(474e) Sulfur Effects on Spatiotemporal Distribution of Reactions Involved in A Commercial Lean Nox Trap Operation

Sulfur poisoning of lean NOx trap (LNT) catalysts is an important technical challenge for broad implementation of the technology. On-going efforts to develop LNTs with improved sulfur tolerance and efficient desulfation strategies require more detailed understanding of sulfur poisoning mechanisms and its impact on relevant LNT reactions. In the present study, we aimed to obtain a clear picture of how sulfur affects the spatiotemporal distribution of reactions and temperature inside a monolithic LNT. We experimentally evaluated a commercial LNT monolith core sample in a bench-flow reactor with simulated engine exhaust. During realistic lean/rich cycling, we measured gas composition and temperature inside/along the monolith channel at different sulfur loadings. The obtained spatiotemporal profiles, combined with integral catalytic performance data, provided useful information about sulfation and its impact on LNT reactions such as NOx storage, oxygen storage, reductant utilization, and byproduct formation. Sulfur tended to accumulate in a plug-like fashion in the reactor and progressively inhibited NOx storage capacity along the axis. The NOx storage/reduction (NSR) reactions occurred over a relatively short portion of the reactor. Oxygen storage capacity (OSC) was poisoned by sulfur also in a progressive manner but to a lesser extent. Global selectivity for N2O remained low at all sulfur loadings, but NH3 selectivity increased significantly with sulfur loading. We interpreted the NH3 breakthrough dependency on sulfur loading based on the evolution of spatial reactions distribution and will be described in detail in the presentation. Sulfation also led to significant changes in reductant consumption trends and temperature profiles in a manner that was consistent with the progressive poisoning of the LNT.