Three-dimensional mesoporous gallosilicate with Pm3n symmetry and its unusual catalytic performances.
Three-dimensional mesoporous gallosilicate with Pm3n symmetry and its unusual catalytic performances.
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DOI：
10.1002/chem.200701946
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发表时间：
2008-04
期刊：
影响因子：
--
通讯作者：
P. Srinivasu;A. Vinu
中科院分区：
文献类型：
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作者：
P. Srinivasu;A. Vinu
以十六烷基三乙基溴化铵为模板剂，在高酸性介质中，采用低n（HCl）/n（Si）的合成方法，首次成功地制备了具有不同n（Si）/n（Ga）比的三维介孔笼型GaSBA-1材料。所获得的材料已明确地详细表征了几个复杂的技术，包括X射线衍射（XRD），N（2）吸附，高分辨率透射电子显微镜，高分辨率扫描电子显微镜，能量色散光谱，元素映射，和（29）Si魔角旋转NMR光谱。XRD和N2吸附结果表明，GaSBA-1材料的结构与SBA-1相似，具有立方、三维、开窗笼状结构。此外，GaSBA-1材料的比表面积和比孔体积远高于SBA-1二氧化硅，这对于催化应用是非常重要的。Ga阳离子在SBA-1二氧化硅骨架中的量已被发现在控制材料的形貌和孔径方面起关键作用。最后，以叔丁醇为烷基化剂，考察了其在苯酚叔丁基化反应中的催化活性，并与AlMCM-41、FeMCM-41、FeAl-MCM-41和FeSBA-1等介孔催化剂的催化活性进行了比较。此外，各种反应参数，如反应温度，反应物进料比，和时间上的流苯酚转化率在苯酚叔丁基化GaSBA-1催化剂上的效果已被证明。在所考察的催化剂中，GaSBA-1（17）（其中括号中的数字表示n（Si）/n（Ga）比）显示出显著的活性，具有高的苯酚转化率和4-叔丁基苯酚的选择性;发现其优于研究中使用的其它介孔催化剂上级。
Three-dimensional, mesoporous-cage-type, GaSBA-1 materials with different n(Si)/n(Ga) ratios have been successfully prepared for the first time by using a low hydrochloric acid to silicon (n(HCl)/n(Si)) molar ratio in the synthesis gel by templating with cetyltriethylammonium bromide as the structure-directing agent in a highly acidic medium. The obtained materials have been unambiguously characterized in detail by several sophisticated techniques including X-ray diffraction (XRD), N(2) adsorption, high-resolution transmission electron microscopy, high-resolution scanning electron microscopy, energy dispersive spectroscopy, elemental mapping, and (29)Si magic-angle-spinning NMR spectroscopy. XRD and nitrogen adsorption results reveal that the structures of the GaSBA-1 materials resemble that of SBA-1, which possesses a cubic, three-dimensional, cage-type structure with open windows. In addition, the specific surface area and the specific pore volume of the GaSBA-1 materials are much higher than those of the SBA-1 silica, which are very important for the catalytic applications. The amount of Ga cation in the SBA-1 silica framework has been found to play a critical role in controlling the morphology and the pore diameter of the materials. Finally, the catalytic activity in the tert-butylation of phenol with tert-butanol as the alkylating agent has been investigated and the results are compared with those of other mesoporous catalysts such as AlMCM-41, FeMCM-41, FeAl-MCM-41, and FeSBA-1. Moreover, the effect of various reaction parameters such as the reaction temperature, reactant feed ratio, and time-on-stream on the phenol conversion in the tert-butylation of phenol over GaSBA-1 catalysts has been demonstrated. Among the catalysts examined, GaSBA-1(17), in which the number in the parenthesis denotes the n(Si)/n(Ga) ratio, showed remarkable activity with a high conversion of phenol and selectivity to 4-tert-butylphenol; it was found to be superior over other mesoporous catalysts used in the study.