Intracrystalline Mesoporosity over Y Zeolites: PASCA Evaluation of the Secondary Cracking Inhibition in the Catalytic Cracking of Hydrocarbons

Two FCC catalyst prototypes were prepared using Y zeolite with different intracrystalline mesoporosity, which were used in the cracking of n -hexadecane (batch fluidized bed reactor, reaction time 4 s, temperatures 500 and 550 °C, catalyst/reactant 2.6). The primary and secondary cracking analysis method (PASCA), based on balances of carbon atoms among cracking products, showed that increasing the mesoporosity in Y zeolite decreases the incidence of secondary cracking as compared to primary cracking, thus increasing the selectivity to intermediate products. This positive effect was the consequence of the improvements in the diffusion transport of primary product molecules which, in diffusing faster out of the pores, have fewer chances to suffer further cracking. The experiments at different temperatures, with both the prototypes and the equilibrium commercial FCC catalysts, confirmed that this method is a simple tool that allows characterizing the cracking performance of FCC catalysts under conditions similar to those in commercial plants.