The isopropylation of naphthalene over USY zeolite with FAU topology. The selectivities of the products

The isopropylation of naphthalene (NP) over USY zeolite (FAU06, SiO₂/Al₂O₃ = 6) gave all eight possible diisopropylnaphthalene (DIPN) isomers: β,β- (2,6- and 2,7-), α,β- (1,3-, 1,6-, and 1,7-), and α,α- (1,4- and 1,5-). The catalyses were operated under kinetic and/or thermodynamic controls depending on the reaction temperatures since the cavities of FAU topology are wide enough to form all DIPN isomers. Enhanced selectivities for β,β-DIPN were observed at the early stages at 200°C, 250°C, and 300°C although the selectivities decreased with the increasing periods, accompanying the increase in α,α- and α,β-DIPN. The enhancement occurred under new types of thermodynamic controls through thermodynamically preferred transition states to β,β-DIPN. Triisopropylnaphthalene (TriIPN) isomers were also formed in the isopropylation. Unstable α,α,β-TriIPN (1,4,6- and 1,3,5-) was predominantly formed at lower temperatures, however, decreased with the increased of stable α,β,β-TriIPN (1,3,6- and 1,3,7-) at higher temperatures. The predominant formation of 1,4,6-TriIPN was also observed in the initial stages in the range of 200°C, 250°C, and 300°C, as reaction period was increased, while the selectivity for the isomer was decreased with concomitant increase in the selectivities for the other isomers. These changes of the selectivities operated under kinetic and/or thermodynamic controls. Large cavities of the zeolite allowed the formation of all TriIPN isomers without steric restriction.