| Summary: | ZSM-5 zeolite is the synthetic counterpart to mutinaite. After thermal activation of the as-synthesized form, the symmetry of the ZSM-5 zeolite is lowered to the monoclinic <i>P</i>2<sub>1</sub>/<i>n</i>. ZSM-5 then undergoes a polymorphic displacive phase transition from the monoclinic <i>P</i>2<sub>1</sub>/<i>n</i> to the orthorhombic <i>Pnma</i>, <i>Pn</i>2<sub>1</sub><i>a</i> or <i>P</i>2<sub>1</sub>2<sub>1</sub>2<sub>1</sub> space groups, which occurs upon heating. This phase transition can be influenced by factors such as the type and amount of sorbate molecules present in the zeolite channels. ZSM-5 has many applications, including as a catalyst or sorbent in various industries, where high thermal stability is required. In this study, four ZSM-5 zeolites with different Si/Al ratios were investigated by synchrotron X-ray powder diffraction at both room temperature and high temperature conditions to determine the effects of chemical composition on the structural response of the zeolite lattice. The results showed that the ZSM-5 zeolites retained their crystallinity and structural features throughout the thermal treatment, indicating that they could be used as effective acid catalysts. Distortions in the zeolite framework can occur after TPA+ decomposition and thermal activation, affecting thermal regeneration and efficiency. The charge balance in ZSM-5 is achieved by the formation of Brønsted acid sites, and variations in bonding geometries are influenced by the initial Si/Al ratio.
|
|---|