Noble nitrogen oxide decomposition

One way to lower costs is to substitute, totally or partially, noble metals by cheaper materials. In this vein, rare-earth-containing mixed oxides have been assayed to eliminate several pollutants. They are now in use for several commercial applications, mainly for CO oxidation and odor elimination. Efforts are being made to develop new uses of these materials in other environmental fields. In what follows, the use of mixed oxides in total oxidation, nitrogen oxides decomposition and NOv reduction will be reviewed. 

Complex oxides of the perovskite structure containing rare earths like lanthanum have proved effective for oxidation of CO and hydrocarbons and for the decomposition of nitrogen oxides. These catalysts are cheaper alternatives than noble metals like platinum and rhodium which are used in automotive catalytic converters. The most effective catalysts are systems of the type Lai vSrvM03, where M = cobalt, manganese, iron, chromium, copper. Further, perovskites used as active phases in catalytic converters have to be stabilized on the rare earth containing washcoat layers. This then leads to an increase in rare earth content of a catalytic converter unit by factors up to ten compared to the three way catalyst. 

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