Molecular Dynamics Simulation Studies on the Stability and Dissociation of Clathrate Hydrates of Single and Double Greenhouse Gases

Abstract

Comprehending and controlling the stability and dissociation of greenhouse gases hydrates are critical for a variety of hydrate-based industrial applications, such as greenhouse gas separation, sequestration, or utilization. Although the promotion effects of greenhouse F-gases (F-promoters) and new cyclic promoters on CO2 hydrates have been acknowledged, the involved molecular mechanisms are poorly understood. This work was therefore conducted to investigate the intermolecular mechanisms of the properties of CO2 and NF3 hydrates using molecular dynamics (MD) simulation to better understand their stability and dissociation and the effects of thermodynamic conditions as well as cage occupancy. In addition, the stability of CO2/CO2 + CH4 hydrates in the presence of seven thermodynamic hydrate promoters (THPs) from different molecular groups or substituents was evaluated. Results reveal that after the breakup of the hydrate, the propensity of NF3 to form nanobubbles is more than that of CO2 molecules. The relative concentration distribution of partially occupied hydrates was also found to be greater than that of completely filled by guest gases. MD simulation results of CO2 double and mixed hydrates also show that the type of large molecular guests in the large cages plays a major role in the stabilization of the clathrate hydrate network. The structural properties, however, indicate that the resistance against being dissociated for CO2 + promoter can be somewhat increased when half of the CO2 molecules in small cages is replaced by CH4. In addition, the existence of neopentyl alcohol in large cavities was found to facilitate the process of hydrate dissociation by making new hydrogen bonds between hydroxyl groups and water molecules. Among studied systems with THPs, cyclopentane, and cyclohexane in comparison with F-promoters seem to be more susceptible to maintaining the stability of CO2 clathrate hydrate.

Molecular Dynamics Simulations of the Stability and Dissociation of Structure-H Clathrate Hydrates in the Presence of Different Amino Acids, Gas Species, and sH Hydrate Formers

“…In this regard, to comprehend the effects of bio-friendly amino acids on CH 4 − and CO 2 sI hydrate formation and dissociation mechanisms, some studies using molecular dynamics (MD) simulations have been performed. Also, we recently employed MD simulations to understand the growth and dissociation of CO 2 clathrate hydrates in the existence of various thermodynamic and kinetic promoters. , Since organic, eco-friendly components such as amino acids can play a positive role in hydrate applications and sH hydrates would also be the proper alternative for such aims, comprehending the impressions of these components on the stability and dissociation of sH clathrate hydrates would be crucial. However, they are still poorly understood at a molecular level.…”

Molecular dynamics simulations of CO2 clathrate hydrate in the presence of organic components

“…To perform all simulations, the classical MD same as our previous work for molecular investigations of CO2 hydrates with different organic promoters was carried out [8]. To provide the initial clathrate hydrate structure, the water molecular positions were adopted from the Takeuchi et al work that optimized the configurations with satisfying the ice rules [9].…”

Confining CO2 inside sI clathrate‐hydrates: The impact of the CO2–water interaction on quantized dynamics

“…Spectroscopic characterization of CO 2 @sI clathrate hydrates has been reported by solid-state NMR, infrared (IR) and Raman spectroscopy, single crystal X-ray, powder X-ray, and neutron diffraction and scattering experiments, [39][40][41][44][45][46][47][48][49][50][51] while computations from electronic structure quantum chemistry methodologies and molecular dynamics (MD) simulations have investigated guesthost interactions, stability, structural and physical/chemical/ mechanical properties, cage occupancy, phase diagrams, and so forth. 10,13,18,20,23,[27][28][29][30][31]35,[52][53][54][55][56][57] Crystal X-ray and powder X-ray experiments have provided information on the CO 2 orientation in the sI cages, and recorded FTIR/IR spectra have also confirmed the encapsulation of the CO 2 in both small and large sI cages at low temperatures of 5.6 K, providing vibrational transitions of the antisymmetric stretch mode of the 12 CO 2 clathrate and its 13 CO 2 and 18 OCO isotopes, as well as Fermi resonances up to 5100 cm À1 . [39][40][41]49,50 Such findings have clearly indicated the effect of the size, shape and composition of the host-cage on the trapped guest-molecule, and have motivated our previous study 56 on quantum dynamics of a single CO 2 molecule in the sI cages.…”

“…Clathrate hydrates are crystalline water‐based inclusion compounds with gas molecules trapped in the cavities formed by the ice–water networks. They have been extensively studied due to their technological applications 1–35 . For example, the CO 2 clathrate hydrates are of interest driven by their potential use in CO 2 gas capture and storage from the Earth's atmosphere, and control climate change, 36–38 while in an astrophysical context their formation and presence could influence the composition and stability of planetary ices and comets 39–41 .…”

“…The carbon dioxide clathrate hydrates are known to form crystals of sI structure at low pressures, 41,43 containing small and large cages. Spectroscopic characterization of CO 2 @sI clathrate hydrates has been reported by solid‐state NMR, infrared (IR) and Raman spectroscopy, single crystal X‐ray, powder X‐ray, and neutron diffraction and scattering experiments, 39–41,44–51 while computations from electronic structure quantum chemistry methodologies and molecular dynamics (MD) simulations have investigated guest–host interactions, stability, structural and physical/chemical/mechanical properties, cage occupancy, phase diagrams, and so forth 10,13,18,20,23,27–31,35,52–57 . Crystal X‐ray and powder X‐ray experiments have provided information on the CO 2 orientation in the sI cages, and recorded FTIR/IR spectra have also confirmed the encapsulation of the CO 2 in both small and large sI cages at low temperatures of 5.6 K, providing vibrational transitions of the antisymmetric stretch mode of the clathrate and its and isotopes, as well as Fermi resonances up to 5100 cm −1 39–41,49,50 .…”