Reductant Use and N-Byproduct Formation During Regeneration of a NSR Catalyst
William Epling, University of Waterloo
NOX storage/reduction (NSR) catalysts as applied to diesel exhaust cycle between the typical, oxygen-rich exhaust composition and an induced reductant-rich gas composition. During the lean portion, NOX is stored via nitrate formation. During the rich phase the nitrates are reduced, resulting in NOX reduction to N2 and restoring the surface’s ability to trap NOX in the ensuing lean phase. Data taken via the CLEERS proposed testing protocol demonstrate that during the regeneration event, multiple reactions are occurring and include reductant reaction with surface oxygen and nitrate species. The utilization of the reductant for each of these has different rates at different temperatures. This results in different extents of reduction, N-byproduct species and surface “clean-up” for the next lean phase.