Investigation on the cation location, structure and performances of rare earth-exchanged Y zeolite

Abstract

A series of Y zeolites exchanged with different amount of cerium and lanthanum cations were investigated. Comprehensive routine analysis tools including X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), X-ray diffraction (XRD) and Py-Fourier transform infrared spectroscopy (Py-FTIR) were used to identify the cation location, and the result was verified via XRD Rietveld study. The results revealed that almost all the RE cations in RE-4, most cations in RE-8 to RE-14 and part of cations in RE-16 were located in the sodalite cage. The AlIV/(AlV+AlVI) values revealed by 27Al MAS NMR spectra, the silicon aluminum ratio of the framework (SARF) values deduced from 29Si MAS NMR spectra and XRD, and hydroxyl amount were reasonably in accordance with the location and content of rare earth cations. The hydrothermal stability derived from in situ XRD investigation and catalyst activity provided by micro-activity test manifested that samples RE-8 to RE-14 exhibited better performances than RE-4 and RE-16, among which RE-12 had the best properties. The phenomena were interpreted by the cation location and structural properties.