Morphological characterization and transport properties of physically reconstructed chromatographic beds

定量的形态-运输关系在开发更高效的功能材料的挑战中发挥着关键作用。要有针对性地优化效率，需要了解多孔固体的制备、形态和传质之间的关系。本项目的重点是物理重建的吸附剂(固定床)的形态和传输特性的表征，这代表了基于二氧化硅的小颗粒(&lt；3微米)、硅基整体和有机聚合物整体的液相色谱的最新发展和问题(挑战)。三维重建是基于实验的颗粒固定床和整体固定床，这些固定床是关于颗粒床的填充过程和整体的合成方案而常规制备的。这一方面很重要，因为它为本项目所遵循的方法和所获得的结果提供了透明度、原创性和创造性。在重建的孔隙空间中直接模拟流体流动和质量传输，可以基于材料内在的形态异质性和由此导致的流动不均匀-从微观孔隙尺度到宏观床层尺度-来描述时空动力学。利用从孔隙空间几何和拓扑分析中提取的参数，实现了形态非均质性的量化。我们分析了孔隙的形状、大小分布和相互连接，其中流体流动和平流输送为主，以及空间域，其中扩散输送和吸附占优势，例如在颗粒(或整体骨架)内的停滞区。该项目的目标是通过对无序孔隙空间的几何和拓扑分析，结合流动和质量传输的详细孔隙尺度模拟，确定有效扩散传输的形态描述符，特别是在色谱上更相关的流体动力学分散。从扩散/吸附限制传质的空间域到流场占主导地位的区域，我们用形态描述符定量地评估了它们的结构非均质性。这在扩散/吸附、流动和质量传输的模拟中进行了类似的处理，并导出了反映这种结构异质性的传输系数。因此，对色谱学实践至关重要的传输性质可以与形态性质相关联，形态性质本身反映了吸附剂的填充过程或合成方案。这种互补的方法使我们能够识别敏感的形态描述符(通过详细的运输模拟得到验证)，这将在未来指导基于物理重建的材料性能从合成到目标应用的系统优化。

Quantitative morphology-transport relationships play a key role in the challenge to develop ever more efficient functional materials. Targeted optimization of efficiency requires knowledge on how preparation, morphology, and mass transport of a porous solid are related. In the focus of this project is the characterization of morphological and transport properties of physically reconstructed adsorbents (fixed beds), which represent the latest developments and problems (challenges) in liquid chromatography with small silica-based particles (< 3 µm), silica-based monoliths, and organic polymer-monoliths. The three-dimensional reconstructions are based on experimental particulate and monolithic fixed beds, which have been conventionally prepared regarding the packing process of the particulate beds and the synthesis protocol of the monoliths. This aspect is important as it provides transparency, originality, and genuity to the methodology followed in this project and the obtained results. Simulations of fluid flow and mass transport directly in the reconstructed pore spaces allow the characterization of spatiotemporal dynamics based on the intrinsic morphological heterogeneity of the materials and resulting flow maldistribution - from the microscopic pore scale up to the macroscopic bed scale. The quantification of morphological heterogeneity is achieved with parameters extracted from the geometrical and topological analysis of the pore spaces. We analyze shape, size distribution, and interconnectivity of the pores, in which fluid flow and advective transport dominate, as well as spatial domains, in which diffusive transport and adsorption prevail, like in stagnant regions inside the particles (or a monolith skeleton). The goal of this project is to identify morphological descriptors for effective diffusive transport and especially the chromatographically far more relevant hydrodynamic dispersion through the geometrical and topological analysis of the disordered pore spaces in combination with the detailed pore scale simulations of flow and mass transport. From spatial domains, in which diffusion/adsorption limit mass transport, to regions, in which the flow field dominates, we quantitatively assess their structural heterogeneity with morphological descriptors. This proceeds analogously in the simulations of diffusion/adsorption, flow, and mass transport and derived transport coefficients, which reflect this structural heterogeneity. Consequently, transport properties central to chromatographic practice can be correlated with morphological properties, which themselves reflect the packing process or synthesis protocol of an adsorbent. This complementary approach allows us to identify sensitive morphological descriptors (validated through the detailed transport simulations), which in the future will direct the systematic optimization of material properties from the synthesis to targeted applications based on physical reconstruction.