A review of Mn-containing oxide catalysts for low temperature selective catalytic reduction of NOx with NH3: reaction mechanism and catalyst deactivation
Open Access
- 16 May 2017
- journal article
- review article
- Published by Royal Society of Chemistry (RSC) in RSC Advances
- Vol. 7 (42), 26226-26242
- https://doi.org/10.1039/c7ra03387g
Abstract
Atmospheric pollutants of nitrogen oxides (NOx) can be reduced by selective catalytic reduction (SCR). SCR of NOx with ammonia (NH3) at low temperatures has attracted much interest for high nitric oxide (NO) conversion, and this method is dominated by catalysts. Manganese (Mn)-containing oxide catalysts exhibit high activity and selectivity for the unique redox property of manganese oxides (MnOx). The reaction mechanisms and deactivation processes are summarized in this review. SCR of NOx with NH3 follows both the Langmuir–Hinshelwood and the Eley–Rideal mechanisms, which also contribute to the nitrous oxide formation. Fast SCR has a higher reaction rate than standard SCR. Mn-containing catalysts could also be deactivated by sulfur oxides and water vapor. The deactivation process of sulfur dioxide can be classified into two categories: deposition of (NH4)2SO4 and sulfation of active sites. The deactivation caused by water vapor can be attributed to the competitive adsorption. The adsorption of water on catalysts' surface blocked the active sites, which are provided for the adsorption of NH3 and NO. Alkali, alkaline earth and heavy metal ions existing in fine fly ash can also damage the catalysts' acid sites. A notable improvement on performance was obtained when Mn-containing catalysts were doped with a transition metal, for these enhanced its adsorption capacity and oxidation ability. Furthermore, this review gives a comprehensive discussion of the synergistic mechanism between bi-metal or multi-metal oxides. Major conclusions and several possible directions for further research are presented finally.Keywords
This publication has 100 references indexed in Scilit:
- Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3Applied Surface Science, 2013
- Mechanism study of the promotional effect of O2 on low-temperature SCR reaction on Fe–Mn/TiO2 by DRIFTChemical Engineering Journal, 2013
- In situ DRIFTS study of NO reduction by NH3 over Fe–Ce–Mn/ZSM-5 catalystsCatalysis Today, 2011
- Low-temperature selective catalytic reduction of NOx with NH3 over metal oxide and zeolite catalysts—A reviewCatalysis Today, 2011
- Cr–MnOx mixed-oxide catalysts for selective catalytic reduction of NOx with NH3 at low temperatureJournal of Catalysis, 2010
- Relationship between SO2 poisoning effects and reaction temperature for selective catalytic reduction of NO over Mn–Ce/TiO2 catalystCatalysis Today, 2010
- Selective catalytic reduction of NO with NH3 over manganese substituted iron titanate catalyst: Reaction mechanism and H2O/SO2 inhibition mechanism studyCatalysis Today, 2010
- Low temperature selective catalytic reduction of NO by activated carbon fiber loading lanthanum oxide and ceriaApplied Catalysis B: Environment and Energy, 2010
- Regenerable ceria-based SOx traps for sulfur removal in lean exhaustsApplied Catalysis B: Environment and Energy, 2008
- Nitrogen Cycles: Past, Present, and FutureBiogeochemistry, 2004