Abstract
MCM-22 zeolite was synthesized in various static hydrothermal systems with hexamethyleneimine (HMI) as the structure-directing agent. Synthesis parameters, such as silica source, alkaline source (Na +, K + or NH 4 + ), alkalinity of the reaction mixture, HMI/SiO 2 ratio and seeding, were changed to investigate their effects on the crystallization and morphology of zeolite MCM-22. The produced samples were characterized by XRD, IR, SEM, N 2 physisorption and ICP. Reaction conditions were revealed to influence the induction period and crystallization rate remarkably, and the sodium metasilicate as the silica source, the medium OH −/SiO 2 molar ratio (0.15), the high HMI/SiO 2 molar ratio and the addition of seeding could accelerate the crystallization. Moreover, by altering the reaction parameters, various morphologies of MCM-22 product with different particle sizes were achieved, such as spherical, rose-like, doughnut-like and platelet-like structures. The noteworthy observation was that with K + as the alkaline source instead of Na +, a much shorter induction period and faster crystallization rate were obtained, resulting in a higher crystallinity and a smaller crystal size. K + is more favorable to the formation of MCM-22 crystal than Na + even at very low HMI/SiO 2 ratios.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call