Relationship between two characteristic diffractions and the status of cationic lanthanum species in zeolite LaNaY

By employing ex situ and in situ powder X-ray diffraction (XRD) studies, the evolution of two characteristic diffractions at 11.9° and 12.4° (2θ) with the real-time migration of cationic lanthanum species in hydrated, dehydrated, and rehydrated lanthanum-exchanged zeolite NaY (LaNaY) have been discussed thoroughly. We found that the [La(H2O) m ]3+ ions in the supercages can strengthen the (222) diffraction and reduce the (311) diffraction dramatically, and such effects disappear when [La(H2O) m ]3+ ions migrate into the sodalite cages and the hexagonal prisms. The relationship obtained shows the capability to monitor the content/location of lanthanum species in LaNaY sample by monitoring the diffractions between 11.6° and 12.8° (2θ) in its XRD pattern, and may be useful in the routine characterization of LaNaY samples in petrochemical industry, avoiding long time collection and the structure refinement of XRD patterns. Moreover, carefully designed in situ XRD characterization proves that H2O molecules play an important role in the reversible migration of cationic lanthanum species in zeolite Y. 27Al MAS NMR was also performed for validation.