Nitrogen-15 and oxygen-18 kinetic isotope effects in the catalytic decomposition of N2O over MgO

Žemva, Peter; Lesar, Antonija; Senegačnik, Marjan; Kobal, I.

doi:10.1039/b002189j

Cited by 12 publications

(18 citation statements)

References 47 publications

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“…The present results confirm the findings already reported in the literature, and in particular that the oxygen abstraction is the rate limiting step. The computed barrier, 1.37 eV for terrace and 1.34 eV for edge sites, is very close to that determined in recent kinetic isotope effects experiments, 1.3 eV [6]. In this respect, it does not seem that the MgO low-coordinated sites play a special role.…”

Section: Discussionsupporting

confidence: 77%

“…The TS resembles that computed by other authors [7][8][9]. The barrier is somewhat lower than that computed in other studies, but quite close to the most recent experimental estimate of 1.3 eV [6]. Reaction (1) is very weakly exothermic on a MgO terrace, with a gain of 0.025 eV per N 2 O molecule, while is strongly exothermic on an edge, where the energy lowering is of 0.55 eV per N 2 O molecule, see Fig.…”

Section: Pure Mgosupporting

confidence: 86%

“…More recently a kinetic isotope effect study has shown that the reaction is of first order in N 2 O with an apparent activation energy of 1.30 eV [6]. The reaction mechanism and the barriers involved have been investigated in three theoretical ab initio studies.…”

Section: Introductionmentioning

confidence: 99%

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Catalytic dissociation of N2O on pure and Ni-doped MgO surfaces

2006

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Section: Discussionsupporting

confidence: 77%

Section: Pure Mgosupporting

confidence: 86%

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Catalytic dissociation of N2O on pure and Ni-doped MgO surfaces

2006

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“…Although there is a great deal of theoretical and experimental data about the MgO surface, − less information is available for CaO and SrO. − An overall agreement has been reached that the oxygen abstraction takes place at an O 2– (surf) site, leaving a peroxide intermediate at the surface. , Since all the considered oxides have the same surface structure, one would expect decomposition of N 2 O to be correlated with the lattice constant and therefore the basicity sequence. Actually, previous studies on N 2 O decomposition have shown that CaO is more active than magnesia; however, SrO and BaO (despite their higher basicity) do not follow the trend, being distinctly less reactive. , …”

Section: Introductionmentioning

confidence: 99%

DFT Modeling of Reaction Mechanism and Ab Initio Microkinetics of Catalytic N₂O Decomposition over Alkaline Earth Oxides: From Molecular Orbital Picture Account to Simulation of Transient and Stationary Rate Profiles

et al. 2013

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A comprehensive molecular modeling of the reaction mechanism, complemented by ab initio microkinetic studies of the catalytic decomposition of N 2 O on a series of the alkaline earth oxides (MgO, CaO, and SrO), was performed. The DFT level of theory was used to study the intimate mechanism of conceivable elementary steps of the deN 2 O reaction over the terrace sites of the most stable (100) planes. The principal mechanistic events were thoroughly analyzed in terms of the frontier molecular orbital picture, and a multiple role of the anionic redox active centers constituted by surface O 2− (surf) ions was revealed. The harmonic transition state theory along with the calculated free enthalpies of activation were used to model the reaction progress with the elementary step resolution in pulse (transient) and steady state regimes. For modeling the surface diffusion and recombination of the reaction key intermediates (peroxy groups), a Monte Carlo approach was applied to rationalize dioxygen formation along the static and dynamic routes. The developed kinetic scheme was able to reproduce the results of temperatureprogrammed surface reaction (TPSR) and isothermal steady state experiments with high accuracy without fitting any parameters. On the basis of obtained results, a complete molecular mechanistic description of the deN 2 O reaction was proposed, resolving definitely the dependence of the particular elementary steps on the strength of anionic redox centers and their Lewis basicity.

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“…A number of chemical and physical processes can be influenced by isotope effects, − but this laboratory activity uses the shakers to illustrate how water isotopic distributions can be used to estimate how the earth’s temperature has varied over time. In a simplified view of the water cycle, liquid water in the ocean evaporates into the gas phase and is blown about by the wind.…”

Section: Discussionmentioning

confidence: 99%

Using Beads and Divided Containers To Study Kinetic and Equilibrium Isotope Effects in the Laboratory and in the Classroom

et al. 2017

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The purpose of this laboratory experiment is to study fundamental concepts of kinetics and equilibria and the isotope effects associated with both of these concepts. The concepts of isotopes in introductory and general chemistry courses are typically used within the contexts of atomic weights and radioactivity. Kinetic and equilibrium isotope effects are typically covered in upper-level courses in the chemistry curriculum, but the concepts behind these isotope effects are also relevant to introductory chemistry. Beads (specifically "airsoft" pellets) of the same size but with two different masses can be used to represent isotopes of two different masses in classroom activities. Plastic Petri dishes with dividers can be modified so that the chambers can represent different states of matter or different chemical species. When the Petri dishes containing a number of beads of each mass are shaken, the beads will be distributed among the chambers in a manner similar to isotope distributions in matter. The bead/Petri dish shakers have been used as a chemistry demonstration and as a chemistry laboratory activity. Additionally, LEGO-based models containing chambers separated by dividers can be used to demonstrate the phenomena of kinetics and equilibria. The laboratory experiments can be performed in one laboratory period and are designed to touch on a variety of topics relevant for general chemistry students, although the lab could also be easily used for students with more or less advanced backgrounds.

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Nitrogen-15 and oxygen-18 kinetic isotope effects in the catalytic decomposition of N2O over MgO

Cited by 12 publications

References 47 publications

Catalytic dissociation of N2O on pure and Ni-doped MgO surfaces

Catalytic dissociation of N2O on pure and Ni-doped MgO surfaces

DFT Modeling of Reaction Mechanism and Ab Initio Microkinetics of Catalytic N₂O Decomposition over Alkaline Earth Oxides: From Molecular Orbital Picture Account to Simulation of Transient and Stationary Rate Profiles

Using Beads and Divided Containers To Study Kinetic and Equilibrium Isotope Effects in the Laboratory and in the Classroom

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Nitrogen-15 and oxygen-18 kinetic isotope effects in the catalytic decomposition of N2O over MgO

Cited by 12 publications

References 47 publications

Catalytic dissociation of N2O on pure and Ni-doped MgO surfaces

Catalytic dissociation of N2O on pure and Ni-doped MgO surfaces

DFT Modeling of Reaction Mechanism and Ab Initio Microkinetics of Catalytic N2O Decomposition over Alkaline Earth Oxides: From Molecular Orbital Picture Account to Simulation of Transient and Stationary Rate Profiles

Using Beads and Divided Containers To Study Kinetic and Equilibrium Isotope Effects in the Laboratory and in the Classroom

Contact Info

Product

Resources

About

DFT Modeling of Reaction Mechanism and Ab Initio Microkinetics of Catalytic N₂O Decomposition over Alkaline Earth Oxides: From Molecular Orbital Picture Account to Simulation of Transient and Stationary Rate Profiles