Journal ArticleDOI
The Effect of an Oxidation Precatalyst on the NOx Reduction by Ammonia SCR
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In this paper, the performance of SCR and SCR catalysts was investigated individually and as a combined system for the removal of NOx by ammonia using synthetic gas mixtures matching the composition of diesel exhaust.Abstract:
The performances of oxidation and SCR catalysts were investigated individually and as a combined system for the removal of NOx by ammonia. Experiments were carried out with synthetic gas mixtures matching the composition of diesel exhaust. Introducing an oxidation catalyst upstream of the SCR catalyst enhances the removal of NOx at low temperatures. The beneficial effects of combining the two catalysts are the oxidation of unburned hydrocarbons that inhibit the SCR reaction and the conversion of NO to NO2 on the oxidation catalyst. NO2 fractions up to 50% of total NOx enhance the NOx conversion at temperatures below 300 °C. However, excess NO2 should be avoided because the reaction of NO2 with ammonia is slow, resulting in a decreased NOx conversion. Above 350 °C, the NOx conversion essentially does not depend on the ratio NO2/NOx or on the presence of hydrocarbons in the feed. A simple mathematical prediction of the NOx conversion for the combined system is also possible. The parameters used in this calc...read more
Citations
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Journal ArticleDOI
Low-temperature selective catalytic reduction of NOx with NH3 over metal oxide and zeolite catalysts—A review
TL;DR: In this paper, two types of low-temperature catalysts, the metal oxide catalyst and metal exchanged zeolite catalyst, were reviewed for selective catalytic reduction of NO x with ammonia (NH 3 -SCR) especially at temperature below 200°C.
Journal ArticleDOI
Effect of manganese substitution on the structure and activity of iron titanate catalyst for the selective catalytic reduction of NO with NH3
TL;DR: In this article, the selective catalytic reduction (SCR) of NO with NH3 over manganese substituted iron titanate catalysts was investigated and the Mn substitution amounts showed obvious influence on the catalyst structure, redox behavior and NH3/NOx adsorption ability of the catalysts.
Journal ArticleDOI
The chemistry of the NO/NO2–NH3 “fast” SCR reaction over Fe-ZSM5 investigated by transient reaction analysis
TL;DR: In this article, the authors present a systematic study of the chemical steps in the NO/NO2−NH3 fast SCR reaction 2NH3+NO+NO2 → 2N2+3H2O over a commercial Fe-ZSM5 catalyst.
Journal ArticleDOI
Reactivity of NO/NO2–NH3 SCR system for diesel exhaust aftertreatment: Identification of the reaction network as a function of temperature and NO2 feed content
Cristian Ciardelli,Isabella Nova,Enrico Tronconi,Daniel Chatterjee,Brigitte Bandl-Konrad,Michel Weibel,Bernd Krutzsch +6 more
TL;DR: In this article, the NH3-SCR reactivity over a commercial V2O5-WO3/TiO2 catalyst in a wide range of temperatures and NO/NO2 feed ratios was investigated.
Journal ArticleDOI
Influence of NO2 on the selective catalytic reduction of NO with ammonia over Fe-ZSM5
Mukundan Devadas,Oliver Kröcher,Martin Elsener,Alexander Wokaun,Nicola Söger,Marcus Pfeifer,Yvonne Demel,Lothar Mussmann +7 more
TL;DR: In this article, the influence of NO2 on the selective catalytic reduction (SCR) of NO with ammonia was studied over Fe-ZSM5 coated on cordierite monolith.
References
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Journal ArticleDOI
Urea-SCR: a promising technique to reduce NOx emissions from automotive diesel engines
TL;DR: In this article, the authors discuss the fundamental problems and challenges if urea-SCR is extended to mobile applications, including the control strategy for urea dosing, the high freezing point of urea, and the long term stability of the catalyst.
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Nitric oxide catalysis in automotive exhaust systems
TL;DR: In this paper, a review of the literature on NO catalysis is presented, focusing on the threeway catalyst system which simultaneously promotes the reduction of nitrogen oxides and the oxidation of carbon monoxide and hydrocarbons.
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Reaction Pathways in the Selective Catalytic Reduction Process with NO and NO2 at Low Temperatures
TL;DR: The low-temperature behavior of the selective catalytic reduction (SCR) process with feed gases containing both NO and NO2 was investigated in this article, where the two main reactions are 4NH3 + 2NO + 2 NO2 → 4N2 + 6H2O and 2NH3+ 2NO2 → NH4NO3 + N2 + H2O.
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Selective catalytic reduction of NO and NO2 at low temperatures
TL;DR: In this paper, the authors investigated the effect of ammonium nitrate on the SCR reaction in the presence of NO and showed that ammonium Nitrate can lead to the formation of NO 2.
Journal ArticleDOI
Hydrolysis of Isocyanic Acid on SCR Catalysts
TL;DR: In this article, the authors compared the first-order rate constants of HNCO hydrolysis with the SCR reaction using the integral equation for a plug-flow reactor.