The nucleation period for TPA-silicalite-1 crystallization determined by a two-stage varying-temperature synthesis
The nucleation period for TPA-silicalite-1 crystallization determined by a two-stage varying-temperature synthesis
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DOI：
10.1016/s1387-1811(99)00064-5
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发表时间：
1999-10-01
影响因子：
5.2
通讯作者：
Sterte, J
中科院分区：
文献类型：
--
作者：
Li, Q;Creaser, D;Sterte, J
两阶段变温合成程序（涉及结晶过程中某个点的温度快速变化）被应用于 TPA-silicalite-1 离散胶体颗粒的合成。随着在初始合成温度下的持续时间延长，晶体浓度和最终晶体尺寸发生变化，直到它们大约等于在初始温度下完全合成所获得的那些。在结晶的这一点上，可以得出结论，成核阶段已完成。对于在 60、80 和 100 摄氏度下进行的合成，通过该方法确定的成核期的持续时间约为 100 小时。 4 至 6 小时且少于 2 小时。分别。因此，对于该系统，成核是一个连续的过程，并且发现最初较高的成核速率在整个成核期间下降。在所有情况下，成核都发生在诱导期，几乎没有或没有观察到晶体生长，这解释了为什么合成产生的产物具有相当窄的晶体尺寸分布。对于两阶段合成，如果在成核期完成后进行温度变化，则第二合成温度仅控制晶体的线性生长速率和获得的silicalite-1的最终产率。 (C) 1999 Elsevier Science B.V. 保留所有权利。
A two-stage-varying-temperature synthesis procedure, which involves a rapid change in temperature at some point during the course of crystallization, was applied to the synthesis of discrete colloidal particles of TPA-silicalite-1. As the duration of the period at the initial synthesis temperature was extended, the crystal concentration and ultimate crystal size varied until they were approximately equal to those obtained for a complete synthesis at the initial temperature. At this point in the crystallization, it was concluded that the nucleation stage was completed. For syntheses performed at 60, 80 and 100 degrees C, the duration of the nucleation period determined by this method was about 100 h. between 4 and 6 h and less than 2 h. respectively. Thus, nucleation, for this system, is a continuous process, and it was found that the rate of nucleation, which is initially high, declines throughout the nucleation period. In all cases, nucleation occurred during an induction period when little or no crystal growth was observed, which explains why the syntheses yielded a product with a rather narrow crystal size distribution. If, for the two-stage syntheses, the temperature change was made after completion of the nucleation period, the second synthesis temperature controlled only the linear growth rate of the crystals and the final yield of silicalite-1 obtained. (C) 1999 Elsevier Science B.V. All rights reserved.