초록 ▼

The concentrations of NO and NO2 in nitrogen oxides contained in an exhaust gas are adjusted to substantially equal mol concentrations, whereupon the exhaust gas is held in contact with a metallic oxide catalyst together with ammonia. Owing to the adjustment of the NO and NO2 concentrations in the n

The concentrations of NO and NO2 in nitrogen oxides contained in an exhaust gas are adjusted to substantially equal mol concentrations, whereupon the exhaust gas is held in contact with a metallic oxide catalyst together with ammonia. Owing to the adjustment of the NO and NO2 concentrations in the nitrogen oxides, the reaction rate is enhanced, and the nitrogen oxides are reduced even at a low temperature. The adjustment of the concentrations of NO and NO2 in the nitrogen oxides is done by the oxidation of NO with ozone, the catalytic oxidation of NO with air or oxygen, the addition of nitric acid, the addition of NO or NO2, etc.

대표청구항 ▼

A process for reducing the concentration of nitrogen oxides in an exhaust gas containing nitrogen oxides, comprising the steps of: (a) adjusting the mol ratio of NO to NO2 in the exhaust gas such that the exhaust gas contains approximately equal molar amounts of NO and NO2, (b) mixing the exhaust ga

A process for reducing the concentration of nitrogen oxides in an exhaust gas containing nitrogen oxides, comprising the steps of: (a) adjusting the mol ratio of NO to NO2 in the exhaust gas such that the exhaust gas contains approximately equal molar amounts of NO and NO2, (b) mixing the exhaust gas having the adjusted mol ratio of NO to NO2 with an ammonia-containing gas, in which the mol ratio of ammonia to the total of NO and NO2 in the exhaust gas is about 0.8 to 2:1, and (c) contacting the resultant mixture with a metallic oxide catalyst at a temperature in the range of 100°-550°C., thereby to reduce nitrogen oxides into nitrogen gas and water, said metallic oxide catalyst containing titanium oxide as its first constituent and an oxide of at least one element selected from the group consisting of iron, copper, nickel, cobalt, molybdenum, tungsten, vanadium, chromium and cerium as its active component.