A honeycomb structure includes: a honeycomb structure body including a plurality of cells; and a plugging portion to alternately plug open end parts of the plurality of cells on one side as an inflow side of the exhaust gas and open end parts on the other side as an outflow side of the exhaust gas. The partition wall is loaded, on the side of the outflow cells, with an oxidation catalyst made of a transition metal oxide to oxidize NO gas or an oxidation catalyst made of a transition metal oxide loaded at CeO.sub.2 to oxidize NO gas. The partition wall has porosity of 70% or less, the oxidation catalyst has a particle diameter of more than 1 m and less than 50.0 m, and the loading amount of the oxidation catalyst is 5.0 g/L or more and 50 g/L or less.

A process for preparing a zeolitic material containing YO.sub.2 and X.sub.2O.sub.3, where Y and X represent a tetravalent element and a trivalent element, respectively, is described. The process includes (1) a step of preparing a mixture containing one or more structure directing agents, seed crystals, and a first zeolitic material containing YO.sub.2 and X.sub.2O.sub.3 and having FAU-, GIS-, MOR-, and/or LTA-type framework structures; and (2) a step of heating the mixture for obtaining a second zeolitic material containing YO.sub.2 and X.sub.2O.sub.3 and having a different framework structure than the first zeolitic material. The mixture prepared in (1) and heated in (2) contains 1000 wt % or less of H.sub.2O based on 100 wt % of YO.sub.2 in the framework structure of the first zeolitic material. A zeolitic material obtainable and/or obtained by the process and its use are also described.

A method for the removal of nitrous oxide from off gas by direct decomposition or by selective catalytic reduction in presence of a reducing agent, comprising the steps of contacting the gas directly or together with the reducing agent or a precursor thereof with a catalyst comprising an Fe-AEI zeolite material essentially free of alkali metal ions (Alk) and having the following molar compositions:

SiO.sub.2:o Al.sub.2O.sub.3:p Fe:q Alk

wherein o is in the range from 0.001 to 0.2;

wherein p is in the range from 0.001 to 0.2;

wherein Alk is one or more of alkali ions and wherein q is less than 0.02.

Disclosed herein are emission treatment systems, articles, and methods for selectively reducing NOx compounds. The systems include a hydrogen generator, a hydrogen selective catalytic reduction (H.sub.2-SCR) article, and one or more of a diesel oxidation catalyst (DOC) and/or a lean NOx trap (LNT) and/or a low temperature NOx adsorber (LTNA). Certain articles may comprise a zone coated substrate and/or a layered coated substrate and/or an intermingled coated substrate of one or more of the H.sub.2-SCR and/or DOC and/or LNT and/or LTNA catalytic compositions.

Catalyst and use of the catalyst comprising a molecular sieve belonging to the ABC-6 framework family with disorder in the ABC stacking sequence essentially composed of double-six-ring periodic building units and having a mole ratio of silicon oxide to aluminum oxide from about 8 to about 60.

A method of manufacturing an exhaust gas-purifying catalyst comprising: moving a gas-flow control tool from a first position where the gas-flow control tool faces the first end face with the slurry in the reservoir interposed therebetween and is spaced apart from the slurry in the reservoir to a second position where the gas-flow control tool faces the first end face with a distance from the first end face shorter than that in the first position, in a period during which the slurry flows from the first end face's side toward the second end face's side, the gas-flow control tool being configured to generate a distribution of linear velocities of gas flows when the gas-flow control tool faces the first end face and gas is passed therethrough toward the first end face.

Disclosed herein are emission treatment systems, articles, and methods for selectively reducing NOx compounds. The systems include a hydrogen generator, a hydrogen selective catalytic reduction (H.sub.2-SCR) article, and one or more of a diesel oxidation catalyst (DOC) and/or a lean NOx trap (LNT) and/or a low temperature NOx adsorber (LTNA). Certain articles may comprise a zone coated substrate and/or a layered coated substrate and/or an intermingled coated substrate of one or more of the H.sub.2-SCR and/or DOC and/or LNT and/or LTNA catalytic compositions.

Provided is an SCR catalyst article comprising a substrate having thereon a second catalyst composition downstream of a first catalyst composition, wherein the first and second catalyst compositions are different and wherein the first catalyst composition is an SCR catalyst composition and the second catalyst composition comprises an Fe-loaded small- or medium-pore molecular sieve, the small- or medium-pore molecular sieve having a silica-to-alumina ratio (SAR) of from 6 to 19.

Disclosed are a composite zeolite SCR catalyst, a preparation method therefor and use thereof. The composite zeolite SCR catalyst comprises a Cu-based zeolite and a first hydrogen-type zeolite; the composite zeolite SCR catalyst has a NO.sub.x removal efficiency of more than or equal to 80% at more than or equal to 300? C.; the composite zeolite SCR catalyst is subjected to hydrothermal treatment at 750-950? C. for 10-16 h, and the hydrothermally treated composite zeolite SCR catalyst has a NO.sub.x removal efficiency of more than or equal to 60% at more than or equal to 300? C. The composite zeolite SCR catalyst of the present application is used in the technology of selective catalytic reduction on nitrogen oxides with ammonia, and the composite zeolite SCR catalyst has simple composition, low preparation cost, great catalytic performance and good hydrothermal stability.

The present invention provides a process for the treatment of a NO.sub.X-containing gas stream, said NO.sub.X-containing gas stream containing NO2 and NO in a molar ratio of NO.sub.2:NO of at least 1:1, to remove at least a portion of the NO.sub.X contained therein, said process comprising: i) providing an additional gas stream comprising NO to the NO.sub.X-containing gas stream, such that the molar ratio of NO.sub.2:NO in the NO.sub.X-containing gas stream is reduced to be less than 1:1; and ii) then passing the NO.sub.X-containing gas stream through a catalyst bed comprising a deNO.sub.X catalyst under suitable conditions to reduce the level of NO.sub.X in the gas stream and thus produce a deNO.sub.X treated gas stream, said deNO.sub.X treated gas stream containing a reduced amount of NO.sub.X.