Investigation of the mechanism of the selective reduction of NO, by propane over the individual samples of commercial catalysts NTK, STK, and Ni-Cr-oxide catalyst and over their binary mechanical mixtures has shown that the synergistic effect observed in the latter case is caused by the oxidative activation of propane on the STK and Ni-Cr-oxide surface which results in the formation of more effective reducing agents, propylene and hydrogen correspondingly. In the case of the Ni-Cr-oxide and NTK catalytic system, hydrogen forms over the former catalyst in propane oxidation, migrates through the gas phase to the latter catalyst, where NO, is activated with the formation of nitrate structures which interact with the said hydrogen giving the products of the overall reaction, N-2 and H2O. When the pair of NTK and STK is concerned, the interaction Of C3H8 and 02 over the latter catalyst gives stable products of partial propane oxidation and/or oxidative dehydrogenation which are transported due to interphase diffusion to NTK surface. The nature of observed synergistic enhancement of catalysis in the case of binary mixtures is proposed under the terms of "remote control" mechanism described in literature and can serve a useful purpose in the design of catalysts for this reaction. (c) 2006 Elsevier B.V. All rights reserved.