A fast transient kinetic study of the effect of H2 on the selective catalytic reduction of NOx with octane using isotopically labelled 15NO

Breen, John; Burch, Robbie; Hardacre, Christopher; Hill, Christopher J.; Rioche, C.

doi:10.1016/j.jcat.2006.11.017

Cited by 57 publications

(41 citation statements)

References 25 publications

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“…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%

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

et al. 2010

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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.

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Section: Resultsmentioning

confidence: 82%

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

et al. 2010

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“…To increase the rate of NO x conversion, basically, the hydrogen must accelerate the rate(s) of the slow step(s) in the reaction of HC-SCR, while the slow step(s) are likely to vary depending on the reaction temperature and feed conditions. 212 We were the first to report the pronounced promotional effect of H 2 on NO x reduction by ethanol over Ag/Al 2 O 3 even in the presence of water vapor. 213 Evidence provided by in situ DRIFTS revealed that the presence of H 2 enhanced the formation of enolic species during the partial oxidation of ethanol over Ag/Al 2 O 3 at low temperatures.…”

Section: Reactivity Of Intermediates Originating From Partial Oxidatimentioning

confidence: 88%

Environmentally-benign catalysts for the selective catalytic reduction of NO_xfrom diesel engines: structure–activity relationship and reaction mechanism aspects

2014

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Selective catalytic reduction of NO x using NH 3 or hydrocarbons (NH 3 -SCR or HC-SCR) in oxygen-rich exhaust from diesel engines remains a major challenge in environmental catalysis. The development of highly efficient, stable and environmentally-benign catalysts for SCR processes is very important for practical use. In this feature article, the structure-activity relationship of vanadium-free catalysts in the NH 3 -SCR reaction is discussed in detail, including Fe-, Ce-based oxide catalysts and Fe-, Cu-based zeolite catalysts, which is beneficial for catalyst redesign and activity improvement. Based on our research, a comprehensive mechanism contributing to the performance of Ag/Al 2 O 3 in HC-SCR is provided, giving a clue to the design of a catalytic system with high efficiency.

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“…However, in most investigations of the hydrogen effect, relatively high H 2 concentrations have been used (e.g., H 2 concentration of 1000-4000 ppm [3], 5000 ppm [4], 500-7200 ppm [5,6], 5000 ppm: 1% [7], 1% [8,9]). Therefore, experimental data on Ag/Al 2 O 3 performance and a possible reaction mechanism within a practical range of H 2 concentrations are scarce.…”

Section: Introductionmentioning

confidence: 99%

Two Reaction Pathways in the Selective Catalytic Reduction of NO x by C6H14 Over Ag–Al2O3 with H2 Co-Feeding

et al. 2009

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The NO x reduction with n-C 6 H 14 was studied over a 3% Ag/Al 2 O 3 catalyst in the presence of hydrogen. The catalyst performance was evaluated by varying the H 2 concentration from 0 to 1600 ppm and by comparing the results with blank runs in which an empty reactor with no catalyst was used. Two distinct reaction pathways were revealed: one at low-temperature (T react \ 370°C) and another one at high-temperature (T react [ 370-390°C). Co-feeding of H 2 promotes the reaction within the 150-360°C interval. The high-temperature pathway (T react [ 370-390°C) seems to be almost independent of hydrogen co-feeding. The homogeneous gas-phase NO x oxidation initiated by NO presumably plays an important role in this high-temperature pathway.

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A fast transient kinetic study of the effect of H2 on the selective catalytic reduction of NOx with octane using isotopically labelled 15NO

Cited by 57 publications

References 25 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

Environmentally-benign catalysts for the selective catalytic reduction of NO_xfrom diesel engines: structure–activity relationship and reaction mechanism aspects

Two Reaction Pathways in the Selective Catalytic Reduction of NO x by C6H14 Over Ag–Al2O3 with H2 Co-Feeding

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A fast transient kinetic study of the effect of H2 on the selective catalytic reduction of NOx with octane using isotopically labelled 15NO

Cited by 57 publications

References 25 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

Environmentally-benign catalysts for the selective catalytic reduction of NOxfrom diesel engines: structure–activity relationship and reaction mechanism aspects

Two Reaction Pathways in the Selective Catalytic Reduction of NO x by C6H14 Over Ag–Al2O3 with H2 Co-Feeding

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Environmentally-benign catalysts for the selective catalytic reduction of NO_xfrom diesel engines: structure–activity relationship and reaction mechanism aspects