Effect of coke deposition over microporous and hierarchical ZSM-23 zeolite

Abstract

The effects of deactivation by coke deposition after the n-heptane cracking reaction were evaluated on crystallinity, acidity and activation energies for the coke thermal oxidation process in microporous and hierarchical ZSM-23 zeolites. The fresh and coked catalysts were characterized by X-ray diffraction, temperature-programmed desorption of ammonia and thermogravimetric analysis. The Flynn–Wall–Ozawa and Vyazovkin kinetic models were used to determine the activation energy of the catalyst regeneration process, using integral dynamic curves from thermogravimetric analysis data obtained with different heating rates. The generation of micro-/mesoporous structures provided a beneficial effect by inhibiting the loss of crystallinity and preserving a certain degree of acidity after catalyst deactivation. The hierarchical ZSM-23 zeolites showed lower deposited coke amounts and activation energy values for the coke thermal oxidation process, providing greater stability, activity and lower energy level required for regeneration in comparison with the microporous zeolites.