Zeolite and zirconia-based catalysts for Nox and soot removal from Diesel exhausts

NOx Storage-Reduction (NSR) technologies rapresent a promising solution to cope with environmental regulations related to the emissions of NOx in the exhausts of diesel and lean-burning gasoline engines; however, since NSR systems are not sufficiently active below 200°C, the ability to store and reduce NOx at low temperatures is going to be a key feature in the years to come. Furthermore, integrated approaches, able to combine the removal of both NOx and PM, are gaining more relevance since they allow a reduction of the volume and cost of the aftertreatment system. In this context, this thesis aims at the study of metal-promoted zeolites as catalysts for the storage at low temperatures and the reduction of NOx. Moreover, a kinetic study of the combustion of soot has been carried out in order to gain relevant information for future analysis of DPNR-like systems. Thanks to the on-going collaboration with professor Stanislaw Dzwigaj of the Université Pierre et Marie Curie (Paris, FR), zeolite-based catalytic materials were prepared varying the metallic phase as well as the zeolite support, and characherized. This materials have been tested in order to investigate their storage ability at low temperature. Promising results were achieved in the case of Pd-impregnated MOR and ZSM5 zeolites. However, their storage ability strongly decreases in the presence of water and hence the formulation of such materials needs to be improved. A first screening in order to check their efficiency in the reduction of NOx was also carried out. Concerning soot oxidation, the effect of the temperature and of the oxygen concentration was investigated under under both non-catalytic and catalytic conditions, using a zirconia-based catalyst.