Carbon Dioxide Clathrate Hydrate Research Articles

Exploring High‐Pressure Polymorphism in Carbonic Acid through Direct Synthesis from Carbon Dioxide Clathrate Hydrate

AbstractCarbon dioxide (CO2) is widespread in astrochemically relevant environments, often coexisting with water (H2O) ices and thus triggering a great interest regarding the possible formation of their adducts under various thermodynamic conditions. Amongst them, solid carbonic acid (H2CO3) remains elusive, yet being widely studied. Synthetic routes followed for its production have always been characterised by drastic irradiation on solid ice mixtures or complex procedures on fluid samples (such as laser heating at moderate to high pressures). Here we report about a simpler yet effective synthetic route to obtain two diverse carbonic acid crystal structures from the fast, cold compression of pristine clathrate hydrate samples. The two distinct polymorphs we obtained, differing in the water content, have been deeply characterised via spectroscopic and structural techniques to assess their composition and their astonishing pressure stability, checked up to half a megabar, also highlighting the complex correlations between them so to compile a detailed phase diagram of this system. These results may have a profound impact on the prediction and modelisation of the complex chemistry which characterises many icy bodies of our Solar System.

Exploring High-Pressure Polymorphism in Carbonic Acid through Direct Synthesis from Carbon Dioxide Clathrate Hydrate.

Carbon dioxide (CO2) is widespread in astrochemically relevant environments, often coexisting with water (H2O) ices and thus triggering a great interest regarding the possible formation of their adducts under various thermodynamic conditions. Amongst them, solid carbonic acid (H2CO3) remains elusive, yet being widely studied. Synthetic routes followed for its production have always been characterised by drastic irradiation on solid ice mixtures or complex procedures on fluid samples (such as laser heating at moderate to high pressures). Here we report about a simpler yet effective synthetic route to obtain two diverse carbonic acid crystal structures from the fast, cold compression of pristine clathrate hydrate samples. The two distinct polymorphs we obtained, differing in the water content, have been deeply characterised via spectroscopic and structural techniques to assess their composition and their astonishing pressure stability, checked up to half a megabar, also highlighting the complex correlations between them so to compile a detailed phase diagram of this system. These results may have a profound impact on the prediction and modelisation of the complex chemistry which characterises many icy bodies of our Solar System.

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.

Timing and Abundance of Clathrate Formation Control Ocean Evolution in Outer Solar System Bodies: Challenges of Maintaining a Thick Ocean within Pluto

Clathrate hydrates may represent a sizable fraction of material within the icy shells of Kuiper Belt objects and icy moons. They influence the chemical and thermal evolution of subsurface oceans by locking volatiles into the ice shell and by providing more thermal insulation than pure water ice. We model the formation of these crystalline compounds in conditions relevant to outer solar system objects, using Pluto as an example. Although Pluto may have hosted a thick ocean in its early history, Pluto’s overall heat budget is probably insufficient to preserve liquid today if its outer shell is pure water ice. One previously proposed reconciliation is that Pluto’s ocean has a winter jacket: an insulating layer of methane clathrate hydrates. Unfortunately, assessments of the timing, quantity, and type of clathrate hydrates forming within planetary bodies are lacking. Our work quantifies the abundance of clathrate-forming gases present in Pluto’s ocean from accreted ices and volatiles released during thermal metamorphism throughout Pluto’s history. We find that if Pluto formed with the same relative abundances of ices found in comets, then a buoyant layer of mixed methane and carbon dioxide clathrate hydrates may form above Pluto’s ocean, though we find it insufficient to preserve a thick ocean today. In general, our study provides methodology for predicting clathrate formation in ocean worlds, which is necessary to predict the evolution of the ocean’s composition and whether a liquid layer remains at present.

Thermodynamic modeling for ternary clathrate hydrates of carbon dioxide, nitrogen and tetrahydrofuran

Hydrate-based CO2 separation technology is one of research hotspots in the field of Carbon Capture, Utilization, and Storage. However, thermodynamics, such as phase temperature and pressure, are very important for CO2 separation. In this study, a thermodynamic model was developed for calculating the temperature, pressure, separation efficiency and separation factor of the CO2-N2-THF/H2O system at the three-phase equilibrium of vapor–liquid-hydrates (V-L-H). The Chen-guo model was applied for the hydrate phase and the Patel-Teja equation of state (EOS) was used for the vapor phase. The Wilson activity coefficient model was employed for the liquid phase and the solubility of CO2 in solution was calculated using Henry's law. The average absolute deviation of the equilibrium pressure and temperature compared to the experimental data are 10.441% and 0.343%, respectively, which showed that the predicted three-phase equilibrium pressure and temperature were in good agreement with the experimental results. The three-phase equilibrium temperature and pressure of CO2 and N2 gas mixture in pure water and in THF aqueous solutions were compared. The results showed that THF had a promotion effect in reducing temperature and pressure of CO2 hydrate formation.

May sediments affect the inhibiting properties of NaCl on CH4 and CO2 hydrates formation? an experimental report

The equilibria of methane and carbon dioxide clathrate hydrates were measured in presence of a pure-quartz porous sand, with and without NaCl. Two different salt concentrations were tested: 0.030 and 0.037 wt%. Results were compared with phase equilibrium data already present in literature for these species. Despite salt, the porous medium was found to promote the process, mainly for the increased surface/volume ratio and for the improved heat transfer. In presence of salt, sand affected the process differently as a function of temperature: at values higher than 3 – 5 °C, it promoted the process, while for values lower than this range, but still greater than the ice-point, it acted as an inhibitor. However, these results can be considered true only for temperatures above the ice point. Due to similarity of ice water with clathrate hydrates, Raman microscale measurements were performed to gather information about the influence of sediments, salt, and temperature on OH-stretching vibrations of water. The obtained results allowed to clarify how the addition of NaCl, and or sediments to liquid water, under different temperature conditions (15 °C and −15 °C), influenced the water hydrogen bonds. Specifically, the changes of OH-stretching vibrations, when correlated with the NaCl concentrations, demonstrated that the presence of sediments partially inhibited the salt effects in the ice water probably due to hydrophilic interactions with the silanol groups of sediments. SEM measurements showed morphological information on sediments and on ice in different experimental conditions.

Development of dual functional methodology for seawater desalination and salt manufacture by carbon dioxide hydrate formation

Clathrate-hydrate-based seawater desalination is a novel technology that is performed by reaction between seawater and guest compounds to obtain fresh water. This study proposed a dual functional methodology for seawater desalination and salt manufacture by using carbon dioxide clathrate hydrate. In this methodology, the clathrate hydrate formation continues until the concentration of electrolytes in unreacted brine reaches the saturated solubility for the salt precipitation. The visual observation of the clathrate hydrate formation and the salt precipitation coupled with the analysis utilizing the powder X-ray diffraction (PXRD) technique was implemented to demonstrate the methodology. The carbon dioxide clathrate hydrate formation was first performed with sodium chloride aqueous solution. The carbon dioxide clathrate hydrate crystals floated on high salinity water. This experiment was followed by the occurrence of the sodium chloride dihydrate precipitation upon the carbon dioxide clathrate hydrate formation. The formed compounds, carbon dioxide clathrate hydrate and sodium chloride dihydrate, were identified by PXRD analysis. The mass fraction of the compounds was also determined by PXRD.

In Situ X-Ray Diffraction Study on Hydrate Formation at Low Temperature in a High Vacuum

The condition for incorporating simple gases with H2O to form clathrate hydrates in protosolar nebula is a subject of topical interest. Methane and carbon dioxide clathrate hydrates have been specu...

Carbon dioxide clathrate hydrate formation at low temperature

Context.The formation and presence of clathrate hydrates could influence the composition and stability of planetary ices and comets; they are at the heart of the development of numerous complex planetary models, all of which include the necessary condition imposed by their stability curves, some of which include the cage occupancy or host–guest content and the hydration number, but fewer take into account the kinetics aspects.Aims.We measure the temperature-dependent-diffusion-controlled formation of the carbon dioxide clathrate hydrate in the 155–210 K range in order to establish the clathrate formation kinetics at low temperature.Methods.We exposed thin water ice films of a few microns in thickness deposited in a dedicated infrared transmitting closed cell to gaseous carbon dioxide maintained at a pressure of a few times the pressure at which carbon dioxide clathrate hydrate is thermodynamically stable. The time dependence of the clathrate formation was monitored with the recording of specific infrared vibrational modes of CO2with a Fourier Transform InfraRed spectrometer.Results.These experiments clearly show a two-step clathrate formation, particularly at low temperature, within a relatively simple geometric configuration. We satisfactorily applied a model combining surface clathration followed by a bulk diffusion–relaxation growth process to the experiments and derived the temperature-dependent-diffusion coefficient for the bulk spreading of clathrate. The derived apparent activation energy corresponding to this temperature-dependent-diffusion coefficient in the considered temperature range isEa= 24.7 ± 9.7 kJ mol−1. The kinetics parameters favour a possible carbon dioxide clathrate hydrate nucleation mainly in planets or satellites.

Incorporation of Ammonium Fluoride and Methanol in Carbon Dioxide Clathrate Hydrates and Their Significance for Hydrate-Based Gas Separation

Methanol is known as one of few small molecules that cannot stabilize a solid clathrate hydrate host lattice as a guest molecule in a simple hydrate phase. Recently, it was discovered 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. These doped phases were found to be able to incorporate strongly hydrophilic guests such as methanol. As the next step in testing the utility of these novel hydrates, we prepared NH4F-doped clathrates with simple CO2 and binary CO2 + methanol guest molecules and characterized these by powder X-ray diffraction (PXRD), Raman spectroscopy, and molecular dynamics (MD) simulations. From the PXRD analysis, it was confirmed that CO2 interacts more strongly with the NH4F-doped 512 cages than the 512 cages without dopants. The MD simulations supported the PXRD results by demonstrating a strong interaction between the O atom of CO2 and the dopant NH4+ in the small cages. The incorporation of methanol into the CO2 + methanol clathrates was confirmed by PXRD analysis. With low concentrations of methanol, this guest shows a preference for the 512 cages and may serve as a site blocker for the 512 cage that normally would be occupied by small molecules such as CH4 and N2 in hydrate-based gas separation (HGBS) processes. Phase boundary conditions for hydrate stability in CO2–NH4F–CH3OH– water were obtained, and it was determined that a solution of 5 mol % NH4F and 2.2 mol % CH3OH is a reasonable choice for operating an HBGS process. The present findings provide insight into the potential of the NH4F-doped hydrate lattice, aided by quantities of catalytic methanol, for use in HBGS processes.

Experimental measurement of carbon dioxide clathrate hydrate in the presence of adamantane and other water soluble and insoluble additives

In this communication, hydrate thermodynamic equilibrium data of adamantane + water + carbon dioxide, 10, 20 and 30 wt fractions of tert-butanol(2-methyl 2-propanol) + water + CO2, 4.5 and 14.5 wt fractions of 2,5-dihydrofuran + water + CO2, 15 and 20 wt fractions of 1,3,5-trioxane + water + CO2, methyl-tert-butyl-ether (MTBE) + water + CO2 and mix of 10 wt% 1,3,5-trioxane and 3.5 wt% 2,5-dihydrofuran + water + CO2 were measured in the pressure range of 1.5–3.5 MPa using isochoric pressure search method. This work took advantage of the Gibbs Phase rule for adamantane and MTBE without considering their weight fraction. The results showed that 1,3,5-trioxane and 2,5-dihydrofuran are good promoters, especially mix of them. 2-methyl 2-propanol acts as an inhibitor in the presence of CO2. Methyl-tert-butyl-ether and adamantane had no impact on CO2 clathrate hydrate.

Formation of carbon dioxide clathrate hydrate from amorphous ice with warming

To investigate the formation mechanisms of CO2 clathrate hydrate under vacuum conditions, infrared spectra of vapor-deposited H2OCO2 amorphous ice were measured. From analyses of variations in the spectral features with warming, remarkable changes were found at ∼100 K. The results indicate that the deposited amorphous ice is transformed into CO2 clathrate hydrate at around ∼100 K. From the results, a phase diagram of CO2 clathrate hydrate from vapor deposited amorphous ice was predicted. The results suggest the existence of pure CO2 clathrate hydrates in space.

Self-preservation effect modelling in hydrate systems using Lattice Dynamic methods

The thermodynamic properties of the carbon dioxide clathrate hydrate as well as hexagonal ice Ih have been calculated using Quasiharmonic Lattice Dynamic framework in connection with Molecular Dynamic methods in order to show the existence of the self-preservation effect in the carbon dioxide hydrates. The statistical thermodynamics theory has been applied to calculate the thermal expansion coefficients for hydrate and ice systems. The calculations clearly show that because the thermal expansion of the hydrate phase is limited by the thermal expansion of ice it is possible to keep the hydrate in a stable region within the phase diagram. The differences in thermal expansion should lead to the self-preservation effect with the application of additional pressure on the hydrate phase. This effect allows using the self-preservation effect for the storage and transportation of gas in the hydrate form.

Phase stability conditions of carbon dioxide and methane clathrate hydrates in the presence of KBr, CaBr2, MgCl2, HCOONa, and HCOOK aqueous solutions: Experimental measurements and thermodynamic modelling

Experimental data on dissociation conditions of carbon dioxide clathrate hydrate in the presence of KBr, CaBr2, MgCl2, HCOONa, and HCOOK aqueous solutions, as well as methane clathrate hydrate in the presence of HCOONa and HCOOK aqueous solutions have been measured and are reported in this study. Measurements were conducted in the temperature and pressure ranges of (266.9–285.8)K and (1.47–9.68)MPa, respectively, using an isochoric pressure-search method. Results reveal that at varying concentrations, the aqueous salt solutions have a satisfactory inhibition effects on both carbon dioxide and methane hydrate formation, causing a shift in the P-T (pressure–temperature) equilibrium cruves to higher pressures and lower temperatures. A thermodynamic model based on the solid solution theory of van der Waals and Platteeuw (vdW-P) was used for estimation of hydrate dissociation conditions in the presence of the salt aqueous solutions. The gas phase was modeled using the Valderrama modification of the Patel-Teja equation of state (VPT EoS). The UNIQUAC approach, along with the Debeye-Huckel method, was applied to calculate the activity coefficient of water in the presence of salt. The UNIQUAC interaction parameters between water and anions and cations were optimized using the measured hydrate dissociation data. The model results provide a reasonable agreement with the experimental data, with an average absolute deviation (ARD%) below 0.3%.

Thermodynamic modeling of phase equilibrium of carbon dioxide clathrate hydrate in aqueous solutions of promoters and inhibitors suitable for gas separation

AbstractGas hydrates of CO2 in the presence of tetra‐n‐alkyl ammonium bromide (TBAB) and tetrahydrofuran (THF) show potential applications for storage. Prediction of the phase behavior of these systems is an important precursor for their successful application. In this work, a thermodynamic model is developed to predict phase equilibrium of CO2 hydrates in the presence of TBAB and THF aqueous solutions. In this work, the van der Waals and Platteeuw model is used to model the hydrate phase stability. The fugacity of hydrate former and that of water is calculated from the Peng–Robinson equation of state and the Pitzer–Mayorga–Zavitsas hydration (PMZH) model for TBAB and nonrandom two‐liquid (NRTL) models for the THF system. Further, the vapor pressure of water in the empty hydrate as well as Langmuir adsorption constants has been expressed in terms of concentration of the promoter. The model predictions is compared with available experimental data on the phase equilibrium of CO2 hydrates in the presence of TBAB and THF aqueous solution and are found to be in good agreement. Then, the developed model is also applied for the prediction of phase equilibrium conditions of the semiclathrate hydrates of CO2 in the presence of TBAB + NaCl solution. The developed model is found to interpret the promotion effects of both TBAB (with or without NaCl) and THF on phase stability conditions of CO2 hydrate. The overall average absolute deviation in pressure has been perceived to be within 3.6% for TBAB and 7.7% for TBAB + NaCl both with PMZH model and 6.9% for THF systems with NRTL model. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd. StartCopText© 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

Preservation of carbon dioxide clathrate hydrate in the presence of fructose or glucose and absence of sugars under freezer conditions

To investigate the preservation of CO2 clathrate hydrate in the presence of fructose or glucose and absence of sugars, CO2 hydrate samples were preserved at 238.2 K, 253.2 K and 258.2 K under atmospheric pressure for three weeks. The preservations of CO2 hydrate with those two monosaccharide sugars at both 238.2 K and 253.2 K were lower than that of the pure CO2 hydrate without the sugars. The results indicated that the viscosity of super-cooled or stable sugar aqueous solution and occurrence of super-cooled water in the sample hydrate particles are significant factors in the preservation of CO2 hydrate.

Preservation of carbon dioxide clathrate hydrate in the presence of trehalose under freezer conditions

To investigate the preservation of CO2 clathrate hydrate in the presence of sugar for the novel frozen dessert, mass fractions of CO2 clathrate hydrate in CO2 clathrate hydrate samples coexisting with trehalose were intermittently measured. The samples were prepared from trehalose aqueous solution with trehalose mass fractions of 0.05 and 0.10 at 3.0 MPa and 276.2 K. The samples having particle sizes of 1.0 mm and 5.6–8.0 mm were stored at 243.2 K and 253.2 K for three weeks under atmospheric pressure. The mass fractions of CO2 clathrate hydrate in the samples were 0.87–0.97 before the preservation, and CO2 clathrate hydrate still remained 0.56–0.76 in the mass fractions for 5.6–8.0 mm samples and 0.37–0.55 for 1.0 mm samples after the preservation. The preservation in the trehalose system was better than in the sucrose system and comparable to that in the pure CO2 clathrate hydrate system. This comparison indicates that trehalose is a more suitable sugar for the novel frozen carbonated dessert using CO2 clathrate hydrate than sucrose in terms of CO2 concentration in the dessert. It is inferred that existence of aqueous solution in the samples is a significant factor of the preservation of CO2 clathrate hydrate in the presence of sugar.

Phase equilibrium condition measurements in carbon dioxide clathrate hydrate forming system from 199.1 K to 247.1 K

This paper reports ice + vapor + hydrate three-phase equilibrium condition measurements in CO2 + H2O system at the temperatures from 199.1 K to 247.1 K. The phase equilibrium pressures measured in the present study are from 34.3 kPa to 406.6 kPa. The measurements were performed using the batch, isochoric method. The results of the present measurements complement the lack of the literature data on the phase equilibrium conditions at the above temperature range and contribute to CO2 hydrate-related environmental issues and technologies below the water freezing temperature such as Martian environment, fire extinguisher and working media of power generation system.

Stability and cell distortion of sI clathrate hydrates of methane and carbon dioxide: A 2D lattice-gas model study

Thermodynamic models of the stability of clathrate hydrates are important for different applications such as the storage, separation and transport of gases. The development of improved models relies on a better understanding of the relationships between the macroscopic stability of clathrate hydrates and their structure. In particular, lattice distortion is an important parameter that is difficult to incorporate in thermodynamic models of clathrate hydrates. In this work, a 2D lattice-gas model has been applied for the first time for the study of the stability and lattice distortion of sI clathrate hydrates of methane and carbon dioxide. Results show a direct relationship between cell distortion and cell occupancy: the minimum distortion is found at cell occupancies near 1. In addition, in the case of carbon dioxide hydrates, a complex behavior is observed due to the partial occupancy of small cavities by guest CO2 molecules. By relating lattice distortion with hydrate stability, phase diagrams can be calculated which are in qualitative agreement with experimental diagrams and with results of more complex simulation methods.

Quantum Dynamics of Carbon Dioxide Encapsulated in the Cages of the sI Clathrate Hydrate: Structural Guest Distributions and Cage Occupation

We perform quantum multiconfiguration time-dependent Hartree calculations for the two cages of the sI CO2 clathrate hydrate, and we report, for first time, results on the translational, rotational, and vibrational states. The potential surface is constructed by the semiempirical SPC/E water model and pairwise additive interactions between the CO2 molecule and all water molecules forming each cage, while a spectroscopic-determined potential is used for the CO2 monomer. The exact kinetic energy operator is derived for the linear CO2 in the cage, and the potential energy operator is adapted to combined mode schemes, chosen adequately in order to obtain the desired product representation. The rotational ability of the CO2 is hindered in the small cavities (512), while in the large cage (51262) translational and rotational degrees of freedom are highly coupled. By analyzing the corresponding T-R eigenstates, we established a connection with experimental X-ray measurements on the orientation of the CO2 molecule in the two cages. Further, vibrational excitations of the fundamental symmetric and antisymmetric stretch modes, their overtones, and combination bands are computed from 7D quantum calculations. We found significant frequency shifts, which are comparable to those observed in the double-peak profile of the experimentally recorded infrared spectra, for the CO2 molecule trapped in the small and large cages of the sI clathrate hydrate. Such good agreement, with the data from recent spectroscopic studies of carbon dioxide clathrate hydrate at low temperatures, indicates a single occupancy of the sI structure cages, allowing an assessment of the theoretical approaches employed.