Akademik Veri Yönetim Sistemi
18th European Powder Diffraction Conference, Padua, İtalya, 30 Ağustos - 02 Eylül 2024, ss.36-37, (Özet Bildiri)
The production of zeolites from kaolin and halloysite clays involves high-temperature treatments to transform the feedstock.
This process leads to the formation of meta-forms (metakaolin and metahalloysite) used as precursors in zeolite synthesis.
Specifically, kaolin calcined above 950 °C undergoes Al-Si spinel crystallization and amorphous silica release, impacting the
Si/Al molar ratio and subsequently affecting the type of zeolite synthesized [1].
This study focuses on the thermal behavior of kaolin and halloysite, employing in situ high-temperature X-ray diffraction at
the SESAME Synchrotron MS/XRD beamline [2]. Samples were heated in quartz capillaries using an Oxford FMB gas blower,
following specific protocols: for dehydroxylation analysis, clays were heated to 400 °C at a 5 °C/min ramp, with data collected
every 25 °C up to 800 °C; for spinel crystallization studies, the heating ramp was maintained at 5 °C/min, with data acquisition
every 5 °C from 900 to 999 °C. Findings indicate complete dehydroxylation at 575 °C for kaolin (Fig. 1d) and 500 °C for
halloysite (Fig. 1a), and both minerals experienced Al-Si spinel crystallization at 940 °C (Fig. 1c, 1f). An α to β quartz phase
transition was observed between 400 and 575°C (Fig. 1b, 1e).
Differential thermogravimetry analysis of the clays aligned with existing literature, while N2 adsorption-desorption
measurements of the zeolites revealed high BET surface areas, signifying a hierarchical intercrystalline structure of micro and
mesopore formation. The presence of mesoporosity, a result of Al-Si spinel crystallization, was further confirmed through low-
angle XRD. This study establishes a direct correlation between the calcination time and the resulting zeolite type, highlighting
the novel in situ analysis of Al-Si spinel crystallization. The unprecedented observation of Al-Si spinel crystallization, not
documented in previous in situ studies, was of particular significance. These insights advance the understanding of thermal
transformations occurring in clay mineralogy resulting in tailoring the obtained zeolite type.
[1] P. Pasabeyoglu, G. Moumin, L. de Oliveira, M. Roeb, B. Akata, Solarization of the zeolite production: Calcination of kaolin as
proof-ofconcept, J. Clean. Prod. 414 (2023) 137611. https://doi.org/10.1016/j.jclepro.2023.137611.
[2] M. Abdellatief, M. Al Najdawi, Y. Momani, B. Aljamal, A. Abbadi, M. Harfouche, G. Paolucci, Operational status of the X-ray
powder diffraction beamline at the SESAME synchrotron, J. Synchrotron Radiat. 29 (2022) 532–539.
https://doi.org/10.1107/S1600577521012820.