A method of converting nitrogen oxides in a gas to nitrogen by contacting the nitrogen oxides with a nitrogenous reducing agent in the presence of a zeolite catalyst containing at least one transition metal, wherein the zeolite is a small pore zeolite containing a maximum ring size of eight tetrahedral atoms, wherein the at least one transition metal is selected from the group consisting of Cr, Mn, Fe, Co, Ce, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Ag, In, Sn, Re, Ir and Pt.

Transition metal/zeolite scr catalysts

An exhaust gas-purifying catalyst includes a substrate, and a catalytic layer facing the substrate and including a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal having an average particle diameter falling within a range of 0.01 to 0.70 μm, the average particle diameter being obtained by observation using a scanning electron microscope. Another exhaust gas-purifying catalyst includes a substrate, and a catalytic layer formed on the substrate using slurry containing a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal having an average particle diameter falling within a range of 0.01 to 0.70 μm, the average particle diameter being obtained by observation using a scanning electron microscope.

Exhaust gas purifying catalyst

A catalyst is provided that is capable of efficiently purifying NO x contained in a lean atmosphere containing moisture The exhaust gas purifying catalyst contains a composition obtained by physically mixing a composite oxide containing zirconium and manganese and/or cobalt with a zeolite

The invention relates to a first catalyst for purifying an exhaust gas. The first catalyst has a substrate and a catalytic coating formed thereon. This catalytic coating has first and second grains. The first grain includes a porous carrier supporting thereon at least one of palladium and rhodium. The second grain includes a double oxide supporting thereon at least one of platinum and palladium. This double oxide is represented by a formula of (La1-x Ax)1-α BO.sub.δ where A is at least one element selected from barium, potassium and cesium, B is at least one of iron, cobalt, nickel and manganese, 0<X<1, 0<α<0.2, and δ is a number such that a net electric charge of the first double oxide becomes zero. The invention further relates to a second catalyst similar to the first catalyst. The first grain of the second catalyst includes a porous carrier supporting thereon at least one of platinum, palladium, rhodium and iridium. The second grain of the second catalyst includes a double oxide represented by a formula of (La1-x Ax)1-α BZr.sub.β O.sub.δ where A, B, x, α and δ are defined as above and 0<β<1. The first and second catalysts are each improved in NOx absorption capability and capable of purifying NOx contained in an oxygen rich exhaust gas, even after the passage of an exhaust gas of high temperature for a long time through these catalysts.

Catalyst for purifying oxygen rich exhaust gas

The present invention provides a catalyst for reduction of nitrogen oxides represented by the formula (A a O x .B b O y ).(C c O z .C' c' O z' )/S which is produced by supporting mixed metal oxides represented by the formula (A z O x .B b O y ).(C c O z .C' c' O z' ) in amorphous state on aluminum or silicon-containing support at calcination temperature of 400° to 700° C. in a molar ratio of 0.01:1 to 5:1, and a method for removing nitrogen oxides through selective catalytic reduction which comprises converting 50 to 50,000 ppm of nitrogen oxides in exhaust gas from automobile or from fixed source such as plant turbine and boiler, and other industry in a state of having 0.1 to 20% of excessive oxygen over (A a O x .B b O y ).(C c O z .C' c' O z' )/S catalyst by using 100 to 100,000 ppm of hydrocarbon reducing agent having 1 to 5 carbons under the reaction condition of 200° to 800° C. of reaction temperature, 1 to 10 atmosphere of reaction pressure and 1000 to 100,000/hour of space velocity into nitrogen in which A and B are lanthanide metals, such as lanthanum, cerium, praseodymium or neodymium, and alkali metals or alkaline earth metals, such as sodium, potassium, rubidium, cesium, magnesium, calcium, strontium or barium, C and C' are transition metals of the first period, such as cobalt, copper, nickel, manganese, iron, vanadium, titanium, chromium and zinc, and noble metals, such as platinum, rhodium, iridium, ruthenium, rhenium, palladium and silver, a, b, c and c' have stoichiometrically 0 to 1, provided with a+b=1, c+c'=1 and is in the range of 0.1-3.0:1.0, and S is aluminum or silicon-containing support, and is zeolite, silica, alumina or silica-alumina.

Method for removing nitrogen oxides in exhaust gas by selective catalytic reduction and catalyst for reduction of nitrogen oxides

PURPOSE:To provide a catalyst for efficiently reducing nitrogen oxide in a waste gas in a wide temp. range even in the coexistence of oxygen and moisture by providing an inside layer having a catalytic component expressed by a specific formula and a surface layer carrying a specific catalytic component on the inside layer. CONSTITUTION:The inside layer constituting a catalytic structural body on the base material contains a perovskite type multiple oxide expressed by the formula (A expresses La, Y, Ce, Pr, Nd or the like, B expresses Na, K, Bi, Th, Ba, Sr, Ca or the like, C expresses Mn, Co, Fe, Ni, Cr, Cu, V, Mo, W, Ta, Li or the like and 0<=X<=1) as the catalytic component. And the surface layer on the inside layer has the catalytic component made by carrying at least one kind of metals, the ions or the oxides of Ib group, IIa group, IIb group, IIIa group, IIIb group, IVa group, IVb group, Va group, VIIa group and VIII group in the Periodical Table on at least one kind of carrier selected from aluminum oxide, titanium dioxide, zirconium oxide and H type zeolite.

Catalytic structure for nitrogen oxide catalytic reduction

PURPOSE:To remove NOx in an exhaust gas efficiently. CONSTITUTION:From a viewpoint that in the reduction reaction between NOx and hydrocarbons on a reduction catalyst in an oxidative atmosphere, NO2, is reduced more easily than NO, an exhaust gas is previously contacted with an oxidation catalyst to oxidize NO in the exhaust gas into NO2. The treated exhaust gas, in an oxidative atmosphere containing excessive oxygen and in the presence of hydrocarbons, is contacted with a reduction catalyst selected from zeolite of a proton type, zeolite of an alkali metal type, and acid metal oxide (metal oxide treated with a compound having sulfate group to reduce NO2, in the exhaust gas into nitrogen.

Treatment method for removing nitrogen oxide

PURPOSE: To obtain the catalyst which efficiently reduces the NOx in exhaust gases in the presence of oxygen by using the compd. of a specific compsn. contg. alkaline earth metals, at least one kind among alkali metals, alkaline earth metals and rare earth elements, at least one kind of specific metals and Al as an effective component. CONSTITUTION: The effective component of this catalyst is expressed by compsn. formula A (1-x) A' x B' y Al (12-y) O (19-z) . In the formula, A denotes the alkaline earth metal; A' denotes at least one kind among the alkali metals, alkaline earth metals and rare earth elements; B' denotes Co, Ni, Cr, Fe, Mn or Cu; A and A' may be the same if A and A' are the alkaline earth metals; 0≤x≤1, 0≤y≤2, z are the values corresponding to the number of lattice defects. Such compds. include, for example, the compds. having a magnetoplumbite crystal structure. The ratio of the hydrocarbon or alcohols to be used as the reducing agent is preferably 0.2 to 2mol per 1mol NOx. COPYRIGHT: (C)1992,JPO&Japio

Catalyst for contact reduction of nox

PURPOSE:To efficiently reduce nitrogen oxides in exhaust gas by a catalyst obtained by supporting perovskite type composite oxide represented by a specific general formula on a solid acid carrier. CONSTITUTION:A catalyst for catalytically reducing nitrogen oxides using hydrocarborns and/or an oxygen-containing compound as a reducing agent is constituted by supporting perovskite type composite oxide represented by formula (wherein A is at least one kind of an element selected from La, Y, Ce or the like, B is at least one kind of an element selected from Ba, Sr, Ca or the like, C is at least one kind of an element selected from Mn, Co, Fe or the like and (x) is O<=X<=1) on a solid acid carrier. By this catalyst, nitrogen oxide is selectively reacted with hydrocarbon or an oxygen-containing compound in the coexistence of oxygen and nitrogen oxides in exhaust gas is efficiently reduced without using a large amount of a reducing agent.

Catalyst for catalytically reducing nitrogen oxide

PURPOSE:To efficiently remove NOx in exhaust gas containing SOx within an oxidizing atmosphere wherein excessive oxygen is present without lowering the activity of a catalyst to be used and to remove an imperfect combustion product discharged according to circumferences by the removal of NOx CONSTITUTION:Exhaust gas is brought into contact with a catalyst containing one or more kinds of polyvalent metal phosphate and ALPO type phosphate (crystalline aluminum phosphate [ALPO], crystalline aluminum silicate phosphate [SAPO], crystalline aluminum metal phosphate [MAPO] wherein a part of P or P-Al of ALPO is substituted with a metal such as Ti or Fe) in the presence of hydrocarbons or an oxygen-containing compound (hereinbelow referred to as hydrocarbons) present in the exhaust gas or introduced from the outside This catalyst preferentially promotes the reaction of NOx with hydrocarbons as compared with the reaction of oxygen with hydrocarbons and can remove NO in the exhaust gas with high efficiency

Kindaichi Yoshiaki

Papers

Catalytic structure for nitrogen oxide catalytic reduction

Treatment method for removing nitrogen oxide

Catalyst for contact reduction of nox

Catalyst for catalytically reducing nitrogen oxide

Decontamination of exhaust gas containing nitrogen oxide