Berechnung der adsorptionsisothermen mit einer zustandsgleichung

To study the influence of the actual behavior of the liquid phase on the adsorption properties, three mixtures with different actual behaviors were chosen. The first system hexane/decane is almost an ideal mixture. The second mixture of benzene/methanol has an azeotrope point but no liquid/liquid phase equilibrium (LLE). The third system of hexane/methanol has an azeotrope point and miscibility gap. In the calculation of the adsorption isotherms of the liquid/vapor boundary surface in the hexane/decane system both models give qualitatively similar results. However, the density gradient theory predicts a twice as high value for the adsorption. In the inhomogeneous system hexane/methanol there were characteristic peaks in the adsorption isotherms as a function of the temperature. These related to the concentrations of both coexisting liquid phases and could be traced back to the dissociation equilibrium. For the effectiveness of many industrial processes adsorption plays a decisive role. In the case of homogeneous, almost ideal liquid mixtures the adsorption characteristic of liquid mixtures can be predicted in the liquid/vapor boundary surface with the aid of thermodynamic models and experimentally determined surface tensions. To predict the boundary surface properties expressions from density function theory are suitable. There are still unsolved numerical problems with azeotrope behavior. Numerically simple to handle is the calculation of the Gibbs adsorption isotherm that resides on the assumption of the Gibbs interface. For the description of the real fluid systems the PC-SAFT (Perturbed Chain Statistical Association Fluid Theory) equation of state was used.