Spatially Resolving Reactions in Diesel Oxidation Catalysts for Low Temperature Combustion Exhaust

Melanie  Hazlett, University of Houston

Concerns over global warming and climate change have led to increasingly strict environmental policies on vehicle emissions.  This has been the driving force for optimizing both engine operation and catalytic after-treatment systems to reduce emissions.  With the development of new low temperature combustion (LTC) engines comes the need to consider how these new exhaust conditions will affect the performance of these catalytic systems.  LTC engines have higher concentrations of CO and hydrocarbons, which in diesel engine exhaust systems are components that the diesel oxidation catalyst (DOC) can oxidize.  This study looks at the performance of model Pt/Al2O3 and Pt/Pd/Al2O3 catalysts under simulated LTC diesel exhaust conditions, using spatially resolved data.  The simulated exhaust gas contained CO, C2H4, C2H6 and C12H26. The species concentrations were measured along the length of the catalyst, as a function of time and temperature during temperature programmed oxidation experiments. For each reactant, the results show significant inhibition, both self-inhibition and by the other species. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was also performed on these catalysts to determine surface species present during reaction conditions.  Understanding the axial concentration gradients in the catalyst during these reactions will help us in designing better DOCs in the future to enhance the low temperature catalyst performance.