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(570c) Effects of C12H26 and O2 on NO Uptake on Pd/SSZ-13: Experiments and Modeling

Harold, M. - Presenter, University of Houston
Ambast, M., University of Houston
Addressing NOx (NO+NO2) emissions during vehicle cold start (< 150oC) remains a major challenge. Passive NOx Adsorber (PNA) is a potential solution to reduce NOx emissions during the cold start period. Therefore it is important to study the effects of different exhaust components on NOx uptake on PNA. The objective of the current study is to understand the impacts of C12H26 (dodecane) and O2 on NOx uptake and release. Systematic experiments are conducted with mechanistic-based modeling to elucidate the underlying mechanism for coupled C12H26, O2 and NO uptake on Pd/SSZ-13.

In our recent study we developed a one-dimensional two-phase transient monolith model containing a mechanistic-based microkinetic scheme to explain the NOxuptake and release over different PNA materials [1,2]. Model involves Z-[PdOH]+,Z-Pd2+Z- and Z-Pd+ as active sites. Here we will present experimental and modeling studies on the uptake of NO in the presence of C12H26 over a Pd/SSZ-13. When a co-feed containing C12H26 and NO is supplied to Pd/SSZ-13 catalyst, compared to NO-only feed, the NO uptake is unaffected but during the subsequent temperature ramp, the release of trapped NO is delayed to over 220oC from 175oC. The release delay is beneficial for PNA performance as the primary NOx aftertreatment technology Selective Catalytic Reduction (SCR) is not operated below 200oC. Oxidation of C12H26 leads to the generation of partial oxidation product CO. Carbon monoxide binds strongly to Pd sites with NO and can delay NO release. The developed model was extended to include the effects of C12H26 on NO uptake and release. Some of the modelling results are shown in Fig. 1. The model is validated at different uptake temperatures, temperature programmed desorption (TPD) ramp rates, and feed flow rates, affording its use to validate the experimental findings and to identify optimal operating strategies.