高等学校化学学报 ›› 2020, Vol. 41 ›› Issue (11): 2449-2456.doi: 10.7503/cjcu20200289

• 无机化学 • 上一篇    下一篇

硅溶胶粒度与分布对高硅铝比镁碱沸石合成的影响机理

董乐, 黄星亮(), 任俊杰, 代小平, 刘宗俨, 田洪锋, 王志东, 吴晓彤   

  1. 中国石油大学(北京)化学工程与环境学院, 北京 102249
  • 收稿日期:2020-05-25 出版日期:2020-11-10 发布日期:2020-11-06
  • 通讯作者: 黄星亮 E-mail:xlhuang@cup.edu.cn
  • 基金资助:
    国家自然科学基金(U1662104)

Influence Mechanism of Particle Size and Distribution of Silica Sol in the Synthesis of Ferrierite Zeolite with High SiO2/Al2O3 Ratio

DONG Le, HUANG Xingliang(), REN Junjie, DAI Xiaoping, LIU Zongyan, TIAN Hongfeng, WANG Zhidong, WU Xiaotong   

  1. College of Chemical Engineering and Environment,China University of Petroleum,Beijing 102249,China
  • Received:2020-05-25 Online:2020-11-10 Published:2020-11-06
  • Contact: HUANG Xingliang E-mail:xlhuang@cup.edu.cn
  • Supported by:
    Supported by the National Natural Science Foundation of China(U1662104)

摘要:

以硅溶胶为硅源, 在不同碱度的溶液中对其进行前处理, 制得不同粒度与分布的硅溶胶母液, 并以此为原料合成了高硅铝比镁碱沸石分子筛(FER zeolite). 通过激光粒度分析仪(LPSA)、 傅里叶变换红外光谱(FTIR)、 X射线衍射(XRD)、 扫描电子显微镜/能量色散X射线光谱(SEM-EDS)和X射线荧光(XRF)等对母液和产物进行了表征, 考察了碱度对硅溶胶粒度特性和分子筛晶化过程以及产物性质的影响. 结果表明, 随着碱度增加, 硅溶胶母液的粒径逐渐增大, 对应于溶液中更多的Q3硅单元向Q2硅单元转变. 在低碱度下, 高聚合度的Q3硅单元倾向于使晶化过程遵循固相转化机理, 生成大片纯相镁碱沸石, 且产物的相对结晶度和固体收率均较高; 而在高碱度下, 大量活性的Q2硅单元则易于使凝胶成块, 晶化过程遵循液相转化机制, 产物尺寸较小且含有杂晶, 相对结晶度和固体收率均较低.

关键词: 镁碱沸石, 高硅铝比, 水热合成, 硅溶胶, 粒度及分布

Abstract:

Silica sol mother liquids with different particle sizes and distributions were prepared by pre- treating silica sol in solutions of different alkalinities, and then they were used as silicon source to synthesize high-silica ferrierite(FER) zeolites. Mother liquids and products were characterized by means of laser particle size analyzer(LPSA), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM-EDS) and X-ray fluorescence(XRF) spectroscopy. The influences of alkalinity on the particle size characteristics of silica sol mother liquid, the crystallization process, and products were investigated. Results indicated that the particle size of the silica sol mother liquid gradually increased with the alkalinity, corresponding to the transition of more Q3 silicon units to Q2 silicon units in the solution. At low alkalinity, Q3 silicon units with a high degree of polymerization tended to make crystallization follow the solid-phase transformation mechanism to synthesize pure phase big ferrierite crystals with high yield and relative crystallinity; while at high alkalinity, a large number of active Q2 silicon units tended to make the gel coagulate with each other, and the crystallization process followed the liquid-phase transformation mechanism, affording small product with low purity and yield.

Key words: FER zeolite, High SiO2/Al2O3 ratio, Hydrothermal synthesis, Silica sol, Particle size and distribution

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