Modification of MnCo2Ox catalysts by NbOx for low temperature selective catalytic reduction of NO with NH3

A series of MnCo2Ox catalysts modified with different Nb ratios were synthesized by co-precipitation and sol–gel method. The effects of niobia on the low-temperature NH3-SCR performances of the catalysts were investigated. The MnCo2O4 spinel phase was identified according to XRD and Raman results. Niobates including Mn2NbOx and Co2NbOx appeared with the increase of the Nb loading based on the Raman and H2-TPR results. Among the obtained catalysts, MnCo2Nb0.5Ox presented the best catalytic performance with a broad operation temperature window, high N2 selectivity and good H2O resistance. It was found that the addition of niobia weakened the redox properties of the catalysts to some extent, resulting in the decrease of NO conversion at 50 °C. This, as well as the enhanced surface acidity, inhibited the unselected oxidation of NH3 to N2O and increased the N2 selectivity over the modified catalysts. Consequently, the modification of MnCo2Ox catalyst by NbOx promoted the low-temperature NH3-SCR performance.