Pore size tailoring in large-pore SBA-15 silica synthesized in the presence of hexane.
Pore size tailoring in large-pore SBA-15 silica synthesized in the presence of hexane.
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DOI：
10.1021/la0702178
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发表时间：
2007-05
期刊：
影响因子：
--
通讯作者：
M. Kruk;Liang Cao
中科院分区：
文献类型：
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作者：
M. Kruk;Liang Cao
以聚（环氧乙烷）-聚（环氧丙烷）-聚（环氧乙烷）嵌段共聚物Pluronic P123为模板剂，己烷为胶束膨胀剂，合成了大孔SBA-15硅。小角度x射线散射数据表明，在15℃下形成高度有序的二维六边形材料（SBA-15结构），并在130℃下加热5天后仍能保存。合成的SBA-15二氧化硅的单胞参数约为16.5 nm，热处理后仅略有增加。而经过热处理的材料，煅烧后的单胞参数明显较大（16 nm vs 14 nm）。15℃时形成的SBA-15的孔径分布较窄，以9.5 nm为中心，接近SBA-15通常报道的孔径上限。这种材料的孔隙中明显存在收缩。通过选择适当的处理温度和时间，热处理导致消除收缩并使孔径增加到15 nm或更大。孔隙大小在处理第一天增加最快，但至少持续5天。孔径分布随着处理时间的增加而变宽。孔径的增大似乎主要与煅烧过程中收缩程度的减小（去除模板）和孔壁厚度的减小有关。
Large-pore SBA-15 silicas were synthesized using poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer Pluronic P123 as a template and hexane as a micelle expander. The reaction was initially carried out at 15 degrees C, followed by the heating of the synthesis gel at temperatures from 40 to 130 degrees C. Small-angle X-ray scattering data indicate that highly ordered two-dimensional hexagonal material (SBA-15 structure) formed at 15 degrees C and was preserved even after 5 days of heating at 130 degrees C. The unit-cell parameter for as-synthesized SBA-15 silicas was about 16.5 nm and increased only slightly after the heat treatment, whereas the unit-cell parameter after calcination was appreciably larger (16 vs 14 nm) for materials that were subjected to the thermal treatment. The pore size distribution of SBA-15 formed at 15 degrees C was narrow and centered at approximately 9.5 nm, which is close to the upper limit of pore diameters typically reported for SBA-15. The presence of constrictions in the pores of this material was evident. The heat treatment led to the elimination of the constrictions and to the pore diameter increase to 15 nm or more, tailored by the selection of appropriate treatment temperature and time. The pore size increase was the fastest during the first day of treatment, but it continued for at least 5 days. The pore size distribution broadened as the time of the treatment increased beyond 1 day. The pore size increase appears to be primarily related to the decrease in the degree of shrinkage during the calcination (removal of the template) and the decrease in the pore wall thickness.