Sb loaded MnOx/TiO 2 /CNTs catalysts for Selective catalytic reduction of NOx: insight to the SO 2 and H 2 O tolerance

Abstract

A series of Sb containing CNTs based MnOx/TiO2 catalysts were prepared by the incipient wetness co-impregnation method and tested for the selective catalytic reduction (SCR) of NOx with NH3. The Sb loaded MnOx/TiO2-CNTs catalyst showed better performance than the other catalysts tested and presented the highest activity in the temperature regime of 100–400 oC. Interestingly, Sb loaded catalyst exhibited SO2 and H2O resistance with better thermal stability. Physico-chemical characterizations such as SEM, XRD, BET, XPS, NH3-TPD, and H2-TPR were employed to investigate the influence of Sb loading on NOx removal over MnOx/TiO2-CNTs catalysts. A step-wise addition of SO2 into the gas stream disclosed that MnOx-Sb/TiO2-CNTs catalyst has better SO2 resistance by avoiding the sulphur poisoning than the base catalyst MnOx/TiO2. Moreover, the results of SEM and XRD revealed that the dispersion of MnOx on TiO2/CNT surface was more uniform after Sb loading. We evidenced that the decrease in SCR activity of MnOx based catalyst is due to the formation of MnSO4. Indeed, in Sb loaded catalysts, the SOx species react more preferably with SbOx than that of MnOx. This strong interaction of SO2 with SbOx successfully prevents the poisoning of active sites on MnOx from being sulphated. This significantly improved the SO2 tolerance of Sb-loaded catalysts.