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 aresearch hotspot in the petrochemical industry. Herein, nickel was usedto modify IM-5 zeolite to improve the performance in catalyticcracking. Properties of the Ni/IM-5 zeolites with different nickelloadings were characterized. It was demonstrated that nickel specieswere mainly located on the external surface of impregnated IM-5zeolite, only a few Ni2+ions were distributed in the ion exchange site ascompensation cations. Pyridine infrared results indicated that theintroduction of nickel could modulate the acidity of IM-5 zeolite andincrease the amount of Lewis acid sites. Compared with IM-5, Ni/IM-5exhibited higher olefin selectivity, especially ethylene, inn-hexanecracking reactions. It was considered that nickel could providedehydrogenation active sites and promote the formation of lightolefins. Thus, the selectivity of light olefins can be improved by controlling the amount and distribution of nickel in IM-5 zeolite