We compared the NOx regeneration process for the storage and reduction reaction of NOx using both Pt/Ba/Al2O3 and Pt/K/Al2O3 on a millisecond time range. The NOx storage process was simulated using pulses of gaseous O-2 and NO, and the reduction was simulated using pulses of H-2 gas. When pulses of H-2 were supplied, the time profiles of N-2 and NH3 products were measured using a TAP-type reactor with a time-of-flight mass spectrometer. The time profiles of the products during the reduction process depended on the temperature, the amounts reduction reaction using a simple two-step representation of the of gases and the components of the samples. From an analysis of the NO process, it was found that the rate of reduction of NOx using Pt/K/Al2O3 would be larger than reduction using Pt/Ba/Al2O3. Further analysis using different precious metals wilt help us to extend our understanding of the NSR reaction mechanism. (C) 2007 Elsevier Ltd. All rights reserved.