16- C-H bond activation of methane by pure and Fe and Al doped silica: A density functional study

Mehmet Ferdi FELLAH, Isik ONAL^*

Department of Chemical Engineering, Middle East Technical University, Ankara, 06531, Turkey, Tel.: +90 312 210 2639 Fax.: +90 312 210 2600 E-mail address: ional@metu.edu.tr (I. Onal)

Abstract

C-H bond activation was studied by means of density functional theory (DFT) calculations as implemented in SPARTAN (2002) at the B3LYP level using 6-31G** as the basis set. Transition state calculations were, in general, performed for determination of activation barriers. Relative energy profiles were determined for pure and Fe and Al doped silica clusters by using coordinate driving calculations. The transition state activation barrier calculated for the Fe doped cluster was found to be 40.4 kcal / mole. Approximate transition state activation barriers obtained for Al doped and pure silica clusters were 66.2 and 73.4 kcal/mole, respectively. The activation barrier for C-H bond activation of methane decreases with substitution of Fe and Al on the silica surface, which theoretically demonstrates the favorable effects of Fe and Al substitution on that surface. The activation energy is substantially decreased from the approximate transition state value of 73.4 kcal / mole for pure silica cluster to 40.4 kcal / mole obtained for the transition state for Fe substituted silica.

Keywords: C-H bond activation, Methane, Silica, Fe doping, Al doping, Density Functional Theory

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