不同形貌和晶粒大小ZSM—5分子筛合成的研究

考察了K2O－AI2O3－SiO2-TPABr(四丙基溴化铵）－H2O体系中水热合成制备ZSM－5分子筛时各因素对晶粒大小和形貌的影响。降低投料硅铝比、增加K^ 含量、使用碱性较弱的K2CO3或升高晶化温度都能促进产品ZSM－5分子筛晶粒的增大。提高投料硅铝经或引入NO3^-易使产物形貌趋于球形。采用晶化前预老化的方法，可以方便地制备出不同晶粒大小（1．0－40μm）且不含微晶、无微晶聚集体的产品。

STUDIES ON THE SYNTHESISOF ZEOLITE ZSM-5 WITH DIFFERENT MORPHOLOGY AND CRYSTAL SIZE

Factors affecting the hydrothermal crystallization of zeolite ZSM-5 such as n(SiO2)/n(Al2O3), crystallization temperature, alkalinity, oxyanion, seeding and aging, from K2O-Al2O3-SiO2-TPABr(tetrapropyl ammonium bromide)-H2O aluminosilicate gels were studied. The high crystalline ZSM-5 zeolites of larger size were obtained from these gels, and their crystal morphology tended to transform from spherulite to euhedralite and grew larger when increasing either Al2O3 content or crystallization temperature or replacing KOH by less alkaline K2CO3. Oxyanion such as NO-3 played a role to some extent in preventing the formation of euhedralite in richer alumina recipe. Compared with seeding, a combination of aging and crystallization was more facile in tailoring of crystal size from 1. 0 to 40 μm. It was shown by IR that the aged gel did not have the structural characteristics of ZSM-5 crystallite. In addition, the observation that no XRD peak broadening of (002) diffraction was observed as compared with standard sample α-SiO2 revealed the absence of tiny crystals (less than 0.5 μm) in as-synthesized zeolite samples.