Hui K S, Chao C Y H
Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
J Hazard Mater. 2006 Sep 21;137(2):1135-48. doi: 10.1016/j.jhazmat.2006.03.050. Epub 2006 Apr 25.
The present study reports a green synthesis method for preparing pure (free of fly ash) and ordered MCM-41 materials from coal fly ash at room temperature (25 degrees C) during 24 h of reaction. It was shown that the impurities in the coal fly ash were not detrimental to the formation of MCM-41 at the tested conditions. The influence of initial synthesis pH on material properties of calcined MCM-41 samples was investigated by various techniques such as XRF, XPS, XRD, FTIR, DR-UV-vis, solid state NMR, N2 physisorption, TG-DTA, SEM and TEM. The experimental results showed that the amount of trace elements such as Al, Na, Ti and Fe incorporated into the sample increased with synthesis pH value. More aluminum species were incorporated with tetrahedral coordination in the framework under a high pH value. The particle size of the sample decreased with the synthesis pH value. Samples synthesized at high pH values had a larger pore size and were more hydrothermally stable than those at low pH values. From thermal analysis, it was observed that the synthesized MCM-41 samples showed a high thermal stability. These properties made the synthesized MCM-41 suitable for further processing into more useful materials in a wide range of applications.
本研究报道了一种在室温（25℃）下，通过24小时反应从粉煤灰制备纯（无粉煤灰）且有序的MCM-41材料的绿色合成方法。结果表明，在所测试的条件下，粉煤灰中的杂质对MCM-41的形成并无不利影响。通过多种技术，如X射线荧光光谱法（XRF）、X射线光电子能谱法（XPS）、X射线衍射法（XRD）、傅里叶变换红外光谱法（FTIR）、漫反射紫外可见光谱法（DR-UV-vis）、固态核磁共振法（solid state NMR）、N₂物理吸附法、热重-差示热分析法（TG-DTA）、扫描电子显微镜法（SEM）和透射电子显微镜法（TEM），研究了初始合成pH值对煅烧后MCM-41样品材料性能的影响。实验结果表明，样品中掺入的Al、Na、Ti和Fe等微量元素的含量随合成pH值的增加而增加。在高pH值下，更多的铝物种以四面体配位形式掺入骨架中。样品的粒径随合成pH值的降低而减小。在高pH值下合成的样品孔径更大，且比低pH值下合成的样品具有更高的水热稳定性。通过热分析观察到，合成的MCM-41样品具有较高的热稳定性。这些特性使得合成的MCM-41适合进一步加工成更有用的材料，用于广泛的应用。
