Analysis of decisive structural parameters of zeolites for alkylation of benzene with ethylene

The effects of the zeolite structure and the Bronsted and Lewis sites on the activity and selectivity in alkylation of benzene with ethylene to ethylbenzene were investigated using three series of zeolites with different structures, Si/Al ratios and contents of Lewis sites. The 12-membered three-dimensional channels of beta zeolite ((star)BEA) provide higher selectivity to ethylbenzene compared to faujasite zeolite (FAU) with cavities in which the di-alkylated and heavier by-products are formed. The activity is controlled by the concentration of Bronsted acidic sites, while Lewis sites do not contribute to the activity or affect the selectivity. The highest activity and selectivity are obtained using Al-rich H-(star)BEA (Si/Al 4.2) with a high density of Bronsted groups in a well-defined channel structure sterically constrained for heavy by-products. It is shown that a three-dimensional channel structure with Bronsted acid sites in a shape selective environment is a key parameter controlling the activity and selectivity.