Thermodynamic Stability of Structure H Hydrates Based on the Molecular Properties of Large Guest Molecules

Tezuka, Kyoichi; Taguchi, T.; Alavi, Saman; Sum, Amadeu K.; Ohmura, Ryo

doi:10.3390/en5020459

Cited by 16 publications

(17 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The stability has been related to the maximum temperature at which the clathrate phase disappears for a given pressure, that is, the experimental data have to be described by the formation free energy of the hydrogen clathrate, which equals to the sum of free energies of its components. The Gibbs free energy calculations obtained in this study with the SR method at 273 K indicate order of stability different from that in ref . Our calculations have not been carried out on the dissociation curve of the clathrate hydrates, and the stabilization free energy obtained from our simulations is different from the formation free energy corresponding to the experimental conditions.…”

Section: Resultscontrasting

confidence: 92%

“…In the study of ref , the stability of sH clathrate has been determined based on equilibrium pressure or pressure of formation as calculated from interpolation of experimental data at 276 K. In the study stability increases in the order 2,3-dimethyl-1-butene (2DMBE) < 2,3-dimethylbutane (2DMBA) < 3,3-dimethylpentane (DMP) < 3,3-dimethyl-1-butene (3DMBE) < cycloheptane (CHP) < methylcyclohexane (MCH). The formation pressure is measured at a point where the disappearance of the hydrate crystal during temperature increase takes place, that is, on the dissociation curve.…”

Section: Resultsmentioning

confidence: 99%

“…One of the main assumptions underlying the self-referential method is that all molecules are treated as rigid bodies. Recent X-ray crystallography and molecular dynamics studies − demonstrated that conformation changes of promoter molecules can be substantial in the large cages of structure H hydrate. In order to understand within the framework of the self-referential technique the effect of promoter conformations on the thermodynamic stability of sH clathrate hydrate, the Gibbs free energy of sH hydrate with six different promoters and their conformers has been calculated.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Free Energy Calculations for Identifying Efficient Promoter Molecules of Binary sH Hydrogen Clathrates

et al. 2014

View full text Add to dashboard Cite

To determine the stabilizing effect of different promoter molecules on the clathrate, the Gibbs free energy of fully occupied binary sH hydrogen clathrates with secondary guest molecules in the large cages is calculated with Monte Carlo simulations. The small and medium cages of sH are occupied by one H2 guest molecule. Various promoter molecules enclathrated in the large cages are considered. Simulations are conducted in the pressure range of 250–1000 atm for temperatures ranging from 233 to 273 K. We investigate the effect of dipole moment and molecular size on the thermodynamic stability of sH hydrogen clathrate hydrate.

show abstract

Section: Resultscontrasting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Free Energy Calculations for Identifying Efficient Promoter Molecules of Binary sH Hydrogen Clathrates

et al. 2014

View full text Add to dashboard Cite

show abstract

“…In this regard, the water is a host compound, and the clathrate hydrates are a class of guest–host materials. Knowledge of relevant topics is required to understand the clathrate hydrate formation process, such as heat − and mass , transfer, phase diagrams, ,− and molecular structures of the guest compound. ,− More details of the relationship between the clathrate hydrate formation process and knowledge of the relevant topics are described in the Supporting Information. Also, novel technologies utilizing clathrate hydrate formation and decomposition have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Visual Observation of Tetra-n-butylammonium Bromide Ionic Semiclathrate Hydrate Formation: A Laboratory Experiment

Yasuda

2021

J. Chem. Educ.

View full text Add to dashboard Cite

A laboratory experiment was performed using tetra-n-butylammonium bromide (TBAB) ionic semiclathrate hydrate, a crystalline compound. Ionic semiclathrate hydrates have unique properties, and hence, novel technologies utilizing the ionic semiclathrate hydrates have been proposed to date. Thus, students could learn fundamentals of functional materials through ionic semiclathrate hydrates from chemical and engineering points of view. In the experiment, formation of the TBAB hydrate was observed at fixed temperature and under atmospheric pressure by using TBAB aqueous solutions having TBAB mass fractions of w TBAB = 0.10, 0.20, 0.30, 0.40, and 0.50. There are no serious safety hazards. In addition, the experiment can be performed using inexpensive equipment and materials. The amount of the formed TBAB hydrate and its crystal morphology depended on the concentration of the aqueous solution. The students needed to submit a laboratory report describing fundamentals of the ionic semiclathrate hydrates, a relationship between equilibrium conditions and the amount of the formed TBAB hydrate, and an adequate crystal morphology of the TBAB hydrate crystals as a thermal storage material. Most students understood the experiment well, and the average score of the reports was approximately 80%.

show abstract

“…One important factor in the phase equilibrium is the relationship between the molecular size of guest compounds and the cage size. 9 When the ratio of the molecule-to-cage size (or cavity ratio) is around 0.76−1.0, the guest compound could be safely affirmed to enter the cage, and the hydrate is stable. If the cavity ratio is close to 1.0, the hydrate can still be stable.…”

Section: Introductionmentioning

confidence: 99%

Effect of Help-Guest Size and Hydrogen Bonding on the Stability of N-Methylpiperidine Structure H Clathrate Hydrate

et al. 2020

Self Cite

View full text Add to dashboard Cite

The phase equilibrium diagram measurements, powder X-ray diffraction, and molecular dynamics simulations are used to characterize the stability, structure, and guest dynamics of the structure H (sH) N-methylpiperidine (NMP) clathrate hydrate with the difluoromethane (HFC-32) help gas. The pressure−temperature phase diagram of the NMP + HFC-32 hydrate is more stable under higher temperature−lower pressure conditions than the simple HFC-32 structure I (sI) hydrate or the sH hydrates of NMP with the methane help-gas guest compound. The hydrate with these investigated guest compounds was more stable, although the HFC-32 help-guest molecules should be comparatively large and more difficult to fit into the small and medium cages of sH hydrate. Molecular dynamics simulations show that the NMP guest molecules form hydrogen bonds with the cage water molecules in the NMP + HFC-32 sH hydrate, while similar hydrogen bonding was not observed for the sH hydrate of NMP with CH 4 . The larger size and nonzero dipole moment of the HFC-32 help-gas could lead to tension in the small and medium sH cages, which could weaken the cage structures in the hydrate framework, thus enabling the formation of hydrogen bonding between the NMP molecules in the neighboring cages with the cage water molecules. This is a first case where the combination of larger help-gas molecules and hydrogen bonding of the large-cage guests was observed to help stabilize a sH hydrate phase. The newly found phenomena could be the favorable properties for sophisticated gas-storing materials with the minimum environmental impact.

show abstract

Thermodynamic Stability of Structure H Hydrates Based on the Molecular Properties of Large Guest Molecules

Cited by 16 publications

References 19 publications

Free Energy Calculations for Identifying Efficient Promoter Molecules of Binary sH Hydrogen Clathrates

Free Energy Calculations for Identifying Efficient Promoter Molecules of Binary sH Hydrogen Clathrates

Visual Observation of Tetra-n-butylammonium Bromide Ionic Semiclathrate Hydrate Formation: A Laboratory Experiment

Effect of Help-Guest Size and Hydrogen Bonding on the Stability of N-Methylpiperidine Structure H Clathrate Hydrate

Contact Info

Product

Resources

About