Comprises a catalytic activity or activity of bias being adjustable, which can be used as trap a nox associating two compositions based on manganese and another element selected from among the alkali, alkaline-earth - metal and the rare earths.

摘要

A compound includes two compositions each having a support and an active phase including manganese and another element. In the first composition the element is either an alkaline or alkaline earth element and is bound chemically to the manganese. In the second composition the element is an alkaline, alkaline earth or rare earth element. The second composition has a specific surface area of - 10 m2/g after being calcined for 8 hours at 80 deg C. Independent claims are included for the following: (a) a system having a substrate supporting two layers containing the respective compositions (b) a system having the compound in a layer containing a mixture of the two compositions; (c) a system having two substrates each with a layer carrying one or other of the compositions; (d) reducing nitrogen oxides in a flue gas using a system as in (b), (c) or (d); and (e) the use of the above compound for treating the exhaust gas from an internal combustion engine.