To separate linear and branched molecules in a liquid state, adsorption on porous materials is a promising separation method. To calculate the adsorption isotherms, a combination of lattice cluster theory and density functional theory was introduced recently, allowing the prediction of branched molecules' adsorption isotherms based on the knowledge of the adsorption isotherms of the pure linear substances. However, these models are not practicable for process simulation and optimization because of their high numerical effort. Therefore, a simpler adsorption model based on the lattice cluster theory was developed to provide the results of the density functional theory approach for process development. In addition to the adsorption isotherm calculations, the model also considers the overall mass balance of the adsorption process. The model was validated for the adsorption of two binary, liquid alkane systems on three different adsorbents. Therefore, adsorption isotherms of these mixtures on activated coal, zeolite, and silica gel were measured. A good agreement of experimental and calculated adsorption isotherms was observed for all systems.