Presently, a growing interest is focused on unregulated emissions of nitrous oxide (N2O) from stationary and mobile sources in order to anticipate future restrictive legislations, since N2O exhibits a significant higher global warming power than that of CO2. The adoption of end-of-pipe technologies is appropriate. However, the simultaneous conversion of NOxand N2O over catalytic processes is still challenging both for industrial plants and automotive exhaust gases particularly at low temperature. Subsequent selectivity enhancements towards the formation of N2probably need better insights into the mechanisms involved in the formation and the subsequent conversion of N2O during the overall reduction of NOx, particularly in O2excess. Up to now practical solutions for mobile sources imply the use of noble metals. Conventional three-way catalysts (TWC) running under stoichiometric conditions are wide-spread through the world even if their efficiency is still restricted during the cold start engine with a substantial formation of undesired N-containing products such as N2O. Nowadays, the use of noble metals in TWC, particularly Rh, becomes more and more questionable with the continuous development of lean-burn engines because of their poor efficiency to convert NOxinto nitrogen in those running conditions. In such a circumstance, there is a particular interest in developing non-noble metal-based catalysts and also the use of additives and alternative reducing agents. By way of illustration, hydrogen could be an interesting issue for both stationary and mobile sources for the reduction of NOxemissions at low temperature under lean conditions. This paper will discuss on such an opportunity and the correlative development of novel catalysts. © 2007 Elsevier B.V. All rights reserved.
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