An MAS NMR study on the Mo-modified phosphoric rare earth (HZRP-1) penta-sil zeolite catalyst

High-resolution solid-state MAS NMR, equipped with a newly designed device for conducting catalytic reactions, was used to characterize in-situ an Mo modified phosphoric rare earth-containing penta-sil zeolite catalyst (denoted as Mo /HZRP-1), which showed good activity for methane dehydro-aromatization in the absence of oxygen. Al-27 MAS NMR spectra revealed the presence of different Al-relating species in the calcined and reacted catalysts. High calcination temperature and high Mo loading enhanced the replacement of framework silicon by phosphorus atoms, resulting in the alteration of the environment of aluminum nuclei in the zeolitic framework and leading consequently to a change of the acidic property of the catalyst. In correlation with reaction results of the relevant catalysts, it was concluded that the presence of tetrahedral framework aluminum, which is associated with the formation of Bronsted acidic sites, is of great significance for methane dehydro-aromatization.