N-Propylbenzene Disproportionation: An Efficient Tool for Assessing the Framework Topology of Large-Pore Zeolites

Abstract

The mechanisms of n-propylbenzene (nPB) disproportionation over various large-pore (LaNa-Y, H-Y, H-mordenite, and H-beta) and medium-pore (H-NU-87, H-TNU-9, and H-ZSM-5) zeolites were investigated. The GC–MS results from the used zeolite catalysts demonstrate that monopropylated 1,1-diphenylpropane and dipropylated 1,1-diphenylpropane derivatives are serving as the main reaction intermediates of bimolecular nPB disproportionation, whereas 1-phenyl-2-propylphenylpropane, 1-propylphenyl-2-phenylpropane, and 1-propylphenyl-2-propylphenylpropane species are the intermediates of some particular side reactions. It was found that the intrazeolitic buildup of these five different groups of diphenylpropane-based species is strongly influenced by the size and shape of zeolite void spaces, as was also corroborated by DFT calculation results. This allows nPB disproportionation to be quite useful for estimating the framework topology of zeolites with unknown structures, especially those of large-pore materials.