High-temperature denitration catalysts and processes for preparing same

A method of high-temperature denitration characterized in that NOx in an exhaust gas is reduced at 450° to 800° C. using ammonia as a reducing agent in the presence of a catalyst wherein at least one of tungsten oxide, molybdenum oxide and boron oxide is supported on a carrier comprising zirconium oxide and SO3 or SO42− and having solid acid strength (Ho) of −11.93 or lower.

A method of high-temperature denitration characterized in that NOx in an exhaust gas is reduced at 450° to 800° C. using ammonia as a reducing agent in the presence of a catalyst obtained by a process wherein an aqueous solution of a nitrate or a chloride of zirconium is basified to form a zirconium hydroxide precipitate, then the precipitate is dried, followed by supporting a sulfuric radical on the precipitate, and the precipitate is calcined.

A high-temperature denitration catalyst which comprises zirconium oxide and SO3 or SO42−, has solid acid strength (Ho) of −11.93 or lower and is used in a high-temperature region at a reaction temperature of 450° to 800° C., or wherein at least one of tungsten oxide, molybdenum oxide and boron oxide is supported on a carrier comprising zirconium oxide and SO3 or SO42− and having solid acid strength (Ho) of −11.93 or lower and which is used in a high-temperature region at a reaction temperature of 450° to 800° C., characterized in that the catalyst is dispersed and retained among fibers of ceramic paper.

A high-temperature denitration catalyst which comprises zirconium oxide and SO3 or SO42−, has solid acid strength (Ho) of −11.93 or lower and is used in a high-temperature region at a reaction temperature of 450° to 800° C., or wherein at least one of tungsten oxide, molybdenum oxide and boron oxide is supported on a carrier comprising zirconium oxide and SO3 or SO42− and having solid acid strength (Ho) of −11.93 or lower and which is used in a high-temperature region at a reaction temperature of 450° to 800° C., characterized in that the catalyst is dispersed and retained among fibers of a honeycomb structure obtained by superimposing flat ceramic paper and corrugated plate-like ceramic paper alternatively.

A high-temperature denitration catalyst for selective catalytic reduction of a nitrogen oxide in an exhaust gas comprising a composite oxide composed of titanium oxide and at least one of tungsten oxide, molybdenum oxide and boron oxide and having solid acid strength (Ho) of −11.93 or lower, characterized in that a binder is added to the catalyst and the obtained mixture is formed into a particle.

A process for preparing a plate type high-temperature denitration catalyst characterized in that titanium oxide is dispersed and retained among fibers of a ceramic fiber preform, the titanium oxide is dried and impregnated with a solution containing at least one element of tungsten, molybdenum and boron, and then the preform is dried and calcined under an oxygen atmosphere at a temperature of 500° to 800° C. to obtain the plate type high-temperature denitration catalyst comprising a composite of the above-mentioned metals and having solid acid strength (Ho) of −11.93 or lower.