The USY zeolite in fluid cracking catalyst is commonly stabilized by ion-exchange with rare-earth (RE) cations. The RE-exchange provides hydrothermal stability by improving surface area retention, as well as inhibiting dealumination of the zeolite, resulting in greater preservation of acid sites. Though La and Ce are commonly used in FCC catalysts, we have observed that the stability of REUSY catalysts improves as the ionic radius of the RE cation decreases. In this paper, we compare the activity and selectivity of REUSY catalysts, stabilized with light (La) and heavy (Ho, Er, and Yb) rare-earth cations�the latter having a smaller ionic radius, due to the well-known phenomenon of lanthanide contraction.The experimental data (Table 1) shows that when lanthanide elements having a smaller ionic radius are used to make the REUSY catalyst, a significant improvement in catalytic activity is achieved. The data also shows that yttrium is even more effective than the heavier lanthanides in stabilizing Y-zeolite. Under a variety of deactivation conditions, yttrium stabilized USY catalysts show higher cracking activity and higher gasoline selectivity than similar catalysts formulated with lanthanum. The results may be explained by the greater hydrocarbon adsorption capacity of the yttrium-stabilized catalysts.Table 1 Activity and yields of various rare-earths containing FCC catalysts. RE input at constant moles.

Effect of ionic radius of rare earth on USY zeolite in fluid catalytic cracking

247th National Meeting (2014)

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