EFAL extra-framework aluminum

For the dealuminated zeolites produced by exposing Na-Y to an SiCU stream, an enhanced concentration of extra-framework aluminum species (EFAL) inside the zeolite crystal was discovered, and heats > 130kjmol were observed in the SiCU-treated samples. This was not the case on faujasites dealuminated with EDTA, which showed a lower concentration of strong... 

A more in-depth study on FAU-structiu e zeolites with high siUca content by Beyerlein et al. [108] addresses the influence of extra-framework species (EFAL) on the catalytic activity for the isobutane conversion. Overall, the cracking activity increased linearly with the concentration of framework aluminum sites for all catalysts. However, FAU samples dealuminated with ammonium hexafluorosilicate (AHF) showed a lower activity compared to conventionally hydrothermally treated catalysts. Steaming of the chemically dealuminated catalysts led to an increased activity in cracking isobutane compared to the parent FAU. This is interpreted as an indication that extraframework aluminum species, typically acting as Lewis add sites, are interacting with Bronsted acid sites to form new and stronger addic sites. 

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