Benzene reduction in gasoline by alkylation with olefins: Comparison of Beta and MCM-22 catalysts

Abstract

The study compares the performance of Beta and MCM-22 zeolites as catalysts for propylene alkylation of benzene present in an enriched sample of reformate heart cut (20 wt% benzene). The experiments were carried out in a batch system with a 2/1 mole ratio of benzene/propylene at 220 °C for 1 h. An MCM-22 zeolite that contained Brønsted/Lewis acid sites in a 2–3/1 ratio proved to be much more resistant to deactivation during these real feed benzene alkylation experiments when compared with the Beta catalyst (Brønsted/Lewis acid site ratio of 0.1–0.3/1). MCM-22 with a 45 wt% benzene conversion presented higher i-propylbenzene selectivity than Beta (38 wt% benzene conversion) by reducing the formation of by-products. The outstanding behavior of MCM-22 may be explained by its particular Brønsted to Lewis acid ratio, which could help in the carbonium-ion formation and in the activation of the benzene ring toward electrophilic attack, and to its open crystalline framework that facilitates diffusion of reactants, products and coke precursors. Additional studies regarding experimental conditions for the preparation of MCM-22 and alkylation procedures are required for optimization.