CATALYST FOR CLEANING EXHAUST

摘要

PROBLEM TO BE SOLVED: To provide a catalyst for cleaning exhaust capable of effectively removing HC generated during a cold start and excellent in the capacity of removing CO, HC and NOx during warming up.

SOLUTION: The catalyst for cleaning exhaust comprising an upstream catalyst layer 2 formed upstream of a flow-path wall 15 which forms a gas flow path for exhaust to pass therethrough, and a downstream catalyst layer 3 formed downstream of the flow-path wall 15 relative to the upstream catalyst layer 2, is characterized in that the upstream catalyst layer 2 is thinner than the downstream catalyst layer 3 and comprises Pd, and the downstream catalyst layer 3 includes an inner catalyst layer 31 comprising Pt and a ZrO2-CeO2complex oxide and an outer catalyst layer 32 comprising Rh formed on the surface of the inner catalyst layer 31. The ratio (T3/T2) of the thickness of the inner catalyst layer 31 (T2) to the thickness of the outer catalyst layer 32 (T3) is in the range of 1.5 to 2.5.

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