| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control system capable of sufficiently enjoying a fuel consumption improving effect by travelling mainly in an oxygen excessive region (for example, in a lean state) and effectively using H2 contained in exhaust gas as a reducer. SOLUTION: The exhaust emission control system is constituted by arranging at least an NOx removing catalyst to reduce and treat nitrogen oxides with hydrogen as a reducer as well as an H2 diffusion control material to control diffusivity of hydrogen in an exhaust passage of an internal combustion engine or combustion equipment to be mainly driven in the oxygen excessive region and it increases H2 density in the exhaust gas to be supplied at the time when the NOx removing catalyst reduces and treats the nitrogen oxides by controlling diffusing speed of H2 by the H2 diffusion control material. The H2 diffusion control material and the NOx removing catalyst are laminated on an integral structured catalyst support and make a multilayer structure, and either one or both of an inner surface and an outer surface of this NOx removing catalyst layer makes or make contact with the H2 diffusion control layer. The H2 diffusion control material contains more than two kinds of fire resistance inorganic matters modes of pore diameter distribution of which are less than 4A and less than 10A. |
