Nature and location of cerium in Ce-loaded Y zeolites as revealed by HRTEM and spectroscopic techniques

Different methods were used to introduce cerium in a HUSY zeolite. The samples obtained from ion-exchange, precipitation and wetness impregnation procedures were characterized both before and after hydrothermal deactivation in order to determine and compare the nature of the cerium species and their location in the catalyst. A variety of techniques were used: XRD, HRTEM, XPS, infrared and Raman spectroscopy and catalytic test of dehydration of 2-propanol. The presence of amorphous phases of extra framework aluminium species (EFAL) depends on the preparation method as was evidenced by TEM. The presence of CeO2 and exchanged cerium was determined in catalysts prepared by precipitation and impregnation methods. The quantification of both types of cerium species was accomplished by Rietveld refinement. For the catalyst prepared by impregnation, it is suggested that cerium species interact with EFAL species. This interaction determines the cerium dispersion.