A model is developed that allows simulation of breakthrough adsorption experiments of n-alkanes dissolved in a short chain alkane solvent. The model is used to verify conclusions made in previous experimental work that studied competitive adsorption behavior of paraffinic mixtures in vapor and liquid phase conditions. In these types of breakthrough experiments, a pressure drop in the adsorption column results in a change in aggregation state and density changes inside the column, leading to a change in adsorption behavior. Simulations demonstrate the effect of column temperature, outlet pressure, and pellet size on competitive adsorption behavior, and the importance of the effect of density on adsorption behavior is also demonstrated.