m-Xylene isomerization is one of the current technologies for the mass production of p-xylene. Very recently, we have provided clear experimental evidence that tri- and tetramethylated diphenylmethane (3mDPM and 4mDPM) species are real transition states of this reaction not only over large-pore zeolites but also over some medium�pore ones (Min et al. ACS Catal. 2012, 2, 971).  Here we have performed density functional theory calculations on the strain energies of 3mDPM and 4mDPM derivatives in eight different medium-pore zeolites in order to more precisely investigate the effects of zeolite pore structure on the type of these bicyclic aromatic reaction intermediates. We have also calculated the adsorption energies of p-xylene and o-xylene within the channels of six different medium-pore zeolites.  The strain energies of 3mDPM and 4mDPM species, as well as the adsorption energies of p-xylene and o-xylene, were found to increase with decreasing the available void space in medium-pore zeolites, which is in excellent agreement with the conclusion from our recent experimental work.

Theoretical investigations of <i>m-x</i>ylene isomerization over medium-pore zeolites with different framework topologies

247th National Meeting (2014)

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Theoretical investigations of m-xylene isomerization over medium-pore zeolites with different framework topologies