On the mechanism of propane dehydrocyclization over cation-containing, proton-poor MFI zeolite

Document Type

Article

Publication Date

1-1-1998

Abstract

The catalytic behavior of 1/1 cation (Ga, Cu, or In)/framework-Al MFI (MFI is terminology officially sanctioned by the International Zeolite Association, IUPAC commission) zeolite for propane dehydrocyclization was examined under conditions where the materials were initially either in fully protonated or fully metal-loaded states. Metal-loading was accomplished with reductive solid-state ion exchange, and under appropriate conditions, loadings nearing 100% exchange of protons for the reduced univalent cations could be achieved. Ga-MFI is stable to dehydrocyclization reaction conditions to at least ∼800 K, but both In-MFI and Cu-MFI convert to a relatively inactive catalytic state under similar conditions probably by reduction. However, prior to this reduction, In-MFI and Cu-MFI are equivalent or superior to Ga-MFI for the formation of aromatics. The initial zero-protonated state for Ga-MFI was characterized by little or no C-C bond scission to methane, a high benzene/toluene ratio, and a strongly olefinic and branched C4 fraction. On this basis, a reaction mechanism for this state not involving protons, and not bifunctional, is proposed. © 1998 Academic Press.

Publication Source (Journal or Book title)

Journal of Catalysis

First Page

17

Last Page

27

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