Adsorption interaction in H2-ZSM-5 system and calculation of the zeolite microchannel parameters

• The real shape of the microchannels for MFI zeolites is identified.
• Places for preferential localization of the sorbate molecules in the zeolite structure is determined.
• Theoretical values of the zeolite microchannel volumes is calculated.
• Calculated and experimental values of Henry constants for hydrogen adsorption at 77 K is compared.

The adsorption interaction of molecular hydrogen with atoms of silicalite-1 and HZSM-5 zeolite frameworks was studied using a representative fragment of the structure including 27 elementary cells with total volume 144 nm3. Potentials of the adsorption interaction between the sorbate molecules and the lattice atoms (O, Si, Al) were calculated. Isopotential surfaces of the intermolecular interaction were also calculated. The isopotential surface with zero adsorption potential Ф0 determines the microchannel shape and topology. Theoretical volumes of the zeolite microchannels and geometrical surface areas Ф0 were calculated. Places where the sorbate molecules are preferentially localized in the zeolite structure (places with the lowest adsorption potential) in the Henry adsorption isotherm region were determined. The calculated and experimental values of the Henry constant for H2 adsorption at 77 K were compared.

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