Theoretical and Experimental Chemistry, Vol. 47, No. 3, July, 2011 (Russian Original Vol. 47, No. 3, May-June, 2011) INFLUENCE OF THE NATURE OF ALKALINE EARTH ELEMENT ON THE CATALYTIC PROPERTIES OF PEROVSKITES WITH THE COMPOSITION La 1–3x Li x M 2x CoO 3±d (M = Ca, Sr, Ba; 0 £ x £ 0.05) IN THE OXIDATION OF CO UDC 544.478.1 S. A. Nedil’ko, 1 I. V. Fesich, 1 A. G. Dzyaz’ko, 1 O. Z. Didenko, 2 G. R. Kosmambetova, 2 and P. E. Strizhak 2 Mixed solid solutions La 1–3x Li x M 2x CoO 3±d (M = Ca, Sr, Ba; 0 £ x £ 0.05) were obtained by concurrent precipitation of metal oxalates from aqueous solutions with subsequent thermal treatment. The phase homogeneity and parameters of the unit cells of the complex oxides were determined by X-ray powder diffraction. It was shown that modification of the lanthanum cobaltate by addition of alkaline earth metals and lithium led to an increase in the unit cell parameters, an increase in the defectiveness of the structures, a decrease in the dimensions of the field of coherent diffraction, and an increase in the catalytic activity with respect to oxidation of CO. Key words: perovskite, LaCoO 3 , alkaline earth elements, oxidation of CO, X-ray phase analysis. Interest in the catalytic properties of mixed oxides with the perovskite structure has arisen from their high thermal stability and the possibility of their practical use in the flameless combustion of methane in catalytic heat generators and the preparation of synthesis gas from natural gas [1, 2]. The high catalytic activity of perovskites in redox processes results from the characteristics of their crystal structure which includes oxygen anions and two types of cation: A rare earth and/or alkaline earth cations and B transition d metals [2]. The ordering of the A cations in the perovskite structure guarantees the thermal stability of the oxygen sublattice. In the sublattice consisting of the transition d-metal cations, the B cations may be found in several stable states of different oxidation states, compensating the charge during electron transfer in the intercalation of adsorbed molecular oxygen in the anionic sublattice of the perovskite. Modification of perovskites with cations of other elements with lower oxidation states results in the formation of defects (oxide vacancies which are the active centers in oxidation reactions) and, moreover, in significant improvement of electron-conduction properties of perovskites [3, 4]. A disadvantage of perovskites is their low specific surfaces, about 1-3 m 2 /g. So despite the fact that the specific catalytic activity of perovskites is considerably higher than that of simple oxides, the overall conversion of reagents is lower as a rule [5]. Recently as a result of developments in nanotechnology, new methods have been developed for the synthesis of highly dispersed materials, including perovskites [6-10]. It has been shown that the use of the sol–gel method, the Pekini method, 0040-5760/11/4703-0183 ©2011 Springer Science+Business Media, Inc. 183 ________ 1 Taras Shevchenko National University of Kyiv, Vul. Volodymyrs’ka, 64, Kyiv 01601, Ukraine. E-mail: fesych@univ.kiev.ua. 2 L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Prospekt Nauky, 31, Kyiv 03028, Ukraine. E-mail: didenko_oz@yahoo.co.uk. ___________________________________________________________________________________________________ Translated from Teoreticheskaya i Éksperimental’naya Khimiya, Vol. 47, No. 3, pp. 174-178, May-June, 2011. Original article submitted April 12, 2011; revision submitted May 23, 2011.