Spatial Temperature and Concentration Profile Chanages Following Heterogeneous Thermal Aging in a Model Diesel Oxidation Catalyst
April Russell, University of Waterloo
April Russell, William Epling, Howard Hess, Hai-Ying Chen, Cary Henry, Neal Currier and Aleksey Yezerets
Propylene oxidation was used as a probe reaction to investigate temperature and concentration profile changes along a Pt/Al2O3 monolith-supported catalyst before and after thermal aging. Infra-red thermography and spatially-resolved capillary inlet mass spectrometry (SpaciMS) techniques together demonstrate catalyst use, by reaction location, and how this changes with aging. In this study, heterogeneous thermal aging targeted at the catalyst inlet. After aging, the reaction zone moved further from the catalyst inlet and was broader. Temperature and concentration wave velocities in back-to-front ignition also decreased after aging. Both effects were more pronounced with lower propylene concentrations. An established steady state was disrupted with step changes in propylene concentration and three different effects were observed depending on the initial steady-state reaction condition. A reaction zone initially located at the inlet, following light-off and back-to-front ignition, moved upstream when decreasing the propylene concentration and moved downstream when concentration increased. A reaction located at the outlet, following light-off without back-to-front ignition, moved forward with concentration increase until reaching the front, after which the aforementioned behaviour occurred. When a low level of reaction existed without light-off, increasing the propylene concentration caused reaction extinction.