Title : Oxidation of methane to methanol over pairs of transition metal ions stabilized in the zeolite matrices
Abstract:
Selective oxidation of methane to methanol represents one of the possibilities for gas to liquid transformation of this key energy source. Recently were developed systems based on binuclear transition metal ions sites (formed e.g. by Fe(II) ions) capable of splitting molecular oxygen and forming highly active paired or isolated α-oxygen species which subsequently oxidize methane to methanol. This systems work in squasi-catalytic regime analogously as was reported for Cu-zeolites, but work under isothermal conditions and without need of water vapor for the extraction of oxidation products. In this paper, the mechanism of oxygen activation is studied, as well as the role of the nature of transition metal ions and local arrangement of the binuclear cationic site. It was found that splitting of molecular oxygen and subsequent oxidation of methane is not unique for Fe-ferrieite, but can be connected with a number of systems when fulfilled some requirements on the zeolite topology, framework Al organization and arrangement of the active site. Moreover, the oxygen speciation depends on the conditions of the reaction including subsequent treatment in an oxidative atmosphere. The rate determining step of the whole reaction chain represents desorption of methanol from the active site.
