Influence of pressure and density on adsorption equilibria from near and supercritical solutions - experimental determination and thermodynamic modeling

随着颗粒直径达到纳米级，使用超临界流体的吸附过程变得越来越重要。准确了解相应的吸附平衡对于有效地设计这种分离过程是非常重要的。该提案申请拨款，以进一步发展密度依赖吸附的热力学模型，该模型基于色谱柱内可压缩超临界溶液吸附平衡的实验测定。在动态测量此类流体的吸附时，物理上必要的压降是误差的主要来源。到目前为止，缺乏模型来描述吸附在这些柱在理论上合理的方式。在实验部分，研究了二元溶液（CO2 +非挥发性有机固体）的吸附。吸附测量将在分析色谱柱的大压降下进行。通过使用第二个较短但其他方面相同的柱，可以在密度可以假设为恒定的段内测量超临界流体的吸附。随后，热力学建模的不同可能性将进行评估，并在必要时进行扩展。目的是通过使用较长的色谱柱进行大压降的测量，尽可能准确地计算段中的吸附量。在建模方面，将应用诸如Peng-Robinson状态方程、SAFT和Virial状态方程等模型。除了描述依赖于密度的吸附外，所需的纯化合物和混合化合物数据的数量是模型性能的一个标准。在二元溶液吸附的基础上，将实验和计算扩展到三元溶液（CO2 +有机改性剂+非挥发性有机固体）。此外，溶解在正己烷中的非挥发性固体在相同吸附剂上的吸附量作为参考数据进行测量。可选地，该模型还将应用于液体吸附，以测试非挥发性固体和吸附剂之间相互作用参数对超临界吸附模型的可转移性。

Adsorption processes using supercritical fluids are gaining increasing importance, with particle diameters reaching into the nanoscale. Exact knowledge of the corresponding adsorption equilibria is of utter importance to design such separation processes efficiently.This proposal applies for a grant to further develop the thermodynamic modeling of density dependent adsorption based on experimental determination of adsorption equilibria of compressible supercritical solutions within a chromatographic column. The physically necessary pressure drop along such a column is a major source of error within the dynamic measurement of adsorption of such fluids. So far, there is a lack of models to describe adsorption in these columns in a theoretically sound manner. In the experimental part of the project the adsorption of binary solutions (CO2 + non-volatile organic solid) is investigated. Adsorptions measurements will be carried out with a large pressure drop in an analytical chromatographic column. By using a second, shorter but otherwise identical column, the adsorption of the supercritical fluid is to be measured within segments in which the density can be assumed constant. Subsequently, different possibilities of thermodynamic modeling will be evaluated and extended if necessary. The goal is to calculate the adsorption in the segments as exactly as possible from the measurements with large pressure drop using the longer column. For modeling, models such as the Peng-Robinson equation of state, SAFT and the Virial equation of state are to be applied. Next to the description of the density dependent adsorption, the number of pure and mixed compound data needed is a criterion for the performance of the model. Based on the adsorption of binary solutions, the experiments and calculations are extended to ternary solutions (CO2 + organic modifier + non-volatile organic solid). Additionally, the adsorption of non-volatile solids dissolved in n-hexane on the same adsorbents is to be measured as reference data. Optionally, the modeling will also be applied to liquid adsorption to test the transferability of interaction parameters between non-volatile solid and adsorbent to the modeling of the supercritical adsorption.