Incorporation of ammonium fluoride into clathrate hydrate lattices and its significance in inhibiting hydrate formation

Park, Seongmin; Lim, Dongwook; Seo, Yongwon; Lee, Huen

doi:10.1039/c5cc01705j

Cited by 15 publications

(14 citation statements)

References 40 publications

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“…13,14 Here we test the response of water's phase diagram with respect to a specific disturbance, the addition of small amounts of ammonium fluoride (NH4F). While NH4F is well-known to mix with the 'ordinary' ice Ih across a large composition range 15,16 and has been shown to incorporate into clathrate hydrates, 17,18 the mixing of NH4F with high-pressure phases of ice has not been previously investigated. The local hydrogen-bonding environment of ice is in principle well-adapted for incorporating NH4 + and Fions in terms of the length, strength and number of hydrogen bonds.…”

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confidence: 99%

Doping-induced disappearance of ice II from water’s phase diagram

et al. 2018

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confidence: 99%

Doping-induced disappearance of ice II from water’s phase diagram

et al. 2018

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“…From the diffraction analyses we demonstrated that methanol can be aguest molecule for sI, [9] sII, and sH H 2 O/NH 4 Fc lathrates.F or further confirmation we have also investigated solid-state 13 CNMR spectra of methanol for each of the H 2 O/NH 4 F clathrate structural types,s I, sII, and sH. Figure 4s hows the cross-polarized (CP) spectra at 183 Ki nt he chemical shift region of the methanol resonance.S ince the spectra were obtained by cross-polarization from 1 Hthey should only show material in the immobile phase;s ince the temperature was 183 Kthis excludes any frozen methanol (m.p.175.6 K).…”

Section: Angewandte Chemiementioning

confidence: 86%

Managing Hydrogen Bonding in Clathrate Hydrates by Crystal Engineering

et al. 2017

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Methanol is one of the most common inhibitors for clathrate hydrate formation. Crystalline clathrate hydrates containing methanol were synthesized and analyzed by powder X-ray diffraction and 13 CNMR spectroscopy. The data obtained demonstrate that methanol can be ah elper guest for forming structure I, structure II, and structure Hc lathrate hydrates,a sl ong as the lattice framework contains NH 4 F. The latter acts as alattice stabilizer by providing sites for strong hydrogen bonding of the normally disruptive methanol hydroxy group.N H 4 Fa nd methanol can be considered key materials for crystal engineering of clathrate hydrates,a st he modified lattices allowp reparation of hydrates of non-traditional water-soluble guests such as alcohols and diols.M ethanol takes on the role of an unconventional helper guest. This extends clathrate chemistry to ar ealm where neither hydrophobic guests nor high pressures are required. This also suggests that more stable lattices can be engineered for applications such as gas storage.

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“…At ambient pressure, NH4F is soluble in ice Ih across a wide composition range [33][34] and it has been shown to be soluble in clathrate hydrates [35][36] as well as in ice III. 17 This is remarkable since most other ionic species display very low solubilities in ice.…”

Section: Bjerrum (O-h H-o and O…o) Defectsmentioning

confidence: 99%

Ammonium Fluoride as a Hydrogen-Disordering Agent for Ice

et al. 2019

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The removal of residual hydrogen disorder from various phases of ice with acid or base dopants at low temperatures has been a focus of intense research for many decades. As an antipode to these efforts, we now show using neutron diffraction that ammonium fluoride (NH4F) is a hydrogendisordering agent for the hydrogen-ordered ice VIII. Cooling its hydrogen-disordered counterpart ice VII doped with 2.5 mol% ND4F under pressure leads to a hydrogen-disordered ice VIII with ~31% residual hydrogen disorder illustrating the long-range hydrogen-disordering effect of ND4F.The doped ice VII could be supercooled by ~20 K with respect to the hydrogen-ordering temperature of pure ice VII after which the hydrogen-ordering took place slowly over a ~60 K temperature window. These findings demonstrate that ND4F-doping slows down the hydrogenordering kinetics quite substantially. The partial hydrogen order of the doped sample is consistent with the antiferroelectric ordering of pure ice VIII. Yet, we argue that local ferroelectric domains must exist between ionic point defects of opposite charge. In addition to the long-range effect of NH4F-doping on hydrogen-ordered water structures, the design principle of using topological charges should be applicable to a wide range of other 'ice-rule' systems including spin ices and related polar materials. IntroductionWater's phase diagram has been explored for more than a century leading to the discovery of 17 crystallographically distinct phases of ice so far. [1][2][3][4][5] The water molecules in the various phases of ice are fully hydrogen-bonded which gives rise to 4-fold connected networks following the 'twoin-two-out' ice rules with respect to the donation and acceptance of hydrogen bonds. 6-8 Based on this building principle, a wide range of network topologies can be observed ranging from the high-symmetry ice Ih network with only six-membered rings and the highly complex ice V/XIII network to the two interpenetrating individual networks of ice VII/VIII. [6][7][8] Within the constraints of the ice rules, 9 the water molecules can display orientational disorder and such phases are categorized as hydrogen-disordered. In fact, all phases of ice that can be crystallized from liquid water display hydrogen disorder as can be seen in Figure 1(a). In the case of ices Ih, Isd, IV, VI, VII and XII, full hydrogen disorder is observed in neutron diffraction in the form of half-occupied deuterium sites. [10][11][12][13] Ices III and V on the other hand display partial hydrogen order and some of the fractional occupancies deviate significantly from ½. 13 As required by the third law of thermodynamics, the various hydrogen-disordered phases are expected to transform to their corresponding hydrogen-ordered counterparts upon cooling as long-range orientational order of the water molecules is established. Figure 1(b) shows the crystal structures of the hydrogen-disordered ice VII and its hydrogen-ordered counterpart ice VIII.

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Incorporation of ammonium fluoride into clathrate hydrate lattices and its significance in inhibiting hydrate formation

Cited by 15 publications

References 40 publications

Doping-induced disappearance of ice II from water’s phase diagram

Doping-induced disappearance of ice II from water’s phase diagram

Managing Hydrogen Bonding in Clathrate Hydrates by Crystal Engineering

Ammonium Fluoride as a Hydrogen-Disordering Agent for Ice

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