Göran Wirmark

Spatially Resolved Effects of Deactivation on Field-Aged Automotive Catalysts

Four samples from each of two field-aged catalysts subjected to different field test conditions were investigated. The light-off and conversion performance of each sample was measured in a synthetic exhaust flow reactor system. Time-resolved laser IR spectroscopy was used to investigate the catalyst behaviour under transient conditions. Significant differences in light-off temperatures and transient conversion performance between the samples was observed. The samples taken from the inlet side of the monolith were more deactivated than the corresponding ones from the outlet. However, samples taken from peripheral positions always showed better performance than samples originating from the centre. For the covering abstract of the conference see IRRD 852385.

Deterioration of Three-Way Automotive Catalysts, Part I - Steady State and Transient Emission of Aged Catalyst

Five field-aged catalysts with different mileages were analysed with respect to emission performance and structural changes. The FTP-75 emission results were compared to synthetic exhaust gas tests including: i) light-off, ii) lambda screening at stationary and oscillating stoichiometry, iii) space velocity variation. Several samples from different positions of one catalyst were used to achieve the spatially resolved activity profile for that catalyst. Surface characterisation was used to characterise accumulated catalyst poison. Laboratory space velocity test was concluded to be a sensitive probe for catalyst performance: good correlation to vehicle emission data was found. An analysis of the influence of temperature and oscillation on the catalyst conversion performance was made, with particular emphasis on the ageing effects. The oxidation of hydrocarbons and CO, and the reduction of NO was significantly higher during oscillations at 753 K than at steady state, while this effect was not found at 653 K. The spatially resolved activity profile revealed large differences between the oxidation and NO reduction activities, the latter being the most significantly deteriorated catalyst function. For the covering abstract see IRRD 858138.