Effect of oxygen concentration on the NOx reduction with ammonia over V2O5–WO3/TiO2 catalyst

Djerad, Souad; Crocoll, Marcus; Kureti, Sven; Tifouti, L.; Weisweiler, Werner

doi:10.1016/j.cattod.2005.11.067

Cited by 113 publications

(63 citation statements)

References 18 publications

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“…It is not possible to achieve more than 65% of efficiency when lower O 2 concentration and higher temperature (566°C) are considered. These results agree partially with works conducted previously [28].…”

Section: Resultssupporting

confidence: 83%

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Optimization of Selective-Type Aftertreatment Systems in Diesel Engines

Lourenço¹,

Almeida²,

Glovaski³

2015

Anais Do XXIII Simpósio Internacional De Engenharia Automotiva

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Diesel engine technology has been driven by stringent regulation. To fulfill this demands emission control systems are constantly improving. In this context exhaust gas aftertreatment development assumes an important role however the in-cylinder emissions control is fundamental to comply with future legislations.Among the aftertreatment systems applied to reduce diesel engines combustion products the Selective Catalytic Reduction (SCR), which converts nitrogen oxides, (NO x ) into nitrogen N 2 and water H 2 O via dosing a chemical reducing agent containing ammonia in the exhaust system is an already proven solution for most medium and heavy duty Diesel (MDD and HDD) applications.The current work aims to compare the behavior of different urea and formamide-based reducing agents using a selective catalytic reduction aftertreatment system (ATS) when it comes to NO x reduction. Another purpose of this study in addition to studying the NO x reduction is also to understand the effects or side-effects in other gases like carbon monoxide (CO), carbon dioxide (CO 2 ), hydrocarbon (HC), oxygen (O 2 ), ammonia (NH 3 ) and to discuss in detail the potential of using this alternative reducing agents to comply with EURO VI standards and optimized SCR systems towards increasing their efficiency.Regarding the SCR catalyst system as to NO x reduction it is possible to say that urea-based mixtures are the most efficient ones but on the other hand are also those that present higher values of ammonia slip. The formamide-based mixtures do not present efficiency as significant as the urea-based mixtures but the ammonia slip levels produced by those mixtures are virtually none.With regard to CO and HC emissions the formamide-based mixtures have presented significant increase on the emissions of those two gases while in the urea-based mixtures the values have remained virtually unchanged.

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Section: Resultssupporting

confidence: 83%

“…This cycle is operated through a sequence of 13 modes with different engine speed and load conditions [28]. The final result is a weighted average of the 13 modes as shown in Figure 4.…”

Section: Metodologymentioning

confidence: 99%

Optimization of Selective-Type Aftertreatment Systems in Diesel Engines

Lourenço¹,

Almeida²,

Glovaski³

2015

Anais Do XXIII Simpósio Internacional De Engenharia Automotiva

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“…In addition to the main SCR reactions over V 2 O 5 -WO 3 (or MoO 3 )/TiO 2 catalysts, many side reactions can occur, and among them, one is the production of N 2 O that is a greenhouse gas with a global warming potential of 310 at a 100-year time horizon, and the extent of its emissions can greatly depend on the loading and crystallinity of V 2 O 5 , the secondary component, reaction temperature, concentrations of H 2 O and O 2 , and so forth [3,6,[11][12][13][14][15]. Such a formation of N 2 O in the NH 3 -SCR reaction is proposed by the following major routes [6,[12][13][14][15] …”

Section: Introductionmentioning

confidence: 99%

“…Such a formation of N 2 O in the NH 3 -SCR reaction is proposed by the following major routes [6,[12][13][14][15] …”

Section: Introductionmentioning

confidence: 99%

The Role of Fe2O3 Species in Depressing the Formation of N2O in the Selective Reduction of NO by NH3 over V2O5/TiO2-Based Catalysts

Kim

Yang

2018

Catalysts

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Promotion of 2.73% Fe 2 O 3 in an in-house-made V 2 O 5 -WO 3 /TiO 2 (VWT) and a commercial V 2 O 5 -WO 3 /TiO 2 (c-VWT) has been investigated as a cost effective approach to the suppression of N 2 O formation in the selective catalytic reduction of NO by NH 3 (NH 3 -SCR). The promoted VWT and c-VWT catalysts all gave a significantly decreased N 2 O production at temperatures >400 • C compared to the unpromoted samples. However, such a promotion led to the loss in high temperature NO conversion, mainly due to the oxidation of NH 3 to N-containing gases, particularly NO. Characterization of the unpromoted and promoted catalysts using X-ray diffraction (XRD), NH 3 adsorption-desorption, and Raman spectroscopy techniques could explain the reason why the promotion showed much lower N 2 O formation levels at high temperatures. The addition of Fe 2 O 3 to c-VWT resulted in redispersion of the V 2 O 5 species, although this was not visible for 2.73% Fe 2 O 3 /VWT. The iron oxides exist as a highly-dispersed noncrystalline α-Fe 2 O 3 in the promoted catalysts. These Raman spectra had a new Raman signal that could be tentatively assigned to Fe 2 O 3 -induced tetrahedrally coordinated polymeric vanadates and/or surface V-O-Fe species with significant electronic interactions between the both metal oxides. Calculations of the monolayer coverage of each metal oxide and the surface total coverage are reasonably consistent with Raman measurements. The proposed vanadia-based surface polymeric entities may play a key role for the substantial reduction of N 2 O formed at high temperatures by NH 3 species adsorbed strongly on the promoted catalysts. This reaction is a main pathway to greatly suppress the extent of N 2 O formation in NH 3 -SCR reaction over the promoted catalysts.

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“…Gas-phase NO reacts with adsorbed ammonia on the V=O sites and produces N 2 and H 2 O. Gas-phase oxygen then oxidizes the V=O site, preparing the site for another cycle of SCR reactions [39]. The increase in the oxygen content plays an important role in the formation of N 2 O by ammonia oxidation [40]. The NO removal rate tends to be stable at an oxygen content of >4%.…”

Section: Oxygen Concentrationmentioning

confidence: 99%

Experimental Research of an Active Solution for Modeling In Situ Activating Selective Catalytic Reduction Catalyst

et al. 2017

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Abstract:The effect of active solutions suitable for the in situ activation of selective catalytic reduction (SCR) catalysts was experimentally investigated using a designed in situ activation modeling device. To gain further insight, scanning electron microscopy (SEM), specific surface area analysis (BET), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) analyses were used to investigate the effects of different reaction conditions on the characteristics of the deactivated catalysts. The activation effect of loading V 2 O 5 , WO 3 and MoO 3 on the surface of the deactivated catalysts was analyzed and the correlation to the denitrification activity was determined. The results demonstrate that the prepared activating solution of 1 wt % vanadium (V), 9 wt % tungsten (W), and 6 wt % molybdenum (Mo) has a beneficial effect on the deactivation of the catalyst. The activated catalyst resulted in a higher NO removal rate when compared to the deactivated catalyst. Furthermore, the NO removal rate of the activated catalyst reached a maximum of 32%. The activity of the SCR catalyst is closely linked to the concentration of the active ingredients. When added in optimum amounts, the active ingredients helped to restore the catalytic activity. In particular, the addition of active ingredients, the availability of labile surface oxygen, and the presence of small pores improved the denitrification efficiency. Based on these results, active solutions can effectively solve the problem of denitrification catalyst deactivation. These findings are a reference for the in-situ activation of the selective catalytic reduction of nitrogen oxides (SCR-DeNOx) catalyst.

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Effect of oxygen concentration on the NOx reduction with ammonia over V2O5–WO3/TiO2 catalyst

Cited by 113 publications

References 18 publications

Optimization of Selective-Type Aftertreatment Systems in Diesel Engines

Optimization of Selective-Type Aftertreatment Systems in Diesel Engines

The Role of Fe2O3 Species in Depressing the Formation of N2O in the Selective Reduction of NO by NH3 over V2O5/TiO2-Based Catalysts

Experimental Research of an Active Solution for Modeling In Situ Activating Selective Catalytic Reduction Catalyst

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