Sulphur Poisoning and Regeneration of NOx Trap Catalyst for Direct Injected Gasoline Engines

Abstract

<div class="htmlview paragraph">Sulphur poisoning and regeneration of NO<sub>x</sub> trap catalysts have been studied in synthetic exhausts and in an engine bench. Sulphur gradually poisoned the NO<sub>x</sub> storage sites in the axial direction of the NO<sub>x</sub> trap. During sulphur regenerations, hydrogen was found to be more efficient than carbon monoxide in removing the sulphur from the trap. The sulphur regeneration became more efficient the richer the environment (λ<1) and the higher the temperature (at least 600°C). H<sub>2</sub>S was found to be the main product during the sulphur regeneration. However, it was possible to reduce the H<sub>2</sub>S formation and instead produce more SO<sub>2</sub> by running with lambda close to one or by pulsing lambda. Even if a relatively large amount of sulphur was removed from the NO<sub>x</sub> trap, these methods gave a much less efficient regeneration per sulphur atom removed than when running relatively rich constantly. Finally, a model that could explain this observation was proposed.</div>