The present application relates to a cerium-tin-based composite oxide catalyst for catalyzing purification of a nitrogen oxide, a preparation method and an application thereof. The catalyst has the following chemical composition: a cerium-tin oxide and an M oxide, wherein the M is selected from any one of or a combination of at least two of P, Ti, Zr, V, Mn, Fe, Cu, Al, Si, Ni, Hf, Nb, Ta, Cr, Mo, W, or Re. According to the present application, a cerium-tin-based composite oxide catalyst having the characteristics such as high catalytic activity, high hydrothermal stability, excellent N.sub.2 generation selectivity, a wide operation temperature window, and adaptation to high space velocity reaction conditions is prepared by means of a non-toxic and harmless raw material and a simple method, and the present application is applicable to a device for catalyzing purification of a mobile source nitrogen oxide represented by diesel vehicle exhaust gas and a fixed source nitrogen oxide represented by flue gas from a coal-fired power plant.

The present application relates to a cerium-tin-based composite oxide catalyst for catalyzing purification of a nitrogen oxide, a preparation method and an application thereof. The catalyst has the following chemical composition: a cerium-tin oxide and an M oxide, wherein the M is selected from any one of or a combination of at least two of P, Ti, Zr, V, Mn, Fe, Cu, Al, Si, Ni, Hf, Nb, Ta, Cr, Mo, W, or Re. According to the present application, a cerium-tin-based composite oxide catalyst having the characteristics such as high catalytic activity, high hydrothermal stability, excellent N.sub.2 generation selectivity, a wide operation temperature window, and adaptation to high space velocity reaction conditions is prepared by means of a non-toxic and harmless raw material and a simple method, and the present application is applicable to a device for catalyzing purification of a mobile source nitrogen oxide represented by diesel vehicle exhaust gas and a fixed source nitrogen oxide represented by flue gas from a coal-fired power plant.

A photocatalytic device includes: a metal layer; and a photocatalytic layer provided on the metal layer and containing a photocatalytic material. In the photocatalytic layer, a slit or an opening is formed to expose a portion of the metal layer.

A photocatalytic device includes: a metal layer; and a photocatalytic layer provided on the metal layer and containing a photocatalytic material. In the photocatalytic layer, a slit or an opening is formed to expose a portion of the metal layer.

The invention relates to a catalyst which comprises: a) a mixed metal oxide of molybdenum, vanadium, niobium and optionally tellurium; and b) ceria particles having a crystallite size greater than 15 nanometers (nm); wherein the amount of the ceria particles, based on the total amount of the catalyst, is of from 1 to 60 wt. %. Further, the invention relates to a process for preparing a catalyst, which comprises mixing a mixed metal oxide of molybdenum, vanadium, niobium and optionally tellurium with ceria particles having a crystallite size greater than 15 nanometers (nm), wherein the amount of the ceria particles, based on the total amount of the catalyst, is of from 1 to 60 wt. %. Still further, the invention relates to an alkane oxidative dehydrogenation and/or alkene oxidation process wherein such catalyst is used.

The invention relates to a catalyst which comprises: a) a mixed metal oxide of molybdenum, vanadium, niobium and optionally tellurium; and b) ceria particles having a crystallite size greater than 15 nanometers (nm); wherein the amount of the ceria particles, based on the total amount of the catalyst, is of from 1 to 60 wt. %. Further, the invention relates to a process for preparing a catalyst, which comprises mixing a mixed metal oxide of molybdenum, vanadium, niobium and optionally tellurium with ceria particles having a crystallite size greater than 15 nanometers (nm), wherein the amount of the ceria particles, based on the total amount of the catalyst, is of from 1 to 60 wt. %. Still further, the invention relates to an alkane oxidative dehydrogenation and/or alkene oxidation process wherein such catalyst is used.

The present disclosure provides SCR catalyst compositions capable of reducing nitrogen oxide (NO.sub.x) emissions in engine exhaust. The catalyst compositions include a reducible metal oxide support containing ceria, one or more transition metal oxides as a redox promotor; and an oxide of niobium, tungsten, silicon, molybdenum, or a combination thereof as an acidic promotor. The redox promotor and the acid promotor are both supported on the reducible metal oxide support. Further provided are SCR catalyst articles coated with such compositions, processes for preparing such catalyst compositions and articles, an exhaust gas treatment system including such catalyst articles, and methods for reducing NO.sub.x in an exhaust gas stream using such catalyst articles and systems.

The present disclosure provides SCR catalyst compositions capable of reducing nitrogen oxide (NO.sub.x) emissions in engine exhaust. The catalyst compositions include a reducible metal oxide support containing ceria, one or more transition metal oxides as a redox promotor; and an oxide of niobium, tungsten, silicon, molybdenum, or a combination thereof as an acidic promotor. The redox promotor and the acid promotor are both supported on the reducible metal oxide support. Further provided are SCR catalyst articles coated with such compositions, processes for preparing such catalyst compositions and articles, an exhaust gas treatment system including such catalyst articles, and methods for reducing NO.sub.x in an exhaust gas stream using such catalyst articles and systems.

A niobate compound is provided that has excellent reactivity with alkali metal salts and can be reacted with alkali metal salts at room temperature. The niobate compound has a ratio (first peak/second peak) of the intensity of a peak (first peak) having the highest intensity at 2θ=9.4°±1.5° to the intensity of a peak (second peak) having the highest intensity at 2θ=29.0°±1.5° being 1.3 or more in the X-ray diffraction pattern.

A niobate compound is provided that has excellent reactivity with alkali metal salts and can be reacted with alkali metal salts at room temperature. The niobate compound has a ratio (first peak/second peak) of the intensity of a peak (first peak) having the highest intensity at 2θ=9.4°±1.5° to the intensity of a peak (second peak) having the highest intensity at 2θ=29.0°±1.5° being 1.3 or more in the X-ray diffraction pattern.