Study of DPNR catalysts for combined soot oxidation and NO x reduction

Abstract

The behavior of a model PtBa/Al 2O 3 model NSR catalyst in both the NO x storage/reduction and soot oxidation is investigated in this work. It is found that the presence of soot negatively influences the NO x storage capacity of the catalyst, evaluated at 623 K in presence of water and CO 2 in the feed stream: in fact the amounts of NO x stored in presence of soot decrease by nearly 30% in the presence of roughly 10% (w/w) of soot. The presence of soot has a destabilizing effect on the NO x adsorbed species, which decompose to a large extent in the absence of gas phase NO and oxygen. This has also been confirmed by dedicated TPD and TPO experiments. However the presence of soot does not appreciably affect the behavior of the PtBa/Al 2O 3 catalyst in the reduction by H 2 of the stored nitrates, being in all cases N 2 the major reaction product along with minor amounts of ammonia. During the storage of NO x , soot oxidation takes place. Notably, the stored NO x participate in the soot oxidation upon release of NO 2 and O 2 which actively oxidize soot. However a direct participation of the adsorbed NO x species in the oxidation of soot cannot be excluded.