USY for FCC

USY (Ultra-Stable Y) zeolite is the primary cracking component in modern FCC catalysts. It is the only large-pore zeolite that combines the acidity needed for gas oil cracking with the hydrothermal stability required to survive hundreds of oxidation-reduction cycles in the FCC regenerator at 700-800 °C in steam.

Why USY Is the FCC Standard

USY is produced by dealuminating Y zeolite through steam calcination. This removes framework aluminium, raising the effective Si/Al ratio, contracting the unit cell, and creating secondary mesoporosity. Three properties make USY the FCC cracking standard:

Hydrothermal stability. A non-dealuminated HY zeolite would lose most of its crystallinity and acidity within hours under regenerator conditions. USY survives because dealumination removes the most hydrolysis-susceptible framework aluminium atoms and replaces Al-O bonds with stronger Si-O bonds.

Tunable activity-selectivity balance. Unit cell size (UCS) is the primary QC parameter controlling FCC performance. Lower UCS (24.24-24.35 Å) means fewer but stronger acid sites, lower hydrogen transfer, and higher gasoline selectivity. Higher UCS (24.40-24.55 Å) provides more total acidity and higher cracking activity.

Mesoporosity for heavy-feed access. The secondary mesopores (20-500 Å) created during dealumination improve diffusion of heavy feed molecules to active sites, enhancing bottoms conversion and metals tolerance.

How to Select USY for FCC

Rare-earth exchange (RE-USY) increases acid site strength and density, promoting hydrogen transfer that saturates olefins and increases gasoline yield. For maximum propylene, select RE-free USY combined with ZSM-5 additive.

When requesting a sample, specify your target UCS window, RE₂O₃ level (if any), feedstock metals content, and desired product slate.