| 摘要 |
PURPOSE: To obtain a catalyst capable of stably diminishing NOx in exhaust gas with high efficiency by wrapping a granular carrier made of Al2 O3 , ZrO2 or SiO2 with two or more layers of ceramics or metal oxides and specifying the temp. range in which each of the inner and outer ones of the two or more layers has catalytic activity. CONSTITUTION: A granular carrier made of Al2 O3 , ZrO2 or SiO2 is wrapped with two or more layers of ceramics or metal oxides. The inner one of the two or more layers is imparted with catalytic activity in the rage of 150-350 deg.C and the outer one is imparted with catalytic activity in the range of 300-600 deg.C. For example, a granular carrier 26 made of Al2 O3 , ZrO2 or SiO2 is wrapped with a 1st layer 21 of Al2 O3 , ZrO2 or SiO2 carrying Pt, a 2nd layer 22 of a metal oxide selected from among CeO2 , BaO and La2 O3 , a 3rd layer 23 of Al2 , ZrO2 or SiO2 carrying Rh or Ru and a 4th layer 24 of Al2 O3 , ZrO2 or SiO2 carrying Ce, Co, Ag, or Cu. |
