The present invention relates to a method for preparing an alumina supported perovskite type oxide composition, to an alumina supported perovskite type oxide composition and to the use of such an alumina supported perovskite type oxide composition in catalytic systems in emission control applications.

A multilayer supported oxidative coupling of methane (OCM) catalyst composition (support, first single oxide layer, one or more mixed oxide layers, optional second single oxide layer) characterized by formula A.sub.aZ.sub.bE.sub.cD.sub.dO.sub.x/support; A is alkaline earth metal; Z is first rare earth element; E is second rare earth element; D is redox agent/third rare earth element; the first, second, third rare earth element are not the same; a=1.0; b=0.1-10.0; c=0.1-10.0; d=0-10.0; x balances oxidation states; first single oxide layer (Z.sub.b1O.sub.x1, b1=0.1-10.0; x1 balances oxidation states) contacts support and one or more mixed oxide layers; one or more mixed oxide layers (A.sub.a2Z.sub.b2E.sub.c2D.sub.d2O.sub.x2, a2=1.0; b2=0.1-10.0; c2=0.1-10.0; d2=0-10.0; x2 balances oxidation states; A.sub.aZ.sub.bE.sub.cD.sub.dO.sub.x and A.sub.a2Z.sub.b2E.sub.c2D.sub.d2O.sub.x2 are different) contacts first single oxide layer and optionally second single oxide layer, and second single oxide layer (AO), when present, contacts one or more mixed oxide layers and optionally first single oxide layer.

A multilayer supported oxidative coupling of methane (OCM) catalyst composition (support, first single oxide layer, one or more mixed oxide layers, optional second single oxide layer) characterized by formula A.sub.aZ.sub.bE.sub.cD.sub.dO.sub.x/support; A is alkaline earth metal; Z is first rare earth element; E is second rare earth element; D is redox agent/third rare earth element; the first, second, third rare earth element are not the same; a=1.0; b=0.1-10.0; c=0.1-10.0; d=0-10.0; x balances oxidation states; first single oxide layer (Z.sub.b1O.sub.x1, b1=0.1-10.0; x1 balances oxidation states) contacts support and one or more mixed oxide layers; one or more mixed oxide layers (A.sub.a2Z.sub.b2E.sub.c2D.sub.d2O.sub.x2, a2=1.0; b2=0.1-10.0; c2=0.1-10.0; d2=0-10.0; x2 balances oxidation states; A.sub.aZ.sub.bE.sub.cD.sub.dO.sub.x and A.sub.a2Z.sub.b2E.sub.c2D.sub.d2O.sub.x2 are different) contacts first single oxide layer and optionally second single oxide layer, and second single oxide layer (AO), when present, contacts one or more mixed oxide layers and optionally first single oxide layer.

A multilayer supported oxidative coupling of methane (OCM) catalyst composition (alpha-Al.sub.2O.sub.3 support, first single oxide layer, one or more mixed oxide layers, optional second single oxide layer) characterized by formula A.sub.aZ.sub.bE.sub.cD.sub.dO.sub.x/alpha-Al.sub.2O.sub.3; A is alkaline earth metal; Z is first rare earth element; E is second rare earth element; D is redox agent/third rare earth element; the first, second, third rare earth element are not the same; a=1.0; b=0.1-10.0; c=0.1-10.0; d=0-10.0; x balances oxidation states; first single oxide layer (Z.sub.b1O.sub.x1, b1=0.1-10.0; x1 balances oxidation states) contacts alpha-Al.sub.2O.sub.3 support and one or more mixed oxide layers; one or more mixed oxide layers (A.sub.a2Z.sub.b2E.sub.c2D.sub.d2O.sub.x2, a2=1.0; b2=0.1-10.0; c2=0.1-10.0; d2=0-10.0; x2 balances oxidation states; A.sub.aZ.sub.bE.sub.cD.sub.dO.sub.x and A.sub.a2Z.sub.b2E.sub.c2D.sub.d2O.sub.x2 are different) contacts first single oxide layer and optionally second single oxide layer, and second single oxide layer (AO), when present, contacts one or more mixed oxide layers and optionally first single oxide layer.

A multilayer supported oxidative coupling of methane (OCM) catalyst composition (alpha-Al.sub.2O.sub.3 support, first single oxide layer, one or more mixed oxide layers, optional second single oxide layer) characterized by formula A.sub.aZ.sub.bE.sub.cD.sub.dO.sub.x/alpha-Al.sub.2O.sub.3; A is alkaline earth metal; Z is first rare earth element; E is second rare earth element; D is redox agent/third rare earth element; the first, second, third rare earth element are not the same; a=1.0; b=0.1-10.0; c=0.1-10.0; d=0-10.0; x balances oxidation states; first single oxide layer (Z.sub.b1O.sub.x1, b1=0.1-10.0; x1 balances oxidation states) contacts alpha-Al.sub.2O.sub.3 support and one or more mixed oxide layers; one or more mixed oxide layers (A.sub.a2Z.sub.b2E.sub.c2D.sub.d2O.sub.x2, a2=1.0; b2=0.1-10.0; c2=0.1-10.0; d2=0-10.0; x2 balances oxidation states; A.sub.aZ.sub.bE.sub.cD.sub.dO.sub.x and A.sub.a2Z.sub.b2E.sub.c2D.sub.d2O.sub.x2 are different) contacts first single oxide layer and optionally second single oxide layer, and second single oxide layer (AO), when present, contacts one or more mixed oxide layers and optionally first single oxide layer.

A cerium-zirconium-aluminum-based composite material, a cGPF catalyst and a preparation method thereof are provided. The cerium-zirconium-aluminum-based composite material adopts a stepwise precipitation method, firstly preparing an aluminum-based pre-treated material, then coprecipitating the aluminum-based pre-treated material with zirconium and cerium sol, and finally roasting at high temperature to obtain the cerium-zirconium-aluminum-based composite material. The cerium-zirconium-aluminum-based composite material has better compactness and higher density, and when it is used in cGPF catalyst, it occupies a smaller volume of pores on the catalyst carrier, such that cGPF catalyst has lower back pressure and better ash accumulation resistance, which is beneficial to large-scale application of cGPF catalyst.

A cerium-zirconium-aluminum-based composite material, a cGPF catalyst and a preparation method thereof are provided. The cerium-zirconium-aluminum-based composite material adopts a stepwise precipitation method, firstly preparing an aluminum-based pre-treated material, then coprecipitating the aluminum-based pre-treated material with zirconium and cerium sol, and finally roasting at high temperature to obtain the cerium-zirconium-aluminum-based composite material. The cerium-zirconium-aluminum-based composite material has better compactness and higher density, and when it is used in cGPF catalyst, it occupies a smaller volume of pores on the catalyst carrier, such that cGPF catalyst has lower back pressure and better ash accumulation resistance, which is beneficial to large-scale application of cGPF catalyst.

An object of the present invention is to provide means for releasing oxygen at a temperature lower than conventional means in an exhaust gas purification catalyst. A Ce—Zr composite oxide is provided, which has a crystallite diameter of 6.5 nm or less and a BET specific surface area of 90 m.sup.2/g or more.

An object of the present invention is to provide means for releasing oxygen at a temperature lower than conventional means in an exhaust gas purification catalyst. A Ce—Zr composite oxide is provided, which has a crystallite diameter of 6.5 nm or less and a BET specific surface area of 90 m.sup.2/g or more.

The present invention relates to a mixed oxide of aluminium, of zirconium, of cerium, of lanthanum and optionally of at least one rare-earth metal other than cerium and lanthanum that makes it possible to prepare a catalyst that retains, after severe ageing, a good thermal stability and a good catalytic activity. The invention also relates to the process for preparing this mixed oxide and also to a process for treating exhaust gases from internal combustion engines using a catalyst prepared from this mixed oxide.