Characterization of a New Advanced Diesel Oxidation Catalyst with Low Temperature NOx Storage Capability for LD Diesel Politecnico di Torino

Format:

Conference/Event

Author/Creator:

Millo, Millo, author.

Contributor:

Vezza, Davide

Conference Name:

SAE 2012 World Congress & Exhibition (2012-04-24 : Detroit, Michigan, United States)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2012

Summary:

Currently, two consolidated aftertreatment technologies areavailable for the reduction of NOx emissions from diesel engines:Urea SCR (Selective Catalytic Reduction) systems and LNT (Lean NOxTrap) systems. Urea SCR technology, which has been widely used formany years at stationary sources, is becoming nowadays anattractive alternative also for light-duty diesel applications.However, SCR systems are much more effective in NOx reductionefficiency at high load operating conditions than light loadcondition, characterized by lower exhaust gas temperatures. Onepossible solution to improve the low temperature behavior, is theuse of newly developed Advanced Diesel Oxidation Catalysts (A-DOC)which are capable to store NOx at low exhaust temperatures (typicalof urban driving conditions) when SCR efficiency is low, and torelease the stored NOx at higher temperatures (id est, duringextra-urban driving conditions) where the urea injected iseffectively forming ammonia for the subsequent NOx conversion.Experimental tests were therefore carried out in order to assessthe performance of an A-DOC when exposed at the emissions comingfrom a modern Euro 5, 2.0 L displacement turbocharged Common RailDI diesel engine for a typical European passenger car: the enginefeatures a DOC and a DPF in close-coupled position, hosted into anon-purpose-designed dismountable canning, thus allowing an easyswitch between different components.The characterization of these newer DOC formulations wasperformed over NEDC cycles. Moreover, the catalysts were testedboth in fresh and hydrothermally aged conditions in order to have abetter understanding relative to robustness and durability of thesenewer catalysts.NOx storage capability, which was found to be impressively highfor a fresh A-DOC, significantly decreased after aging, thusleading to a final NOx cumulated emissions figure which equals theengine-out value for the aged A-DOC.Nevertheless, since most of the NOx released from the A-DOCoccurs during the EUDC segment, when a downstream SCR would likelyhave reached appreciable NOx reduction efficiencies, even an agedA-DOC could provide significant benefits in terms of NOx emissionsreduction.However, the analysis of the NO/NO₂ share downstream of the DPF,which is of crucial importance for SCR efficiency at lowtemperature, revealed that the overall conversion efficiency for NOover NEDC was negative, while on the contrary the conversionefficiency for NO₂ was remarkably high. As a result, the NO₂/NOxratio downstream of the DPF (id est, at the inlet of a downstreamSCR) remained significantly low during the whole EUDC segment, thushindering the achievement of high NOx conversion efficiencies andthe full exploitation of a synergetic combination of the A-DOC witha downstream SCR

Notes:

Vendor supplied data

Publisher Number:

2012-01-0373

Access Restriction:

Restricted for use by site license