EFFECT OF TETRACHLOROMETHANE AS A GAS-PHASE ADDITIVE ON THE OXIDATIVE DEHYDROGENATION OF ETHANE OVER MAGNESIUM PHOSPHATE

The oxidative dehydrogenation of ethane to ethylene on Mg-3(PO4)(2) has been investigated in the presence and absence of tetrachloromethane (TCM). The homogeneous reaction proceeded extensively at temperatures above 998 K, while the heterogeneous reaction on the phosphate occurred at temperatures below 823 K. Selectivity to ethylene in the presence of TCM between 723 and 823 K was six times higher than that in the absence of TCM with a concomitant decrease in the conversion of ethane under the present reaction conditions, while no effects of TCM were observed at temperatures between 998 and 1098 K. Chlorinated species were detected on the surface of the used catalysts after contact with TCM even at temperatures as low as 723 K. The ratio of Cl/Mg measured by XPS after the ethane reaction was strongly influenced by both the relative amounts of C2H6 and O-2 in the reactant stream and the reaction temperature.