The location of <i>p</i>-xylene in a single crystal of zeolite H-ZSM-5 with a new, sorbate-induced, orthorhombic framework symmetry

Abstract

Si23.92Alo.08048.2Csato (+0.08H+), Mr= 165426, orthorhombic, P2~2~21, a = 20.121 (1), b = 19.820 (1), c= 13.438 (1)A, V= 5359 (3)A 3, Z=4, D~= 2.06 (including p-xylene), D x = 1-80 gcm -3 (for the framework), 2(Cu Ka)= 1.54180 A,/t= 62.7 cm -~, F(000) = 3343.7, T= 293 K, R = 0.039 for 5796 observed reflections with I > 1.0o(/). The adsorption ofp-xylene in the sinusoidal channels is accompanied by a cooperative deformation of the (100) pentasil layers. The resulting strictly alternating shift of adjacent (010) pentasil layers along c changes the monoclinic HZSM-5 framework to orthorhombic symmetry with space group P2~2~2~. This space group is different from the orthorhombic space group of as-synthesized ZSM-5 (Pnma) and has not been reported before. The straight channel parallel to [010] is slightly corrugated. The elliptical cross section has limiting ports of about 6.1 x 4.8 A. The sinusoidal channel, parallel to [100], is elliptical with major and minor axes of about 6.2 and