The Isopropylation of Naphthalene over USY Zeolite with FAU Topology. The Selectivities of the Products

Abstract

Abstract 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 are operated under kinetic and/or thermodynamic controls depending on the reaction temperatures because 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, 250, and 300 °C although the selectivities decreased with the increasing periods, accompanying the increase in α,α- and α,β-DIPN. The enhancement occurs under new types of thermodynamic controls through thermodynamically preferred transition states to β,β-DIPN. Triisopropylnaphthalene (TriIPN) isomers are also formed in the isopropylation. Unstable α,α,β-TriIPN (1,4,6- and 1,3,5-) is predominantly formed at lower temperatures; however, decreased with the increase 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, 250 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 allow the formation of all TriIPN isomers without steric restriction.