Study on lanthanum cation location in LaY zeolite

LaY samples were prepared by double exchange double calcinations (DEDC) method and liquid-solid phase exchange (LSPE) method. The position, occupation and coordination of La³⁺ outside the framework of Y zeolite were determined by polycrystalline XRD with the Rietveld method. La³⁺ situate at SI' sites and coordinate with framework oxygen (O3). As a result, they made the framework of Y zeolite more stable and the hydrothermal stability improved. In samples prepared by LSPE method, the interaction between La³⁺ and O3 was stronger because the bond distance from La³⁺ to O3 was shorter than that in samples prepared by DEDC method. In samples prepared by LSPE method, La cation existed in the form of[La(OH)₂]⁺ because each La³⁺ coordinated with two hydroxyl besides three O3. There were a small amount of Na⁺ located at SI sites inside hexagonal prism in samples prepared by both methods. In samples prepared by DEDC method, there were a few Al³⁺ locate at SII' sites due to slight dealumination during preparation process.