Clathrate Hydrate Formation Research Articles

Carbon Dioxide Clathrate Hydrate Formation and Mass Balance Calculation: A Laboratory Experiment

Carbon Dioxide Clathrate Hydrate Formation and Mass Balance Calculation: A Laboratory Experiment

Design of eco-friendly antifreeze peptides as novel inhibitors of gas-hydration kinetics.

In this study, peptides designed using fragments of an antifreeze protein (AFP) from the freeze-tolerant insect Tenebrio molitor, TmAFP, were evaluated as inhibitors of clathrate hydrate formation. It was found that these peptides exhibit inhibitory effects by both direct and indirect mechanisms. The direct mechanism involves the displacement of methane molecules by hydrophobic methyl groups from threonine residues, preventing their diffusion to the hydrate surface. The indirect mechanism is characterized by the formation of cylindrical gas bubbles, the morphology of which reduces the pressure difference at the bubble interface, thereby slowing methane transport. The transfer of methane to the hydrate interface is primarily dominated by gas bubbles in the presence of antifreeze peptides. Spherical bubbles facilitate methane migration and potentially accelerate hydrate formation; conversely, the promotion of a cylindrical bubble morphology by two of the designed systems was found to mitigate this effect, leading to slower methane transport and reduced hydrate growth. These findings provide valuable guidance for the design of effective peptide-based inhibitors of natural-gas hydrate formation with potential applications in the energy and environmental sectors.

Harnessing Nuclear Magnetic Resonance Spectroscopy to Decipher Structure and Dynamics of Clathrate Hydrates in Confinement: A Perspective.

This perspective outlines recent developments in the field of NMR spectroscopy, enabling new opportunities for in situ studies on bulk and confined clathrate hydrates. These hydrates are crystalline ice-like materials, built up from hydrogen-bonded water molecules, forming cages occluding non-polar gaseous guest molecules, including CH4, CO2 and even H2 and He gas. In nature, they are found in low-temperature and high-pressure conditions. Synthetic confined versions hold immense potential for energy storage and transportation, as well as for carbon capture and storage. Using previous studies, this report highlights static and magic angle spinning NMR hardware and strategies enabling the study of clathrate hydrate formation in situ, in bulk and in nano-confinement. The information obtained from such studies includes phase identification, dynamics, gas exchange processes, mechanistic studies and the molecular-level elucidation of the interactions between water, guest molecules and confining interfaces.

SEM/Raman spectroscopy of clathrites as analogs of authigenic carbonates in ocean worlds

AbstractThere is evidence from the near‐infrared observations of space missions of the presence of carbonates on the surface of several ocean worlds. However, their genesis remains unresolved. We investigate the hypothesis that these carbonates may be in the form of clathrites assuming that clathrate hydrates are stable phases in the crust and ocean of these ocean worlds. In order to support this, we studied a sample of a potential clathrite from the Hydrate Ridge cold seep (Cascadia Subduction Zone), the carbonate rock fossil of clathrate hydrates, as a terrestrial analogue. We characterised the mineralogy and texture of the sample by using a coupled confocal Raman microscope and scanning electron microscopy instrument with the aim of identifying possible geo‐ and biosignatures, which could be relevant for future missions of exploration to ocean worlds and Mars. Our results show that aragonite is the dominant mineral phase in the clathrite sample, but Mg‐calcite and dolomite were also identified. These three carbonates constitute a pattern related to clathrate hydrate formation and dissociation processes. Dolomite was defined as a biosignature of gas hydrate microbiomes because it was integrated within Mg‐calcite grains precipitated after clathrate hydrate dissociation. Nevertheless, no spectral changes were observed in Raman bands of carbonate minerals that would indicate the influence of clathrate hydrates in their genesis. We also observed that Raman band positions of the associated framboidal pyrites are a characteristic signature of the associated framboid‐like texture because its potential as biosignature may only be attributed by biochemical analysis.

Partitioning photochemically formed CO2 into clathrate hydrate under interstellar conditions.

Clathrate hydrates (CHs), host-guest compounds of water forming hydrogen-bonded cages around guest molecules, are now known to exist under interstellar conditions. Experimental evidence demonstrated that prolonged thermal treatment of a solid mixture of water and CO2/CH4 produces CHs at 10-30 K under simulated interstellar conditions. However, in the current study, we show that CO2 produced photochemically by vacuum ultraviolet irradiation of H2O-CO mixtures at 10 K and ∼10-10 mbar, gets partitioned into its CH phase and a matrix phase embedded in amorphous ice. The process occurring under simulated interstellar conditions was studied at different temperatures and H2O-CO compositions. The formation of CO2 CH and other photoproducts was confirmed using reflection absorption infrared spectroscopy. The UV-induced photodesorption event of CO2 may provide the mobility required for the formation of CHs, while photoproducts like methanol can stabilize such CH structures. Our study suggests that new species originating during such energetic processing in ice matrices may form CH, potentially altering the chemical composition of astrophysical environments.

Zero-point energy effects on the stability of water clusters: Implications on the uptake of hydrogen isotope substituted water on ice and clathrate hydrate phases

To study the effect of hydrogen isotope substitution on the uptake of water during formation of clathrate hydrates, the harmonic intermolecular librational modes of selected water clusters (X2O)n with n = 2–6 and hydrogen isotopes X = H, D, and T are studied. The effects of the quantum mechanical zero-point energy (ZPE) in each cluster on the binding energies of the H2O, D2O, and T2O clusters are determined, with ZPE leading to the smallest binding energies in the H2O clusters and the largest binding energies in the T2O clusters. Corrections for anharmonicity of the librational modes are considered, and these bring the frequency ranges of the calculated intermolecular librational modes in the clusters to the experimental ranges of the librational modes in the infrared spectra of H2O and D2O solid ice and clathrate hydrate phases, and liquid H2O water. These calculations show the expected ranges of the binding energy of tritiated water onto a solid ice and clathrate hydrate surface and can help quantify the isotopic enrichment on a growing clathrate hydrate phase from the solution.

Novel approach for designing order parameters of clathrate hydrate structures by graph neural network.

Clathrate hydrates continue to be the focus of active research efforts due to their use in energy resources, transportation, and storage-related applications. Therefore, it is crucial to define their essential characteristics from a molecular standpoint. Understanding molecular structure in particular is crucial because it aids in understanding the mechanisms that lead to the formation or dissociation of clathrate hydrates. In the past, a wide variety of order parameters have been employed to classify and evaluate hydrate structures. An alternative approach to inventing bespoke order parameters is to apply machine learning techniques to automatically generate effective order parameters. In earlier work, we suggested a method for automatically designing novel parameters for ice and liquid water structures with Graph Neural Networks (GNNs). In this work, we use a GNN to implement our method, which can independently produce feature representations of the molecular structures. By using the TeaNet-type model in our method, it is possible to directly learn the molecular geometry and topology. This enables us to build novel parameters without prior knowledge of suitable order parameters for the structure type, discover structural differences, and classify molecular structures with high accuracy. We use this approach to classify the structures of clathrate hydrate structures: sI, sII, and sH. This innovative approach provides an appealing and highly accurate replacement for the traditional order parameters. Furthermore, our method makes clear the process of automatically designing a universal parameter for liquid water, ice, and clathrate hydrate to analyze their structures and phases.

Facile and sustainable methane storage via clathrate hydrate formation with low dosage promoters in a sponge matrix

Natural gas (NG) is an effective and eco-friendly fossil fuel with regard to reducing CO2 emission. In this manner, many technologies have been developed to store the NG efficiently, like LNG and CNG. Among them, natural gas hydrates (NGH) emerge as a promising option to replace LNG and CNG, due to their high energy density and mild storage conditions. Nevertheless, vigorous mechanical stirring, which is typically adopted to produce the NGH, requires high energy inputs and short periodic managements from elevated viscosity of the fluids during the production process. In this work, the effective method for synthesizing methane hydrates under a non-stirred system was proposed and evaluated. A commercial melamine sponge, which is cheap, lightweight, and easily accessible, was utilized as a supporting matrix. Additionally, various types of thermodynamic (e.g., CP (immiscible) and THF (miscible) and kinetic promoters (e.g., sodium dodecyl sulfate (SDS, surfactant) and l-methionine (L-met, amino acid)) were introduced and assessed in terms of methane storage capacity and kinetic parameters during the long-term 20 cycles of formation-dissociation. These combinations from low dosage of thermodynamic and kinetic promoters (e.g., CP + SDS, and DIOX + L-met) facilitated immediate nucleation, and high methane uptake was obtained by inducing sequential growth of methane hydrates. Finally, comparing with the CNG technology, it was shown that the mixed hydrates formed with the low-dosage of promoters were profitable in terms of formation and storage conditions.

Formation and Dissociation of Dimethyl Ether Clathrate Hydrate in Interstellar Ice Mimics

Formation and Dissociation of Dimethyl Ether Clathrate Hydrate in Interstellar Ice Mimics

Probing the critical nucleus size in tetrahydrofuran clathrate hydrate formation using surface-anchored nanoparticles

Controlling the formation of clathrate hydrates is crucial for advancing hydrate-based technologies. However, the microscopic mechanism underlying clathrate hydrate formation through nucleation remains poorly elucidated. Specifically, the critical nucleus, theorized as a pivotal step in nucleation, lacks empirical validation. Here, we report uniform nanoparticles, e.g., graphene oxide (GO) nanosheets and gold or silver nanocubes with controlled sizes, as nanoprobes to experimentally measure the size of the critical nucleus of tetrahydrofuran (THF) clathrate hydrate formation. The capability of the nanoparticles in facilitating THF clathrate hydrate nucleation displays generally an abrupt change at a nanoparticle-size-determined specific supercooling. It is revealed that the free-energy barrier shows an abrupt change when the nanoparticles have an approximately the same size as that of the critical nucleus. Thus, it is inferred that THF clathrate hydrate nucleation involves the creation of a critical nucleus with its size being inversely proportional to the supercooling. By proving the existence and determining the supercooling-dependent size of the critical nucleus of the THF clathrate hydrates, this work brings insights in the microscopic pictures of the clathrate hydrate nucleation.

Surface modification of mesostructured cellular foam to enhance hydrogen storage in binary THF/H2 clathrate hydrate

Solid-state tuning of a mesostructured cellular foam (MCF) enhances hydrogen storage in clathrate hydrates. Grafting of promoter-like molecules (e.g., tetrahydrofuran) at the internal surface of the MCF improved the kinetics of formation of binary H2-THF clathrate hydrate.

Geometric and Hydrophilic Effects of Oxirane Compounds with a Four-Carbon Backbone on Clathrate Hydrate Formation.

The physicochemical properties of clathrate hydrates are influenced by the chemical nature and three-dimensional (3D) geometry of the added molecules. This study investigates the effects of five oxirane compounds: cis-2,3-epoxybutane (c23EB), trans-2,3-epoxybutane (t23EB), 1,2-epoxybutane (12EB), 1,2,3,4-diepoxybutane (DEB), and 3,3-dimethylepoxybutane (33DMEB) on CH4 hydrate formation. Despite having a four-carbon backbone, these compounds differ in their 3D geometries. The structures and stabilities of CH4 hydrates containing each compound were analyzed using high-resolution powder diffraction, solid-state 13C NMR, and phase equilibrium measurements. The experimental results revealed that c23EB, 12EB, and 33DMEB act as sII/sH hydrate formers and thermodynamic promoters, whereas t23EB and DEB have opposite roles. These results were analyzed in relation to the 3D geometries and relative stabilities of various rotational isomers using DFT calculations. Hydrate structure was influenced by both the length and thickness of the added compounds. Moreover, an appropriate level of (not excessive) hydrophilicity induced by an oxirane group appeared to enhance the thermodynamic stability of the hydrates. This study provides insights into how the chemical nature of additives influences the structure and stability of clathrate hydrates.

Phase equilibrium conditions in carbon dioxide + cyclopentane double clathrate hydrate forming system coexisting with sodium chloride aqueous solution

The four-phase equilibrium conditions were measured in carbon dioxide + cyclopentane double clathrate hydrate forming systems coexisting with either sodium chloride aqueous solution or pure water as a technological basis for developing seawater desalination technology utilizing clathrate hydrate formation and decomposition. The equilibrated phases included sodium chloride aqueous solution or pure water, carbon dioxide + cyclopentane double clathrate hydrate, liquid cyclopentane, and carbon dioxide gas. The experiments were performed using the batch isochoric procedure. Three different concentrations of sodium chloride in the aqueous solution were tested: 0.035, 0.070, or 0.105 in mass fraction. Pressures ranged from 0.385 MPa to 2.488 MPa. The results were compared with the equilibrium conditions for carbon dioxide and cyclopentane simple clathrate hydrate forming systems. The comparison revealed that the double clathrate hydrate is more thermodynamically stable than the simple clathrate hydrates, under a given sodium chloride concentration in the aqueous solution.

Elucidating the molecular mechanism of water migration in myosin gels of Nemipterus virgatus during low pressure coupled with heat treatment

The relationship between myosin denaturation, aggregation and water migration in Nemipterus virgatus myosin gels with different treatment processes under optimal low pressure coupled with heat treatment was investigated to clarify the molecular mechanism of water migration. With the different treatment processes, the proportion of bound water of the myosin gels increased significantly (P < 0.05). Denaturation of myosin S1 sub-fragments and α-helical unfolding during different treatment processes led to an increase in β-sheets content. These promote increased exposure of Try residues and hydrophobic groups of myosin, formation of clathrate hydrates, and reduced mobility of bound water. Furthermore, hydrophobic interactions and disulfide bonds caused the head-head and head-hinge to coalesce into a 3D honeycomb network with greater fractal dimension, less lacunarity, smaller water hole diameter and more water holes. This increased the capillary pressure experienced by the bound water, causing immobile water to migrate towards the bound water. The present study may be necessary to improve the mechanism of water migration in protein gel systems and to promote the industrial application of high pressure processing technology in surimi-based foods.

Understanding the influences of different associated gas impurities and the kinetic modelling of biogas hydrate formation at the molecular scale

The biological degradation of organic waste generates biogas that mostly comprises a mixture of CH4 and CO2. The separation of CO2 and other gas impurities from CH4 using a hydrate-based technique has recently gained interest as an option. The captured CO2 and impurities can then be sequestered in natural gas hydrate (NGH) geological sites leading to an exchange of the in situ CH4 hydrate over to CO2-dominated hydrate and a simultaneous CH4 release from these huge natural sources of energy in permafrost sediments. Consequently, the effects of associated gas impurities such as SO2, H2S, N2, and H2 on either hydrate-based biogas purification or residual sequestration in NGH deposits need to be well-understood. In this work, the influence of different biogas compositions on the process of clathrate hydrate formation using molecular dynamics (MD) simulations was investigated. Additionally, a kinetic model for predicting the progress of biogas crystal growth based on the formation of the number of hydrogen bonds as well as total energy is proposed. The results elucidate that the concentration of dissolved gas in liquid water at the solid-solution interface is one of the key controllers of the growth rate but it has less impact on the filling percentage of formed both types the clathrate hydrate cages. The presence of H2S and SO2 molecules was found to slightly increase the formation of biogas hydrate. On the other hand, N2, and H2 molecules reduce the rate of biogas hydrate generation.

Crystallization-driven evolution of water occurrence states with implications on dewaterability improvement of waste-activated sludge

This study proposed to improve the dewaterability of waste-activated sludge (WAS) through crystallization-driven evolution of water occurrence states. Primarily, the feasibility of clathrate hydrate (i.e., CO2 hydrate) formation in WAS was examined. The thermodynamic analysis indicated that the CO2 hydrate formation with the excessive water in WAS followed pseudo-first-order kinetics, and fit of the data yielded a kobs value of 3.905 × 10−5 L∙mol−1∙s−1 for 274.15 K. With the water conversion efficiency of 100%, the crystallization-dissociation process of CO2 hydrate significantly improved the dewaterability of WAS in term of capillary suction time (CST) decreasing from 251.5 s to 57.4 s. Also, the relief of gas pressure can induce the hydrate dissociation, which creates a novel way to recycle CO2 gas and save the consumption of chemicals required by sludge dewatering process. Regarding the mechanism of hydrates-based sludge dewatering, the evolution of water occurrence state was investigated. The in-situ synchrotron X-ray computed microtomography visually analyzed the micro-scale porosity and interstitial water of WAS flocs. The model of three-dimensional pore structure was established and the porosity parameters of solid aggregates were determined. It was found that the volume of connected pores and the total pore volume fraction of solid compositions increased. But the mean volume and mean area of isolated pores simultaneously decreased by 14.6% and 12.4%, respectively, which meant that the steric hindrance caused by isolated pores was weakened due to the reduced solid-water contact area. In addition, the crystallization of water caused the reformation of conformation arrangement of vicinal water and solid molecules, which highly organized the water molecules into the crystal structure. Accordingly, an estimation method for vicinal water layer thickness was developed based on atom force microscope. The thickness of vicinal water layer was found to be reduced by 77.4% and the hydration repulsion among solid compositions was correspondingly weakened, which facilitated the aggregation of solid compositions, and the relatively separated hydrate phase and solid phase could be formed. All the above results open up a novel strategy for enhanced water-solid separation of WAS through the crystallization-driven evolution of water occurrence states. As distinguished from the conventional approaches, the hydrates-based sludge dewatering enhances the water-solid separation only with regulating the spatial arrangement of water-solid molecules, but without altering the chemical compositions. Thus, more chances can be created to increase the environmentally friendly attributes related to WAS dewatering.

Development and evaluation of aloe vera dry extract quantum dots as novel hydrate inhibitor for the control of flow assurance problems in the oilfields

Application of quantum dots in the oil and gas field operations is an emerging area, especially in tracer application and as hydrate inhibitors. This study involves development and evaluation of a novel low-dosage hydrate inhibitor aloe vera dry extract quantum dots, prepared by hydrothermal method, to prevent the formation of clathrate hydrates. Experimental studies were performed for THF model hydrate system in crude oil-water emulsion to evaluate the effect of wax content on hydrate formation. Quantum dots were tested for varying concentrations from 0.1 wt% to 1.0 wt% and the best result was obtained at 1.0 wt% in the experimental solutions. The quantum dots have shown the ability of anti-agglomerants, which allowed the tiny hydrate particles formed to remain dispersed in the experimental solution for a longer duration of time and also increased the induction time with increasing concentration of quantum dots. The study also revealed that presence of wax delayed the induction time of hydrate formation, but once hydrate formation occurred, the wax particles acted as nucleation sites for the agglomeration of more hydrate particles.

Enabling hydrate-based methane storage under mild operating conditions by periodic mesoporous organosilica nanotubes

Biomethane is a renewable natural gas substitute produced from biogas. Storage of this sustainable energy vector in confined clathrate hydrates, encapsulated in the pores of a host material, is a highly promising avenue to improve storage capacity and energy efficiency. Herein, a new type of periodic mesoporous organosilica (PMO) nanotubes, referred to as hollow ring PMO (HR-PMO), capable of promoting methane clathrate hydrate formation under mild working conditions (273 K, 3.5 MPa) and at high water loading (5.1 g water/g HR-PMO) is reported. Gravimetric uptake measurements reveal a steep single-stepped isotherm and a noticeably high methane storage capacity (0.55 g methane/g HR-PMO; 0.11 g methane/g water at 3.5 MPa). The large working capacity throughout consecutive pressure-induced clathrate hydrate formation-dissociation cycles demonstrates the material’s excellent recyclability (97% preservation of capacity). Supported by ex situ cryo-electron tomography and x-ray diffraction, HR-PMO nanotubes are hypothesized to promote clathrate hydrate nucleation and growth by distribution and confinement of water in the mesopores of their outer wall, along the central channels of the nanotubes and on the external nanotube surface. These findings showcase the potential for application of organosilica materials with hierarchical and interconnected pore systems for pressure-based storage of biomethane in confined clathrate hydrates.

Existence of Acetaldehyde Clathrate Hydrate and Its Dissociation Leading to Cubic Ice under Ultrahigh Vacuum and Cryogenic Conditions.

Acetaldehyde in a dilute aqueous solution gets hydrated to produce a geminal diol under atmospheric conditions. The acetaldehyde-water ice system under high pressure also converts to a geminal diol, and therefore, its stable clathrate hydrate (CH) phase, which in most systems forms at high pressures, is unknown. In the present study, we showed that acetaldehyde CH exists in ultrahigh vacuum (10-10 mbar) under cryogenic conditions (below 140 K) and continues to exist at 115 K for periods well over 1 day. Decomposition of acetaldehyde CH at 130-135 K produces water ice in its cubic crystalline form. The mechanism and kinetics involved in the process have also been studied. Reflection absorption infrared spectroscopy and temperature-programmed desorption mass spectrometry were utilized to confirm the CH formation. Our study establishes the possibility of a stable CH phase for acetaldehyde in interstellar and cometary environments.

Molecular dynamics simulations to investigate the effects of organic amines on biogas clathrate hydrate formation

The biological degradation of organic wastes mostly generates biogas including CO2 and CH4. Since both gases may be utilized as feedstock for various industrial applications, the alternative of gas hydrates to separate or enrich such gas species is of particular interest. To promote the hydrate-based (HB) methods, introducing environmentally friendly promoters could either enhance the formation or improve the recovery rates. In this study, the effects of pure and binary organic amines (methylamine, dimethylamine, amylamine) and urea on the kinetics of CO2 + CH4 hydrate formation through molecular dynamics simulations were explored. To characterize the kinetics of biogas hydrate formation, different analyses such as the three/four-body structural order parameters, determination of hydrate-like cages, number of hydrogen bonds, molecular distributions, and energy variations were investigated. Results indicate that the promotion effects of organic molecules were evident in which the presence of methylamine, dimethylamine, and their mixture was found to be more kinetically efficient than other studied solution systems. These molecules can also induce guest gases toward being located inside the formed cages more than in pure water. Studied molecules can also affect the distribution of CO2 and CH4 molecules during the conversion of the solution phase to a clathrate-like state which could be a useful feature to intensify the split fraction of HB processes. Nonetheless, the addition of urea in either a pure or binary mixture with other amine molecules was not recognized as the observed efficiency of combined methylamine and dimethylamine. This investigation reveals the uncovered characteristics regarding the utilization of long/short-chain amines to upgrade the process of biogas separation through hydrate.