Patent ID: 9604176
Date: 2017-03-28
CPC Classifications: B01D,F01N,Y02T

Claim:
1. An exhaust gas purification system, comprising: NOx occlusion reduction type catalysts, each having a catalytic metal and a NOx occlusion material which occludes NOx when an air-fuel ratio of exhaust gas is in a lean state and releases the occluded NOx when the air-fuel ratio is in a rich state, wherein the NOx occlusion reduction type catalysts include a high-temperature NOx occlusion reduction type catalyst in which a NOx occlusion material containing an alkali metal is supported, and a low-temperature NOx occlusion reduction type catalyst in which a NOx occlusion material containing an alkaline earth metal is supported, disposed in series on an upstream side and a downstream side, respectively; a hydrocarbon injector on an upstream side of the high-temperature NOx occlusion reduction type catalyst; a first NOx sensor between the high-temperature NOx occlusion reduction type catalyst and the low-temperature NOx occlusion reduction type catalyst; a second NOx sensor downstream of the low-temperature NOx occlusion reduction type catalyst; and a hydrocarbon supply controller configured to provide— wherein the hydrogen addition device is a high-temperature hydrocarbon injector on the upstream side of the high-temperature NOx occlusion reduction type catalyst; and a low-temperature hydrocarbon injector between the high-temperature NOx occlusion reduction type catalyst and the low-temperature NOx occlusion reduction type catalyst, wherein the hydrocarbon supply controller controls the high-temperature hydrocarbon addition device and the low-temperature hydrocarbon addition device to supply—