Abstract
The isopropylation of naphthalene (NP) over USY zeolite (FAU06, SiO2/Al2O3 = 6) gave all eight possible diisopropylnaphthalene (DIPN) isomers: beta,beta- (2,6- and 2,7-), alpha,beta- (1,3-, 1,6-, and 1,7-), and alpha,alpha- (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 beta,beta-DIPN were observed at the early stages at 200, 250, and 300 degrees C although the selectivities decreased with the increasing periods, accompanying the increase in alpha,alpha- and alpha,beta-DIPN. The enhancement occurs under new types of thermodynamic controls through thermodynamically preferred transition states to beta,beta-DIPN. Triisopropylnaphthalene (TriIPN) isomers are also formed in the isopropylation. Unstable alpha,alpha,beta-TriIPN (1,4,6- and 1,3,5-) is predominantly formed at lower temperatures; however, decreased with the increase of stable alpha,beta,beta-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 degrees 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.