| 摘要 |
PURPOSE:To provide a catalyst device effective to clean exhaust gas from an engine using natural gas as fuel and to reduce the generation of formaldehyde and other minor components which are harmful to human body and have high photochemical reactivity by the coexistence with NOx in the exhaust gas. CONSTITUTION:Onto a base, in which an acid resistant three dimensional ceramic honeycomb body is wash-coated with gamma-Al2O3, more than one kind of metal selected from planinum group elements comprising Pd, Pt, and Rh is carried to form a catalyst (a). More than one kind of oxide of metal selected from lanthanoids comprising La, Nd, and Pr is added to the catalyst (a) to prevent the decrease in a methane conversion ratio at high temperatures and to improve the heat resistance of the catalyst, so that a catalyst (b) is formed. Magnesium oxide for preventing the generation of formaldehyde by the coexistence with NOx is added to the catalyst (b), forming a catalyst (c). The catalysts (b) and (c) are arranged to form a multilayerestructure 5a, 5b. |
