A simplified dynamic mathematical model for a simulated moving-bed adsorption process is presented. The model is adopted to simulate the separation process of p-xylene from the other 8-carbon aromatics by means of the Parex (TM) technology. Operating conditions and the moving-bed structure for a commercial plant were used and the performance of the unit was simulated. The model results are in good agreement with the findings of similar existing studies. Comparison of the results of this simplified model with those obtained by other researches indicates a considerable decrease in central processing unit (CPU) time.