Denoyel R, Meneses J M, Armatas G S, Rouquerol J, Unger K K, Pomonis P J
Madirel, CNRS-Université de Provence, Centre de St Jérôme, 13397 Marseille Cedex 20, France.
Langmuir. 2006 Jun 6;22(12):5350-7. doi: 10.1021/la0604681.
In this work, we compare the surface and morphometric properties of the pore networks in four silicas (code names Fr1428, Fr474, Fr1386, and MM1164) with different random porosities using the adsorption isotherms of two different probe adsorbents, nitrogen and methanol. The parent material Fr1428 was a pure silica 25 microm sample. The Fr474 sample was the same one with bonded electroneutral diol groups on its outer surface. Fr1386 was the parent material with bonded electroneutral diol groups on its outer surface and sulfonic groups on its inner surface, and the MM1164 sample was the original sample with external electroneutral diol groups and internal n-octadecyl groups. The properties examined were the specific surface area S(p) and the specific pore volume V(p), the pore connectivity c, the pore anisotropy b, the tortuosity tau, and the lacunarity lambda of the pore network as well as the percentage microporosity. These properties provide a complete characterization of complexity of the porous network. The surface areas of the solids were estimated via the traditional BET plots (S(BET)) and the I-point method (S(I)). The two sets of values S(BET) and S(I) were practically identical and they decrease as the size of the functional group increases. The values of percentage microporosity were also determined by the same I-point method using the variation of the C parameter of the BET equation. The total pore volume V(p) was found to be higher in the case of methanol adsorption, compared to nitrogen, which might be related to increase condensation. The networks of the pores were simulated using a dual site bond model (DSBM) and Monte Carlo (MC) techniques for achieving their proper arrangement into the solids. From the resulting simulating networks, the pore connectivity distributions (PCD) and their mean values c(mean) were estimated and favorably compared to the values of connectivity c(Seaton) determined according to the method of Seaton. Both values decrease with the size of the functional groups and are weakly affected by the adsorbent employed. From the simulation pore network, the mean values of tortuosity tau(mean) were also estimated and found to be lower when N2 was used as adsorbate compared to MeOH. The values of lacunarity lambda, estimated according to the method by Allain and Cloitre using the moving box technique in the DSBM/MC simulation matrix of the pore network, indicate that the distribution of the poreless mass into the matrix increases with the size of the functional group. Finally, the internal relationships observed between the pore anisotropy b and the percentage microporosity as well as between the tortuosity tau and the pore connectivity c are discussed.
在这项工作中，我们使用两种不同的探针吸附剂氮气和甲醇的吸附等温线，比较了四种具有不同随机孔隙率的二氧化硅（代号为Fr1428、Fr474、Fr1386和MM1164）中孔隙网络的表面和形态计量学性质。母体材料Fr1428是一个25微米的纯二氧化硅样品。Fr474样品是其外表面带有键合电中性二醇基团的相同样品。Fr1386是外表面带有键合电中性二醇基团且内表面带有磺酸基团的母体材料，而MM1164样品是带有外部电中性二醇基团和内部正十八烷基的原始样品。所研究的性质包括比表面积S(p)、比孔容V(p)、孔隙连通性c、孔隙各向异性b、曲折度tau、孔隙网络的空隙率lambda以及微孔率百分比。这些性质提供了对多孔网络复杂性的完整表征。通过传统的BET图（S(BET)）和I点法（S(I)）估算了固体的表面积。S(BET)和S(I)这两组值实际上是相同的，并且它们随着官能团尺寸的增加而减小。微孔率百分比的值也通过使用BET方程的C参数变化的相同I点法来确定。发现与氮气相比，甲醇吸附情况下的总孔容V(p)更高，这可能与凝聚增加有关。使用双位点键模型（DSBM）和蒙特卡罗（MC）技术对孔隙网络进行模拟，以使其在固体中正确排列。从得到的模拟网络中，估算了孔隙连通性分布（PCD）及其平均值c(mean)，并将其与根据Seaton方法确定的连通性c(Seaton)值进行了有利比较。这两个值都随着官能团尺寸的增加而减小，并且受所用吸附剂的影响较小。从模拟孔隙网络中，还估算了曲折度tau(mean)的平均值，发现与甲醇相比，当使用氮气作为吸附质时其值更低。根据Allain和Cloitre的方法，使用孔隙网络的DSBM/MC模拟矩阵中的移动框技术估算的空隙率lambda值表明，无孔物质在矩阵中的分布随着官能团尺寸的增加而增加。最后，讨论了孔隙各向异性b与微孔率百分比之间以及曲折度tau与孔隙连通性c之间观察到的内在关系。
