Preparation of monolithic SiO2–Al2O3 cryogels with inter-connected macropores through ice templating
Preparation of monolithic SiO2–Al2O3 cryogels with inter-connected macropores through ice templating
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DOI：
10.1039/b604780g
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发表时间：
2006-08
影响因子：
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通讯作者：
H. Nishihara;S. Mukai;Yusuke Fujii;T. Tago;T. Masuda;H. Tamon
中科院分区：
文献类型：
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作者：
H. Nishihara;S. Mukai;Yusuke Fujii;T. Tago;T. Masuda;H. Tamon
制备了SiO_2-Al_2O_3冻凝胶的大孔单块体。以冰晶为模板制备大孔，并通过冷冻干燥将大孔周围的壁裁剪成多孔冻凝胶。大孔和壁形成蜂窝状结构，这是从样品的横截面的扫描电子显微镜图像确认。证实了大孔的尺寸和壁厚分别在10-20 μm和200-500 nm的范围内。能量色散X射线衍射分析表明，Al原子均匀分散在整个样品中，没有局部聚集。此外，拉曼光谱和27 Al核磁共振谱表明，Al原子通过形成Al-O-Si聚合物网络被引入到SiO2骨架中。氮吸附-脱附测量表明，壁是具有高BET表面积（>700 m2 g−1）和大孔体积（>0.45 cm 3 g−1）的微孔/中孔。此外，NH3-TPD测量显示，样品具有酸性位点，这使得该材料可以用作固体酸催化剂。
Macroporous monoliths of SiO2–Al2O3 cryogels were prepared. Macropores were generated by using ice crystals as the template, while the walls which surround the macropores were tailored as porous cryogels by freeze drying. Macropores and walls formed honeycomb-like structures, which were confirmed from scanning electron microscopy images of cross-sections of the samples. It was confirmed that the sizes of the macropores and the wall thicknesses were respectively in the ranges of 10–20 µm and 200–500 nm. Al mapping analysis by energy dispersive X-ray diffractometry showed that Al atoms were homogeneously dispersed throughout the samples without local aggregation. Moreover, Raman spectroscopy and 27Al NMR spectroscopy indicated that Al atoms were incorporated into the silica framework by forming an Al–O–Si polymeric network. Nitrogen adsorption–desorption measurements indicated that the walls were micro/mesoporous with high BET surface areas (>700 m2 g−1) and large pore volumes (>0.45 cm3 g−1). Moreover, NH3-TPD measurements revealed that the samples had acid sites, which allowed this material to be used as a solid acid catalyst.