Surface species formed during propane aromatization over Zn/MFI catalyst as determined by in situ spectroscopic techniques

The propane conversion was studied by in situ 1H, 13C MAS NMR and IR spectroscopic techniques over Zn/H-MFI catalyst. Propane 2-13C, propane 1-13C, propene 1-13C, propene 2-13C and benzene 13C were used as labelled reactants. The results pointed to the propane activation via dissociative adsorption over zinc oxide sites, as evidenced by zinc propyl surface species observation at the onset of propane conversion. Zinc propyl species convert further into propene, which forms asymmetric π-complex with zinc cations. At the later reaction steps, propene oligomerizes to give charge delocalized carbanionic species stabilized on zinc cations. The role of carbanionic species in consecutive reaction steps is discussed.

Graphical abstractPropane aromatization has been studied in situ over Zn/H-MFI catalyst by 1H, 13C MAS NMR and IR spectroscopic techniques. The following surface species were identified: (i) zinc propyl species; (ii) propene asymmetric π-complex with zinc cations; (iii) charge delocalized carbanionic species stabilized on zinc cations. The role of these species in the reaction pathway is discussed. Figure optionsDownload full-size imageDownload as PowerPoint slide