The Synthesis Of ZSM-5Zeolites And Studies Of Crystallinity And Crystal Size

ZSM-5zeolite, successfully developed by Mobil Oil in1972, with high Si/Al ratio, and three-dimensional pore structure of straight-through-hole, has a typical thermal and acid stability and excellent hydrophobicity properties. Small crystals ZSM-5zeolite have larger external surface, high surface energy and shorter channels by comparing with the big zeolites. So, reducing the partical size is one of the ways to impoving the catalysts. The influence factors of the crystallinity and crystal size of ZSM-5zeolite was studies in this thesis. The samples were characterized by XRD, SEM, BET, FT-IR and LPSA etc.Result show that:1. The high crystallinity ZSM-5zeolite can only be synthesized with the high concentration aluminosilicate gel formed in the condition of certain high alkalinity. ZSM-5zeolite crystallization process is based on the solid-solid transformations mechanism2. ZSM-5zeolite with high crystallinity can be synthesized at180℃for36h after aging for12h at room temperature using n-butylamine as template. The higher of the crystallization temperature, the higher of the relative crystallinity; As the increase of aging and crystallization time, the relative crystallinity become higher at first, then lower later.3. The higher of the crystallization temperature and the concentration of aluminosilicate gel, the higher of the relative crystallinity and average particle size, the sample of the highest crystallinity can be synthesized with the aging time of24h at room temperature and the crystallization time of24h at180℃by seeding method, the aging time have a small influence on the crystal size.4. Extend the aging time or crystallization time all can be succeed synthesis ZSM-5zeolite by direct method, but other phase peaks appear when too long crystallization time. In order to achieve higher relative crystallinity and smaller ZSM-5zeolite, we use stirring method at aging time.5. In the three synthesis methods, the seeding method can get smallest crystal; the sample synthesized by template method has the best thermal stability; and at repeat rate the sample synthesized by direct method has not as good as the samples synthesized by template method and seeding method.