Chapter 12: LNT Catalysts for the Simultaneous Removal of NO_x and Soot: The DPNR Concept

This chapter refers to the DPNR (Diesel Particulate–NO_x Reduction) technology which aims at the simultaneous removal of soot and NO_x from diesel exhausts by coupling the LNT technology for NO_x reduction with the combustion of soot over the same LNT catalysts. First, the behavior of conventional Pt-based LNT catalyst in the soot combustion is analyzed. Then, the capability of Pt-based LNT catalysts to accomplish the removal of NO_x in the presence of soot under cycling conditions (i.e. alternating lean–rich phases according to the typical DPNR strategy) is addressed. Particular emphasis is given to the specific role of each catalyst component and on the complex interaction between the de-NO_x and de-soot functions. Finally, the potentialities of novel Pt-free DPNR formulations as well as alternative catalytic approaches are considered.