Suitability of using ZSM-5 over other medium pore zeolites for n-hexane aromatization - a density functional study

The aromatization of n-hexane over medium pore zeolites e.g. ZSM-5, ZSM-22 and EU-1, has been studied using density functional theory /DFT). We compar ed the activities of different T sites present in these three zeolites and located the active T sites as T6 (ZSM-5), T4 (ZSM-22) and T8 (EU-1), respec tively, by correlating the geometric parameters such as bond length and bon d angles with electronic properties. The experimental Bronsted acidity orde r has been compared with our calculated deprotonation energy to validate ou r model. Now, to choose the best zeolite among the three zeolites studied i n terms of activity toward aromatization, we have performed DFT calculation s on the organic molecules (both reactant and major products), zeolite clus ter and zeolite organic molecule complex. The result matches the experiment al observation by justifying the suitability of ZSM-5 in aromatization reac tion in comparison to other medium pore zeolites. (C) 1999 Elsevier Science B.V. All rights reserved.