Influence of the Nature of the Exchanged Ion onn-Hexane Aromatization Activity of Pt–M–ETS-10:Ab InitioCalculations on the Location of Pt

Author： Waghmode S.B. Das T.K. Vetrivel R. Sivasanker S.

Publisher： Academic Press

ISSN： 0021-9517

Source： Journal of Catalysis, Vol.185, Iss.2, 1999-07, pp. : 265-271

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Abstract

The activity of Pt–M–ETS-10 samples exchanged with different alkali metals (M=Li, Na, K, Rb, or Cs) in the aromatization ofn-hexane depends on the nature of the exchanged metal ion (M). A distinct relationship between the intermediate electronegativity (S_int) of the different metal-exchanged ETS-10 samples and benzene yield is reported, suggesting the activation of Pt by the basicity of the exchanged metal. Results ofab initioHartree–Fock calculations on cluster models representing Pt–M–ETS-10 corresponding to the presence of Pt nearer to [TiO₆]^2-and [SiO₄] groups reveal that the presence of Pt nearer to [TiO₆]^2-is energetically more favored and results in a gain of electron charge by Pt. The studies also suggest an increasing amount of electron transfer from the model clusters of ETS-10 to the Pt with increase in the electropositive character of the exchanged metal. It appears therefore, that small Pt clusters residing nearer to [TiO₆]^2-accessible from the 12-MR channels are the likely active sites inn-hexane aromatization over Pt–M–ETS-10.