| 摘要 |
PROBLEM TO BE SOLVED: To reduce nitrogen oxide due to hydrocarbon while emission of methane is inhibited in cleaning treatment of combustion exhaust gas of natural gas containing excess oxygen by a method wherein a nitrogen oxide-removing catalyst is arranged on an upstream side under existence of hydrocarbon, and a methane oxide catalyst is arranged on a downstream side and used. SOLUTION: In the case where combustion exhaust gas of natural gas is cleaned, a nitrogen oxide is firstly reduced and removed by bringing an exhaust gas into contact with a catalyst for reducing the nitrogen oxide under existence of hydrocarbon arranged on an upstream side. Then a remaining methane is removed by bringing the exhaust gas into contact with a catalyst for oxidizing and removing the methane which is arranged on a downstream side. As the oxidizing catalyst herein, a catalyst or the like for supporting, for example, palladium or palladium and platinum on zirconia is mentioned. Then a support amount of palladium is preferably about 2-20% of a zirconia support weight, and in the case where palladium and platinum are jointly used, platinum is preferably about 10-50% of the palladium weight. |
