Structure stabilization of zeolite Y induced by yttrium and its role in promoting n-docosane conversion

Abstract

Rare earth (RE)-exchanged zeolite Y is the major active component of fluid catalytic cracking (FCC) catalysts. Herein, a series of yttrium (Y3+)-exchanged zeolites Y was prepared by the ion-exchange method, and the location of Y3+ ions in the Y3+-exchange zeolite NaY was determined by fitting synchrotron radiation X-ray powder diffraction (XRPD) pattern combined with the infrared spectra in the hydroxyl stretching region. In analogy to lanthanum (La3+)-exchanged zeolite Y, Y3+ ions were preferentially located inside the sodalite units near the double six-membered rings (D6R's), octahedrally coordinating to three framework oxygens and to three H2O molecules (or OH groups) in close proximity. The substitution of Y3+ ions for counter-ions Na + caused a noticeable shrinkage of the unit cell due mainly to the relatively small ionic radius and high charge density of Y3+ ions. As a consequence, the Y3+-exchanged HY-based FCC catalyst exhibited improved steam stability, and higher selectivity for high-value products (liquefied petroleum gas and C5+gasoline) in n-docosane cracking compared with the La3+-exchanged HY-based catalyst.