Structural study of a cyclopentane sorption complex of fully dehydrated H-ZSM-5 (Si/Al=24), |H3.8(C5H10)1.47|[Al3.8Si92.2O192]-MFI

초록

To study the cyclopentane sorption sites and the effect of sorption on the H-ZSM-5 structure, crystal of H-ZSM-5 were prepared by burning out the tetrapropylammonium cations in air. For the adsorption of cyclopentane into H-ZSM-5 crystal, the crystal was treated with zeolitically dried cyclopentane for 6 h at 297 K, and then evacuated for 600 s at this temperature and 1.1 x 10(-4) Pa. The structure of a single crystal of cyclopentane sorption complex of dehydrated H-ZSM-5 (MFI, |H-3.8(C5H10)(1.47)|[Al3.8Si92.2O192]-MFI, Si/Al = 24) has been determined crystallographically using synchrotron X-radiation in the orthorhombic space group Pnma; a = 20.141(4), b = 19.944(4), c = 13.439(3) angstrom. It was refined using all intensities to the final error indice R-1 = 0.072. The 1.47 cyclopentane molecules per unit cell are located between 5-rings in zigzag channel. The cyclopentane molecules are located perpendicular to the 10-rings of zigzag channel and parallel to the 5-rings of H-ZSM-5 framework at the center of them. Each cyclopentane molecule is held in place by 16 hydrogen bonds between all hydrogen atoms of cyclopentane and framework oxygen atoms of its 5- and 10-rings: C center dot center dot center dot O ca. 3.318 similar to 3.992 angstrom.

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