Khodakov Andrei Y, Zholobenko Vladimir L, Impéror-Clerc Marianne, Durand Dominique
Laboratoire de Catalyse de Lille, Université des Sciences et Technologies de Lille, Bât. C3, Cité Scientifique, 59655 Villeneuve d'Ascq, France.
J Phys Chem B. 2005 Dec 8;109(48):22780-90. doi: 10.1021/jp052786z.
The initial stages of SBA-15 synthesis have been studied by using in situ time-resolved small-angle X-ray scattering with a synchrotron radiation source. The quantitative analysis of X-ray scattering and diffraction intensities allows the structures of intermediates to be identified at the different stages of SBA-15 synthesis. Following tetraethylorthosilicate (TEOS) addition, an intense small-angle scattering and an associated secondary maximum are observed, which are attributed to non-interacting surfactant template micelles encrusted with silicate species. After 25-30 min of the reaction, the broad scattering disappears and narrow Bragg diffraction peaks typical of hexagonally ordered structure are observed. The cylindrical micelles identified from X-ray scattering data appear to be the direct precursors of 2D hexagonal SBA-15 structure. Just after the formation of the SBA-15 hexagonal phase, the cylindrical micelles are only weakly linked in the hexagonal structure. As the synthesis proceeds, the solvent in the void volume between the cylindrical micelles is gradually replaced by more dense silicate species. The unit cell parameter of SBA-15 is progressively decreasing during the SBA-15 synthesis, which can be related to the condensation and densification of silicate fragments in the spaces between the cylinders. The volume fraction of the 2D hexagonally ordered phase is sharply growing during the first 2 h of the reaction. The inner core radius of SBA-15 material remains almost constant during the whole synthesis and is principally affected by the size of the poly(propylene oxide) inner core in the original cylindrical micelles.
利用同步辐射源的原位时间分辨小角X射线散射研究了SBA - 15合成的初始阶段。对X射线散射和衍射强度的定量分析能够识别SBA - 15合成不同阶段中间体的结构。加入正硅酸乙酯（TEOS）后，观察到强烈的小角散射和相关的二级最大值，这归因于包裹着硅酸盐物种的非相互作用表面活性剂模板胶束。反应25 - 30分钟后，宽散射消失，观察到典型的六方有序结构的窄布拉格衍射峰。从X射线散射数据确定的圆柱形胶束似乎是二维六方SBA - 15结构的直接前体。在SBA - 15六方相形成后，圆柱形胶束在六方结构中只是弱连接。随着合成的进行，圆柱形胶束之间空隙体积中的溶剂逐渐被更致密的硅酸盐物种取代。在SBA - 15合成过程中，SBA - 15的晶胞参数逐渐减小，这可能与圆柱体之间空间中硅酸盐碎片的缩合和致密化有关。在反应的前2小时内，二维六方有序相的体积分数急剧增加。在整个合成过程中，SBA - 15材料的内核半径几乎保持不变，并且主要受原始圆柱形胶束中聚环氧丙烷内核尺寸的影响。
