Multiscale Piezoelasticity of Methane Gas Hydrates: From Bonds to Cages to Lattices

Abstract

For the past several decades, natural gas, also called methane gas, has been recognized as a green energy resource. It can generate energy by burning and produces fewer pollutants and carbon dioxide than coal and petroleum. For these reasons, it is also being viewed as a bridge fuel to renewable energy. Conservative estimates suggest that 80% of the naturally occurring hydrates on the planet contains natural gas. This vast amount translates to approximately twice the amount of energy stored in fossil fuels and oils. In addition, the special guest–host structure of gas hydrates provides a significant storage capacity, which makes the hydrate become a competitive candidate for carbon dioxide sequestration. However, the instability of hydrates during exploration becomes the biggest barrier for methane gas extraction and carbon dioxide sequestration. Thus, to overcome this barrier, this paper aims to investigate the stability limits and study the piezo effect of structure I (sI) methane gas hydrates at 0 K. This work investigates the structure, thermodynamics, and elasticity of sI methane hydrates subjected to pressure loads, at three scales, atoms, cages, and lattice, using the density functional theory in conjunction with homogenization methods and the theory of mixtures. The distribution functions of bond parameters are characterized in the hydrate system, which provides a novel understanding on the spread of values at the smallest scale. The roles of different types of cages at the mesoscale have been identified, such as continuous phase and disperse inclusion. At the continuum scale, the different deformation mechanisms are observed (affine and non-affine), which correspond to different fracture mechanisms (brittle and ductile) under tensile and compressive pressures, respectively. Taken together, the systematic atomic–cage–lattice multiscale characterization proves fruitful in linking processes that connect mechanical properties, cage geometry, and hydrogen bonding. The multiscale methodology can be generalized to other gas hydrates to improve the fundamental understanding and obtain engineering correlations.

Interfacial Effects during Phase Change in Multiple Levitated Tetrahydrofuran Hydrate Droplets

“…As such, it is more precise to say that droplets in adjacent positions only have a higher likelihood of nucleating together. Second, this likelihood may be reduced for THF hydrates as they have greater tensile strengths than ice (i.e., natural gas hydrates, which have analogous structural properties to THF hydrates, have been measured to crack only under liquid–solid interfacial pressures in the gigapascal range versus the megapascal range for ice), which means that there could be less cracking and less HNP emission. − However, this implies that the instantaneous pressures at the liquid–solid interface at nucleation between ice and THF hydrate are similar, which may not necessarily be the case. While models exist to calculate these values for water, they cannot be applied to hydrates due to significant differences in growth rates and mechanisms, and no models for this hydrate formation parameter currently exist .…”

2022 Pioneers in Energy Research: John Ripmeester

“…Piezoelasticity properties of methane hydrates were calculated using density functional theory (DFT) at 0 K and high pressure to study the strength and nature of small and large cages of structure I (sI) hydrates. 39 ■ APPLICATIONS A review by Rodionova et al 40 discussed structures of single and double ionic clathrate hydrates (semi-clathrates) in the presence of different gases and possibilities of structural transition as a result of the presence of these gases. Gas hydrates could be used as a molecular sieve, whereby depending upon the shape and size of the hydrate-forming guests, one of the gases from a gas mixture may preferentially occupy the solid hydrate cages and become separated from its mixture.…”

“…A study by Tadepalli and Kumar reported long-scale molecular dynamics simulations for a microsecond for the CH 4 /CO 2 exchange process and verified if the defects caused in the structure with a tertiary molecule, like ammonia, can enhance the process by carrying CO 2 beyond the surface layers. Piezoelasticity properties of methane hydrates were calculated using density functional theory (DFT) at 0 K and high pressure to study the strength and nature of small and large cages of structure I (sI) hydrates …”

Progress and Outlook of Solar-Powered Biomass for Biorefineries: A Minireview

“…23 In another work, Servio and co-workers focused only on photocatalytic H 2 production from biomass. 24 Similarly, Jiang et al published a review article on the thermocatalytic conversion of biomass-derived glucose to value-added chemicals. 25 In contrast to these previous reviews, our work focuses on photocatalysts, such as metal sulfides, zeolites, TiO 2 , and g-C 3 N 4 -based porous materials, and the wide range of products that can be produced from biomass valorization.…”

“…Manyar et al recently published a review article on the upgradation of biomass to biofuels using only metal oxide catalysts . In another work, Servio and co-workers focused only on photocatalytic H 2 production from biomass . Similarly, Jiang et al published a review article on the thermocatalytic conversion of biomass-derived glucose to value-added chemicals .…”