Direct synthesis of well-ordered and unusually reactive MnSBA-15 mesoporous molecular sieves with high manganese content.
Direct synthesis of well-ordered and unusually reactive MnSBA-15 mesoporous molecular sieves with high manganese content.
复制标题
DOI：
10.1021/jp063957i
复制
发表时间：
2006-10
期刊：
影响因子：
--
通讯作者：
M. Selvaraj;T. G. Lee
中科院分区：
文献类型：
--
作者：
M. Selvaraj;T. G. Lee
以四水硝酸锰和Pluronic 123三嵌段聚合物[（EO）20（PO）70（EO）20]为原料，通过简单调节水与盐酸的摩尔比（n（H2O）/n（HCl）），首次合成了不同n（Si）/n（Mn）比（4、8、20和50）的介孔MnSBA-15材料。为了考察Mn掺杂对材料结构和织构的影响，在合成凝胶中n（Si）/n（Mn）= 4和n（H2O）/n（HCl）= 295的条件下，采用不同的合成温度合成了MnSBA-15。研究了MnSBA-15的水热稳定性和热稳定性。采用ICP-AES、XRD、N2吸附、ESR、FE-SEM、TEM等手段对煅烧后的MnSBA-15材料进行了表征。ICP-AES研究表明，在二氧化硅孔壁上掺入了更高量的锰，因为通过调节合成凝胶中的n（Si）/n（Mn）比，可以在固定的n（H2O）/n（HCl）摩尔比为295下成功地制备具有高达2.2的n（Si）/n（Mn）比的MnSBA-15。通过XRD和N2吸附测试，研究了MnSBA-15的结构和织构。ESR研究结果清楚地描述了结构和Mn物种配位对SBA-15二氧化硅孔壁的影响，而TEM和FE-SEM图像可以识别MnSBA-15的均匀孔径和绳状六方介孔结构。XRD和N2吸附测试结果表明，随着合成温度的升高，MnSBA-15的晶胞参数、孔径和孔容增大，比表面积和孔壁厚度减小。所制备的六方MnSBA-15材料可以在各种优化条件下作为反式二苯乙烯环氧化生成反式二苯乙烯氧化物的催化剂进行测试，其催化性能也可以与MnMCM-41和ZrMnMCM-41的结果进行比较。
The mesoporous MnSBA-15 materials with different n(Si)/n(Mn) ratios of 4, 8, 20, and 50 have been synthesized, for the first time, using manganese nitrate tetrahydrate and Pluronic 123 triblock polymer [(EO)20(PO)70(EO)20] by simply adjusting the molar ratio of water to hydrochloric acid (n(H2O)/n(HCl)) under direct hydrothermal conditions. For the effect of structural and textural properties with incorporation of manganese, the MnSBA-15 has been synthesized with different synthesis temperatures at the fixed molar ratios of n(Si)/n(Mn) = 4 and n(H2O)/n(HCl) = 295 in the synthesis gel. The hydrothermal and thermal stabilities of MnSBA-15 have also been investigated. The calcined MnSBA-15 materials prepared have been characterized by ICP-AES, XRD, N2 adsorption, ESR, FE-SEM, and TEM. The ICP-AES studies show a higher amount of manganese incorporation on the silica pore walls, as MnSBA-15 with a n(Si)/n(Mn) ratio up to 2.2 can be successfully prepared at a fixed n(H2O)/n(HCl) molar ratio of 295 by adjusting the ratios of n(Si)/n(Mn) in the synthesis gel. The structural and textural properties of calcined MnSBA-15 prepared can be found by the results of XRD and N2 adsorption. The investigation of ESR results clearly describe the effect of structure and Mn species coordination on the SBA-15 silica pore walls while the uniform pore diameter and rope-like hexagonal mesoporous structure of MnSBA-15 can be identified by TEM and FE-SEM images. With increasing synthesis temperature, an increase the unit cell parameter, pore size, and pore volume and a decrease the specific surface area and pore wall thickness of MnSBA-15 can be obviously noted by the results of XRD and N2 adsorption. The hexagonal MnSBA-15 materials prepared could be tested as catalysts in epoxidation of trans-stilbene to produce trans-stilbene oxide under various optimal conditions while their catalytic properties could also be compared to the results of MnMCM-41 and ZrMnMCM-41.