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正变得越来越重要。准确了解相应的吸附平衡对于有效地设计这样的分离过程是非常重要的。这项建议申请拨款，以在色谱柱内可压缩超临界溶液吸附平衡的实验测定的基础上，进一步发展与密度相关的吸附热力学模型。在动态测量这种流体的吸附时，沿这种柱的物理必要的压降是主要的误差来源。到目前为止，还缺乏理论上合理的模型来描述这些柱子中的吸附。在本项目的实验部分，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中的大压降下进行。通过使用第二个较短但在其他方面相同的色谱柱，超临界流体的吸附将在密度可假定为恒定的区段内测量。随后，将对热力学建模的不同可能性进行评估，并在必要时进行扩展。目标是通过使用较长的色谱柱进行大压降的测量，尽可能准确地计算出各段中的吸附。对于建模，将使用诸如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之外，所需的纯化合物和混合化合物数据的数量是衡量模型性能的标准。基于二元溶液的吸附，将实验和计算推广到三元溶液(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的吸附剂上的吸附将作为参考数据进行测量。可选地，该模型也可应用于液体吸附，以检验非挥发固体与吸附剂之间的相互作用参数对超临界吸附模型的可转换性。

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.