Mechanistic insights of CO2-coke reaction during the regeneration step of the fluid cracking catalyst

The regeneration of a. coked fluid catalytic cracking (FCC) catalyst under O-2/He and CO2/He atmospheres from room temperature up to 1000 degrees C was studied using online mass spectroscopy. The catalyst was also thermally treated at temperatures between 300 degrees C and 500 degrees C in order to promote coke modification. It was verified that the amount of aliphatic carbon decreased for higher temperatures. These treatments have a more significant impact on the coke-CO2 reaction than on the coke-O-2 reaction. The former reaction was the focus of the present investigation and the results were compared to the latter reaction. CO2 preferentially reacts in the beginning of coke burning and a remarkable decrease Of CO2 activity is observed with the calcinated coked catalyst. Regeneration under (CO2)-C-13/He at constant temperatures between 600 degrees C and 940 degrees C revealed a first-order kinetics for the coke-CO2 reaction. The CO2 molecule reacts dissociatively introducing oxygenated functionality into the coke. These species are decomposed at high temperature forming CO and no water is observed during the CO2-coke reaction. (c) 2007 Elsevier B.V. All rights reserved.