Hydrate Film Research Articles

Three-Scale in Situ Investigation on the Film Morphology and Mass Transfer Channels during the Thickening Growth of Hydrates on Gas Bubble

A three-scale in situ observation technique combining the optical microscope, confocal microscope, and Raman spectroscopy was proposed to gain insights into the thickening growth kinetic of hydrate film formed on a gas bubble suspended in water. The evolution of the morphology and mass transfer channels of the hydrate films formed from pure CH4 or the mixture of CH4 and C2H6 during thickening growth was investigated. Results demonstrated that the morphological evolution of hydrate films during thickening growth depended on the initial morphology of the hydrate film formed in the lateral growth. The sI CH4 and sI CH4–C2H6 hydrates had the same ultimate morphology (e.g., a large number of well-defined polyhedral granular hydrates), while the sII CH4–C2H6 hydrates appeared massive. It was clearly observed that the gas pores on the hydrate film gradually vanished with the growth of hydrate film, which suggested that the predominant mass transfer channels on the film changed from the gas pores to the lattices....

Growth kinetics of hydrate formation from water–hydrocarbon system

Abstract Gas hydrates have drawn global attentions in the past decades as potential energy resources. It should be noted that there are a variety of possible applications of hydrate-based technologies, including natural gas storage, gas transportation, separation of gas mixture, and seawater desalination. These applications have been critically challenged by insufficient understanding of hydrate formation kinetics. In this work, the literatures on growth kinetic behaviors of hydrate formation from water-hydrocarbon were systematically reviewed. The hydrate crystal growth, hydrate film growth and macroscopic hydrate formation in water system were reviewed, respectively. Firstly, the hydrate crystal growth was analyzed with respect to different positions, such as gas/liquid interface, liquid–liquid interface and gas–liquid–liquid system. Secondly, experimental and modeling studies on the growth of hydrate film at the interfaces between guest phase and water phase were categorized into two groups of lateral growth and thickening growth considering the differences in growth rates. Thirdly, we summarized the promoters and inhibitors reported (biological or chemical, liquid or solid and hydrophobic or hydrophilic) and analyzed the mechanisms affecting hydrate formation in bulk water system. Knowledge gaps and suggestions for further studies on hydrate formation kinetic behaviors are presented.

Environmentally Friendly Production of Methane from Natural Gas Hydrate Using Carbon Dioxide

Huge amounts of natural gas hydrate are trapped in an ice-like structure (hydrate). Most of these hydrates have been formed from biogenic degradation of organic waste in the upper crust and are almost pure methane hydrates. With up to 14 mol% methane, concentrated inside a water phase, this is an attractive energy source. Unlike conventional hydrocarbons, these hydrates are widely distributed around the world, and might in total amount to more than twice the energy in all known sources of conventional fossil fuels. A variety of methods for producing methane from hydrate-filled sediments have been proposed and developed through laboratory scale experiments, pilot scale experiments, and theoretical considerations. Thermal stimulation (steam, hot water) and pressure reduction has by far been the dominating technology platforms during the latest three decades. Thermal stimulation as the primary method is too expensive. There are many challenges related to pressure reduction as a method. Conditions of pressure can be changed to outside the hydrate stability zone, but dissociation energy still needs to be supplied. Pressure release will set up a temperature gradient and heat can be transferred from the surrounding formation, but it has never been proven that the capacity and transport ability will ever be enough to sustain a commercial production rate. On the contrary, some recent pilot tests have been terminated due to freezing down. Other problems include sand production and water production. A more novel approach of injecting CO2 into natural gas hydrate-filled sediments have also been investigated in various laboratories around the world with varying success. In this work, we focus on some frequent misunderstandings related to this concept. The only feasible mechanism for the use of CO2 goes though the formation of a new CO2 hydrate from free water in the pores and the incoming CO2. As demonstrated in this work, the nucleation of a CO2 hydrate film rapidly forms a mass transport barrier that slows down any further growth of the CO2 hydrate. Addition of small amounts of surfactants can break these hydrate films. We also demonstrate that the free energy of the CO2 hydrate is roughly 2 kJ/mol lower than the free energy of the CH4 hydrate. In addition to heat release from the formation of the new CO2 hydrate, the increase in ion content of the remaining water will dissociate CH4 hydrate before the CO2 hydrate due to the difference in free energy.

Metal Insulator Transition in Vanadium Dioxide Hydrated by Means of the Plasma-Immersion Ion Implantation Method

In the work, we explore the modification of the structure of vanadium dioxide films, as well as the metal-semiconductor phase transition in them, when hydrated by the method of plasma-immersion ion implantation. Based on a detailed X-ray analysis and the Raman spectra of the initial and hydrated films, it is shown that the plasma-ion modification of the transition and the metallization of vanadium dioxide (at a hydrogen concentration above 10at. %) are most likely associated with electron-correlation effects amplified by hydrogen implantation and an increase in the free charge carrier density in the material.

FT-IR Spectroscopy for the Identification of Binding Sites and Measurements of the Binding Interactions of Important Metal Ions with Bovine Serum Albumin

Proteins play crucial roles in the transportation and distribution of therapeutic substances, including metal ions in living systems. Some metal ions can strongly associate, while others show low affinity towards proteins. Consequently, in the present work, the binding behaviors of Ca2+, Ba2+, Ag+, Ru3+, Cu2+ and Co2+ with bovine serum albumin (BSA) were screened. BSA and the metal ions were allowed to interact at physiological pH and their binding interactions were screened by using FT-IR spectroscopy. Spectra were collected by using hydrated films over a range of 4000–400 cm−1. The interaction was demonstrated by a significant reduction in the spectral intensities of the amide I (C=O stretching) and amide II bands (C–N stretching coupled to NH bending) of the protein after complexation with metal ions. The binding interaction was further revealed by spectral shifting of the amide I band from 1651 cm−1 (free BSA) to 1653, 1654, 1649, 1655, 1655, and 1654 cm−1 for BSA–Ca2+, BSA–Ba2+, BSA–Ag+, BSA–Ru3+, BSA–Cu2+ and BSA–Co2+ complexes, respectively. The shifting of the amide I band was due to the interactions of metal ions with the O and N atoms of the ligand protein. Estimation of the secondary protein structure showed alteration in the protein conformation, characterized by a marked decrease (12.9–40.3%) in the α-helix accompanied by increased β-sheet and β-turn after interaction with the metal ions. The interaction results of this study were comparable with those reported in our previous investigation of metal ion–BSA interactions using affinity capillary electrophoresis (ACE), which has proven the accuracy of the FT-IR technique in the measurement of interactions between proteins and metal ions.

Research on the heat and mass transfer mechanisms for growth of hydrate shell from gas bubbles

AbstractAs a fundamental study for hydrate utilization technologies, hydrate growth is a complicated rate‐limiting process controlled by heat and mass transfer mechanisms. Generally, the experimental data of hydrate shell lateral growth in the literature are compiled based on the system subcooling, while those of hydrate shell vertical growth are compiled based on the molecular mobility of the hydrate formers and water. In this study, we quantitatively investigate the dominating factors for hydrate film growth considering the opposite mass or heat transfer limitations, which can explain the observed phenomena from the literature more comprehensively. Firstly, a model is derived to describe the lateral growth of hydrate shell considering the convective mass transfer and effective concentration driving force at the film front. It can demonstrate the important effects of subcooling and other system factors such as gas type, aqueous solution, and system pressure on hydrate shell lateral growth. Secondly, an improved self‐similar model is presented to simulate the process of hydrate shell thickening considering the heat transfer limitation. The simulation results indicate that the hydrate shell growth rate decreases with a decrease in the subcooling and an increase in the bubble radius.

Study of transport phenomena between H<sub>2</sub>O and CO<sub>2</sub> via CO<sub>2</sub>hydrate film

Study of transport phenomena between H<sub>2</sub>O and CO<sub>2</sub> via CO<sub>2</sub>hydrate film

A Novel Soft Contact Piezo-Controlled Liquid Cell for Probing Polymer Films under Confinement using Synchrotron FTIR Microspectroscopy

Soft polymer films, such as polyelectrolyte multilayers (PEMs), are useful coatings in materials science. The properties of PEMs often rely on the degree of hydration, and therefore the study of these films in a hydrated state is critical to allow links to be drawn between their characteristics and performance in a particular application. In this work, we detail the development of a novel soft contact cell for studying hydrated PEMs (poly(sodium 4-styrenesulfonate)/poly(allylamine hydrochloride)) using FTIR microspectroscopy. FTIR spectroscopy can interrogate the nature of the polymer film and the hydration water contained therein. In addition to reporting spectra obtained for hydrated films confined at the solid-solid interface, we also report traditional ATR FTIR spectra of the multilayer. The spectra (microspectroscopy and ATR FTIR) reveal that the PEM film build-up proceeds as expected based on the layer-by-layer assembly methodology, with increasing signals from the polymer FTIR peaks with increasing bilayer number. In addition, the spectra obtained using the soft contact cell indicate that the PEM film hydration water has an environment/degree of hydrogen bonding that is affected by the chemistry of the multilayer polymers, based on differences in the spectra obtained for the hydration water within the film compared to that of bulk electrolyte.

Effect of annealing treatment on transparent and conductive hydrated magnesium-carbon films

Transparent electronic technology has many urgent optoelectronic device applications. A key component of plasmonic materials in conventional semiconductors is the wide band gap of oxide thin films. Although transparent electronic materials have been developed for visible and near-infrared wavelengths, systems incorporating mid-infrared and far-infrared spectra are difficult to achieve. In this study, hydrated magnesium-carbon films, a new type of non-oxide transparent conductive thin films with a magnesium hydroxide structure, were generated using the three-step method. After annealing treatment, larger crystals in the thin films typically exhibited superior film resistivity, with conductivity values of approximately 8.63 × 10−3 Ω m. Due to the free electron concentration was not more than 1020 cm−3, the films demonstrated excellent optical properties, with plasma wavelength values of approximately 8 μm for infrared transmittance above 70%. After annealing, due to the Moss-Burstein (M-B) effect, the visible light transmittance was greater than 85% and the optical bandgap shifted towards the blue region. In addition, the influences of the sputtering power of the carbon target on the properties of hydrated magnesium-carbon film were also discussed in this paper.

Adsorption of ammonia nitrogen on lignite and its influence on coal water slurry preparation

Using lignite as an adsorbent and subsequently as a material for coal water slurry (CWS) preparation represents an alternative method for coal chemical wastewater treatment. However, the components in these wastewaters could affect the CWS performance, especially ammonia nitrogen (NH4+-N). The influencing mechanism of NH4+-N was studied through adsorption method. Associated with adsorption reaction model, Fourier transform infrared spectrum and zeta potential detection, it was found that the adsorption reaction of NH4+-N, driven by ion-exchange interactions with H+ of –OH and –COOH on the lignite surface, displayed a typical monolayer mode and was much faster than that of NSF which displayed a double-layer mode and was adsorbed preferentially at hydrophobic sites. In binary adsorption, the adsorption amount of NSF was increased remarkably by adding NH4+-N. This was attributed to the modified lignite surface and hydrophilic group by NH4+-N that decreased the surface electronegativity as well as the electrostatic repulsion among –SO3− in NSF molecules. The enhanced adsorption of NSF resulted in capturing more water molecules in hydration film surrounding the particles in CWS. The hydration film was then thickened and stabilized, thus leading to a decrease in free water for CWS flowing. As a result, the apparent viscosity was increased, and CWS tended to be dilatant. In addition, the thickened and stabilized hydration film also increased the yield stress of CWS prepared with NH4+-N, resulting in improved stability.

Molecular simulation study on hydration of low-rank coal particles and formation of hydration film

Molecular simulation study on hydration of low-rank coal particles and formation of hydration film

The effect of NaCl concentration and corrosion on cohesion/adhesion forces of structure-II hydrate particles

Gas hydrates are ice-like solid compounds formed from water and suitably sized gas molecules under high pressure and low temperature conditions. In typical oil and gas transportation flowlines, when water is present gas hydrates particles can form, agglomerate, and accumulate in the flowlines. These particles can also deposit on flowline walls during fluid flow or during shut-in/restart conditions. The formation of hydrate plugs can cause a blockage in the flowline, as well as other safety concerns. Although researchers have studied how temperature and annealing time would affect the cohesion/adhesion forces between hydrate particles and particle-surface systems, the effects of surface corrosion, salinity and water amount on the adhesion force have not been reported. Deep-water flowlines typically contain brine, and water condensation and corrosion can occur on flowline walls. A water layer and corrosion on flowline walls can affect hydrate film growth and deposition, and salt dissolved in the liquid phase may also influence the agglomeration of hydrate particles. Thus, the effects of free water, corrosion and salt on CH4/C2H6 hydrate particle-particle and particle-surface micromechanical forces are essential for advancing the understanding on hydrate agglomeration and deposition mechanisms in gas dominated deep-water pipelines. In order to investigate the mechanism of gas hydrate deposition and agglomeration in gas dominated flowlines, a high-pressure micromechanical force (MMF) apparatus was applied to directly measure CH4/C2H6 hydrate adhesion/cohesion forces. The influence of NaCl concentration on the cohesion force between CH4/C2H6 hydrate particles was studied, and the effect of surface corrosion on adhesion forces between hydrate particles and carbon steel (CS) were analysed. It was found that the presence of NaCl decreased the cohesion force between hydrate particles, and a possible explanation of this phenomenon was given based on the capillary liquid bridge model. For the adhesion force measurements, the results indicated that with increasing visual corrosion, the adhesion force between gas hydrate particle and CS surface increased by up to 500%.

Visual Studies of Methane Hydrate Formation on the Water–Oil Boundaries

Visual studies of the growth of methane hydrate at the interface of water with three kinds of methane-saturated crude oils were performed at supercooling ∼20 °C. The results were compared with the growth of methane hydrate at the interfaces of water–methane and water–methane-saturated decane or toluene. The average rates of hydrate film growth measured for the water–oil interfaces vary within the range of 0.8–1.0 mm s–1, which is somewhat lower than the average growth rate at the water–methane and water–decane (toluene) interfaces (1.6 mm s–1). It was found that in some cases hydrate nucleation proceeded not on the water–oil boundary but at the walls of the cell. Spontaneous intrusion of oil formations (drops, serpentlike formations) into the aqueous phase was observed in some experiments. These formations are likely to originate from oil catching by the bundles of needlelike hydrate crystals due to the capillary effect. Intense growth of the hydrate on the walls of the cell was observed for two kinds of ...

Carbon dioxide hydrate formation with SDS: Further insights into mechanism of gas hydrate growth in the presence of surfactant

The capillary-driven mechanism of gas hydrate growth after their nucleation in the presence of surfactants under quiescent conditions is well-known for methane and other hydrocarbons gases but has not been observed previously for carbon dioxide (CO2). We have investigated the CO2 hydrate growth with sodium dodecyl sulfate (SDS) under different mass-transfer driving forces Δx, that is the difference between the equilibrium solubility of gas in liquid and the amount of gas dissolved in the liquid (mole concentration) in equilibrium with the hydrate. The kinetics data on gas consumption and the results of microscopic investigation of the hydrate film growth at the gas-liquid interface as well as hydrate growth in the bulk liquid and in the gas phase upward from the gas-liquid interface (the capillary-driven growth) are presented. An effect of the driving force on the CO2 hydrate formation was examined. It was found that under the large driving force (Δx ≥ 5.0 × 10−3), SDS additives in the concentration of 100, 1000 and 5000 ppm had no effect on the mechanism and kinetics of the CO2 hydrate growth. For the small driving force (Δx ≤ 1.0 × 10−3) and the SDS concentration of 1000 ppm the capillary-driven growth of CO2 hydrates was observed for the first time. The amount of the water converted into the hydrate during the capillary-driven growth of CO2 hydrates without stirring in the presence of 1000 ppm SDS achieved about 90%.

Development and evaluation of palonosetron loaded mucoadhesive buccal films

Clinical potential of palonosetron in oral therapy is mainly limited by low permeability. The purpose of this study was to develop oral mucoadhesive film with palonosetron and evaluate its prospective for buccal delivery. Films were prepared by solvent casting method using proloc 15 and eudragit® RL 100 polymers. The composition of polymers and plasticizers were optimized and evaluated for physicomechanical properties, mucoadhesion, swelling, drug release and permeation across mucosal membrane. The drug loaded films (F1-F4) demonstrated desirable physical properties, mechanical strength and mucoadhesion. Rapid hydration of films was observed which may provide prompt mucoadhesion of film with the buccal mucosa. A biphasic drug release profile was noticed in films (F1-F4), with greater amount being released in 2 h. Ex vivo studies using films (F3 and F4 with 0.25 mg and 0.5 mg palonosetron per cm2, respectively) showed greater transport when drug concentration was high. Scanning electron microscopy image shows that drug loaded film possesses morphological features of an ideal film. In conclusion, our data demonstrated that, buccal films has the potential to provide effective transport of drug through the buccal mucosa and could be an option for palonosetron delivery.

Effect of hydration on microstructure and property of anodized oxide film for aluminum electrolytic capacitor

Etched aluminum foil for aluminum electrolytic capacitor was first boiled in water for different time to form hydrous film on Al foil and then anodized in H3BO4 solution at 530 V to form anodic oxide barrier film as insulating dielectric layer. The obtained films were characterized by field-emission scanning electron microscopy, transmission electron microscope and X-ray diffraction for surface morphology, microstructure and crystallinity examination. Small-current charging, LCR meter and electrochemical impedance spectroscopy were exploited to measure the propertied of the anodized oxide film such as withstanding voltage (Uw), specific resistance (Rox) and specific capacitance (Cs and Cox) for its electrochemical performance. The results show that the hydrous film is pseudoboehmite (PB) with a dense inner layer and a fibrous outer layer. The crystallinity of the PB film increases with hydration time. During anodization, the PB film was transformed into anodic oxide (γ′-Al2O3) barrier film. Prolonging hydration time promotes transformating PB into γ′-Al2O3 and improves the crystallinity of the barrier film, leading to increase in Cs and Cox and decrease in Rox and Uw.

Long-term viability of carbon sequestration in deep-sea sediments.

Sequestration of carbon dioxide in deep-sea sediments has been proposed for the long-term storage of anthropogenic CO2 that can take advantage of the current offshore infrastructure. It benefits from the negative buoyancy effect and hydrate formation under conditions of high pressure and low temperature. However, the multiphysics process of injection and postinjection fate of CO2 and the feasibility of subseabed disposal of CO2 under different geological and operational conditions have not been well studied. With a detailed study of the coupled processes, we investigate whether storing CO2 into deep-sea sediments is viable, efficient, and secure over the long term. We also study the evolution of multiphase and multicomponent flow and the impact of hydrate formation on storage efficiency. The results show that low buoyancy and high viscosity slow down the ascending plume and the forming of the hydrate cap effectively reduces permeability and finally becomes an impermeable seal, thus limiting the movement of CO2 toward the seafloor. We identify different flow patterns at varied time scales by analyzing the mass distribution of CO2 in different phases over time. We observe the formation of a fluid inclusion, which mainly consists of liquid CO2 and is encapsulated by an impermeable hydrate film in the diffusion-dominated stage. The trapped liquid CO2 and CO2 hydrate finally dissolve into the pore water through diffusion of the CO2 component, resulting in permanent storage. We perform sensitivity analyses on storage efficiency under variable geological and operational conditions. We find that under a deep-sea setting, CO2 sequestration in intact marine sediments is generally safe and permanent.

Effect of silica sand size and saturation on methane hydrate formation in the presence of SDS

Abundant reserves of natural gas hydrates are hosted in the pores of sediment layers, and the hydrate-based technology could be widely used in industry. In this work, the formation kinetics of methane hydrate in a complex system containing silica sand and 300-ppm sodium dodecyl sulfate (SDS) solution were investigated at 275.15 K and 7 MPa. The hydrate was formed in different-saturated silica sand with particle sizes of 100, 150, 200, 300, and 400 mesh. The results indicated that in both the 50%- and 100%-saturated sand, a larger particle size exhibited a better methane storage capacity. In the complex system, the presence of SDS molecules significantly enhanced the hydrate formation process and weakened the effect of particle size on the hydrate formation rate. The difference in hydrate gas uptake formed in the differently saturated silica sand indicted that with an increase in saturation, the smaller-sized silica sands caused a more marked inhibitory effect. Finally, the different hydrate distributions in the 50%- and 100%-saturated silica sand revealed that a hydrate film formed quickly and preferentially on the surface of the silica sand, which was attributed to the adsorption of the SDS active groups and the presence of the silica sand surface. With the thickening of the hydrate film, the resulting volume expansion and stronger capillary force led to the migration of the liquid phase, which resulted in the hydrate distributions observed in the differently saturated silica sands.

Hydration film measurement on mica and coal surfaces using atomic force microscopy and interfacial interactions

The hydration film on particle surface plays an important role in bubble-particle adhesion in mineral flotation process. The thicknesses of the hydration films on natural hydrophobic coal and hydrophilic mica surfaces were measured directly by atomic force microscopy (AFM) based on the bending mode of the nominal constant compliance regime in AFM force curve in the present study. Surface and solid-liquid interfacial energies were calculated to explain the forming mechanism of the hydration film and atomic force microscopy data. The results show that there are significant differences in the structure and thickness of hydration films on coal and mica surfaces. Hydration film formed on mica surface with the thickness of 22.5 nm. In contrast, the bend was not detected in the nominal constant compliance regime. The van der Waals and polar interactions between both mica and coal and water molecules are characterized by an attractive effect, while the polar attractive free energy between water and mica (−87.36 mN/m) is significantly larger than that between water and coal (−32.89 mN/m), which leads to a thicker and firmer hydration layer on the mica surface. The interfacial interaction free energy of the coal/water/bubble is greater than that of mica. The polar attractive force is large enough to overcome the repulsive van der Waals force and the low energy barrier of film rupture, achieving coal particle bubble adhesion with a total interfacial free energy of −56.30 mN/m.

The enhanced flotation of coal by nanosilica particles

ABSTRACT It is well known that the stability of hydration film on the particle surface affected the particle-bubble attachment in a flotation process. In this paper, the effect of attached nanosilica particles on the stability of liquid film around the coal particles was investigated by measurements of viscosity of the coal pulp and the bubble attachment time for coal particles. The interaction energy between a nanosilica particle and a coal particle was calculated using the EDLVO theory. Results showed that the nanosilica-coal attachment was driven by hydration attraction. And the stability of liquid film was weakened with the attachment of nanosilica particles, which is probably due to the change of surface roughness. In this case, the bubble-particle attachment time was reduced and further improved the flotation recovery of coal.