The role of Al and strong acidity in the selective catalytic oxidation of NH3 over Fe-ZSM-5

Abstract

Fe-ZSM-5 catalysts prepared using different techniques have been used to highlight the role of aluminium-associated sites and hence Bronsted acidity during the selective catalytic oxidation (SCO) of NH3. NH3–TPD was used to characterise the type of acidity and the number of acid sites in the Fe-ZSM-5 materials. Catalysis was carried out in a fixed bed Pyrex micro reactor operated at atmospheric pressure and a temperature range of 623–723K. Results show that catalysts with no Al and hence possessing only weak acidity had lower performance during the SCO of NH3. The presence of Al in the zeolite framework is believed to be of importance in stabilising the Fe active species. The oxidative activity of the catalysts was thus found to depend on the presence or absence of Al, whilst only Fe-H-[Al]ZSM-5 catalyst was both active and selective.