Swift hopping gallium over [AlO4](-) swift tetrahedra in Ga/ZSM-5: a DFT study

摘要

Density functional theory calculations were carried out to investigate gallium species (Ga+, [GaH2](+), and [GaO](+)) stabilization in Ga-exchanged HZSM-5, using cluster modeling approach. Three isomeric gallium positions over [AlO4](-) zeolite fragment at T12 position were found. These isomers are turning into each over with low activation energy barrier and gallium fragment revolves around [AlO4](-) tetrahedron by hopping between cationic positions. Activation energies of gallium fragment hopping were computed and compared for different gallium containing cations. Those barriers were found to be times less than the activation energies of catalytic processes on gallium-exchanged zeolite. (c) 2007 Wiley Periodicals, Inc.