Guest Partitioning and Metastability of the Nitrogen Gas Hydrate - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Physical Chemistry C Année : 2017

Guest Partitioning and Metastability of the Nitrogen Gas Hydrate

Résumé

Gas clathrate hydrates or gas hydrates are made of H-bonded water molecules forming cages, within which gaseous (guest) molecules are encapsulated. The formed clathrate structures, which may be metastable, depend on the nature and on the partitioning of the guest molecules in the water cage. This work focuses on the structural and vibrational properties of nitrogen hydrate in its two clathrate forms (namely, SI and SII) in the thermodynamic ranges 50–200 bar and 150–270 K, together with a comprehensive analysis of the transformation from SI to SII of this gas hydrate. The thermal expansion of both structures has been measured at 1 bar, and the melting of the nitrogen hydrate has been measured at ca. 210 K at 1 bar. Moreover, the SI structure is metastable in the studied pressure region: from time-dependent neutron powder diffraction analysis, it is shown that the SI structure transforms over time to the SII structure with a rate of (1.37 ± 0.17) × 105 s–1 at 100 K and at 1 bar. The transformation is also characterized by an induction time (i.e., the lifetime of the pure SI structure) of 0.49 day. We have also investigated the guest partitioning of the nitrogen hydrate using high-resolution Raman scattering. Vibrational bands of nitrogen molecules encapsulated in large cages are measured at lower wavenumbers than the one associated with encapsulation in small cages (by 1.1 cm–1 in SI and 0.8 cm–1 in SII). In the case of the thermodynamically stable SII phase, the dependence of the guest partitioning has been characterized as a function of the pressure–temperature conditions. Variation of the relative cage filling is demonstrated. While the small cages remain singly occupied according to previous neutron diffraction analysis, this variation is attributed to large cages of the nitrogen hydrate that easily catch or release nitrogen guest molecules. This study thus provides new opportunities for preparing nitrogen gas hydrates with a “targeted” structure and relative cage filling not only by varying the pressure and temperature but also by playing with the structural metastability.
Fichier non déposé

Dates et versions

hal-04520646 , version 1 (25-03-2024)

Identifiants

Citer

Claire Petuya, Françoise Damay, Bertrand Chazallon, Jean-Luc Bruneel, Arnaud Desmedt. Guest Partitioning and Metastability of the Nitrogen Gas Hydrate. Journal of Physical Chemistry C, 2017, 122 (1), pp.566-573. ⟨10.1021/acs.jpcc.7b10151⟩. ⟨hal-04520646⟩
2 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More