A COMPARATIVE-STUDY OF THE OXIDATION OF METHANE AND ETHANE ON CALCIUMHYDROXYAPATITES WITH INCORPORATED LEAD IN THE PRESENCE AND ABSENCE OFTETRACHLOROMETHANE

The oxidation of methane has been compared with that of ethane on calc ium hydroxyapatite with incorporated lead (PbxxHAp with xx equal to 10 0 Pb/[Pb+Ca] (molar ratio)] in the presence and absence of tetrachloro methane (TCM). In the absence of TCM, the activity reached a maximum o n Pb12HAp for both methane and ethane oxidation. The effects of the in troduction of TCM into the feedstream on the oxidation of methane and ethane were dependent on the hydrocarbon, the partial pressure of TCM and the catalyst composition. In general, the conversions of both meth ane and ethane in the presence of TCM decreased on introduction of sma ll partial pressures of TCM, as reported in our previous publications. However, it is found in the present study that, with higher partial p ressures of TCM, the aforementioned conversions increased, particularl y with increasing time-on-stream, while substantial depressions of the selectivity to CO2 were observed. Significant selectivities to CH3Cl were found with CH4, while no C2H5Cl was observed in the oxidation of ethane, although it is believed that both chlorides are formed and und ergo decomposition. Further information on the role of TCM has been ob tained from XRD and XPS measurements. (C) 1998 Elsevier Science B.V.