SURFACE-CHEMISTRY IN THE OXIDATIVE COUPLING OF METHANE

The various aspects of the chemistry involved in the oxidative couplin g of methane are considered, with special focus on the surface chemist ry, i.e., on the heterogeneous part of this complex hetero-homogeneous process. The elementary steps which control either the primary or the secondary reactions are analysed in the light of recent results obtai ned with state-of-the-art techniques such as the isotopic transient ki netics and the fast pulse TAP reactor. The two main routes for methane activation via homolytic or heterolytic splitting of the C-H bond are discussed together with the modes of oxygen activation and their depe ndence on the catalyst nature. A tentative list of various active site s corresponding to the specific stages of the reaction is provided. In view of a better understanding of the secondary conversion of ethane into ethylene and further on into COx, recent studies devoted to the o xydehydrogenation of ethane are reviewed with an introduction to the d evelopment of low temperature processes. The occurrence of a single me chanism or of several ones adapted to the various families of active c atalysts is discussed on the basis of the huge amount of literature av ailable at the present time.