Vietnam Journal of Catalysis and Adsorption

RESEARCH PAPER

open access logo 200x200Potassium Coordination in K-KFI Zeolite Investigated by Synchrotron X-ray Diffraction

Son T. Le, Binh T. Nguyen, Trong D. Phammail

Faculty of Chemistry, VNU University of Science, 19 Le Thanh Tong, Hoan Kiem, Hanoi, Vietnam

ABSTRACT

The KFI (Si/Al=4) zeolite was prepared by a hydrothermal method using 18-crown-6 as the organic structure directing agent. The synthesized material was characterized by in-house X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and N2 adsorption isotherm. The material possessed a high crystalline structure with well-defined cubic shape, large surface area, and high micropore volume. The atomic positions of atoms, potassium locations and occupancies parameters were determined from the refined Synchrotron X-ray diffraction pattern of potassium exchanged KFI. The Rietveld refinement results indicated that K+ cations were located at three different sites (SI’, SII, and SIII), at which site SII at the puckered 8-membered ring of the pau-cages is the most stable site. The elucidation of extra-framework cation sites in zeolites is crucial in understanding the structure-property relationship for zeolite catalysts and adsorbents.

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