Catalyst unit, for reducing emission levels, particularly of nitrogen oxides, in internal combustion engine vehicle exhaust gas has upstream region of high concentration of noble metal and downstream region of lower concentration

摘要

A catalyst unit for reduction of (NO x) has an extended surface heat resistant carrier holding noble metal and also agents which absorb NO xunder lean, or stoichiometric combustion conditions, and comprises an upstream region of high noble metal content and a downstream region containing a lower concentration of noble metal.