Mechanism of tetralin conversion on zeolites for the production of benzene derivatives

Abstract

Ring-opening of tetralin, which is produced by partial dehydrogenation of naphthalene, was catalyzed by various zeolites. Influences of acidity and textural properties of the zeolites on the activity and selectivity were studied in the reactions of not only tetralin but also butylbenzene and indane as the intermediate models in tetralin conversion. The *BEA zeolite exhibited higher conversion and selectivity to benzene and its derivatives (butylbenzene, toluene, xylenes and ethylbenzene) than the other framework type zeolites. The simultaneous cracking of butylbenzene principally produced benzene. The reaction rate in the ring-opening of tetralin was considerably high on strong Brønsted acid sites in the 12-ring of the *BEA zeolite. The amount of Brønsted acid sites on the *BEA zeolite increased the tetralin conversion but did not affect the selectivity to the products. In tetralin conversion, MOR and FAU zeolites formed more methylindane and naphthalene as by-products, respectively. Methylindane was produced on weak Brønsted acid sites through ring-contraction of tetralin, and naphthalene was formed on Lewis acid sites through dehydrogenation. The influences of the reaction conditions on the catalytic activity in tetralin conversion were also investigated. The contact time increased the conversion, but hardly affected the selectivities to the products. The total pressure also improved the catalytic activity. The pressurized hydrogen decreased the selectivity for methylindane, while it increased for benzene and its derivatives. At 573 K, the selectivities to benzene and its derivatives were high, but the reaction temperature increased the selectivity to the by-products.