Catalytic combustion of soot over alkali doped SrTiO 3

Abstract

The effect of introduction of alkalies (Me = Li, K, Cs) into SrTiO 3 on the physico-chemical properties of resulted materials and their catalytic activity in soot combustion was studied. Two groups of SrTiO 3 based perovskites were prepared: substituted in A-position of the structure (Sr 1 − x Me x TiO 3, 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 Me 2O. 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 SrTiO 3 can be related to reversible decomposition of MeNO 3. XPS shows that surface of SrTiO 3 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 °C for SrTiO 3 and to 302–303 °C for Sr 0.8K 0.2TiO 3 and Sr 0.8K 0.2TiO 3, respectively. Substituted materials are more active in soot combustion than impregnated ones. A mechanism explaining effect of alkali metals nitrate addition to SrTiO 3 on its catalytic activity in soot combustion is proposed.