IR Spectroscopy Analysis and Kinetic Modeling Study for NH₃ Adsorption and Desorption on H- and Fe-BEA Catalysts

Abstract

Among different types of Fe-exchanged zeolites, Fe-BEA exhibits very promising surface properties for developing efficient urea or NH 3 -SCR systems. In this work, dedicated experimental and kinetic modeling studies were performed in order to elucidate mechanistic aspects related to NH 3 storage and release on these catalysts. A series of NH 3 adsorption and desorption experiments were performed over both H- and Fe-exchanged BEA zeolites, taking into account a broad range of operating conditions. Coupling FTIR spectroscopy, surface NH 3 adspecies were characterized. NH 3 gaseous concentration profiles were subsequently simulated by means of a detailed multisite kinetic model, being able to account for low-temperature adsorption phenomena. Finally, correlations between surface acidity and model sites were enabled by comparing IR spectroscopy and model predicted results, leading to the development of a phenomenological semidetailed, multisite kinetic modeling approach.