MOSSBAUER STUDY OF PEROVSKITE OXIDES FOR OXIDATIVE COUPLING OF CH 4 AND ABSORPTION OF CO 2 *) K. NOMURA Graduate School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113, Japan Z. HOMONNAY, A. VERTES Department of Nuclear Chemistry, Eotvos University, P.O. Box 32, H-1518, Budapest 112, Hungary V. CHECHERSKY, A. NATH Department of Chemistry, Drexel University, 32nd and Chestnut Streets, Philadelphia, Pennsylvania 19104, USA Y. UJIHIRA Research Center for Advanced Science and Technology, The University of Tokyo, Komaba 4-6-1, Meguro-ku, Tokyo 153, Japan T. HAYAKAWA, K. TAKEHIRA National Institute of Material and Chemical Research, Tsukuba Research Center, Higashi 1-1, Tsukuba, Ibaraki 305, Japan Received 13 November 1996 Perovskite oxides, (Ba 0.95 Ca 0.05 ) (Co 1–x Fe x ) O 3–D , are prominent materials for oxida- tive coupling of methane and for CO 2 absorption at high temperature, and these oxides before and after treatment in CH 4 and CO 2 atmosphere were analysed by Mossbauer spectroscopy. The perturbation of microstructure by substitution of Ba sites with Ca, and the electron transfer of mixed valences in Fe and Co ions with the formation of oxygen vacancies at high temperatures, are considered to contribute strongly to the selectivity of CH 4 coupling and the rapid absorption of CO 2 at high temperatures. 1 Introduction Perovskite oxides, (Ba 0.95 Ca 0.05 ) (Co 1-x Fe x ) O 3–D , are prominent catalysts for oxidative couling of methane as well as for deep oxidation of flammable gases, and also are useful materials for CO 2 absorption at high temperature. In CH 4 atmo- sphere, a large amount of CO 2 is formed in the temperature range from 300 to 500°C and nearly 100% selectivity to C2 hydrocarbons is obtained in the tem- perature range from 550 to 750°C [1]. On the other hand, in CO 2 and CO 2 + Air ambients, the perovskite oxides absorbed CO 2 rapidly at temperatures between 600 and 900°C [2]. These remarkable properties could permit potential application of these oxides to the reduction of greenhouse gas from industrial effluents. *) Presented at the International Colloquium "Mossbauer Spectroscopy in Materials Science - MSMS96", September 1996, Lednice, Czech Republic. Czechoslovak Journal of Physics, Vol. 47 (1997), No. 5 517