Hyperpolarized 129xe N0R study on Y zeolites modified by rare earth cations

The pore structure of REHY zeolites and the distribution of rare earth cations in zeolites were characterized by hyperpolarized 129Xe NMR, as well as by XRD, 29Si NMR and N2 adsorption-desorption analysis. The results showed that two signals were observed in the 129Xe NMR of REHY, which could be attributed to two kinds of fast exchange of Xe atoms in the two different types of pores (pores I and II). Pore I was attributed to the supercage of Y zeolites and pore II might be generated from the partial destruction pore caused by molecular sieves dealuminum. The details of Xe adsorption and motion were also studied by variable-temperature (VT) 129Xe NMR experiments. The VT 129Xe NMR experiments suggested that the pore structure of Y zeolites could be improved greatly by the introduction of rare earth cations (RE). However, the RE cations could be found not only in the supercage, but also at the surface of Y zeolites modified by high content of RE, which would block the pore of Y zeolite.