Cumene transformations over mordenite catalysts: a 13C MAS NMR study

Cumene conversion under an excess of benzene is studied over a series of mordenite (MOR) zeolites (Na-MOR, HNa-MOR, H-MOR and dealuminated H-MOR) by in situ 13C and 1H MAS NMR spectroscopy in the temperature range 298–473 K. By tracing the fate of 13C labeled atoms in the benzene molecule, intermolecular transalkylation, disproportionation and isomerization reactions are highlighted. The reactivity of MOR-based catalysts in these reactions is found to increase in the following order: <f>Na-MOR<HNa-MOR<H-MOR<H-DealMOR</f>. Transalkylation and disproportionation require mild conditions (<f>T=298–393</f> K, weak acidity), while isomerization to <f>n</f>-propylbenzene needs more severe conditions (<f>T>473</f> K, strong acid sites). The reaction mechanisms are discussed. [Copyright &y& Elsevier]