Carbon-Templated Mesopores in HZSM-5 Zeolites: Effect on Cyclohexane Cracking

Intracrystalline mesoporosity in HZSM-5 zeolites was generated using carbon nanoparticles as template. The activity of the resulting zeolites was evaluated for the ring opening and cracking of cyclohexane. The zeolites with mesopores showed smaller particle sizes and a decrease of the amount of medium and strong acid sites, which involved a decrease of Bronsted nature. Despite their lower acidity, the mesoporous zeolites exhibited higher activity. The mesoporous zeolite with the lowest acidity also showed the lowest activity, evidencing that generation of mesoporosity must be carefully tuned in order to preserve the intrinsic zeolitic properties. Increase of the mesoporosity led to increased selectivity towards more valuable light olefins, consequently decreasing the selectivity towards C-3 and C-4 saturated hydrocarbons. Smaller particle sizes and mesopores improved the products diffusion, decreasing the contact time and the oligomerization and bimolecular hydrogen transfer reactions, which were also disfavored by the decrease of the acid sites concentration. [GRAPHICS] .