Effect of Transition Metal Nickel on the Selectivity of Light Olefins in n-Hexane Cracking of Ni/IM-5 Zeolite

The production of light olefins by catalytic cracking is a research hotspot in the petrochemical industry. Herein, nickel was used to modify IM-5 zeolite to improve the performance in catalytic cracking. Properties of the Ni/IM-5 zeolites with different nickel loadings were characterized. It was demonstrated that nickel species were mainly located on the external surface of impregnated IM-5 zeolite, only a few Ni2+ ions were distributed in the ion exchange site as compensation cations. Pyridine infrared results indicated that the introduction of nickel could modulate the acidity of IM-5 zeolite and increase the amount of Lewis acid sites. Compared with IM-5, Ni/IM-5 exhibited higher olefin selectivity, especially ethylene, in n-hexane cracking reactions. It was considered that nickel could provide dehydrogenation active sites and promote the formation of light olefins. Thus, the selectivity of light olefins can be improved by controlling the amount and distribution of nickel in IM-5 zeolite.