Mechanistic studies of NOx reduction reactions under oxidative atmosphere on alumina supported 1wt% Pt and 1wt% Pt–0.5wt% Zn catalysts (Part I)

Garin, F.; Girard, P.; Ringler, Sandrine; Maire, G.; Davias, N.

doi:10.1016/s0926-3373(98)00107-6

Cited by 23 publications

(13 citation statements)

References 21 publications

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“…At low temperature range, propene and 15 NO disappearance reactions have the same apparent activation energy value while at high temperature range, propane and 18 O 2 consumption reactions have similar activation energy value. Such a behaviour is in accordance with the fact that, at low temperature, the sticking coefficient of NO (σ NO ) is higher than the oxygen one (σ O 2 ) [91,92], and when the temperature increases, σ NO decreases and σ O 2 increases which leads, in fine, to a complete oxidation of the propane with 18 [89,90].…”

Section: Resultssupporting

confidence: 82%

“…Furthermore, when performing experiments, with labelled compounds 18 O 2 and 15 NO with propene as reductant, in the temperature range 150-250 • C we noticed, from Arrhenius plots determined from initial rates, the presence of two temperature domains 150-200 and 200-250 • C [89,90]. At low temperature range, propene and 15 NO disappearance reactions have the same apparent activation energy value while at high temperature range, propane and 18 O 2 consumption reactions have similar activation energy value.…”

Section: Resultsmentioning

confidence: 91%

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Environmental catalysis

Garin

2004

Catalysis Today

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This review article was constructed around the first Algerian-French congress aimed on emerging materials which was held at Tamanrasset by the end of February 2003. The aim of this review is to point out that a lot of work has been done in heterogeneous catalysis to better understand the active sites responsible for the catalytic reactivity. Most of these researches were performed under reducible atmosphere, on metallic catalysts, to improve our knowledge about hydrocarbon reforming catalysts. Starting from this base which was recalled through various classes of important studies such as: (i) the dilution of the active sites, (ii) the use of bimetallics, (iii) the use of well-crystallised surfaces and (iv) the influence of the metal-support interactions; a development and an opening is made on the three-way catalysis and the DeNO x reactions. The objectives being to point out the very important influence of the experimental conditions and of the gas phase compositions which may induce very strong surface modifications of the initial metallic aggregates. Moreover, it will depend on the reactions, i.e. isomerisation, oxidation, reduction where the active site may also be composed of, in addition to the metallic crystallites, the participation of the oxygen of the support.A tentative for a general interpretation of the observed results is given by the use of the variations of the local density of states and of the "d" band centre energy.

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Section: Resultssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 91%

Environmental catalysis

Garin

2004

Catalysis Today

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“…Considering these facts, it can be assumed that NO and C 3 H 6 are involved in the generation of partially oxidised hydrocarbon species through a slow reaction. This species may have an important role on the reaction, as has been put forward by other authors [6,7,[25][26][27][28] From these results, it could be concluded that adsorption of hydrocarbon on Pt is followed by a reaction in which NOads and C3H6ads would participate to form partially oxidized hydrocarbon species. In these conditions, the surface is covered by these species that need the action of oxygen gas to react completely to CO 2 and liberate Pt free sites for the reaction to continue.…”

Section: Transient Analysis Experiments Below T Max (200ºc)supporting

confidence: 57%

The selective reduction of NO with propene on Pt-beta catalyst: A transient study

Cortés

Illán-Gómez

Lecea

2007

Applied Catalysis B: Environmental

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The mechanism of the NO/C3H6/O2 reaction has been studied on a Ptbeta catalyst using transient analysis techniques. This work has been designed to provide answers to the volcano-type activity behaviour of the catalytic system, for that reason, steady state transient switch (C 3 H 6 /NO/O 2 → C 3 H 6 /Ar/O 2 , C 3 H 6 /Ar/O 2 → C 3 H 6 /NO/O 2 ; C 3 H 6 /NO/O 2 → Ar/NO/O 2 , Ar/NO/O 2 → C 3 H 6 /NO/O 2 ; C 3 H 6 /NO/O 2 → C 3 H 6 /NO/Ar and C 3 H 6 /NO/Ar → C 3 H 6 /NO/O 2 ) and Thermal Programmed Desorption (TPD) experiments were conducted below and above the temperature of the maximum activity (Tmax). Below Tmax, at 200ºC, a high proportion of adsorbed hydrocarbon exists on the catalyst surface. There exists a direct competition between NO and O 2 for Pt free sites which is very much in favour of NO, and therefore NO reduction selectively takes place over hydrocarbon combustion. NO and C 3 H 6 are involved in the generation of partially oxidised hydrocarbon species. O 2 is essential for the oxidation of these intermediates closing the catalytic cycle. NO 2 is not observed in the gas phase. Above T max , at 230ºC, C 3 H 6ads coverage is negligible and the surface is mainly covered by O ads produced by the dissociative adsorption of O 2 . NO 2 is observed in gas phase and carbon deposits are formed at the catalyst surface. From these results, the state of Ptbeta catalyst at T max is inferred. The reaction proceeds through the formation of partially oxidised active intermediates (C x H y O z N w ) from C 3 H 6ads and NO ads . The combustion of the intermediates with O2(g) frees the Pt active sites so the reaction can continue.Temperature has a positive effect on the surface reaction producing active intermediates. On the contrary, formation of NO ads and C 3 H 6·ads are not favoured by an increase in temperature. Temperature has also a positive effect on the dissociation of O 2 to form O ads , consequently, the formation of NO 2 is favoured by temperature through the oxygen dissociation. NO2 is very reactive and produces the propene combustion without NO reduction. These facts will determine the maximum concentration of active intermediates and consequently the maximum of activity.Key words: NOx-SCR mechanism, propene, Pt-beta catalyst, transient experiments. Page 2 of 34A c c e p t e d M a n u s c r i p t 3 IntroductionNumerous papers deal with the study of the mechanism of NO x reduction by hydrocarbon in the presence of excess oxygen on platinum based catalysts. However there is no evidence that allows defining a single reaction path. Pt/Al 2 O 3 and Pt/SiO 2 catalysts have been the most studied catalytic systems and therefore, those about which more is known. One of the conclusions arising from a detailed study of the literature is the different reaction paths for different hydrocarbons, as it appears when comparing propane and propene [1]. The Pt oxidation state is a key issue in determining the reaction mechanism and this seems to be related to the different nature of the hydrocarbon-metal bond [2][...

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“…For instance, Pitchon et al observed NO production at low temperatures for NO 2 HC-SCR with PtSiO 2 catalyst, which could be pointing out that NO 2 is previously reduced to NO before N 2 formation [52]. The oxidation of NO to NO 2 in the absence of a reductant agent could suggest that the formation of adsorbed NO 2 , which would latter interact with the adsorbed hydrocarbon, could be likely to occur on this catalytic system, although the system response in the presence of SO 2 , as shown in Figure 12.b and c, seems to neglect such a possibility.…”

Section: Ssit-ptmentioning

confidence: 99%

Electrospinning of silica sub-microtubes mats with platinum nanoparticles for NO catalytic reduction

Ruiz-Rosas¹,

Rosas²,

Loscertales³

et al. 2014

Applied Catalysis B: Environmental

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Silica sub-microtubes loaded with platinum nanoparticles have been prepared in flexible non-woven mats using co-axial electrosppining technique. A partially gelated sol made from tetraethyl orthosilicate was used as the silica precursor, and oil was used as the sacrificial template for the hollow channel generation. Platinum has been supported on the wall of the tubes just adding the metallic precursor to the sol-gel, thus obtaining the supported catalyst by one-pot method. The silica tubes have a high aspect ratio with external/internal diameters of 400/200 nm and well-dispersed platinum nanoparticles of around 2 nm. This catalyst showed a high NO conversion with very high selectivity to N 2 at mild conditions in the presence of excess oxygen when using C 3 H 6 as reducing agent. This relevant result reveals the potential of this technique to produce nanostructured catalysts onto easy to handle conformations.Keywords: coaxial electrospinning, silica nanotubes, platinum nanoparticles, NOx SCR. Graphical AbstractHighlights  Non-woven mats of platinum-loaded silica nanotubes were obtained by co-axial electrospinning in one-pot procedure. By this technique, high dispersed Pt nanoparticles can be easily deposited on the walls of the silica nanotubes. Pt-loaded silica nanotube non-woven mats show high activity for low temperature NOx SCR with propylene in the presence of excess oxygen and outstanding N 2 selectivity, at the studied operation conditions.

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Mechanistic studies of NOx reduction reactions under oxidative atmosphere on alumina supported 1wt% Pt and 1wt% Pt–0.5wt% Zn catalysts (Part I)

Cited by 23 publications

References 21 publications

Environmental catalysis

Environmental catalysis

The selective reduction of NO with propene on Pt-beta catalyst: A transient study

Electrospinning of silica sub-microtubes mats with platinum nanoparticles for NO catalytic reduction

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