Zeolite rare earth

It is unexpected that the catalytic activity and the proton acidity do not depend on the lanthanum content. This result cannot be related to the schemes of hydrolysis of the zeolitic rare earth cations reviewed in Ref. 13. On the other hand, acidity measurements in solution (15) have shown that in the lanthanum zeolites studied in this work the La3+ ions have replaced the NH4+ ions and have not formed a lanthanum compound (13). Finally, the variations in the sodium content of these lanthanum zeolites do not seem to be the dominant factor in contrast to the alkaline earth zeolites (26). 

In conclusion, we have shown here that rare earths play an important role in improving the stability of Y zeolite in FCC catalysts. Moreover, by an adequate control of the zeolite rare-earth content, it is possible to control the activity and selectivity of the catalyst by controlling the unit cell size or framework aluminium content of the equilibrated zeolite. 

The alumina content, the amount of rare-earth, and the type and amount of zeolite affect catalyst tolerance to vanadium poisoning. 

Until the late 1970s, the NaY zeolite was mostly ion exchanged with rare earth components. Rare earth components, such as lanthanum and... 

Zeolites with lower UCS are initially less active than the conventional rare earth exchanged zeolites (Figure 3-5). However, the lower UCS zeolites tend to retain a greater fraction of their activity under severe thermal and hydrothermal treatments, hence the name ultrastable Y. 

A freshly manufactured zeolite has a relatively high UCS in the range of 24.50°A to 24.75°A. The thermal and hydrothermal environment of the regenerator extracts alumina from the zeolite structure and, therefore, reduces its UCS. The final UCS level depends on the rare earth and sodium level of the zeolite. The lower the sodium and rare earth content of the fresh zeolite, the lower UCS of the equilibrium catalyst (E-cat). 

Rare Earth Level. Rare earth (RE) elements serve as a bridge to stabilize aluminum atoms in the zeolite structure. They prevent the... 

A fully rare-earth-exchanged zeolite equilibrates at a high UCS. whereas a non-rare-earth zeolite equilibrates at a very low UCS in the range of 24.25 [3]. All intermediate levels of rare-earth-exchanged zeolite can be produced. The rare earth increases zeolite activity and... 

Figure 3-5. Comparison of activity retention between rare-earth-exchanged zeolites versus USY zeolites. (Source Grace Davison Octane Handbook.)...

UCS, rare earth, and sodium are just three of the parameters that are readily available to characterize the zeolite properties. They provide valuable information about catalyst behavior in the cat cracker. If required, additional tests can be conducted to examine other zeolite properties. 

A typical NaY zeolite contains approximately 13 wt% Na20. To enhance activity and thermal and hydrothermal stability of NaY, the sodium level must be reduced. This is normally done by the ion exchanging of NaY with a medium containing rare earth cations and/ or hydrogen ions. Ammonium sulfate solutions are frequently employed as a source for hydrogen ions. 

At this state of the catalyst synthesis there are two approaches for further treamient of NaY. Depending on the particular catalyst and the catalyst supplier, further treatment (rare earth exchanged) of NaY can be accomplished either before or after its incorporation into the matrix. Post-treatment of the NaY zeolite is simpler, but may reduce ion exchange efficiency. 

A rare-earth-exchanged zeolite increases hydrogen transfer reactions. In simple terms, rare earth forms bridges between two to three acid sites in the catalyst framework. In doing so, the rare earth protects... 

Rare Earth. Increasing the amount of rare earth oxide (REO) on the zeolite decreases the octane (Figure 6-5). 

Rare Earth is a generic name used for the 14 metallic elements of the lanthanide series used in the manufacturing of FCC catalyst to improve stability, activity, and gasoline selectivity of the zeolite. 

Di or trivalent cations are able to induce the dissociation of coordinated water molecules to produce acidic species such as MOH+ (or MOH2+ for trivalent metal cations) and H+. Several infrared studies concerning rare-earth or alkali-earth metal cation exchanged Y zeolites have demonstrated the existence of such species (MOH+ or MOH2+) [3, 4, 5, 6]. However, the literature is relatively poor concerning the IR characterization of these acidic sites for LTA zeolites. The aim of the present work is to characterize 5A zeolite acidity by different techniques and adsorption tests carried on 5A zeolite samples with different ion exchange. 

The ammonia is released and the protons remain in the zeolite, which then can be used as acidic catalysts. Applying this method, all extra-framework cations can be replaced by protons. Protonated zeolites with a low Si/Al ratio are not very stable. Their framework structure decomposes even upon moderate thermal treatment [8-10], A framework stabilization of Zeolite X or Y can be achieved by introducing rare earth (RE) cations in the Sodalite cages of these zeolites. Acidic sites are obtained by exchanging the zeolites with RE cations and subsequent heat treatment. During the heating, protons are formed due to the autoprotolysis of water molecules in the presence of the RE cations as follows ... 

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