Disclosed are zeolite catalysts having the CHA crystal structure with a low silica to alumina ratio, as well as articles and systems incorporating the catalysts and methods for their preparation and use. The catalysts can be used to reduce NOx from exhaust gas streams, particularly those emanating from gasoline or diesel engines.

A process for preparing a catalyst comprising a zeolitic material comprising copper, the process comprising (i) preparing an aqueous mixture comprising water, a zeolitic material comprising copper, a source of copper other than the zeolitic material comprising copper, and a non-zeolitic oxidic material selected from the group consisting of alumina, silica, titania, zirconia, ceria, a mixed oxide comprising one or more of Al, Si, Ti, Zr, and Ce and a mixture of two or more thereof; (ii) disposing the mixture obtained in (i) on the surface of the internal walls of a substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the substrate extending therethrough; and optionally drying the substrate comprising the mixture disposed thereon; (iii) calcining the substrate obtained in (ii).

An exhaust gas purification catalyst device comprising a base material and a catalyst coating layer provided on the base material, wherein the catalyst coating layer contains zeolite particles, inorganic oxide particles other than the zeolite particles, and a catalyst precious metal, and the ratio d.sub.ZEO/d.sub.OX between the average particle diameter d.sub.ZEO of the zeolite particles and the average particle diameter d.sub.OX of the inorganic oxide particles other than the zeolite particles is 3.4 or less.

A three-way catalyst article, and its use in an exhaust system for compressed natural gas engines, is disclosed. The catalyst article for treating exhaust gas from compressed natural gas (CNG) engine comprising: a substrate comprising an inlet end, an outlet end with an axial length L; a first catalytic region beginning at the outlet end and extending for less than the axial length L, wherein the first catalytic region comprises a first zeolite; and a second catalytic region beginning at the inlet end, wherein the second catalytic region comprises a second platinum group metal (PGM) component, a second oxygen storage capacity (OSC) material, and a second inorganic oxide; wherein the second PGM component is selected from the group consisting of palladium, platinum, rhodium or a combination thereof.

Disclosed herein is a continuous process for preparing zeolitic material with a CHA-type framework structure comprising SiO.sub.2 and X.sub.2O.sub.3 and the zeolitic material so-obtained. The processes comprises (i) preparing a mixture comprising one or more sources of SiO.sub.2, one or more sources of X.sub.2O.sub.3, seed crystals, one or more tetraalkylammonium cation R.sup.5R.sup.6R.sup.7R.sup.8N.sub.+-containing compounds as structure directing agent, and a liquid solvent system; (ii) continuously feeding the mixture prepared in (i) into a continuous flow reactor at a liquid hourly space velocity; and (iii) crystallizing the zeolitic material with a CHA-type framework structure from the mixture in the continuous flow reactor.

The present disclosure provides catalyst compositions capable of reducing nitrogen oxide (NO.sub.x) emissions in engine exhaust. The catalyst compositions include metal ion-exchanged zeolites having a domain size of less than about 1500 Ångstroms (Å), a crystallographic strain of less than about 0.7%, or both. Further provided are catalyst articles coated with such compositions, processes for preparing such catalyst compositions and articles, an exhaust gas treatment system including such catalytic articles, and methods for reducing NO.sub.x in an exhaust gas stream using such catalytic articles and systems.

Denitration catalyst unit, comprising two or more platy catalyst elements, wherein the platy catalyst element has an edge located on gas-inflow side, an edge located on gas-outflow side and edges located on either side of the platy catalyst element, the platy catalyst elements are piled so as to align the edges located on gas-inflow side and the edges located on either side of the platy catalyst elements respectively, each of the platy catalyst elements alternately has more than one flat part in the shape of a flat plate and more than one concavo-convex part in the shape of platy convex strips on the upper and lower surfaces, the platy convex strips are parallel to one another and are obliquely disposed at an angle θ of not less than 50° and not more than 85° to an extending direction of the edge located on gas-inflow side of the platy catalyst element so that a ridge of the platy convex strip on the upper surface of one of the platy catalyst elements intersects with a ridge of the platy convex strip on the lower surface of another of the platy catalyst elements adjacent, at least one of the intersection points is within a range x of more than 0 mm and less than 25 mm inward from the edge located on gas-inflow side of the platy catalyst element.

A method of coating a substrate with a foam is described. The method comprises: (a) introducing a foam into a substrate comprising a plurality of channels through open ends of the channels at a first end of the substrate; and (b) applying at least one of (i) a vacuum to open ends of the channels at a second end of the substrate and (ii) a pressure to the open ends of the channels at the first end of the substrate; wherein the foam comprises a particulate material, and wherein the foam is particle stabilized.

A gas purification catalyst device comprises: a substrate; and one or more catalyst layers on the substrate. Among the one or more catalyst layers, at least one catalyst layer contains both Cu-CHA-type zeolite particles and iron-supporting metal oxide particles in which iron is supported on metal oxide particles.

In certain exemplary embodiments, an air purifier comprises a housing defining an enclosure and having an air entrance and an air exit; a particulate filter; a NCCO filter material configured to adsorb and decompose at least one gaseous pollutant; an AOG configured to generate at least one oxidant; an oxidant remover configured to remove at least one oxidant; a fan unit configured to generate airflow from the air entrance to the air exit; wherein the particulate filter, the NCCO filter material, the AOG, the oxidant remover and the fan unit are positioned within the enclosure such that during operation, a flow of air passes from the air entrance to the air exit through the particulate filter and the NCCO filter material along a direction of the flow of air. In certain embodiments, the air purifier may ensure safety to users while efficiency in removing contaminants can be greatly improved.