Kinetic Modelling of the Adsorption and Desorption of NH3 on Fe/BEA Zeolite

This paper deals with the kinetic modelling of the adsorption and desorption of NH3 on Fe/BEA zeolite. Fe/BEA was recently reported to show high activity for the selective catalytic reduction (SCR) of NOx by NH3. The NH3 adsorption and desorption kinetics was examined in the temperature range from 323 to 923 K using temperature programmed desorption of NH3 (NH3-TPD) and diffuse reflectance infrared fourier transform spectroscopy (DRIFTS). With these investigations an elementary kinetic mean field model of the NH3 adsorption and desorption was constructed employing Arrhenius-based rate expressions. The model differentiated molecularly bound NH3 and NH4+ surface species originated from the NH3 chemisorption. For both kinds of species, the kinetic parameters of the adsorption of NH3 were adopted from the literature, while that of the desorption were numerically fitted based upon NH3-TPD traces. The reliability of the kinetic model was evidenced by reproduction and prediction of the NH3-TPD profiles as well as thermodynamic consistency.