Propene transformation on Cu-modified ZSM-5 zeolite: Aromatization and oxidation

Propene transformation on copper-modified ZSM-5 zeolite has been studied by 13C MAS NMR and FTIR spectroscopy. Two major reaction pathways are identified, aromatization to the simple aromatic hydrocarbons (benzene, toluene) and oxidation to acrolein. Copper-allyl species is inferred to be the key intermediate in both processes. π-Complex of propene with copper sites is the primary intermediate, preceding the formation of copper-allyl species. The role of different active sites is established. Cu2+–O2– Lewis acid-base pairs are responsible for the allylic species formation, whereas [Cu3(μ-O)3]2+ oxo-clusters provide the oxidation of copper-allyls. The results obtained are of importance for developing zeolite-based catalysts for propene aromatization to the simple aromatic compounds and partial oxidation to acrolein.