A lean NO.sub.x trap catalyst and its use in an emission treatment system for internal combustion engines is disclosed. The lean NO.sub.x trap catalyst comprises a first layer, a second layer, and a third layer.

An exhaust gas purifier is disposed in an exhaust gas passage of an engine, and includes: a DPF for capturing PM contained in exhaust gas; an SCR catalyst provided downstream of the DPF in a direction of flow of the exhaust gas, and for reducing NO.sub.x contained in the exhaust gas for purification in the presence of NH.sub.3; an injection unit provided between the DPF and the SCR catalyst, and for supplying urea to the SCR catalyst so as to supply NH.sub.3 to the SCR catalyst; and an AMOX provided downstream of the SCR catalyst in the direction of flow of the exhaust gas, and for removing NH.sub.3 having passed through the SCR catalyst. The DPF does not contain Pt or Pd, and contains Rh. The AMOX contains Pt.

An oxidation catalyst composite, methods, and systems for the treatment of exhaust gas emissions from a diesel engine are described. More particularly, an oxidation catalyst composite including a first washcoat comprising a zeolite, Pt, and first refractory metal oxide support containing manganese, a second washcoat comprising a second refractory metal oxide support, a Pt component and a Pd component, and a third washcoat comprising palladium and a rare earth oxide component is described.

Composites of mixed metal oxides for an exhaust gas purifying catalyst comprise the following co-precipitated materials by weight of the composite: zirconia in an amount in the range of 55-99%; titania in an amount in the range of 1-25%; a promoter and/or a stabilizer in an amount in the range of 0-20%. These composites are effective as supports for platinum group metals (PGMs), in particular rhodium.

A catalyst for gasoline engine exhaust gas after-treatment, comprising Pt and optionally at least one other platinum group metal on a hydrothermal stable support material which is coated onto a gasoline particulate filter. The catalyst oxidizes particulate matter trapped in the gasoline particulate filter under low temperature and abates NO.sub.x, CO and HC. Also a process for preparing the catalyst is disclosed, and a method for after-treatment of gasoline engine exhaust gas using the catalyst is disclosed.

An exhaust gas purifier is disposed in an exhaust gas passage of an engine, and includes: a DPF for capturing PM contained in exhaust gas; an SCR catalyst provided downstream of the DPF in a direction of flow of the exhaust gas, and for reducing NO.sub.x contained in the exhaust gas for purification in the presence of NH.sub.3; an inj ection unit provided between the DPF and the SCR catalyst, and for supplying urea to the SCR catalyst so as to supply NH.sub.3 to the SCR catalyst; and an AMOX provided downstream of the SCR catalyst in the direction of flow of the exhaust gas, and for removing NH.sub.3 having passed through the SCR catalyst. The DPF does not contain Pt or Pd, and contains Rh. The AMOX contains Pt.

An oxidation catalyst composite, methods, and systems for the treatment of exhaust gas emissions from a diesel engine are described. More particularly, an oxidation catalyst composite including a first washcoat comprising a zeolite, Pt, and first refractory metal oxide support containing manganese, a second washcoat comprising a second refractory metal oxide support, a Pt component and a Pd component, and a third washcoat comprising palladium and a rare earth oxide component is described.

A method for preparing a metal-organic framework (MOF) comprising contacting one or more of a rare earth metal ion component with one or more of a tetratopic ligand component, sufficient to form a rare earth-based MOF for controlling moisture in an environment. A method of moisture control in an environment comprising adsorbing and/or desorbing water vapor in an environment using a MOF, the MOF including one or more of a rare earth metal ion component and one or more of a tetratopic ligand component. A method of controlling moisture in an environment comprising sensing the relative humidity in the environment comprising a MOF; and adsorbing water vapor on the MOF if the relative humidity is above a first level, sufficient to control moisture in an environment.

An exhaust gas-purifying three-way catalyst containing: (i) base material particles of a Nd-solid dissolved zirconia-based complex oxide comprising Nd and Zr as constituent metal elements in the following mass proportions: TABLE-US-00001 ZrO.sub.2 50 to 75% by mass; and Nd.sub.2O.sub.3 25 to 50% by mass, in terms of oxides; and (ii) Pd catalyst particles supported on the base material particles, wherein the Nd-solid dissolved zirconia-based complex oxide further contains at least one or more rare earth elements selected from the group consisting of yttrium, scandium, lanthanum, and praseodymium, as a constituent metal element, in an amount of a total of more than 0% by mass to 20% by mass or less in terms of an oxide.

This exhaust gas purification catalyst device includes an upper layer which includes first carrier particles and rhodium, and a lower layer which includes second carrier particles, and the upper layer includes a rhodium enriched area in the range a, from the downstream end in the exhaust gas flow to greater than 50% and up to 80% of the upper layer length, and a range b from the upper layer top surface less than 20 m in the depth direction. The rhodium enriched area contains at least 50% and less than 100% of all the rhodium in the upper layer.