Effect of ceria loading on Zr-pillared clay catalysts for selective catalytic reduction of NO with NH3

Abstract

yCeO₂/Zr-PILC (y = 2.5–7.4 wt%) catalysts were prepared using an impregnation method. The physiochemical properties of the materials were investigated by means of XRD, BET, XPS, H₂-TPR, NH₃-TPD, and in situ DRIFT techniques, and their catalytic activities were evaluated for the selective catalytic reduction of NO with ammonia (NH₃-SCR). The 5CeO₂/Zr-PILC sample showed a high NH₃-SCR activity, with the NO conversion being more than 80% in the temperature range (350–450 °C). The Zr-incorporated support was beneficial for the dispersion of ceria. There was a strong interaction between ceria and Zr-PILC, which led to increased H₂ consumption and high-temperature reduction. An appropriate CeO₂ loading could generate the 5CeO₂/Zr-PILC catalyst that contained higher amounts of Ce³⁺ and the chemisorbed oxygen species favoring the NH₃-SCR reaction. Moreover, the high acidity and strong NH₃ adsorption ability of 5CeO₂/Zr-PILC were responsible for good NH₃-SCR performance in a wide temperature range. The NH₃-SCR reaction occurred according to both the Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms, with the former being dominant.