observed in  FIG. 8A  that NO conversion for SPGM oxidation catalyst system Type 3 fresh samples reach a maximum of about 32% conversion at about 385° C., while PGM control system Type 4 fresh samples reach maximum NO x  conversion of about 19%, at about 460° C. 
         [0115]    SPGM oxidation catalyst system Type 3 presents a higher catalytic activity in NO oxidation than PGM control system Type 4 sample. An improvement of about 55% in NO x  conversion may indicate that SPGM oxidation catalyst system Type 3 may deliver enhanced activity in NO oxidation. 
         [0116]    As may be seen in  FIG. 8B , NO 2  production from concentration profile curve  810  is about 35 ppm at about 385° C., while NO 2  production from concentration profile curve  812  is about 20 ppm, at about 460° C. These results may verify that catalytic behavior of fresh samples of SPGM oxidation catalyst system Type 3 surpasses the catalytic behavior of samples of PGM control system Type 4. DOC activity for NO 2  production is increased by the presence of Cu—Mn spinel in SPGM oxidation catalyst system Type 3. 
         [0117]    As may be noted, SPGM oxidation catalyst system Type 3 may deliver a higher level of NO oxidation to NO 2  production level than that of PGM control system Type 4. The increased NO 2  production and the resulting level of NO conversion for SPGM oxidation catalyst system Type 3 may indicate that the synergistic effect provided by Cu—Mn spinel may also deliver improved NO oxidation activity under diesel oxidation conditions and Pt/Rh loading of about 1.0 g/ft 3 . These results may confirm that improvement is derived due to the synergistic effect between Cu—Mn spinel and PGM, which may also enable synergized PGM diesel oxidation catalyst systems for a plurality of engine applications operating under real conditions. Higher level of NO oxidation may be obtained by using higher loading of Pt/Rh in OC layer. 
         [0118]    The catalytic oxidation of SPGM oxidation catalyst systems Type 1 and Type 3 has been carried out using these catalysts under DOC light-off conditions to show and verify that DOC catalytic performance of the disclosed systems increased when compared with oxidation activity of PGM control system Type 2 and Type 4. Both SPGM systems have shown to be significantly active catalyst for diesel oxidation as determined by their corresponding light-off performance compare to same PGM systems with no Cu—Mn composition. In all disclosed SPGM systems may be observed that the presence of Cu—Mn spinel may be associated with the enhanced oxidation activity not shown by the non-synergized PGM systems. The disclosed SPGM oxidation catalyst systems may provide a basis for a plurality of applications in lean burn engine operations. 
         [0119]    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.