Location of the tripropylbenzylammonium ion (P3BZY) in the as-synthesized zeolite ZSM-5 (Si/Al = 28): A study by solid-state NMR, computer simulations and X-ray synchrotron powder diffraction

The crystal structure of a zeolitic microporous material having the MFI (ZSM-5) framework type and synthesized in the presence tripropylbenzylammonium (P3BZY templating agent) has been investigated by combined solid-state nuclear magnetic resonance (NMR), computer simulations and X-ray synchrotron powder diffraction (XRPD). The unit-cell (uc) content of the material is ∣H0.7Na2.6(NC16H28)4∣[Al3.3Si92.7O192]-MFI (in short ZSM-5 · 4P3BZY). Its framework symmetry is most likely Pnma and the aromatic ring of the benzyl group, which is located in the straight channel (SC), induces a rather strong elliptical deformation (ε = 1.134) of its 10-ring pore opening. The inter-molecular CH3CH3 distances between terminal methyl groups of P3BZY in the zig-zag channel (ZZ), and the CH3cb4 (aromatic benzyl ring) distances in the straight channel are 3.81 and 3.19 Å, respectively. The nitrogen atom of the P3BZY template is centered at the channel intersection and the occluded molecule fits very tightly into the MFI channel system. The 2.6 sodium cations of the formula could not be unambiguously revealed by difference-Fourier maps. Two plausible Na+ locations were simulated by computer simulations (MM: molecular mechanics) at x/y/z = 0.181/0.176/0.886 and −0.084/0.562/0.478 in the zig-zag and straight channels, respectively. These sites were not structurally refined.