高岭土微球原位合成L沸石过程中的影响因素

INFLUENCING FACTORS FOR IN-SITU SYNTHESIS OF ZEOLITE L ON CALCINED KAOLIN MICROSPHERES

以高岭土为原料,采用原位晶化法制备了L沸石。制备过程分为两步:首先,将原料高岭土在不同的温度下煅烧,分别得到偏土和高土;然后,在碱性体系下,将其与白炭黑、水、L沸石导向剂以一定的比例混合,在一定温度下水热晶化一定时间,得到L沸石。考察了晶化温度、晶化时间、硅/铝比(n(SiO2)/n(Al2O3))、陈化时间等因素对合成L沸石的影响。结果表明,在n(SiO2)/n(Al2O3)=15、陈化时间30h、晶化温度130℃和晶化时间18h的条件下,可以制备得到高结晶度的L沸石,其中晶化温度和晶化时间是影响合成L沸石相对结晶度的主要因素。采用XRD和SEM对合成的L沸石的晶态结构进行表征和形貌观察。

Zeolite L was prepared by in-situ synthesis method with calcined Kaolin as raw material. Two steps were involved in the preparation： the first step was calcinations of selected Kaolin at different temperatures to get meta-Kaolin and Kaolin; second step was hydrothermal synthesis of zeolite L from meta-Kaolin or Kaolin in alkaline medium mixed with appropriate amounts of other constituents, such as sodium silicate, water, zeolite L initiator under a certain crystallization temperature for a certain crystallization time. Such preparative factors as crystallization temperature, crystallization time, aging time and the mole ratio of n （SiO2）/n （Al2O3） were systematically investigated to discuss their effects on the growth of zeolites L on calcined Kaolin supports. The results showed that the crystallization temperature and time were the main factors affecting the relative crystalline of synthesized zeolite L. The optimum conditions to get phase pure zeolite L with good crystallinity from Kaolin were found to be the n（SiO2）/n（Al2O3） of 15 in the reaction mixture, the aging time of 30h at room temperature, the crystallization temperature of 130℃ and the crystallization time of 18h. The crystal phases of the as-prepared zeolites samples were characterized by X-ray diffraction （XRD） and scanning electronic microscopy （SEM）.