An investigation on the promoting effect of Pr modification on SO2 resistance over MnOx catalysts for selective reduction of NO with NH3

Abstract

Manganese oxides (MnO x ) exhibit excellent low-temperature activities in SCR reaction of NO with NH 3 , and they are considered as a promising catalyst for future application. However, MnO x still suffer from poor resistance to SO 2 and H 2 O. In this work, Pr was used to modify MnO x catalysts via co-precipitation process, and MnPrO x catalyst exhibited superior SO 2 resistance over pure MnO x catalyst. A series of characterization techniques, such as XRD, BET, H 2 -TPR, XPS, TG and in-situ DRIFTS, were adopted to explore the promoting effect of Pr modi cation on SO 2 resistance over MnO x catalyst in detail. The results indicated that, in the presence of SO 2 in feed gas, it seemed that PrO x rather than MnO x were apt to react with SO 2 , which was favorable to protect Mn active sites on the catalyst surface to some extent. It was known that there was strong competitive adsorption between SO 2 and NH 3 /NO species on SCR catalyst surface. In-situ DRIFTS results revealed that the adsorption of NH 3 and NO on MnO x catalyst had been severely suppressed after the introduction of SO 2 , resulting in the relevant SCR reactions following either L-H or E-R mechanisms would be inhibited obviously. But for Pr-modi ed MnO x catalyst, the introduction of SO 2 almost had no effect on the adsorption of NH 3 on catalyst surface, while it exerted a relatively noticeable impact on the adsorption of NO. As a result, SCR reactions occurred on Pr-modi ed MnO x catalyst surface could still proceed in a near-normal way through E-R rather than L-H mechanisms.Therefore, Pr modi cation on MnO x catalyst exhibited a distinctively promoting effect on SO 2 resistance performance in SCR process. HighlightsPr-modi ed MnO x catalyst exhibited superior SO 2 resistance over MnO x catalyst.Pr modi cation could inhibit the sulfation of Mn active sites on the surface of MnO x catalyst.For Pr-modi ed MnO x catalyst, the adsorption of NH 3 on Lewis acid sites was almost not affected by SO 2 , and the inhibition degree of SO 2 for NO adsorption was lower than that of MnO x catalyst.The SCR reaction on Pr-modi ed MnO x catalyst might follow E-R mechanism in the presence of SO 2 .

The promoting effect of support pretreatment with sulfate acid on the Ca resistance of a CeO2/ZrO2 catalyst for NH3-SCR of NOx with NH3

“…In recent years, some non-toxic SCR catalysts such as CuO, Fe 2 O 3 , MnO x and CeO 2 , have been widely investigated in order to substitute vanadium-based catalysts. [9][10][11][12] Among them, ceriumbased NH 3 -SCR catalysts have attracted a lot of researchers' interest due to their excellent reducibility and remarkable oxygen storage capacity, which are significant to the oxidation of NO x and the acceleration of NH 3 -SCR reactions. A great deal of effort has been devoted to improving the SCR performance of Ce-based catalysts.…”