Much of the research on the direct conversion of methane has been devoted to its oxidative coupling (OCM), Eq. (1); this involves the catalytic transformation of methane and oxygen to ethene and water at elevated temperature (> 600 °C)
2CH4 + ½ O2 ® C2H6 + H2O (1)
The fundamental aspects of the problem involve both a heterogeneous component which includes the activation of CH4 on (usually doped) metal oxide surfaces, and a homogeneous gas-phase part; in the latter, coupling of the free methyl radicals, generated according to Eq. (2), followed by dehydrogenation C2H6 à C2H4 occurs. Much of the current debates center around the nature of the active metal-oxide surface species. However, these aspects will not be addressed; rather the focus will be on the rate-limiting step of OCM, i.e. the initial homolytic scission of the C-H bond.
MO. + CH4 ® MOH + CH3. (2)
The following questions have been addressed in a combined experimental/computational study and will form the focus of the seminar.
3) In heteronuclear oxide clusters AxByOz, at which site of the terminal A-O or B-O units does the reaction commence?
4) How is the selectivity of initial C-H bond activation of a flexible alkyl group affected by the introduction of a functional group?Specifically: Is "remote and directed functionalization" an issue in the gas-phase reactions of MO.+ with RX (X = functional group)?