Temperature Induced Monoclinic to Orthorhombic Phase Transition in Protonated ZSM-5 Zeolites with Different Si/Al Ratios: An In-Situ Synchrotron X-ray Powder Diffraction Study
Nicola Precisvalle,
Maura Mancinelli,
Matteo Ardit,
Giada Beltrami,
Lara Gigli,
Alfredo Aloise,
Enrico Catizzone,
Massimo Migliori,
Girolamo Giordano,
Vincenzo Guidi,
Annalisa Martucci
Affiliations
Nicola Precisvalle
Physics and Earth Science Department, University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy
Maura Mancinelli
Physics and Earth Science Department, University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy
Matteo Ardit
Physics and Earth Science Department, University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy
Giada Beltrami
Physics and Earth Science Department, University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy
Lara Gigli
Materials Characterization by X-ray Diffraction (MCX) Beamline, Elettra-Sincrotrone Trieste S.C.p.A., SS14-km 163,5 Science Park AREA, I-34149 Basovizza, Italy
Alfredo Aloise
Department of Physical and Chemical Sciences, University of L’Aquila, Via Vetoio (COPPITO 1–2), I-67100 L’Aquila, Italy
Enrico Catizzone
Department of Environmental and Chemical Engineering, University of Calabria, Via Bucci Cubo 44a, I-87036 Rende, Italy
Massimo Migliori
Department of Environmental and Chemical Engineering, University of Calabria, Via Bucci Cubo 44a, I-87036 Rende, Italy
Girolamo Giordano
C.E.Ca.S.P. Lab., University of Calabria, Via Bucci, I-87036 Rende, Italy
Vincenzo Guidi
Physics and Earth Science Department, University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy
Annalisa Martucci
Physics and Earth Science Department, University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy
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 P21/n. ZSM-5 then undergoes a polymorphic displacive phase transition from the monoclinic P21/n to the orthorhombic Pnma, Pn21a or P212121 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.
