表面活性剂和水溶性聚合物对合成A型沸石的影响(续前)

The crystallization of zeolite NaA in the presence of various surfactant(sodium dodecyl sulfate,Aerosol OT,cetyltrimethylammonium bromide,Nonidet P40)and of poly(ethylene glycol)was studied and compared to a control crystallization with no additive present.Crystalline-growth curves were determined by quantitative X-ray diffraction studies of samples removed periodically from the hydrothermal system.Crystal-size distributions and linear crystal-growth rates were determined by scanning electron microscopy,and from these date,nucleation profiles were constructed.Changes in the concentrations of soluble aluminum and silicon in the aqueous phase of the hydrothermal system during crystallization were monitored by inductively coupled plasma atomic emission spectroscopy.The additives were shown to lengthen the prenuleation period,shorten the nucleation period,and increase the linear rate of crystal growth.All but Aerosol OT increased the total number of nuclei produced and gave crystals with a reduced mean size and narrower size distribution.These effects may be attributed to and effective reduction in the water content of the hydrothermal system.Aerosol OT reduced the number of nuclei produced and gave larger crystals,and effect that may be attributed to a specific interaction with aluminum species.In general,the aluminum concentration in the aqueous phase was found to decrease dramatically during the period of crystal growth.

表面活性剂和水溶性聚合物对合成A型沸石的影响(待续)

研究了不同表面活性剂———十二烷基硫酸钠(K 12)、二辛基磺基琥珀酸钠(AOT)、辛基三乙基溴化铵、Nonidet(P40)和聚乙二醇对A型沸石晶化影响 ,并与没有添加剂的A型沸石晶化做了比较。通过对反应的水热体系不同时间点采样的X衍射 ,得出了晶化动力学曲线 ;对样品通过扫描电镜(TEM) ,可以得出粒度分布和线性晶化成长速率 ,从这些数据可以绘制出粒度分布直方图 ;通过等离子体原子发射光谱(ICP/AES) ,测出了水热体系液体中不同时间硅、铝浓度的变化情况。研究表明 :加入添加剂后使预成核时间增长、成核时间缩短 ,加快了晶化速率 ;除了AOT外 ,均可增加核数量 ,减小粒度并使粒度分布变窄。这些影响可能是由于添加剂的加入 ,使水热体系中水含量的降低而引起的。而AOT的加入使核数量减少、粒度增大 ,可能是由于它与铝之间有特殊的作用。水热体系液体中铝的浓度在晶体成长期显著下降。