TAP reactor investigation of methane coupling over samarium oxide catalysts

The adsorption and reaction characteristics of a Ba/Sr/Sma03 catalyst for methane coupling has been investigated using the TAP (Temporal Analysis of Products) reactor system. Puhed adsorption experiments using methane, oxygen and krypton at temperatures ranging from 17°C to 300°C show that the transient response of methane is similar to that of Kr and is either not adaorbed, or weakly adsorbed on the catalyst. By contrast, oxygen ia strongly adsorbed at temperaturee above 500°C which suggests incorporation into the lattice with possible formation of surface anions. Pump-probe experiments in which methane and oxygen are introduced over the catalyst were aho performed to investigate the effect of lifetimes of suspected surface intermediates on the relative yields of ethane and ethene. It is shown that the relative yields of both species increase with increasing vaIues of the pulse valve time delay between introduction of the oxygen and methane. An explanation of these results using current knowledge and reasonable speculation of the mecbaniim is provided. Keywordx adsorption reaction, methane coupling, samarium oxide, TAP reactor. 0166-9934/91/$03.50