Solid-state transformation of TMA-magadiite into zeolite omega and detailed insights into the crystallization process†
Herein, we have studied the crystallization of zeolite omega by the solid-state transformation of TMA-magadiite at 100 °C for 12 h. The samples prepared at different times were subjected to XRD, SEM, IR, Raman and solid MAS NMR analyses to investigate the crystallization behaviors and changes in the medium-range structure during the synthesis process and a comprehensive mechanism was proposed. It has been demonstrated that the 5Rs and 6Rs in magadiite are partially retained in the system and participate in the growth of zeolite omega. The 4Rs were formed after heating for 4 h. The synthesis time of the zeolite omega using this method is shorter than that using the magadiite hydrothermal conversion method (about 72 h), because special composition building units, which have similarities to the structure of zeolite omega, were formed and adsorbed on the surface of the TMA-magadiite, and then provided a growth surface for the synthesis of targets. In addition, recycling the waste mother liquid produced in the preparation of the precursor was done to achieve the low cost and green synthesis. Finally, several factors influencing the reaction are discussed.