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Selective catalytic reduction

About: Selective catalytic reduction is a research topic. Over the lifetime, 10502 publications have been published within this topic receiving 226291 citations.


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Journal ArticleDOI
Zhiming Liu1, Seong Ihl Woo1
TL;DR: In this paper, the authors classified the selective catalytic reduction (SCR) of NOx by hydrocarbon into two categories: one is the adsorption/dissociation mechanism, and the other is the oxidation reduction mechanism.
Abstract: The catalytic removal of nitrogen oxide (NOx) under lean‐burn conditions is one of the most important targets in catalysis research. Some lean‐NOx control technologies such as the direct decomposition of NOx, NOx storage‐reduction (NSR), and selective catalytic reduction (SCR) using different reducing agents (diesel soot, NH3, or hydrocarbon) are described. The reaction mechanism of NSR, which is the most promising technology, together with some novel NSR catalysts is discussed. Some mechanisms of SCR of NOx by hydrocarbon (HC‐SCR) were classified into two categories: one is the adsorption/dissociation mechanism, and the other is the oxidation‐reduction mechanism. Based on the discussion of the reaction mechanism, the influence of some factors (catalyst support, metal loading, calcination temperature, catalyst preparation method, oxygen, reducing agents, water, and sulfur) on the activity of HC‐SCR catalyst is discussed. It seems that Ag/Al2O3 catalyst offers the most promising for SCR of NOx by hydrocarb...

484 citations

Journal ArticleDOI
TL;DR: In this article, a series of TiO 2 supported manganese oxide catalysts were prepared by wet-impregnation method for the low temperature selective catalytic reduction (SCR) of NO with ammonia as a reductant.
Abstract: A series of TiO 2 supported manganese oxide catalysts were prepared by wet-impregnation method for the low temperature selective catalytic reduction (SCR) of NO with ammonia as a reductant. A combination of various physico-chemical techniques such as N 2 physisorption, O 2 chemisorption, TPR, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman were used to characterize the chemical environment of these catalysts. O 2 chemisorption and XRD results suggest that Mn exist in a well-dispersed state at below 16.7 wt.% of Mn on TiO 2 anatase (Hombikat), 7.5 wt.% on TiO 2 rutile (Kemira) and P-25 (80% anatase + 20% rutile), and in microcrystalline phase above these loading levels on respective support materials. These results also reveal that Mn interacts very well with pure anatase phase compared to rutile. XPS results of Mn/TiO 2 anatase (Hombikat) catalysts illustrated the presence of MnO 2 as a major phase (peak at 642.0 eV) along with Mn 2 O 3 as the minor phase at lower loadings. The presence of Mn 2 O 3 disappears at higher loadings. The characterization results indicated that the manganese oxide exists as an isolated species at very low loadings, highly dispersed state probably as two dimensional monolayer species at intermediate loadings, polymeric or microcrystalline form of manganese oxide at higher (above monolayer capacity) loadings was envisaged. The catalytic performance of various amounts of Mn loaded on different TiO 2 supported catalysts for low temperature SCR reaction at catalyst bed temperature 175 °C under power plant conditions using GHSV = 50,000 h −1 was studied. The catalyst with 16.7 wt.% Mn/TiO 2 anatase (Hombikat) was found to be highly active and selective catalyst for this reaction. The Raman studies acted as complimentary tool to XPS in order to characterize the manganese oxides (MnO, Mn 2 O 3 , Mn 3 O 4 , MnO 2 ). Raman data show that there is a strong interaction between the Mn oxides and the support, which is responsible for the impressive catalytic performance in comparison with other systems we investigated.

461 citations

Journal ArticleDOI
Zhongbiao Wu1, Boqiong Jiang1, Yue Liu1, Haiqiang Wang1, Ruiben Jin1 
TL;DR: The DRIFT spectroscopy for the adsorption of NH3 indicated the presence of coordinated NH3 and NH4+ on both of the two catalysts, indicating these species could react with NO effectively.
Abstract: Manganese oxides and iron-manganese oxides supported on TiO2 were prepared by the sol−gel method and used for low-temperature selective catalytic reduction (SCR) of NO with NH3. Base on the previous study, Mn(0.4)/TiO2 and Fe(0.1)−Mn(0.4)/TiO2 were then selected to carry out the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) investigation for revealing the reaction mechanism. The DRIFT spectroscopy for the adsorption of NH3 indicated the presence of coordinated NH3 and NH4+ on both of the two catalysts. When NO was introduced, the coordinated NH3 on the catalyst surface was consumed rapidly, indicating these species could react with NO effectively. When NH3 was introduced into the sample preadsorbed with NO + O2, SCR reaction would not proceed on Mn(0.4)/TiO2. However, for Fe(0.1)−Mn(0.4)/TiO2 the bands due to coordinated NH3 on Fe2O3 were formed. Simultaneously, the bidentate nitrates were transformed to monodentate nitrates and NH4+ was detected. And NO2 from the oxidation of NO on ...

456 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of the additive Ce on V2O5-WO3/TiO2 with low vanadium loadings for the selective catalytic reduction (SCR) of NOx with NH3 was investigated.
Abstract: The effect of the additive Ce on V2O5-WO3/TiO2 with low vanadium loadings for the selective catalytic reduction (SCR) of NOx with NH3 was investigated. The catalytic activity of 0.1% V2O5-6% WO3/TiO2 (V0.1W6Ti) was greatly enhanced by the addition of 10 wt % of Ce in the broad temperature range of 200−500 °C. The catalysts were characterized by BET, XRD, XPS, TPD, H2-TPR, and DRIFTS. The results indicated that the active components of V and W were well-dispersed, while a small cluster of cubic CeO2 appeared over the V0.1W6Ce10Ti catalyst. The Ce additive could enhance the NOx adsorption and then accelerate the SCR reaction due to the synergetic interaction among the Ce and V,W species. Ce mainly existed in the form of Ce3+ oxide in V0.1W6Ce10Ti catalysts, which was beneficial for the oxidation of NO to NO2. Moreover, the DRIFTS results showed that the Ce additive on V0.1W6Ti could provide stronger and more active Bronsted acid sites, which were beneficial for the SCR reaction. The Ce additive also enhance...

436 citations

Journal ArticleDOI
TL;DR: In this article, a series of high-activity manganese−cerium oxide catalysts for the low-temperature (373−453 K) selective catalytic reduction (SCR) of NOx with ammonia were prepared.
Abstract: A series of high-activity manganese−cerium oxide catalysts for the low-temperature (373−453 K) selective catalytic reduction (SCR) of NOx with ammonia were prepared. They were prepared by using the...

420 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023311
2022632
2021546
2020583
2019604
2018595