NOx Adsorber Aging on a Heavy-Duty On-Highway Diesel Engine - Part Two

A 5.9 liter medium-heavy-duty diesel engine, equipped with a diesel exhaust aftertreatment system consisting of catalyzed diesel particulate filters and NO_x adsorber catalysts arranged in a dual-path configuration was evaluated with the goal of studying the thermal aging characteristics of a number of NO_x adsorber formulations and documenting adsorber formulation improvements over time. The performance of 2005 vintage NO_x adsorber formulations was compared with the performance of older formulations. The testing was performed in three steps. The first was to run with zero sulfur fuel at a high temperature engine operating mode to characterize performance losses due to exposure to the highest temperatures experienced under normal operation. This was followed by aging without sulfur but with desulfation events to characterize the impact of the higher desulfation temperatures on catalyst deactivation. Finally, high sulfur fuel was used along with desulfation events to investigate the additional impact of sulfur on performance. The testing documents substantial improvements on NO_x adsorber durability with the best adsorber demonstrating about 82% control over the SET after the equivalent of 814,000 miles of accelerated aging.