Effect of an Al2O3-based binder on the structure of extruded Fe-ZSM-5

The effect of an alumina-based binder on the structure of a commercial Fe-ZSM-5 catalyst has been investigated. Several ex-situ characterization techniques were used to show that the binder in the catalyst formulation allows obtaining a material that possesses improved features in terms of Fe species dispersion, framework Al content and acidity. UV-Vis and X-ray absorption spectroscopy showed that the extent of Fe agglomeration in the extruded catalyst was significantly lower compared to that in the catalyst without binder. Al-27 and Si-29-MAS NMR spectroscopy demonstrated a remarkable difference in terms of framework Al migration. NH3-TPD experiments corroborated the NMR results suggesting a retention of Bronsted acidity in the extruded catalyst. We tentatively propose that by providing extra-framework Al species prior to the treatment at elevated temperature, the binder hinders the framework Al dislodgment and Fe agglomeration during calcination.