The alkylation of naphthalene over three-dimensional large pore zeolites: The influence of zeolite structure and alkylating agent on the selectivity for dialkylnaphthalenes

In order to elucidate how zeolite structure and alkylating agent play roles in the shape-selective catalysis, the alkylation, i.e., isopropylation, sec-butylation, and tert-butylation, of naphthalene (NP) was examined over three-dimensional twelve-membered (12-MR) zeolites, Y (FAU), Beta (BEA), and CIT-1 (CON), and compared to that of H-mordenite (MOR). The β,β-selectivities (for β,β-dialkylnapthalene (β,β-DAN)) and the 2,6-selctivities (for 2,6-dialkylnaphthalene (2,6-DAN)) among DAN isomers varied with the types of zeolites and alkylating agents. FAU, BEA, and CON gave only low selectivities for 2,6-diisopropylnaphthalene (2,6-DIPN) in the isopropylation, and predominant isomers were bulky and thermodynamically unstable α,β-DIPN (1,3-, 1,6-, and 1,7-DIPN) and α,α-DIPN (1,4- and 1,5-DIPN) at lower temperatures, and the formation of the less bulky and thermodynamically stable β,β-DIPN (2,6- and 2,7-DIPN) increased with increasing the temperature: they have quite different features from the shape-selective catalysis over MOR. These results suggest that FAU, BEA, and CON are not shape-selective in the isopropylation, and that the isopropylation is principally controlled kinetically at lower temperatures, and thermodynamically at higher temperatures.