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Dealumination–aging pattern of REUSY zeolites contained in fluid cracking catalysts
Authors:Francisco Hernndez-Beltrn  Juan Carlos Moreno-Mayorga  María de Lourdes Guzmn-Castillo  Juan Navarrete-Bolaos  Montserrat Gonzlez-Gonzlez  Brent E Handy
Affiliation:

a Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, 07730, Mexico City, DF, Mexico

b CIEP, Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, Av. Dr. Manuel Nava 6, Zona Universitaria, 78210, San Luis Potosi, SLP, Mexico

Abstract:The evolution of the properties of a REUSY zeolite contained in a fluid cracking catalyst was investigated under laboratory steam deactivation procedures and in age fractions of the corresponding equilibrium catalyst (Ecat). The aging pattern, defined by the evolution of the zeolite surface area (ZSA) related to the decrease of the unit cell size (UCS), was similar between lab-steamed zeolites and Ecat fractions. A sharp drop in ZSA occurred at ca. 2.430 nm UCS. A study done by FT-IR spectroscopy suggested that zeolite dealumination initially took place more extensively on the sodalite cages and double six-member rings (D6R) of the structure and that the final collapse of the zeolite framework occurred through destruction of the 12-member rings (12M). This can be explained by a crystal fracture and break down process and disassembling of the sodalite cages in the faujasite structure. NH3 microcalorimetry showed that strong acid sites in faujasites are destroyed by steam aging, but this effect does not lead to a reduction in the cracking activity of the Ecat form. The microactivity test (MAT) showed that the specific activity declined sharply at 2.430 nm UCS. Differences in product selectivity were related to the extent of damage of the zeolite, extra-framework alumina and mesoporosity. While further aging canceled the effect attributed to extra-framework alumina differences attributed to mesoporosity increased.
Keywords:Zeolite  Faujasite  USY  Fluid cracking  Dealumination  Steam aging
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