Performance Features of Pt/BaO Lean NOx Trap with Hydrogen as Reductant

The performance of a model Pt/BaO/Al2O3 monolith catalyst was studied using H-2 as the reductant. The dependence of product selectivities on operating parameters is reported, including the durations of regeneration and storage times, feed composition and temperature, and monolith temperature. The data are explained in terms of a phenomenological model factoring in the transport, kinetic, and spatio-temporal effects. The Pt/BaO catalyst exhibits high cycle-averaged NOx conversion above 100 degrees C, generating a mixture of N-2 and byproducts NH3 and N2O. The cycle-averaged NOx conversion exhibits a maximum at about 300 degrees C corresponding to the NOx storage maximum. The N-2 selectivity exhibits a maximum at a somewhat higher temperature, at which point the NH3 selectivity exhibits a minimum. This trend conveys the intermediate role of NH3 in reacting with stored NOx. Both N-2 and N2O are also formed during the storage steps from the oxidation of NHx species produced during the regeneration. (c) 2009 American Institute of Chemical Engineers AIChE J, 55: 687-700, 2009