A Topological Study of the Transition States of the Hydrogen Exchange and Dehydrogenation Reactions of Methane on a Zeolite Cluster

N. B. OKULIK; R. PIS DIEZ; A. H. JUBERT; P. M. ESTEVES; C.J.A. MOTA

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Lugar: Washington; Año: 2001 vol. 105 p. 7079 - 7084

1089-5639

The transition states of the hydrogen exchange and dehydrogenation reactions of methane on a zeolite acid site are studied within the framework of the density functional theory and the atoms-in-molecules theory. The transition state for the hydrogen exchange reaction is found to be characterized by a slightly ionic interaction between a distorted CH5+ structure and the negatively charged zeolite. No free carbocation is found. The dehydrogenation reaction presents a transition state in which three different fragments can be well identified, namely, an almost planar CH3+ structure, a H2 pseudomolecule, and the negatively charged zeolite. The interaction between the fragments can be described as a closed-shell one, typical of rather ionic systems.