Article
Energy & Fuels
Parisa Naeiji, Mengdi Pan, Manja Luzi-Helbing, Saman Alavi, Judith M. Schicks
Summary: A study was conducted to investigate the dissociation behavior of methane hydrates under different temperature and pressure conditions. Both experimental and simulated data showed that the behavior differed above and below the freezing point of water. At temperatures near or below freezing, CH4 hydrates exhibited self-preservation behaviors due to the formation of a quasi-liquid or amorphous phase at the outer layers of the hydrate crystal. Above the freezing point, dissociation appeared to initiate at the surface of the hydrate phase.
Article
Chemistry, Physical
A. Arjun, Peter G. Bolhuis
Summary: This study investigates the homogenous nucleation rate of CO2 hydrates at low temperatures using transition interface sampling simulations, revealing the differences in hydrate formation processes at different temperatures and shedding light on the kinetics of nucleation processes.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Energy & Fuels
Masakazu Matsumoto, Hideki Tanaka
Summary: The structure selectivity of mixed gas hydrates and group 14 clathrates is examined using statistical mechanical theories and the empirical rule on the topological constraint of the Frank-Kasper phases. The most stable structure is revealed by the generalized phase diagram, and the method developed here can estimate the phase behaviors of clathrate compounds in a wide range of thermodynamic conditions.
Article
Chemistry, Physical
Angel M. Fernandez-Fernandez, Martin Perez-Rodriguez, Manuel M. Pineiro
Summary: This study investigated the properties of fluorinated methane and its hydrates through atomistic molecular dynamics simulations, refining molecular models to compare with experimental results. The three-phase equilibrium of fluorinated methane hydrates was found to be challenging based on the simulation and experimental data comparison.
JOURNAL OF MOLECULAR LIQUIDS
(2021)
Article
Multidisciplinary Sciences
Yong Chen, Satoshi Takeya, Amadeu K. Sum
Summary: Clathrate hydrates are ordered structures stabilized by hydrophobic interactions between water and guest molecules. In this study, an alternative method is proposed to understand the complex structures of clathrate hydrates, revealing the diverse crystalline hydrogen-bonded networks that can be formed. The topological dual relations between clathrate hydrate networks and tetrahedrally close-packed structures provide insights into their nucleation, phase transition, and co-existence mechanisms. Molecular dynamics simulations are employed to explore the intrinsic structural relationships of clathrate hydrates and other unrelated ordered materials.
NATURE COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Manju Sharma, Satyam Singh
Summary: This study investigates the enhanced CO2 sequestration in natural gas hydrates using DFT calculations and molecular dynamics simulations, through the formation of stable dual cages and Y-shaped clusters in the presence of flue and noble gases.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Peng Wang, Jun Wang, Ke Xu, Yanwen Lin, Qiao Shi, Tong Li, Yuequn Fu, Zhisen Zhang, Jianyang Wu
Summary: This study investigates the structure and stability of clathrate hydrates encapsulating fluorinated methane derivatives under mechanical load through molecular dynamics simulations. The study finds distinct structural and mechanical behaviors among different clathrate hydrates, and the lattice constant of clathrate hydrates is influenced by the size and dipole moment of the encapsulated fluorinated methane.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Thermodynamics
Qiao Shi, Yanwen Lin, Yongchao Hao, Zixuan Song, Ziyue Zhou, Yuequn Fu, Zhisen Zhang, Jianyang Wu
Summary: In this study, the unconventional growth characteristics of methane hydrates (MH) were investigated using molecular dynamics simulation and machine learning methods. A new MH structure named MH-VII was discovered, and a long short-term memory (LSTM) neural network-based ML model was developed to predict the complex dynamic growth of MH. This research provides new insights into the growth mechanism of clathrate hydrates, and the LSTM-based ML model serves as a critical tool for studying the time-dependent behaviors of clathrate hydrates under complex conditions.
Article
Chemistry, Multidisciplinary
Sangmin Lee, Thi Vo, Sharon C. Glotzer
Summary: In this study, hard truncated triangular bipyramids self-assemble into seven different colloidal clathrate crystals, consisting of cages that are either empty or occupied by guest particles. Monte Carlo simulations reveal that the crystallization occurs through the compartmentalization of entropy between low- and high-entropy subsystems for the host and guest particles. The researchers also use entropic bonding theory to design host-guest colloidal clathrates with explicit interparticle attraction for experimental realization.
Article
Engineering, Chemical
Yu Wei, Nobuo Maeda
Summary: The memory effect in gas hydrate nucleation refers to the phenomenon that gas hydrates form easier or faster in water with a history of gas hydrate formation. Despite several proposed hypotheses, the cause of the memory effect remains a mystery. This study examines the impact of guest gas supersaturation on the memory effect.
CHEMICAL ENGINEERING SCIENCE
(2023)
Article
Chemistry, Multidisciplinary
Kazuaki Z. Z. Takahashi, Masaki Hiratsuka
Summary: This study combines molecular simulation and machine learning to successfully investigate the structural transitions of cyclopropane hydrate and ice. By evaluating and classifying different local order parameters, the optimal set of order parameters that distinguish between different structures is determined.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Engineering, Mechanical
Jinjie Liu, Ke Xu, Li Yang, Yanwen Lin, Tong Li, Xuezheng Gao, Zhisen Zhang, Jianyang Wu
Summary: This study used classic molecular dynamic simulations to investigate the fracture mechanics of three main methane clathrate hydrates, revealing different mechanical properties among them and degradation caused by nanocracks. Additionally, tip amorphization during crack propagation process was observed in the three methane clathrate hydrates.
ACTA MECHANICA SINICA
(2021)
Article
Energy & Fuels
Bernadette R. Cladek, A. J. Ramirez-Cuesta, S. Michelle Everett, Marshall T. McDonnell, Luke Daemen, Yongqiang Cheng, Paulo H. B. Brant Carvalho, Christopher Tulk, Matthew G. Tucker, David J. Keffer, Claudia J. Rawn
Summary: Natural hydrate deposits are a rich source of CH4. Recent studies have shown that CH4 can be extracted from hydrates by CO2 exchange, which also has the potential for carbon sequestration. Understanding the impact of guest variation in CH4, CO2, and mixed hydrates on their stability and the processes of methane extraction and CO2 sequestration is crucial. The use of inelastic neutron scattering has revealed the dynamic modes in hydrate structures and the behavior of CH4, providing valuable insights for further research.
Article
Chemistry, Physical
Ngoc N. Nguyen, Ruediger Berger, Manfred Wagner, Juergen Thiel, Hans-Juergen Butt, Robert Graf
Summary: This study uncovered the presence of liquid-like water molecules in (polar) tetrahydrofuran clathrates and demonstrated a two-stage dissociation process in these structures. In contrast, no liquid-like water molecules were found in (nonpolar) cyclopentane clathrates.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Energy & Fuels
Mengdi Pan, Parisa Naeiji, Judith M. Schicks
Summary: This study investigates the dissociation of binary and multicomponent structure II hydrates by using a combination of in situ and ex situ Raman spectroscopic measurements and molecular dynamics simulations. The study focuses on the gas release behavior due to the destabilization of hydrate cavities induced by thermal stimulation. The results show that the dissolution process involves the decomposition, reformation, and continuing decomposition of the hydrate crystals until they disappear. The study also reveals differences in the release rate and composition change of different gas molecules during the dissociation process.
Article
Chemistry, Physical
Parisa Naeiji, Tom K. Woo, Saman Alavi, Ryo Ohmura
JOURNAL OF CHEMICAL PHYSICS
(2020)
Article
Chemistry, Physical
Masamichi Kodera, Tomoyuki Matsueda, Rodion V. Belosludov, Ravil K. Zhdanov, Vladimir R. Belosludov, Satoshi Takeya, Saman Alavi, Ryo Ohmura
JOURNAL OF PHYSICAL CHEMISTRY C
(2020)
Article
Chemistry, Multidisciplinary
Riku Matsuura, Saman Alavi, Ryo Ohmura
Summary: This study presents visual observations of the formation and growth of structure-H hydrate formed with methane and 1-methylpiperidine (MPD). The crystal growth dynamics were categorized into two types depending on the subcooling temperature, showing changes in crystal shape and size with different subcooling conditions. The implications of crystal morphology on suitable conditions for industrial utilization of this hydrate for gas capture applications are discussed.
CRYSTAL GROWTH & DESIGN
(2021)
Article
Chemistry, Physical
Yuri Kondo, Saman Alavi, Satoshi Takeya, Ryo Ohmura
Summary: Experimental and computational studies were conducted to investigate the interaction between fluoromethane and pinacolone with water to form hydrates, showing that the addition of pinacolone molecules can lead to the formation of the sH phase and lower the equilibrium hydrate formation pressure. The molecular dynamics simulations revealed weak hydrogen bonding between pinacolone molecules and water in the cages within the HFC-41 phase, with oblate HFC-41 molecules showing a strong orientational preference towards the equatorial planes of the cages.
JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Chemistry, Multidisciplinary
Sanehiro Muromachi, Hassan Sharifi, Saman Alavi, John A. Ripmeester, Peter Englezos
Summary: This study investigated the structural characteristics of clathrate hydrates formed with the cyclic amine pyrrolidine and the structurally related THF. The inclusion of pyrrolidine led to an expansion of cage sizes in the hydrate, while the cages without pyrrolidine did not expand to the same degree. The refined X-ray diffraction structure suggested that pyrrolidine was incorporated in the large cage without forming hydrogen bonds with the cage water molecules, supported by molecular dynamics simulations showing weak hydrogen bond interactions between pyrrolidine and water molecules.
CRYSTAL GROWTH & DESIGN
(2021)
Article
Chemistry, Physical
Zhaoqian Su, Saman Alavi, John A. Ripmeester, Gedaliah Wolosh, Cristiano L. Dias
Summary: The study reveals that methanol can both slow down and accelerate the formation of methane clathrate hydrates, depending on the temperature. This dual role is attributed to the temperature-dependent methane-methanol interaction and the competition between methanol and water for interacting with methane.
JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Engineering, Chemical
Jeongtak Kim, Byeonggwan Lee, Kyuchul Shin, Seong-Pil Kang, Ki Hun Park, Minjun Cha, Saman Alavi, John A. Ripmeester
Summary: It was found that water-NH4F solutions can form clathrates consisting of solid solutions of water and NH4F, which have the same structure as the canonical clathrate hydrates, and can incorporate different guest molecules such as methanol. The research provides insight into the potential of NH4F-doped hydrate lattice, aided by catalytic methanol, for use in hydrate-based gas separation processes.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2021)
Article
Energy & Fuels
Jeongtak Kim, Kyuchul Shin, Saman Alavi, John A. Ripmeester
Summary: This study investigated the effect of ammonium fluoride doping on THF + methanol clathrate hydrates using experimental and simulation methods. The results showed that ammonium fluoride can stabilize methanol in the hydrate cages and significantly affect the thermal properties of the clathrate hydrates. The simulations revealed strong interactions between methanol guest molecules and ammonium fluoride host pairs, suggesting a complementary stabilization mechanism. These findings provide important insights into the nature of ion-pair doped clathrate systems and their potential applications in gas storage.
Article
Energy & Fuels
Byeonggwan Lee, Kyuchul Shin, Saman Alavi, John A. Ripmeester
Summary: In this study, the effect of NH4F doping on N-2, O-2, and CH4 hydrates was investigated. The results showed that NH4F doping can modify the size and electrostatic charge distribution of molecules within the hydrate cages, and induce a transition in the preferred structure of N2 hydrate. These findings suggest that crystal engineering of hydrate lattices can be a potential approach to enhance hydrate-based gas separation technologies.
Article
Chemistry, Physical
Parisa Naeiji, Tom K. Woo, Ryo Ohmura, Saman Alavi
Summary: This study investigated the interfacial behavior of tetrabutylammonium bromide (TBAB) aqueous solutions under different conditions. The results showed that TBAB solutions have lower interfacial tension and higher gas adsorption at the interface, which facilitate the formation of semiclathrate hydrates. CO2 exhibits preferential adsorption compared to CH4 due to stronger interactions in the solution. The increased adsorption of CH4 at the solution surface is attributed to the hydrophobic interactions between the TBAB cation and methane gas.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Takuma Misawa, Tomoaki Ishikawa, Satoshi Takeya, Saman Alavi, Ryo Ohmura
Summary: CO2 separation from H2 + CO2 gas mixture is essential for stable supply of blue hydrogen, and hydrate-based CO2 separation is a superior technology in terms of environmental and economic aspects. The study showed successful CO2 separation in the H2 + CO2 + CP + H2O system at 284 K, but with an increase in energy costs due to hydrogen loss.
JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
(2023)
Article
Energy & Fuels
Parisa Naeiji, Mengdi Pan, Manja Luzi-Helbing, Saman Alavi, Judith M. Schicks
Summary: A study was conducted to investigate the dissociation behavior of methane hydrates under different temperature and pressure conditions. Both experimental and simulated data showed that the behavior differed above and below the freezing point of water. At temperatures near or below freezing, CH4 hydrates exhibited self-preservation behaviors due to the formation of a quasi-liquid or amorphous phase at the outer layers of the hydrate crystal. Above the freezing point, dissociation appeared to initiate at the surface of the hydrate phase.
Article
Chemistry, Physical
Satoshi Takeya, Hiroshi Fujihisa, Saman Alavi, Ryo Ohmura
Summary: We report a thermally induced phase transition of cubic structure II hydrates of tetrahydropyran (THP) and CO2 below about 140 K. The phase transition was characterized by powder X-ray diffraction measurements at variable temperatures. A dynamical ordering of the CO2 guests in small pentagonal dodecahedral 512 host water cages, not previously observed in the simple CO2 hydrate, occurs simultaneously with the symmetry lowering transition from a cubic structure II to a tetragonal unit cell.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Sanehiro Muromachi, Satoshi Takeya, Saman Alavi, John A. Ripmeester
Summary: The crystal structure of tetra-n-butylammonium chloride (TBAC) + CO2 semiclathrate hydrate, known for its high CO2 selectivity, was studied using single crystal X-ray diffraction. The study revealed that the CO2 gas occupies dodecahedral (D) cages along with water and chloride ions. Different types of D cages were observed, with the ratio of D-L:D-M:D-N as 2:2:1. The CO2 molecules were found in distorted D-M and D-N cages, while chloride ions were partially present in D-M cages. The spatial distribution of CO2 in the cages was limited due to the distortion of D-M and D-N cages. The study also highlighted the superior CO2 capture preference of TBAC hydrate.
Article
Chemistry, Multidisciplinary
Byeonggwan Lee, Jeongtak Kim, Kyuchul Shin, Ki Hun Park, Minjun Cha, Saman Alavi, John A. Ripmeester
Summary: The study investigated the hydrate structure and conformation of 1-pentanol as a guest molecule in structure II hydrate, and found that by doping with NH4+ and F- ions, the 1-pentanol was successfully accommodated in the compact conformation of the sII large cage.
