Catalytic combustion of soot over alkali doped SrTiO3

The effect of introduction of alkalies (Me = Li, K, Cs) into SrTiO3 on the physico-chemical properties of resulted materials and their catalytic activity in soot combustion was studied. Two groups of SrTiO3 based perovskites were prepared: substituted in A-position of the structure (Sr1-xMexTiO3, x = 0.05-0.2) and impregnated with the same amount of alkali metals. Prepared materials exhibit low specific surface area and perovskite structure, only these ones impregnated with the highest amount of Cs (K) show weak XRD signals of Me2O. TPD-O-2 experiments show bimodal profiles of O-2 desorption curves with maximums corresponding to individual step of alkali nitrates thermal decomposition. It is supposed that second peak of O-2 desorption from impregnated SrTiO3 can be related to reversible decomposition of MeNO3- XPS shows that surface of SrTiO3 substituted with K (Cs) is much richer in these elements than the surface of impregnated one. Prepared materials lower the temperature of soot ignition from 530 (inert) to 470 degrees C for SrTiO3 and to 302-303 degrees C for Sr0.8K0.2TiO3 and Sr-0.8.K0.2TiO3, respectively. Substituted materials are more active in soot combustion than impregnated ones. A mechanism explaining effect of alkali metals nitrate addition to SrTiO3 on its catalytic activity in soot combustion is proposed. (c) 2006 Elsevier B.V. All rights reserved.