Novel Approches in Oxidative Catalysis for Diesel Particulate Abatement

Abstract

Next 2008 European legislation on diesel engines will impose the use of specific traps, placed in the car exhaust line, so as to meet very stringent particulate emission limits (0.005 g/km). This paper provides a survey of the advancement status of R&D in the field of diesel particulate traps. Special emphasis is given to the combined use of traps and catalysts for regeneration purposes via catalytic combustion of the collected soot in the traps. Issues like trap materials selection, catalyst development, catalytic vs. non-catalytic trap performance are addressed. Specific highlights of the research in catalytic materials developed at Politecnico di Torino in the framework of EU projects will also be provided. In order to enhance the soot-catalyst contact conditions, several kinds of catalysts have been developed: oxygen spillover oxide, mobile catalysts based on alkali vanadates, spinels for the combined removal of particulate and NOx, precious metals enabling the NO oxidation to NO2 followed by reaction of this latter with particulate, heavy metal oxides, alkalimetal substituted perovskites capable of delivering oxygen species. An overview of these different approaches to soot oxidation will be provided pointing the way towards possible synergetic effects in multi-component catalysts.