CATALYST FOR PURIFYING EXHAUST GAS AND PURIFICATION OF NITROGEN OXIDE

摘要

PURPOSE:To purify nitrogen oxide in combustion exhaust gas containing oxygen using hydrocarbon by bringing exhaust gas into contact with zeolite containing a hydrogen ion and specified in its SiO2/Al2O3 mol ratio and subsequently bringing the same into contact with In-containing zeolite specified in its SiO2/Al2O3 mol ratio. CONSTITUTION:A catalyst for purifying exhaust gas is constituted by arranging zeolite containing a hydrogen ion and characterized in that an SiO2/Al2O3 mol ratio is 10 or more on an exhaust gas inflow side and In-containing zeolite whose SiO2/Al2O3 mol ratio is 10 or more on an exhaust gas outflow side. Exhaust gas is brought into contact with zeolite containing the hydrogen ion and characterized in that the SiO2/Al2O3 mol ratio is 10 or more and subsequently brought into contact with In-containing zeolite whose SiO2/Al2O3 mol ratio is 10 or more. As a result, even when the concn. of oxygen is higher than a practical level, sufficient nitrogen oxide purifying efficiency is developed and nitrogen oxide can efficiently be removed from oxygen-containing combustion exhaust gas.