CHARACTERIZATION OF BAX2 GD2O3 (X=F, CL, BR) CATALYSTS FOR THE OXIDATIVE COUPLING OF METHANE/

The reactivities of the BaX2/Gd2O3 (X=F, Cl, Br) catalysts in the oxid ative coupling of methane (OCM) reaction have been investigated. It ha s been observed that BaF2, BaCl2, or BaBr2 can significantly improve t he catalytic performance of Gd2O3 The X-ray diffraction (XRD) results indicated that ionic substitutions between the BaX2 and Gd2O3 phases o ccurred during the preparation of the BaX2/Gd2O3 catalysts as well as in the course of the OCM reaction. O-2-TPD, O-2-pulse, and Raman resul ts showed that such ionic substitutions could lead to the increase in the amount of oxygen adsorbed on the BaX2/Gd2O3 catalysts, resulting i n the promotion of catalytic performance. Based on the results of XPS and halide content analyses, we realized that the halides in the BaX2/ Gd2O3 catalysts behaved rather differently in the OCM reaction. The ca talytic performance of the BaX2/Gd2O3 catalysts as related to reaction time can be correlated to the behaviours of the halides in the cataly sts. (C) 1998 Elsevier Science B.V. All rights reserved.