Sol-gel titania modified with Ba and Li atoms for catalytic combustion

摘要

Samples of compounds in the ternary system BaO-Li2O-TiO2 were synthesized by using the sol-gel method at pH 3 and pH 9, and the calcination temperatures of 600 and 800°C in the region of solid solutions which can form the “ideal” composition Ba3Li2Ti8O20. The X-ray diffraction patterns of the samples showed a mixture of three crystalline phases, the main one was isostructural with the ternary phase Ba3Li2Ti8O20; the other two were BaTiO3 and Li2TiO3. By refining the structures with the Rietveld technique, a good fit to the experimental diffraction pattern was found, showing the partial substitution of Ti by Li in the Ba2Ti6O13 structure. The catalytic activity in methane combustion under the stoichiometric mixture of dilute CH4/O2 was higher for the samples calcined at 600°C, where the Ba3Li2Ti8O20 ternary compound was formed. This high activity can be related with the large specific surface area, presence of anatase and low crystallite size.