| abstract |
A high-temperature NOx occlusion reduction type catalyst in which an NOx occlusion material containing an alkali metal is supported, and a low-temperature NOx occlusion reduction type catalyst in which an NOx occlusion material containing an alkaline earth metal is supported, are disposed in series on an upstream side and a downstream side, respectively, of an exhaust gas purification system. An oxidation catalyst is disposed on an upstream side of the high-temperature NOx occlusion reduction type catalyst. The desulfurization of the NOx occlusion reduction type catalysts is facilitated, and the NOx reduction efficiency is improved by the partial oxidation of hydrocarbons in the exhaust gas, while a wide NOx active temperature window is achieved. |