Investigation of NOx Adsorber Catalyst Deactivation

The understanding of deactivation mechanisms is critical to the development of NOx adsorber catalysts with improved durability. The thermal deactivation of a state-of-the-art Pt/Rh based NOx adsorber catalyst is evaluated following oven agings at 800 and 900°C. Sulfur poisoning during lean/rich cycling is studied as a function of catalyst inlet temperature and SO₂ concentration. Complementing these studies utilizing synthetic exhaust gas compositions, deactivation resulting from three different engine aging schedules is examined.

The performance of engine-aged catalysts is evaluated as received, and following desulfurization procedures differing in inlet temperature and air/fuel ratio. The impact of aging schedules on NOx adsorption and three-way catalyst function is discussed with respect to precious metal dispersion, washcoat sintering, as well as sulfur build-up and oil-derived poisonings.