Dealuminated ZSM-5 Zeolite Catalyst for Ethylene Oligomerization to Liquid Fuels

Ethylene oligomerization using ZSM-5 zeolite was investigated to study the role of Bronstedacid sites in the formation of higher hydrocarbons. The oligomerization of olefins, dependent on the acidityof ZSM-5 zeolite, is an important step in the conversion of natural gas to liquid fuels. The framework Si/Alratio reflects the number of potential acid sites and the acid strength of the ZSM-5 catalyst. ZSM-5 withthe mole ratio SiO2/Al2O3 equal to 30 was dealuminated for different periods of time according to theacidic ion-exchange method to produce ZSM-5 with various Si/Al ratios. The FT-IR analysis revealedthat the integrated framework aluminum band, non-framework aluminum band, and silanol groups areasof the ZSM-5 zeolites decreased after being dealuminated. The performance of the dealuminated zeolitewas tested for ethylene oligomerization. The results demonstrated that the dealumination of ZSM-5 ledto higher ethylene conversion, but the gasoline selectivity was reduced compared to the performance of aZSM-5 zeolite. The characterization results revealed the amount of aluminum in the zeolitic framework,the crystallinity of the ZSM-5 zeolite, and the Si/Al ratio affected the formation of Bronsted acid sites.The number of the Bronsted acid sites on the catalyst active sites is important in the olefin conversion toliquid hydrocarbons.