Exploring the acid catalyzed isomerization of phenanthrene under confinement in mordenite

Abstract

The isomerization reaction of 1,2-dihydrophenanthrene catalyzed by a mordenite zeolite is explored theoretically in the present study. It was found that the electrostatic adducts which resemble ion-pair and π complexes, detected for zeolite catalysts, could enable the reaction to proceed through an energy favorable channel and explain its selectivity. The reaction pathway found for the interaction of 1,2-dihydrophenanthrene with the acid site of a mordenite zeolite proceeds firstly through a hydrogen abstraction, followed by a concerted cyclization pathway with C-C bond β-scission assisted by the reagent interaction with the zeolite catalyst. Then, two sequential migrations take place over the five-ring cycled product leading to unstable carbocation intermediate species which could be hydrogenated by an H2 molecule. The Al site within the MOR zeolite framework, does not activate the H-H bond. The C-C bond scission-cyclization process is detected as the energetic limiting step that could be fostered due to the confinement effect induced by the zeolite porous structure.