Ma. Johnson et al., AN AB-INITIO STUDY ON THE OXIDATIVE COUPLING OF METHANE OVER A LITHIUM-DOPED MGO CATALYST - SURFACE-DEFECTS AND MECHANISM, JOURNAL OF PHYSICAL CHEMISTRY B, 101(16), 1997, pp. 3196-3201
We present a study on the catalytic cycle responsible for coupling of
methane by molecular oxygen over a lithium-doped magnesium oxide catal
yst. To elucidate the mechanism by which methyl radicals are produced
and the active sites are regenerated, geometries and energies of relev
ant reaction intermediates were determined using an ab initio embedded
cluster model. Our results suggest a new mechanism that requires only
one active site and does not involve the energetically costly process
of creating lattice vacancies. This mechanism is more consistent with
the available experimental data than the Ito-Lunsford mechanism propo
sed earlier.