Various NOx storage-reduction (NSR) catalysts with 1 wt% noble metal loading (Pt, Pd, or Rh) dispersed on MgAl2O4 have been synthesized by single step flame spray pyrolysis. The as-prepared powders consisting of nonporous nanoparticles were characterized by X-ray diffraction, scanning transmission electron microscopy, nitrogen adsorption-desorption, CO chemisorption and thermogravimetric methods. Different reduction agents were applied in the fuel rich cycles: H-2, CO or C3H6. Processes occurring during fuel rich and lean cycles were analyzed in detail by means of time-resolved diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermogravimetry combined with mass spectroscopy. With H-2 as reductant, Pt/MgAl2O4 showed the best performance at short regeneration time (<50 s), followed by Rh/MgAl2O4 and Pd/MgAl2O4. However, if CO or C3H6 were used as reductant. Rh/MgAl2O4 outperformed both other catalysts, especially at longer regeneration times (>50 s). NOx storage on these catalysts was mainly restricted to surface species, although bulk nitrate species were identified by DRIFTS as well. The latter were not completely reduced under the experimental conditions used. (C) 2012 Elsevier B.V. All rights reserved.