A cerium-zirconium based mixed oxide composition have: (a) a Ce:Zr molar ratio of 1 or less, and (b) a cerium oxide content of 10-50% by weight. The composition has (i) a surface area of at least 18 m.sup.2/g, and a total pore volume as measured by N.sub.2 physisorption of at least 0.11 cm.sup.3/g, after ageing at 1100° C. in an air atmosphere for 6 hours, (ii) a surface area of at least 42 m.sup.2/g, and a total pore volume as measured by N.sub.2 physisorption of at least 0.31 cm.sup.3/g, after ageing at 1000° C. in an air atmosphere for 4 hours, and (iii) Dynamic Oxygen Storage Capacity (D-OSC) value as measured by H.sub.2-TIR of greater than 500 μmol/g at 600° C. after aging at 800° C. in an air atmosphere for 2 hours. A process contacts the exhaust gas with the composition Another process is for preparing the composition.

Subject of the invention is an exhaust gas purification system for a gasoline engine, comprising in consecutive order the following devices: a first three-way-catalyst (TWC1), a gasoline particulate filter (GPF) and a second three-way-catalyst (TWC2), wherein the oxygen storage capacity (OSC) of the GPF is greater than the OSC of the TWC2, wherein the OSC is determined in mg/l of the volume of the device. The invention also relates to methods in which the system is used and uses of the system.

A three-way catalyst article, and its use in an exhaust system for internal combustion engines, is disclosed. The catalyst article for treating exhaust gas comprising: a substrate comprising an inlet end and an outlet end with an axial length L; a first catalytic region comprising a first platinum group metal (PGM) component and a first oxygen storage capacity (OSC) material, wherein the first OSC material has a fresh specific surface area (SSA) of at least 10 m.sup.2/g; and wherein the first OSC material has an SSA difference of no more than 30 m.sup.2/g between the fresh first OSC material and the aged first OSC material.

A cerium-zirconium oxide-based ionic conductor (CZOIC) material including zirconium oxide in an amount ranging from 5 wt. % up to 95 wt. %, cerium oxide in an amount ranging from 95 wt. % to 5 wt. %, and at least one oxide or a rare earth metal in an amount ranging from 30 wt. % or less, based on the overall mass of the CZOIC material. The CZOIC material exhibits a structure comprising one or more expanded unit cells and a plurality of crystallites having ordered nano-domains. The structure of the CZOIC material exhibits a crystal lattice defined by a d-value measured at multiple (hkl) locations using a SAED technique that exhibit distortions, such that the d-values for the same (hkl) location varies from about 2% to about 5% from the d-value measured for a reference cerium-zirconium material at the same (hkl) location.

An exhaust gas control system according to the present disclosure includes: a first exhaust gas control catalyst layer that controls an exhaust gas emitted from an internal combustion engine; and a second exhaust gas control catalyst layer that further controls the exhaust gas that has been controlled by the first exhaust gas control catalyst layer. The second exhaust gas control catalyst layer contains an oxygen storage material. The ratio of the amount (mmol—CO.sub.2/m.sup.2) of base points per specific surface area (m.sup.2/g) of the oxygen storage material to the specific surface area is equal to or less than 4.50×10.sup.−5.

An exhaust gas purification device suppresses a pressure loss increase and includes a honeycomb substrate and inflow cell side catalyst layer. The substrate includes a porous partition wall defining several cells extending from an inflow side end surface to an outflow side end surface. The cells include an inflow and outflow cell adjacent across the wall. The inflow cell has an open inflow side end and sealed outflow side end. The outflow cell has a sealed inflow side end and open outflow side end. The catalyst layer is on an inflow cell side surface in an region extending from the inflow side end positioned 10% or more of the partition wall length. At this position, a filled portion of the inflow cell side catalyst layer pores are 40% or less. The pores are present to a depth of 50% of a thickness of the partition wall.

Disclosed is a catalyst for removing saturated hydrocarbon including an acidic support including porous alumina (Al.sub.2O.sub.3) and having higher acidity than alumina, and an active metal including platinum (Pt) and supported on the acidic support.

In an exhaust gas purification catalyst, a catalytic component (100) containing a first oxide (21), a second oxide (22), and a precious metal (30) is supported on a three-dimensional structure (10); the ratio of the amount of precious metal (30) supported on the first oxide (21) to the total amount of precious metal (30) supported on the first oxide (21) and precious metal (30) supported on the second oxide (22), or the ratio of the amount of precious metal (30) supported on the second oxide (22) to the total amount of precious metal (30) supported on the first oxide (21) and precious metal (30) supported on the second oxide (22) is 70% or more to 100% or less, as measured by an electron probe microanalyzer (EPMA); and the amount of carbon monoxide that the precious metal (30) can adsorb per unit mass is 15 mL/g or more to 100 mL/g or less.

A catalytic converter system having oxygen storage materials is disclosed and methods for determining whether to reactivate oxygen storage materials and monitoring failure events of the oxygen storage materials are also disclosed.

A method of converting nitrogen oxides in a gas to nitrogen by contacting the nitrogen oxides with a nitrogenous reducing agent in the presence of a zeolite catalyst containing at least one transition metal, wherein the zeolite is a small pore zeolite containing a maximum ring size of eight tetrahedral atoms, wherein the at least one transition metal is selected from the group consisting of Cr, Mn, Fe, Co, Ce, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Ag, In, Sn, Re, Ir and Pt.