Catalytic oxidation of ammonia on platinum

Nowak, E.J.

doi:10.1016/0009-2509(66)80003-9

Cited by 29 publications

(8 citation statements)

References 15 publications

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“…9D, shows that although some Pt is still present at the original position, the particle size has decreased considerably and a lot of Pt is transported away. Reviewing the literature, it is speculated that the loss of Pt metal is due either to transport as volatile PtO 2 in the presence of oxygen [14,[51][52][53], or by catalytic restructuring proceeded by the formation and decomposition of short-lived radical species that interact with the Pt particles [14,54].Three different sections could be identified in the used half monolith, which are represented by the electron micrographs of Fig. 11.…”

Section: Spatially Resolved Semmentioning

confidence: 99%

Catalytic partial oxidation of methane on platinum investigated by spatial reactor profiles, spatially resolved spectroscopy, and microkinetic modeling

Korup

Goldsmith

Weinberg

et al. 2013

Journal of Catalysis

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Spatially resolved profile measurements, Raman spectroscopy, electron microscopy, and microkinetic modeling have been used to study the catalytic partial oxidation of methane on Pt. The measured species profiles through Pt coated foam catalysts exhibit a two-zone structure: an abrupt change in reaction rates separates the fast exothermic oxidation chemistry at the entrance of the reactor from the slow endothermic reforming chemistry. Spatially resolved Raman spectroscopy and electron microscopy confirm that the position of the mechanistic change could be correlated with Pt transportation and formation of carbonaceous deposits blocking the majority of active Pt sites in the reforming zone. The species profiles were simulated using a pseudo-2D heterogeneous model, which includes heat and mass transport limitations, and two state-of-the-art chemical kinetic mechanisms. Although both mechanisms are in quantitative agreement with the oxygen profiles, the two mechanisms differ substantially in their predictions of the branching ratio between partial and complete oxidation, as well as surface site coverages. The experimentally observed change in reaction rates is attributed to carbon formation, which the mechanisms are unable to reproduce, since they do not include carbon–carbon coupling reactions

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Section: Spatially Resolved Semmentioning

confidence: 99%

Catalytic partial oxidation of methane on platinum investigated by spatial reactor profiles, spatially resolved spectroscopy, and microkinetic modeling

Korup

Goldsmith

Weinberg

et al. 2013

Journal of Catalysis

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“…A slow transition beginning at Ref 0.5 causes a turbulent wake to develop downstream from the cylinder Ž . Nowak, 1966 . This wake flow is fully developed at Ref100.…”

Section: Turbulencementioning

confidence: 99%

Simulating cyclohexane millisecond oxidation: Coupled chemistry and fluid dynamics

2002

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Cyclohexane partial oxidation o®er a 40-mesh Pt ᎐ 10%Rh single-gauze catalyst can produce ; 85% selecti®ity to oxygenates and olefins at 25% cyclohexane con®ersion and 100% oxygen con®ersion, with cyclohexene and 5-hexenal as the dominant prod-( ucts. A detailed 2-D model of the reactor is sol®ed using density-functional theory with ) 35 reactions among 25 species and computational fluid dynamics. Rapid quenching in the wake of the wires allows highly nonequilibrium species to be preser®ed. The simulations show that the competition between cyclohexyl and cyclohexylperoxy radicals is crucial in determining product selecti®ities. At high temperatures and low pressures, the cyclohexyl radical is fa®ored, leading to high selecti®ities to cyclohexene. At lower temperatures or high pressures, cyclohexylperoxy radicals are fa®ored, allowing the formation of parent oxygenates to dominate. Numerical simulations suggest ways to tune reactor operation for desired product distributions and allow the in®estigation of dangerous or costly operating conditions, such as high pressure.2 3 technology is presumably that separation of the product stream would be energy-intensive.The millisecond single-gauze reactor successfully couples catalytic and gas-phase chemistry to produce a highly unsta-

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“…Ammonia is produced at industrial scale for use in fertilizer and chemical synthesis, , but could become a promising carbon-free fuel if its selective and efficient catalytic oxidation to nitrogen can be achieved. Catalysts sufficiently active and stable for fuel cell applications are still needed. − Platinum-based materials, perhaps the current best candidates, − suffer from low current densities due to side reactions that can result at moderate applied bias.…”

mentioning

confidence: 99%

Enhanced Ammonia Oxidation Catalysis by a Low-Spin Iron Complex Featuring Cis Coordination Sites

Zott

Peters

2021

J. Am. Chem. Soc.

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The goal of using ammonia as a solar fuel motivates the development of selective ammonia oxidation (AO) catalysts for fuel cell applications. Herein, we describe Fe-mediated AO electrocatalysis with [(bpyPy 2 Me)Fe(MeCN) 2 ] 2+ , exhibiting the highest turnover number (TON) reported to date for a molecular system. To improve on our recent report of a related iron AO electrocatalyst, [(TPA)Fe(MeCN) 2 ] 2+ (TON of 16), the present [(bpyPy 2 Me)Fe(MeCN) 2 ] 2+ system (TON of 149) features a stronger-field, more rigid auxiliary ligand that maintains cis-labile sites and a dominant low-spin population at the Fe(II) state. The latter is posited to mitigate demetalation and hence catalyst degradation by the presence of a large excess of ammonia under the catalytic conditions. Additionally, the [(bpyPy 2 Me)Fe(MeCN) 2 ] 2+ system exhibits a substantially faster AO rate (ca. 50×) at significantly lower (∼250 mV) applied bias compared to [(TPA)Fe(MeCN) 2 ] 2+ . Electrochemical data are consistent with an initial E 1 net H-atom abstraction step that furnishes the cis amide/ammine complex [(bpyPy 2 Me)Fe(NH 2 )(NH 3 )] 2+ , followed by the onset of catalysis at E 2 . Theoretical calculations suggest the possibility of N−N bond formation via multiple thermodynamically plausible pathways, including both reductive elimination and ammonia nucleophilic attack. In sum, this study underscores that Fe, an earthabundant metal, is a promising metal for further development in metal-mediated AO catalysis by molecular systems.

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Catalytic oxidation of ammonia on platinum

Cited by 29 publications

References 15 publications

Catalytic partial oxidation of methane on platinum investigated by spatial reactor profiles, spatially resolved spectroscopy, and microkinetic modeling

Catalytic partial oxidation of methane on platinum investigated by spatial reactor profiles, spatially resolved spectroscopy, and microkinetic modeling

Simulating cyclohexane millisecond oxidation: Coupled chemistry and fluid dynamics

Enhanced Ammonia Oxidation Catalysis by a Low-Spin Iron Complex Featuring Cis Coordination Sites

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