Reaction between nitrogen oxide (NOx) and ammonia on iron oxide-titanium oxide catalyst

Kato, Akira; Matsuda, Shimpei; Kamo, Tomoichi; Nakajima, Fumito; Kuroda, Hiroshi; Narita, T.

doi:10.1021/j150626a029

Cited by 138 publications

(83 citation statements)

References 4 publications

(6 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While HC-SCR has been largely studied in the past decades for automotive applications, the NH3-SCR is now accepted as exhibiting the highest potential to reduce NOx emission in the lean condition, with different reaction pathways described by Equations (1)- (3). These reactions are usually denoted as "standard-SCR" (Equation (1)), "fast-SCR" (Equation (2)) and "NO2-SCR" (Equation (3)) reactions [9,[16][17][18][19][20]:…”

Section: Introductionmentioning

confidence: 99%

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

et al. 2015

View full text Add to dashboard Cite

Abstract:The selective catalytic reduction (SCR) of NOx by NH3 has been extensively studied in the literature, mainly because of its high potential to remediate the pollution of diesel exhaust gases. The implementation of the NH3-SCR process into passenger cars requires the use of an ammonia precursor, provided by a urea aqueous solution in the conventional process. Although the thermal decomposition and hydrolysis mechanisms of urea are well documented in the literature, the influence of the direct use of urea on the NOx reduction over SCR catalysts may be problematic. With the aim to evaluate prototype powdered catalysts, a specific synthetic gas bench adjusted to powdered material was developed, allowing the use of NH3 or urea as reductant for direct comparison. The design of the experimental setup allows vaporization of liquid urea at 200 °C under 10 bar using an HPLC pump and a micro injector of 50 μm diameter. This work presents the experimental setup of the catalytic test and some remarkable catalytic results towards further development of new catalytic formulations specifically dedicated to urea-SCR. Indeed, a possible divergence in terms of DeNOx efficiency is evidenced depending on the nature of the reductant, NH3 or urea solution. Particularly, the evaluated catalyst may not allow an optimal NOx conversion because of a lack in ammonia availability when the urea residence time is shortened. This is attributed to insufficient activity of isocyanic acid (HNCO) hydrolysis, OPEN ACCESSCatalysts 2015, 5 1536 which can be improved by addition upstream of an active solid for the hydrolysis reaction such as ZrO2. Thus, this µ-scale synthetic gas bench adjusted to powdered materials enables the specific behaviour of urea use for NOx reduction to be demonstrated.

show abstract

Section: Introductionmentioning

confidence: 99%

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

et al. 2015

View full text Add to dashboard Cite

show abstract

“…The reaction between equimolar NO-NO 2 and NH 3 is c.a. 10 times faster than the reaction between NO and NH 3 at low temperatures (200-300 8C) [10]. Therefore, the fast SCR reaction is considered as a feasible means to boosting the denitrification efficiency at lower temperatures as well as to reducing the catalyst costs of SCR system.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of nitric oxide to nitrogen dioxide over Ru catalysts

Cheng

et al. 2009

Applied Catalysis B: Environmental

View full text Add to dashboard Cite

“…Currently NH 3 or urea SCR is also being increasingly employed to reduce NO x in the exhaust gases of internal combustion engines operated with an excess of air, such as Diesel engines installed in heavy-duty vehicles and passenger cars. Zeolite-based catalysts promoted by transition metals such as Fe and Cu are considered for this application.…”

mentioning

confidence: 99%

Enhanced NH₃ Selective Catalytic Reduction for NO_x Abatement

2009

View full text Add to dashboard Cite

Nitrogen oxides NO x , which include NO (nitrogen monoxide), NO 2 (nitrogen dioxide), and N 2 O (nitrous oxide), are currently considered to be among the most dangerous air pollutants, as they cause acid rain, contribute to photochemical smog, and have direct harmful effects on human health. For all these reasons, in the last decades NO x emissions have been regulated in industrialized countries by more and more restrictive legislation.[1] Selective catalytic reduction (SCR) technology is well established and used worldwide to control NO x emissions from power plants and other stationary sources. A hot exhaust gas is passed over an extruded honeycomb monolith catalyst consisting of V 2 O 5 -WO 3 /TiO 2 [2] in the presence of a nitrogenous reductant such as ammonia or urea (an ammonia carrier), which converts NO x to nitrogen according to the so-called standard SCR reaction (1).Currently NH 3 or urea SCR is also being increasingly employed to reduce NO x in the exhaust gases of internal combustion engines operated with an excess of air, such as Diesel engines installed in heavy-duty vehicles and passenger cars. Zeolite-based catalysts promoted by transition metals such as Fe and Cu are considered for this application. One problem of SCR systems for vehicles, however, is poor activity at low temperatures where most of the NO x is produced, for example, during cold startup and on traveling short distances. The chosen method to boost the DeNOx activity of SCR catalysts for mobile applications at low temperature is to increase the NO 2 /NO molar feed ratio (NO 2 accounts only for few percent of total NO x in the engine exhaust) and thus promote the fast SCR reaction (2).This is realized in practice by installing a Diesel oxidation catalyst (DOC), typically consisting of precious metals carried on a flow-through honeycomb support, to convert a portion of NO to NO 2 upstream of the SCR converter. Thus, considerable improvements in NO x conversion are achieved, and the highest DeNOx efficiencies correspond to the NO 2 /NO molar ratio of 1/1 associated with reaction (2).[4] However, the oxidation activity of the DOC is strongly dependent on temperature and flow rate of the exhaust gases, so that optimal NO 2 /NO feed ratio cannot be guaranteed for all possible engine operating conditions.Here we reveal that a superior NO conversion efficiency can also be achieved by means of an enhanced SCR reaction [5] involving selective reduction of NO to N 2 by NH 3 and nitrate species such as ammonium nitrate [reaction (3)].The new reaction has very high DeNOx efficiency at low temperatures, similar to that of fast SCR, even though no NO 2 is fed to the SCR catalyst; accordingly, it can replace reaction (2) in boosting NH 3 SCR activity without the necessity of pre-oxidizing NO. Figure 1 shows the temporal evolution of the NO, NH 3 , and NO 2 outlet concentrations during one run at 205 8C over an Fe-ZSM-5 washcoated monolith catalyst. Initially only equimolar amounts of NH 3 and NO (1000 ppm each) were fed to the catalyst in a nitro...

show abstract

Reaction between nitrogen oxide (NOx) and ammonia on iron oxide-titanium oxide catalyst

Abstract: Die Reduktion von N0x (N02 oder NO + N02) mit NH3 an einem Fe‐oxid/Ti‐oxid‐Katalysator wird in einem Strömungsreaktor untersucht.

Cited by 138 publications

References 4 publications

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

Oxidation of nitric oxide to nitrogen dioxide over Ru catalysts

Enhanced NH₃ Selective Catalytic Reduction for NO_x Abatement

Contact Info

Product

Resources

About

Reaction between nitrogen oxide (NOx) and ammonia on iron oxide-titanium oxide catalyst

Abstract: Die Reduktion von N0x (N02 oder NO + N02) mit NH3 an einem Fe‐oxid/Ti‐oxid‐Katalysator wird in einem Strömungsreaktor untersucht.

Cited by 138 publications

References 4 publications

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

Oxidation of nitric oxide to nitrogen dioxide over Ru catalysts

Enhanced NH3 Selective Catalytic Reduction for NOx Abatement

Contact Info

Product

Resources

About

Enhanced NH₃ Selective Catalytic Reduction for NO_x Abatement