A computer simulation study on acylation reaction of aromatic hydrocarbonsover acidic zeolites

In the case of acylation reaction of aromatic hydrocarbons it is observed t hat acylation of toluene and naphthalene in the presence of acidic zeolites such as H-ZSM-5, H-ZSM-12, H-Beta, H-Mordenite, and H-Y results in differe nt products with variable selectivities. It is observed experimentally that benzoylation of toluene and naphthalene over zeolite H-Beta follows the se lectivity order: 4-methylbenzophenone > 2-methylbenzophenone > 3-methylbenz ophenone and 2-benzoylnaphthalene > 1-benzoylnaphthalene, respectively. Zeo lite H-Beta shows the best selectivity among all other acidic zeolites. To explain this selectivity order a computer simulation study has been perform ed. Molecular mechanics were used to calculate the individual strain, dimen sions of reactant, and product molecules; the dimensions of zeolite cages w ere compared. The results show that zeolite Beta is the best zeolite in ter ms of fitting of the reactant and product molecules. DFT was applied to stu dy the electronic property and interaction energy of reactant and product m olecules with acidic zeolite framework to rationalize the mechanism of acyl ation reaction over acidic zeolites. Molecular electrostatic potential maps were also plotted from DFT to rationalize the polarization of the reactant s in the reaction process. The results were compared with experimental obse rvation which justifies the role of acidic zeolites, in this particular rea ction. (C) 1999 Academic Press.