In situ and ex situ XANES study of nanodispersed Mo species in zeolites used in fine chemistry catalysis

Mo K-edge XANES experiments on Mo-containing zeolites at low Mo loading (1 and 2 wt% of Mo on H-ZSM-11, H-BETA and H-ZSM-5 catalysts), active in fine chemistry reactions, were performed ex situ as function of sample calcinati on temperature in air (in the range 773-973 K) or in situ at 873 and 973K u nder N-2 flow. The results showed a 4-fold oxygen coordination for the inco rporated Mo species in the activated (dehydrated) state. Combining these re sults with additional data evidences an almost total Mo exchange inside the zeolite channels.