Synthesis of Zeolite Omega by the Magadiite Conversion Method and Insight into the Changes of Medium-Range Structure during Crystallization

Abstract

Zeolite omega has been synthesized directly in the presence of tetramethylammonium ions (TMA+) by the magadiite conversion method. Using the reactive gel composition: 20SiO2: Al2O3: 3.6Na2O: 180H2O: 0.96TMABr, pure and high crystalline zeolite omega could be obtained at 100 °C for 72 h. It is found that most of the long-range order structure of magadiite was retained, even though part of it was collapsed, as its primary structure during the crystallization process. Meanwhile, the crystallization behavior and changes of medium-range structure in the synthesis were characterized. The growth of zeolite omega occurs on the surface of magadiite, and 4-membered rings probably from the connection by 5-membered rings are formed after 10 h. The Al atoms prefer to occupy the position in 6-membered rings of gmelinite in zeolite omega. The influence of reaction time, temperature, and composition in starting gel was examined.