Tuning operational conditions for efficient NOx storage and reduction over a Pt–Ba/Al2O3 monolith catalyst

A well-controlled homemade Pt–BaO/Al2O3 monolith catalyst has been used for tuning the operational conditions at which the NOx storage and reduction (NSR) of the lean-burn engine exhaust gases is achieved more efficiently. The following operational conditions have been analyzed: the duration of the lean (storage) period, and the reductant (H2) concentration and duration of the regeneration (rich) period. The storage pattern during the lean period is evaluated by the percentage of NOx stored or NOx trapping efficiency (ηT), and the performance during the rich period is evaluated by the NOx reduction conversion (XR) and the selectivity to nitrogen (SN2SN2). These three response variables have been integrated into the single parameter that we have named integral NSR efficiency (ɛNSR) of the whole NSR process, which represents the percentage of N2 produced at the reactor exit relative to the NOx fed to the reactor. The proposed graphical map consists of a series of ɛNSR-isocurves and allows predicting the NSR efficiency for any combination of the three studied operational conditions (CH2,tR,tL)(CH2,tR,tL). Such operational map shall also be useful to compare the global NSR behavior of commercial catalysts under real operating conditions.