Continuous reduction of NO with octane over a silver/alumina catalyst in oxygen-rich exhaust gases: combined heterogeneous and surface-mediated homogeneous reactions

Eränen, Kari; Lindfors, Lars-Eric; Klingstedt, Fredrik; Murzin, Dmitry Yu.

doi:10.1016/s0021-9517(03)00195-7

Cited by 80 publications

(52 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…loading was between 5 and 7 wt % in contrast to literature, 2,8,15,17,20,21,33,34,42,43 where 2 wt % is typically reported as the standard catalyst. It is believed that these high loadings of silver can be obtained by using boehmite as the precursor for γ-alumina, as this ensures a high surface area for the final catalyst (see Table 1) and has been reported 35 to maintain a strong interaction between silver and alumina, preventing silver from sintering during calcination.…”

Section: Resultsmentioning

confidence: 82%

“…This finding is in agreement with previous findings that the presence of NO strongly influences the activation of the hydrocarbon. 8,13,15 The hydrogen effect will be discussed in more detail based on the combined in situ EXAFS and DRIFTS measurements.…”

Section: Resultsmentioning

confidence: 99%

“…1,[4][5][6][7][8][9][10][11][12] The large Ag 0 clusters cause unselective combustion of the reducing agent and the formation of N 2 O, a harmful greenhouse gas, whereas all of the other silver species have been proposed to be the active sites for SCR. 1,9,[11][12][13][14] The lack of certainty on the type of the active site is due to the complex nature of the SCR reaction, 1,15 the mobility of silver species under reaction condition, 3,16 and the influence of temperature and gas-phase composition on the formed surface species. 17 Hydrocarbons are used as reducing agents for the SCR reaction (HC-SCR) with silver alumina catalysts, and in the past decades the use of several different hydrocarbons, ranging from short-chain hydrocarbons, such as propane 2,7,12,18 and propene, 11,19 to long-chain hydrocarbons such as octane, 15,20,21 decane, 17 and real diesel fuel, 22 has been studied.…”

Section: Introductionmentioning

confidence: 99%

“…1,9,[11][12][13][14] The lack of certainty on the type of the active site is due to the complex nature of the SCR reaction, 1,15 the mobility of silver species under reaction condition, 3,16 and the influence of temperature and gas-phase composition on the formed surface species. 17 Hydrocarbons are used as reducing agents for the SCR reaction (HC-SCR) with silver alumina catalysts, and in the past decades the use of several different hydrocarbons, ranging from short-chain hydrocarbons, such as propane 2,7,12,18 and propene, 11,19 to long-chain hydrocarbons such as octane, 15,20,21 decane, 17 and real diesel fuel, 22 has been studied. The structure of the hydrocarbon only influences the activity of the catalysts; increasing the number of carbons and the linearity of the carbon chain increases the activity of the catalyst but does not affect its selectivity.…”

Section: Introductionmentioning

confidence: 99%

“…29 The organic nitrites, nitro, amino species, cyanide, and isocyanate species readily react with water-forming ammonia that can reduce surface-bound or gaseous NO x to N 2 . 29 In addition to the above-discussed surface reactions, it has been shown that homogeneous gas-phase reactions occur under SCR conditions 15 and that the presence of water enhances the formation of gaseous ammonia. 21 The addition of small amounts of hydrogen (<1%) significantly improves the performance of silver alumina and silverexchanged ZSM-5 catalysts, 2,10,30,31 whereas this effect is not observed for ZrO 2 -, TiO 2 -, Ga 2 O 3 -, or SiO 2 -supported silver catalysts nor for Co or Pt on alumina catalysts.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

New Insights into the Active Surface Species of Silver Alumina Catalysts in the Selective Catalytic Reduction of NO

et al. 2010

View full text Add to dashboard Cite

The performance of silver alumina catalysts and silver aluminate was studied in the selective catalytic reduction (SCR) of NO by propene. The use of boehmite during the impregnation step ensured a strong interaction between the silver species and the alumina surface in the final calcined catalyst. Thus, higher silver loadings (5-7 wt % silver) could be used without significant loss in selectivity to N 2 during SCR. The nature of the silver species and the formation of adsorbed surface species during SCR and hydrogen-assisted SCR (H 2 -SCR) was studied by activity measurements and by combined in situ IR and X-absorption spectroscopic measurements. The combination of these techniques in the same reaction cell allowed simultaneous monitoring of the state of silver and the formation of surface species under realistic reaction conditions. The active silver species on alumina support were concluded to be 2-dimensional oxidic Ag n δ+ species. Silver aluminate was ruled out as a possibility for an active phase for the SCR reaction. The oxidic Ag n δ+ species were present under both SCR and H 2 -SCR reaction conditions and even on a prereduced catalyst under the SCR reaction conditions. Hydrogen is proposed to enhance the formation of adsorbed surface species, especially nitrites, but not to change the nature of the active silver sites.

show abstract

Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

New Insights into the Active Surface Species of Silver Alumina Catalysts in the Selective Catalytic Reduction of NO

et al. 2010

View full text Add to dashboard Cite

show abstract

Photoionization Mass Spectrometry for Online Detection of Reactive and Unstable Gas‐Phase Intermediates in Heterogeneous Catalytic Reactions

You

Huang

2019

ChemCatChem

View full text Add to dashboard Cite

Heterogeneous catalytic reactions always involve surface intermediates on catalyst surfaces, and some of them also involve reactive and unstable gas-phase intermediates such as radicals and alkyl hydroperoxides. Online detection of these gas-phase intermediates is of great importance for fundamentally understanding reaction mechanisms of relevant heterogeneous catalytic reactions, designing structures of efficient catalysts and optimizing reactors. However, it has remained a long-time challenge due to the lack of routine characterization techniques. Herein we review recent progress on applications of photoionization mass spectrometry in online detection of reactive and unstable gas-phase intermediates in heterogeneous catalytic reactions. The development and advantages of photoionization mass spectrometry and the relevant equipment setup for heterogeneous catalysis studies are also described. Finally, a future perspective is given.[a] Dr. * (m/z = 15), C 2 H 5 * (m/z = 29) and allyl radical (CH 2 CHCH 2 * 4 5 6 7 8

show abstract

Engineering HC-SCR: Improved Low Temperature Performance through a Cascade Concept

et al. 2005

View full text Add to dashboard Cite

A catalytic after treatment system for lean HC-SCR was constructed of two different catalyst beds, e.g. of a Ag/alumina and Cu-ZSM-5 catalyst (cascade concept). The improved activity especially at low temperature range was found to be due to the synergetic effect of the two catalysts, which combines the transformation of the feed gas over Ag/alumina to such compounds that are highly reactive towards N 2 over Cu-ZSM-5. The effluent coming from the Ag/alumina bed was analysed by GC-MS along with the NO to N 2 conversion over the whole system by GC. The results obtained from the GC-MS measurements revealed that hydrocarbon used as a reducing agent is oxidised and that besides oxygenates also various N-containing hydrocarbons are formed over the Ag/Al 2 O 3 .

show abstract

Continuous reduction of NO with octane over a silver/alumina catalyst in oxygen-rich exhaust gases: combined heterogeneous and surface-mediated homogeneous reactions

Cited by 80 publications

References 19 publications

New Insights into the Active Surface Species of Silver Alumina Catalysts in the Selective Catalytic Reduction of NO

New Insights into the Active Surface Species of Silver Alumina Catalysts in the Selective Catalytic Reduction of NO

Photoionization Mass Spectrometry for Online Detection of Reactive and Unstable Gas‐Phase Intermediates in Heterogeneous Catalytic Reactions

Engineering HC-SCR: Improved Low Temperature Performance through a Cascade Concept

Contact Info

Product

Resources

About