Ammoxidation of C2 hydrocarbons over Mo zeolite catalysts prepared by solid state ion exchange: Nature of molybdenum species
Abstract Successful introduction of molybdenum (from MoCl 3 into zeolites of different topologies was carried out using solid state ion exchange. MOR like support extended the formation of Mo oxides due to its particular aperture/channel shapes. However, BEA and MFI (ZSM 5) zeolites structures loaded small aggregates of Mo oxide. Exchanging MoCl 3 with NH 4 BEA, H ZSM 5 (Si/Al 15) and NH 4 ZSM 5 (Si/Al 26) led to the consumption of Bronsted acid sites and silanol groups, while the lack of exchange sites in NH 4 MOR generated Mo OH as revealed by DRIFTS and TPD of NH 3 Polymeric Mo and MoO 3 occupied the bulk of BEA and MOR issued solids. Nevertheless, NH 4 ZSM 5 (Si/Al 26) support triggered the formation of dimeric species. For H ZSM 5 (Si/Al 15) solid, monomeric species migrated throughout the channels of H ZSM 5, which condensed easily to form rather polymeric species. Small oxide crystallites and Mo moieties that weakly interact with NH 4 BEA and NH 4 ZSM 5 (Si/Al 26) were easily reduced under hydrogen, while the negatively charged H ZSM 5 (Si/Al 15) framework inhibited the reducibility.