Characterization of micro- and mesoporosity in SBA-15 materials from adsorption data by the NLDFT method
Characterization of micro- and mesoporosity in SBA-15 materials from adsorption data by the NLDFT method
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DOI：
10.1021/jp010621u
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发表时间：
2001-07-26
影响因子：
3.3
通讯作者：
Neimark, AV
中科院分区：
文献类型：
--
作者：
Ravikovitch, PI;Neimark, AV
以三嵌段共聚物为模板的SBA-15硅质材料因其在大分子催化和分离方面的潜在应用而受到广泛关注。SBA-15材料具有直径为5-30 nm的规则的六角形圆柱形通道阵列，并且除非经过特殊处理，否则具有可察觉的内壁气孔体积，可占总孔隙率的30%。壁内孔包括二氧化硅基质内的微孔以及比主通道窄的中孔。提出了一种从氮吸附等温线估算SBA-15材料孔结构参数的一致性方法。该方法基于圆柱孔内吸附和毛细凝聚的非局域密度泛函理论。NLDFT方法允许计算中孔尺寸分布，并评估孔壁厚度和壁内孔隙度。由NLDFT方法得到的结构参数与几何构型和X射线衍射数据相一致。用NLDFT方法解释了SBA-15上的吸附等温线，解决了最近发表的不同方法测定的孔径之间的一些差异。NLDFT方法也适用于其他微介孔材料。
SBA-15 siliceous materials templated using triblock copolymers have recently received considerable attention because of their potential applications in catalysis and separations of large molecules. SBA-15 materials possess a regular hexagonal array of cylindrical channels of 5-30 nm in diameter and, unless specially treated, an appreciable volume of intrawall pores which may constitute up to 30% of the total porosity. The intrawall pores include micropores within the silica matrix and also mesopores that are narrower than the main channels. We present a consistent method for evaluating the pore structure parameters of SBA-15 materials from the nitrogen adsorption isotherms. The proposed method is based on the nonlocal density functional theory (NLDFT) of adsorption and capillary condensation in cylindrical pores. The NLDFT method allows one to calculate the mesopore size distribution and to evaluate the pore wall thickness and the amount of intrawall porosity. The structural parameters obtained by the NLDFT method are in agreement with geometrical considerations and X-ray diffraction data. Interpretation of adsorption isotherms on SBA-15 by means of the NLDFT method resolves some of the recently published discrepancies between the pore sizes determined from different methods. The NLDFT method is applicable to other micro-mesoporous materials.