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Hindrance Factor Expression for Diffusion in Random Mesoporous Adsorbents Obtained from Pore-Scale Simulations in Physical Reconstructions
Industrial & Engineering Chemistry Research ( IF 3.8 ) Pub Date : 2018-02-16 00:00:00 , DOI: 10.1021/acs.iecr.7b04840
Stefan-Johannes Reich 1 , Artur Svidrytski 1 , Dzmitry Hlushkou 1 , Daniela Stoeckel 1, 2 , Christian Kübel 3 , Alexandra Höltzel 1 , Ulrich Tallarek 1
Affiliation  

Hindered diffusion of solutes is the rate-limiting step in many processes for which random porous media play a central role as providers of adsorbing or reactive interfaces. The key to an optimized layout of these processes is the knowledge of the overall diffusive hindrance factor H(λ) = Deff,H(λ)/Dm, which quantifies the degree to which diffusion through a material (represented by the effective diffusion coefficient Deff,H) is hindered compared with diffusion in the bulk liquid (represented by Dm) in dependence of λ, the ratio of solute size to mean pore size. To arrive at an adequate hindrance factor expression for random mesoporous silica, we use electron tomography to physically reconstruct the mesopore space of three macro-mesoporous silica monoliths. The samples share the same general mesopore shape and topology at varied mean feature size, as established by morphological analysis, and serve as realistic models in pore-scale simulations of hindered diffusion. From a large set of Deff,H(λ) values for 0 ≤ λ ≤ 0.9, we derive a quantitative expression for H(λ) that captures the morphological evolution (in dependence of λ) and allows a prediction of the extent of hindered diffusion from material properties. We propose the expression for structures of similar morphology as the investigated samples, which potentially encompasses all mesoporous silica materials obtained through sol–gel processing.

中文翻译:

从物理重建中的孔尺度模拟获得的随机介孔吸附剂扩散的阻碍因素表达。

溶质的受阻扩散是许多过程中的限速步骤,在这些过程中,随机多孔介质作为吸附或反应性界面的提供者发挥着核心作用。优化这些工艺布局的关键是了解总扩散障碍因子H(λ)= D eff,H(λ)/ D m,它可以量化通过材料的扩散程度(以有效扩散表示)。与散装液体中的扩散(以D m表示)相比,系数D eff,H)受到了阻碍)取决于λ,溶质尺寸与平均孔径的比值。为了对随机的介孔二氧化硅获得足够的阻碍因子表达,我们使用电子断层扫描技术物理重建了三个大介孔二氧化硅整体结构的介孔空间。样品通过形态学分析在不同的平均特征尺寸上具有相同的一般中孔形状和拓扑,并在受阻扩散的孔尺度模拟中用作现实模型。从0≤λ≤0.9的大量D eff,H(λ)值中,我们得出H的定量表达式(λ)捕获形态演化(取决于λ)并允许根据材料特性预测受阻扩散的程度。我们提出了一种与所研究样品具有相似形态的结构的表达,它可能涵盖了所有通过溶胶-凝胶工艺获得的介孔二氧化硅材料。
更新日期:2018-02-17
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