Promoting effect of SO2−4 functionalization on the performance of Fe2O3 catalyst in the selective catalytic reduction of NOx with NH3

Abstract

Fe(OH)3 and Fe2O3 were first prepared by a precipitation method and then sulfated to obtain the SO2−4 -functionalized SO2−4/Fe(OH)3 and SO2−4/Fe2O3 catalysts for the selective catalytic reduction of NOx with NH3 (NH3-SCR); the promoting effect of SO2−4 functionalization on the performance of Fe2O3 catalyst in NH3-SCR was then investigated. The results indicate that the SCR activity of the SO2−4 -functionalized Fe2O3 catalysts is significantly improved in comparison with that of unmodified Fe2O3. In particular, the SO2−4/Fe(OH)3 catalyst exhibits excellent performance in NH3-SCR, with the NOx conversion of over 80% at 250–450°C; besides, it also display high catalytic stability and resistance towards H2O + SO2. A series of characterization results including XRD, Raman spectroscopy, TG analysis, FTIR spectroscopy, H2-TPR, NH3-TPD and in situ DRIFTS reveal that the functionalization with sulfuric acid can inhibit the growth of Fe2O3 grains; moreover, SO2−4 combines with Fe3+ to form the sulfate complex, leading to an increase in the number of surface acid sites and the acid strength, which can inhibit the ammonia over-oxidation on Fe2O3 and enhance the deNOx performance of Fe2O3.