Theoretical study of the effect of trickle phase conditions on competitive adsorption in packed bed adsorption columns

In several industrial catalytic processes the operating conditions cause the feed to be in trickle phase conditions. For example in the hydroconversion process the linear alkanes are converted in trickle phase reactor and it is well known that the presence of the vapor-liquid equilibrium has a determining effect on selectivity through changing adsorption behavior. In this paper a model is developed that describes adsorption in trickle phase conditions in an adsorption breakthrough experiment. Due to adsorption the composition in the column during breakthrough changes and local shifts in aggregation state can occur. The model allows to simulate both single and mixed phase conditions and transitions between these states. The composition of the vapor and liquid phase in trickle phase conditions is calculated using the Peng Robinson equation of state (PREOS). The model shows how vapor-liquid equilibrium influences adsorption selectivity. Two cases are identified, adsorption of linear alkanes with nonspecific adsorption interaction and adsorption of polar and apolar compounds on an apolar adsorbent. Depending on conditions vapor and liquid fronts are observed and the effects of temperature and pressure are studied for both cases and different behavior is observed. From the simulation results it is concluded that accounting for the presence of vapor-liquid equilibrium in trickle phase adsorption columns is important since it has an effect on selectivity and the shape of breakthrough curves.