Effect of cation location on the hydrothermal stability of rare earth-exchanged Y zeolites

NaY zeolites ion-exchanged with rare earth (RE) cations (La3 +, Ce3 +, Pr3 +, Nd3 +) were prepared by a double-exchange double-calcination method. The position, occupation and coordination of the zeolite extra-framework RE cations were identified by powder X-ray diffraction with the Rietveld refinement. The results indicate that Ce species were insusceptible to migration into the sodalite cages compared with others under the same circumstances, which may be attributed to the facile formation of CeO2(IV) based on Ce(OH)2 + and oxygen as well as the retarded migration of tetravalent cerium. Furthermore, the stability and activity of REY zeolites increased with decreasing ionic radii of RE elements.

► La3 +, Ce3 +, Pr3 + and Nd3 + ion locations in Y zeolite were determined by powder XRD.
► Some cerium(III) ions to the tetravalent state seemed to retard cerium migration.
► Y zeolite containing smaller RE ionic radii showed higher stability and activity.