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Ammonia

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William I. F. David – One of the best experts on this subject based on the ideXlab platform.

  • neutron diffraction and gravimetric study of the manganese nitriding reaction under Ammonia decomposition conditions
    Physical Chemistry Chemical Physics, 2017
    Co-Authors: Thomas J. Wood, Joshua W Makepeace, William I. F. David

    Abstract:

    Ammonia decomposition over iron catalysts is known to be affected by whether the iron exists in elemental form or as a nitride. In situ neutron diffraction studies with simultaneous gravimetric analysis were performed on the nitriding and denitriding reactions of iron under Ammonia decomposition conditions. The gravimetric analysis agrees well with the Rietveld analysis of the neutron diffraction data, both of which confirm that the form of the iron catalyst is strongly dependent on Ammonia decomposition conditions. Use of Ammonia with natural isotopic abundance as the nitriding agent means that the incoherent neutron scattering of any hydrogen within the gases present is able to be correlated to how much Ammonia had decomposed. This novel analysis reveals that the nitriding of the iron occurred at exactly the same temperature as Ammonia decomposition started. The iron nitriding and denitriding reactions are shown to be related to steps that take place during Ammonia decomposition and the optimum conditions for Ammonia decomposition over iron catalysts are discussed.

  • isotopic studies of the Ammonia decomposition reaction mediated by sodium amide
    Physical Chemistry Chemical Physics, 2015
    Co-Authors: Thomas J. Wood, Joshua W Makepeace, William I. F. David, Hazel M A Hunter, Martin O Jones

    Abstract:

    We demonstrate that the Ammonia decomposition reaction catalysed by sodium amide proceeds under a different mechanism to Ammonia decomposition over transition metal catalysts. Isotopic variants of Ammonia and sodium amide reveal a significant kinetic isotope effect in contrast to the nickel-catalysed reaction where there is no such effect. The bulk composition of the catalyst is also shown to affect the kinetics of the Ammonia decomposition reaction.

  • Ammonia decomposition catalysis using non stoichiometric lithium imide
    Chemical Science, 2015
    Co-Authors: Joshua W Makepeace, William I. F. David, Thomas J. Wood, Hazel M A Hunter, Martin O Jones

    Abstract:

    We demonstrate that non-stoichiometric lithium imide is a highly active catalyst for the production of high-purity hydrogen from Ammonia, with superior Ammonia decomposition activity to a number of other catalyst materials. Neutron powder diffraction measurements reveal that the catalyst deviates from pure imide stoichiometry under Ammonia flow, with active catalytic behaviour observed across a range of stoichiometry values near the imide. These measurements also show that hydrogen from the Ammonia is exchanged with, and incorporated into, the bulk catalyst material, in a significant departure from existing Ammonia decomposition catalysts. The efficacy of the lithium imide–amide system not only represents a more promising catalyst system, but also broadens the range of candidates for amide-based Ammonia decomposition to include those that form imides.

Sofia Calero – One of the best experts on this subject based on the ideXlab platform.

  • role of hydrogen bonding in the capture and storage of Ammonia in zeolites
    Chemical Engineering Journal, 2020
    Co-Authors: I Matitomartos, Ana Martincalvo, Conchi O Ania, J B Parra, Jose Manuel Vicentluna, Sofia Calero

    Abstract:

    Abstract Ammonia is an important chemical compound used in a wide range of applications. This makes its capture, purification and recovery necessary. We combine experimental and molecular simulation techniques to identify the molecular mechanisms ruling the adsorption of Ammonia in pure and high silica zeolites. To reproduce accurately the interaction between Ammonia and the zeolites the development of a transferable set of Lennard-Jones parameters was needed. Adsorption isotherms were measured and also calculated using the new set of parameters for several commercial pure silica zeolites, including MFI, FAU, and LTA topologies. We found an anomalous behavior of the adsorption isotherm of Ammonia in MFI, which can be explained through a monoclinic to orthorhombic structural phase transition. We also found that low concentration of extra-framework cations favors the adsorption of Ammonia in these high silica zeolites. Using radial distribution functions and hydrogen bond analyses we identified Ammonia clusterization as the key mechanism involved in the adsorption. Based on it, hydrophobic zeolites with large pores could be used for Ammonia sequestration with lower cost than the currently used techniques.

Joshua W Makepeace – One of the best experts on this subject based on the ideXlab platform.

  • neutron diffraction and gravimetric study of the manganese nitriding reaction under Ammonia decomposition conditions
    Physical Chemistry Chemical Physics, 2017
    Co-Authors: Thomas J. Wood, Joshua W Makepeace, William I. F. David

    Abstract:

    Ammonia decomposition over iron catalysts is known to be affected by whether the iron exists in elemental form or as a nitride. In situ neutron diffraction studies with simultaneous gravimetric analysis were performed on the nitriding and denitriding reactions of iron under Ammonia decomposition conditions. The gravimetric analysis agrees well with the Rietveld analysis of the neutron diffraction data, both of which confirm that the form of the iron catalyst is strongly dependent on Ammonia decomposition conditions. Use of Ammonia with natural isotopic abundance as the nitriding agent means that the incoherent neutron scattering of any hydrogen within the gases present is able to be correlated to how much Ammonia had decomposed. This novel analysis reveals that the nitriding of the iron occurred at exactly the same temperature as Ammonia decomposition started. The iron nitriding and denitriding reactions are shown to be related to steps that take place during Ammonia decomposition and the optimum conditions for Ammonia decomposition over iron catalysts are discussed.

  • isotopic studies of the Ammonia decomposition reaction mediated by sodium amide
    Physical Chemistry Chemical Physics, 2015
    Co-Authors: Thomas J. Wood, Joshua W Makepeace, William I. F. David, Hazel M A Hunter, Martin O Jones

    Abstract:

    We demonstrate that the Ammonia decomposition reaction catalysed by sodium amide proceeds under a different mechanism to Ammonia decomposition over transition metal catalysts. Isotopic variants of Ammonia and sodium amide reveal a significant kinetic isotope effect in contrast to the nickel-catalysed reaction where there is no such effect. The bulk composition of the catalyst is also shown to affect the kinetics of the Ammonia decomposition reaction.

  • Ammonia decomposition catalysis using non stoichiometric lithium imide
    Chemical Science, 2015
    Co-Authors: Joshua W Makepeace, William I. F. David, Thomas J. Wood, Hazel M A Hunter, Martin O Jones

    Abstract:

    We demonstrate that non-stoichiometric lithium imide is a highly active catalyst for the production of high-purity hydrogen from Ammonia, with superior Ammonia decomposition activity to a number of other catalyst materials. Neutron powder diffraction measurements reveal that the catalyst deviates from pure imide stoichiometry under Ammonia flow, with active catalytic behaviour observed across a range of stoichiometry values near the imide. These measurements also show that hydrogen from the Ammonia is exchanged with, and incorporated into, the bulk catalyst material, in a significant departure from existing Ammonia decomposition catalysts. The efficacy of the lithium imide–amide system not only represents a more promising catalyst system, but also broadens the range of candidates for amide-based Ammonia decomposition to include those that form imides.