Experimental determination of Fluidized Catalytic Cracking (FCC) deactivation constant

FCC catalyst is deactivated by coke formation during the process. The rate equations describing FCC process kinetics involve a deactivation term to account for the decrease in the reaction rates due to coke deactivation. Several mathematical functions have been proposed to represent this catalyst decay term. A study was carried out to determine the deactivation constant. VGO cracking activity of steamed catalyst was measured utilizing micro-activity test (MAT), as per the ASTM method. The catalyst was then deactivated by injecting VGO for 10, 20, and 30 sec at 600°C. The kinetic conversion was proportional to C/O as C/O was changed by varying the quantity of catalyst in the reactor. The deactivation constant was 59, 86, and 156/hr at 480°, 600°, and 700°C, respectively. The activation energy for the catalyst deactivation was 6.3 Kcal/mole from the slope of the temperature dependency of the catalyst decay constant based on the Arrhenius law. This agreed well with published data. The use of this experimentally determined value of deactivation constant increased the accuracy of predicted yields of gas, gasoline, and coke.