Product speciation during regeneration of lean NO_x traps

A set of elementary surface reactions was proposed for modeling the chemistry in a lean NO_x trap during regeneration (reduction of stored NO_x). The reaction mechanism is based on a series of flow reactor temperature ramp experiments performed on a core sample from a fully formulated lean NO_x trap catalyst. The experiments used simultaneous flow of NO_x and reductant species (H₂ and CO) to decouple the reduction reactions from the NO_x storage and release processes. The mechanism accounted for the observed product distribution (including NH₃ and N₂O) from the trap over a range of temperatures and inlet gas compositions similar to those expected for realistic operation. The NO_x trap regeneration and byproduct formation rates can be effectively captured using a relatively compact set of elementary reactions. NO_x trap regeneration can be simulated with a reasonably compact set of elementary reactions. Regeneration product speciation depended heavily on both catalyst temperature and local reactant concentrations (in particular, the ratio of NO_x/reductant). This is an abstract of a paper presented at the AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).