EXHAUST GAS PURIFICATION CATALYST AND EXHAUST GAS PURIFICATION APPARATUS USING SAME

摘要

Disclosed are: an exhaust gas purification catalyst which is capable of achieving a higher NOx removal ratio in comparison to conventional exhaust gas purification catalysts; and an exhaust gas purification apparatus which uses the exhaust gas purification catalyst. Specifically disclosed is an exhaust gas purification catalyst which is provided in an exhaust gas passage of an internal combustion engine. The exhaust gas purification catalyst captures NOx in the exhaust gas when the air/fuel ratio of the exhaust gas is lean, and releases the captured NOx for removal by reduction when the air/fuel ratio of the exhaust gas is stoichiometric or rich. The exhaust gas purification catalyst comprises: a first catalyst layer that contains Pt and has NOx capturing ability; a second catalyst layer that contains a zeolite that has HC capturing ability; and an intermediate layer that is provided between the first catalyst layer and the second catalyst layer and has NOx reducing ability. The intermediate layer contains, as a main component, at least one oxide selected from the group consisting of CeO2, ZrO2 and complex oxides containing Ce and Zr, and also contains one or both of Rh and Pd. Also specifically disclosed is an exhaust gas purification apparatus which uses the exhaust gas purification catalyst.