Abstract: The catalytic transformation of methylcyclohexane as an accepted probe reaction to evaluate zeolitic acidity (concentration, strength, and accessibility) is employed to study the acidity and the reactivity of three commercial dealuminated Y zeolites (DAY) with different Si/Al ratios and meso/microporosities, accompanied by N2 adsorption/desorption, pyridine-IR, hydroxyl-IR spectroscopy technologies. The global activity (conversion) is largely dependent on the concentration of the acid sites, and the activity of the protonic sites in terms of turnover frequency (TOF) reflects the accessibility of acid sites. The products of aromatics and isomers, and the yield of cracking products increase with the increase of concentration of strong protonic sites in zeolite micropores. Moreover, the decrease of aromatics with the reduction of the concentration of acid sites and the diffusion length within DAY zeolites are observed due to the decrease of the secondary reaction. For the same reason, it results in the increasing of C7 products and alkenes/alkanes ratios in the cracking products. The high i-C4 product selectivity is a unique reflection of the high percentage of very strong acid sites, which is characterized by the hydroxyl-IR band at 3600 cm-1.

Key words: methylcyclohexane catalytic transformation, industrially modified Y zeolite, zeolitic acidity, strong protonic sites, spectroscopic technology