The Location of p-Dichlorobenzene in a Single Crystal of Zeolite H-ZSM-5 at High Sorbate Loading

摘要

The crystal structure of a high-loaded complex of H-ZSM-5 with eight molecules of p-dichlorobenzene per unit cell has been solved by single-crystal X-ray diffraction. The orthorhombic space group P212121 with a = 20.102(6), b = 19.797(9), c= 13.436 (3) A and V = 5347 (3) A3 has four Si23.92Al0.08O48.2C6H4Cl2 units per unit cell. Dx = 2.164Mgm-3, λ(AoKα) = 0.71073A and μ(MoKα) = 0.876mm-1. The final R(wR) = 0.046 (0.039), w = I/σ2(F), for 6090 observed reflections with I > 1.0σ(I) measured at 293 K. The straight channel parallel to [010] is slightly corrugated. The elliptical cross sections have limiting apertures of 6.0x4.9 A (roxygen = 1.35 A). The sinusoidal channel parallel to [100] is elliptical with major and minor axes of 6.1 x 4.8 A, respectively. One of the two independent p-dichlorobenzene molecule lies at the intersection of the straight and sinusoidal channels with its long molecular axis almost parallel to (100) and deviating ~ 8° from [010]. The second p-dichlorobenzene molecule is in the sinusoidal channel. Its long molecular axis deviates almost 7° from [100] and is practically parallel to (010). The structural aspects are in all details comparable to those in the high-loaded H-ZSM-5/p-xylene complex [van Koningsveld, Tuinstra, van Bekkum & Jansen (1989). Acta Cryst. B45, 423-431], except for the main interaction forces between the p-dichlorobenzene molecules at the channel intersection.