Fe‐Beta@CeO2 core‐shell catalyst with tunable shell thickness for selective catalytic reduction of NOx with NH3

A series of core‐shell structural deNO_x catalysts using small‐grain Beta supporting FeO_x nanoparticles as the core and tunable CeO₂ thin film thickness as sheaths were designed and controllably synthesized. Their catalytic performances were tested for selective catalytic reduction of NO_x with NH₃ (NH₃‐SCR). It was found that CeO₂ shell thickness plays an important role in influencing the acidity and redox properties of the catalysts. Fe‐Beta@CeO₂ core‐shell catalysts exhibit excellent resistance to H₂O and SO₂ and high NO_x conversion (above 90%) in the wide temperature range (225–565°C). The kinetics result indicates that the coating of CeO₂ shell significantly increases the pore diffusion resistance of Fe‐Beta@CeO₂ catalysts. Furthermore, in situ DRIFT results reveal that CeO₂ shell can promote the formation of NO₂ and cis‐ species. But too thick CeO₂ shell (～20 nm) would result in the formation of inactive nitrate species, and thereby lead to a decrease of high‐temperature activity of the catalysts. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4430–4441, 2017