Kinetics of the bimolecular reaction NO+H2 on Pt

Papapolymerou, G.; Botis, A. G.; Papargyris, Athanasios D.; Spiliotis, X.

doi:10.1016/0304-5102(93)85060-7

Cited by 6 publications

(9 citation statements)

References 14 publications

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“…(10) is in good correspondence with the value of 62.8 kJ/mol given by Otto and Yao for the reduction of NO by H 2 over Pt/g-Al 2 O 3 in an excess of NO [17]. The value of the heat of adsorption of H 2 is in good agreement with other reported values on platinum: 46 kJ/mol [18], 68.1 kJ/mol [19] and 51.8 kJ/mol [20]. Values of desorption energies of O 2 found in the literature (230 kJ/mol [21]) are substantially higher than the heat of adsorption found in this study.…”

Section: Kinetics Of the No/h 2 /O 2 Reactionsupporting

confidence: 90%

Kinetics and mechanism of the reduction of nitric oxides by H2 under lean-burn conditions on a Pt–Mo–Co/α-Al2O3 catalyst

Frank

Emig

Renken

1998

Applied Catalysis B: Environmental

128

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The kinetics and the mechanism of the selective reduction of nitric oxides (NO x ) by hydrogen is studied on a trimetallic Pt± Mo±Co/-Al 2 O 3 catalyst under oxidising conditions. This system is interesting in view of an exhaust gas control of power plants or lean-burn cars. It can be shown that the NO dissociation is the crucial step, dominating the overall reaction behaviour and that it depends on temperature and on the partial pressure of H 2 . With increasing temperatures the reaction reveals an autocatalytic behaviour resulting in bistability and hysteresis. At higher temperatures, where no bistability is found, the NO/H 2 as well as the competing O 2 /H 2 reaction occur only above a certain critical partial pressure of H 2 . The kinetics of the NO/H 2 / O 2 reaction are established using a modi®ed Langmuir±Hinshelwood model (T1428C±1608C, y O2 >4%) which takes into account the critical H 2 partial pressure. The model describes the experimental data within AE15%. The determined activation energies are: 63 kJ/mol for the NO x consumption, 77 and 45 kJ/mol for the N 2 and N 2 O formation, respectively, and 130 kJ/ mol for the O 2 /H 2 reaction. Adsorption enthalpies are determined to À59 kJ/mol for the adsorption of H 2 , À77 kJ/mol for the adsorption of NO and À97 kJ/mol for the adsorption of O 2 . An interesting feature of the reaction is the enhancement of the NO/H 2 reaction by oxygen for low partial pressures of O 2 . This appears to be the ®rst study where a promoting effect of oxygen for the NO/H 2 reaction is found on a platinum supported catalyst. #

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Section: Kinetics Of the No/h 2 /O 2 Reactionsupporting

confidence: 90%

Kinetics and mechanism of the reduction of nitric oxides by H2 under lean-burn conditions on a Pt–Mo–Co/α-Al2O3 catalyst

Frank

Emig

Renken

1998

Applied Catalysis B: Environmental

128

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“…Zemlyanov et al 17 observed an NH intermediate during the NO + H 2 reaction on Pt(100) by EELS. Prasad and Gland 18 explained the formation of diimide N 2 H 2 during the decomposition of NH 3 and N 2 H 4 on Rh foil by the coupling of NH species on the surface. NH x intermediates were also observed in NH 3 and N 2 H 4 decomposition studies on Ni, 19,20 Pt, 21 Rh, 22,23 and Ru.…”

Section: Introductionmentioning

confidence: 99%

“…Prasad and Gland 18 explained the formation of diimide N 2 H 2 during the decomposition of NH 3 and N 2 H 4 on Rh foil by the coupling of NH species on the surface. NH x intermediates were also observed in NH 3 and N 2 H 4 decomposition studies on Ni, 19,20 Pt, 21 Rh, 22,23 and Ru. 24 Recently, the NO + H 2 reaction regained interest in the context of chemical waves and oscillations that develop under specific reaction conditions on Rh single-crystal planes.…”

Section: Introductionmentioning

confidence: 99%

“…Kinetic studies of the NO + H 2 reaction have been performed on Pt foil, 3 Rh foil, 4 Pt/Rh single crystals, 5,6 Rh/SiO 2 , 7 and Rh/ Al 2 O 3 . 8 These studies have shown that the reactivity of atomic nitrogen, which is formed by the dissociation of NO, plays a key role in the selectivity issue of the NO + H 2 reaction.…”

Section: Introductionmentioning

confidence: 99%

“…8 These studies have shown that the reactivity of atomic nitrogen, which is formed by the dissociation of NO, plays a key role in the selectivity issue of the NO + H 2 reaction. Whereas reactions such as the NO dissociation [9][10][11] and recombination of atomic nitrogen to N 2 12, 13 have been studied extensively, the microscopic mechanisms of N 2 O and NH 3 formation are still unknown. NH 3 formation is commonly described by the stepwise hydrogenation of atomic nitrogen.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and Mechanism of NH₃ Formation by the Hydrogenation of Atomic Nitrogen on Rh(111)

1997

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The reaction between atomic nitrogen and H 2 has been studied in order to elucidate the mechanism of NH 3 formation on Rh(111). Atomic nitrogen layers of 0.10 monolayer (ML) coverage were obtained by adsorbing NO at 120 K and selectively removing the atomic oxygen from dissociated NO by reaction with H 2 at 375 K. The rate of NH 3 formation is first order in the atomic nitrogen coverage and linearly proportional to the H 2 pressure below 5 × 10 -7 mbar. Static secondary ion mass spectrometry (SSIMS) indicates that N and NH 2 are the predominant reaction intermediates, while small amounts of NH 3 are also detected. The NH 2 surface coverage increases with increasing H 2 pressure. The presence of NH 2 is also indicated by the appearance of a reaction-limited H 2 desorption state in temperature-programmed desorption (TPD) spectra. The hydrogenation of NH 2 to NH 3 is expected to be the rate-determining step in the NH 3 formation. From the temperature dependence of the NH 3 formation rate an effective activation energy of 40 kJ/mol was determined, which could be translated into an activation energy of 76 kJ/mol for the hydrogenation from NH 2 to NH 3 .

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Decomposition of no on Pd and Ir. Comparison with Pt and Rh

Papapolymerou

1996

React Kinet Catal Lett

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Kinetics of the bimolecular reaction NO+H2 on Pt

Cited by 6 publications

References 14 publications

Kinetics and mechanism of the reduction of nitric oxides by H2 under lean-burn conditions on a Pt–Mo–Co/α-Al2O3 catalyst

Kinetics and mechanism of the reduction of nitric oxides by H2 under lean-burn conditions on a Pt–Mo–Co/α-Al2O3 catalyst

Kinetics and Mechanism of NH₃ Formation by the Hydrogenation of Atomic Nitrogen on Rh(111)

Decomposition of no on Pd and Ir. Comparison with Pt and Rh

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Kinetics of the bimolecular reaction NO+H2 on Pt

Cited by 6 publications

References 14 publications

Kinetics and mechanism of the reduction of nitric oxides by H2 under lean-burn conditions on a Pt–Mo–Co/α-Al2O3 catalyst

Kinetics and mechanism of the reduction of nitric oxides by H2 under lean-burn conditions on a Pt–Mo–Co/α-Al2O3 catalyst

Kinetics and Mechanism of NH3 Formation by the Hydrogenation of Atomic Nitrogen on Rh(111)

Decomposition of no on Pd and Ir. Comparison with Pt and Rh

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Kinetics and Mechanism of NH₃ Formation by the Hydrogenation of Atomic Nitrogen on Rh(111)