Changes of medium-range structure in the course of crystallization of mordenite from diatomite

• Silicate-ring structures in diatomite were studied.
• Changes of medium-range structure during the crystallization were investigated.
• Formation pathway for mordenite was proposed.

Mordenite was synthesized from diatomite in a template-free system. The crystallization behavior and changes of medium-range structure during the crystallization were studied by X-ray diffraction, scanning electron micrograph, vibrational spectroscopy and high-energy X-ray diffraction. It is indicated that major 4-membered rings are formed at a stage later than that of 5-membered ring in the course of crystallization. Diatomite has also been demonstrated to consist of 5-membered rings and various rings lager than 5-membered ring. A formation pathway for mordenite from diatomite could be proposed that 5-membered rings formed initially are undergoing accommodation of 4-membered rings around them to form mordenite.

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