INFRARED STUDY OF THE FORMATION AND STABILITY OF LA2O2CO3 DURING THE OXIDATIVE COUPLING OF METHANE ON LA2O3

The formation and stability of La2O2CO2 under CO2/He and the CH4/O2/He reaction mixture were investigated by infrared spectroscopy in the 650-750°C range. La2O2CO3 is not stable under flowing He at 650°C. Bulk La2O2CO3 is formed during the oxidative coupling of CH4 at 650°C, although thermodynamic considerations predict that it cannot be generated from the gaseous CO2 produced by the catalytic reaction. On this basis, it is suggested that the dioxymonocarbonate is formed via the surface deep oxidation of CH4 and/or the reaction products. FTIR spectroscopy indicates that 15% of the starting catalyst La2O3 is transformed into La2O2CO3 by the catalytic reaction at 650°C. © 1993 Academic Press, Inc.