Role of surface and lattice copper species in copper-containing (Mg/Sr)TiO3 perovskite catalysts for soot combustion

Copper-containing (Mg/Sr)TiO3 perovskites have been prepared and characterized by ICP-OES, N2 adsorption at −196 °C, XRD, XPS and H2-TPR. The catalytic activity for soot combustion has been studied in a fixed-bed reactor under a NO + O2 mixture, and the interaction between the reactive gas mixture and selected catalysts has been studied by in situ DRIFT experiments.The role of the catalysts is to oxidize NO to NO2, and a relationship between NO oxidation capacity and soot combustion activity has been obtained. SrTi0.89Cu0.11O3 is the most active catalyst among those studied because it combines a high NOx chemisorption capacity with a high oxidation rate of the NOx species chemisorbed. Surface CuO is the active component of the samples Cu/SrTiO3 and Cu/MgTiO3, where the support promotes the activity of CuO, SrTiO3 being preferable to MgTiO3. On the contrary, active sites are not necessarily linked to the copper cations in the catalysts SrTi0.89Cu0.11O3 and MgTi0.9Cu0.1O3. Lattice copper promotes significantly the catalytic activity of the mixed oxide SrTi0.89Cu0.11O3, but a much lower promoting effect is observed for MgTi0.9Cu0.1O3.