SO2 oxidation model for Pt/Pd based diesel oxidation catalysts

Hom  Sharma, UCONN

ORAL PRESENTATION: Sulfur oxides (SOx) in the diesel engine exhaust are one of the major factors contributing toward deactivation of emissions aftertreatment catalysts. Interactions of SOx with the catalyst metals and supports can result in sulfate formation. The noble metals (Pt/Pd) based DOC is one of the most expensive components of the emissions aftertreatment system. Despite the extensive research conducted on DOC performance, the interaction of DOC with the sulfur oxides in the exhaust is not clearly understood and it makes the emissions oxidation chemistry even more challenging. In this work, we will discuss the development of a detailed elementary-step microkinetic model for Pt-DOC that accounts for the oxidation of oxides of sulfur, such as SO2, along with the model predictions for catalytic oxidation of SOx in fixed bed and monolith reactors under practically relevant operating conditions. Further, we explore the SOx (x = 0 ? 4) interactions and reaction pathways of SO2 oxidation on Pt and Pd surfaces using first principles density functional theory (DFT). Our results show good agreement with the experimental observations. The elementary-step surface reaction and SOx interaction mechanisms could be utilized for improved design and control of the aftertreatment system as well as appropriate DOC sizing.

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