A method of reducing nitrogen oxides in exhaust gas of an internal combustion engine by selective catalytic reduction (SCR) comprises contacting the exhaust gas also containing ammonia and oxygen with a catalytic converter comprising a catalyst (2) comprising at least one crystalline small-pore molecular sieve catalytically active component (Z.sub.M,I) having a maximum ring opening of eight tetrahedral basic building blocks, which crystalline small-pore molecular sieve catalytically active component (Z.sub.M,I) comprising mesopores.

A cold start catalyst is disclosed. The cold start catalyst comprises a zeolite catalyst and a supported platinum group metal catalyst. The zeolite catalyst comprises a base metal, a noble metal, and a zeolite. The supported platinum group metal catalyst comprises one or more platinum group metals and one or more inorganic oxide carriers. The invention also includes an exhaust system comprising the cold start catalyst. The cold start catalyst and the process result in improved NO.sub.x storage and NO.sub.x conversion, improved hydrocarbon storage and conversion, and improved CO oxidation through the cold start period.

Uses for a new crystalline molecular sieve designated SSZ-105 are disclosed. SSZ-105 is synthesized using N,N-dimethylpiperidinium cations as a structure directing agent. SSZ-105 is a disordered aluminosilicate molecular sieve comprising at least one intergrown phase of an ERI framework type molecular sieve and an LEV framework type molecular sieve.

The current invention refers to the LNT and the SCR catalysts designed for combined LNT-SCR applications. LNT catalysts are based on proton-conducting oxides of fluorite structure, namely Ca (Sr)LaCe (Zr, Pr) mixed oxides in which up to 40 mol-% of lanthanum is replaced by calcium and/or strontium, and up to 66 mol-% of cerium is replaced by zirconium and/or praseodymium, further combined with PtPd or PtPdRh precious metal components. SCR catalysts are Cu/zeolite modified by citrate treatment or CuCe, MnCe or CoCe/modified zeolite.

Provided is a system for treating an exhaust gas comprising a first SCR catalyst zone comprising vanadium loaded on a metal oxide selected from TiO.sub.2, ZrO.sub.2, SiO.sub.2, CeO.sub.2, and Al.sub.2O.sub.3; and a second SCR catalyst zone comprising a copper loaded small-pore molecular sieve, wherein the first SCR catalyst zone is disposed upstream of the second SCR catalyst zone with respect to normal exhaust gas flow through the system. Also provided is a method for using the system to treat exhaust gas.

Provided is a system for treating an exhaust gas comprising a first SCR catalyst zone comprising vanadium loaded on a metal oxide selected from TiO.sub.2, ZrO.sub.2, SiO.sub.2, CeO.sub.2, and Al.sub.2O.sub.3; and a second SCR catalyst zone comprising a copper loaded small-pore molecular sieve, wherein the first SCR catalyst zone is disposed upstream of the second SCR catalyst zone with respect to normal exhaust gas flow through the system. Also provided is a method for using the system to treat exhaust gas.

Provided is a method for reducing N.sub.2O emissions in an exhaust gas comprising contacting an exhaust gas containing NH.sub.3 and an inlet NO concentration with an SCR catalyst composition containing small pore zeolite having an SAR of about 3 to about 15 and having about 1-5 wt. % of an exchanged transition metal.

The present invention relates to a composition comprising a non-zeolitic oxidic material comprising alumina; an 8-membered ring pore zeolitic material comprising one or more of copper and iron, wherein the framework structure of the zeolitic material comprises a tetravalent element Y, a trivalent element X and oxygen, wherein the molar ratio of Y:X, calculated as YO.sub.2X.sub.2O.sub.3, is in the range of from 2:1 to 40:1; wherein at least part of the outer surface of the zeolitic material is covered by a layer comprising the non-zeolitic oxidic material; wherein Y comprises one or more of Si, Sn, Ti, Zr and Ge and X comprises one or more of Al, B, In and Ga.

The present invention relates to a composition comprising a non-zeolitic oxidic material comprising alumina; an 8-membered ring pore zeolitic material comprising one or more of copper and iron, wherein the framework structure of the zeolitic material comprises a tetravalent element Y, a trivalent element X and oxygen, wherein the molar ratio of Y:X, calculated as YO.sub.2X.sub.2O.sub.3, is in the range of from 2:1 to 40:1; wherein at least part of the outer surface of the zeolitic material is covered by a layer comprising the non-zeolitic oxidic material; wherein Y comprises one or more of Si, Sn, Ti, Zr and Ge and X comprises one or more of Al, B, In and Ga.