The present invention relates to a catalytic article for purifying an exhaust gas containing nitrogen oxides, which comprises a first region containing a vanadium-based SCR catalyst, a second region containing a metal-promoted molecular sieve catalyst, and a third region containing a vanadium-based SCR catalyst, wherein at least part of the second region is located downstream of at least part of the first region and upstream of at least part of the third region in the exhaust gas flow direction, provided that no part of the second region is located upstream of the first region or downstream of the third region. The present invention also relates to a method and a system for treatment of an exhaust gas containing nitrogen oxides by selective catalytic reduction using the catalytic article.

The present invention relates to a catalytic article for purifying an exhaust gas containing nitrogen oxides, which comprises a first region containing a vanadium-based SCR catalyst, a second region containing a metal-promoted molecular sieve catalyst, and a third region containing a vanadium-based SCR catalyst, wherein at least part of the second region is located downstream of at least part of the first region and upstream of at least part of the third region in the exhaust gas flow direction, provided that no part of the second region is located upstream of the first region or downstream of the third region. The present invention also relates to a method and a system for treatment of an exhaust gas containing nitrogen oxides by selective catalytic reduction using the catalytic article.

An object of the present invention is to provide an exhaust gas purifying catalyst composition and an exhaust gas purifying catalyst, each of which has improved exhaust gas purification performance, and the present invention provides an exhaust gas purifying catalyst composition containing a Ce-based oxide particle, a CeZr-based composite oxide particle, an Al-based oxide particle, and a noble metal element, wherein an amount of Ce in terms of CeO.sub.2 in the Ce-based oxide particle is 90% by mass or more based on a mass of the Ce-based oxide particle, wherein an amount of Ce in terms of CeO.sub.2 in the CeZr-based composite oxide particle is 5% by mass or more and 90% by mass or less based on a mass of the CeZr-based composite oxide particle, wherein the Ce-based oxide particle has an average particle size of 0.10 ?m or more and 15 ?m or less, and wherein an amount of the Ce-based oxide particle in the exhaust gas purifying catalyst composition is 2.0% by mass or more and 30% by mass or less based on a mass of the exhaust gas purifying catalyst composition.

An object of the present invention is to provide an exhaust gas purification catalyst with improved exhaust gas purification performance, and in order to achieve such an object, the present invention provides an exhaust gas purification catalyst (1A) including a substrate (10) and a catalyst layer (20A) provided on the substrate (10), wherein a content of aluminum element in terms of oxide and a content of barium element in a first layer (21) of the catalyst layer (20A) are 15% by mass or more and 3% by mass or more, respectively, based on a mass of the first layer (21), and wherein a total of a content of zirconium element in terms of oxide and a content of a rare earth element in terms of oxide, a content of aluminum element in terms of oxide, and a content of barium element in a second layer (22) of the catalyst layer (20A) are 80% by mass or more, less than 15% by mass, and less than 3% by mass, respectively, based on a mass of the second layer (22).

An object of the present invention is to provide an exhaust gas purification catalyst with improved exhaust gas purification performance, and in order to achieve such an object, the present invention provides an exhaust gas purification catalyst (1A) including a substrate (10) and a catalyst layer (20A) provided on the substrate (10), wherein a content of aluminum element in terms of oxide and a content of barium element in a first layer (21) of the catalyst layer (20A) are 15% by mass or more and 3% by mass or more, respectively, based on a mass of the first layer (21), and wherein a total of a content of zirconium element in terms of oxide and a content of a rare earth element in terms of oxide, a content of aluminum element in terms of oxide, and a content of barium element in a second layer (22) of the catalyst layer (20A) are 80% by mass or more, less than 15% by mass, and less than 3% by mass, respectively, based on a mass of the second layer (22).

An object of the present invention is to provide an exhaust gas purification catalyst composition and an exhaust gas purification catalyst, each of which utilizes a phosphorus capturing material that enables solving a problem of MAO, and in order to achieve the object, a complex oxide containing Mg, Ba, and Al, wherein the complex oxide has a spinel-type crystal structure, and wherein a molar ratio of a Mg content to an Al content in the complex oxide is 0.010 or more and 0.25 or less is used as a phosphorus capturing material.

The exhaust gas purification device includes a substrate, a first catalyst layer, and a second catalyst layer. The substrate includes an upstream end and a downstream end. The first catalyst layer contains first catalyst particles and lies on the substrate across a first region extending between the upstream end and a first position. The first position is at a first distance from the upstream end toward the downstream end. The second catalyst layer contains second catalyst particles and lies on the first catalyst layer across the first region. The second catalyst layer is provided with pores. Pore connectivity of the second catalyst layer is 5% to 35%. A mean value of areas of the pores of the second catalyst layer in a cross-sectional backscattered electron image of the second catalyst layer may be 0.7 ?m.sup.2 to 9.0 ?m.sup.2.

An object of the present invention is to provide an exhaust gas purifying catalyst composition and an exhaust gas purifying catalyst, each of which has improved exhaust gas purification performance, and the present invention provides an exhaust gas purifying catalyst composition containing a Ce-based oxide particle, a CeZr-based composite oxide particle, and a noble metal element, wherein the Ce-based oxide particle contains at least one type of additional element selected from Al, Mg, La, Pr, Y, and Nd, and wherein an amount of the at least one type of additional element in terms of oxide in the Ce-based oxide particle is 0.1% by mass or more and 20% by mass or less based on a mass of the Ce-based oxide particle.

A SCR catalyst composition comprises an aluminosilicate zeolite having AFT framework structure and a promoter metal. Meanwhile, providing a process for preparing the aluminosilicate zeolite having AFT framework, and use of the zeolite for selective catalytic reduction of nitrogen oxides.

A SCR catalyst composition comprises an aluminosilicate zeolite having AFT framework structure and a promoter metal. Meanwhile, providing a process for preparing the aluminosilicate zeolite having AFT framework, and use of the zeolite for selective catalytic reduction of nitrogen oxides.