SINGLE-CRYSTAL STRUCTURE-ANALYSIS OF ZEOLITE H-ZSM-5 LOADED WITH NAPHTHALENE

The crystal structure of H-ZSM-5 loaded with 3.68(2) molecules naphtha lene per unit cell was solved by single crystal X-ray diffraction. The space group is orthorhombic, Pnma, with a=19.919(1), b=19.955(2) and c=13.357(1) Angstrom and V=5309(1) Angstrom(3). There are eight Si(11. 96)Al(0.04)O(24)0.46C(10)H(8) (+0.04H(+)) units per unit cell. D-x=1.9 59 Mg m(-3), lambda(MoKalpha)=0.71069 Angstrom and mu(MoKalpha)=0.677 mm(-1). The final R(R(w))=0.044 (0.038), w=1/sigma(2)(F), for 5605 obs erved reflections with I>2.0 sigma(I) measured at 293 K. The inversion of the a and b unit cell parameters (a/b=0.996), first reported by Me ntzen et al. [B.F. Mentzen, M. Sacerdote-Peronnet, J.F. Berar and F. L efebvre, Zeolites, 13 (1993) 485] is confirmed. The straight channel a xis along [010] has elliptical cross-sections with limiting apertures of 4.55x6.44 Angstrom (r(oxygen)=1.35 Angstrom). The 10-ring pores in the sinusoidal channel remain almost circular (major and minor axes be ing about 5.6 and 5.2 Angstrom). Naphthalene molecules are located at the channel intersections. Their long molecular axis (parallel to a mo lecular 2-fold axis) deviates 1.7 degrees from [010]. The angle betwee n the normal on the plane of the molecule and the positive a axis is 4 0.5(3)degrees. The naphthalene molecules form loosely connected chains in the straight channel; the shortest non-bonding C-C distance betwee n neighbouring molecules in the straight channel is 4.57(2) Angstrom.