Synergized platinum group metals (SPGM) with ultra-low PGM loadings employed as underfloor (UF) three-way catalyst (TWC) systems with varied material compositions and configurations are disclosed. SPGM UF catalysts in which ZPGM compositions of binary and ternary spinel structures supported onto support oxides are coupled with commercialized PGM close-coupled (CC) catalysts and tested under Federal Test Procedure FTP-75 within TGDI and PI engines. The performance of the TWC systems including commercialized PGM CC and SPGM UF (with ultra-low PGM loadings) catalysts is compared to the performance of commercialized PGM CC and PGM UF catalysts. The disclosed TWC systems indicate that SPGM UF TWC catalytic performance is comparable or even exceeds high PGM-based conventional TWC catalysts, with reduced tailpipe emissions.

A catalyst for direct decomposition of NO and NO.sub.2 to N.sub.2 and O.sub.2 has a CoFe.sub.2O.sub.4 spinel doped with potassium cations. The catalyst has high activity and good selectivity for N.sub.2 production, when potassium cations are loaded at a density of about 0.9 weight percent. Methods for making the catalyst include wet impregnation of a CoFe.sub.2O.sub.4 spinel with a solution of potassium cations, such as a KOH solution.

A catalyst for direct decomposition of NO and NO.sub.2 to N.sub.2 and O.sub.2 has a CoFe.sub.2O.sub.4 spinel doped with potassium cations. The catalyst has high activity and good selectivity for N.sub.2 production, when potassium cations are loaded at a density of about 0.9 weight percent. Methods for making the catalyst include wet impregnation of a CoFe.sub.2O.sub.4 spinel with a solution of potassium cations, such as a KOH solution.

A catalyst for storing nitrogen oxides (NO.sub.x) in an exhaust gas from a lean burn engine comprising a NO.sub.x storage material and a substrate, wherein the NO.sub.x storage material comprises a NO.sub.x storage component and an NO oxidation promoter on a support material, wherein the NO oxidation promoter is manganese or an oxide, hydroxide or carbonate thereof.

Active catalysts for the treatment of a low temperature exhaust gas stream are provided containing palladium oxides dispersed on a spinel oxide for the direct, lean removal of nitrogen oxides from the exhaust gas stream. The low temperature (from about 400 C. to about 650 C.), direct decomposition is accomplished without the need of a reductant molecule. In one example, PdO may be dispersed on a surface of a metal oxide support, such as Co.sub.3O.sub.4 spinel oxide, synthesized using wet impregnation techniques. The PdO/Co.sub.3O.sub.4 catalyst system converts nitric oxide to nitrogen gas with high product specificity, avoiding the production of a significant concentration of the undesirable N.sub.2O product.

Active catalysts for the treatment of a low temperature exhaust gas stream are provided containing potassium (K) dispersed on a spinel oxide for the direct, lean removal of nitrogen oxides from the exhaust gas stream. The low temperature (from about 400 C. to about 650 C.), direct decomposition is accomplished without the need of a reductant molecule. In one example, K may be dispersed on a surface of a metal oxide support, such as NiFe.sub.2O.sub.4 spinel oxide, synthesized using wet impregnation techniques. The K/NiFe.sub.2O.sub.4 catalyst system converts nitric oxide to nitrogen gas with high product specificity, up to 100%, avoiding the production of a significant concentration of the undesirable N.sub.2O product.

Active catalysts for the treatment of a low temperature exhaust gas stream are provided containing potassium (K) dispersed on a spinel oxide for the direct, lean removal of nitrogen oxides from the exhaust gas stream. The low temperature (from about 400 C. to about 650 C.), direct decomposition is accomplished without the need of a reductant molecule. In one example, K may be dispersed on a surface of a metal oxide support, such as NiFe.sub.2O.sub.4 spinel oxide, synthesized using wet impregnation techniques. The K/NiFe.sub.2O.sub.4 catalyst system converts nitric oxide to nitrogen gas with high product specificity, up to 100%, avoiding the production of a significant concentration of the undesirable N.sub.2O product.

Active catalysts for the treatment of a low temperature exhaust gas stream are provided containing palladium oxides dispersed on a spinel oxide for the direct, lean removal of nitrogen oxides from the exhaust gas stream. The low temperature (from about 400 C. to about 650 C.), direct decomposition is accomplished without the need of a reductant molecule. In one example, PdO may be dispersed on a surface of a metal oxide support, such as Co.sub.3O.sub.4 spinel oxide, synthesized using wet impregnation techniques. The PdO/Co.sub.3O.sub.4 catalyst system converts nitric oxide to nitrogen gas with high product specificity, avoiding the production of a significant concentration of the undesirable N.sub.2O product.

A monolithic catalyst for simultaneous removal of NO.sub.x and carbon particles, especially from off-gases of carbon power plants contains the monolith is made from acid-proof austenitic steel. The catalyst is a two-phase one; moreover, it contains the phases NiFe.sub.2O.sub.4 and Fe.sub.2O.sub.3(Mh) with spinel structure, and these phases form microcrystallites, additionally containing Mn. The manner of production of the monolithic catalyst for simultaneous removal of NO.sub.x and carbon particles, especially from off-gases of carbon power plants depends on the monolith is subject to oxidation after which the resulting oxide layers are washed with the solution of nickel salts; later the monolith is baked in the oxidising atmosphere with the view to inserting nickel ions into the oxide layer; finally this obtained oxide layers are subject to reduction.

Active catalysts for the treatment of a low temperature exhaust gas stream are provided containing copper oxides dispersed on a spinel oxide for the direct, lean removal of nitrogen oxides from the exhaust gas stream. The low temperature, direct decomposition is accomplished without the need of a reductant molecule. In one example, CuO.sub.x may be dispersed as a monolayer on a metal oxide support, such as Co.sub.3O.sub.4 spinel oxide, synthesized using an incipient wetness impregnation technique. The CuO.sub.x/Co.sub.3O.sub.4 catalyst system converts nitric oxide to nitrogen gas with high product specificity, avoiding the production of a significant concentration of the undesirable N.sub.2O product.