Promotional role of Nb modification on CuCeOx catalyst for low temperature selective catalytic reduction of NO with NH3: A mechanism investigation

CuCeOx and CuCeNbOx-k with different Nb doping ratios were obtained by the citric acid method and applied in NH3-SCR process. The activity test results elucidated that the addition of Nb effectively ameliorated the low-temperature SCR performance. Among them, CuCeNbOx-0.4 catalyst had the finest SCR activity (more than 90% in 185-370 degrees C), highest N-2 selectivity, excellent SO2&H2O resistance and thermal stability. Numerous characterization analysis demonstrated that CuCeNbOx-0.4 had the largest specific surface area, the strongest surface acidity and the most excellent redox properties. The conclusions of in situ DRIFT manifested the Nb modification generated more activated species, enhanced the reactivity of ad-NH3 and ad-NOx species, and the SCR reaction on CuCeNbOx-0.4 mainly followed the Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. Furthermore, the Nb doping also formed the dual redox cycle (Cu2+ + Nb4+ <-> Cu+ + Nb5+, Cu2+ + Ce3+ <-> Cu+ + Ce4+), which facilitated the low-temperature SCR reaction.