Meyers J J, Liapis A I
Department of Chemical Engineering and Biochemical Processing Institute, University of Missouri-Rolla 65409-1230, USA.
J Chromatogr A. 1999 Aug 6;852(1):3-23. doi: 10.1016/s0021-9673(99)00443-4.
A cubic lattice network of interconnected pores was constructed to represent the porous structure existing in a monolith (continuous bed) or in a column packed with porous chromatographic particles. Expressions were also constructed and utilized to simulate, through the use of the pore network model, the intraparticle interstitial velocity and pore diffusivity of adsorbate molecules in porous chromatographic particles or in monoliths under retained and unretained conditions. The combined effects of steric hindrance at the entrance to the pores and frictional resistance within the pores, as well as the effects of pore size, pore connectivity, nT, of the porous network, molecular size of adsorbate and ligand (active site), and the fractional saturation of adsorption sites (ligands), have been considered. The results for the adsorption systems studied in this work, indicate that the obstruction effects on the intraparticle interstitial velocity, due to (a) the thickness of the immobilized layer of active sites and (b) the thickness of the adsorbed layer, are small and appear to be insignificant when they are compared with the very significant effect that the value of the pore connectivity, nT, has on the magnitude of the intraparticle interstitial velocity. The effective pore diffusion coefficient of the adsorbate molecules was found to decline with increasing molecular size of ligand, with increasing fractional saturation of the active sites or with diminishing pore size, and with decreasing pore connectivity, nT. The results also show that the magnitude of the interstitial fluid velocity is many times larger than the diffusion velocity of the adsorbate molecules within the porous adsorbent particles. Furthermore, the results clearly show that the intraparticle interstitial velocity and the pore diffusivity of the adsorbate increase significantly as the value of the pore connectivity, nT, of the porous medium increases. The results of this work indicate that the pore network model and the expressions presented in this work, could allow one, for a given porous adsorbent, adsorbate, ligand (active site), and interstitial column fluid velocity, to determine in an a priori manner the values of the intraparticle interstitial velocity and pore diffusivity within the monolith or within the porous adsorbent particles as the fractional saturation of the active sites changes. The values of these transport parameters could then be employed in the macroscopic models that could predict the dynamic behavior, scale-up, and design of chromatographic systems. The theoretical results could also have important implications in the selection of a ligand as well as in the selection and construction of an affinity porous matrix.
构建了一个相互连接的孔隙立方晶格网络，以代表整体柱（连续床）或填充有多孔色谱颗粒的柱中存在的多孔结构。还构建并利用了一些表达式，通过孔隙网络模型来模拟在保留和未保留条件下，吸附质分子在多孔色谱颗粒或整体柱中的颗粒内间隙流速和孔隙扩散率。考虑了孔隙入口处的空间位阻和孔隙内的摩擦阻力的综合影响，以及多孔网络的孔径、孔隙连通性nT、吸附质和配体（活性位点）的分子大小以及吸附位点（配体）的分数饱和度的影响。本工作中研究的吸附系统的结果表明，由于（a）活性位点固定层的厚度和（b）吸附层的厚度，对颗粒内间隙流速的阻碍作用较小，与孔隙连通性nT的值对颗粒内间隙流速大小的非常显著的影响相比，这些阻碍作用似乎微不足道。发现吸附质分子的有效孔隙扩散系数随着配体分子大小的增加、活性位点分数饱和度的增加、孔径的减小以及孔隙连通性nT的降低而下降。结果还表明，间隙流体速度的大小比吸附质分子在多孔吸附剂颗粒内的扩散速度大许多倍。此外，结果清楚地表明，随着多孔介质的孔隙连通性nT的值增加，吸附质的颗粒内间隙流速和孔隙扩散率显著增加。本工作的结果表明，对于给定的多孔吸附剂、吸附质、配体（活性位点）和柱内间隙流体速度，本文提出的孔隙网络模型和表达式可以让人们预先确定随着活性位点分数饱和度的变化，整体柱或多孔吸附剂颗粒内的颗粒内间隙流速和孔隙扩散率的值。然后可以将这些传输参数的值用于宏观模型，以预测色谱系统的动态行为、放大和设计。理论结果在配体的选择以及亲和多孔基质的选择和构建方面也可能具有重要意义。
