Cu_x-Nb_{1.1- x} (x = 0.45, 0.35, 0.25, 0.15) bimetal oxides catalysts for the low temperature selective catalytic reduction of NO with NH₃

The Cu_x-Nb_{1.1- x} (x = 0.45, 0.35, 0.25, 0.15) bimetal oxides catalysts were synthesized through citric acid method and used in the selective catalytic reduction (SCR) of NO with NH₃. The relationship among the catalytic performances, the acid/redox properties and the structures of the binary oxides systems was explored through different characterization techniques including XRD, H₂-TPR, BET, NO-TPD, NH₃-TPD, XPS and in situ DRIFTS. The characterization results point out that the ratio of Cu to Nb has great influence on the activity of NH₃-SCR reaction. Different catalytic activities of Cu_x-Nb_{1.1- x} (x = 0.45, 0.35, 0.25, 0.15) mixed oxides could be attributed mainly to surface area, acid amount, the adsorption and activation of NH₃ and redox ability of the corresponding catalyst. Among these Cu_x-Nb_{1.1- x} (x = 0.45, 0.35, 0.25, 0.15) oxides catalysts, the Cu_0.25-Nb_0.85 catalyst exhibited the complete NO conversion in a reaction temperature range of 180-330 °C, together with near 100% N₂ selectivity and remarkable SO₂/H₂O resistance. Moreover, the Cu_0.25-Nb_0.85 catalyst still exhibited wide activity temperature window of 185-380 °C at above 90% NO conversion even in the presence of 5% H₂O under high GHSV of 70,000 h^-1. Thus, it can be summarized from the above results that Cu_0.25-Nb_0.85 can be considered as excellent catalyst for NH₃-SCR of NO.