Spatially resolved temperature and gas species concentration changes during C3H6 oxidation over a Pt/Al2O3 catalyst following sulfur exposure

Spatially resolved capillary inlet mass spectrometry (SpaciMS) and infra-red thermography have been used to characterize propylene oxidation along a Pt/Al2O3 monolith-supported catalyst, before and after heterogeneous sulfur deposition. The combined techniques clearly illustrate reaction location, and therefore catalyst use, and how these performance indicators change following different degrees of sulfur damage, as well as after partial desulfation. With each sulfation step, light-off temperatures (T50) increased and the time for back-to-front ignition changed pattern during temperature programmed oxidation. With 1500 ppm propylene fed, the reaction zones established during constant inlet temperature operation shifted further into the catalyst and increased in width following sulfur treatment. When the temperature was sufficient to achieve light-off of 4500 ppm propylene, back-to-front ignition proceeded toward the inlet, such that even after sulfur deposition the reaction zones were very close to the catalyst inlet and virtually indistinguishable between catalyst sulfation states. However, IRT measurements demonstrate that the reaction light-off position did move downstream in the catalyst with sulfur damage.

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► Catalyst exposure to sulfur shifted C3H6 oxidation light-off downstream.
► Reaction front propagation through the catalyst slowed in zones exposed to sulfur.
► Partial removal of sulfur from the zones re-established activity.