A comparative study of the oxidation of methane and ethane on calcium hydroxyapatites with incorporated lead in the presence and absence of tetrachloromethane

Abstract

The oxidation of methane has been compared with that of ethane on calcium hydroxyapatite with incorporated lead (PbxxHAp with xx equal to 100 Pb/[Pb+Ca] (molar ratio)] in the presence and absence of tetrachloromethane (TCM). In the absence of TCM, the activity reached a maximum on Pb12HAp for both methane and ethane oxidation. The effects of the introduction 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 methane and ethane in the presence of TCM decreased on introduction of small partial pressures of TCM, as reported in our previous publications. However, it is found in the present study that, with higher partial pressures of TCM, the aforementioned conversions increased, particularly with increasing time-on-stream, while substantial depressions of the selectivity to CO 2 were observed. Significant selectivities to CH 3Cl were found with CH 4, while no C 2H 5Cl was observed in the oxidation of ethane, although it is believed that both chlorides are formed and undergo decomposition. Further information on the role of TCM has been obtained from XRD and XPS measurements.