Effect of microwave-assisted aging on the static hydrothermal synthesis of zeolite MCM-22

The synthesis of MCM-22 zeolite under static hydrothermal conditions was performed with the synthesis mixture being treated by a microwave-assisted aging process prior to the onset of crystallization using colloidal silica and tetraethyl orthosilicate (TEOS) as silica sources, respectively. The effects of the chemical compositions of the initial solutions and the conditions of microwave treatment for precursors on the synthesis of MCM-22 zeolite were investigated. The microwave-assisted aging was compared with the ultrasound-assisted aging, stirring aging and without any aging processes. The produced samples were characterization by XRD, ICP, FT-IR, and SEM techniques. The microwave-assisted aging for the initial gel can shorten the crystallization time to form MCM-22 phase and broaden the range of SiO2/Al2O3 ratio both for the initial gel and final solid product. Moreover, the increase of the microwave aging temperature and the aging time favors a decrease of crystallization time and particle size. By using microwave-assisted aging process, the pure and high crystallinity MCM-22 product with the SiO2/Al2O3 ratio being as high as 80 can be obtained. Increasing the SiO2/Al2O3 ratio produces the smaller particles of MCM-22.