Document Type : Regular Article
Chemical Engineering, Shahid Nikbakht faculty of engineering, University of Sistan and Baluchestan, Zahedan, Iran
Although catalyst deactivation rate greatly varies depending on many factors, including the catalyst structure, reactor feed composition, and operating conditions; it is usually inevitable. Since catalyst deactivation modeling has so far been poorly addressed in the literature, in the present study, nine experimental sets of cobalt based Fischer-Tropsch catalysts activity-time data were considered to be modeled using an innovative sigmoidal pattern with amazingly meaningful parameters. Such theoretical models for catalyst life significantly facilitate the control of reactors during petrochemical industrial applications, where a constant reactor product flow rate is necessary. Five types of statistics were used to validate the goodness of the regression model. The results showed that the sigmoid model perfectly predicts the activity of the whole catalyst life for a wide range types of catalyst which is capable of being utilized as an important part of a reaction rate. For process conditions within the range of T=220–230 0C, P=20 bar, and H2/CO ratio=2, the two important constants of the model average 0.6 ± 0.1 and 0.42 ± 0.06 for steady-state activity and total loss of activity, respectively. The proposed model offers a significant advance over the existing macroscopic deactivation models, since different catalyst deactivation trends can be covered.