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Sample records for co2 clathrate hydrates

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

    Science.gov (United States)

    Nagashima, Hironori D; Takeya, Satoshi; Uchida, Tsutomu; Ohmura, Ryo

    2016-01-19

    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.

  2. Investigating the Metastability of Clathrate Hydrates for Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Koh, Carolyn Ann [Colorado School of Mines, Golden, CO (United States)

    2014-11-18

    Important breakthrough discoveries have been achieved from the DOE award on the key processes controlling the synthesis and structure-property relations of clathrate hydrates, which are critical to the development of clathrate hydrates as energy storage materials. Key achievements include: (i) the discovery of key clathrate hydrate building blocks (stable and metastable) leading to clathrate hydrate nucleation and growth; (ii) development of a rapid clathrate hydrate synthesis route via a seeding mechanism; (iii) synthesis-structure relations of H2 + CH4/CO2 binary hydrates to control thermodynamic requirements for energy storage and sequestration applications; (iv) discovery of a new metastable phase present during clathrate hydrate structural transitions. The success of our research to-date is demonstrated by the significant papers we have published in high impact journals, including Science, Angewandte Chemie, J. Am. Chem. Soc. Intellectual Merits of Project Accomplishments: The intellectual merits of the project accomplishments are significant and transformative, in which the fundamental coupled computational and experimental program has provided new and critical understanding on the key processes controlling the nucleation, growth, and thermodynamics of clathrate hydrates containing hydrogen, methane, carbon dioxide, and other guest molecules for energy storage. Key examples of the intellectual merits of the accomplishments include: the first discovery of the nucleation pathways and dominant stable and metastable structures leading to clathrate hydrate formation; the discovery and experimental confirmation of new metastable clathrate hydrate structures; the development of new synthesis methods for controlling clathrate hydrate formation and enclathration of molecular hydrogen. Broader Impacts of Project Accomplishments: The molecular investigations performed in this project on the synthesis (nucleation & growth)-structure-stability relations of clathrate

  3. IR reflectance spectroscopy of carbon dioxide clathrate hydrates. Implications for Saturn's icy moons.

    Science.gov (United States)

    Oancea, A.; Grasset, O.; Le Menn, E.; Bezacier, L.; Bollengier, O.; Le Mouélic, S.; Tobie, G.

    2012-04-01

    A CO2 spectral band was discovered by VIMS on the Saturn's satellites Dione, Hyperion, Iapetus and Phoebe [1]. The band position on the three first satellites corresponds to CO2 trapped in a complex material, but no indication exists whether this latter is water ice or some mineral or complex organic compound [1]. On Phoebe, the CO2 spectral band is consistent with solid CO2 or CO2 molecules trapped in the small cages of a clathrate hydrate structure [2]. It is thought that clathrate hydrates could play a significant role in the chemistry of the solar nebula [3] and in the physical evolution of astrophysical objects [4]. But so far, no clathrate hydrate structure has been observed in astrophysical environments. Moreover, identification of molecules trapped in a clathrate hydrate structure is extremely difficult because of the strong IR vibration modes of the water ice matrix. In this work, experimental IR reflectance spectra for CO2 clathrate hydrates are studied on grains and films. Clathrates are synthesized in a high pressure autoclave at low temperatures. IR spectral analysis is made with a low pressure and low temperature cryostat. These experimental conditions - 80 spectrum will be presented. A comparison between the absorption bands of CO2 clathrate hydrates obtained in our lab and CO2 absorption bands as detected by VIMS on the icy satellites of Saturn will be shown. This experimental work confirms that VIMS data are not consistent with the presence of structure I CO2 clathrate hydrates on the surface of the icy moons. Possibility of having metastable structure II still remains unsolved and will be discussed. [1] Dalton et al., Space Sci. Rev. 2010, 153 : 113-154. [2] Cruikshank D.P. et al, Icarus, 2010, 206: 561-572. [3] Mousis O. et al , Ap. J. 2009, 691: 1780-1786. [4] Choukroun M. et al, in Solar System Ices, edited by Castillo-Rogez, J. et al., 2011.

  4. Thermodynamic studies on semi-clathrate hydrates of TBAB + gases containing carbon dioxide

    International Nuclear Information System (INIS)

    Eslamimanesh, Ali

    2012-01-01

    CO 2 capture has become an important area of research mainly due to its drastic greenhouse effects. Gas hydrate formation as a separation technique shows tremendous potential, both from a physical feasibility as well as an envisaged lower energy utilization criterion. Briefly, gas (clathrate) hydrates are non-stoichiometric, ice-like crystalline compounds formed through a combination of water and suitably sized guest molecule(s) under low-temperatures and elevated pressures. As the pressure required for gas hydrate formation is generally high, therefore, aqueous solution of tetra-n-butyl ammonium bromide (TBAB) is added to the system as a gas hydrate promoter. TBAB generally reduces the required hydrate formation pressure and/or increases the formation temperature as well as modifies the selectivity of hydrate cages to capture CO 2 molecules. TBAB also takes part in the hydrogen-bonded cages. Such hydrates are called 'semi-clathrate' hydrates. Evidently, reliable and accurate phase equilibrium data, acceptable thermodynamic models, and other thermodynamic studies should be provided to design efficient separation processes using the aforementioned technology. For this purpose, phase equilibria of clathrate/semi-clathrate hydrates of various gas mixtures containing CO 2 (CO 2 + CH 4 /N 2 /H 2 ) in the presence of pure water and aqueous solutions of TBAB have been measured in this thesis. In the theoretical section of the thesis, a thermodynamic model on the basis of the van der Waals and Platteeuw (vdW-P) solid solution theory along with the modified equations for determination of the Langmuir constants of the hydrate formers has been successfully developed to represent/predict equilibrium conditions of semi-clathrate hydrates of CO 2 , CH 4 , and N 2 . Later, several thermodynamic consistency tests on the basis of Gibbs-Duhem equation as well as a statistical approach have been applied on the phase equilibrium data of the systems of mixed/simple clathrate hydrates

  5. Collagen tissue treated with chitosan solution in H2O/CO2 mixtures: Influence of clathrates hydrates on the structure and mechanical properties.

    Science.gov (United States)

    Chaschin, Ivan S; Bakuleva, Natalia P; Grigoriev, Timofei E; Krasheninnikov, Sergey V; Nikitin, Lev N

    2017-03-01

    A mixture of water/carbon dioxide is a "green" perspective solvent from the viewpoint of biomedical applications. Clathrate hydrates are formed this solvent under certain conditions and a very interesting question is the impact of clathrates hydrates on the structure and properties of bovine pericardium, which is used in biomedicine, in particular as a main part of biological heart valve prostheses. The aim of the present work is to investigate the influence of clathrates on the structure and mechanical properties of the collagen tissue treated with chitosan in H 2 O/CO 2 mixtures under pressure 3.0-3.5MPa and temperatures 2-4°C. It was first found that the clathrate hydrates in this media due to the strong fluctuations "bomb" collagen tissue of bovine pericardium, which is manifested in the appearance of numerous small gaps (pores) with mean size of 225±25nm and large pores with size of 1-3μ on the surface and within collagen matrices. High porosity leads to averaging characteristics of the organization structure in tissues with different orientation of the collagen fibers. As a result, the mechanical properties of the collagen tissue with a different orientation of the collagen fibrils become similar, which is quite different from their original properties. The structural changes caused by the influence of the environment clathrate hydrates led to a significant decrease of the tensile strength (30-47% in total, p<0.05) and initial elastic moduli (74-83%, p<0.05). However, the final elastic moduli and the maximum tensile virtually unchanged compared to the control. Nevertheless, it was found that the direct deposition of chitosan from the H 2 O/CO 2 mixtures with clathrate improve the mechanical-strength properties of the porous matrices. We believe that these improved mechanical properties are achieved due to particularly deep and uniform impregnation of the collagen matrix with chitosan from its pressurized solutions in H 2 O/CO 2 mixtures. Copyright © 2016

  6. CLATHRATE HYDRATES FORMATION IN SHORT-PERIOD COMETS

    International Nuclear Information System (INIS)

    Marboeuf, Ulysse; Mousis, Olivier; Petit, Jean-Marc; Schmitt, Bernard

    2010-01-01

    The initial composition of current models of cometary nuclei is only based on two forms of ice: crystalline ice for long-period comets and amorphous ice for short-period comets. A third form of ice, i.e., clathrate hydrate, could exist within the short-period cometary nuclei, but the area of formation of this crystalline structure in these objects has never been studied. Here, we show that the thermodynamic conditions in the interior of short-period comets allow the existence of clathrate hydrates in Halley-type comets. We show that their existence is viable in the Jupiter family comets only when the equilibrium pressure of CO clathrate hydrate is at least 1 order of magnitude lower than the usually assumed theoretical value. We calculate that the amount of volatiles that could be trapped in the clathrate hydrate layer may be orders of magnitude greater than the daily amount of gas released at the surface of the nucleus at perihelion. The formation and the destruction of the clathrate hydrate cages could then explain the diversity of composition of volatiles observed in comets, as well as some pre-perihelion outbursts. We finally show that the potential clathrate hydrate layer in comet 67P/Churyumov-Gerasimenko would, unfortunately, be deep inside the nucleus, out of reach of the Rosetta lander. However, such a clathrate hydrate layer would show up by the gas composition of the coma.

  7. Exploring the possibility to store the mixed oxygen-hydrogen cluster in clathrate hydrate in molar ratio 1:2 (O2+2H2).

    Science.gov (United States)

    Qin, Yan; Du, Qi-Shi; Xie, Neng-Zhong; Li, Jian-Xiu; Huang, Ri-Bo

    2017-05-01

    An interesting possibility is explored: storing the mixture of oxygen and hydrogen in clathrate hydrate in molar ratio 1:2. The interaction energies between oxygen, hydrogen, and clathrate hydrate are calculated using high level quantum chemical methods. The useful conclusion points from this study are summarized as follows. (1) The interaction energies of oxygen-hydrogen mixed cluster are larger than the energies of pure hydrogen molecular cluster. (2) The affinity of oxygen molecules with water molecules is larger than that of the hydrogen molecules with water molecules. (3) The dimension of O 2 -2H 2 interaction structure is smaller than the dimension of CO 2 -2H 2 interaction structure. (4) The escaping energy of oxygen molecules from the hydrate cell is larger than that of the hydrogen molecules. (5) The high affinity of the oxygen molecules with both the water molecules and the hydrogen molecules may promote the stability of oxygen-hydrogen mixture in the clathrate hydrate. Therefore it is possible to store the mixed (O 2 +2H 2 ) cluster in clathrate hydrate. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Observation of interstitial molecular hydrogen in clathrate hydrates.

    Science.gov (United States)

    Grim, R Gary; Barnes, Brian C; Lafond, Patrick G; Kockelmann, Winfred A; Keen, David A; Soper, Alan K; Hiratsuka, Masaki; Yasuoka, Kenji; Koh, Carolyn A; Sum, Amadeu K

    2014-09-26

    The current knowledge and description of guest molecules within clathrate hydrates only accounts for occupancy within regular polyhedral water cages. Experimental measurements and simulations, examining the tert-butylamine + H2 + H2O hydrate system, now suggest that H2 can also be incorporated within hydrate crystal structures by occupying interstitial sites, that is, locations other than the interior of regular polyhedral water cages. Specifically, H2 is found within the shared heptagonal faces of the large (4(3)5(9)6(2)7(3)) cage and in cavities formed from the disruption of smaller (4(4)5(4)) water cages. The ability of H2 to occupy these interstitial sites and fluctuate position in the crystal lattice demonstrates the dynamic behavior of H2 in solids and reveals new insight into guest-guest and guest-host interactions in clathrate hydrates, with potential implications in increasing overall energy storage properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Observations of CO{sub 2} clathrate hydrate formation and dissolution under deep-ocean disposal conditions

    Energy Technology Data Exchange (ETDEWEB)

    Warzinski, R.P.; Cugini, A.V. [Department of Energy, Pittsburgh, PA (United States); Holder, G.D. [Univ. of Pittsburgh, Pittsburgh, PA (United States)

    1995-11-01

    Disposal of anthropogenic emissions of CO{sub 2} may be required to mitigate rises in atmospheric levels of this greenhouse gas if other measures are ineffective and the worst global warming scenarios begin to occur. Long-term storage of large quantities of CO{sub 2} has been proposed, but the feasibility of large land and ocean disposal options remains to be established. Determining the fate of liquid CO{sub 2} injected into the ocean at depths greater than 500 m is complicated by uncertainties associated with the physical behavior of CO{sub 2} under these conditions, in particular the possible formation of the ice-like CO{sub 2} clathrate hydrate. Resolving this issue is key to establishing the technical feasibility of this option. Experimental and theoretical work in this area is reported.

  10. Polymorphism in Br2 clathrate hydrates.

    Science.gov (United States)

    Goldschleger, I U; Kerenskaya, G; Janda, K C; Apkarian, V A

    2008-02-07

    The structure and composition of bromine clathrate hydrate has been controversial for more than 170 years due to the large variation of its observed stoichiometries. Several different crystal structures were proposed before 1997 when Udachin et al. (Udachin, K. A.; Enright, G. D.; Ratcliffe, C. I.; Ripmeester, J. A. J. Am. Chem. Soc. 1997, 119, 11481) concluded that Br2 forms only the tetragonal structure (TS-I). We show polymorphism in Br2 clathrate hydrates by identifying two distinct crystal structures through optical microscopy and resonant Raman spectroscopy on single crystals. After growing TS-I crystals from a liquid bromine-water solution, upon dropping the temperature slightly below -7 degrees C, new crystals of cubic morphology form. The new crystals, which have a limited thermal stability range, are assigned to the CS-II structure. The two structures are clearly distinguished by the resonant Raman spectra of the enclathrated Br2, which show long overtone progressions and allow the extraction of accurate vibrational parameters: omega(e) = 321.2 +/- 0.1 cm(-1) and omega(e)x(e) = 0.82 +/- 0.05 cm(-1) in TS-I and omega(e) = 317.5 +/- 0.1 cm(-1) and omega(e)x(e) = 0.70 +/- 0.1 cm(-1) in CS-II. On the basis of structural analysis, the discovery of the CS-II crystals implies stability of a large class of bromine hydrate structures and, therefore, polymorphism.

  11. Volatile inventories in clathrate hydrates formed in the primordial nebula.

    Science.gov (United States)

    Mousis, Olivier; Lunine, Jonathan I; Picaud, Sylvain; Cordier, Daniel

    2010-01-01

    between the different volatiles in the clathrate hydrates themselves. On the other hand, if contraction or expansion of the cages due to temperature variations are imposed in our model, the Ar and Kr mole fractions can be modified up to several orders of magnitude in clathrate hydrates. Moreover, mole fractions of other molecules such as N2 or CO are also subject to strong changes with the variation of the size of the cages. Our results may affect the predictions of the composition of the planetesimals formed in the outer solar system. In particular, the volatile abundances calculated in the giant planets' atmospheres should be altered because these quantities are proportional to the mass of accreted and vaporized icy planetesimals. For similar reasons, the estimates of the volatile budgets accreted by icy satellites and comets may also be altered by our calculations. For instance, under some conditions, our calculations predict that the abundance of argon in the atmosphere of Titan should be higher than the value measured by Huygens. Moreover, the Ar abundance in comets could be higher than the value predicted by models invoking the incorporation of volatiles in the form of clathrate hydrates in these bodies.

  12. Raman spectroscopic studies of hydrogen clathrate hydrates.

    Science.gov (United States)

    Strobel, Timothy A; Sloan, E Dendy; Koh, Carolyn A

    2009-01-07

    Raman spectroscopic measurements of simple hydrogen and tetrahydrofuran+hydrogen sII clathrate hydrates have been performed. Both the roton and vibron bands illuminate interesting quantum dynamics of enclathrated H(2) molecules. The complex vibron region of the Raman spectrum has been interpreted by observing the change in population of these bands with temperature, measuring the absolute H(2) content as a function of pressure, and with D(2) isotopic substitution. Quadruple occupancy of the large sII clathrate cavity shows the highest H(2) vibrational frequency, followed by triple and double occupancies. Singly occupied small cavities display the lowest vibrational frequency. The vibrational frequencies of H(2) within all cavity environments are redshifted from the free gas phase value. At 76 K, the progression from ortho- to para-H(2) occurs over a relatively slow time period (days). The rotational degeneracy of H(2) molecules within the clathrate cavities is lifted, observed directly in splitting of the para-H(2) roton band. Raman spectra from H(2) and D(2) hydrates suggest that the occupancy patterns between the two hydrates are analogous, increasing confidence that D(2) is a suitable substitute for H(2). The measurements suggest that Raman is an effective and convenient method to determine the relative occupancy of hydrogen molecules in different clathrate cavities.

  13. UV-visible and resonance Raman spectroscopy of halogen molecules in clathrate hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Janda, K.C.; Kerenskaya, G.; Goldsheleger, I.U.; Apkarian, V.A.; Fleischer, E.B. [California Univ., Irvine, CA (United States). Dept. of Chemistry

    2008-07-01

    Resonance Raman spectroscopy was used to study halogen clathrate hydrate solids. In particular, this paper presented an ultraviolet-visible spectra for a polycrystalline sample of chlorine clathrate hydrate and two single crystal samples of bromine clathrate hydrate. UV-visible spectroscopy was used to study the interactions between the halogen guest molecule and the host water lattice. The spectrum for chlorine hydrate had a strong temperature dependence, while the spectra for bromine clathrate hydrate single crystals had a stable cubic type 2 structure as well as a tetragonal structure. A metastable cubic type 1 structure was also observed. Resonance Raman spectroscopy showed how the molecules fit into the host cages. 25 refs., 2 tabs., 7 figs.

  14. Thermodynamics of clathrate hydrate at low and high pressures with application to the outer solar system

    Science.gov (United States)

    Lunine, J. I.; Stevenson, D. J.

    1985-01-01

    The thermodynamic stability of clathrate hydrate is calculated to predict the formation conditions corresponding to a range of solar system parameters. The calculations were performed using the statistical mechanical theory developed by van der Waals and Platteeuw (1959) and existing experimental data concerning clathrate hydrate and its components. Dissociation pressures and partition functions (Langmuir constants) are predicted at low pressure for CO clathrate (hydrate) using the properties of chemicals similar to CO. It is argued that nonsolar but well constrained noble gas abundances may be measurable by the Galileo spacecraft in the Jovian atmosphere if the observed carbon enhancement is due to bombardment of the atmosphere by clathrate-bearing planetesimals sometime after planetary formation. The noble gas abundances of the Jovian satellite Titan are predicted, assuming that most of the methane in Titan is accreted as clathrate. It is suggested that under thermodynamically appropriate conditions, complete clathration of water ice could have occurred in high-pressure nebulas around giant planets, but probably not in the outer solar nebula. The stability of clathrate in other pressure ranges is also discussed.

  15. The effect of classical and quantum dynamics on vibrational frequency shifts of H2 in clathrate hydrates

    International Nuclear Information System (INIS)

    Plattner, Nuria; Meuwly, Markus

    2014-01-01

    Vibrational frequency shifts of H 2 in clathrate hydrates are important to understand the properties and elucidate details of the clathrate structure. Experimental spectra of H 2 in clathrate hydrates have been measured for different clathrate compositions, temperatures, and pressures. In order to establish reliable relationships between the clathrate structure, dynamics, and observed frequencies, calculations of vibrational frequency shifts in different clathrate environments are required. In this study, a combination of classical molecular dynamics simulations, electronic structure calculations, and quantum dynamical simulation is used to calculate relative vibrational frequencies of H 2 in clathrate hydrates. This approach allows us to assess dynamical effects and simulate the change of vibrational frequencies with temperature and pressure. The frequency distributions of the H 2 vibrations in the different clathrate cage types agree favorably with experiment. Also, the simulations demonstrate that H 2 in the 5 12 cage is more sensitive to the details of the environment and to quantum dynamical effects, in particular when the cage is doubly occupied. We show that for the 5 12 cage quantum effects lead to frequency increases and double occupation is unlikely. This is different for the 5 12 6 4 cages for which higher occupation numbers than one H 2 per cage are likely

  16. Roles of Clathrate Hydrates in Crustal Heating and Volatile Storage/Release on Earth, Mars, and Beyond

    Science.gov (United States)

    Kargel, J. S.; Beget, J.; Furfaro, R.; Prieto-Ballesteros, O.; Palmero-Rodriguez, J. A.

    2007-12-01

    Clathrate hydrates are stable through much of the Solar System. These materials and hydrate-like amorphous associations of water with N2, CO, CH4, CO2, O2 and other molecules could, in fact, constitute the bulk of the non-rock components of some icy satellites, comets, and Kuiper Belt Objects. CO2 clathrate is thermodynamically stable at the Martian South Pole surface and could form a significant fraction of both Martian polar caps and icy permafrost distributed across one-third of the Martian surface. CH4 clathrate is the largest clathrate material in Earth's permafrost and cold seafloor regions, and it may be a major volatile reservoir on Mars, too. CO2 clathrate is less abundant on Earth but it might store most of Mars' CO2 inventory and thus may be one of the critical components in the climate system of that planet, just as CH4 clathrate is for Earth. These ice-like phases not only store biologically, geologically, and climatologically important gases, but they also are natural thermal insulators. Thus, they retard the conductive flow of geothermal heat, and thick accumulations of them can modify geotherms, cause brines to exist where otherwise they would not, and induce low-grade metamorphism of upper crustal rocks underlying the insulating bodies. This mechanism of crustal heating may be especially important in assisting hydrogeologic activity on Mars, gas-rich carbonaceous asteroids, icy satellites, and Kuiper Belt Objects. These worlds, compared to Earth, are comparatively energy starved and frozen but may partly make up for their deficit of joules by having large accumulations of joule-conserving hydrates. Thick, continuous layers of clathrate may seal in gases and produce high gas fugacities in aquifers underlying the clathrates, thus producing gas-rich reservoirs capable of erupting violently. This may have happened repeatedly in Earth history, with global climatic consequences for abrupt climate change. We have hypothesized that such eruptions may have

  17. Confining CO2 inside the nanocavities of the sI clathrate: a quantum dynamics study

    International Nuclear Information System (INIS)

    Prosmiti, R; Arismendi-Arrieta, D J; Valdés, Á

    2015-01-01

    Clathrate hydrates have been found to occur naturally, and have been extensively studied due to their important industrial applications, such as the storage of the CO 2 from the atmosphere and control climate change. Thus, quantitative understanding of physical and chemical properties, as well as the factors that control the formation of CO 2 hydrates, on both macroscopic and microscopic levels is essential in several areas of physical science. (paper)

  18. Clathrate Hydrates for Thermal Energy Storage in Buildings: Overview of Proper Hydrate-Forming Compounds

    Directory of Open Access Journals (Sweden)

    Beatrice Castellani

    2014-09-01

    Full Text Available Increasing energy costs are at the origin of the great progress in the field of phase change materials (PCMs. The present work aims at studying the application of clathrate hydrates as PCMs in buildings. Clathrate hydrates are crystalline structures in which guest molecules are enclosed in the crystal lattice of water molecules. Clathrate hydrates can form also at ambient pressure and present a high latent heat, and for this reason, they are good candidates for being used as PCMs. The parameter that makes a PCM suitable to be used in buildings is, first of all, a melting temperature at about 25 °C. The paper provides an overview of groups of clathrate hydrates, whose physical and chemical characteristics could meet the requirements needed for their application in buildings. Simulations with a dynamic building simulation tool are carried out to evaluate the performance of clathrate hydrates in enhancing thermal comfort through the moderation of summer temperature swings and, therefore, in reducing energy consumption. Simulations suggest that clathrate hydrates have a potential in terms of improvement of indoor thermal comfort and a reduction of energy consumption for cooling. Cooling effects of 0.5 °C and reduced overheating hours of up to 1.1% are predicted.

  19. Electric double-layer capacitor based on an ionic clathrate hydrate.

    Science.gov (United States)

    Lee, Wonhee; Kwon, Minchul; Park, Seongmin; Lim, Dongwook; Cha, Jong-Ho; Lee, Huen

    2013-07-01

    Herein, we suggest a new approach to an electric double-layer capacitor (EDLC) that is based on a proton-conducting ionic clathrate hydrate (ICH). The ice-like structures of clathrate hydrates, which are comprised of host water molecules and guest ions, make them suitable for applications in EDLC electrolytes, owing to their high proton conductivities and thermal stabilities. The carbon materials in the ICH Me4NOH⋅5 H2O show a high specific capacitance, reversible charge-discharge behavior, and a long cycle life. The ionic-hydrate complex provides the following advantages in comparison with conventional aqueous and polymer electrolytes: 1) The ICH does not cause leakage problems under normal EDLC operating conditions. 2) The hydrate material can be utilized itself, without requiring any pre-treatments or activation for proton conduction, thus shortening the preparation procedure of the EDLC. 3) The crystallization of the ICH makes it possible to tailor practical EDLC dimensions because of its fluidity as a liquid hydrate. 4) The hydrate solid electrolyte exhibits more-favorable electrochemical stability than aqueous and polymer electrolytes. Therefore, ICH materials are expected to find practical applications in versatile energy devices that incorporate electrochemical systems. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Critical guest concentration and complete tuning pattern appearing in the binary clathrate hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Cha, J.H.; Lee, H. [Korea Advanced Inst. of Science and Technology, Yuseong-gu, Daejeon (Korea, Republic of). Dept. of Chemical and Biomolecular Engineering; Kim, D.Y. [SK Engineering and Construction, Jongno-gu, Seoul (Korea, Republic of); Park, J. [Hanwha Chemical R and D Center, Yuseong-gu, Daejeon (Korea, Republic of); Lee, J.W. [Kongju National Univ., Cheonan, Chungnam (Korea, Republic of); Ripmeester, J.A. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences

    2008-07-01

    Clathrate hydrates, or gas hydrates, are stabilized by van der Waals interaction between a guest molecule and a host framework. Because of their property, they are a potential resource in the exploitation of natural gas hydrates, as a material for the sequestration of carbon dioxide (CO{sub 2}), as a means of storage and transportation of natural gas, as well as hydrogen storage. Clathrate hydrate research can be divided into two categories that emphasize either macroscopic or microscopic approaches. However, these two approaches need to be closely linked for a better understanding of the structures and processes involving both natural phenomena and hydrates for industrial processes. Details on the molecular scale that concern the less usual properties of clathrate hydrates remain unknown. This paper presented the results of a study that reported on the existence of a critical guest concentration (CGC) and established the complete tuning pattern that occurred in the binary hydrates, including water-soluble hydrate formers (promoters) and water-insoluble guests. The paper presented the experimental procedures, including formation of the methane (CH{sub 4}) and tetrahydrofuran (THF) binary hydrate; a schematic diagram of the experimental apparatus; and formation of the CH{sub 4} and t-BuNH{sub 2} binary hydrate. Nuclear magnetic resonance (NMR) spectroscopic measurements and thermodynamic measurements were also presented. It was concluded that the CGC value appeared to primarily depend on the chemical nature of a liquid guest component participating in the binary hydrate formation. 10 refs., 2 tabs., 9 figs.

  1. A spectroscopic study of the structure and occupancies of clathrate hydrates incorporating hydrogen

    Science.gov (United States)

    Grim, R. Gary

    With the ability to store and concentrate gases inside a clean and abundant water framework, clathrate hydrates are considered to be a promising material for many applications related to gas storage, separation, and sequestration. Hydrates of hydrogen are particularly interesting, for in addition to these potential applications, the small molecular size provides an opportunity for use as a model guest in many fundamental studies such as guest diffusion, multiple guest occupancy, and quantum mechanical effects upon confinement. In attempt to study these effects and the viability of H 2 hydrates as an energy storage material, a combined experimental and theoretical approach incorporating Raman spectroscopy, X-ray and neutron diffraction, nuclear magnetic resonance, ab-initio calculations, and molecular dynamic simulations was performed. One of the most significant challenges in the application of H2 clathrate hydrates is the demanding thermodynamic requirements needed for stability. In recent years, a mechanism known as the `tuning' effect had reportedly solved this issue where thermodynamic requirements could be reduced while simultaneously maintaining high storage capacities. In this work, the viability and validity of this technique is explored and alternative explanations in the form of epitaxial hydrate growth under high driving force conditions are discussed. A second, and equally important challenge facing clathrate hydrates as a future storage material is the overall storage capacity of H2. In previous work, H2 has only been experimentally verified to occupy the small 512 and 43566 3 cages and also in the large 51264 cages of the type II clathrate, often with an energy deficient promoter. In order to achieve more robust energy densities, other hydrate cages must be accessible. Herein a new method for increasing overall hydrate energy densities is presented involving the incorporation of H2 in the large cages of the type I clathrate with CH4 as a co

  2. Enhanced Selectivity of the Separation of CO2 from N2 during Crystallization of Semi-Clathrates from Quaternary Ammonium Solutions

    International Nuclear Information System (INIS)

    Herri, J.M.; Bouchemoua, A.; Kwaterski, M.; Brantuas, P.; Galfre, A.; Bouillot, B.; Douzet, J.; Ouabbas, Y.; Cameirao, A.

    2014-01-01

    CO 2 mitigation is crucial environmental problem and a societal challenge for this century. CO 2 capture and sequestration is a route to solve a part of the problem, especially for the industries in which the gases to be treated are well localized. CO 2 capture by using hydrate is a process in which the cost of the separation is due to compression of gases to reach the gas hydrate formation conditions. Under pressure, the water and gas forms a solid that encapsulates preferentially CO 2 . The gas hydrate formation requires high pressures and low temperatures, which explains the use of thermodynamic promoters to decrease the operative pressure. Quaternary ammonium salts represent an interesting family of components because of their thermodynamic effect, but also because they can generate crystals that are easily handled. In this work, we have made experiments concerning the equilibrium of (CO 2 , N 2 ) in presence of Tetra-n-Butyl Ammonium Bromide (TBAB) which form a semi-clathrate hydrate. We propose equilibrium data (pressure, temperature) in presence of TBAB at different concentrations and we compare them to the literature. We have also measured the composition of the hydrate phase in equilibrium with the gas phase at different CO 2 concentrations. We observe that the selectivity of the separation is dramatically increased in comparison to the selectivity of the pure water gas clathrate hydrate. We observe also a benefice on the operative pressure which can be dropped down to the atmospheric pressure. (authors)

  3. Phase equilibrium measurements and the tuning behavior of new sII clathrate hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Woongchul; Park, Seongmin; Ro, Hyeyoon; Koh, Dong-Yeun; Seol, Jiwoong [Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, Daejeon 305-701 (Korea, Republic of); Lee, Huen, E-mail: h_lee@kaist.ac.kr [Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, Daejeon 305-701 (Korea, Republic of); Graduate School of EEWS, KAIST, Daejeon 305-701 (Korea, Republic of)

    2012-01-15

    Graphical abstract: Pyrrolidine and piperidine act as sII clathrate hydrate formers under methane gas. Highlights: > New sII clathrate hydrate formers were proposed: pyrrolidine and piperidine. > Formation of gas hydrate with methane as help gas was confirmed. > NMR, Raman, and XRD patterns were analyzed to identify the hydrate structures. > We measured (L + H + V) phase equilibrium with proposed hydrate formers. > Tuning phenomena increase gas storage in (pyrrolidine + CH{sub 4}) clathrate hydrates. - Abstract: We suggest two types of new amine-type sII formers: pyrrolidine and piperidine. These guest compounds fail to form clathrate hydrate structures with host water, but instead have to combine with light gaseous guest molecules (methane) for enclathration. First, two binary clathrate hydrates of (pyrrolidine + methane) and (piperidine + methane) were synthesized at various amine concentrations. {sup 13}C NMR and Raman analysis were done to identify the clathrate hydrate structure and guest distribution over sII-S and sII-L cages. XRD was also used to find the exact structure and corresponding cell parameters. At a dilute pyrrolidine concentration of less than 5.56 mol%, the tuning phenomenon is observed such that methane molecules surprisingly occupy sII-L cages. At the critical guest concentration of about 0.1 mol%, the cage occupancy ratio reaches the maximum of approximately 0.5. At very dilute guest concentration below 0.1 mol%, the methane molecules fail to occupy large cages on account of their rarefied distribution in the network. Direct-release experiments were performed to determine the actual guest compositions in the clathrate hydrate phases. Finally, we measured the clathrate hydrate phase equilibria of (pyrrolidine + methane) and (piperidine + methane).

  4. Phase equilibrium measurements and the tuning behavior of new sII clathrate hydrates

    International Nuclear Information System (INIS)

    Shin, Woongchul; Park, Seongmin; Ro, Hyeyoon; Koh, Dong-Yeun; Seol, Jiwoong; Lee, Huen

    2012-01-01

    Graphical abstract: Pyrrolidine and piperidine act as sII clathrate hydrate formers under methane gas. Highlights: → New sII clathrate hydrate formers were proposed: pyrrolidine and piperidine. → Formation of gas hydrate with methane as help gas was confirmed. → NMR, Raman, and XRD patterns were analyzed to identify the hydrate structures. → We measured (L + H + V) phase equilibrium with proposed hydrate formers. → Tuning phenomena increase gas storage in (pyrrolidine + CH 4 ) clathrate hydrates. - Abstract: We suggest two types of new amine-type sII formers: pyrrolidine and piperidine. These guest compounds fail to form clathrate hydrate structures with host water, but instead have to combine with light gaseous guest molecules (methane) for enclathration. First, two binary clathrate hydrates of (pyrrolidine + methane) and (piperidine + methane) were synthesized at various amine concentrations. 13 C NMR and Raman analysis were done to identify the clathrate hydrate structure and guest distribution over sII-S and sII-L cages. XRD was also used to find the exact structure and corresponding cell parameters. At a dilute pyrrolidine concentration of less than 5.56 mol%, the tuning phenomenon is observed such that methane molecules surprisingly occupy sII-L cages. At the critical guest concentration of about 0.1 mol%, the cage occupancy ratio reaches the maximum of approximately 0.5. At very dilute guest concentration below 0.1 mol%, the methane molecules fail to occupy large cages on account of their rarefied distribution in the network. Direct-release experiments were performed to determine the actual guest compositions in the clathrate hydrate phases. Finally, we measured the clathrate hydrate phase equilibria of (pyrrolidine + methane) and (piperidine + methane).

  5. Novel nanotechnology for efficient production of binary clathrate hydrates of hydrogen and other compounds

    Energy Technology Data Exchange (ETDEWEB)

    Di Profio, P.; Arca, S.; Germani, R.; Savelli, G. [Perugia Univ., Perugia (Italy). Dept. of Chemistry, Center of Excellence on Innovative Nanostructured Materials

    2008-07-01

    The development of a hydrogen-based economy depends on finding ways to store hydrogen, but current hydrogen storage methods have significant disadvantages. One main challenge in storing sufficient amounts of hydrogen (up to 4 weight per cent) into a clathrate matrix is that of a kinetic origin, in that the mass transfer of hydrogen gas into clathrate structures is significantly limited by the macroscopic scale of the gas-liquid or gas-ice interfaces involved. This paper discussed the possibility of storing hydrogen in clathrate hydrates. It presented a newly developed method for preparing binary hydrogen hydrates that is based on the formation of amphiphile-aided nanoemulsions. Nanotechnology is used to reduce the size of hydrate particles to a few nanometers, thereby minimizing the kinetic hindrance to hydrate formation. This process has potential for increasing the amount of hydrogen stored, as it has provided ca. 1 weight per cent of hydrogen. Two new co-formers were also successfully tested, namely cyclopentane and tetrahydrothiophene. 23 refs., 10 figs.

  6. Hydrogen storage and carbon dioxide sequestration in TBAF semi-clathrate hydrates: Kinetics and evolution of hydrate-phase composition by in situ raman spectroscopy - Abstract -

    NARCIS (Netherlands)

    Torres Trueba, A.; Radoviæ, I.R.; Zevenbergen, J.F.; Kroon, M.C.; Peters, C.J.

    2012-01-01

    Carbon dioxide (CO2) represents almost one third of the emissions from the combustion of fossil fuels additionally, CO2 has been identified as the mayor contributor of global warming. Hydrogen (H2), on the other hand, due to its properties is considered a promising energy carrier. Clathrate hydrates

  7. Two-component, ab initio potential energy surface for CO2-H2O, extension to the hydrate clathrate, CO2@(H2O)20, and VSCF/VCI vibrational analyses of both.

    Science.gov (United States)

    Wang, Qingfeng Kee; Bowman, Joel M

    2017-10-28

    We report an ab initio, full-dimensional, potential energy surface (PES) for CO 2 -H 2 O, in which two-body interaction energies are fit using a basis of permutationally invariant polynomials and combined with accurate potentials for the non-interacting monomers. This approach which we have termed "plug and play" is extended here to improve the precision of the 2-body fit in the long range. This is done by combining two separate fits. One is a fit to 47 593 2-body energies in the region of strong interaction and approaching the long range, and the second one is a fit to 6244 2-body energies in the long range. The two fits have a region of overlap which permits a smooth switch from one to the other. All energies are obtained at the CCSD(T)-F12b/aug-cc-pVTZ level of theory. Properties of the full PES, i.e., stationary points, harmonic frequencies of the global minimum, etc., are shown to be in excellent agreement with direct CCSD(T)-F12b/aug-cc-pVTZ results. Diffusion Monte Carlo calculations of the dimer zero-point energy (ZPE) are performed, and a dissociation energy, D 0 , of 787 cm -1 is obtained using that ZPE, D e , and the rigorous ZPEs of the monomers. Using a benchmark D e , D 0 is 758 cm -1 . Vibrational self-consistent field (VSCF)/virtual state configuration interaction (VCI) MULTIMODE calculations of intramolecular fundamentals are reported and are in good agreement with available experimental results. Finally, the full dimer PES is combined with an existing ab initio water potential to develop a potential for the CO 2 hydrate clathrate CO 2 (H 2 O) 20 (5 12 water cage). A full normal-mode analysis of this hydrate clathrate is reported as are local-monomer VSCF/VCI calculations of the fundamentals of CO 2 .

  8. Experimental Equipment Validation for Methane (CH4) and Carbon Dioxide (CO2) Hydrates

    Science.gov (United States)

    Saad Khan, Muhammad; Yaqub, Sana; Manner, Naathiya; Ani Karthwathi, Nur; Qasim, Ali; Mellon, Nurhayati Binti; Lal, Bhajan

    2018-04-01

    Clathrate hydrates are eminent structures regard as a threat to the gas and oil industry in light of their irritating propensity to subsea pipelines. For natural gas transmission and processing, the formation of gas hydrate is one of the main flow assurance delinquent has led researchers toward conducting fresh and meticulous studies on various aspects of gas hydrates. This paper highlighted the thermodynamic analysis on pure CH4 and CO2 gas hydrates on the custom fabricated equipment (Sapphire cell hydrate reactor) for experimental validation. CO2 gas hydrate formed at lower pressure (41 bar) as compared to CH4 gas hydrate (70 bar) while comparison of thermodynamic properties between CH4 and CO2 also presented in this study. This preliminary study could provide pathways for the quest of potent hydrate inhibitors.

  9. Two-component, ab initio potential energy surface for CO2—H2O, extension to the hydrate clathrate, CO2@(H2O)20, and VSCF/VCI vibrational analyses of both

    Science.gov (United States)

    Wang, Qingfeng Kee; Bowman, Joel M.

    2017-10-01

    We report an ab initio, full-dimensional, potential energy surface (PES) for CO2—H2O, in which two-body interaction energies are fit using a basis of permutationally invariant polynomials and combined with accurate potentials for the non-interacting monomers. This approach which we have termed "plug and play" is extended here to improve the precision of the 2-body fit in the long range. This is done by combining two separate fits. One is a fit to 47 593 2-body energies in the region of strong interaction and approaching the long range, and the second one is a fit to 6244 2-body energies in the long range. The two fits have a region of overlap which permits a smooth switch from one to the other. All energies are obtained at the CCSD(T)-F12b/aug-cc-pVTZ level of theory. Properties of the full PES, i.e., stationary points, harmonic frequencies of the global minimum, etc., are shown to be in excellent agreement with direct CCSD(T)-F12b/aug-cc-pVTZ results. Diffusion Monte Carlo calculations of the dimer zero-point energy (ZPE) are performed, and a dissociation energy, D0, of 787 cm-1 is obtained using that ZPE, De, and the rigorous ZPEs of the monomers. Using a benchmark De, D0 is 758 cm-1. Vibrational self-consistent field (VSCF)/virtual state configuration interaction (VCI) MULTIMODE calculations of intramolecular fundamentals are reported and are in good agreement with available experimental results. Finally, the full dimer PES is combined with an existing ab initio water potential to develop a potential for the CO2 hydrate clathrate CO2(H2O)20(512 water cage). A full normal-mode analysis of this hydrate clathrate is reported as are local-monomer VSCF/VCI calculations of the fundamentals of CO2.

  10. Electrochemical stability of ionic clathrate hydrates and their structural consideration

    International Nuclear Information System (INIS)

    Lee, Wonhee; Lim, Dongwook; Lee, Huen

    2013-01-01

    Although electrochemical stability is an essential factor in relation to the potential applications of ionic clathrate hydrates to solid electrolytes, most studies regarding the proton conductors have focused on their ionic conductivity and thermal stability. Solid electrolytes in various electrochemical devices have to endure the applied potentials; thus, we examined the linear sweep voltammograms of various tetraalkylammonium hydroxide hydrates in order to shed light on the trend of electrochemical stability depending on the hydrate structure. We revealed that the electrochemical stability of Me 4 NOH hydrates is mainly affected by both their ionic concentration and cage occupancy. In particular, the true clathrate structures of β-Me 4 NOH hydrates are more electrochemically stable than their α-forms that possess partially broken hydrogen bonds. We also observed that the binary THF–Pr 4 NOH and pure Bu 4 NOH clathrate hydrates exhibit greater electrochemical stability than those of pure Me 4 NOH hydrates having lower or similar ionic concentrations. These results are considered to arise from the fact that each of the Pr 4 N + and Bu 4 N + ions occupies an extended space comprising four cages, which leads to stabilization of the larger unit, whereas a Me 4 N + ion is completely included only in one cage

  11. CO_2 capture from flue gas using clathrate formation in the presence of thermodynamic promoters

    International Nuclear Information System (INIS)

    Kim, Soyoung; Choi, Sung-Deuk; Seo, Yongwon

    2017-01-01

    Tetrahydrofuran (THF) as a water-soluble sII clathrate former, cyclopentane (CP) as a water-insoluble sII clathrate former, and tetra n-butyl ammonium chloride (TBAC) as a water-soluble semiclathrate former were used to investigate their thermodynamic promotion effects on clathrate-based CO_2 capture from simulated flue gas. The phase equilibria of CO_2 (20%) + N_2 (80%) + promoter clathrates at different promoter concentrations revealed that the presence of THF, CP, and TBAC could significantly reduce the clathrate formation pressure. THF solutions provided the highest gas uptake and steepest CO_2 concentration changes in the vapor phase, whereas TBAC solutions showed the highest CO_2 selectivity (∼61%) in the clathrate phase. CP solutions exhibited a slower formation rate, but their final gas uptake and CO_2 selectivity in the clathrate phase were comparable to the THF solutions. Raman spectroscopy confirmed the enclathration of both CO_2 and N_2 in the clathrate cages and a structural transition due to the inclusion of promoters in the clathrate phase. The overall experimental results indicate that TBAC is a viable thermodynamic promoter for clathrate-based CO_2 capture from simulated flue gas, considering the lower pressure requirement for clathrate formation, higher CO_2 enrichment in the clathrate phase, non-toxicity, and non-volatility. - Highlights: • Clathrate-based CO_2 capture was investigated in the presence of thermodynamic promoters. • THF, CP, and TBAC demonstrated a significant thermodynamic promotion for CO_2 (20%) + N_2 (80%) clathrates. • The highest gas uptake was observed for the THF (5.6 mol%) solution. • TBAC solutions showed the highest CO_2 selectivity in the clathrate phase (∼61%). • Raman spectroscopy confirmed the guest gas enclathration and clathrate structure.

  12. Molecular simulations and density functional theory calculations of bromine in clathrate hydrate phases

    Energy Technology Data Exchange (ETDEWEB)

    Dureckova, Hana, E-mail: houci059@uottawa.ca; Woo, Tom K., E-mail: tom.woo@uottawa.ca [Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 5N6 (Canada); Alavi, Saman, E-mail: saman.alavi@nrc-cnrc.gc.ca [Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 5N6 (Canada); National Research Council of Canada, 100 Sussex Dr., Ottawa, Ontario K1N 6N5 (Canada); Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, British Columbia V6T 1Z3 (Canada)

    2016-01-28

    Bromine forms a tetragonal clathrate hydrate structure (TS-I) very rarely observed in clathrate hydrates of other guest substances. The detailed structure, energetics, and dynamics of Br{sub 2} and Cl{sub 2} in TS-I and cubic structure I (CS-I) clathrate hydrates are studied in this work using molecular dynamics and quantum chemical calculations. X-ray diffraction studies show that the halogen-water–oxygen distances in the cages of these structures are shorter than the sum of the van der Waals radii of halogen and oxygen atoms. This suggests that the stabilizing effects of halogen bonding or other non-covalent interactions (NCIs) may contribute to the formation of the unique tetragonal bromine hydrate structure. We performed molecular dynamics simulations of Br{sub 2} and Cl{sub 2} clathrate hydrates using our previously developed five-site charge models for the dihalogen molecules [Dureckova et al. Can. J. Chem. 93, 864 (2015)] which reproduce the computed electrostatic potentials of the dihalogens and account for the electropositive σ-hole of the halogen bond donor (the dihalogen). Analysis of the radial distribution functions, enthalpies of encapsulation, velocity and orientation autocorrelation functions, and polar angle distributions are carried out for Br{sub 2} and Cl{sub 2} guests in various cages to contrast the properties of these guests in the TS-I and CS-I phases. Quantum chemical partial geometry optimizations of Br{sub 2} and Cl{sub 2} guests in the hydrate cages using the M06-2X functional give short halogen-water distances compatible with values observed in X-ray diffraction experiments. NCI plots of guest-cage structures are generated to qualitatively show the relative strength of the non-bonding interactions between dihalogens and water molecules. The differences between behaviors of Br{sub 2} and Cl{sub 2} guests in the hydrate cages may explain why bromine forms the unique TS-I phase.

  13. Thermodynamic promotion of carbon dioxide-clathrate hydrate formation by tetrahydrofuran, cyclopentane and their mixtures

    DEFF Research Database (Denmark)

    Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens

    2013-01-01

    Gas clathrate hydrate dissociation pressures are reported for mixtures of carbon dioxide, water and thermodynamic promoters forming structure II hydrates.Hydrate (H)-aqueous liquid (Lw)-vapour (V) equilibrium pressures for the ternary system composed of water, tetrahydrofuran (THF), and carbon....... It is shown that upon adding THF to the pure aqueous phase to form a 4mass percent solution, the equilibrium pressure of the formed hydrates may be lowered compared to the ternary system of water, cyclopentane and carbon dioxide. © 2013 Elsevier Ltd....... dioxide (CO2), with 5.0mole percent THF in the initial aqueous phase, are presented in the temperature range from 283.3K to 285.2K. At 283.3K, the three-phase equilibrium pressure is determined to be 0.61MPa (absolute pressure).Four-phase hydrate (H)-aqueous liquid (Lw)-organic liquid (La)-vapour (V...

  14. Overview: Nucleation of clathrate hydrates.

    Science.gov (United States)

    Warrier, Pramod; Khan, M Naveed; Srivastava, Vishal; Maupin, C Mark; Koh, Carolyn A

    2016-12-07

    Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.

  15. Overview: Nucleation of clathrate hydrates

    Science.gov (United States)

    Warrier, Pramod; Khan, M. Naveed; Srivastava, Vishal; Maupin, C. Mark; Koh, Carolyn A.

    2016-12-01

    Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.

  16. Energy consumption estimation for greenhouse gas separation processes by clathrate hydrate formation

    International Nuclear Information System (INIS)

    Tajima, Hideo; Yamasaki, Akihiro; Kiyono, Fumio

    2004-01-01

    The process energy consumption was estimated for gas separation processes by the formation of clathrate hydrates. The separation process is based on the equilibrium partition of the components between the gaseous phase and the hydrate phase. The separation and capturing processes of greenhouse gases were examined in this study. The target components were hydrofluorocarbon (HFC-134a) from air, sulfur hexafluoride (SF 6 ) from nitrogen, and CO 2 from flue gas. Since these greenhouse gases would form hydrates under much lower pressure and higher temperature conditions than the accompanying components, the effective capturing of the greenhouse gases could be achieved by using hydrate formation. A model separation process for each gaseous mixture was designed from the basis of thermodynamics, and the process energy consumption was estimated. The obtained results were then compared with those for conventional separation processes such as liquefaction separation processes. For the recovery of SF 6 , the hydrate process is preferable to liquefaction process in terms of energy consumption. On the other hand, the liquefaction process consumes less energy than the hydrate process for the recovery of HFC-134a. The capturing of CO 2 by the hydrate process from a flue gas will consume a considerable amount of energy; mainly due to the extremely high pressure conditions required for hydrate formation. The influences of the operation conditions on the heat of hydrate formation were elucidated by sensitivity analysis. The hydrate processes for separating these greenhouse gases were evaluated in terms of reduction of global warming potential (GWP)

  17. Hydration of krypton and consideration of clathrate models of hydrophobic effects from the perspective of quasi-chemical theory.

    Science.gov (United States)

    Ashbaugh, Henry S; Asthagiri, D; Pratt, Lawrence R; Rempe, Susan B

    2003-09-01

    Ab initio molecular dynamics (AIMD) results on a krypton-water liquid solution are presented and compared to recent XAFS results for the radial hydration structure for a Kr atom in liquid water solution. Though these AIMD calculations have important limitations of scale, the comparisons with the liquid solution results are satisfactory and significantly different from the radial distributions extracted from the data on the solid Kr/H(2)O clathrate hydrate phase. The calculations also produce the coordination number distribution that can be examined for metastable coordination structures suggesting possibilities for clathrate-like organization; none are seen in these results. Clathrate pictures of hydrophobic hydration are discussed, as is the quasi-chemical theory that should provide a basis for clathrate pictures. Outer shell contributions are discussed and estimated; they are positive and larger than the positive experimental hydration free energy of Kr(aq), implying that inner shell contributions must be negative and of comparable size. Clathrate-like inner shell hydration structures on a Kr atom solute are obtained for some, but not all, of the coordination number cases observed in the simulation. The structures found have a delicate stability. Inner shell coordination structures extracted from the simulation of the liquid, and then subjected to quantum chemical optimization, always decomposed. Interactions with the outer shell material are decisive in stabilizing coordination structures observed in liquid solution and in clathrate phases. The primitive quasi-chemical estimate that uses a dielectric model for the influence of the outer shell material on the inner shell equilibria gives a contribution to hydration free energy that is positive and larger than the experimental hydration free energy. The 'what are we to tell students' question about hydrophobic hydration, often answered with structural clathrate pictures, is then considered; we propose an

  18. Clathrate hydrates - the energy of the future an overview and a postulated formation mechanism

    International Nuclear Information System (INIS)

    Pratt, R.M.

    2000-01-01

    Clathrate hydrates are non-stoichiometric compounds that form when water and certain low molecular weight hydrocarbons coexist at high pressures and low temperatures. The majority of the earth hydrocarbons are in the hydrate phase and are primarily located along the ocean bottoms and to a lesser degree in the permafrost regions. In addition, hydrate formation is induced in undersea gas transmission lines and causes costly pipeline plugs and requires expensive inhibition measures to be taken. Therefore, both a stick and a carrot motivate hydrate research. They are a costly and dangerous nuisance to the oil and gas industry and represent a tremendous, untapped energy resource of the future. The formation mechanism of clathrate hydrate formation has always been shrouded in mystery, and an ongoing debate has ensued as to whether their formation is a bulk or surface phenomenon. Molecular dynamics simulation and fractal modeling suggest that this may be an irrelevant issue and that two independent factors contribute to the symmetrical ordered structure of clathrate hydrates: hydrophobic hydration of hydrocarbon molecules in water and formation of linked cavities as these small clusters aggregate. (Author)

  19. The anomalous halogen bonding interactions between chlorine and bromine with water in clathrate hydrates.

    Science.gov (United States)

    Dureckova, Hana; Woo, Tom K; Udachin, Konstantin A; Ripmeester, John A; Alavi, Saman

    2017-10-13

    Clathrate hydrate phases of Cl 2 and Br 2 guest molecules have been known for about 200 years. The crystal structure of these phases was recently re-determined with high accuracy by single crystal X-ray diffraction. In these structures, the water oxygen-halogen atom distances are determined to be shorter than the sum of the van der Waals radii, which indicates the action of some type of non-covalent interaction between the dihalogens and water molecules. Given that in the hydrate phases both lone pairs of each water oxygen atom are engaged in hydrogen bonding with other water molecules of the lattice, the nature of the oxygen-halogen interactions may not be the standard halogen bonds characterized recently in the solid state materials and enzyme-substrate compounds. The nature of the halogen-water interactions for the Cl 2 and Br 2 molecules in two isolated clathrate hydrate cages has recently been studied with ab initio calculations and Natural Bond Order analysis (Ochoa-Resendiz et al. J. Chem. Phys. 2016, 145, 161104). Here we present the results of ab initio calculations and natural localized molecular orbital analysis for Cl 2 and Br 2 guests in all cage types observed in the cubic structure I and tetragonal structure I clathrate hydrates to characterize the orbital interactions between the dihalogen guests and water. Calculations with isolated cages and cages with one shell of coordinating molecules are considered. The computational analysis is used to understand the nature of the halogen bonding in these materials and to interpret the guest positions in the hydrate cages obtained from the X-ray crystal structures.

  20. Measurements of relevant parameters in the formation of clathrate hydrates by a novel experimental apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Arca, S.; Di Profio, P.; Germani, R.; Savelli, G. [Perugia Univ., CEMIN, Perugia (Italy). Dept. of Chemistry

    2008-07-01

    There is a growing interest in understanding the thermodynamics and kinetics of clathrate hydrate formation. This paper presented a study that involved the design, construction, calibration, and testing of a new apparatus that could obtain as many parameters as possible in a single formation batch and that could measure unexplored clathrate hydrate parameters. The apparatus was capable of measuring equilibrium phases involving gaseous components. The paper described the conceptual design as well as the chamber, pressure line, temperature control, liquid addition line, and conductometric probe. The paper also discussed data acquisition, stirring, measurement examples, and internal illumination and video monitoring. It was concluded that refining measurements, particularly those concerning kinetic characterizations, is important in order to clarify several uncertain kinetic behaviors of clathrate hydrates. 6 refs., 16 figs.

  1. Phase equilibrium measurements of structure II clathrate hydrates of hydrogen with various promoters

    NARCIS (Netherlands)

    Torres Trueba, A.; Rovetto, L.J.; Florusse, L.J.; Kroon, M.C.; Peters, C.J.

    2011-01-01

    Phase equilibrium measurements of single and mixed organic clathrate hydrates with hydrogen were determined within a pressure range of 2.0–14.0 MPa. The organic compounds studied were furan, 2,5-dihydrofuran, tetrahydropyran, 1,3-dioxolane and cyclopentane. These organic compounds are known to form

  2. A statistical method for evaluation of the experimental phase equilibrium data of simple clathrate hydrates

    DEFF Research Database (Denmark)

    Eslamimanesh, Ali; Gharagheizi, Farhad; Mohammadi, Amir H.

    2012-01-01

    We, herein, present a statistical method for diagnostics of the outliers in phase equilibrium data (dissociation data) of simple clathrate hydrates. The applied algorithm is performed on the basis of the Leverage mathematical approach, in which the statistical Hat matrix, Williams Plot, and the r......We, herein, present a statistical method for diagnostics of the outliers in phase equilibrium data (dissociation data) of simple clathrate hydrates. The applied algorithm is performed on the basis of the Leverage mathematical approach, in which the statistical Hat matrix, Williams Plot...... in exponential form is used to represent/predict the hydrate dissociation pressures for three-phase equilibrium conditions (liquid water/ice–vapor-hydrate). The investigated hydrate formers are methane, ethane, propane, carbon dioxide, nitrogen, and hydrogen sulfide. It is interpreted from the obtained results...

  3. Accurate description of phase diagram of clathrate hydrates on molecular level

    Energy Technology Data Exchange (ETDEWEB)

    Belosludov, V.; Subbotin, O. [Niklaev Inst. of Inorganic Chemistry, Novosibirsk (Russian Federation). Siberian Branch of Russian Academy of Science; Belosludov, R.; Mizuseki, H.; Kawazoe, Y. [Tohoku Univ., Aoba-ku, Sendai (Japan). Inst. for Materials Research

    2008-07-01

    A number of experimental and theoretical studies of hydrogen hydrates have been conducted using different methods. In order to accurately estimate the thermodynamic properties of clathrate hydrates that multiply filling the cages, this paper presented a method based on the solid solution theory of van der Waals and Platteeuw with several modifications, including multiple occupancies, host relaxation, and the description of the quantum nature of hydrogen behavior in the cavities. The validity of the proposed approach was verified for argon, methane, and xenon hydrates. The results were in agreement with known experimental data. The model was then used to calculate the curves of monovariant three-phase equilibrium gas-hydrate-ice and the degree of filling of the large and small cavities for pure hydrogen and mixed hydrogen/propane hydrates in a wide range of pressure and at low temperatures. The paper presented the theory, including equations, monovariant equilibria, and computational details. It was concluded that the proposed model accounted for the influence of guest molecules on the host lattice and guest-guest interaction. The model could be used with other inclusion compounds with the same type of composition such as clathrate silicon, zeolites, and inclusion compounds of semiconductor elements. The calculated curves of monovariant equilibrium agree with the experiment. 33 refs., 1 tab., 9 figs.

  4. Pre-combustion capture of carbon dioxide in a fixed bed reactor using the clathrate hydrate process

    International Nuclear Information System (INIS)

    Babu, Ponnivalavan; Kumar, Rajnish; Linga, Praveen

    2013-01-01

    Hydrate based gas separation (HBGS) process with silica sand and silica gel as contact medium was employed to capture CO 2 from fuel gas mixture. Gas uptake measurement at three different pressures (7.5, 8.5 and 9.0 MPa) and 274.15 K were conducted for hydrate formation kinetics and overall conversion of water to hydrate, rate of hydrate formation were determined. Water conversion of up to 36% was achieved with silica sand bed compared to 13% conversion in the silica gel bed. Effect of driving force on the rate of hydrate formation and gas consumption was significant in silica sand bed whereas it was found to be insignificant in silica gel bed. Hydrate dissociation experiments by thermal stimulation (at constant pressure) alone and a combination of depressurization and thermal stimulation were carried out for complete recovery of the hydrated gas. A driving force of 23 K was found to be sufficient to recover all the hydrated gas within 1 h. This study indicates that silica sand can be an effective porous media for separation of CO 2 from fuel gas when compared to silica gel. - Highlights: ► The clathrate process for pre-combustion capture of carbon dioxide in a novel fixed bed reactor is presented. ► Performance of two contact media (silica gel and silica sand) was investigated. ► Water to hydrate conversion was higher in a silica sand column. ► A pressure reduction and thermal stimulation approach is presented for a complete recovery of the hydrated gas

  5. Measurement of Clathrate Hydrate Thermodynamic Stability in the Presence of Ammonia

    Science.gov (United States)

    Dunham, Marc

    2012-01-01

    There is a lack of data available for the stability of clathrate hydrates in the presence of ammonia for low-to-moderate pressures in the 0-10 MPa range. Providing such data will allow for a better understanding of natural mass transfer processes on celestial bodies like Titan and Enceladus, on which destabilization of clathrates may be responsible for replenishment of gases in the atmosphere. The experimental process utilizes a custom-built gas handling system (GHS) and a cryogenic calorimeter to allow for the efficient testing of samples under varying pressures and gas species.

  6. In situ Low-temperature Pair Distribution Function (PDF) Analysis of CH4 and CO2 Hydrates

    Science.gov (United States)

    Cladek, B.; Everett, M.; McDonnell, M.; Tucker, M.; Keffer, D.; Rawn, C.

    2017-12-01

    Gas hydrates occur in ocean floor and sub-surface permafrost deposits and are stable at moderate to high pressures and low temperatures. They are a clathrate structure composed of hydrogen bonded water cages that accommodate a wide variety of guest molecules. CO2 and CH4 hydrates both crystallize as the cubic sI hydrate and can form a solid solution. Natural gas hydrates are interesting as a potential methane source and for CO2 sequestration. Long-range diffraction studies on gas hydrates give valuable structural information but do not provide a detailed understanding of the disordered gas molecule interactions with the host lattice. In-situ low temperature total scattering experiments combined with pair distribution function (PDF) analysis are used to investigate the gas molecule motions and guest-cage interactions. CO2 and methane hydrates exhibit different decomposition behavior, and CO2 hydrate has a smaller lattice parameter despite it being a relatively larger molecule. Total scattering studies characterizing both the short- and long-range order simultaneously help to elucidate the structural source of these phenomena. Low temperature neutron total scattering data were collected using the Nanoscale Ordered MAterials Diffractometer (NOMAD) beamline at the Spallation Neutron Source (SNS) on CO2 and CH4 hydrates synthesized with D2O. Guest molecule motion within cages and interactions between gases and cages are investigated through the hydrate stability and decomposition regions. Data were collected from 2-80 K at a pressure of 55 mbar on CO2 and CH4 hydrates, and from 80-270 K at 25 bar on CH4 hydrate. The hydrate systems were modeled with classical molecular dynamic (MD) simulations to provide an analysis of the total energy into guest-guest, guest-host and host-host contributions. Combined Reitveld and Reverse Monte Carlo (RMC) structure refinement were used to fit models of the data. This combined modeling and simulation characterizes the effects of CO2 and

  7. A consistent and verifiable macroscopic model for the dissolution of liquid CO2 in water under hydrate forming conditions

    International Nuclear Information System (INIS)

    Radhakrishnan, R.; Demurov, A.; Trout, B.L.; Herzog, H.

    2003-01-01

    Direct injection of liquid CO 2 into the ocean has been proposed as one method to reduce the emission levels of CO 2 into the atmosphere. When liquid CO 2 is injected (normally as droplets) at ocean depths >500 m, a solid interfacial region between the CO 2 and the water is observed to form. This region consists of hydrate clathrates and hinders the rate of dissolution of CO 2 . It is, therefore, expected to have a significant impact on the injection of liquid CO 2 into the ocean. Up until now, no consistent and predictive model for the shrinking of droplets of CO 2 under hydrate forming conditions has been proposed. This is because all models proposed to date have had too many unknowns. By computing rates of the physical and chemical processes in hydrates via molecular dynamics simulations, we have been able to determine independently some of these unknowns. We then propose the most reasonable model and use it to make independent predictions of the rates of mass transfer and thickness of the hydrate region. These predictions are compared to measurements, and implications to the rates of shrinkage of CO 2 droplets under varying flow conditions are discussed. (author)

  8. Hydrogen storage in double clathrates with tert-butylamine.

    Science.gov (United States)

    Prasad, Pinnelli S R; Sugahara, Takeshi; Sum, Amadeu K; Sloan, E Dendy; Koh, Carolyn A

    2009-06-18

    The first proof-of-concept of the formation of a double tert-butylamine (t-BuNH(2)) + hydrogen (H(2)) clathrate hydrate has been demonstrated. Binary clathrate hydrates with different molar concentrations of the large guest t-BuNH(2) (0.98-9.31 mol %) were synthesized at 13.8 MPa and 250 K, and characterized by powder X-ray diffraction and Raman microscopy. A structural transformation from sVI to sII of t-BuNH(2) hydrate was clearly observed under hydrogen pressures. Raman spectroscopic data suggested that the hydrogen molecules occupied the small cages and had similar occupancy to hydrogen in the double tetrahydrofuran (THF) + H(2) clathrate hydrate. The hydrogen storage capacity in this system was approximately 0.7 H(2) wt % at the molar concentration of t-BuNH(2) close to the sII stoichiometry.

  9. Towards CO2 sequestration and applications of CO2 hydrates: the effects of tetrahydrofuran on the phase equilibria of CO2 hydrates

    International Nuclear Information System (INIS)

    Khalik, M.S.; Peters, C.J.

    2006-01-01

    The increasing quantity of carbon dioxide (CO 2 ) in the atmosphere has caused widespread global concerns. Capturing CO 2 from its sources and stored it in the form of gas hydrates and application of CO 2 hydrates are among the proposed methods to overcome this problem. In order to make hydrate-based process more attractive, the use of cyclic ethers as promoters is suggested to reduce the required hydrate formation pressure and enhancing the corresponding kinetic rate. In the present work, tetrahydrofuran (THF) is chosen as a hydrate promoter, participating in forming hydrates and produces mixed hydrate together with CO 2 . The pressure and temperature ranges of hydrate stability region are carefully determined through phase equilibrium measurement of the ternary CO 2 , tetrahydrofuran (THF) and water systems. From the experimental results, it is confirmed that the presence of THF in CO 2 + water systems will extend the hydrate formation region to higher temperature at a constant pressure. The extension of the hydrate stability region is depended on the overall concentration of the ternary system. Moreover, four-phase equilibrium of H-Lw-Lv-V is observed in the system, which may be due to a liquid phase split. In the region where the four-phase equilibrium exists, the ternary system loses its concentration dependency of the hydrate equilibrium conditions. (Author)

  10. The effect of the condensed-phase environment on the vibrational frequency shift of a hydrogen molecule inside clathrate hydrates.

    Science.gov (United States)

    Powers, Anna; Scribano, Yohann; Lauvergnat, David; Mebe, Elsy; Benoit, David M; Bačić, Zlatko

    2018-04-14

    We report a theoretical study of the frequency shift (redshift) of the stretching fundamental transition of an H 2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the vibrational frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H 2 in the v=0 and v=1 vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H 2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H 2 inside a hydrate domain is assumed to be pairwise additive. The H 2 -H 2 O pair interaction, represented by the 5D (rigid monomer) PES that depends on the vibrational state of H 2 , v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H 2 -H 2 O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H 2 vibrational frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H 2 change very little with the domain size, unlike the H 2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the vibrational frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H 2 O molecules in the first three complete hydration shells around H 2 .

  11. The effect of the condensed-phase environment on the vibrational frequency shift of a hydrogen molecule inside clathrate hydrates

    Science.gov (United States)

    Powers, Anna; Scribano, Yohann; Lauvergnat, David; Mebe, Elsy; Benoit, David M.; Bačić, Zlatko

    2018-04-01

    We report a theoretical study of the frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the vibrational frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v =0 and v =1 vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2-H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the vibrational state of H2, v =0 or v =1 , is derived from the high-quality ab initio full-dimensional (9D) PES of the H2-H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 vibrational frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the vibrational frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.

  12. Growth mode transition of tetrahydrofuran clathrate hydrates in the guest/host concentration boundary layer.

    Science.gov (United States)

    Sabase, Yuichiro; Nagashima, Kazushige

    2009-11-19

    Clathrate hydrates are known to form a thin film along a guest/host boundary. We present here the first report of tetrahydrofuran (THF) clathrate hydrate formation in a THF/water concentration boundary layer. We found that the THF-water system also forms a hydrate film separating the guest/host phases. The lateral growth rate of the film increases as supercooling increases. The thickness of the film at the growth tip decreases as supercooling and the lateral growth rate increase. These tendencies are consistent with reports of experiments for other hydrates and predictions of heat-transfer models. After film formation and slight melting, two types of growth modes are observed, depending on temperature T. At T = 3.0 degrees C, the film slowly thickens. The thickening rate is much lower than the lateral growth rate, as reported for other hydrates. At T agglomerate of small polycrystalline hydrates forms in each phase. Grain boundaries in the film and pore spaces in the agglomerate act as paths for permeation of each liquid. Timing when continuous nucleation starts is dominantly controlled by the time of initiation of liquid permeation through the film. Digital particle image velocimetry analysis of the agglomerate shows that it expands not by growth at the advancing front but rather by continuous nucleation in the interior. Expansion rates of the agglomerate tend to be higher for the cases of multipermeation paths in the film and the thinner film. We suppose that the growth mode transition to continuous nucleation is caused by the memory effect due to slight melting of the hydrate film.

  13. Thermodynamic stability and guest distribution of CH4/N2/CO2 mixed hydrates for methane hydrate production using N2/CO2 injection

    International Nuclear Information System (INIS)

    Lim, Dongwook; Ro, Hyeyoon; Seo, Yongwon; Seo, Young-ju; Lee, Joo Yong; Kim, Se-Joon; Lee, Jaehyoung; Lee, Huen

    2017-01-01

    Highlights: • We examine the thermodynamic stability and guest distribution of CH 4 /N 2 /CO 2 mixed hydrates. • Phase equilibria of the CH 4 /N 2 /CO 2 mixed hydrates were measured to determine the thermodynamic stability. • The N 2 /CO 2 ratio of the hydrate phase is almost constant despite the enrichment of CO 2 in the hydrate phase. • 13 C NMR results indicate the preferential occupation of N 2 and CO 2 in the small and large cages of sI hydrates, respectively. - Abstract: In this study, thermodynamic stability and cage occupation behavior in the CH 4 – CO 2 replacement, which occurs in natural gas hydrate reservoirs by injecting flue gas, were investigated with a primary focus on phase equilibria and composition analysis. The phase equilibria of CH 4 /N 2 /CO 2 mixed hydrates with various compositions were measured to determine the thermodynamic stability of gas hydrate deposits replaced by N 2 /CO 2 gas mixtures. The fractional experimental pressure differences (Δp/p) with respect to the CSMGem predictions were found to range from −0.11 to −0.02. The composition analysis for various feed gas mixtures with a fixed N 2 /CO 2 ratio (4.0) shows that CO 2 is enriched in the hydrate phase, and the N 2 /CO 2 ratio in the hydrate phase is independent of the feed CH 4 fractions. Moreover, 13 C NMR measurements indicate that N 2 molecules preferentially occupy the small 5 12 cages of sI hydrates while the CO 2 molecules preferentially occupy the large 5 12 6 2 cages, resulting in an almost constant area ratio of CH 4 molecules in the large to small cages of the CH 4 /N 2 /CO 2 mixed hydrates. The overall experimental results provide a better understanding of stability conditions and guest distributions in natural gas hydrate deposits during CH 4 – flue gas replacement.

  14. Lattice dynamics study of low energy guest–host coupling in clathrate hydrate

    International Nuclear Information System (INIS)

    Yang Yuehai; Dong Shunle; Wang Lin

    2008-01-01

    Our lattice dynamics simulation of Xe-hydrate with four-site TIP4P oxygen-shell model can accurately reproduce each peak position in the inelastic incoherent neutron scattering spectrum at the acoustic band (below 15meV) and yield correct relative intensity. Based on the results, the uncertain profile at ∼6 meV is assigned to anharmonic guest modes coupled strongly to small cages. Blue shift is proposed in phonon dispersion sheet in the case of anticrossing and found to be an evident signal for guest-host coupling that explains the anomalous thermal conductivity of clathrate hydrate

  15. Micro-Tomographic Investigation of Ice and Clathrate Formation and Decomposition under Thermodynamic Monitoring

    Directory of Open Access Journals (Sweden)

    Stefan Arzbacher

    2016-08-01

    Full Text Available Clathrate hydrates are inclusion compounds in which guest molecules are trapped in a host lattice formed by water molecules. They are considered an interesting option for future energy supply and storage technologies. In the current paper, time lapse 3D micro computed tomographic (µCT imaging with ice and tetrahydrofuran (THF clathrate hydrate particles is carried out in conjunction with an accurate temperature control and pressure monitoring. µCT imaging reveals similar behavior of the ice and the THF clathrate hydrate at low temperatures while at higher temperatures (3 K below the melting point, significant differences can be observed. Strong indications for micropores are found in the ice as well as the THF clathrate hydrate. They are stable in the ice while unstable in the clathrate hydrate at temperatures slightly below the melting point. Significant transformations in surface and bulk structure can be observed within the full temperature range investigated in both the ice and the THF clathrate hydrate. Additionally, our results point towards an uptake of molecular nitrogen in the THF clathrate hydrate at ambient pressures and temperatures from 230 K to 271 K.

  16. In situ NMR studies of hydrogen storage kinetics and molecular diffusion in clathrate hydrate at elevated hydrogen pressures

    Energy Technology Data Exchange (ETDEWEB)

    Okuchi, T. [Okayama Univ., Misasa, Tottori (Japan); Moudrakovski, I.L.; Ripmeester, J.A. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences

    2008-07-01

    The challenge of storing high-density hydrogen into compact host media was investigated. The conventional storage scheme where an aqueous solution is frozen with hydrogen gas is too slow for practical use in a hydrogen-based society. Therefore, the authors developed a faster method whereby hydrogen was stored into gas hydrates. The hydrogen gas was directly charged into hydrogen-free, crystalline hydrate powders with partly empty lattices. The storage kinetics and hydrogen diffusion into the hydrate was observed in situ by nuclear magnetic resonance (NMR) in a pressurized tube cell. At pressures up to 20 MPa, the storage was complete within 80 minutes, as observed by growth of stored-hydrogen peak into the hydrate. Hydrogen diffusion within the crystalline hydrate media is the rate-determining step of current storage scheme. Therefore, the authors measured the diffusion coefficient of hydrogen molecules using the pulsed field gradient NMR method. The results show that the stored hydrogen is very mobile at temperatures down to 250 K. As such, the powdered hydrate media should work well even in cold environments. Compared with more prevailing hydrogen storage media such as metal hydrides, clathrate hydrates have the advantage of being free from hydrogen embrittlement, more chemically durable, more environmentally sound, and economically affordable. It was concluded that the powdered clathrate hydrate is suitable as a hydrogen storage media. 22 refs., 4 figs.

  17. Competing quantum effects in the free energy profiles and diffusion rates of hydrogen and deuterium molecules through clathrate hydrates.

    Science.gov (United States)

    Cendagorta, Joseph R; Powers, Anna; Hele, Timothy J H; Marsalek, Ondrej; Bačić, Zlatko; Tuckerman, Mark E

    2016-11-30

    Clathrate hydrates hold considerable promise as safe and economical materials for hydrogen storage. Here we present a quantum mechanical study of H 2 and D 2 diffusion through a hexagonal face shared by two large cages of clathrate hydrates over a wide range of temperatures. Path integral molecular dynamics simulations are used to compute the free-energy profiles for the diffusion of H 2 and D 2 as a function of temperature. Ring polymer molecular dynamics rate theory, incorporating both exact quantum statistics and approximate quantum dynamical effects, is utilized in the calculations of the H 2 and D 2 diffusion rates in a broad temperature interval. We find that the shape of the quantum free-energy profiles and their height relative to the classical free energy barriers at a given temperature, as well as the rate of diffusion, are strongly affected by competing quantum effects: above 25 K, zero-point energy (ZPE) perpendicular to the reaction path for diffusion between cavities decreases the quantum rate compared to the classical rate, whereas at lower temperatures tunneling outcompetes the ZPE and as a result the quantum rate is greater than the classical rate.

  18. Phase equilibria of carbon dioxide and methane gas-hydrates predicted with the modified analytical S-L-V equation of state

    Directory of Open Access Journals (Sweden)

    Span Roland

    2012-04-01

    Full Text Available Gas-hydrates (clathrates are non-stoichiometric crystallized solutions of gas molecules in the metastable water lattice. Two or more components are associated without ordinary chemical union but through complete enclosure of gas molecules in a framework of water molecules linked together by hydrogen bonds. The clathrates are important in the following applications: the pipeline blockage in natural gas industry, potential energy source in the form of natural hydrates present in ocean bottom, and the CO2 separation and storage. In this study, we have modified an analytical solid-liquid-vapor equation of state (EoS [A. Yokozeki, Fluid Phase Equil. 222–223 (2004] to improve its ability for modeling the phase equilibria of clathrates. The EoS can predict the formation conditions for CO2- and CH4-hydrates. It will be used as an initial estimate for a more complicated hydrate model based on the fundamental EoSs for fluid phases.

  19. Computational characterization of 13C NMR lineshapes of carbon dioxide in structure 1 clathrate hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Dornan, P.; Woo, T.K. [Ottawa Univ., ON (Canada). Dept. of Chemistry

    2008-07-01

    Nonspherical large cages in structure one clathrates impose non-uniform motion of nonspherical guest molecules and anisotropic lineshapes in nuclear magnetic resonance (NMR) spectra of the guest. This paper presented a general method for calculating the chemical shift lineshape anisotropy of guest molecules in clathrate hydrate compounds from molecular dynamics simulations for the case of weak host, guest dipolar coupling. In order to calculate the cage chemical shielding tensors and the NMR lineshape produced by each guest molecule, the study involved the use of orientational distributions from molecular dynamics simulation along with time and powder angle averaging. The total predicted lineshape anisotropy was calculated from the superposition of the lineshapes of all guests. The approach was applied to calculate the temperature dependent 13C NMR lineshape anisotropy of carbon dioxide in structure 1 clathrates. The paper presented the computational methodology and results and discussion. It was concluded that the resulting lineshapes were in good agreement with the experimental 13C NMR spectrum at each temperature. The method provided a uniform procedure to calculate the lineshapes at different temperatures and no prior assumptions about the nature of the motion of the guest in cages was required. 37 refs., 2 tabs., 3 figs.

  20. Fire extinction utilizing carbon dioxide hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Hatakeyama, T.; Aida, E.; Yokomori, T.; Ohmura, R.; Ueda, T. [Keio Univ., Hiyoshi, Kohoku-ku, Yokohama (Japan)

    2008-07-01

    Clathrate hydrates formed with nonflammable gases may be suitable for use as fire extinguishing agents because dissociation of the hydrates results in the temperature decrease in the combustion field and the nonflammable gases released from the dissociated hydrates prevent the supply of the oxygen to the combustion field. This paper discussed experiments in which ordinary ice and dry ice were used to evaluate the performance of CO{sub 2} hydrate as a fire extinguishing agent. The paper described the apparatus and procedure for the preparation of CO{sub 2} hydrate crystals. A schematic of the reactor to form CO{sub 2} hydrate and a photograph of CO{sub 2} hydrate crystal formed in the study were also presented. Other illustrations, photographs, and tables that were presented included a schematic diagram of the experimental apparatus used for the flame extinction experiments; a photograph of CO{sub 2} hydrate powder; sequential video graphs of the flame extinction by the supply of CO{sub 2} hydrate crystals to the methanol pool flame and the relevant illustration; and heat of CO{sub 2} hydrate dissociation, water vaporization and sublimation of dry ice. It was concluded that the critical mass of the CO{sub 2} hydrate required to extinguish a flame was much less than that of ordinary ice, indicating the superiority of CO{sub 2} hydrate to the ice. In addition, the experiments also revealed that the size of the CO{sub 2} hydrate particles had a significant effect on the performance of flame extinction. 5 refs., 2 tabs., 7 figs.

  1. Feasibility of Large-Scale Ocean CO2 Sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Peter Brewer

    2008-08-31

    Scientific knowledge of natural clathrate hydrates has grown enormously over the past decade, with spectacular new findings of large exposures of complex hydrates on the sea floor, the development of new tools for examining the solid phase in situ, significant progress in modeling natural hydrate systems, and the discovery of exotic hydrates associated with sea floor venting of liquid CO{sub 2}. Major unresolved questions remain about the role of hydrates in response to climate change today, and correlations between the hydrate reservoir of Earth and the stable isotopic evidence of massive hydrate dissociation in the geologic past. The examination of hydrates as a possible energy resource is proceeding apace for the subpermafrost accumulations in the Arctic, but serious questions remain about the viability of marine hydrates as an economic resource. New and energetic explorations by nations such as India and China are quickly uncovering large hydrate findings on their continental shelves. In this report we detail research carried out in the period October 1, 2007 through September 30, 2008. The primary body of work is contained in a formal publication attached as Appendix 1 to this report. In brief we have surveyed the recent literature with respect to the natural occurrence of clathrate hydrates (with a special emphasis on methane hydrates), the tools used to investigate them and their potential as a new source of natural gas for energy production.

  2. Enclathration of CO2 as a co-guest of structure H hydrates and its implications for CO2 capture and sequestration

    International Nuclear Information System (INIS)

    Lee, Yohan; Lee, Dongyoung; Lee, Jong-Won; Seo, Yongwon

    2016-01-01

    Highlights: • We examine sH hydrates with CO 2 + N 2 + neohexane for CO 2 capture and sequestration. • The structural transition occurs in the CO 2 (40%) + N 2 (60%) + neohexane system. • CO 2 molecules are enclathrated into sH hydrates in the N 2 -rich systems. • CO 2 selectivity in sH hydrates is slightly lower than that in sI hydrates. • ΔH d values provide information on the structural transition of sH to sI hydrates. - Abstract: In this study, the thermodynamic behaviors, cage-specific guest distributions, structural transition, and dissociation enthalpies of sH hydrates with CO 2 + N 2 gas mixtures were investigated for their potential applications to hydrate-based CO 2 capture and sequestration. The stability conditions of the CO 2 + N 2 + water systems and the CO 2 + N 2 + neohexane (2,2-dimethylbutane, NH) + water systems indicated that the gas mixtures in the range of flue gas compositions could form sH hydrates, thereby mitigating the pressure and temperature required for gas hydrate formation. Structure identification using powder X-ray diffraction (PXRD) revealed the coexistence of sI and sH hydrates in the CO 2 (40%) + N 2 (60%) + NH system and the hydrate structure transformed from sH into sI as the CO 2 concentration increased. In addition, the Raman analysis clearly demonstrated that CO 2 molecules were enclathrated into the cages of sH hydrates in the N 2 -rich systems. It was found from direct CO 2 composition measurements that CO 2 selectivity in the sH hydrate phase was slightly lower than that in the corresponding sI hydrate phase. Dissociation enthalpy (ΔH d ) measurements using a high-pressure micro-differential scanning calorimeter (HP μ-DSC) indicated that the ΔH d values could also provide valuable information on the structural transition of sH to sI hydrates with respect to the CO 2 concentration in the feed gas. This study provides a better understanding of the thermodynamic and physicochemical background for CO 2

  3. Cryogenic-SEM investigation of CO{sub 2} hydrate morphologies

    Energy Technology Data Exchange (ETDEWEB)

    Camps, A.P.; Milodowski, A.; Rochelle, C.; Williams, J.F.; Jackson, P. D. [British Geological Survey, Keyworth, Nottinghamshire (United Kingdom); Camps, A.P; Lovell, M.; Williams, J.F. [Leicester Univ., Leicester (United Kingdom). Dept. of Geology

    2008-07-01

    Gas hydrates occur naturally around the world in the shallow-marine geosphere, and are seen as a drilling hazard in the petroleum industry due to their role in the carbon cycle, and their possible contribution in past and present climate change. Hydrates are ice-like structures composed of cages of water molecules containing one or more guest molecules, such as methane and carbon dioxide (CO{sub 2}). CO{sub 2} hydrates also occur naturally on earth and are being investigated for their potential to store large volumes of CO{sub 2} to reduce atmospheric emissions of greenhouse gases as a climate change mitigation strategy. However, the mineralogy and formation processes of hydrates are relatively poorly understood. Different imaging techniques have been utilized to study gas hydrates, such as nuclear magnetic resonance, magnetic resonance imaging, and x-ray computed tomography. Scanning Electron Microscopy (SEM) at cryogenic temperatures is another technique to study hydrates, and has been used successfully for investigation of methane and CO{sub 2} hydrates. This paper presented a study that investigated CO{sub 2} hydrates formed in laboratories, using a cryogenic-SEM. The paper presented the study methods and observations, including euhedral crystalline carbon dioxide hydrate; acicular carbon dioxide hydrate; granoblastic carbon dioxide hydrate; and gas rich carbon dioxide hydrate. It was concluded that the investigation produced various different hydrate morphologies resulting from different formation conditions. Morphologies ranged from well-defined euhedral crystals to acicular needles, and more complex, intricate forms. 22 refs., 6 figs., 1 appendix.

  4. Major occurrences and reservoir concepts of marine clathrate hydrates: Implications of field evidence

    Science.gov (United States)

    Booth, J.S.; Winters, W.J.; Dillon, William P.; Clennell, M.B.; Rowe, M.M.

    1998-01-01

    This paper is part of the special publication Gas hydrates: relevance to world margin stability and climatic change (eds J.P. Henriet and J. Mienert). Questions concerning clathrate hydrate as an energy resource, as a factor in modifying global climate and as a triggering mechanism for mass movements invite consideration of what factors promote hydrate concentration, and what the quintessential hydrate-rich sediment may be. Gas hydrate field data, although limited, provide a starting point for identifying the environments and processes that lead to more massive concentrations. Gas hydrate zones are up to 30 m thick and the vertical range of occurrence at a site may exceed 200 m. Zones typically occur more than 100m above the phase boundary. Thicker zones are overwhelmingly associated with structural features and tectonism, and often contain sand. It is unclear whether an apparent association between zone thickness and porosity represents a cause-and-effect relationship. The primary control on the thickness of a potential gas hydrate reservoir is the geological setting. Deep water and low geothermal gradients foster thick gas hydrate stability zones (GHSZs). The presence of faults, fractures, etc. can favour migration of gas-rich fluids. Geological processes, such as eustacy or subsidence, may alter the thickness of the GHSZ or affect hydrate concentratiion. Tectonic forces may promote injection of gas into the GHSZ. More porous and permeable sediment, as host sediment properties, increase storage capacity and fluid conductivity, and thus also enhance reservoir potential.

  5. Carbon and energy footprint of the hydrate-based biogas upgrading process integrated with CO2 valorization.

    Science.gov (United States)

    Castellani, Beatrice; Rinaldi, Sara; Bonamente, Emanuele; Nicolini, Andrea; Rossi, Federico; Cotana, Franco

    2018-02-15

    The present paper aims at assessing the carbon and energy footprint of an energy process, in which the energy excess from intermittent renewable sources is used to produce hydrogen which reacts with the CO 2 previously separated from an innovative biogas upgrading process. The process integrates a hydrate-based biogas upgrading section and a CO 2 methanation section, to produce biomethane from the biogas enrichment and synthetic methane from the CO 2 methanation. Clathrate hydrates are crystalline compounds, formed by gas enclathrated in cages of water molecules and are applied to the selective separation of CO 2 from biogas mixtures. Data from the experimental setup were analyzed in order to evaluate the green-house gas emissions (carbon footprint CF) and the primary energy consumption (energy footprint EF) associated to the two sections of the process. The biosynthetic methane production during a single-stage process was 0.962Nm 3 , obtained mixing 0.830Nm 3 of methane-enriched biogas and 0.132Nm 3 of synthetic methane. The final volume composition was: 73.82% CH 4 , 19.47% CO 2 , 0.67% H 2 , 1.98% O 2 , 4.06% N 2 and the energy content was 28.0MJ/Nm 3 . The functional unit is the unitary amount of produced biosynthetic methane in Nm 3 . Carbon and energy footprints are 0.7081kgCO 2eq /Nm 3 and 28.55MJ/Nm 3 , respectively, when the electric energy required by the process is provided by photovoltaic panels. In this scenario, the overall energy efficiency is about 0.82, higher than the worldwide average energy efficiency for fossil methane, which is 0.75. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Formation and dissociation of CO{sub 2} and CO{sub 2}-THF hydrates compared to CH{sub 4} and CH{sub 4}-THF hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Giavarini, C.; Maccioni, F.; Broggi, A. [Roma Univ. La Sapienza, Roma (Italy). Dept. of Chemical Engineering; Politi, M. [ENEL-RICERCHE, Brindisi (Italy)

    2008-07-01

    Carbon sequestration involves the removal of greenhouse gases from industrial or utility plant streams and their long term storage so that they cannot interact with the climate system. Different methods for selective carbon dioxide (CO{sub 2}) removal are in commercial use and are based on, gas absorption, membrane process, and cryogenic fractionation. In addition, disposal of captured CO{sub 2} in the ocean and in geological reservoirs has been proposed by researchers. Another challenge is to take advantage of the properties of CO{sub 2} hydrates for carbon sequestration since it could have a number of uses such as chemical production. As such, it is important to understand the hydrate decomposition kinetics during storage, transportation, and disposal. This paper presented a project that involved the separation of carbon dioxide from the flue gases of powers plants, in the form of hydrate. The project also involved the storage, use, and disposal of the hydrate. The purpose of the study was to evaluate the decomposition kinetics of CO{sub 2} hydrate containing different quantities of ice, at low pressures and temperatures between -3 and 0 degrees Celsius. In addition, in order to evaluate the tetrahydrofuran (THF) stabilization effect, the study examined the influence of THF on the formation and decomposition kinetics of mixed THF-methane (CH{sub 4}) and THF-CO{sub 2} hydrates. Preservation tests were conducted to determine the best pressure and temperature conditions for the mixed-hydrates conservation, with reference to the simple hydrates. The paper described the apparatus for the formation and dissociation tests which consisted of a jacketed stainless steel reactor, equipped with stirrer. The paper also described the hydrate formation procedure as well as hydrate characterization. Last, the paper discussed the hydrate dissociation tests that were conducted immediately after hydrate formation in the reactor. It was concluded that the hydrophilic and hydrophobic

  7. Determining the flux of methane into Hudson Canyon at the edge of methane clathrate hydrate stability

    Science.gov (United States)

    Weinsten, A.; Navarrete, L; Ruppel, Carolyn D.; Weber, T.C.; Leonte, M.; Kellermann, M.; Arrington, E.; Valentine, D.L.; Scranton, M.L; Kessler, John D.

    2016-01-01

    Methane seeps were investigated in Hudson Canyon, the largest shelf-break canyon on the northern US Atlantic Margin. The seeps investigated are located at or updip of the nominal limit of methane clathrate hydrate stability. The acoustic identification of bubble streams was used to guide water column sampling in a 32 km2 region within the canyon's thalweg. By incorporating measurements of dissolved methane concentration with methane oxidation rates and current velocity into a steady-state box model, the total emission of methane to the water column in this region was estimated to be 12 kmol methane per day (range: 6 – 24 kmol methane per day). These analyses suggest this methane is largely retained inside the canyon walls below 300 m water depth, and that it is aerobically oxidized to near completion within the larger extent of Hudson Canyon. Based on estimated methane emissions and measured oxidation rates, the oxidation of this methane to dissolved CO2 is expected to have minimal influences on seawater pH. This article is protected by copyright. All rights reserved.

  8. Gas hydrates and clathrates. Flow assurance, environmental and economic perspectives and the Nigerian liquefied natural gas project

    International Nuclear Information System (INIS)

    Gbaruko, B.C.; Igwe, J.C.; Nwokeoma, R.C.; Gbaruko, P.N.

    2007-01-01

    Gas hydrates are nonstoichiometric crystalline compounds that belong to the inclusion group known as clathrates. They occur when water molecules attach themselves together through hydrogen bonding and form cavities which can be occupied by a single gas or volatile liquid molecule. Gas hydrates, asphaltenes and waxes are three major threats to flow assurance that must be well assessed by design team uptime. Gas hydrates are also looked upon as a future energy source and as a potential climate hazard. The purpose of this review is to show the chemistry and mechanism of gas hydrate formation, the problems they pose, especially to flow assurance, their system implications, their environmental and economic perspectives with respect to their prospects as storage and transport alternative to the liquefied natural gas technology. (author)

  9. Thermodynamic and Process Modelling of Gas Hydrate Systems in CO2 Capture Processes

    DEFF Research Database (Denmark)

    Herslund, Peter Jørgensen

    A novel gas separation technique based on gas hydrate formation (solid precipitation) is investigated by means of thermodynamic modeling and experimental investigations. This process has previously been proposed for application in post-combustion carbon dioxide capture from power station flue gases...... formation may be performed at pressures of approximately 20 MPa and temperatures below 280 K. Thermodynamic promoters are needed, to reduce the pressure requirement of the process, thereby making it competitive to existing capture technologies. A literature study is presented focusing mainly...... on thermodynamic gas hydrate promotion by hydrate formers stabilising the classical gas clathrate hydrate structures (sI, sII and sH) at low to moderate pressures. Much literature is available on this subject. Both experimental and theoretical studies presented in the literature have pointed out cyclopentane...

  10. CO2 capture by gas hydrate crystallization: Application on the CO2-N2 mixture

    International Nuclear Information System (INIS)

    Bouchemoua, A.

    2012-01-01

    CO 2 capture and sequestration represent a major industrial and scientific challenge of this century. There are different methods of CO 2 separation and capture, such as solid adsorption, amines adsorption and cryogenic fractionation. Although these processes are well developed at industrial level, they are energy intensive. Hydrate formation method is a less energy intensive and has an interesting potential to separate carbon dioxide. Gas hydrates are Document crystalline compounds that consist of hydrogen bonded network of water molecules trapping a gas molecule. Gas hydrate formation is favored by high pressure and low temperature. This study was conducted as a part of the SECOHYA ANR Project. The objective is to study the thermodynamic and kinetic conditions of the process to capture CO 2 by gas hydrate crystallization. Firstly, we developed an experimental apparatus to carry out experiments to determine the thermodynamic and kinetic formation conditions of CO 2 -N 2 gas hydrate mixture in water as liquid phase. We showed that the operative pressure may be very important and the temperature very low. For the feasibility of the project, we used TBAB (Tetrabutylammonium Bromide) as thermodynamic additive in the liquid phase. The use of TBAB may reduce considerably the operative pressure. In the second part of this study, we presented a thermodynamic model, based on the van der Waals and Platteeuw model. This model allows the estimation of thermodynamic equilibrium conditions. Experimental equilibrium data of CO 2 -CH 4 and CO 2 -N 2 mixtures are presented and compared to theoretical results. (author)

  11. Effects of cyclopentane on CO2 hydrate formation and dissociation as a co-guest molecule for desalination

    International Nuclear Information System (INIS)

    Zheng, Jia-nan; Yang, Ming-jun; Liu, Yu; Wang, Da-yong; Song, Yong-chen

    2017-01-01

    Highlights: • CP decreases CO 2 hydrate phase equilibrium pressure by forming CO 2 -CP hydrates. • The increase of CP can’t decrease hydrates phase equilibrium pressure unlimitedly. • Higher CP concentration lowers CO 2 hydrate gas uptake. • The optimal CP molar ratio is 0.01 based on hydrate phase equilibrium and gas uptake. - Abstract: Cyclopentane (CP) is considered to be a potential co-guest molecule in carbon dioxide (CO 2 ) hydrate-based desalination. The experimental thermodynamic data of CO 2 -CP hydrates were measured for a salt solution, where CP was chosen as a hydrate promoter. Seven experimental cases (62 cycles) were studied with different molar ratios of CP/water (0, 0.0025, 0.005, 0.0075, 0.01, 0.02, and 0.03). Hydrate phase equilibrium data were generated using an isochoric method, and the hydrate saturations were calculated based on gas uptake. The results indicated that the increase in CP concentration significantly decreased the CO 2 hydrate equilibrium pressure to a certain limit; the hydrate saturation also decreased during this process. Also, it was determined that CP encouraged the formation of s-II double CO 2 -CP hydrates, which are different from s-I simple CO 2 hydrate. The CO 2 -CP guest provides a strengthened stability and moderate hydrate phase equilibrium conditions for hydrate-based desalination. The recommended optimal molar ratio of CP is 0.01 when the increase in equilibrium was more than 10 K, and the decrease in hydrate saturation was less than 2%.

  12. Molecular dynamics study on the structure I clathrate-hydrate of methane + ethane mixture

    International Nuclear Information System (INIS)

    Erfan-Niya, Hamid; Modarress, Hamid; Zaminpayma, Esmaeil

    2011-01-01

    Molecular dynamics (MD) simulations are used to study the structure I stability of methane + ethane clathrate-hydrates at temperatures 273, 275 and 277 K. NVT- and NPT-ensembles are utilized in MD simulation, and each consists of 3 x 3 x 3 replica unit cells containing 46 water molecules which are considered as the host molecules and up to eight methane + ethane molecules considered as the guest molecules. In MD simulations for host-host interactions, the potential model used was a type of simple point charge (SPC) model, and for guest-guest and host-guest interactions the potential used was Lennard-Jones model. In the process of MD simulation, achieving equilibrium of the studied system was recognized by stability in calculated pressure for NVT-ensemble and volume for NPT-ensemble. To understand the characteristic configurations of the structure I hydrate, the radial distribution functions (RDFs) of host-host, host-guest and guest-guest molecules as well as other properties including kinetic energy, potential energy and total energy were calculated. The results show that guest molecules interaction with host molecules cannot decompose the hydrate structure, and these results are consistent with most previous experimental and theoretical investigations that methane + ethane mixtures form structure I hydrates over the entire mixture composition range.

  13. Chemical-clathrate hybrid hydrogen storage: storage in both guest and host.

    Science.gov (United States)

    Strobel, Timothy A; Kim, Yongkwan; Andrews, Gary S; Ferrell, Jack R; Koh, Carolyn A; Herring, Andrew M; Sloan, E Dendy

    2008-11-12

    Hydrogen storage from two independent sources of the same material represents a novel approach to the hydrogen storage problem, yielding storage capacities greater than either of the individual constituents. Here we report a novel hydrogen storage scheme in which recoverable hydrogen is stored molecularly within clathrate cavities as well as chemically in the clathrate host material. X-ray diffraction and Raman spectroscopic measurements confirm the formation of beta-hydroquinone (beta-HQ) clathrate with molecular hydrogen. Hydrogen within the beta-HQ clathrate vibrates at considerably lower frequency than hydrogen in the free gaseous phase and rotates nondegenerately with splitting comparable to the rotational constant. Compared with water-based clathrate hydrate phases, the beta-HQ+H2 clathrate shows remarkable stability over a range of p-T conditions. Subsequent to clathrate decomposition, the host HQ was used to directly power a PEM fuel cell. With one H2 molecule per cavity, 0.61 wt % hydrogen may be stored in the beta-HQ clathrate cavities. When this amount is combined with complete dehydrogenation of the host hydroxyl hydrogens, the maximum hydrogen storage capacity increases nearly 300% to 2.43 wt %.

  14. The synthesis and the spectroscopic, thermal, and structural properties of the M2[(fumarate)Ni(CN)4]·2(1,4-Dioxane) clathrate (M = Co, Ni, Cd and Hg)

    Science.gov (United States)

    Kartal, Zeki; Yavuz, Abdülkerim

    2018-03-01

    In this study, the clathrates of fumarate-tetracyanonickel-dioxane, given by the formula M2[(fumarate)Ni(CN)4]·2(1,4-Dioxane) (M = Co, Ni, Cd and Hg), have been obtained for the first time through chemical methods. These clathrates have been characterized by elemental, thermal, FT-IR, and FT-Raman spectroscopies. The parameters of structures of clathrates have been determined by X-ray powder diffraction. The thermal behaviors of these clathrates have been also investigated by thermo-gravimetric analysis (TGA), differential thermal analysis (DTA), and derivative thermal gravimetric analysis (DTG) in the range of 20-900 °C. X-ray powder diffraction data have been recorded at ambient temperature in the 2θ range 5-50°. The FT-IR and FT-Raman spectra of clathrates have been recorded in the region of 4000-400 cm-1 and 4000-100 cm-1, respectively. The results of the spectral and thermal analyses of the newly synthesized clathrates of fumarate-tetracyanonickel-dioxane suggest that these clathrates are new examples of the Hofmann-type dioxane clathrates. In our study, the Hofmann-type dioxane clathrates, which are formed by bounding electrons of oxygen-donor atoms of fumarate ion ligand molecule to transition metal atoms, consist of the corrugated |M-Ni(CN)4|∞ polymeric layers, which are held in parallel through the chain of (-M-fumarate-M-).

  15. Hydraulic and Mechanical Effects from Gas Hydrate Conversion and Secondary Gas Hydrate Formation during Injection of CO2 into CH4-Hydrate-Bearing Sediments

    Science.gov (United States)

    Bigalke, N.; Deusner, C.; Kossel, E.; Schicks, J. M.; Spangenberg, E.; Priegnitz, M.; Heeschen, K. U.; Abendroth, S.; Thaler, J.; Haeckel, M.

    2014-12-01

    The injection of CO2 into CH4-hydrate-bearing sediments has the potential to drive natural gas production and simultaneously sequester CO2 by hydrate conversion. The process aims at maintaining the in situ hydrate saturation and structure and causing limited impact on soil hydraulic properties and geomechanical stability. However, to increase hydrate conversion yields and rates it must potentially be assisted by thermal stimulation or depressurization. Further, secondary formation of CO2-rich hydrates from pore water and injected CO2 enhances hydrate conversion and CH4 production yields [1]. Technical stimulation and secondary hydrate formation add significant complexity to the bulk conversion process resulting in spatial and temporal effects on hydraulic and geomechanical properties that cannot be predicted by current reservoir simulation codes. In a combined experimental and numerical approach, it is our objective to elucidate both hydraulic and mechanical effects of CO2 injection and CH4-CO2-hydrate conversion in CH4-hydrate bearing soils. For the experimental approach we used various high-pressure flow-through systems equipped with different online and in situ monitoring tools (e.g. Raman microscopy, MRI and ERT). One particular focus was the design of triaxial cell experimental systems, which enable us to study sample behavior even during large deformations and particle flow. We present results from various flow-through high-pressure experimental studies on different scales, which indicate that hydraulic and geomechanical properties of hydrate-bearing sediments are drastically altered during and after injection of CO2. We discuss the results in light of the competing processes of hydrate dissociation, hydrate conversion and secondary hydrate formation. Our results will also contribute to the understanding of effects of temperature and pressure changes leading to dissociation of gas hydrates in ocean and permafrost systems. [1] Deusner C, Bigalke N, Kossel E

  16. CO2 injection into submarine, CH4-hydrate bearing sediments: Parameter studies towards the development of a hydrate conversion technology

    Science.gov (United States)

    Deusner, Christian; Bigalke, Nikolaus; Kossel, Elke; Haeckel, Matthias

    2013-04-01

    In the recent past, international research efforts towards exploitation of submarine and permafrost hydrate reservoirs have increased substantially. Until now, findings indicate that a combination of different technical means such as depressurization, thermal stimulation and chemical activation is the most promising approach for producing gas from natural hydrates. Moreover, emission neutral exploitation of CH4-hydrates could potentially be achieved in a combined process with CO2 injection and storage as CO2-hydrate. In the German gas hydrate initiative SUGAR, a combination of experimental and numerical studies is used to elucidate the process mechanisms and technical parameters on different scales. Experiments were carried out in the novel high-pressure flow-through system NESSI (Natural Environment Simulator for sub-Seafloor Interactions). Recent findings suggest that the injection of heated, supercritical CO2 is beneficial for both CH4 production and CO2 retention. Among the parameters tested so far are the CO2 injection regime (alternating vs. continuous injection) and the reservoir pressure / temperature conditions. Currently, the influence of CO2 injection temperature is investigated. It was shown that CH4 production is optimal at intermediate reservoir temperatures (8 ° C) compared to lower (2 ° C) and higher temperatures (10 ° C). The reservoir pressure, however, was of minor importance for the production efficiency. At 8 ° C, where CH4- and CO2-hydrates are thermodynamically stable, CO2-hydrate formation appears to be slow. Eventual clogging of fluid conduits due to CO2-rich hydrate formation force open new conduits, thereby tapping different regions inside the CH4-hydrate sample volume for CH4gas. In contrast, at 2 ° C immediate formation of CO2-hydrate results in rapid and irreversible obstruction of the entire pore space. At 10 ° C pure CO2-hydrates can no longer be formed. Consequently the injected CO2 flows through quickly and interaction with

  17. Transport Mechanisms for CO2-CH4 Exchange and Safe CO2 Storage in Hydrate-Bearing Sandstone

    Directory of Open Access Journals (Sweden)

    Knut Arne Birkedal

    2015-05-01

    Full Text Available CO2 injection in hydrate-bearing sediments induces methane (CH4 production while benefitting from CO2 storage, as demonstrated in both core and field scale studies. CH4 hydrates have been formed repeatedly in partially water saturated Bentheim sandstones. Magnetic Resonance Imaging (MRI and CH4 consumption from pump logs have been used to verify final CH4 hydrate saturation. Gas Chromatography (GC in combination with a Mass Flow Meter was used to quantify CH4 recovery during CO2 injection. The overall aim has been to study the impact of CO2 in fractured and non-fractured samples to determine the performance of CO2-induced CH4 hydrate production. Previous efforts focused on diffusion-driven exchange from a fracture volume. This approach was limited by gas dilution, where free and produced CH4 reduced the CO2 concentration and subsequent driving force for both diffusion and exchange. This limitation was targeted by performing experiments where CO2 was injected continuously into the spacer volume to maintain a high driving force. To evaluate the effect of diffusion length multi-fractured core samples were used, which demonstrated that length was not the dominating effect on core scale. An additional set of experiments is presented on non-fractured samples, where diffusion-limited transportation was assisted by continuous CO2 injection and CH4 displacement. Loss of permeability was addressed through binary gas (N2/CO2 injection, which regained injectivity and sustained CO2-CH4 exchange.

  18. Anti-Agglomerator of Tetra-n-Butyl Ammonium Bromide Hydrate and Its Effect on Hydrate-Based CO2 Capture

    Directory of Open Access Journals (Sweden)

    Rong Li

    2018-02-01

    Full Text Available Tetra-n-butyl ammonium bromide (TBAB was widely used in the research fields of cold storage and CO2 hydrate separation due to its high phase change latent heat and thermodynamic promotion for hydrate formation. Agglomeration always occurred in the process of TBAB hydrate generation, which led to the blockage in the pipeline and the separation apparatus. In this work, we screened out a kind of anti-agglomerant that can effectively solve the problem of TBAB hydrate agglomeration. The anti-agglomerant (AA is composed of 90% cocamidopropyl dimethylamine and 10% glycerol, which can keep TBAB hydrate of 19.3–29.0 wt. % in a stable state of slurry over 72 h. The microscopic observation of the morphology of the TBAB hydrate particles showed that the addition of AA can greatly reduce the size of the TBAB hydrate particles. CO2 gas separation experiments found that the addition of AA led to great improvement on gas storage capacity, CO2 split fraction and separation factor, due to the increasing of contact area between gas phase and hydrate particles. The CO2 split fraction and separation factor with AA addition reached up to 70.3% and 42.8%, respectively.

  19. Impact of CO{sub 2} hydrates on ocean carbon dioxide deposition options

    Energy Technology Data Exchange (ETDEWEB)

    Lund, P C

    1995-04-01

    The objective of the research project described in this report was to contribute to the research on greenhouse gases and the global environment. The focus is on the concept of storing large amounts of CO{sub 2} in the ocean. The project was divided into three subtasks: (1) a comprehensive study of the thermodynamic, physical and chemical properties of the seawater/CO{sub 2}/hydrate system, (2) establishment of a micro-scale kinetic model for CO{sub 2} hydrate formation and stability, based on (1), and (3) establishment of macro-scale models for various ocean deposition options based on (2). A database of selected thermodynamic functions has been set up. A large database of oceanic data has also been made; for any given coordinates at sea a computer program provides the temperature, salinity and oxygen profiles from the sea surface to the sea floor. The kinetic model predicts the formation and pseudo-stability of a very thin hydrate film which acts as an inhibitor for diffusion of CO{sub 2} into the sea water. The model predicts that the hydrate film reduces the overall flux from a liquid CO{sub 2} source with about 90%. Thermodynamically, pure CO{sub 2} in contact with water might form hydrates at depths below about 400 m, which would indicate that hydrate formation could play a role for all ocean CO{sub 2} deposition options. However, this study shows that other mechanisms significantly reduce the role of hydrate formation. It is finally concluded that although more modelling and experimental work is required within this field of research, the hydrate film may play an important role for all options except from shallow water injection. 86 refs., 32 figs., 16 tabs.

  20. Effects of CO2 hydrate on deep-sea foraminiferal assemblages

    International Nuclear Information System (INIS)

    Ricketts, E. R.; Kennett, J. P.; Hill, T. M.; Barry, J. P.

    2005-01-01

    This study, conducted with the Monterey Bay Aquarium Research Institute (MBARI), is the first to investigate potential effects of carbon dioxide (CO2) hydrates on benthic microfossils, specifically oraminifera. The experiment was conducted in September 2003 aboard the R/V Western Flier using the ROV Tiburon. Experimental (CO2 exposed) and control cores were collected at 3600m and stained to distinguish live (stained) from dead (unstained) individuals. Foraminifera are ideal for these investigations because of differing test composition (calcareous and agglutinated) and thickness, and diverse epifaunal and infaunal depth preferences. The effects of the CO2 on assemblages have been tracked both vertically (10cm depth) and horizontally, and between live and dead individuals. Increased mortality and dissolution of calcareous forms resulted from exposure to CO2 hydrate. Preliminary results suggest several major effects on surface sediment assemblages: 1) total number of foraminifera in a sample decreases; 2) foraminiferal diversity decreases in both stained and unstained specimens. The number of planktonic and hyaline calcareous tests declines greatly, with milliolids being more resistant to dissolution when stained; and 3) percentage of stained (live) forms is higher. Down-core trends (up to 10cm) indicate: 1) percent agglutinated forms decline and calcareous forms increasingly dominate; 2) agglutinated diversity decreases with depth; and 3) assemblages become increasingly similar with depth to those in control cores not subjected to CO2 hydrate. These results imply almost complete initial mortality and dissolution upon CO2 hydrate emplacement in the corrals. (Author)

  1. Study of hydrogen-molecule guests in type II clathrate hydrates using a force-matched potential model parameterised from ab initio molecular dynamics

    Science.gov (United States)

    Burnham, Christian J.; Futera, Zdenek; English, Niall J.

    2018-03-01

    The force-matching method has been applied to parameterise an empirical potential model for water-water and water-hydrogen intermolecular interactions for use in clathrate-hydrate simulations containing hydrogen guest molecules. The underlying reference simulations constituted ab initio molecular dynamics (AIMD) of clathrate hydrates with various occupations of hydrogen-molecule guests. It is shown that the resultant model is able to reproduce AIMD-derived free-energy curves for the movement of a tagged hydrogen molecule between the water cages that make up the clathrate, thus giving us confidence in the model. Furthermore, with the aid of an umbrella-sampling algorithm, we calculate barrier heights for the force-matched model, yielding the free-energy barrier for a tagged molecule to move between cages. The barrier heights are reasonably large, being on the order of 30 kJ/mol, and are consistent with our previous studies with empirical models [C. J. Burnham and N. J. English, J. Phys. Chem. C 120, 16561 (2016) and C. J. Burnham et al., Phys. Chem. Chem. Phys. 19, 717 (2017)]. Our results are in opposition to the literature, which claims that this system may have very low barrier heights. We also compare results to that using the more ad hoc empirical model of Alavi et al. [J. Chem. Phys. 123, 024507 (2005)] and find that this model does very well when judged against the force-matched and ab initio simulation data.

  2. A Second Glass Transition in Pressure Collapsed Type II Clathrate Hydrates.

    Science.gov (United States)

    Andersson, Ove; Häussermann, Ulrich

    2018-04-19

    Type II clathrate hydrates (CHs) M·17 H 2 O, with M = tetrahydrofuran (THF) or 1,3-dioxolane, are known to collapse, or amorphize, on pressurization to ∼1.3 GPa in the temperature range 77-140 K. On heating at 1 GPa, these pressure-amorphized CH states show a weak, stretched sigmoid-shaped, heat-capacity increase because of a glass transition. Here we use thermal conductivity and heat capacity measurements to show that also type II CH with M = cyclobutanone (CB) collapses on isothermal pressurization and undergoes a similar, weak, glass transition upon heating at 1 GPa. Furthermore, we reveal for both THF CH and CB CH a second, much more pronounced, glass transition at temperatures above the thermally weak glass transition on heating in the 0.2-0.7 GPa range. This result suggests the general occurrence of two glass transitions in water-rich (94 mol %) pressure-collapsed CHs. Because of a large increase in dielectric permittivity concurrently as the weak heat capacity increase, the first glass transition must be due to kinetic unfreezing of water molecules. The thermal features of the second glass transition, measured on isobaric temperature cycling, are typical of a glass-liquid-glass transition, which suggests that pressure-amorphized CHs transform reversibly to liquids.

  3. Replacement of CH4 in the hydrate by use of liquid CO2

    International Nuclear Information System (INIS)

    Ota, Masaki; Morohashi, Kenji; Abe, Yuki; Watanabe, Masaru; Smith, Richard Lee Jr.; Inomata, Hiroshi

    2005-01-01

    The dynamics of CH 4 replacement in the CH 4 hydrate with saturated liquid CO 2 at 273.2 K was measured with a high pressure optical cell. The results showed that CH 4 in the hydrate gradually moved to the liquid CO 2 phase while CO 2 in the liquid phase penetrated into the hydrate from the quantitative analysis. The decomposing process of the CH 4 hydrate during the replacement was analyzed with in situ Raman spectroscopy, which allowed us to distinguish the cage structure of the CH 4 hydrate and discuss the microscopic view of the replacement in the hydrate. It was found that the decomposition of the medium cage (M-cage) in the CH 4 hydrate proceeded faster than that of the small cage (S-cage). The observed rate difference could be related to the stability of the S-cage in the CH 4 hydrate or the re-formation tendency of CH 4 and water molecules in the S-cage after decomposing the hydrate structure, whereas the guest molecule exchange of CH 4 with CO 2 could occur in the M-cage. Based on the experimental data, we developed a kinetic model for calculation of the CH 4 remaining in the hydrate considering the decomposition rate difference between the M-cage and S-cage in the CH 4 hydrate. The results indicate that the driving force could be the fugacity difference between the fluid phase and the hydrate phase for the replacement process

  4. Numerical Simulations for Enhanced Methane Recovery from Gas Hydrate Accumulations by Utilizing CO2 Sequestration

    Science.gov (United States)

    Sridhara, Prathyusha

    In 2013, the International Energy Outlook (EIA, 2013) projected that global energy demand will grow by 56% between 2010 and 2040. Despite strong growth in renewable energy supplies, much of this growth is expected to be met by fossil fuels. Concerns ranging from greenhouse gas emissions and energy security are spawning new interests for other sources of energy including renewable and unconventional fossil fuel such as shale gas and oil as well as gas hydrates. The production methods as well as long-term reservoir behavior of gas hydrate deposits have been under extensive investigation. Reservoir simulators can be used to predict the production potentials of hydrate formations and to determine which technique results in enhanced gas recovery. In this work, a new simulation tool, Mix3HydrateResSim (Mix3HRS), which accounts for complex thermodynamics of multi-component hydrate phase comprised of varying hydrate solid crystal structure, is used to perform the CO2-assisted production technique simulations from CH4 hydrate accumulations. The simulator is one among very few reservoir simulators which can simulate the process of CH4 substitution by CO2 (and N2 ) in the hydrate lattice. Natural gas hydrate deposits around the globe are categorized into three different classes based on the characteristics of the geological sediments present in contact with the hydrate bearing deposits. Amongst these, the Class 2 hydrate accumulations predominantly confirmed in the permafrost and along seashore, are characterized by a mobile aqueous phase underneath a hydrate bearing sediment. The exploitation of such gas hydrate deposits results in release of large amounts of water due to the presence of permeable water-saturated sediments encompassing the hydrate deposits, thus lowering the produced gas rates. In this study, a suite of numerical simulation scenarios with varied complexity are considered which aimed at understanding the underlying changes in physical, thermodynamic and

  5. Thermo physical and flow properties of CO{sub 2} hydrate slurry - Scientific paper

    Energy Technology Data Exchange (ETDEWEB)

    Sari, O.; Hu, J.; Eicher, S.; Egolf, P. W. [Institute of Thermal Engineering, University of Applied Sciences of Western Switzerland, Yverdon-les-Bains (Switzerland); Homsy, P. [Nestec, Vevey (Switzerland)

    2008-07-01

    The apparent viscosity and flow regime of CO{sub 2} hydrate slurry were investigated with a XL7-100 on-line resonant viscometer. Possible reasons for the viscosity changes before and after the nucleation of hydrates are discussed. In addition, super saturation of the CO{sub 2} solution under certain pressure and temperature conditions as well as its density and apparent viscosity were examined. The hydrate's solid fraction and the dissociation enthalpy were evaluated by an on-line Micro DSC system. Real-time coupled multi-electrode array sensor (CMAS) probes were applied to measure the maximal localized corrosion rate of three different materials subjected to CO{sub 2} hydrate slurry and saturated CO{sub 2} solution in the temperature range of 1 to 18 {sup o}C and pressure range of 25 to 30 bar. The density of CO{sub 2} hydrate slurry was also experimentally investigated and the relation between the density and the solid fraction has been established. (author)

  6. Hydrate-based technology for CO2 capture from fossil fuel power plants

    International Nuclear Information System (INIS)

    Yang, Mingjun; Song, Yongchen; Jiang, Lanlan; Zhao, Yuechao; Ruan, Xuke; Zhang, Yi; Wang, Shanrong

    2014-01-01

    Graphical abstract: Application of hydrate based technology on carbon dioxide capture and storage (CCS). - Highlights: • Hydrate-based CO 2 –N 2 separation data was obtained for flow in porous media. • Tetrahydrofuran and sodium dodecyl sulphate are used as additives simultaneously. • Solution movement rarely occurs when residual solution saturations are low. • Bothe of pressure and temperature have remarkable impacts on gas compositions. • A suitable operation parameter choice is proposed for hydrate-based CO 2 capture. - Abstract: Hydrate-based CO 2 capture is a promising technology. To obtain fundamental data for a flowing system, we measured the distribution of pore solution to analyse hydrate formation/dissociation and gas separation properties. An orthogonal experiment was carried out to investigate the effects of glass beads, flow rates, pressures and temperatures on it. Magnetic resonance imaging (MRI) images were obtained using a spin echo multi-slice pulse sequence. Hydrate saturations were calculated quantitatively using an MRI mean intensity. The results show that hydrate blockages were frequently present. During the hydrate formation and dissociation process, the movement of the solution occurred in cycles. However, the solution movement rarely occurred for residual solution saturations obtained with a high backpressure. The solution concentrate phenomenon occurred mostly in BZ-04. The highest hydrate saturation was 30.2%, and the lowest was 0.70%. Unlike that in BZ-01, there was no stability present in BZ-02 and BZ-04. The different CO 2 concentrations for the three processes of each cycle verified hydrate formation during the gas flow process. The highest CO 2 concentration was 38.8%, and the lowest one was 11.4%. To obtain high hydrate saturation and good separation effects, the values of 5.00 MPa, 1.0 ml min −1 and 280.00 K were chosen. For the gas flow process, only the pressure had a significant impact on gas composition, and all

  7. The CO{sub 2} hydrate slurry; Le coulis de glace

    Energy Technology Data Exchange (ETDEWEB)

    Sari, O.; Hu, J.; Eicher, S.; Brun, F. [Institute of Thermal Engineering, University of Applied Sciences of Western Switzerland, Yverdon-les-Bains (Switzerland); Sari, O.; Hu, J. [Clean Cooling Solutions, spin off of University of Applied Sciences of Western Switzerland, Yverdon-les-Bains (Switzerland); Homsy, P. [Nestec Ltd, Vevey (Switzerland); Logel, J.-C. [Axima Refrigeration, Bischheim (France)

    2007-12-15

    A new, very promising refrigerant was developed, which could be used in industrial processes as well as air conditioners: the CO{sub 2} hydrate slurry. Replacing hydrochlorofluorocarbon HCFC refrigerants has a high priority, due to the strong negative environmental impact of these fluids. New refrigerants have to be environment friendly, non-inflammable, cheap and made of natural materials. CO{sub 2} hydrate slurries and/or a mixture of ice slurry and CO{sub 2} hydrate slurry meet these requirements. The University of Applied Sciences of Western Switzerland in Yverdon, together with industrial partners, investigated the properties of such slurries. The slurries were created using the Coldeco process: the refrigerating fluid is directly injected into the liquid brine. The evaporation of the refrigerating fluid cools the liquid down to its freezing point and homogeneously distributed small crystals appear in the liquid. A test rig was built to measure the physical and chemical properties of the slurries obtained in this way. CO{sub 2} hydrate slurries have a higher energy storage capacitance (500 kJ/kg) than ice slurries (333 kJ/kg). The production of CO{sub 2} hydrate slurries in large quantities in a continuous process was demonstrated. The solid particle concentration was 10%, the pressure amounted to 30 bar and the temperature 2 to 4 {sup o}C. Such slurries can be pumped and circulated in pipe networks. Stainless steel is the appropriate material for such networks. However, the main advantage of the new refrigerant will be, according to the authors, a reduced energy consumption compared to traditional refrigerating cycles: the difference between the temperature required by the user and the refrigerant temperature is reduced, thanks to the use of the latent heat in the new process.

  8. Phase Behaviour of Methane Hydrate Under Conditions Relevant to Titan's Interior

    Science.gov (United States)

    Sclater, G.; Fortes, A. D.; Crawford, I. A.

    2018-06-01

    The high-pressure behaviour Clathrate hydrates, thought to be abundant in the outer solar system, underpins planetary modelling efforts of the interior of Titan, where clathrates are hypothesised to be the source of the dense N2, CH4 atmosphere.

  9. Kinetics of CO2 and methane hydrate formation : an experimental analysis in the bulk phase

    NARCIS (Netherlands)

    He, Y.; Rudolph, E.S.J.; Zitha, P.L.J.; Golombok, M.

    2011-01-01

    Gas resources captured in the form of gas hydrates are by an order of magnitude larger than the resources available from conventional resources. In order to keep the CO2CO2 footprint in the world as small as possible, the idea is to produce methane hydrates and sequestrate CO2CO2 into hydrates in

  10. Isostructural and cage-specific replacement occurring in sII hydrate with external CO2/N2 gas and its implications for natural gas production and CO2 storage

    International Nuclear Information System (INIS)

    Seo, Young-ju; Park, Seongmin; Kang, Hyery; Ahn, Yun-Ho; Lim, Dongwook; Kim, Se-Joon; Lee, Jaehyoung; Lee, Joo Yong; Ahn, Taewoong; Seo, Yongwon; Lee, Huen

    2016-01-01

    Highlights: • The structural sustainability of sII hydrate is demonstrated during the replacement. • The experimental evidence of isostructural replacement is revealed. • The cage-specific replacement in sII hydrates allows long-term CO 2 storage. • The compositions and extent of replacement are cross-checked by GC and NMR analyses. - Abstract: A replacement technique has been regarded as a promising strategy for both CH 4 exploitation from gas hydrates and CO 2 sequestration into deep-ocean reservoirs. Most research has been focused on replacement reactions that occur in sI hydrates due to their prevalence in natural gas hydrates. However, sII hydrates in nature have been also discovered in some regions, and the replacement mechanism in sII hydrates significantly differs from that in sI hydrates. In this study, we have intensively investigated the replacement reaction of sII (C 3 H 8 + CH 4 ) hydrate by externally injecting CO 2 /N 2 (50:50) gas mixture with a primary focus on powder X-ray diffraction, Raman spectroscopy, NMR spectroscopy, and gas chromatography analyses. In particular, it was firstly confirmed that there was no structural transformation during the replacement of C 3 H 8 + CH 4 hydrate with CO 2 /N 2 gas injection, indicating that sII hydrate decomposition followed by sI hydrate formation did not occur. Furthermore, the cage-specific replacement pattern of the C 3 H 8 + CH 4 hydrate revealed that CH 4 replacement with N 2 in the small cages of sII was more significant than C 3 H 8 replacement with CO 2 in the large cages of sII. The total extent of the replacement for the C 3 H 8 + CH 4 hydrate was cross-checked by NMR and GC analyses and found to be approximately 54%. Compared to the replacement for CH 4 hydrate with CO 2 /N 2 gas, the lower extent of the replacement for the C 3 H 8 + CH 4 hydrate with CO 2 /N 2 gas was attributable to the persistent presence of C 3 H 8 in the large cages and the lower content of N 2 in the feed gas. The

  11. Methane Production from Gas Hydrate Deposits through Injection of Supercritical CO2

    Directory of Open Access Journals (Sweden)

    Matthias Haeckel

    2012-06-01

    Full Text Available The recovery of natural gas from CH4-hydrate deposits in sub-marine and sub-permafrost environments through injection of CO2 is considered a suitable strategy towards emission-neutral energy production. This study shows that the injection of hot, supercritical CO2 is particularly promising. The addition of heat triggers the dissociation of CH4-hydrate while the CO2, once thermally equilibrated, reacts with the pore water and is retained in the reservoir as immobile CO2-hydrate. Furthermore, optimal reservoir conditions of pressure and temperature are constrained. Experiments were conducted in a high-pressure flow-through reactor at different sediment temperatures (2 °C, 8 °C, 10 °C and hydrostatic pressures (8 MPa, 13 MPa. The efficiency of both, CH4 production and CO2 retention is best at 8 °C, 13 MPa. Here, both CO2- and CH4-hydrate as well as mixed hydrates can form. At 2 °C, the production process was less effective due to congestion of transport pathways through the sediment by rapidly forming CO2-hydrate. In contrast, at 10 °C CH4 production suffered from local increases in permeability and fast breakthrough of the injection fluid, thereby confining the accessibility to the CH4 pool to only the most prominent fluid channels. Mass and volume balancing of the collected gas and fluid stream identified gas mobilization as equally important process parameter in addition to the rates of methane hydrate dissociation and hydrate conversion. Thus, the combination of heat supply and CO2 injection in one supercritical phase helps to overcome the mass transfer limitations usually observed in experiments with cold liquid or gaseous CO2.

  12. Precise structural analysis of methane hydrate by neutron diffraction

    International Nuclear Information System (INIS)

    Igawa, Naoki; Hoshikawa, Akinori; Ishii, Yoshinobu

    2006-01-01

    Methane hydrate has attracted great interest as an energy resource to replace natural gas since this material is deposited in the seafloor and the deposits are estimated to exceed those of natural gas. Understanding the physical proprieties, such as the temperature dependence of the crystal structure, helps to specify the optimum environmental temperature and pressure during drilling, transport, and storage of methane hydrate. Clathrate hydrates consisted of encaging atomic and/or molecular species as a guest and host water formed by a hydrogen bonding. Although many studies on the clathrate hydrate including methane hydrate were reported, no detailed crystallographic property has yet been cleared. We focused on the motion of methane in the clathrate hydrate by the neutron diffraction. The crystal structure of the methane hydrate was analyzed by the applying the combination of the Rietveld refinement and the maximum entropy method (MEM) to neutron powder diffraction. Temperature dependence of the scattering-length density distribution maps revealed that the motion of methane molecules differs between the shapes of dodecahedron and tetrakaidecahedron. (author)

  13. Crystallization of tetra-n-butyl ammonium bromide clathrate hydrate slurry and the related heat transfer characteristics

    International Nuclear Information System (INIS)

    Shi, X.J.; Zhang, P.

    2014-01-01

    Highlights: • Crystallization characteristics of TBAB CHS under different thermal conditions were clarified. • Overall heat transfer coefficients before and during the crystallization were obtained. • The crystallization characteristics of TBAB CHS mainly depend on the status of supercooled solution. • Dropping of TBAB CHS can accelerate the supercooling release and crystallization. - Abstract: Tetra-n-butyl ammonium bromide (TBAB) clathrate hydrate slurry (CHS) is a promising phase change material slurry for cold storage and transport in air-conditioning system. This slurry can be generated from the supercooled TBAB aqueous solution. In the present study, TBAB CHS was generated under different thermal conditions, i.e. different initial mass concentrations of TBAB aqueous solution and different supercooling degrees. The crystallization of TBAB CHS and the overall heat transfer coefficient under different thermal conditions were clarified. It was concluded that the crystallization characteristics of TBAB hydrate crystals mainly depended upon the thermal condition of the supercooled TBAB aqueous solution. In addition, the dropping of pre-produced TBAB CHS into supercooled TBAB aqueous solution could immediately induce the crystallization of TBAB hydrate crystals, and the initial type of TBAB hydrate crystals was only related to the status of the supercooled TBAB aqueous solution regardless of the type of the dropped TBAB CHS. Furthermore, the overall heat transfer coefficients before crystallization and during crystallization were also measured. It was found that more hydrate crystals would adhere to the vessel wall at larger supercooling degree and higher mass concentration of aqueous solution, which would deteriorate the heat transfer significantly. Moreover, images of TBAB hydrate crystals under different thermal conditions were recorded in order to help clarifying the crystallization characteristics

  14. Thermodynamic model for predicting equilibrium conditions of clathrate hydrates of noble gases + light hydrocarbons: Combination of Van der Waals–Platteeuw model and sPC-SAFT EoS

    International Nuclear Information System (INIS)

    Abolala, Mostafa; Varaminian, Farshad

    2015-01-01

    Highlights: • Applying sPC-SAFT for phase equilibrium calculations. • Determining Kihara potential parameters for hydrate formers. • Successful usage of the model for systems with hydrate azeotropes. - Abstract: In this communication, equilibrium conditions of clathrate hydrates containing mixtures of noble gases (Argon, Krypton and Xenon) and light hydrocarbons (C 1 –C 3 ), which form structure I and II, are modeled. The thermodynamic model is based on the solid solution theory of Van der Waals–Platteeuw combined with the simplified Perturbed-Chain Statistical Association Fluid Theory equation of state (sPC-SAFT EoS). In dispersion term of sPC-SAFT EoS, the temperature dependent binary interaction parameters (k ij ) are adjusted; taking advantage of the well described (vapor + liquid) phase equilibria. Furthermore, the Kihara potential parameters are optimized based on the P–T data of pure hydrate former. Subsequently, these obtained parameters are used to predict the binary gas hydrate dissociation conditions. The equilibrium conditions of the binary gas hydrates predicted by this model agree well with experimental data (overall AAD P ∼ 2.17)

  15. Molecular storage of ozone in a clathrate hydrate: an attempt at preserving ozone at high concentrations.

    Directory of Open Access Journals (Sweden)

    Takahiro Nakajima

    Full Text Available This paper reports an experimental study of the formation of a mixed O(3+ O(2+ CO(2 hydrate and its frozen storage under atmospheric pressure, which aimed to establish a hydrate-based technology for preserving ozone (O(3, a chemically unstable substance, for various industrial, medical and consumer uses. By improving the experimental technique that we recently devised for forming an O(3+ O(2+ CO(2 hydrate, we succeeded in significantly increasing the fraction of ozone contained in the hydrate. For a hydrate formed at a system pressure of 3.0 MPa, the mass fraction of ozone was initially about 0.9%; and even after a 20-day storage at -25°C and atmospheric pressure, it was still about 0.6%. These results support the prospect of establishing an economical, safe, and easy-to-handle ozone-preservation technology of practical use.

  16. Morphology studies on gas hydrates interacting with silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Beltran, J.; Servio, P. [McGill Univ., Montreal, PQ (Canada). Dept. of Chemical Engineering

    2008-07-01

    Clathrate hydrates or gas hydrates are non-stoichiometric, crystalline compounds that form when small molecules come in contact with water at certain temperatures and pressures. Natural gas hydrates are found in the ocean bottom and in permafrost regions. It is thought that the amount of energy stored in natural hydrates is at least twice that of all other fossil fuels combined. In addition, trapping carbon dioxide as a hydrate in the bottom of the ocean has been suggested as an alternative means of reducing atmospheric carbon dioxide levels. Naturally occurring clathrates are found in close interaction with fine grained particles of very small mean pore diameters. Even though an increasing amount of hydrate equilibrium data for small diameter porous media has become available, the morphological behavior of hydrates subject to such conditions is yet to be explored. This paper presented a study that visually examined hydrate formation and decomposition of gas hydrates while interacting with fine grains of silica gel. The study showed still frames from high-resolution video recordings for hydrate formation and decomposition. The paper discussed the experiment including the apparatus as well as the results of hydrate formation and hydrate dissociation. This study enabled for the first time to observe clathrate morphology while hydrates interacted closely with fine grain particles with small mean pore diameters. 9 refs., 8 figs.

  17. Phase equilibrium condition measurements in nitrogen and air clathrate hydrate forming systems at temperatures below freezing point of water

    International Nuclear Information System (INIS)

    Yasuda, Keita; Oto, Yuya; Shen, Renkai; Uchida, Tsutomu; Ohmura, Ryo

    2013-01-01

    Highlights: • Phase equilibrium conditions in the nitrogen and modelled air hydrate forming systems are measured. • Measurements are conducted at temperatures below the freezing point of water. • Results have relevance to the air hydrate formation in the ice sheets. • Measured data are quantitatively compared with the previously reported values. • Range of the equilibrium measurements was from (242 to 268) K. -- Abstract: Contained in this paper are the three phase equilibrium conditions of the (ice + clathrate hydrate + guest-rich) vapour in the (nitrogen + water) and the modelled (air + water) systems at temperatures below the freezing point of water. The precise determination of the equilibrium conditions in those systems are of importance for the analysis of the past climate change using the cored samples from the ice sheets at Antarctica and Greenland because the air hydrates keep the ancient climate signals. The mole ratio of the modelled air composed of nitrogen and oxygen is 0.790:0.210. The equilibrium conditions were measured by the batch, isochoric procedure. The temperature range of the measurements in the nitrogen hydrate forming system is (244.05 < T < 266.55) K and the corresponding equilibrium pressure range is (7.151 < p < 12.613) MPa. The temperature range of the measurements in the modelled air hydrate forming system is (242.55 < T < 267.85) K, and the corresponding equilibrium pressure range is (6.294 < p < 12.144) MPa. The data obtained quantitatively compared with the previously reported data

  18. A Feasibility Study on Hydrate-Based Technology for Transporting CO2 from Industrial to Agricultural Areas

    Directory of Open Access Journals (Sweden)

    Seiji Matsuo

    2017-05-01

    Full Text Available Climate change caused by global warming has become a serious issue in recent years. The main purpose of this study was to evaluate the effectiveness of the above system to quantitatively supply CO2 or CO2 hydrate from industrial to agricultural areas. In this analysis, several transportation methods, namely, truck, hydrate tank lorry, and pipeline, were considered. According to this analysis, the total CO2 supply costs including transportation ranged from 15 to 25 yen/kg-CO2 when the transportation distance was 50 km or less. The cost of the hydrate-based method increased with the transport distance in contrast to the liquefied CO2 approach. However, the technology of supplying CO2 hydrate had merit by using a local cooling technique for cooling specific parts of agricultural products.

  19. Clathrate hydrate dissociation conditions of refrigerants R404A, R406A, R408A and R427A: Experimental measurements and thermodynamic modeling

    International Nuclear Information System (INIS)

    Hashemi, Hamed; Babaee, Saeedeh; Mohammadi, Amir H.; Naidoo, Paramespri; Ramjugernath, Deresh

    2015-01-01

    Highlights: • The application of refrigerant hydrates in cold storage systems is investigated. • Hydrate dissociation conditions of various refrigerants have been measured. • A correlative thermodynamic model was applied to the data. • Enthalpy of dissociation for the refrigerants studied calculated. • Experimental measurements performed over a wide range of pressures. - Abstract: Clathrate hydrate dissociation conditions were measured for four “alternative” refrigerants, viz. R404A, R406A, R408A and R427A. The experimental measurements were performed within the pressure range of (0.079 to 9.995) MPa and temperatures ranging from (272.7 to 288.7) K. An isochoric pressure-search method was used to perform the measurements. A thermodynamic model based on the van der Waals–Platteeuw (vdW–P) model was applied for the prediction of the dissociation conditions which were compared to the experimental measurements. The fluid phase was modeled using the MHV2 G E -EoS mixing rule along with the UNIFAC (original) activity model. The van der Waals–Platteeuw (vdW–P) model was used for the modeling of the hydrate phase. There was reasonable agreement between the experimental and predicted values

  20. Clathrates - An Exploration of the Chemistry of Caged Compounds

    Indian Academy of Sciences (India)

    also found on the icy moons of our solar system, at Saturn and .... This mineral loses water rapidly on heating and seemed ... The prototype of clathrate-I structure for gas hydrate has a .... Useful for studies of air pollution, process control and.

  1. Phase equilibrium modeling of gas hydrate systems for CO2 capture

    DEFF Research Database (Denmark)

    Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens

    2012-01-01

    to form from vapor phases with initial mole fractions of CO2 at or above 0.15.The two models are validated against mixed hydrate equilibrium data found in literature. Both dissociation pressures and hydrate compositions are considered in the validation process.With the fitted parameters, Model I predicts...

  2. Phase equilibrium conditions of semi-calthrate hydrates of (tetra-n-butyl ammonium chloride + carbon dioxide)

    International Nuclear Information System (INIS)

    Sun, Zhi-Gao; Jiao, Li-Jun; Zhao, Zhi-Gui; Wang, Gong-Liang; Huang, Hai-Feng

    2014-01-01

    Highlights: • Carbon dioxide hydrate stability zone was enlarged with the help of TBAC. • Carbon dioxide uptake into TBAC semi-clathrate hydrates is confirmed. • Equilibrium pressure of hydrate decreased with the increase of TBAC mass concentration. • The addition of TBAC reduces the formation pressures of carbon dioxide hydrate by 2.5 MPa. - Abstract: In the present work, hydrate equilibrium conditions for (tetra-n-butyl ammonium chloride (TBAC) + carbon dioxide + water) mixtures were investigated. Tetra-n-butyl ammonium chloride was reported to form a semi-clathrate hydrate. The experiments were carried out within the TBAC mass fraction range of (0.05 to 0.3). The experimental results showed that the presence of TBAC decreased the formation pressure of carbon dioxide double hydrate within the experimental temperature range. Moreover, pressure reduction was dependent on the TBAC concentration

  3. An effect of surface properties on detachment of adhered solid to cooling surface for formation of clathrate hydrate slurry

    Science.gov (United States)

    Daitoku, Tadafumi; Utaka, Yoshio

    In air-conditioning systems, it is desirable that the liquid-solid phase change temperature of a cool energy storage material is approximately 10 °C from the perspective of improving coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize large heat capacity of working fluids. Since the solid that adheres to the heat transfer surface forms a thermal resistance layer and remarkably reduces the rate of cold storage, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removing the solid phase from the heat transfer surface was studied. Tetra-n-butylammonium Bromide (TBAB) clathrate hydrate was used as a cold storage material. The effect of the heat transfer surface properties on the scraping force for detachment of adhered solid of TBAB hydrate to the heat transfer surface was examined experimentally.

  4. How Sodium Chloride Salt Inhibits the Formation of CO2 Gas Hydrates.

    Science.gov (United States)

    Holzammer, Christine; Finckenstein, Agnes; Will, Stefan; Braeuer, Andreas S

    2016-03-10

    We present an experimental Raman study on how the addition of sodium chloride to CO2-hydrate-forming systems inhibits the hydrate formation thermodynamically. For this purpose, the molar enthalpy of reaction and the molar entropy of reaction for the reaction of weakly hydrogen-bonded water molecules to strongly hydrogen bonded water molecules are determined for different salinities from the Raman spectrum of the water-stretching vibration. Simultaneously, the influence of the salinity on the solubility of CO2 in the liquid water-rich phase right before the start of hydrate formation is analyzed. The results demonstrate that various mechanisms contribute to the inhibition of gas hydrate formation. For the highest salt concentration of 20 wt % investigated, the temperature of gas hydrate formation is lowered by 12 K. For this concentration the molar enthalpy and entropy of reaction become smaller by 50 and 20%, respectively. Concurrently, the solubility of carbon dioxide is reduced by 70%. These results are compared with data in literature for systems of sodium chloride in water (without carbon dioxide).

  5. Study on Characteristic of Self-preservation Effect of CO2 Hydrate according to Temperature, Particle Diameter and Shape

    International Nuclear Information System (INIS)

    Kim, Yeon-Soo; Kang, Seong-Pil; Park, So-Jin

    2013-01-01

    Gas hydrate studies are attracting attention of many researchers as an innovative, economic and environmentally friendly technology when it is applied to CO 2 capture, transport, and storage. In this study, we investigated whether CO 2 hydrate shows the self-preservation effect or not, that is the key property for developing a novel CO 2 transport/storage method. Especially the degree of self-preservation effect for CO 2 hydrate was studied according to the particle size of CO 2 hydrate samples. We prepared three kinds of CO 2 hydrate samples varying their particle diameter as millimeter, micron and nano size and measured their change of weight at -15 - -30 .deg. C under atmospheric pressure during 3 weeks. According to our experimental result, the lower temperature, larger particle size, and compact structure for higher density are the better conditions for obtaining self-preservation effect

  6. Precipitation of hydrated Mg carbonate with the aid of carbonic anhydrase for CO2 sequestration

    Science.gov (United States)

    Power, I. M.; Harrison, A. L.; Dipple, G. M.

    2011-12-01

    Strategies for sequestering CO2 directly from the atmosphere are likely required to achieve the desired reduction in CO2 concentration and avoid the most damaging effects of climate change [1]. Numerous studies have demonstrated the accelerated precipitation of calcium carbonate minerals with the aid of carbonic anhydrase (CA) as a means of sequestering CO2 in solid carbonate form; however, no study has examined precipitation of magnesium carbonate minerals using CA. Precipitation of magnesite (MgCO3) is kinetically inhibited [2]; therefore, Mg2+ must be precipitated as hydrated carbonate minerals. In laboratory experiments, the uptake of atmospheric CO2 into brine solutions (0.1 M Mg) was rate-limiting for the precipitation of dypingite [Mg5(CO3)4(OH)2-5H2O] with initial precipitation requiring 15 days [3]. It was also found that dypingite precipitation outpaced the uptake of CO2 gas into solution. CO2 uptake is limited by the hydration of CO2 to form carbonate ions [4]. Carbonic anhydrase (CA) enzymes are among the fastest known in nature and are able to catalyze the hydration of CO2, i.e., converting CO2(aq) to CO32- and HCO3- [5]. CA plays an important role in the carbon concentrating mechanism of photoautotrophic, chemoautotrophic, and heterotrophic prokaryotes and is involved in pH homeostasis, facilitated diffusion of CO2, ion transport, and the interconversion of CO2 and HCO3- [6]. Introducing CA into buffered Mg-rich solutions should allow for more rapid precipitation of hydrated magnesium carbonate minerals. Batch experiments were conducted using 125 mL flasks containing 100 mL of Millipore deionized water with 0.2 M of MgCl2-6H2O. To buffer pH, 1.0 g of pulverized brucite [Mg(OH)2] or 1.0 g of NaOH was added to the systems, which were amended with Bovine carbonic anhydrase (BCA) (Sigma-Aldrich). Solutions were stirred continuously and kept at room temperature (~22°C) with laboratory air introduced by bubbling. Temperature and pH were measured routinely

  7. Carbon dioxide storage in marine sediments - dissolution, transport and hydrate formation kinetics from high-pressure experiments

    Science.gov (United States)

    Bigalke, N. K.; Savy, J. P.; Pansegrau, M.; Aloisi, G.; Kossel, E.; Haeckel, M.

    2009-12-01

    By satisfying thermodynamic framework conditions for CO2 hydrate formation, pressures and temperatures of the deep marine environment are unique assets for sequestering CO2 in clathrates below the seabed. However, feasibility and safety of this storage option require an accurate knowledge of the rate constants governing the speed of physicochemical reactions following the injection of the liquefied gas into the sediments. High-pressure experiments designed to simulate the deep marine environment open the possibility to obtain the required parameters for a wide range of oceanic conditions. In an effort to constrain mass transfer coefficients and transport rates of CO2 in(to) the pore water of marine sediments first experiments were targeted at quantifying the rate of CO2 uptake by de-ionized water and seawater across a two-phase interface. The nature of the interface was controlled by selecting p and T to conditions within and outside the hydrate stability field (HSF) while considering both liquid and gaseous CO2. Concentration increase and hydrate growth were monitored by Raman spectroscopy. The experiments revealed anomalously fast transport rates of dissolved CO2 at conditions both inside and outside the HSF. While future experiments will further elucidate kinetics of CO2 transport and hydrate formation, these first results could have major significance to safety-related issues in the discussion of carbon storage in the marine environment.

  8. Hydrogen storage in clathrate hydrates: Current state of the art and future directions

    International Nuclear Information System (INIS)

    Veluswamy, Hari Prakash; Kumar, Rajnish; Linga, Praveen

    2014-01-01

    Hydrogen is looked upon as the next generation clean energy carrier, search for an efficient material and method for storing hydrogen has been pursued relentlessly. Improving hydrogen storage capacity to meet DOE targets has been challenging and research efforts are continuously put forth to achieve the set targets and to make hydrogen storage a commercially realizable process. This review comprehensively summarizes the state of the art experimental work conducted on the storage of hydrogen as hydrogen clathrates both at the molecular level and macroscopic level. It identifies future directions and challenges for this exciting area of research. Hydrogen storage capacities of different clathrate structures – sI, sII, sH, sVI and semi clathrates have been compiled and presented. In addition, promising new approaches for increasing hydrogen storage capacity have been described. Future directions for achieving increased hydrogen storage and process scale up have been outlined. Despite few limitations in storing hydrogen in the form of clathrates, this domain receives prominent attention due to more environmental-friendly method of synthesis, easy recovery of molecular hydrogen with minimum energy requirement, and improved safety of the process

  9. Kinetics of the Formation and Dissociation of Gas Hydrates from CO2-CH4 Mixtures

    Directory of Open Access Journals (Sweden)

    Devinder Mahajan

    2012-07-01

    Full Text Available Sequestration of carbon dioxide (CO2 in the form of its hydrates in natural methane (CH4 hydrate reservoirs, via CO2/CH4 exchange, is an attractive pathway that also yields valuable CH4 gas as product. In this paper, we describe a macroscale experiment to form CO2 and CH4-CO2 hydrates, under seafloor-mimic conditions, in a vessel fitted with glass windows that provides visualization of hydrates throughout formation and dissociation processes. Time resolved pressure and temperature data as well as images of hydrates are presented. Quantitative gas conversions with pure CO2, calculated from gas chromatographic measurements yielded values that range from 23 – 59% that correspond to the extent of formed hydrates. In CH4-rich CH4-CO2 mixed gas systems, CH4 hydrates were found to form preferentially.

  10. Experimental hydrate formation and gas production scenarios based on CO{sub 2} sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, J.C.; Howard, J.J. [ConocoPhillips, Bartlesville, OK (United States). Reservoir Laboratories; Baldwin, B.A. [Green Country Petrophysics LLC, Dewey, OK (United States); Ersland, G.; Husebo, J.; Graue, A. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology

    2008-07-01

    Gas hydrate production strategies have focused on depressurization or thermal stimulation of the reservoir, which in turn leads to hydrate dissociation. In order to evaluate potential production scenarios, the recovery efficiency of the natural gas from hydrate must be known along with the corresponding amounts of produced water. This study focused on the exchange of carbon dioxide (CO{sub 2}) with the natural gas hydrate and the subsequent release of free methane (CH{sub 4}). Laboratory experiments that investigated the rates and mechanisms of hydrate formation in coarse-grained porous media have shown the significance of initial water saturation and salinity on forming methane hydrates. Many of the experiments were performed in a sample holder fitted with an MRI instrument for monitoring hydrate formation. Hydrate-saturated samples were subjected to different procedures to release methane. The rates and efficiency of the exchange process were reproducible over a series of initial conditions. The exchange process was rapid and efficient in that no free water was observed in the core with MRI measurements. Injection of CO{sub 2} into the whole-core hydrate-saturated pore system resulted in methane production at the outlet end. Permeability measurements on these hydrate saturated cores during hydrate formation decreased to low values, but enough for gas transport. The lower permeability values remained constant during the methane-carbon dioxide exchange process in the hydrate structure. 12 refs., 9 figs.

  11. Thermodynamics of a post combustion hydrate-based carbon dioxide capture process

    International Nuclear Information System (INIS)

    Ben Attouche Sfaxi, I.

    2011-07-01

    Hydrates selectivity towards carbon dioxide is offering a promising route for carbon dioxide removal from flue gases. Hydrate-based CO 2 capture process could substitute amine facilities widely implemented in gas treatment plants but suffering from oxidative degradation problems and high energy demand. In the framework of this thesis, we focus on phase equilibria that are involved in such process. Experimental dissociation conditions for clathrate hydrates of carbon dioxide and nitrogen, in the presence of some promoting molecules (Tetrahydrofuran, Tetrabutyl ammonium bromide and Tetrabutyl ammonium Fluoride ) are reported in the experimental section of this work. The data generated in this work along with literature data are compared to the model predictions. The developed model is based on the Cubic Plus Association (CPA) equation of state (EoS) for fluid phases combined to the van der Waals and Platteeuw's theory for the hydrate phase. (author)

  12. Stochastic Approach to Determine CO2 Hydrate Induction Time in Clay Mineral Suspensions

    Science.gov (United States)

    Lee, K.; Lee, S.; Lee, W.

    2008-12-01

    A large number of induction time data for carbon dioxide hydrate formation were obtained from a batch reactor consisting of four independent reaction cells. Using resistance temperature detector(RTD)s and a digital microscope, we successfully monitored the whole process of hydrate formation (i.e., nucleation and crystal growth) and detected the induction time. The experiments were carried out in kaolinite and montmorillonite suspensions at temperatures between 274 and 277 K and pressures ranging from 3.0 to 4.0 MPa. Each set of data was analyzed beforehand whether to be treated by stochastic manner or not. Geochemical factors potentially influencing the hydrate induction time under different experimental conditions were investigated by stochastic analyses. We observed that clay mineral type, pressure, and temperature significantly affect the stochastic behavior of the induction times for CO2 hydrate formation in this study. The hydrate formation kinetics along with stochastic analyses can provide basic understanding for CO2 hydrate storage in deep-sea sediment and geologic formation, securing its stability under the environments.

  13. Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria

    Science.gov (United States)

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2006-01-01

    Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H 2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within ??2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol-1 K-1 for 1/n CH4??H 2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled. ?? 2006 American Chemical Society.

  14. Experimental study and thermodynamic modeling of CO2 gas hydrate formation in presence of zinc oxide nanoparticles

    International Nuclear Information System (INIS)

    Mohammadi, Mohsen; Haghtalab, Ali; Fakhroueian, Zahra

    2016-01-01

    Highlights: • Nanofluids enhance heat and mass transfer and affect on kinetic and thermodynamics. • The ZnO nanoparticles in liquid affect on kinetics and P-T curve of CO 2 hydrate. • ZnO nanoparticles enhance the growth rate and gas storage in CO 2 hydrate. • A thermodynamic modeling of CO 2 hydrate proposed in the presence of nanoparticles. • Water activity in ZnO + nanofluid was affected by enhancement of the CO 2 solubility. - Abstract: The effect of synthesized zinc oxide (ZnO) nanoparticles was investigated on the kinetic and thermodynamic equilibrium conditions of CO 2 hydrate formation. The amount of the gas consumption was measured and compared for the four sample fluids: pure water, aqueous solution of sodium dodecyl sulfate (SDS), water-based ZnO-nanofluid and water-based ZnO-nanofluid in the presence of SDS (0.001 mass fraction). The time of hydrate growth decreased and the amount of the storage gas enhanced in the presence of nanoparticles. Moreover, the nanoparticles size effect besides the CO 2 solubility enhancement in ZnO-nanofluid led to the reduction of water activity, so that the equilibrium curve of hydrate formation was shifted to higher pressures. A new correlation for Henry’s law constant was obtained using CO 2 -solubility data in ZnO-nanofluid. Finally using this correlation, the water activity was calculated through the Chen–Guo approach to propose a thermodynamic method for prediction of the equilibrium hydrate formation conditions in the presence of the nanoparticles.

  15. Quantum dynamics of small H2 and D2 clusters in the large cage of structure II clathrate hydrate: Energetics, occupancy, and vibrationally averaged cluster structures

    Science.gov (United States)

    Sebastianelli, Francesco; Xu, Minzhong; Bačić, Zlatko

    2008-12-01

    We report diffusion Monte Carlo (DMC) calculations of the quantum translation-rotation (T-R) dynamics of one to five para-H2 (p-H2) and ortho-D2 (o-D2) molecules inside the large hexakaidecahedral (51264) cage of the structure II clathrate hydrate, which was taken to be rigid. These calculations provide a quantitative description of the size evolution of the ground-state properties, energetics, and the vibrationally averaged geometries, of small (p-H2)n and (o-D2)n clusters, n=1-5, in nanoconfinement. The zero-point energy (ZPE) of the T-R motions rises steeply with the cluster size, reaching 74% of the potential well depth for the caged (p-H2)4. At low temperatures, the rapid increase of the cluster ZPE as a function of n is the main factor that limits the occupancy of the large cage to at most four H2 or D2 molecules, in agreement with experiments. Our DMC results concerning the vibrationally averaged spatial distribution of four D2 molecules, their mean distance from the cage center, the D2-D2 separation, and the specific orientation and localization of the tetrahedral (D2)4 cluster relative to the framework of the large cage, agree very well with the low-temperature neutron diffraction experiments involving the large cage with the quadruple D2 occupancy.

  16. A rigorous mechanistic model for predicting gas hydrate formation kinetics: The case of CO2 recovery and sequestration

    International Nuclear Information System (INIS)

    ZareNezhad, Bahman; Mottahedin, Mona

    2012-01-01

    Highlights: ► A mechanistic model for predicting gas hydrate formation kinetics is presented. ► A secondary nucleation rate model is proposed for the first time. ► Crystal–crystal collisions and crystal–impeller collisions are distinguished. ► Simultaneous determination of nucleation and growth kinetics are established. ► Important for design of gas hydrate based energy storage and CO 2 recovery systems. - Abstract: A rigorous mechanistic model for predicting gas hydrate formation crystallization kinetics is presented and the special case of CO 2 gas hydrate formation regarding CO 2 recovery and sequestration processes has been investigated by using the proposed model. A physical model for prediction of secondary nucleation rate is proposed for the first time and the formation rates of secondary nuclei by crystal–crystal collisions and crystal–impeller collisions are formulated. The objective functions for simultaneous determination of nucleation and growth kinetics are presented and a theoretical framework for predicting the dynamic behavior of gas hydrate formation is presented. Predicted time variations of CO 2 content, total number and surface area of produced hydrate crystals are in good agreement with the available experimental data. The proposed approach can have considerable application for design of gas hydrate converters regarding energy storage and CO 2 recovery processes.

  17. Application of gas hydrate formation in separation processes: A review of experimental studies

    International Nuclear Information System (INIS)

    Eslamimanesh, Ali; Mohammadi, Amir H.; Richon, Dominique; Naidoo, Paramespri; Ramjugernath, Deresh

    2012-01-01

    Highlights: ► Review of gas hydrate technology applied to separation processes. ► Gas hydrates have potential to be a future sustainable separation technology. ► More theoretical, simulation, and economic studies needed. - Abstract: There has been a dramatic increase in gas hydrate research over the last decade. Interestingly, the research has not focussed on only the inhibition of gas hydrate formation, which is of particular relevance to the petroleum industry, but has evolved into investigations on the promotion of hydrate formation as a potential novel separation technology. Gas hydrate formation as a separation technology shows tremendous potential, both from a physical feasibility (in terms of effecting difficult separations) as well as an envisaged lower energy utilization criterion. It is therefore a technology that should be considered as a future sustainable technology and will find wide application, possibly replacing a number of current commercial separation processes. In this article, we focus on presenting a brief description of the positive applications of clathrate hydrates and a comprehensive survey of experimental studies performed on separation processes using gas hydrate formation technology. Although many investigations have been undertaken on the positive application of gas hydrates to date, there is a need to perform more theoretical, experimental, and economic studies to clarify various aspects of separation processes using clathrate/semi-clathrate hydrate formation phenomena, and to conclusively prove its sustainability.

  18. Hydrate equilibrium data for the CO2 + N2 system with the use of tetra-n-butylammonium bromide (TBAB), cyclopentane (CP) and their mixture

    DEFF Research Database (Denmark)

    Tzirakis, Fragkiskos; Stringari, Paolo; von Solms, Nicolas

    2016-01-01

    Carbon Dioxide capture and sequestration (CCS) is nowadays an important area of research for decreasing CO2 emissions worldwide. Hydrates can become of great importance in the future as they form the basis for a new technology that can be used for CO2 capture from flue gases (hydrate...... crystallization). In this work hydrate equilibrium data are measured and compared with literature data. In particular, experimental results for hydrate dissociation with several promoters are presented. The isochoric method is used to determine the gas hydrate dissociation points. Different CO2 + N2 gas mixtures...

  19. Gas Hydrate Research Database and Web Dissemination Channel

    Energy Technology Data Exchange (ETDEWEB)

    Micheal Frenkel; Kenneth Kroenlein; V Diky; R.D. Chirico; A. Kazakow; C.D. Muzny; M. Frenkel

    2009-09-30

    To facilitate advances in application of technologies pertaining to gas hydrates, a United States database containing experimentally-derived information about those materials was developed. The Clathrate Hydrate Physical Property Database (NIST Standard Reference Database {number_sign} 156) was developed by the TRC Group at NIST in Boulder, Colorado paralleling a highly-successful database of thermodynamic properties of molecular pure compounds and their mixtures and in association with an international effort on the part of CODATA to aid in international data sharing. Development and population of this database relied on the development of three components of information-processing infrastructure: (1) guided data capture (GDC) software designed to convert data and metadata into a well-organized, electronic format, (2) a relational data storage facility to accommodate all types of numerical and metadata within the scope of the project, and (3) a gas hydrate markup language (GHML) developed to standardize data communications between 'data producers' and 'data users'. Having developed the appropriate data storage and communication technologies, a web-based interface for both the new Clathrate Hydrate Physical Property Database, as well as Scientific Results from the Mallik 2002 Gas Hydrate Production Research Well Program was developed and deployed at http://gashydrates.nist.gov.

  20. Hydrate Equilibrium Data for CO2+N-2 System in the Presence of Tetra-n-butylammonium Fluoride (TBAF) and Mixture of TBAF and Cyclopentane (CP)

    DEFF Research Database (Denmark)

    Tzirakis, Fragkiskos; Stringari, Paolo; Coquelet, Christophe

    2016-01-01

    Hydrates can be used for CO2 capture from flue gases (hydrate crystallization). In this work, hydrate equilibrium data were measured and compared with literature data. The isochoric method was used to determine the gas hydrate dissociation points. Different CO2+N2 gas mixtures were used...

  1. Structural transformations of sVI tert-butylamine hydrates to sII binary hydrates with methane.

    Science.gov (United States)

    Prasad, Pinnelli S R; Sugahara, Takeshi; Sloan, E Dendy; Sum, Amadeu K; Koh, Carolyn A

    2009-10-22

    Binary clathrate hydrates with methane (CH(4), 4.36 A) and tert-butylamine (t-BuNH(2), 6.72 A) as guest molecules were synthesized at different molar concentrations of t-BuNH(2) (1.00-9.31 mol %) with methane at 7.0 MPa and 250 K, and were characterized by powder X-ray diffraction (PXRD) and Raman microscopy. A structural transformation from sVI to sII of t-BuNH(2) hydrate was clearly observed on pressurizing with methane. The PXRD showed sII signatures and the remnant sVI signatures were insignificant, implying the metastable nature of sVI binary hydrates. Raman spectroscopic data on these binary hydrates suggest that the methane molecules occupy the small cages and vacant large cages. The methane storage capacity in this system was nearly doubled to approximately 6.86 wt % for 5.56 mol % > t-BuNH(2) > 1.0 mol %.

  2. Experimental investigation of methane release from hydrate formation in sandstone through both hydrate dissociation and CO{sub 2} sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Husebo, J.; Graue, A.; Kvamme, B. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology; Stevens, J.; Howard, J.J. [ConocoPhillips, Ponca City, OK (United States); Baldwin, B.A. [Green Country Petrophysics LLC, Dewey, OK (United States)

    2008-07-01

    Large amounts of natural gas trapped in hydrate reservoirs are found in Arctic regions and in deep offshore locations around the world. Natural gas production from hydrate deposits offer significant potential for future energy needs. However, research is needed in order to propose potential production schemes for natural gas hydrates. Natural gas molecules can be freed from hydrate structured cages by depressurization, by heating and by exposing the hydrate to a substance that will form a thermodynamically more stable hydrate structure. This paper provided a comparison of two approaches for releasing methane from methane hydrate in porous sandstone. The study scope covered the dissociation rate of methane hydrate in porous media through depressurization, and also referred to previous work done on producing methane from hydrates in sandstone while sequestering carbon dioxide (CO{sub 2}). The study was conducted in a laboratory setting. The paper discussed the experimental design which included the placing of a pressure- and temperature-controlled sample holder inside the bore of a magnetic resonance imager. The experimental procedures were then outlined, with reference to hydrate formation; carbon dioxide sequestration; hydrate dissociation experiments with constant volume; and hydrate dissociation experiments at constant pressure. The constant volume experiments demonstrated that in order to dissociate a large amount of hydrate, the initial depressurization had to be significantly lower than the hydrate stability pressure. 9 refs., 9 figs.

  3. Synthesis and thermal conductivity of type II silicon clathrates

    Science.gov (United States)

    Beekman, M.; Nolas, G. S.

    2006-08-01

    We have synthesized and characterized polycrystalline Na 1Si 136 and Na 8Si 136, compounds possessing the type II clathrate hydrate crystal structure. Resistivity measurements from 10 to 300 K indicate very large resistivities in this temperature range, with activated temperature dependences indicative of relatively large band gap semiconductors. The thermal conductivity is very low; two orders-of-magnitude lower than that of diamond-structure silicon at room temperature. The thermal conductivity of Na 8Si 136 displays a temperature dependence that is atypical of crystalline solids and more indicative of amorphous materials. This work is part of a continuing effort to explore the many different compositions and structure types of clathrates, a class of materials that continues to be of interest for scientific and technological applications.

  4. Effects of hydration and oxygen vacancy on CO2 adsorption and activation on beta-Ga2O3(100).

    Science.gov (United States)

    Pan, Yun-xiang; Liu, Chang-jun; Mei, Donghai; Ge, Qingfeng

    2010-04-20

    The effects of hydration and oxygen vacancy on CO(2) adsorption on the beta-Ga(2)O(3)(100) surface have been studied using density functional theory slab calculations. Adsorbed CO(2) is activated on the dry perfect beta-Ga(2)O(3)(100) surface, resulting in a carbonate species. This adsorption is slightly endothermic, with an adsorption energy of 0.07 eV. Water is preferably adsorbed molecularly on the dry perfect beta-Ga(2)O(3)(100) surface with an adsorption energy of -0.56 eV, producing a hydrated perfect beta-Ga(2)O(3)(100) surface. Adsorption of CO(2) on the hydrated surface as a carbonate species is also endothermic, with an adsorption energy of 0.14 eV, indicating a slightly repulsive interaction when H(2)O and CO(2) are coadsorbed. The carbonate species on the hydrated perfect surface can be protonated by the coadsorbed H(2)O to a bicarbonate species, making the CO(2) adsorption exothermic, with an adsorption energy of -0.13 eV. The effect of defects on CO(2) adsorption and activation has been examined by creating an oxygen vacancy on the dry beta-Ga(2)O(3)(100) surface. The formation of an oxygen vacancy is endothermic, by 0.34 eV, with respect to a free O(2) molecule in the gas phase. Presence of the oxygen vacancy promoted the adsorption and activation of CO(2). In the most stable CO(2) adsorption configuration on the dry defective beta-Ga(2)O(3)(100) surface with an oxygen vacancy, one of the oxygen atoms of the adsorbed CO(2) occupies the oxygen vacancy site, and the CO(2) adsorption energy is -0.31 eV. Water favors dissociative adsorption at the oxygen vacancy site on the defective surface. This process is spontaneous, with a reaction energy of -0.62 eV. These results indicate that, when water and CO(2) are present in the adsorption system simultaneously, water will compete with CO(2) for the oxygen vacancy sites and impact CO(2) adsorption and conversion negatively.

  5. Experimental study and thermodynamic modelling of methane clathrate hydrate dissociation conditions in silica gel porous media in the presence of methanol aqueous solution

    International Nuclear Information System (INIS)

    Hashemi, Hamed; Javanmardi, Jafar; Zarifi, Mojdeh; Eslamimanesh, Ali; Mohammadi, Amir H.

    2012-01-01

    Highlights: ► Phase equilibria of hydrates of methane in confined silica gel pores are reported. ► Dissociation data in the presences of methanol aqueous solution are also measured. ► A thermodynamic model is developed for prediction of the obtained data. ► Acceptable agreement is found between the obtained data and the predicted results. - Abstract: In this work, the phase equilibria of clathrate hydrates of methane in the presence of pure water and 0.035 mass fraction of methanol aqueous solution in confined silica gel pores with (10 and 15) nm mean diameters are measured and reported. A thermodynamic model is also developed for prediction of the obtained experimental hydrate dissociation data. The Valderrama–Patel–Teja (VPT-EoS) equation of state (EoS) accompanied with the non-density dependent (NDD) mixing rules coupled with a previously developed activity model are applied to evaluate the fugacity of the species present and the activity coefficient of water in methanol aqueous solution. Acceptable agreement between the reported data and the predicted results using the proposed model and an existing method reported in the literature demonstrates the reliability of the presented model.

  6. Experimental investigation on TBAB clathrate hydrate slurry flows in a horizontal tube: Forced convective heat transfer behaviors

    Energy Technology Data Exchange (ETDEWEB)

    Wenji, Song [Guangzhou Institute of Energy Conversion, CAS, No. 2 Nengyuan Road, Tianhe District, Guangzhou 510640 (China); Key Laboratory of Renewable Energy and Gas Hydrate, CAS, No. 2 Nengyuan Road, Tianhe District, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Rui, Xiao; Chong, Huang; Shihui, He; Kaijun, Dong; Ziping, Feng [Guangzhou Institute of Energy Conversion, CAS, No. 2 Nengyuan Road, Tianhe District, Guangzhou 510640 (China); Key Laboratory of Renewable Energy and Gas Hydrate, CAS, No. 2 Nengyuan Road, Tianhe District, Guangzhou 510640 (China)

    2009-11-15

    Tetra-n-butyl-ammonium bromide (TBAB) clathrate hydrate slurry (CHS) is one kind of secondary refrigerants, which is promising to be applied into air-conditioning or latent-heat transportation systems as a thermal storage or cold carrying medium for energy saving. It is a solid-liquid two phase mixture which is easy to produce and has high latent heat and good fluidity. In this paper, the heat transfer characteristics of TBAB slurry were investigated in a horizontal stainless steel tube under different solid mass fractions and flow velocities with constant heat flux. One velocity region of weakened heat transfer was found. Moreover, TBAB CHS was treated as a kind of Bingham fluids, and the influences of the solid particles, flow velocity and types of flow on the forced convective heat transfer coefficients of TBAB CHS were investigated. At last, criterial correlations of Nusselt number for laminar and turbulent flows in the form of power function were summarized, and the error with experimental results was within {+-}20%. (author)

  7. Weak interactions between water and clathrate-forming gases at low pressures

    Energy Technology Data Exchange (ETDEWEB)

    Thurmer, Konrad; Yuan, Chunqing; Kimmel, Gregory A.; Kay, Bruce D.; Smith, R. Scott

    2015-11-01

    Using scanning probe microscopy and temperature programed desorption we examined the interaction between water and two common clathrate-forming gases, methane and isobutane, at low temperature and low pressure. Water co-deposited with up to 10-1 mbar methane or 10-5 mbar isobutane at 140 K onto a Pt(111) substrate yielded pure crystalline ice, i.e., the exposure to up to ~107 gas molecules for each deposited water molecule did not have any detectable effect on the growing films. Exposing metastable, less than 2 molecular layers thick, water films to 10-5 mbar methane does not alter their morphology, suggesting that the presence of the Pt(111) surface is not a strong driver for hydrate formation. This weak water-gas interaction at low pressures is supported by our thermal desorption measurements from amorphous solid water and crystalline ice where 1 ML of methane desorbs near ~43 K and isobutane desorbs near ~100 K. Similar desorption temperatures were observed for desorption from amorphous solid water.

  8. Effects of C3H8 on hydrate formation and dissociation for integrated CO2 capture and desalination technology

    International Nuclear Information System (INIS)

    Yang, Mingjun; Zheng, Jianan; Liu, Weiguo; Liu, Yu; Song, Yongchen

    2015-01-01

    Hydrate-based technology has been developing for decades to meet the demands in industrial applications. With the global demands for reduced carbon dioxide (CO 2 ) emissions and more fresh water, CHBD (CO 2 hydrate-based desalination) was proposed and has developed rapidly. In this study, to provide basic data for the improvement of CHBD, the thermodynamic and kinetic characteristics of CO 2 and propane (C 3 H 8 ) mixed-gas hydrates in salt solution were experimentally investigated in which C 3 H 8 was chosen as the hydrate formation promoter. We studied nine experimental cases (54 cycles) with different C 3 H 8 proportions (ranging from 0 to 13%) and different initial solution saturations (30%, 40% and 50%). The hydrate phase equilibrium data were generated using the isochoric method, and the hydrate formation saturations were calculated using the relative gas uptake equation. The results indicated that the increase in the C 3 H 8 proportion significantly decreases the gas mixture hydrate equilibrium pressure. Additionally, the relative gas uptake was reduced as the C 3 H 8 proportion increased. A lower relative gas uptake was obtained at a lower gas pressure for the same gas mixture. The initial solution saturation exhibited an insignificant effect on the hydrate phase equilibrium conditions. When the initial solution saturations increased from 30% to 50%, the relative gas uptake decreased. - Highlights: • C 3 H 8 improves the thermodynamics and kinetics of CO 2 hydrates formation. • Hydrates equilibrium pressure decreases with the increase of C 3 H 8 proportion. • Higher C 3 H 8 proportion and/or solution saturation decrease relative gas uptake. • Initial pressure and solution saturation has interactive effect on gas uptake.

  9. Carbon-14 immobilization via the CO2-Ba(OH)2 hydrate gas-solid reaction

    International Nuclear Information System (INIS)

    Haag, G.L.

    1980-01-01

    Although no restrictions have been placed on the release of carbon-14, it has been identified as a potential health hazard due to the ease in which it may be assimilated into the biosphere. The intent of the Carbon-14 Immobilization Program, funded through the Airborne Waste Program Management Office, is to develop and demonstrate a novel process for restricting off-gas releases of carbon-14 from various nuclear facilities. The process utilizes the CO 2 -Ba(OH) 2 hydrate gas-solid reaction to directly remove and immobilize carbon-14. The reaction product, BaCO 3 , possesses both the thermal and chemical stability desired for long-term waste disposal. The process is capable of providing decontamination factors in excess of 1000 and reactant utilization of greater than 99% in the treatment of high volumetric, airlike (330 ppM CO 2 ) gas streams. For the treatment of an air-based off-gas stream, the use of packed beds of Ba(OH) 2 .8H 2 O flakes to remove CO 2 has been demonstrated. However, the operating conditions must be maintained between certain upper and lower limits with respect to the partial pressure of water. If the water vapor pressure in the gas is less than the dissociation vapor pressure of Ba(OH) 2 .8H 2 O, the bed will deactivate. If the vapor pressure is considerably greater, pressure drop problems will increase with increasing humidity as the particles curl and degrade. Results have indicated that when operated in the proper regime, the bulk of the increase in pressure drop results from the conversion of Ba(OH) 2 .8H 2 O to BaCO 3 and not from the hydration of the commercial Ba(OH) 2 .8H 2 O (i.e. Ba(OH) 2 .7.50H 2 O) to Ba(OH) 2 .8H 2 O

  10. Experimental observations on the competing effect of tetrahydrofuran and an electrolyte and the strength of hydrate inhibition among metal halides in mixed CO2 hydrate equilibria

    International Nuclear Information System (INIS)

    Sabil, Khalik M.; Roman, Vicente R.; Witkamp, Geert-Jan; Peters, Cor J.

    2010-01-01

    In the present work, experimental data on the equilibrium conditions of mixed CO 2 and THF hydrates in aqueous electrolyte solutions are reported. Seven different electrolytes (metal halides) were used in this work namely sodium chloride (NaCl), calcium chloride (CaCl 2 ), magnesium chloride (MgCl 2 ), potassium bromide (KBr), sodium fluoride (NaF), potassium chloride (KCl), and sodium bromide (NaBr). All equilibrium data were measured by using Cailletet apparatus. Throughout this work, the overall concentration of CO 2 and THF were kept constant at (0.04 and 0.05) mol fraction, respectively, while the concentration of electrolytes were varied. The experimental temperature ranged from (275 to 305) K and pressure up 7.10 MPa had been applied. From the experimental results, it is concluded that THF, which is soluble in water is able to suppress the salt inhibiting effect in the range studied. In all quaternary systems studied, a four-phase hydrate equilibrium line was observed where hydrate (H), liquid water (L W ), liquid organic (L V ), and vapour (V) exist simultaneously at specific pressure and temperature. The formation of this four-phase equilibrium line is mainly due to a liquid-liquid phase split of (water + THF) mixture when pressurized with CO 2 and the split is enhanced by the salting-out effect of the electrolytes in the quaternary system. The strength of hydrate inhibition effect among the electrolytes was compared. The results shows the hydrate inhibiting effect of the metal halides is increasing in the order NaF 2 2 . Among the cations studied, the strength of hydrate inhibition increases in the following order: K + + 2+ 2+ . Meanwhile, the strength of hydrate inhibition among the halogen anion studied decreases in the following order: Br - > Cl - > F - . Based on the results, it is suggested that the probability of formation and the strength of ionic-hydrogen bond between an ion and water molecule and the effects of this bond on the ambient water

  11. Impact of pressure on the dynamic behavior of CO2 hydrate slurry in a stirred tank reactor applied to cold thermal energy storage

    International Nuclear Information System (INIS)

    Dufour, Thomas; Hoang, Hong Minh; Oignet, Jérémy; Osswald, Véronique; Clain, Pascal; Fournaison, Laurence; Delahaye, Anthony

    2017-01-01

    Highlights: •CO 2 hydrate storage was studied in a stirred tank reactor under pressure. •CO 2 hydrates can store three times more energy than water during the same time. •Increasing CO 2 hydrate pressure decreases charge time for the same stored energy. •CO 2 hydrate storage allow average power exchange to be maintained along the process. -- Abstract: Phase change material (PCM) slurries are considered as high-performance fluids for secondary refrigeration and cold thermal energy storage (CTES) systems thanks to their high energy density. Nevertheless, the efficiency of such system is limited by storage dynamic. In fact, PCM charging or discharging rate is governed by system design (storage tank, heat exchanger), heat transfer fluid temperature and flow rate (cold or hot source), and PCM temperature. However, with classical PCM (ice, paraffin…), phase change temperature depends only on material/fluid nature and composition. In the case of gas hydrates, phase change temperature is also controlled by pressure. In the current work, the influence of pressure on cold storage with gas hydrates was studied experimentally using a stirred tank reactor equipped with a cooling jacket. A tank reactor model was also developed to assess the efficiency of this storage process. The results showed that pressure can be used to adjust phase change temperature of CO 2 hydrates, and consequently charging/discharging time. For the same operating conditions and during the same charging time, the amount of stored energy using CO 2 hydrates can be three times higher than that using water. By increasing the initial pressure from 2.45 to 3.2 MPa (at 282.15 K), it is also possible to decrease the charging time by a factor of 3. Finally, it appears that the capacity of pressure to increase CO 2 -hydrate phase-change temperature can also improve system efficiency by decreasing thermal losses.

  12. The mechanism of vapor phase hydration of calcium oxide: implications for CO2 capture.

    Science.gov (United States)

    Kudłacz, Krzysztof; Rodriguez-Navarro, Carlos

    2014-10-21

    Lime-based sorbents are used for fuel- and flue-gas capture, thereby representing an economic and effective way to reduce CO2 emissions. Their use involves cyclic carbonation/calcination which results in a significant conversion reduction with increasing number of cycles. To reactivate spent CaO, vapor phase hydration is typically performed. However, little is known about the ultimate mechanism of such a hydration process. Here, we show that the vapor phase hydration of CaO formed after calcination of calcite (CaCO3) single crystals is a pseudomorphic, topotactic process, which progresses via an intermediate disordered phase prior to the final formation of oriented Ca(OH)2 nanocrystals. The strong structural control during this solid-state phase transition implies that the microstructural features of the CaO parent phase predetermine the final structural and physicochemical (reactivity and attrition) features of the product hydroxide. The higher molar volume of the product can create an impervious shell around unreacted CaO, thereby limiting the efficiency of the reactivation process. However, in the case of compact, sintered CaO structures, volume expansion cannot be accommodated in the reduced pore volume, and stress generation leads to pervasive cracking. This favors complete hydration but also detrimental attrition. Implications of these results in carbon capture and storage (CCS) are discussed.

  13. Pentagonal dodecahedron methane hydrate cage and methanol ...

    Indian Academy of Sciences (India)

    methane hydrate in sea bed near continental margin and underneath of permafrost ... clathrate structure,6,7 IR spectroscopy analysis of vibra- tional form of guest .... Hydrogen (H71) of the hydroxyl group of methanol is found to have formed ...

  14. The formation of gas hydrates and the effect of inhibitiors on their ...

    African Journals Online (AJOL)

    Natural gas hydrate is a solid crystalline compound produced by combining water and gas and it is considered as the clathrates. Guest gas molecules are stuck insider the pores of water networks produced by hydrogen bonds between molecules of water. There are different ways to analyze the hydrate formation operating ...

  15. Experimental observations on the competing effect of tetrahydrofuran and an electrolyte and the strength of hydrate inhibition among metal halides in mixed CO{sub 2} hydrate equilibria

    Energy Technology Data Exchange (ETDEWEB)

    Sabil, Khalik M., E-mail: khalik_msabil@petronas.com.m [Delft University of Technology, Laboratory of Process Equipment, Mechanical, Maritime and Materials Engineering, Leeghwaterstraat 44, 2628 CA Delft (Netherlands); Universiti Teknologi PETRONAS, Chemical Engineering Programme, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Roman, Vicente R.; Witkamp, Geert-Jan [Delft University of Technology, Laboratory of Process Equipment, Mechanical, Maritime and Materials Engineering, Leeghwaterstraat 44, 2628 CA Delft (Netherlands); Peters, Cor J., E-mail: C.J.Peters@tudelft.n [Delft University of Technology, Laboratory of Process Equipment, Mechanical, Maritime and Materials Engineering, Leeghwaterstraat 44, 2628 CA Delft (Netherlands); Petroleum Institute, Chemical Engineering Program, Bu Hasa Building, Room 2207A, P.O. Box 2533, Abu Dhabi (United Arab Emirates)

    2010-03-15

    In the present work, experimental data on the equilibrium conditions of mixed CO{sub 2} and THF hydrates in aqueous electrolyte solutions are reported. Seven different electrolytes (metal halides) were used in this work namely sodium chloride (NaCl), calcium chloride (CaCl{sub 2}), magnesium chloride (MgCl{sub 2}), potassium bromide (KBr), sodium fluoride (NaF), potassium chloride (KCl), and sodium bromide (NaBr). All equilibrium data were measured by using Cailletet apparatus. Throughout this work, the overall concentration of CO{sub 2} and THF were kept constant at (0.04 and 0.05) mol fraction, respectively, while the concentration of electrolytes were varied. The experimental temperature ranged from (275 to 305) K and pressure up 7.10 MPa had been applied. From the experimental results, it is concluded that THF, which is soluble in water is able to suppress the salt inhibiting effect in the range studied. In all quaternary systems studied, a four-phase hydrate equilibrium line was observed where hydrate (H), liquid water (L{sub W}), liquid organic (L{sub V}), and vapour (V) exist simultaneously at specific pressure and temperature. The formation of this four-phase equilibrium line is mainly due to a liquid-liquid phase split of (water + THF) mixture when pressurized with CO{sub 2} and the split is enhanced by the salting-out effect of the electrolytes in the quaternary system. The strength of hydrate inhibition effect among the electrolytes was compared. The results shows the hydrate inhibiting effect of the metal halides is increasing in the order NaF < KBr < NaCl < NaBr < CaCl{sub 2} < MgCl{sub 2}. Among the cations studied, the strength of hydrate inhibition increases in the following order: K{sup +} < Na{sup +} < Ca{sup 2+} < Mg{sup 2+}. Meanwhile, the strength of hydrate inhibition among the halogen anion studied decreases in the following order: Br{sup -} > Cl{sup -} > F{sup -}. Based on the results, it is suggested that the probability of formation and

  16. Enceladus' near-surface CO2 gas pockets and surface frost deposits

    Science.gov (United States)

    Matson, Dennis L.; Davies, Ashley Gerard; Johnson, Torrence V.; Combe, Jean-Philippe; McCord, Thomas B.; Radebaugh, Jani; Singh, Sandeep

    2018-03-01

    Solid CO2 surface deposits were reported in Enceladus' South Polar Region by Brown et al. (2006). They noted that such volatile deposits are temporary and posited ongoing replenishment. We present a model for this replenishment by expanding on the Matson et al. (2012) model of subsurface heat and chemical transport in Enceladus. Our model explains the distributions of both CO2 frost and complexed CO2 clathrate hydrate as seen in the Cassini Visual and Infrared Mapping Spectrometer (VIMS) data. We trace the journey of CO2 from a subsurface ocean. The ocean-water circulation model of Matson et al. (2012) brings water up to near the surface where gas exsolves to form bubbles. Some of the CO2 bubbles are trapped and form pockets of gas in recesses at the bottom of the uppermost ice layer. When fissures break open these pockets, the CO2 gas is vented. Gas pocket venting is episodic compared to the more or less continuous eruptive plumes, emanating from the "tiger stripes", that are supported by plume chambers. Two styles of gas pocket venting are considered: (1) seeps, and (2) blowouts. The presence of CO2 frost patches suggests that the pocket gas slowly seeped through fractured, cold ice and when some of the gas reached the surface it was cold enough to condense (i.e., T ∼70 to ∼119 K). If the fissure opening is large, a blowout occurs. The rapid escape of gas and drop in pocket pressure causes water in the pocket to boil and create many small aerosol droplets of seawater. These may be carried along by the erupting gas. Electrically charged droplets can couple to the magnetosphere, and be dragged away from Enceladus. Most of the CO2 blowout gas escapes from Enceladus and the remainder is distributed globally. However, CO2 trapped in a clathrate structure does not escape. It is much heavier and slower moving than the CO2 gas. Its motion is ballistic and has an average range of about 17 km. Thus, it contributes to deposits in the vicinity of the vent. Local heat

  17. Experimental and theoretical investigations on the carbon dioxide gas hydrate formation kinetics at the onset of turbidity regarding CO2 capture and sequestration processes

    International Nuclear Information System (INIS)

    ZareNezhad, Bahman; Mottahedin, Mona; Varaminian, Farshad

    2013-01-01

    The carbon dioxide gas hydrate formation kinetics at the onset of turbidity is experimentally and theoretically investigated. It is shown that the time-dependent heterogeneous nucleation and growth kinetics are simultaneously governing the hydrate formation process at the onset of turbidity. A new approach is also presented for determination of gas hydrate-liquid interfacial tension. The CO 2 hydrate-liquid interfacial tension according to the suggested heterogeneous nucleation mechanism is found to be about 12.7 mJ/m 2 . The overall average absolute deviation between predicted and measured CO 2 molar consumption is about 0.61%, indicating the excellent accuracy of the proposed model for studying the hydrate-based CO 2 capture and sequestration processes over wide ranges of pressures and temperatures

  18. Influence of fluorosurfactants on hydrate formation rates

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.U.; Jeong, K.E.; Chae, H.J.; Jeong, S.Y. [Korea Reasearch Inst. of Chemical Technology, Alternative Chemicals/Fuel Research Center, Yuseong-Gu, Daejon (Korea, Republic of)

    2008-07-01

    Gas hydrates, or clathrates, are ice-like solids that forms when natural gas is in contact with liquid water or ice under high pressure and low temperature. There is significant interest in studying the storage and transportation of gas in the form of hydrates. However, a critical problem impacting the industrial application of gas hydrates for storage and transportation of natural gas is the slow formation rate of natural gas hydrate. Researchers have previously reported on the promotion effect of some additives on gas hydrate formation and hydrate gas content. Fluorosurfactants are significantly superior to nonfluorinated surfactants in wetting action, as well as stability in harsh environments, both thermal and chemical. This paper discussed an experimental investigation into the effects of fluorosurfactants with different ionic types on the formation of methane hydrate. The surfactants used were FSN-100 of DuPont Zonyl as non-ionic surfactant and FC-143 of DuPont as anionic surfactant. The paper discussed the experimental apparatus for methane hydrate formation. It also discussed hydrate formation kinetics and the series of hydrate formation experiments that were conducted in the presence of fluorosurfactants. Last, the paper explored the results of the study. It was concluded that anionic fluorosurfactant of FC-143 had a better promoting effect on methane hydrate formation compared with nonionic surfactant of FSN-100. 8 refs., 2 tabs., 2 figs.

  19. Crystal structure of clathrates of Hofmann dma-type

    International Nuclear Information System (INIS)

    NIshikiori, Sh.; Ivamoto, T.

    1999-01-01

    Seven new clathrates Cd(DMA) 2 Ni(CN) 4 ·xG (x=1, G=aniline, 2,3-xylidine, 2,4-xylidine, 2,5-xylidine, 2,6-xylidine, 3,5-xylidine, and x=2, G=2,4,6-trimethylaniline) of Hofmann type are synthesized by amine substitution for dimethylamine (DMA). On the base of x-ray diffraction data it is shown that geometry of guest molecule in cage-like hollow determines the structure of the host and crystal structure of clathrates. Two-dimension metallocomplex of the host of studied clathrates is characterized by elastic folded structure appearing as a result of angular deformation of bond between Cd atoms and host cyanide bridge. Guest molecule orientation is fixed by hydrogen bond. Structural elasticity of the host complex directs to differences in crystal structure of clathrates formed and to considerable variety of incorporated guests [ru

  20. Hydrate phase equilibria of CO2+N2+aqueous solution of THF, TBAB or TBAF system

    DEFF Research Database (Denmark)

    Sfaxi, Imen Ben Attouche; Durand, Isabelle; Lugo, Rafael

    2014-01-01

    We report hydrate dissociation conditions of CO2 (15 and 30mol%)+N2 (85 and 70mol%) in the presence of aqueous solutions of THF, TBAB or TBAF. The concentrations of TBAB and TBAF in the aqueous solutions are 5wt% and 9wt% while THF concentration in aqueous solution is 3mol%. Two different experim...

  1. Sulphation and carbonation properties of hydrated sorbents from a fluidized bed CO{sub 2} looping cycle reactor

    Energy Technology Data Exchange (ETDEWEB)

    Vasilije Manovic; Edward J. Anthony; Dennis Y. Lu [CANMET Energy Technology Centre-Ottawa, Ottawa, ON (Canada)

    2008-10-15

    Sulphation and carbonation have been performed on hydrated spent residues from a 75 kW{sub th} dual fluidized bed combustion (FBC) pilot plant operating as a CO{sub 2} looping cycle unit. The sulphation and carbonation tests were done in an atmospheric pressure thermogravimetric analyzer (TGA), with the sulphation performed using synthetic flue gas (0.45% SO{sub 2}, 3% O{sub 2}, 15% CO{sub 2} and N{sub 2} balance). Additional tests were carried out in a tube furnace (TF) with a higher SO{sub 2} concentration (1%) and conversions were determined by quantitative X-ray diffraction (QXRD) analyses. The morphology of the sulphated samples from the TF was examined by scanning electron microscopy (SEM). Sulphation tests were performed at 850{sup o}C for 150 min and carbonation tests at 750{sup o}C, 10 cycles for 15 min (7.5 min calcination + 7.5 min carbonation). Sulphation conversions obtained for the hydrated samples depended on sample type: in the TGA, they were 75-85% (higher values were obtained for samples from the carbonator); and in the TF, values around 90% and 70% for sample from carbonator and calciner, respectively, were achieved, in comparison to the 40% conversion seen with the original sample. The SEM analyses showed significant residual porosity that can increase total conversion with longer sulphation time. The carbonation tests showed a smaller influence of the sample type and typical conversions after 10 cycles were 50% - about 10% higher than that for the original sample. The influence of hydration duration, in the range of 15-60 min, is not apparent, indicating that samples are ready for use for either SO{sub 2} retention, or further CO{sub 2} capture after at most 15 min using saturated steam. The present results show that, upon hydration, spent residues from FBC CO{sub 2} capture cycles are good sorbents for both SO{sub 2} retention and additional CO{sub 2} capture. 33 refs., 10 figs., 2 tabs.

  2. An ir study of M(1-propanethiol)2Ni(CN)4.G (M=Cd,Ni and G=benzene) clathrates

    International Nuclear Information System (INIS)

    Kartal, Z.; Tuerkoz, D.; Bahceli, S.

    2004-01-01

    Two Hofmann-propanethiol-type clathrates of the for M(1-propanethiol) 2 Ni(CN) 4 .G (M=Cd or Ni; G = benzene) have been prepared in the powder form. The 1-propanethiol (1-PT) molecules provide the cavities in which the quest benzene molecules in clathrate structure ar accommodated. The infrared investigations of the obtained clathrates indicate that these compounds are similar in structure to the other Hofmann-type clathrates (Authors)

  3. Methane clathrates in the solar system.

    Science.gov (United States)

    Mousis, Olivier; Chassefière, Eric; Holm, Nils G; Bouquet, Alexis; Waite, Jack Hunter; Geppert, Wolf Dietrich; Picaud, Sylvain; Aikawa, Yuri; Ali-Dib, Mohamad; Charlou, Jean-Luc; Rousselot, Philippe

    2015-04-01

    We review the reservoirs of methane clathrates that may exist in the different bodies of the Solar System. Methane was formed in the interstellar medium prior to having been embedded in the protosolar nebula gas phase. This molecule was subsequently trapped in clathrates that formed from crystalline water ice during the cooling of the disk and incorporated in this form into the building blocks of comets, icy bodies, and giant planets. Methane clathrates may play an important role in the evolution of planetary atmospheres. On Earth, the production of methane in clathrates is essentially biological, and these compounds are mostly found in permafrost regions or in the sediments of continental shelves. On Mars, methane would more likely derive from hydrothermal reactions with olivine-rich material. If they do exist, martian methane clathrates would be stable only at depth in the cryosphere and sporadically release some methane into the atmosphere via mechanisms that remain to be determined. In the case of Titan, most of its methane probably originates from the protosolar nebula, where it would have been trapped in the clathrates agglomerated by the satellite's building blocks. Methane clathrates are still believed to play an important role in the present state of Titan. Their presence is invoked in the satellite's subsurface as a means of replenishing its atmosphere with methane via outgassing episodes. The internal oceans of Enceladus and Europa also provide appropriate thermodynamic conditions that allow formation of methane clathrates. In turn, these clathrates might influence the composition of these liquid reservoirs. Finally, comets and Kuiper Belt Objects might have formed from the agglomeration of clathrates and pure ices in the nebula. The methane observed in comets would then result from the destabilization of clathrate layers in the nuclei concurrent with their approach to perihelion. Thermodynamic equilibrium calculations show that methane-rich clathrate

  4. A sublimation technique for high-precision measurements of δ13CO2 and mixing ratios of CO2 and N2O from air trapped in ice cores

    Directory of Open Access Journals (Sweden)

    H. Fischer

    2011-07-01

    Full Text Available In order to provide high precision stable carbon isotope ratios (δ13CO2 or δ13C of CO2 from small bubbly, partially and fully clathrated ice core samples we developed a new method based on sublimation coupled to gas chromatography-isotope ratio mass spectrometry (GC-IRMS. In a first step the trapped air is quantitatively released from ~30 g of ice and CO2 together with N2O are separated from the bulk air components and stored in a miniature glass tube. In an off-line step, the extracted sample is introduced into a helium carrier flow using a minimised tube cracker device. Prior to measurement, N2O and organic sample contaminants are gas chromatographically separated from CO2. Pulses of a CO2/N2O mixture are admitted to the tube cracker and follow the path of the sample through the system. This allows an identical treatment and comparison of sample and standard peaks. The ability of the method to reproduce δ13C from bubble and clathrate ice is verified on different ice cores. We achieve reproducibilities for bubble ice between 0.05 ‰ and 0.07 ‰ and for clathrate ice between 0.05 ‰ and 0.09 ‰ (dependent on the ice core used. A comparison of our data with measurements on bubble ice from the same ice core but using a mechanical extraction device shows no significant systematic offset. In addition to δ13C, the CO2 and N2O mixing ratios can be volumetrically derived with a precision of 2 ppmv and 8 ppbv, respectively.

  5. Nitrile hydration by thiolate- and alkoxide-ligated Co-NHase analogues. Isolation of Co(III)-amidate and Co(III)-iminol intermediates.

    Science.gov (United States)

    Swartz, Rodney D; Coggins, Michael K; Kaminsky, Werner; Kovacs, Julie A

    2011-03-23

    Nitrile hydratases (NHases) are thiolate-ligated Fe(III)- or Co(III)-containing enzymes, which convert nitriles to the corresponding amide under mild conditions. Proposed NHase mechanisms involve M(III)-NCR, M(III)-OH, M(III)-iminol, and M(III)-amide intermediates. There have been no reported crystallographically characterized examples of these key intermediates. Spectroscopic and kinetic data support the involvement of a M(III)-NCR intermediate. A H-bonding network facilitates this enzymatic reaction. Herein we describe two biomimetic Co(III)-NHase analogues that hydrate MeCN, and four crystallographically characterized NHase intermediate analogues, [Co(III)(S(Me2)N(4)(tren))(MeCN)](2+) (1), [Co(III)(S(Me2)N(4)(tren))(OH)](+) (3), [Co(III)(S(Me2)N(4)(tren))(NHC(O)CH(3))](+) (2), and [Co(III)(O(Me2)N(4)(tren))(NHC(OH)CH(3))](2+) (5). Iminol-bound 5 represents the first example of a Co(III)-iminol compound in any ligand environment. Kinetic parameters (k(1)(298 K) = 2.98(5) M(-1) s(-1), ΔH(‡) = 12.65(3) kcal/mol, ΔS(‡) = -14(7) e.u.) for nitrile hydration by 1 are reported, and the activation energy E(a) = 13.2 kcal/mol is compared with that (E(a) = 5.5 kcal/mol) of the NHase enzyme. A mechanism involving initial exchange of the bound MeCN for OH- is ruled out by the fact that nitrile exchange from 1 (k(ex)(300 K) = 7.3(1) × 10(-3) s(-1)) is 2 orders of magnitude slower than nitrile hydration, and that hydroxide bound 3 does not promote nitrile hydration. Reactivity of an analogue that incorporates an alkoxide as a mimic of the highly conserved NHase serine residue shows that this moiety facilitates nitrile hydration under milder conditions. Hydrogen-bonding to the alkoxide stabilizes a Co(III)-iminol intermediate. Comparison of the thiolate versus alkoxide intermediate structures shows that C≡N bond activation and C═O bond formation proceed further along the reaction coordinate when a thiolate is incorporated into the coordination sphere.

  6. Solvation dynamics through Raman spectroscopy: hydration of Br2 and Br3(-), and solvation of Br2 in liquid bromine.

    Science.gov (United States)

    Branigan, Edward T; Halberstadt, N; Apkarian, V A

    2011-05-07

    Raman spectroscopy of bromine in the liquid phase and in water illustrates uncommon principles and yields insights regarding hydration. In liquid Br(2), resonant excitation over the B((3)Π(0u)(+)) ← X((1)Σ(g)(+)) valence transition at 532 nm produces a weak resonant Raman (RR) progression accompanied by a five-fold stronger non-resonant (NR) scattering. The latter is assigned to pre-resonance with the C-state, which in turn must be strongly mixed with inter-molecular charge transfer states. Despite the electronic resonance, RR of Br(2) in water is quenched. At 532 nm, the homogeneously broadened fundamental is observed, as in the NR case at 785 nm. The implications of the quenching of RR scattering are analyzed in a simple, semi-quantitative model, to conclude that the inertial evolution of the Raman packet in aqueous Br(2) occurs along multiple equivalent water-Br(2) coordinates. In distinct contrast with hydrophilic hydration in small clusters and hydrophobic hydration in clathrates, it is concluded that the hydration shell of bromine in water consists of dynamically equivalent fluxional water molecules. At 405 nm, the RR progression of Br(3)(-) is observed, accompanied by difference transitions between the breathing of the hydration shell and the symmetric stretch of the ion. The RR scattering process in this case can be regarded as the coherent photo-induced electron transfer to the solvent and its radiative back-transfer.

  7. Snowball Earth termination by destabilization of equatorial permafrost methane clathrate.

    Science.gov (United States)

    Kennedy, Martin; Mrofka, David; von der Borch, Chris

    2008-05-29

    The start of the Ediacaran period is defined by one of the most severe climate change events recorded in Earth history--the recovery from the Marinoan 'snowball' ice age, approximately 635 Myr ago (ref. 1). Marinoan glacial-marine deposits occur at equatorial palaeolatitudes, and are sharply overlain by a thin interval of carbonate that preserves marine carbon and sulphur isotopic excursions of about -5 and +15 parts per thousand, respectively; these deposits are thought to record widespread oceanic carbonate precipitation during postglacial sea level rise. This abrupt transition records a climate system in profound disequilibrium and contrasts sharply with the cyclical stratigraphic signal imparted by the balanced feedbacks modulating Phanerozoic deglaciation. Hypotheses accounting for the abruptness of deglaciation include ice albedo feedback, deep-ocean out-gassing during post-glacial oceanic overturn or methane hydrate destabilization. Here we report the broadest range of oxygen isotope values yet measured in marine sediments (-25 per thousand to +12 per thousand) in methane seeps in Marinoan deglacial sediments underlying the cap carbonate. This range of values is likely to be the result of mixing between ice-sheet-derived meteoric waters and clathrate-derived fluids during the flushing and destabilization of a clathrate field by glacial meltwater. The equatorial palaeolatitude implies a highly volatile shelf permafrost pool that is an order of magnitude larger than that of the present day. A pool of this size could have provided a massive biogeochemical feedback capable of triggering deglaciation and accounting for the global postglacial marine carbon and sulphur isotopic excursions, abrupt unidirectional warming, cap carbonate deposition, and a marine oxygen crisis. Our findings suggest that methane released from low-latitude permafrost clathrates therefore acted as a trigger and/or strong positive feedback for deglaciation and warming. Methane hydrate

  8. Nitrile Hydration by Thiolate–and Alkoxide–Ligated Co-NHase Analogues. Isolation of Co(III)-Amidate and Co(III)–Iminol Intermediates

    Science.gov (United States)

    Swartz, Rodney D.; Coggins, Michael K.; Kaminsky, Werner; Kovacs, Julie A.

    2011-01-01

    Nitrile hydratases (NHases) are thiolate–ligated Fe(III)- or Co(III)-containing enzymes, which convert nitriles to the corresponding amide under mild conditions. Proposed NHase mechanisms involve M(III)–NCR, M(III)–OH, M(III)–iminol and M(III)–amide intermediates. Spectroscopic and kinetic data support the involvement of a M(III)–NCR intermediate. A H–bonding network facilitates this enzymatic reaction. There have been no reported crystallographically characterized examples of these key intermediates. Herein we describe two biomimetic Co(III)–NHase analogues that hydrate MeCN. Four key crystallographically characterized NHase intermediate anaologues, [CoIII(SMe2N4(tren))(MeCN)]2+ (1), [CoIII(SMe2N4(tren))(OH)]+ (3), [CoIII(SMe2N4(tren))(NHC(O)CH3)]+ (2), and [CoIII(OMe2N4(tren))(NHC(OH)CH3)]2+ (5) are described. Iminol–bound 5 represents the first example of a Co(III)-iminol compound in any ligand environment. Kinetic parameters (k1(298 K)= 2.98(5) M−1s−1, ΔH‡ = 12.65(3) kcal/mol, ΔS‡ = −14(7) e.u.) for nitrile hydration by 1 are reported, and the activation energy Ea= 13.2 kcal/mol is compared with that (Ea= 5.5 kcal/mol) of the NHase enzyme. A mechanism involving initial exchange of the bound MeCN for OH− is ruled out by the fact that nitrile exchange from 1 (kex(300 K)= 7.3(1) x10−3 s−1) is two orders of magnitude slower than nitrile hydration, and that hydroxide bound 3 does not promote nitrile hydration. Reactivity of an analogue that incorporates an alkoxide as a mimic of the highly conserved NHase serine residue shows that this moiety facilitates nitrile hydration under milder conditions. Hydrogen-bonding to the alkoxide stabilizes a Co(III)-iminol intermediate. Comparison of the thiolate versus alkoxide intermediate structures shows that C≡N bond activation and C=O bond formation proceed further along the reaction coordinate when a thiolate is incorporated into the coordination sphere. PMID:21351789

  9. CO2 solubility in aqueous solutions containing Na+, Ca2+, Cl−, SO42− and HCO3-: The effects of electrostricted water and ion hydration thermodynamics

    International Nuclear Information System (INIS)

    Gilbert, Kimberly; Bennett, Philip C.; Wolfe, Will; Zhang, Tongwei; Romanak, Katherine D.

    2016-01-01

    Dissolution of CO 2 into deep subsurface brines for carbon sequestration is regarded as one of the few viable means of reducing the amount of CO 2 entering the atmosphere. Ions in solution partially control the amount of CO 2 that dissolves, but the mechanisms of the ion's influence are not clearly understood and thus CO 2 solubility is difficult to predict. In this study, CO 2 solubility was experimentally determined in water, NaCl, CaCl 2 , Na 2 SO 4, and NaHCO 3 solutions and a mixed brine similar to the Bravo Dome natural CO 2 reservoir; ionic strengths ranged up to 3.4 molal, temperatures to 140 °C, and CO 2 pressures to 35.5 MPa. Increasing ionic strength decreased CO 2 solubility for all solutions when the salt type remained unchanged, but ionic strength was a poor predictor of CO 2 solubility in solutions with different salts. A new equation was developed to use ion hydration number to calculate the concentration of electrostricted water molecules in solution. Dissolved CO 2 was strongly correlated (R 2  = 0.96) to electrostricted water concentration. Strong correlations were also identified between CO 2 solubility and hydration enthalpy and hydration entropy. These linear correlation equations predicted CO 2 solubility within 1% of the Bravo Dome brine and within 10% of two mixed brines from literature (a 10 wt % NaCl + KCl + CaCl 2 brine and a natural Na + , Ca 2+ , Cl − type brine with minor amounts of Mg 2+ , K + , Sr 2+ and Br − ). - Highlights: • Measured CO 2 solubility in Na + , Cl − , HCO 3 - , Ca 2+ and SO 4 2− solutions at high PCO 2 . • A new equation calculates electrostricted water (mol/kgw) from hydration number. • CO 2 solubility strongly correlates (R 2  = 0.96) to electrostricted water. • Ion electrostriction of water limits its availability for CO 2 caging and solvation. • Correlations predict CO 2 solubility of several mixed brines to within 1–9%.

  10. Carbon-14 immobilization via the CO2-Ba(OH)2 hydrate gas-solid reaction

    International Nuclear Information System (INIS)

    Haag, G.L.

    1981-08-01

    For the treatment of an air-based off-gas stream, the use of packed beds of Ba(OH) 2 .8H 2 O flakes to remove CO 2 has been demonstrated. However, the operating conditions must be maintained between certain upper and lower limits with respect to the partial pressure of water. If the water vapor pressure in the gas is less than the dissociation vapor pressure of Ba(OH) 2 .8H 2 O, the bed will deactivate. If the vapor pressure is considerably greater, pressure drop problems will increase with increaseing humidity as the particles curl and degrade. Results have indicted that when operated in the proper regime, the bulk of the increase in pressure drop results from the conversion of Ba(OH) 2 .8H 2 O to BaCO 3 and not from the hydration of the commercial Ba(OH) 2 .8H 2 O (i.e., Ba(OH) 2 .7.50H 2 O) to Ba(OH) 2 .8H 2 O

  11. CH4 recovery and CO2 sequestration using flue gas in natural gas hydrates as revealed by a micro-differential scanning calorimeter

    International Nuclear Information System (INIS)

    Lee, Yohan; Kim, Yunju; Lee, Jaehyoung; Lee, Huen; Seo, Yongwon

    2015-01-01

    Highlights: • The extent of the replacement was improved due to the enclathration of N 2 in small cages. • The dissociation enthalpies of the replaced gas hydrates were measured. • There was no noticeable heat flow change during the CH 4 –flue gas replacement. • The replacement could occur without significant destruction of gas hydrates. - Abstract: The CH 4 –flue gas replacement in naturally occurring gas hydrates has attracted significant attention due to its potential as a method of exploitation of clean energy and sequestration of CO 2 . In the replacement process, the thermodynamic and structural properties of the mixed gas hydrates are critical factors to predict the heat flow in the hydrate-bearing sediments and the heat required for hydrate dissociation, and to evaluate the CO 2 storage capacity of hydrate reservoirs. In this study, the 13 C NMR and gas composition analyses confirmed that the preferential enclathration of N 2 molecules in small 5 12 cages of structure I hydrates improved the extent of the CH 4 recovery. A high pressure micro-differential scanning calorimeter (HP μ-DSC) provided reliable hydrate stability conditions and heat of dissociation values in the porous silica gels after the replacement, which confirmed that CH 4 in the hydrates was successfully replaced with flue gas. A heat flow change associated with the dissociation and formation of hydrates was not noticeable during the CH 4 –flue gas replacement. Therefore, this study reveals that CH 4 –flue gas swapping occurs without structural transitions and significant hydrate dissociations

  12. Inter-cage dynamics in structure I, II, and H fluoromethane hydrates as studied by NMR and molecular dynamics simulations

    International Nuclear Information System (INIS)

    Trueba, Alondra Torres; Kroon, Maaike C.; Peters, Cor J.; Moudrakovski, Igor L.; Ratcliffe, Christopher I.; Ripmeester, John A.; Alavi, Saman

    2014-01-01

    Prospective industrial applications of clathrate hydrates as materials for gas separation require further knowledge of cavity distortion, cavity selectivity, and defects induction by guest-host interactions. The results presented in this contribution show that under certain temperature conditions the guest combination of CH 3 F and a large polar molecule induces defects on the clathrate hydrate framework that allow intercage guest dynamics. 13 C NMR chemical shifts of a CH 3 F/CH 4 /TBME sH hydrate and a temperature analysis of the 2 H NMR powder lineshapes of a CD 3 F/THF sII and CD 3 F/TBME sH hydrate, displayed evidence that the populations of CH 4 and CH 3 F in the D and D ′ cages were in a state of rapid exchange. A hydrogen bonding analysis using molecular dynamics simulations on the TBME/CH 3 F and TBME/CH 4 sH hydrates showed that the presence of CH 3 F enhances the hydrogen bonding probability of the TBME molecule with the water molecules of the cavity. Similar results were obtained for THF/CH 3 F and THF/CH 4 sII hydrates. The enhanced hydrogen bond formation leads to the formation of defects in the water hydrogen bonding lattice and this can enhance the migration of CH 3 F molecules between adjacent small cages

  13. Methods of gas hydrate concentration estimation with field examples

    Digital Repository Service at National Institute of Oceanography (India)

    Kumar, D.; Dash, R.; Dewangan, P.

    physics and seismic inversion: examples from the northern deepwater Gulf of Mexico: The Leading Edge, 23, 60-66. Dash R., 2007, Crustal structure and marine gas hydrate studies near Vancouver Island using seismic tomography: PhD thesis, University...-resistivity logs: Examples from Green Canyon, Gulf of Mexico: SEG expanded abstracts, 26, 1579-1583. Singh, S. C., Minshull, T. A., and Spence, G. D., 1993, Velocity structure of a gas hydrate reflector: Science, 260, 204-207. Sloan, E. D. Jr., 1998, Clathrate...

  14. Description of gas hydrates equilibria in sediments using experimental data of soil water potential

    Energy Technology Data Exchange (ETDEWEB)

    Istomin, V. [NOVATEK, Moscow (Russian Federation); Chuvilin, E. [Moscow State Univ., Moscow (Russian Federation). Dept. of Geology; Makhonina, N.; Kvon, V. [VNIIGAZ, Moscow (Russian Federation); Safonov, S. [Schlumberger Moscow Research, Moscow (Russian Federation)

    2008-07-01

    Analytical relationships have been developed between hydrate dissociation pressure and vapor pressure above the pore water surface. In addition, experiments have been discussed in numerous publications on the effect of narrow interconnected throats between pores on clathrate dissociation conditions in porous media. This paper presented an approach that improved upon the available thermodynamic methods for calculation of hydrate phase equilibria. The approach took into account the properties of pore water in natural sediments including three-phase equilibrium of gas-pore water-gas hydrate in a similar way as for unfrozen water in geocryology science. The purpose of the paper was to apply and adapt geocryology and soil physics method to the thermodynamic calculation of non-clathrated water content in sediments. It answered the question of how to estimate the non-clathrated water content if pore water potential was known. The paper explained the thermodynamics of water phase in porous media including the thermodynamic properties of supercooled water, the thermodynamic properties of pore water and pore ice in sediments, and the phase equilibria of pore water. The paper also discussed the quantitative techniques that were utilized for determination of unfrozen water content in sediments and its dependence on temperature variation. These included contact-saturation, calorimetric, dielectric, nuclear magnetic resonance, and others. The thermodynamic calculations of pore water phase equilibria were also presented. 30 refs., 5 tabs., 8 figs.

  15. Computational Recreation of Carbon Dioxide Hydrates at Habitable Planetary Conditions

    Science.gov (United States)

    Recio, J. M.; Izquierdo-Ruiz, F.; Prieto-Ballesteros, O.

    2017-12-01

    Gas clathrate hydrates are proposed as constituents of the icy moons of the giant planets in the Solar System [1]. Carbon dioxide has been detected on the surface of the moons of Jupiter, supposedly originated by internal degasification. In Ganymede, an aqueous ocean is proposed to exist under a thick ice crust in coexistence with several forms of ice, with pressure reaching up to 1.3 GPa [2]. Due to the limited available data on these systems under these conditions, we propose a combination of computational and experimental studies to describe microscopically and macroscopically the structural and chemical behavior of CO2@H2O polymorphs. This will allow us to understand how their presence affects the geophysical structure and activity and their impact on the habitability of the icy moon. A transition from the sI cubic structure to a high pressure phase at around 0.7 GPa has been found for CO2@H2O. In spite of different attempts to characterize the new structure, a definite answer has not been provided yet. A MH-III Filled Ice Structure type was proposed after neutron diffraction experiments in contrast with an alternative structure similar to the hexagonal C0 type for H2 hydrates [3]. It has an estimated hydration level ratio up to 2H2O:1CO2 and 6 water molecules per unit cell. In the figure below, our optimized unit cell based on this hexagonal C0 structure is displayed. Ab initio calculations using the XDM approximation to include van der Waals effects are performed in our search for the pressure evolution of the equilibrium geometries of the C0-CO2@H2O phase and those of a close related structure to this one called Ih-C0, with 8 water molecules per unit cell. We obtain occupation energies at different hydration ratios, densities, equations of state parameters, and stability energies with respect to decomposition. Raman and IR frequencies are also computed in the 0-2 GPa range. High pressure experiments are also being done in a newly designed chamber able to

  16. Heat-pump cool storage in a clathrate of freon

    Science.gov (United States)

    Tomlinson, J. J.

    Presented are the analytical description and assessment of a unique heat pump/storage system in which the conventional evaporator of the vapor compression cycle is replaced by a highly efficient direct contract crystallizer. The thermal storage technique requires the formation of a refrigerant gas hydrate (a clathrate) and exploits an enthalpy of reaction comparable to the heat of fusion of ice. Additional system operational benefits include cool storage at the favorable temperatures of 4 to 7 C (40 to 45 F), and highly efficient heat transfer ates afforded by he direct contact mechanism. In addition, the experimental approach underway at ORNL to study such a system is discussed.

  17. Gas hydrate phase equilibria measurement techniques and phase rule considerations

    International Nuclear Information System (INIS)

    Beltran, Juan G.; Bruusgaard, Hallvard; Servio, Phillip

    2012-01-01

    Highlights: → Inconsistencies found in hydrate literature. → Clarification to the number of variables needed to satisfy and justify equilibrium data. → Application of phase rule to mixed hydrate systems. → Thermodynamically consistent format to present data. - Abstract: A brief review of the Gibbs phase rule for non-reacting systems and its correct application to clathrate hydrates is presented. Clarification is provided for a common mistake found in hydrate phase-equilibria literature, whereby initial compositions are used as intensive variables to satisfy the Gibbs phase rule instead of the equilibrium values. The system of (methane + carbon dioxide + water) under (hydrate + liquid + vapor) equilibrium is used as a case study to illustrate key points and suggestions to improve experimental techniques are proposed.

  18. High-temperature CO2 capture cycles of hydrated limestone prepared with aluminum (hydr)oxides derived from kaolin

    International Nuclear Information System (INIS)

    Wang, Ke; Zhao, Pengfei; Guo, Xin; Han, Dongtai; Chao, Yang

    2014-01-01

    Highlights: • Hydrated limestone exhibited a higher reactivity and stability. • Microstructure of hydrated limestone was significantly improved. • Hydrated limestone still suffered less loss-incapacity. • Hydrated limestone sorbents with kaolin-based binders were prepared and characterized. • Sorbents prepared from hydrated limestone and Al(OH) 3 binder are a promising sorbent. - Abstract: A simple and convenient process was used to improve the utilization of natural limestone and kaolin for calcium looping technology and environmental applications. The calcined natural limestone modified with the distilled water (denoted as Limestone-W), was systematically studied and compared with the other CaO sorbents (calcium acetate, calcium D-gluconate and calcined natural limestone). These CaO-based sorbents were tested for their CO 2 capture behavior through 20 carbonation/calcination cycles in a thermo-gravimetric analyzer (TGA). Their morphology, pore structure and phase composition before and after carbonation/calcination cycles were determined by scanning electron microscopy, nitrogen adsorption, and X-ray diffraction. The first-cycle and multicycle sorption results revealed that the Limestone-W sorbent exhibited a relatively faster reaction rate and higher cyclic CO 2 capture. The characterization data indicated that the Limestone-W was composed of a special calcium oxide structure with lower crystalline and higher porosity nanoparticles, which appeared to be the main reasons for its higher CO 2 capture capability. However, the Limestone-W still suffered loss of reactivity, even though it was less pronounced than the other CaO sorbent. To avoid this unfavorable effect, a thermally stable inert material (aluminum hydroxide derived from kaolin) was incorporated into the Limestone-W structure. This new sorbent revealed higher stability because the formation of a stable framework of Ca 12 Al 14 O 33 particles hindered densification and sintering of the CaO phase

  19. Unexpected inhibition of CO2 gas hydrate formation in dilute TBAB solutions and the critical role of interfacial water structure

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Ngoc N.; Nguyen, Anh V.; Nguyen, Khoi T.; Rintoul, Llew; Dang, Liem X.

    2016-12-01

    Gas hydrates formed under moderated conditions open up novel approaches to tackling issues related to energy supply, gas separation, and CO2 sequestration. Several additives like tetra-n-butylammonium bromide (TBAB) have been empirically developed and used to promote gas hydrate formation. Here we report unexpected experimental results which show that TBAB inhibits CO2 gas hydrate formation when used at minuscule concentration. We also used spectroscopic techniques and molecular dynamics simulation to gain further insights and explain the experimental results. They have revealed the critical role of water alignment at the gas-water interface induced by surface adsorption of tetra-n-butylammonium cation (TBA+) which gives rise to the unexpected inhibition of dilute TBAB solution. The water perturbation by TBA+ in the bulk is attributed to the promotion effect of high TBAB concentration on gas hydrate formation. We explain our finding using the concept of activation energy of gas hydrate formation. Our results provide a step toward to mastering the control of gas hydrate formation.

  20. Investigation of Wyoming Bentonite Hydration in Dry to Water-Saturated Supercritical CO2: Implications for Caprock Integrity

    Science.gov (United States)

    Loring, J. S.; Chen, J.; Thompson, C.; Schaef, T.; Miller, Q. R.; Martin, P. F.; Ilton, E. S.; Qafoku, O.; Felmy, A. R.; Rosso, K. M.

    2012-12-01

    The effectiveness of geologic sequestration as an enterprise for CO2 storage depends partly on the reactivity of supercritical CO2 (scCO2) with caprock minerals. Injection of scCO2 will displace formation water, and the pore space adjacent to overlying caprocks could eventually be dominated by dry to water-saturated scCO2. Caprock formations have high concentrations of clay minerals, including expandable montmorillonites. Water-bearing scCO2 is highly reactive and capable of hydrating or dehydrating clays, possibly leading to porosity and permeability changes that directly impact caprock performance. Dehydration will cause montmorillonite clay minerals in caprocks to contract, thereby decreasing solid volume and possibly increasing caprock permeability and porosity. On the other hand, water intercalation will cause these clays to expand, thereby increasing solid volume and possibly leading to self-sealing of caprock fractures. Pacific Northwest National Laboratory's Carbon Sequestration Initiative is developing capabilities for studying wet scCO2-mineral reactions in situ. Here, we introduce novel in situ infrared (IR) spectroscopic instrumentation that enables quantitative titrations of reactant minerals with water in scCO2. Results are presented for the infrared spectroscopic titrations of Na-, Ca-, and Mg-saturated Wyoming betonites with water over concentrations ranging from zero to scCO2 saturated. These experiments were carried out at 50°C and 90 bar. Transmission IR spectroscopy was used to measure concentrations of water dissolved in the scCO2 or intercalated into the clays. The titration curves evaluated from the transmission-IR data are compared between the three types of clays to assess the effects of the cation on water partitioning. Single-reflection attenuated total reflection (ATR) IR spectroscopy was used to collect the spectrum of the clays as they hydrate at every total water concentration during the titration. Clay hydration is evidenced by

  1. Cyclodextrin-Based Solid-Gas Clathrates

    NARCIS (Netherlands)

    Pereva, Stiliana; Himitliiska, Tsveta; Spassov, Tony; Stoyanov, S.D.; Arnaudov, L.N.; Dudev, Todor

    2015-01-01

    "Cyclodextrin-gas" clathrates were obtained by crystallization from water solution of α-, β-, and γ-cyclodextrins (CDs) under pressure of the gas to be entrapped into the CD molecules. When the pressure is released, these clathrates are stable at ambient conditions and dissociate at elevated

  2. Mineral-like clathrate of cadmium cyanide with benzene

    International Nuclear Information System (INIS)

    Kitazava, T.; Nishimura, A.

    1999-01-01

    A new mineral-like clathrate of cadmium cyanide with benzene Cd(CN) 2 ·C 6 H 6 is prepared. Data of x-ray diffraction analysis show that benzene molecule is incorporated in cadmium cyanide lattice and a new mineral-like lattice of Cd(CN) 2 belongs to structures of cristobalite type. Clathrate Cd(CN) 2 ·C 6 H 6 crystallizes in trigonal space group R3m, a=8.953(4), c=21929(6) A [ru

  3. The Iġnik Sikumi Field Experiment, Alaska North Slope: Design, operations, and implications for CO2−CH4 exchange in gas hydrate reservoirs

    Science.gov (United States)

    Boswell, Ray; Schoderbek, David; Collett, Timothy S.; Ohtsuki, Satoshi; White, Mark; Anderson, Brian J.

    2017-01-01

    The Iġnik Sikumi Gas Hydrate Exchange Field Experiment was conducted by ConocoPhillips in partnership with the U.S. Department of Energy, the Japan Oil, Gas and Metals National Corporation, and the U.S. Geological Survey within the Prudhoe Bay Unit on the Alaska North Slope during 2011 and 2012. The primary goals of the program were to (1) determine the feasibility of gas injection into hydrate-bearing sand reservoirs and (2) observe reservoir response upon subsequent flowback in order to assess the potential for CO2 exchange for CH4 in naturally occurring gas hydrate reservoirs. Initial modeling determined that no feasible means of injection of pure CO2 was likely, given the presence of free water in the reservoir. Laboratory and numerical modeling studies indicated that the injection of a mixture of CO2 and N2 offered the best potential for gas injection and exchange. The test featured the following primary operational phases: (1) injection of a gaseous phase mixture of CO2, N2, and chemical tracers; (2) flowback conducted at downhole pressures above the stability threshold for native CH4 hydrate; and (3) an extended (30-days) flowback at pressures near, and then below, the stability threshold of native CH4 hydrate. The test findings indicate that the formation of a range of mixed-gas hydrates resulted in a net exchange of CO2 for CH4 in the reservoir, although the complexity of the subsurface environment renders the nature, extent, and efficiency of the exchange reaction uncertain. The next steps in the evaluation of exchange technology should feature multiple well applications; however, such field test programs will require extensive preparatory experimental and numerical modeling studies and will likely be a secondary priority to further field testing of production through depressurization. Additional insights gained from the field program include the following: (1) gas hydrate destabilization is self-limiting, dispelling any notion of the potential for

  4. Hydro-geomechanical behaviour of gas-hydrate bearing soils during gas production through depressurization and CO2 injection

    Science.gov (United States)

    Deusner, C.; Gupta, S.; Kossel, E.; Bigalke, N.; Haeckel, M.

    2015-12-01

    Results from recent field trials suggest that natural gas could be produced from marine gas hydrate reservoirs at compatible yields and rates. It appears, from a current perspective, that gas production would essentially be based on depressurization and, when facing suitable conditions, be assisted by local thermal stimulation or gas hydrate conversion after injection of CO2-rich fluids. Both field trials, onshore in the Alaska permafrost and in the Nankai Trough offshore Japan, were accompanied by different technical issues, the most striking problems resulting from un-predicted geomechanical behaviour, sediment destabilization and catastrophic sand production. So far, there is a lack of experimental data which could help to understand relevant mechanisms and triggers for potential soil failure in gas hydrate production, to guide model development for simulation of soil behaviour in large-scale production, and to identify processes which drive or, further, mitigate sand production. We use high-pressure flow-through systems in combination with different online and in situ monitoring tools (e.g. Raman microscopy, MRI) to simulate relevant gas hydrate production scenarios. Key components for soil mechanical studies are triaxial systems with ERT (Electric resistivity tomography) and high-resolution local strain analysis. Sand production control and management is studied in a novel hollow-cylinder-type triaxial setup with a miniaturized borehole which allows fluid and particle transport at different fluid injection and flow conditions. Further, the development of a large-scale high-pressure flow-through triaxial test system equipped with μ-CT is ongoing. We will present results from high-pressure flow-through experiments on gas production through depressurization and injection of CO2-rich fluids. Experimental data are used to develop and parametrize numerical models which can simulate coupled process dynamics during gas-hydrate formation and gas production.

  5. Considering multiple occupancy of cavities in clathrate hydrate phase equilibrium calculations

    Energy Technology Data Exchange (ETDEWEB)

    Asiaee, Alireza; Raeissi, Sona [Natural Gas Engineering Department, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz 71345 (Iran, Islamic Republic of); Shariati, Alireza, E-mail: shariati@shirazu.ac.i [Natural Gas Engineering Department, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz 71345 (Iran, Islamic Republic of)

    2011-05-15

    Research highlights: A model is presented to predict dissociation pressures of gas hydrates at various temperatures. The present model is applicable on a wide range of equilibrium conditions. The simple calculation procedure presented here saves considerably the calculation time. - Abstract: One of the major assumptions of the original van der Waals-Platteeuw (vdWP) model is the single occupancy of hydrate cavities. In this work, the vdWP model is modified to also account for multiple occupancies of hydrate cavities by small molecules. The developed model is evaluated by calculating the hydrate equilibrium conditions with either oxygen or nitrogen as guest molecules in pure form, as well as mixtures of nitrogen and propane (molecules of these pure gases and those in (nitrogen + propane) have double occupancy in large cavities of structure II up to a certain concentration of propane). The results of this modified model show good agreement with the experimental data reported in the literature.

  6. Considering multiple occupancy of cavities in clathrate hydrate phase equilibrium calculations

    International Nuclear Information System (INIS)

    Asiaee, Alireza; Raeissi, Sona; Shariati, Alireza

    2011-01-01

    Research highlights: → A model is presented to predict dissociation pressures of gas hydrates at various temperatures. → The present model is applicable on a wide range of equilibrium conditions. → The simple calculation procedure presented here saves considerably the calculation time. - Abstract: One of the major assumptions of the original van der Waals-Platteeuw (vdWP) model is the single occupancy of hydrate cavities. In this work, the vdWP model is modified to also account for multiple occupancies of hydrate cavities by small molecules. The developed model is evaluated by calculating the hydrate equilibrium conditions with either oxygen or nitrogen as guest molecules in pure form, as well as mixtures of nitrogen and propane (molecules of these pure gases and those in (nitrogen + propane) have double occupancy in large cavities of structure II up to a certain concentration of propane). The results of this modified model show good agreement with the experimental data reported in the literature.

  7. Kinetics of the reaction of hydrated lime with SO{sub 2} at low temperatures: effects of the presence of CO{sub 2}, O{sub 2}, and NOx

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.F.; Shih, S.M. [National Taiwan University, Taipei (Taiwan). Dept. of Chemical Engineering

    2008-12-15

    The effects of the presence Of CO{sub 2}, O{sub 2}, and NOx in the flue gas on the kinetics of the sulfation of hydrated lime at low temperatures were studied using a differential fixed-bed reactor. When O{sub 2} and NOx were not present together the reaction kinetics was about the same as that under gas mixtures containing SO{sub 2}, H{sub 2}O, and N2 only. When both O{sub 2} and NOx were present, sulfation of hydrated lime was greatly enhanced, forming a large amount of calcium sulfate in addition to calcium sulfite. Sulfation of hydrated lime was well described by the surface coverage model, despite the gas-phase conditions being different. Relative humidity is the major factor affecting the reaction, and its effect was more marked when both O{sub 2} and NOx were present. The kinetic model equations obtained in this work can be used to describe the sulfation of hydrated lime in the low-temperature dry and semidry flue gas desulfurization processes with or without an upstream NOx removal unit.

  8. Low temperature X-ray diffraction studies of natural gas hydrate samples from the Gulf of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Rawn, C.J. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Materials Science and Technology Div.; Sassen, R. [Texas A and M Univ., College Station, TX (United States). Geochemical and Environmental Research Group; Ulrich, S.M.; Phelps, T.J. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Biosciences Div.; Chakoumakos, B.C. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Neutron Scattering Science Div.; Payzant, E.A. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Center for Nanophase Materials Science

    2008-07-01

    Quantitative studies of natural clathrate hydrates are hampered by the difficulties associated with obtaining pristine samples for the sea floor without comprising their integrity. This paper discussed X-ray power diffraction studies conducted to measure natural gas hydrate samples obtained from the Green Canyon in the Gulf of Mexico. Data on the hydrate deposits were initially collected in 2002. The X-ray diffraction data were collected in order to examine the structure 2 (s2) gas hydrates as functions of temperature and time. A diffractometer with a theta-theta goniometer modified with a helium closed cycle refrigerator and temperature controller was used. Aragonite, quartz and halite phases were determined in the decomposed sample. Refined phase fractions for both the ice and the s2 hydrate were obtained as a function of temperature. Results of the study demonstrated that the amount of hydrates decreased with increasing temperatures and amounts of time. Large pieces of the hydrate showed heterogenous ice content. Dissociation rates were higher at lower temperatures. It was concluded that unusual trends observed for the smaller lattice parameter of the hydrates resulted from the formation of ice layers that acted as barriers to the released gases and caused increased isostatic pressures around the hydrate core. 9 refs., 6 figs.

  9. Capillary pressure controlled methane hydrate and ice growth-melting patterns in porous media : synthetic silica versus natural sandstone

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, R.; Tohidi, B.; Webber, B. [Heriot-Watt Univ., Centre for Gas Research, Edinburgh (United Kingdom). Inst. of Petroleum Engineering

    2008-07-01

    Although naturally-occurring gas hydrates (or clathrate hydrates) in marine sediments can pose a hazard to deepwater hydrocarbon production operations, they represent a potential strategic energy reserve. Gas hydrates can also provide a means for deep ocean carbon dioxide disposal through sequestration/storage. They have long-term importance with respect to ocean margin stability, methane release, and global climate change. However, fundamental knowledge is still lacking regarding the mechanisms of hydrate growth, accumulation and distribution within the subsurface. Marine sediments which host gas hydrates are commonly fine-grained silts, muds, and clays with narrow mean pore diameters, leading to speculation that capillary phenomena could play a significant role in controlling hydrate distribution in the seafloor, and may be partly responsible for discrepancies between observed and predicted hydrate stability zone thicknesses. A close relationship between hydrate inhibition and pore size has been confirmed through previous laboratory studies. Clathrate stability has been significantly reduced in narrow pores. However, the focus of investigations has generally been hydrate dissociation conditions in porous media, with capillary controls on the equally important process of hydrate growth being largely overlooked. This paper presented the results of an experimental investigation into methane hydrate growth and dissociation equilibria in natural medium grained sandstone. The study also compared data with that previously measured for mesoporous silica glasses. The paper discussed solid-liquid phase behaviour in confined geometries including hysteresis in porous media. It also discussed the experimental equipment and method. It was concluded that, as for synthetic silicas, hydrate growth and dissociation in the sandstone were characterised by a measurable hysteresis between opposing transitions, notably hydrate (or ice) formation occurring at temperatures lower than

  10. The genetic source and timing of hydrocarbon formation in gas hydrate reservoirs in Green Canyon, Block GC955

    Science.gov (United States)

    Moore, M. T.; Darrah, T.; Cook, A.; Sawyer, D.; Phillips, S.; Whyte, C. J.; Lary, B. A.

    2017-12-01

    Although large volumes of gas hydrates are known to exist along continental slopes and below permafrost, their role in the energy sector and the global carbon cycle remains uncertain. Investigations regarding the genetic source(s) (i.e., biogenic, thermogenic, mixed sources of hydrocarbon gases), the location of hydrocarbon generation, (whether hydrocarbons formed within the current reservoir formations or underwent migration), rates of clathrate formation, and the timing of natural gas formation/accumulation within clathrates are vital to evaluate economic potential and enhance our understanding of geologic processes. Previous studies addressed some of these questions through analysis of conventional hydrocarbon molecular (C1/C2+) and stable isotopic (e.g., δ13C-CH4, δ2H-CH4, δ13C-CO2) composition of gases, water chemistry and isotopes (e.g., major and trace elements, δ2H-H2O, δ18O-H2O), and dissolved inorganic carbon (δ13C-DIC) of natural gas hydrate systems to determine proportions of biogenic and thermogenic gas. However, the effects from contributions of mixing, transport/migration, methanogenesis, and oxidation in the subsurface can complicate the first-order application of these techniques. Because the original noble gas composition of a fluid is preserved independent of microbial activity, chemical reactions, or changes in oxygen fugacity, the integration of noble gas data can provide both a geochemical fingerprint for sources of fluids and an additional insight as to the uncertainty between effects of mixing versus post-genetic modification. Here, we integrate inert noble gases (He, Ne, Ar, and associated isotopes) with these conventional approaches to better constrain the source of gas hydrate formation and the residence time of fluids (porewaters and natural gases) using radiogenic 4He ingrowth techniques in cores from two boreholes collected as part of the University of Texas led UT-GOM2-01 drilling project. Pressurized cores were extracted from

  11. Dissolution mechanisms of CO2 hydrate droplets in deep seawaters

    International Nuclear Information System (INIS)

    Gabitto, Jorge; Tsouris, Costas

    2006-01-01

    Carbon dioxide dissolution at intermediate ocean depths was studied using physical and mass transfer models. Particle density and hydrate layer thickness were determined using existing field data. Pseudo-homogeneous and heterogeneous mass transfer models were proposed to study the dissolution process. Pseudo-homogeneous models do not seem to represent the dissolution process well. Although heterogeneous models interpret the physical behavior better, unresolved issues related to hydrate dissolution still remain. For example, solid hydrate forms on one side of the hydrate film while it dissolves on the other. Dissolution is a complex process that comprises at least two sequential steps. The global process is controlled by mass transfer inside the hydrate layer or by a dissolution reaction at the hydrate-water interface

  12. Thermodynamic Stability of Structure H Hydrates Based on the Molecular Properties of Large Guest Molecules

    OpenAIRE

    Tezuka, Kyoichi; Taguchi, Tatsuhiko; Alavi, Saman; Sum, Amadeu K.; Ohmura, Ryo

    2012-01-01

    This paper report analyses of thermodynamic stability of structure-H clathrate hydrates formed with methane and large guest molecules in terms of their gas phase molecular sizes and molar masses for the selection of a large guest molecule providing better hydrate stability. We investigated the correlation among the gas phase molecular sizes, the molar masses of large molecule guest substances, and the equilibrium pressures. The results suggest that there exists a molecular-size value for the ...

  13. Kinetic studies of methane-ethane mixed gas hydrates by neutron diffraction and Raman spectroscopy.

    Science.gov (United States)

    Murshed, M Mangir; Kuhs, Werner F

    2009-04-16

    In situ formations of CH(4)-C(2)H(6) mixed gas hydrates were made using high flux neutron diffraction at 270 K and 5 MPa. For this purpose, a feed gas composition of CH(4) and C(2)H(6) (95 mol% CH(4)) was employed. The rates of transformation of spherical grains of deuterated ice Ih into hydrates were measured by time-resolved neutron powder diffraction on D20 at ILL, Grenoble. Phase fractions of the crystalline constituents were obtained from Rietveld refinements. A concomitant formation of structure type I (sI) and structure type II (sII) hydrates were observed soon after the gas pressure was applied. The initial fast formation of sII hydrate reached its maximum volume and started declining very slowly. The formation of sI hydrate followed a sigmoid growth kinetics that slowed down due to diffusion limitation. This observation has been interpreted in terms of a kinetically favored nucleation of the sII hydrate along with a slow transformation into sI. Both powder diffraction and Raman spectroscopic results suggest that a C(2)H(6)-rich sII hydrate was formed at the early part of the clathration, which slowly decreased to approximately 3% after a reaction of 158 days as confirmed by synchrotron XRD. The final persistence of a small portion of sII hydrate points to a miscibility gap between CH(4)-rich sI and C(2)H(6)-rich sII hydrates.

  14. Tracking all-vapor instant gas-hydrate formation and guest molecule populations: A possible probe for molecules trapped in water nanodroplets

    Czech Academy of Sciences Publication Activity Database

    Uras-Aytemiz, N.; Cwiklik, Lukasz; Devlin, J. P.

    2012-01-01

    Roč. 137, č. 20 (2012), s. 204501 ISSN 0021-9606 Institutional support: RVO:61388955 Keywords : Fourier transform infrared emission spectra * clathrate hydrate * simulations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.164, year: 2012

  15. Bi[NC5H3(CO2)2](OH2)xF (x=1 and 2): New one-dimensional Bi-coordination materials—Reversible hydration and topotactic decomposition to α-Bi2O3

    International Nuclear Information System (INIS)

    Jeon, Hye Rim; Lee, Dong Woo; Ok, Kang Min

    2012-01-01

    Two one-dimensional bismuth-coordination materials, Bi[NC 5 H 3 (CO 2 ) 2 ](OH 2 ) x F (x=1 and 2), have been synthesized by hydrothermal reactions using Bi 2 O 3 , 2,6-NC 5 H 3 (CO 2 H) 2 , HF, and water at 180 °C. Structures of the two materials were determined by single-crystal X-ray diffraction. Although they have different crystal structures, both Bi-organic materials shared a common structural motif, a one-dimensional chain structure consisting of Bi 3+ cations and pyridine dicarboxylate linkers. Detailed structural analyses include infrared spectroscopy, thermogravimetric analysis, and reversible hydration reactions for the coordinated water molecules were reported. Also, thermal decomposition of the rod-shaped Bi[NC 5 H 3 (CO 2 ) 2 ](OH 2 )F single crystals at 800 °C led to α-Bi 2 O 3 that maintained the same morphology of the original crystals. - Graphical abstract: Calcination of the Bi[NC 5 H 3 (CO 2 ) 2 ](OH 2 )F single crystals at 800 °C results in the α-Bi 2 O 3 rods that maintain the original morphology of the crystals. Highlights: ► Synthesis of one-dimensional chain Bi-organic frameworks. ► Reversible hydration reactions of Bi[NC 5 H 3 (CO 2 ) 2 ](OH 2 )F. ► Topotactic decomposition maintaining the same morphology of the original crystals.

  16. FTIR spectroscopic study on the Hofmann -Td- type clathrates: Ni(benzoic acid)2M(CN)4.aniline (M=Zn, Cd, Hg)

    International Nuclear Information System (INIS)

    Kesan, G.; Kartal, Z.

    2010-01-01

    The Hofmann-Td-type clathrates formulated as Ni(L) 2 M(CN) 4 .nG where L is a bidentate or a pair of unidentate ligand molecule, M is Zn, Cd or Hg, G is a guest molecule and n is the number of guest molecule. The host lattice of the Hofmann-Td-type clathrates is formed from endless chains of -Ni-L-L-Ni-L-L-Ni- and M(CN) 4 ions arranged between the consecutive crossing -Ni-L-L-Ni-L-L-Ni- chains with the O-ends bound to the Ni metal atoms. These polymeric layers are held in parallel by Van der Walls interaction between ligand molecules. This structure provides α-type cavity. In this study, Ni(Benzoic Acid ) 2M(CN) 4 .Aniline (M = Zn, Cd, Hg) is obtained for the first time by means of chemical methods in powder form and their infrared spectra are reported in range of (4000-400) cm - 1. The spectral data suggest that the new clathrates are similar in structure to the Hofmann-type clathrates.

  17. Kinetics of methane-ethane gas replacement in clathrate-hydrates studied by time-resolved neutron diffraction and Raman spectroscopy.

    Science.gov (United States)

    Murshed, M Mangir; Schmidt, Burkhard C; Kuhs, Werner F

    2010-01-14

    The kinetics of CH(4)-C(2)H(6) replacement in gas hydrates has been studied by in situ neutron diffraction and Raman spectroscopy. Deuterated ethane structure type I (C(2)H(6) sI) hydrates were transformed in a closed volume into methane-ethane mixed structure type II (CH(4)-C(2)H(6) sII) hydrates at 5 MPa and various temperatures in the vicinity of 0 degrees C while followed by time-resolved neutron powder diffraction on D20 at ILL, Grenoble. The role of available surface area of the sI starting material on the formation kinetics of sII hydrates was studied. Ex situ Raman spectroscopic investigations were carried out to crosscheck the gas composition and the distribution of the gas species over the cages as a function of structure type and compared to the in situ neutron results. Raman micromapping on single hydrate grains showed compositional and structural gradients between the surface and core of the transformed hydrates. Moreover, the observed methane-ethane ratio is very far from the one expected for a formation from a constantly equilibrated gas phase. The results also prove that gas replacement in CH(4)-C(2)H(6) hydrates is a regrowth process involving the nucleation of new crystallites commencing at the surface of the parent C(2)H(6) sI hydrate with a progressively shrinking core of unreacted material. The time-resolved neutron diffraction results clearly indicate an increasing diffusion limitation of the exchange process. This diffusion limitation leads to a progressive slowing down of the exchange reaction and is likely to be responsible for the incomplete exchange of the gases.

  18. Modeling the methane hydrate formation in an aqueous film submitted to steady cooling

    Energy Technology Data Exchange (ETDEWEB)

    Avendano-Gomez, J.R. [ESIQIE, Laboratorio de Ingenieria Quimica Ambiental, Mexico (Mexico). Inst. Politecnico Nacional; Garcia-Sanchez, F. [Laboratorio de Termodinamica, Mexico (Mexico). Inst. Mexicano del Petroleo; Gurrola, D.V. [UPIBI, Laboratorio de Diseno de Plantas, Mexico (Mexico). Inst. Politecnico Nacional

    2008-07-01

    Gas hydrates, or clathrate hydrates, are ice-like compounds that results from the kinetic process of crystallization of an aqueous solution supersaturated with a dissolved gas. This paper presented a model that took into account two factors involved in the hydrate crystallization, notably the stochastic nature of crystallization that causes sub-cooling and the heat resulting from the exothermic enthalpy of hydrate formation. The purpose of this study was to model the thermal evolution inside a hydrate forming system which was submitted to an imposed steady cooling. The study system was a cylindrical thin film of aqueous solution at 19 Mpa. The study involved using methane as the hydrate forming molecule. It was assumed that methane was homogeneously dissolved in the aqueous phase. Ethane hydrate was formed through a kinetic process of nucleation and crystallization. In order to predict the onset time of nucleation, the induction time needed to be considered. This paper discussed the probability of nucleation as well as the estimation of the rate of nucleation. It also presented the mathematical model and boundary conditions. These included assumptions and derivation of the model; boundary conditions; initial conditions; and numerical solution of the model equation. It was concluded that the heat source must be considered when investigating crystallization effects. 34 refs., 2 tabs., 2 figs.

  19. Mechanisms Leading to Co-Existence of Gas Hydrate in Ocean Sediments [Part 2 of 2

    Energy Technology Data Exchange (ETDEWEB)

    Bryant, Steven; Juanes, Ruben

    2011-12-31

    In this project we have sought to explain the co-existence of gas and hydrate phases in sediments within the gas hydrate stability zone. We have focused on the gas/brine interface at the scale of individual grains in the sediment. The capillary forces associated with a gas/brine interface play a dominant role in many processes that occur in the pores of sediments and sedimentary rocks. The mechanical forces associated with the same interface can lead to fracture initiation and propagation in hydrate-bearing sediments. Thus the unifying theme of the research reported here is that pore scale phenomena are key to understanding large scale phenomena in hydrate-bearing sediments whenever a free gas phase is present. Our analysis of pore-scale phenomena in this project has delineated three regimes that govern processes in which the gas phase pressure is increasing: fracturing, capillary fingering and viscous fingering. These regimes are characterized by different morphology of the region invaded by the gas. On the other hand when the gas phase pressure is decreasing, the corresponding regimes are capillary fingering and compaction. In this project, we studied all these regimes except compaction. Many processes of interest in hydrate-bearing sediments can be better understood when placed in the context of the appropriate regime. For example, hydrate formation in sub-permafrost sediments falls in the capillary fingering regime, whereas gas invasion into ocean sediments is likely to fall into the fracturing regime. Our research provides insight into the mechanisms by which gas reservoirs are converted to hydrate as the base of the gas hydrate stability zone descends through the reservoir. If the reservoir was no longer being charged, then variation in grain size distribution within the reservoir explain hydrate saturation profiles such as that at Mt. Elbert, where sand-rich intervals containing little hydrate are interspersed between intervals containing large hydrate

  20. Mechanism of the thermal conductivity of type-I clathrates

    International Nuclear Information System (INIS)

    Ikeda, M. S.

    2015-01-01

    Due to their intrinsically low thermal conductivity, intermetallic type-I clathrates are promising candidates for thermoelectric energy conversion, most notably for waste-heat recovery above room temperature. Combining their low thermal conductivity with the enhanced electrical power factor of strongly correlated materials can be considered as one of the most promising routes to a next generation thermoelectric material. However, although much investigated, the physical origin of the low thermal conductivity of type-I clathrates is still debated. Therefore, the main goal of this thesis was to gain deeper insight into the mechanism of the low thermal conductivity of type-I clathrates. On the basis of recent inelastic neutron and X-ray scattering studies on type-I clathrates and skutterudites, an analytical model for describing the phonon thermal conductivity of such filled cage compounds was developed within this thesis. This model is based on the phononic filter effect and on strongly enhanced Umklapp scattering. Data on several Ge-based single crystalline type-I clathrates are discussed in the context of this model, revealing the influence of host framework vacancies, charge carriers, and large defects such as grain boundaries on the low-temperature thermal conductivity of type-I clathrates. Since for waste heat recovery the thermal conductivity at elevated temperatures is of interest, a sophisticated 3w-experiment for accurate measurements of bulk and thin film materials at elevated temperatures was developed. With the help of this experiment, a universal dependence of the intrinsic phonon thermal conductivity of type-I clathrates on the sound velocity and the lowest-lying guest Einstein mode was demonstrated for the first time. Further investigations on thermoelectric materials including the first Ce-containing type-I clathrate, skutterudites, and thin films complete this doctoral work. (author)

  1. Carbon dioxide gas hydrates accumulation in freezing and frozen sediments

    Energy Technology Data Exchange (ETDEWEB)

    Chuvilin, E.; Guryeva, O. [Moscow State Univ., Moscow (Russian Federation). Dept. of Geology

    2008-07-01

    Carbon dioxide (CO{sub 2}) hydrates and methane hydrates can be formed, and exist under natural conditions. The permafrost area has been considered as an environment for the potential disposal of CO{sub 2}. The favorable factors for preserving CO{sub 2} in liquid and gas hydrate states in frozen sediments and under permafrost horizons are great thickness of frozen sediments; low permeability in comparison with thawed sediments; and favourable conditions for hydrates formation. Therefore, research on the formation and existence conditions of CO{sub 2} gas hydrates in permafrost and under permafrost sediments are of great importance for estimation of CO{sub 2} disposal conditions in permafrost, and for working out specific sequestration schemes. This paper presented the results of an experimental study on the process of carbon dioxide (CO{sub 2}) gas hydrates formation in the porous media of sediments under positive and negative temperatures. Sediment samples of various compositions including those selected in the permafrost area were used. The research was conducted in a special pressure chamber, which allowed to monitor pressure and temperature. The study used the monitoring results in order to make quantitative estimation of the kinetics of CO{sub 2} hydrates accumulation in the model sediments. Results were presented in terms of kinetics of CO{sub 2} hydrates accumulation in the porous media at positive and negative temperatures; kinetics of CO{sub 2} hydrates accumulation in various porous media; gas hydrate-former influence on kinetics of hydrates accumulation in frozen sediments; and influence of freezing on CO{sub 2} hydrates accumulation in porous media. It was concluded that hydrate accumulation took an active place in porous media not only under positive, but also under high negative temperatures, when the water was mainly in the form of ice in porous media. 27 refs., 3 tabs., 5 figs.

  2. Thermoelectric properties of low-dimensional clathrates from first principles

    Science.gov (United States)

    Kasinathan, Deepa; Rosner, Helge

    2011-03-01

    Type-I inorganic clathrates are host-guest structures with the guest atoms trapped in the framework of the host structure. From a thermoelectric point of view, they are interesting because they are semiconductors with adjustable bandgaps. Investigations in the past decade have shown that type-I clathrates X8 Ga 16 Ge 30 (X = Ba, Sr, Eu) may have the unusual property of ``phonon glass-electron crystal'' for good thermoelectric materials. Among the known clathrates, Ba 8 Ga 16 Ge 30 has the highest figure of merit (ZT~1). To enable a more widespread usage of thermoelectric technology power generation and heating/cooling applications, ZT of at least 2-3 is required. Two different research approaches have been proposed for developing next generation thermoelectric materials: one investigating new families of advanced bulk materials, and the other studying low-dimensional materials. In our work, we concentrate on understanding the thermoelectric properties of the nanostructured Ba-based clathrates. We use semi-classical Boltzmann transport equations to calculate the various thermoelectric properties as a function of reduced dimensions. We observe that there exists a delicate balance between the electrical conductivity and the electronic part of the thermal conductivity in reduced dimensions. Insights from these results can directly be used to control particle size in nanostructuring experiments.

  3. On the densification and hydration of CaCO3 particles by Q-switched laser pulses in water

    Science.gov (United States)

    Lin, Peng-Wen; Wu, Chao-Hsien; Zheng, Yuyuan; Chen, Shuei-Yuan; Shen, Pouyan

    2013-09-01

    Calcite powders subjected to Q-switched laser pulses in water were characterized by X-ray/electron diffraction and optical spectroscopy to have a significant internal compressive stress (up to ca. 1.5 GPa) with accompanied transformation into defective calcite II and hydrates. The defective calcite II particles were (0 1 0), (0 0 1), (0 1¯ 1), (0 1 3) and (0 1¯ 3) faceted with 2×(0 2 0)II commensurate superstructure and tended to hydrate epitaxially as monohydrocalcite co-existing with ikaite (CaCO3·6H2O) with extensive cleavages and amorphous calcium carbonate with porous structure. The colloidal suspension containing the densified calcite polymorphs and hydrates showed two UV-visible absorptions corresponding to a minimum band gap of ca. 5 and 3 eV, respectively.

  4. Methane hydrates in quaternary climate change

    International Nuclear Information System (INIS)

    Kennett, J. P.; Hill, T. M.; Behl, R. J.

    2005-01-01

    The hydrate reservoir in marine sediments is known to contain a large volume of exchangeable carbon stored as solid methane hydrate and associated free gas. This reservoir has been shown to be potentially unstable in response to changing intermediate water temperature and sea level (pressure). Evidence continues to grow for past episodes of major methane release at times of climatic warming. Yet few studies of late Quaternary climate change include methane hydrates as an integral part of the global climate system, in spite of the largest known oscillations at this time in sea level and upper ocean temperature changes for the Cenozoic or earlier, conditions that favor instability of the methane hydrate reservoir. Abrupt increases in atmospheric methane recorded in polar ice cores are widely believed to have resulted, not from ocean-floor methane degassing, but instead from continental wetland activation, a hypothesis thus far unsupported by geological data. Furthermore, as part of this Wetland Methane Hypothesis, the abrupt methane increases have been seen as a response to climatic warming rather than contributing significantly to the change. An alternative view (formulated as the Clathrate Gun Hypothesis) is that the speed, magnitude and timing of abrupt climate change in the recent geologic past are consistent with the process of major degassing of methane hydrates. We summarize aspects of this hypothesis here and needs to test this hypothesis. (Author)

  5. Type I Clathrates as Novel Silicon Anodes: An Electrochemical and Structural Investigation

    Science.gov (United States)

    Li, Ying; Raghavan, Rahul; Wagner, Nicholas A.; Davidowski, Stephen K.; Baggetto, Loïc; Zhao, Ran; Cheng, Qian; Yarger, Jeffery L.; Veith, Gabriel M.; Ellis‐Terrell, Carol; Miller, Michael A.; Chan, Kwai S.

    2015-01-01

    Silicon clathrates contain cage‐like structures that can encapsulate various guest atoms or molecules. An electrochemical evaluation of type I silicon clathrates based on Ba8AlySi46−y as the anode material for lithium‐ion batteries is presented here. Postcycling characterization with nuclear magnetic resonance and X‐ray diffraction shows no discernible structural or volume changes even after electrochemical insertion of 44 Li (≈1 Li/Si) into the clathrate structure. The observed properties are in stark contrast with lithiation of other silicon anodes, which become amorphous and suffer from large volume changes. The electrochemical reactions are proposed to occur as single phase reactions at approximately 0.2 and 0.4 V versus Li/Li+ during lithiation and delithiation, respectively, distinct from diamond cubic or amorphous silicon anodes. Reversible capacities as high as 499 mAh g−1 at a 5 mA g−1 rate were observed for silicon clathrate with composition Ba8Al8.54Si37.46, corresponding to ≈1.18 Li/Si. These results show that silicon clathrates could be promising durable anodes for lithium‐ion batteries. PMID:27980951

  6. Alloys of clathrate allotropes for rechargeable batteries

    Science.gov (United States)

    Chan, Candace K; Miller, Michael A; Chan, Kwai S

    2014-12-09

    The present disclosure is directed at an electrode for a battery wherein the electrode comprises clathrate alloys of silicon, germanium or tin. In method form, the present disclosure is directed at methods of forming clathrate alloys of silicon, germanium or tin which methods lead to the formation of empty cage structures suitable for use as electrodes in rechargeable type batteries.

  7. Method and apparatus for efficient injection of CO2 in oceans

    Science.gov (United States)

    West, Olivia R.; Tsouris, Constantinos; Liang, Liyuan

    2003-07-29

    A liquid CO.sub.2 injection system produces a negatively buoyant consolidated stream of liquid CO.sub.2, CO.sub.2 hydrate, and water that sinks upon release at ocean depths in the range of 700-1500 m. In this approach, seawater at a predetermined ocean depth is mixed with the liquid CO.sub.2 stream before release into the ocean. Because mixing is conducted at depths where pressures and temperatures are suitable for CO.sub.2 hydrate formation, the consolidated stream issuing from the injector is negatively buoyant, and comprises mixed CO.sub.2 -hydrate/CO.sub.2 -liquid/water phases. The "sinking" characteristic of the produced stream will prolong the metastability of CO.sub.2 ocean sequestration by reducing the CO.sub.2 dissolution rate into water. Furthermore, the deeper the CO.sub.2 hydrate stream sinks after injection, the more stable it becomes internally, the deeper it is dissolved, and the more dispersed is the resulting CO.sub.2 plume. These factors increase efficiency, increase the residence time of CO2 in the ocean, and decrease the cost of CO.sub.2 sequestration while reducing deleterious impacts of free CO.sub.2 gas in ocean water.

  8. An Experimental and Theoretical Study of CO2 Hydrate Formation Systems

    OpenAIRE

    Tzirakis, Fragkiskos; Kontogeorgis, Georgios; Coquelet, Christophe; von Solms, Nicolas; Stringari, Paolo

    2016-01-01

    Hydrate krystallisering kan blive en vigtig kulstofopsamling metode, forudsat at denne teknologi undergår yderligere forskning. Med henblik på dette mål, forsøger denne undersøgelse at kaste lys over en helt nyt emne for forskning: hydrat forfremmelse.Hydrate forfremmelse indebærer produktion af hydrat ved lavere tryk (og dermed lavere supplerende driftsomkostninger) ved brug af specielle kemikalier (promotore). I første omgang har et omfattende litteraturstudie vist at både eksperimentelle d...

  9. Carbon dioxide hydrate formation in a fixed-bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Fan, S.; Lang, X. [South China Univ. of Technology, Guangzhou (China). Key Laboratory of Enhanced Heat Transfer and Energy Conservation; Wang, Y.; Liang, D. [Chinese Academy of Sciences, Guangzhou (China). Guangzhou Inst. of Energy Conversion and Guangzhou Center of Natural Gas Hydrate; Sun, X.; Jurcik, B. [Air Liquide Laboratories, Tsukuba (Japan)

    2008-07-01

    Gas hydrates are thermodynamically stable at high pressures and near the freezing temperature of pure water. Methane hydrates occur naturally in sediments in the deep oceans and permafrost regions and constitute an extensive hydrocarbon reservoir. Carbon dioxide (CO{sub 2}) hydrates are of interest as a medium for marine sequestration of anthropogenic carbon dioxide. Sequestering CO{sub 2} as hydrate has potential advantages over most methods proposed for marine CO{sub 2} sequestration. Because this technique requires a shallower depth of injection when compared with other ocean sequestration methods, the costs of CO{sub 2} hydrate sequestration may be lower. Many studies have successfully used different continuous reactor designs to produce CO{sub 2} hydrates in both laboratory and field settings. This paper discussed a study that involved the design and construction of a fixed-bed reactor for simulation of hydrate formation system. Water, river sands and carbon dioxide were used to simulate the seep kind of hydrate formation. Carbon dioxide gas was distributed as small bubbles to enter from the bottom of the fixed-bed reactor. The paper discussed the experimental data and presented a diagram of the gas hydrate reactor system. The morphology as well as the reaction characters of CO{sub 2} hydrate was presented in detail. The results were discussed in terms of experimental phenomena and hydrate formation rate. A mathematical model was proposed for describing the process. 17 refs., 7 figs.

  10. Effects of inorganic acids and divalent hydrated metal cations (Mg(2+), Ca(2+), Co(2+), Ni(2+)) on γ-AlOOH sol-gel process.

    Science.gov (United States)

    Zhang, Jian; Xia, Yuguo; Zhang, Li; Chen, Dairong; Jiao, Xiuling

    2015-11-07

    In-depth understanding of the sol-gel process plays an essential role in guiding the preparation of new materials. Herein, the effects of different inorganic acids (HCl, HNO3 and H2SO4) and divalent hydrated metal cations (Mg(2+), Ca(2+), Co(2+), Ni(2+)) on γ-AlOOH sol-gel process were studied based on experiments and density functional theory (DFT) calculations. In these experiments, the sol originating from the γ-AlOOH suspension was formed only with the addition of HCl and HNO3, but not with H2SO4. Furthermore, the DFT calculations showed that the strong adsorption of HSO4(-) on the surface of the γ-AlOOH particles, and the hydrogen in HSO4(-) pointing towards the solvent lead to an unstable configuration of electric double layer (EDL). In the experiment, the gelation time sequence of γ-AlOOH sol obtained by adding metal ions changed when the ionic strength was equal to or greater than 0.198 mol kg(-1). The DFT calculations demonstrated that the adsorption energy of hydrated metal ions on the γ-AlOOH surface can actually make a difference in the sol-gel process.

  11. Proceedings of the 6. international conference on gas hydrates : ICGH 2008

    Energy Technology Data Exchange (ETDEWEB)

    Englezos, P. (ed.) [British Columbia Univ., Vancouver, BC (Canada); Ripmeester, J. (ed.) [National Research Council of Canada, Ottawa, ON (Canada); Dallimore, S.R. [Natural Resources Canada, Ottawa, ON (Canada). Geological Survey of Canada; Servio, P. [McGill Univ., Montreal, PQ (Canada). Dept. of Chemical Engineering; Austvik, T. [Statoil, Trondheim (Norway); Collett, T.S. [United States Geological Survey, Denver, CO (United States); Mehta, A. [Shell E and P Asia Pacific, Sarawak (Malaysia); Paull, C.K. [Monterey Bay Aquarium Research Inst., CA (United States); Sloan, E.D.Jr. [Colorado School of Mines, Golden, CO (United States); Uchida, T. [Hokkaido Univ., Sapporo (Japan)] (comps.)

    2008-07-01

    This international conference provided a forum to highlight gas hydrate research that is underway at academic institutions as well as government and industrial laboratories around the world. The gas or clathrate hydrate research community includes chemical, petroleum and mechanical engineers, geologists, geophysicists, marine biologists, chemists and physicists. The conference was attended by more than 500 delegates who presented their professional knowledge in all areas of the gas hydrates field, emphasizing new aspects. The topics of discussion included resource delineation, reservoir simulation modeling and production technology. Environmental considerations involving natural gas hydrates and global climate change were also highlighted along with carbon dioxide disposal in aquifers and deep oceans. Issues facing oil and gas operations were also discussed, with reference to flow assurance in pipelines, safety issues, permafrost and marine geohazards. Novel technologies involving hydrogen storage, carbon dioxide capture and sequestration were also highlighted along with basic science and engineering aspects of gas hydrate systems. All 417 presentations from the conference have been catalogued separately for inclusion in this database. refs., tabs., figs.

  12. Proceedings of the 6. international conference on gas hydrates : ICGH 2008

    International Nuclear Information System (INIS)

    Englezos, P.; Ripmeester, J.; Dallimore, S.R.; Collett, T.S.; Mehta, A.; Paull, C.K.; Sloan, E.D.Jr.; Uchida, T.

    2008-01-01

    This international conference provided a forum to highlight gas hydrate research that is underway at academic institutions as well as government and industrial laboratories around the world. The gas or clathrate hydrate research community includes chemical, petroleum and mechanical engineers, geologists, geophysicists, marine biologists, chemists and physicists. The conference was attended by more than 500 delegates who presented their professional knowledge in all areas of the gas hydrates field, emphasizing new aspects. The topics of discussion included resource delineation, reservoir simulation modeling and production technology. Environmental considerations involving natural gas hydrates and global climate change were also highlighted along with carbon dioxide disposal in aquifers and deep oceans. Issues facing oil and gas operations were also discussed, with reference to flow assurance in pipelines, safety issues, permafrost and marine geohazards. Novel technologies involving hydrogen storage, carbon dioxide capture and sequestration were also highlighted along with basic science and engineering aspects of gas hydrate systems. All 417 presentations from the conference have been catalogued separately for inclusion in this database. refs., tabs., figs

  13. Influence of Lithium Carbonate on C3A Hydration

    Directory of Open Access Journals (Sweden)

    Weiwei Han

    2018-01-01

    Full Text Available Lithium salts, known to ameliorate the effects of alkali-silica reaction, can make significant effects on cement setting. However, the mechanism of effects on cement hydration, especially the hydration of C3A which is critical for initial setting time of cement, is rarely reported. In this study, the development of pH value of pore solution, conductivity, thermodynamics, and mineralogical composition during hydration of C3A with or without Li2CO3 are investigated. The results demonstrate that Li2CO3 promotes C3A hydration through high alkalinity, due to higher activity of lithium ion than that of calcium ion in the solution and carbonation of C3A hydration products resulted from Li2CO3. Li2CO3 favors the C3A hydration in C3A-CaSO4·2H2O-Ca(OH2-H2O hydration system and affects the mineralogical variation of the ettringite phase(s.

  14. Molecular Level Investigation of CH 4 and CO 2 Adsorption in Hydrated Calcium–Montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Mal-Soon [Physical; McGrail, B. Peter [Physical; Rousseau, Roger [Physical; Glezakou, Vassiliki-Alexandra [Physical

    2017-11-17

    We have studied the mechanism of intercalation and methane adsorption from a H2O/CH4/CO2 mixture on a prototypical shale component, Ca-montmorillonite. We employed ab initio molecular dynamics simulations at 323 K and 90 bar to obtain molecular level information of adsorption energetics, speciation, and structural and thermodynamic properties. Interaction of CH4 with surface Lewis acidic sites (Ca2+, surface OH) results in large induced dipoles (~1 D) that lead to relatively strong adsorption energies that level off once a full CH4 layer is formed. Intercalated CH4, also exhibits induced dipoles at low hydration levels, when the interaction with Ca2+ cations are less hindered. CO2 displaces CH4 in the coordination sphere of the cations (in the interlayer) or in the surface, thereby driving CH4 extraction. Our simulations indicate that there is a Goldilocks pressure range (~60-100 bar) where scCO2 –facilitated CH4 extraction will be maximized.

  15. Vibrational spectroscopic and quantum theoretical study of host-guest interactions in clathrates: I. Hofmann type clathrates

    Directory of Open Access Journals (Sweden)

    VLADIMIR M. PETRUSEVSKI

    2000-06-01

    Full Text Available Hofmann type clatharates are host-guest compounds with the general formula M(NH32M'(CN4·2G, in which M(NH32M'(CN4 is the host lattice and G is benzene, the guest molecule. In previous studies, host-guest interactions have been investigated by analyzing the RT and LNT vibrational (infrared, far infrared and Raman spectra of these clathrates. All the observed changes in the vibrational spectra of these clathrates are referred to a host-guest interaction originating from weak hydrogen bonding between the ammonia hydrogen atoms from the host lattice and the p electron cloud of the guest (benzene molecules. In order to obtain an insight into the relative importance of the local crystalline field vs. the anharmonicity effects on the spectroscopic properties of the guest species upon enclathration, as well as to explain the observed band shifts and splittings, several quantum theoretical approaches are proposed.

  16. Methane Production and Carbon Capture by Hydrate Swapping

    DEFF Research Database (Denmark)

    Mu, Liang; von Solms, Nicolas

    2017-01-01

    There are essentially two different approaches to producing methane from natural gas hydrate reservoirs, either bring the hydrate out of its thermodynamic stability region or expose the hydrate to a substance that will form a more stable hydrate structure, forcing an in situ swapping of the trapped...... experimental runs were performed to examine the influence of operating conditions on methane production by CO2/(CO2 + N2) injection in the temperature range of 274.15–277.15 K and 7.039–10.107 MPa pressure. Our results show that the use of the (CO2 + N2) binary gas mixture is advantageous compared to the use...

  17. Modeling dissociation behaviour of methane hydrate in porous soil media

    Energy Technology Data Exchange (ETDEWEB)

    Jayasinghe, A.G.; Grozic, J.L.H. [Calgary Univ., AB (Canada). Dept. of Civil Engineering

    2008-07-01

    Gas hydrates, or clathrates, exist in the form of crystalline solid structures of hydrogen bonded water molecules where the lattice cages are occupied by guest gas molecules. Methane gas hydrates are the most common. As such, hydrate bearing sediments are considered to be a potential future energy resource. Gas hydrates also function as a source or sink for atmospheric methane, which may influence global warming. The authors emphasized that an understanding of the behaviour of soils containing gas hydrates is necessary in order to develop ways of recovering the vast gas resources that exist in the form of hydrates, particularly since hydrates are also suspected to be a potential factor in the initiation and propagation of submarine slope failures. Gas hydrate dissociation occurs when water and gas are released, resulting in an increase in pore fluid pressure, thereby causing significant reductions in effective stress leading to sediment failure. Dissociation may occur as a result of pressure reductions or increases in temperature. This study focused on the strength and deformation behaviour of hydrate bearing soils associated with temperature induced dissociation. Modeling the dissociation behavior of hydrates in porous soil media involves an understanding of the geomechanics of hydrate dissociation. This paper addressed the issue of coupling the hydrate dissociation problem with the soil deformation problem. A mathematical framework was constructed in which the thermally stimulated hydrate dissociation process in porous soil media under undrained conditions was considered with conduction heat transfer. It was concluded that a knowledge of geomechanical response of hydrate bearing sediments will enable better estimates of benefits and risks associated with the recovery process, thereby ensuring safe and economical exploration. 20 refs., 1 fig., 1 appendix.

  18. Gas hydrate dissociation prolongs acidification of the Anthropocene oceans

    OpenAIRE

    Boudreau, B.P.; Luo, Y.; Meysman, F.J.R.; Middelburg, J

    2015-01-01

    Anthropogenic warming of the oceans can release methane (CH4) currently stored in sediments as gas hydrates. This CH4 will be oxidized to CO2, thus increasing the acidification of the oceans. We employ a biogeochemical model of the multimillennial carbon cycle to determine the evolution of the oceanic dissolved carbonate system over the next 13?kyr in response to CO2 from gas hydrates, combined with a reasonable scenario for long-term anthropogenic CO2 emissions. Hydrate-derived CO2 will appr...

  19. Experimental solid state NMR of gas hydrates : problems and solutions

    Energy Technology Data Exchange (ETDEWEB)

    Moudrakovski, I.; Lu, H.; Ripmeester, J. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences; Kumar, R.; Susilo, R. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering; Luzi, M. [GeoForschungsZentrum Potsdam, Potsdam (Germany)

    2008-07-01

    Solid State NMR is a suitable spectroscopic technique for hydrate research for several reasons, including its capability to distinguish between different structural types of hydrates, its quantitative nature and potential for both in-situ and time resolved experiments. This study illustrated the applications of solid state NMR for compositional and structural studies of clathrate hydrates, with particular emphasis on experimental techniques and potential ways to overcome technical difficulties. In order to use the method to its full capacity, some instrumental developments are needed to adapt it to the specific experimental requirements of hydrate studies, such as very low temperatures and high pressures. This presentation discussed the quantification of the Carbon-13 spectra with examples from natural and synthetic hydrates prepared from multi-component mixtures of hydrocarbons. The main approach used for the first two examples was Carbon-13 NMR with Magic Angle Spinning (MAS) at -100 degrees C. The detailed characterization of mixed hydrogen hydrates required low temperature hydrogen MAS. The quantification problems encountered during these experiments were also discussed. The purpose of these recent experimental developments was to prompt wider application of Solid State NMR in hydrate research. NMR proved to be a viable method for analyzing the composition and structure of multi-component mixed gas hydrates; characterizing natural gas hydrates; and, evaluating the formation conditions and properties of mixed hydrogen hydrates. The limitations of the method were highlighted and sensible choices of experimental conditions and techniques that ensure accurate results were discussed. 34 refs., 10 figs.

  20. Study on gas hydrate as a new energy resource in the 21th century

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Byeong-Jae; Kwak Young-Hoon; Kim, Won-Sik [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

    1999-12-01

    Natural gas hydrate, a special type of clathrate hydrates, is a metastable solid compound which mainly consists of methane and water, and generally called as gas hydrate. It is stable in the specific low-temperature/high-pressure conditions. Gas hydrates play an important role as major reservoir of methane on the earth. On the other hand, the formation and dissociation of gas hydrates could cause the plugging in pipeline, gas kick during production, atmospheric pollution and geohazard. To understand the formation and dissociation of the gas hydrate, the experimental equilibrium conditions of methane hydrate were measured in pure water, 3 wt.% NaCl and MgCl{sub 2} solutions. The equilibrium conditions of propane hydrates were also measured in pure water. The relationship between methane hydrate formation time and overpressure was also analyzed through the laboratory work. The geophysical surveys using air-gun system and multibeam echo sounder were implemented to develop exploration techniques and to evaluate the gas hydrate potential in the East Sea, Korea. General indicators of submarine gas hydrates on seismic data is commonly inferred from the BSR developed parallel to the see floor, amplitude blanking at the upper part of the BSR, and phase reversal and decrease of the interval velocity at BSR. The field data were processed using Geobit 2.9.5 developed by KIGAM to detect the gas hydrate indicators. The accurate velocity analysis was performed by XVA (X-window based Velocity Analysis). Processing results show that the strong reflector occurred parallel to the sea floor were shown at about 1800 ms two way travel time. The interval velocity decrease at this strong reflector and at the reflection phase reversal corresponding to the reflection at the sea floor. Gas hydrate stability field in the study area was determined using the data of measured hydrate equilibrium condition, hydrothermal gradient and geothermal gradient. The depth of BSR detected in the seismic

  1. Synthesis and thermoelectric properties of rare earth Yb-doped Ba8−xYbxSi30Ga16 clathrates

    International Nuclear Information System (INIS)

    Liu, Lihua; Li, Feng; Wei, Yuping; Chen, Ning; Bi, Shanli; Qiu, Hongmei; Cao, Guohui; Li, Yang

    2014-01-01

    Highlights: • Samples with the chemical formula Ba8− x Yb x Si 30 Ga 16 (x = 0, 0.5, 0.7, 1 and 1.5) were prepared. • Some Yb atoms enter the clathrate lattice to replace Ba, while other Yb atoms are oxidized as Yb 2 O 3 . • The thermal conductivity decreases with Yb-doping. • Thermoelectric figure of merit ZT significantly increased. -- Abstract: The potential thermoelectric and magnetic application of clathrate materials with rare-earth doping is the focus of much of the recent research activity in the synthetic material physics and chemistry. A series of clathrate samples with the chemical formula Ba 8−x Yb x Si 30 Ga 16 (x = 0, 0.5, 0.7, 1 and 1.5) were prepared by combining arc melting, ball milling and spark plasma sintering (SPS) techniques. X-ray diffraction and scanning electronic microscopy combined with energy-dispersive X-ray spectroscopy (EDS) analysis showed the dominant phase to be the type-I clathrate. Whereas, X-ray structural refinement and EDS analysis indicated that some Yb atoms enter the clathrate lattice to replace Ba at 2a sites, while other Yb atoms are oxidized as Yb 2 O 3 precipitated around grain boundaries. The solid solubility of Yb into clathrate lattice yielded x ∼ 0.3. Comparative analysis between Yb-doped and Yb-free clathrates showed that the thermal conductivity decreases with Yb-doping. Consequently, thermoelectric figure of merit ZT significantly increased

  2. Mechanisms Leading to Co-Existence of Gas Hydrate in Ocean Sediments [Part 1 of 2

    Energy Technology Data Exchange (ETDEWEB)

    Bryant, Steven; Juanes, Ruben

    2011-12-31

    In this project we have sought to explain the co-existence of gas and hydrate phases in sediments within the gas hydrate stability zone. We have focused on the gas/brine interface at the scale of individual grains in the sediment. The capillary forces associated with a gas/brine interface play a dominant role in many processes that occur in the pores of sediments and sedimentary rocks. The mechanical forces associated with the same interface can lead to fracture initiation and propagation in hydrate-bearing sediments. Thus the unifying theme of the research reported here is that pore scale phenomena are key to understanding large scale phenomena in hydrate-bearing sediments whenever a free gas phase is present. Our analysis of pore-scale phenomena in this project has delineated three regimes that govern processes in which the gas phase pressure is increasing: fracturing, capillary fingering and viscous fingering. These regimes are characterized by different morphology of the region invaded by the gas. On the other hand when the gas phase pressure is decreasing, the corresponding regimes are capillary fingering and compaction. In this project, we studied all these regimes except compaction. Many processes of interest in hydrate-bearing sediments can be better understood when placed in the context of the appropriate regime. For example, hydrate formation in sub-permafrost sediments falls in the capillary fingering regime, whereas gas invasion into ocean sediments is likely to fall into the fracturing regime. Our research provides insight into the mechanisms by which gas reservoirs are converted to hydrate as the base of the gas hydrate stability zone descends through the reservoir. If the reservoir was no longer being charged, then variation in grain size distribution within the reservoir explain hydrate saturation profiles such as that at Mt. Elbert, where sand-rich intervals containing little hydrate are interspersed between intervals containing large hydrate

  3. Macroscopic investigation of water volume effects on interfacial dynamic behaviors between clathrate hydrate and water.

    Science.gov (United States)

    Cha, Minjun; Couzis, Alexander; Lee, Jae W

    2013-05-14

    This study investigated the effects of the water volume on the interfacial dynamics between cyclopentane (CP) hydrate and water droplet in a CP/n-decane oil mixture. The adhesion force between CP hydrate and various water droplets was determined using the z-directional microbalance. Through repetition of precise measurements over several cycles from contact to detachment, we observed abnormal wetting behaviors in the capillary bridge during the retraction process when the water drop volume is larger than 100 μL. With the increase in water droplet volumes, the contact force between CP hydrate and water also increases up to 300 μL. However, there is a dramatic reduction of increasing rate in the contact forces over 300 μL of water droplet. With the addition of the surfactants of sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) to the water droplet, the contact force between CP hydrate and solution droplet exhibits a lower value and a transition volume of the contact force comes with a smaller solution volume of 200 μL. The water volume effects on the liquid wetting of the probe and the size of capillary bridges provide important insight into hydrate growth and aggregation/agglomeration in the presence of free water phase inside gas/oil pipelines.

  4. Seismic Modeling Of Reservoir Heterogeneity Scales: An Application To Gas Hydrate Reservoirs

    Science.gov (United States)

    Huang, J.; Bellefleur, G.; Milkereit, B.

    2008-12-01

    Natural gas hydrates, a type of inclusion compound or clathrate, are composed of gas molecules trapped within a cage of water molecules. The occurrence of gas hydrates in permafrost regions has been confirmed by core samples recovered from the Mallik gas hydrate research wells located within Mackenzie Delta in Northwest Territories of Canada. Strong vertical variations of compressional and shear sonic velocities and weak surface seismic expressions of gas hydrates indicate that lithological heterogeneities control the distribution of hydrates. Seismic scattering studies predict that typical scales and strong physical contrasts due to gas hydrate concentration will generate strong forward scattering, leaving only weak energy captured by surface receivers. In order to understand the distribution of hydrates and the seismic scattering effects, an algorithm was developed to construct heterogeneous petrophysical reservoir models. The algorithm was based on well logs showing power law features and Gaussian or Non-Gaussian probability density distribution, and was designed to honor the whole statistical features of well logs such as the characteristic scales and the correlation among rock parameters. Multi-dimensional and multi-variable heterogeneous models representing the same statistical properties were constructed and applied to the heterogeneity analysis of gas hydrate reservoirs. The petrophysical models provide the platform to estimate rock physics properties as well as to study the impact of seismic scattering, wave mode conversion, and their integration on wave behavior in heterogeneous reservoirs. Using the Biot-Gassmann theory, the statistical parameters obtained from Mallik 5L-38, and the correlation length estimated from acoustic impedance inversion, gas hydrate volume fraction in Mallik area was estimated to be 1.8%, approximately 2x108 m3 natural gas stored in a hydrate bearing interval within 0.25 km2 lateral extension and between 889 m and 1115 m depth

  5. Balancing Accuracy and Computational Efficiency for Ternary Gas Hydrate Systems

    Science.gov (United States)

    White, M. D.

    2011-12-01

    Geologic accumulations of natural gas hydrates hold vast organic carbon reserves, which have the potential of meeting global energy needs for decades. Estimates of vast amounts of global natural gas hydrate deposits make them an attractive unconventional energy resource. As with other unconventional energy resources, the challenge is to economically produce the natural gas fuel. The gas hydrate challenge is principally technical. Meeting that challenge will require innovation, but more importantly, scientific research to understand the resource and its characteristics in porous media. Producing natural gas from gas hydrate deposits requires releasing CH4 from solid gas hydrate. The conventional way to release CH4 is to dissociate the hydrate by changing the pressure and temperature conditions to those where the hydrate is unstable. The guest-molecule exchange technology releases CH4 by replacing it with a more thermodynamically stable molecule (e.g., CO2, N2). This technology has three advantageous: 1) it sequesters greenhouse gas, 2) it releases energy via an exothermic reaction, and 3) it retains the hydraulic and mechanical stability of the hydrate reservoir. Numerical simulation of the production of gas hydrates from geologic deposits requires accounting for coupled processes: multifluid flow, mobile and immobile phase appearances and disappearances, heat transfer, and multicomponent thermodynamics. The ternary gas hydrate system comprises five components (i.e., H2O, CH4, CO2, N2, and salt) and the potential for six phases (i.e., aqueous, liquid CO2, gas, hydrate, ice, and precipitated salt). The equation of state for ternary hydrate systems has three requirements: 1) phase occurrence, 2) phase composition, and 3) phase properties. Numerical simulation of the production of geologic accumulations of gas hydrates have historically suffered from relatively slow execution times, compared with other multifluid, porous media systems, due to strong nonlinearities and

  6. Type I Clathrates as Novel Silicon Anodes: An Electrochemical and Structural Investigation

    OpenAIRE

    Li, Ying; Raghavan, Rahul; Wagner, Nicholas A.; Davidowski, Stephen K.; Baggetto, Lo?c; Zhao, Ran; Cheng, Qian; Yarger, Jeffery L.; Veith, Gabriel M.; Ellis?Terrell, Carol; Miller, Michael A.; Chan, Kwai S.; Chan, Candace K.

    2015-01-01

    Silicon clathrates contain cage?like structures that can encapsulate various guest atoms or molecules. An electrochemical evaluation of type I silicon clathrates based on Ba8Al y Si46?y as the anode material for lithium?ion batteries is presented here. Postcycling characterization with nuclear magnetic resonance and X?ray diffraction shows no discernible structural or volume changes even after electrochemical insertion of 44 Li (?1 Li/Si) into the clathrate structure. The observed properties ...

  7. Study on gas hydrate as a new energy resource in the twenty first century

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Byung Jae; Kim, Won Sik; Oh, Jae Ho [Korea Institute of Geology Mining and Materials, Taejon (Korea)] [and others

    1998-12-01

    Methane hydrate, a special type of clathrate hydrates, is a metastable solid compound mainly consisted of methane and water and generally called as gas hydrate. It is stable in the specific low- temperature/high-pressure conditions. Very large amount of methane that is the main component of natural gas, is accumulated in the form of methane hydrate subaquatic areas. Methane hydrate are the major reservoir of methane on the earth. On the other hand, the development and transmission through pipeline of oil and natural gas in the permafrost and deep subaquatic regions are significantly complicated by formation and dissociation of methane hydrate. The dissociation of natural methane hydrates caused by increasing temperature and decreasing pressure could cause the atmospheric pollution and geohazard. The formation, stable existence and dissociation of natural methane hydrates depend on the temperature, pressure, and composition of gas and characteristics of the interstitial waters. For the study on geophysical and geological conditions for the methane hydrate accumulation and to find BSR in the East Sea, Korea, the geophysical surveys using air-gun system, multibeam echo sounder, SBP were implemented in last September. The water temperature data vs. depth were obtained to determine the methane hydrate stability zone in the study area. The experimental equilibrium condition of methane hydrate was also measured in 3 wt.% sodium chloride solution. The relationship between Methane hydrate formation time and overpressure was analyzed through the laboratory work. (author). 49 refs., 6 tabs., 26 figs.

  8. Bi[NC5H3(CO2)2](OH2)xF (x=1 and 2): New one-dimensional Bi-coordination materials—Reversible hydration and topotactic decomposition to α-Bi2O3

    Science.gov (United States)

    Jeon, Hye Rim; Lee, Dong Woo; Ok, Kang Min

    2012-03-01

    Two one-dimensional bismuth-coordination materials, Bi[NC5H3(CO2)2](OH2)xF (x=1 and 2), have been synthesized by hydrothermal reactions using Bi2O3, 2,6-NC5H3(CO2H)2, HF, and water at 180 °C. Structures of the two materials were determined by single-crystal X-ray diffraction. Although they have different crystal structures, both Bi-organic materials shared a common structural motif, a one-dimensional chain structure consisting of Bi3+ cations and pyridine dicarboxylate linkers. Detailed structural analyses include infrared spectroscopy, thermogravimetric analysis, and reversible hydration reactions for the coordinated water molecules were reported. Also, thermal decomposition of the rod-shaped Bi[NC5H3(CO2)2](OH2)F single crystals at 800 °C led to α-Bi2O3 that maintained the same morphology of the original crystals.

  9. Synthesis and Characterization of Novel Copper(II 2D Coordination Polymers from a Fluorinated Flexible Ligand with Remarkable Clathration Ability

    Directory of Open Access Journals (Sweden)

    Kayoko Kasai

    2011-11-01

    Full Text Available Two-dimensional (2D grid coordination polymers were prepared by the reaction of 1,4-bis(4-pyridylmethyltetrafluorobenzene (bpf with Cu(NO32 in the presence of aromatic compounds. Crystal structures of {[Cu(bpf2(NO32]·(biphenyl2}n (1, {[Cu(bpf2(NO32]·(m-C6H4(OMe22}n (2, {[Cu(bpf2(NO32]·PhtBu}n (3 and {[Cu(bpf2(NO3(H2O]NO3·(bpf0.5}n (4 were determined. The grid networks were held together by C–H···O and C–H···F hydrogen bonds via the NO3− anions and the tetrafluorophenylene rings of bpf, respectively. Biphenyl, m-dimethoxybenzene, t-butylbenzene, and bpf molecules were clathrated in cyclic cavities of the grid networks through arene-perfluoroarene interactions. These coordination networks have remarkable clathration ability for aromatic compounds.

  10. Determination of appropriate condition on replacing methane from hydrate with carbon dioxide

    International Nuclear Information System (INIS)

    Zhou Xitang; Fan Shuanshi; Liang Deqing; Du Jianwei

    2008-01-01

    This paper is intended to determine the appropriate conditions for replacing CH 4 from NGH with CO 2 . By analyzing the hydration equilibrium graphs and geotherms, the HSZs of NGH and CO 2 hydrate, both in permafrost and under deep sea, were determined. Based on the above analysis and experimental results, it is found that to replace CH 4 from NGH with gaseous CO 2 , the appropriate experimental condition should be in the area surrounded by four curves: the geotherm, (H-V) CO2 , (L-V) CO2 and (H-V) CH4 , and to replace CH 4 from NGH with liquid CO 2 , the condition should be in the area surrounded by three curves: (L-V) CO2 , (H-L) CO2 and (H-V) CH4 . For conditions in other areas, either CO 2 can not form a hydrate or CH 4 can release little from its hydrate, which are not desirable results

  11. Study on molecular controlled mining system of methane hydrate; Methane hydrate no bunshi seigyo mining ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Kuriyagawa, M; Saito, T; Kobayashi, H; Karasawa, H; Kiyono, F; Nagaoki, R; Yamamoto, Y; Komai, T; Haneda, H; Takahashi, Y [National Institute for Resources and Environment, Tsukuba (Japan); Nada, H [Science and Technology Agency, Tokyo (Japan)

    1997-02-01

    Basic studies are conducted for the collection of methane from the methane hydrate that exists at levels deeper than 500m in the sea. The relationship between the hydrate generation mechanism and water cluster structure is examined by use of mass spectronomy. It is found that, among the stable liquid phase clusters, the (H2O)21H{sup +} cluster is the most stable. Stable hydrate clusters are in presence in quantities, and participate in the formation of hydrate crystal nuclei. For the elucidation of the nucleus formation mechanism, a kinetic simulation is conducted of molecules in the cohesion system consisting of water and methane molecules. Water molecules that array near methane molecules at the normal pressure is disarrayed under a higher pressure for rearray into a hydrate structure. Hydrate formation and breakdown in the three-phase equilibrium state of H2O, CH4, and CO2 at a low temperature and high pressure are tested, which discloses that supercooling is required for formation, that it is possible to extract CH4 first for replacement by guest molecule CO2 since CO2 is stabler than CH4 at a lower pressure or higher temperature, and that formation is easier to take place when the grain diameter is larger at the formation point since larger grain diameters result in a higher formation temperature. 3 figs.

  12. Linking interfacial chemistry of CO2 to surface structures of hydrated metal oxide nanoparticles: hematite.

    Science.gov (United States)

    Chernyshova, Irina V; Ponnurangam, Sathish; Somasundaran, Ponisseril

    2013-05-14

    A better understanding of interaction with dissolved CO2 is required to rationally design and model the (photo)catalytic and sorption processes on metal (hydr)oxide nanoparticles (NPs) in aqueous media. Using in situ FTIR spectroscopy, we address this problem for rhombohedral 38 nm hematite (α-Fe2O3) nanoparticles as a model. We not only resolve the structures of the adsorbed carbonate species, but also specify their adsorption sites and their location on the nanoparticle surface. The spectral relationships obtained present a basis for a new method of characterizing the microscopic structural and acid-base properties (related to individual adsorption sites) of hydrated metal (hydr)oxide NPs using atmospherically derived CO2 as a probe. Specifically, we distinguish two carbonate species suggesting two principally different adsorption mechanisms. One species, which is more weakly adsorbed, has an inner-sphere mononuclear monodentate structure which is formed by a conventional ligand-exchange mechanism. At natural levels of dissolved carbonate and pH from 3 to 11, this species is attached to the most acidic/reactive surface cations (surface states) associated with ferrihydrite-like surface defects. The second species, which is more strongly adsorbed, presents a mixed C and O coordination of bent CO2. This species uniquely recognizes the stoichiometric rhombohedral {104} facets in the NP texture. Like in gas phase, it is formed through the surface coordination of molecular CO2. We address how the adsorption sites hosting these two carbonate species are affected by the annealing and acid etching of the NPs. These results support the nanosize-induced phase transformation of hematite towards ferrihydrite under hydrous conditions, and additionally show that the process starts from the roughened areas of the facet intersections.

  13. Motion of Br2 molecules in clathrate cages. A computational study of the dynamic effects on its spectroscopic behavior.

    Science.gov (United States)

    Bernal-Uruchurtu, M I; Janda, Kenneth C; Hernández-Lamoneda, R

    2015-01-22

    This work looks into the spectroscopic behavior of bromine molecules trapped in clathrate cages combining different methodologies. We developed a semiempirical quantum mechanical model to incorporate through molecular dynamics trajectories, the effect movement of bromine molecules in clathrate cages has on its absorption spectra. A simple electrostatic model simulating the cage environment around bromine predicts a blue shift in the spectra, in good agreement with the experimental evidence.

  14. Further studies on hydration of alkynes by the PtCl4-CO catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Israelsohn, Osnat; Vollhardt, K. Peter C.; Blum, Jochanan

    2002-01-18

    Under CO atmosphere, between 80 and 120 C, a glyme solution of PtCl{sub 4} forms a carbonyl compound that promotes hydration of internal as well as terminal alkynes to give aldehyde-free ketones. The catalytic process depends strongly on the electronic and steric nature of the substrates. Part of the carbonyl functions of the catalyst can be replaced by phosphine ligands. Chiral DIOP reacts with the PtCl{sub 4}-CO compound to give a catalyst that promotes partial kinetic resolution of a racemic alkyne. Replacement of part of the CO by polystyrene-bound diphenylphosphine enables to attach the catalyst to the polymeric support. Upon entrapment of the platinum compound in a silica sol-gel matrix, it reacts as a partially recyclable catalyst. A reformulated mechanism for the PdCl{sub 4}-CO catalyzed hydration is suggested on the basis of the present study.

  15. A Fundamental Study of Inorganic Clathrate and Other Open-Framework Materials

    Energy Technology Data Exchange (ETDEWEB)

    Nolas, George [Univ. of South Florida, Tampa, FL (United States)

    2017-08-15

    Due to formidable synthetic challenges, many materials of scientific and technological interest are first obtained as microcrystalline powders. High purity, high yield processing techniques are often lacking and thus care must be taken in interpretation of the observed structural, chemical, and physical properties of powder or polycrystalline materials, which can be strongly influenced by extrinsic properties. Furthermore, the preparation of high-quality single crystals for many materials by traditional techniques can be especially challenging in cases where the elemental constituents have greatly differing melting points and/or vapor pressures, when the desired compound is thermodynamically metastable, or where growth with participation of the melt is generally not possible. New processing techniques are therefore imperative in order to investigate the intrinsic properties of these materials and elucidate their fundamental physical properties. Intermetallic clathrates constitute one such class of materials. The complex crystal structures of intermetallic clathrates are characterized by mainly group 14 host frameworks encapsulating guest-ions in polyhedral cages. The unique features of clathrate structures are intimately related to their physical properties, offering ideal systems for the study of structure-property relationships in crystalline solids. Moreover, intermetallic clathrates are being actively investigated due to their potential for application in thermoelectrics, photovoltaics and opto-electronics, superconductivity, and magnetocaloric technologies. We have developed different processing techniques in order to synthesize phase-pure high yield clathrates reproducibly, as well as grow single crystals for the first time. We also employed these techniques to synthesize new “open-framework” compounds. These advances in materials processing and crystal growth allowed for the investigation of the physical properties of a variety of different clathrate

  16. Stopped-flow studies of carbon dioxide hydration and bicarbonate dehydration in H2O and D2O. Acid-base and metal ion catalysis

    International Nuclear Information System (INIS)

    Pocker, Y.; Bjorkquist, D.W.

    1977-01-01

    The approach to equilibrium between carbon dioxide and bicarbonate has been followed by zero-order kinetics both from direction of CO 2 hydration and HCO 3 - dehydration. The rates are monitored at 25.0 0 C using stopped-flow indicator technique in H 2 O as well as D 2 O. The hydration of CO 2 is subject to catalysis by H 2 O (k 0 = 2.9 x 10 -2 s -1 ) and OH - (k/sub OH - / = 6.0 x 10 3 M -1 s -1 ). The value of 0.63 for the ratio k/sub OH - //k/sub OD - / is consistent with a mechanism utilizing a direct nucleophilic attack of OH - on CO 2 . In reverse direction HCO 3 - dehydration is catalyzed predominantly by H 3 O + (k/sub H 3 O + / 4.1 x 10 4 M -1 s -1 ) and to a much lesser degree by H 2 O (k 0 = 2 x 10 -4 s -1 ). The value of 0.56 for ratio k/sub H 3 O + //kD 3 O + / indicates that HCO 3 - may be protonated either in a preequilibrium step or in a rate-determining dehydration step. Both the hydration of CO 2 and the dehydration of bicarbonate are subject to general catalysis. For CO 2 , dibasic phosphate, a zinc imidazole complex, and a copper imidazole complex all enhanced the rate of hydration with respective rate coefficients of 3 x 10 -1 , 6.0, and 2.5 M -1 s -1 . For bicarbonate, monobasic phosphate catalyzed the rate of dehydration (k/sub H 2 PO 4 - / = 1 x 10 -1 M -1 s -1 ). Additionally in going from an ionic strength of 0.1 to 1.0 there was a negligible salt effect for the water-catalyzed hydration of CO 2 . However, the rate constant for the hydronium ion catalyzed dehydration of HCO 3 - was reduced from 4.1 x 10 4 M -1 s -1 to 2.3 x 10 4 M -1 s -1 for the same change in ionic strength. Finally the rate of CO 2 uptake by the complex Co(NH 3 ) 5 OH 2 3+ was followed spectrophotometrically both in H 2 O and D 2 O to determine the solvent isotope effect for a reaction known to involve a nucleophilic attack of a Co(III)-hydroxo complex on CO 2

  17. The Exchange Reaction Between Methane Hydrate and Carbon Dioxide: An Oceanic Feasibility Test

    Science.gov (United States)

    Dunk, R. M.; Brewer, P. G.; Peltzer, E. T.; Walz, P. M.; Hester, K. C.; Sloan, E. D.

    2006-12-01

    The conversion of CH4 hydrate to CO2 hydrate offers, in principle, a way of sequestering CO2, with the additional recovery of CH4 gas as an energy source. We report results from the first in-situ oceanic experiment on this reaction, carried out in August 2006 at the massive thermogenic hydrate mounds in 850 m water depth, Barkley Canyon, offshore from Vancouver Island (48° 18.642' N, 126° 3.903' W), using MBARI's ROV Tiburon deployed from the R/V Western Flyer. Two small cores (10 cm length, 4 cm diameter) of white hydrate were collected from exposed outcrops using an ROV operated tool and hydraulically ejected into a glass walled, closed top, reaction chamber. Approximately 2 L of liquid CO2 were dispensed into the chamber, and the chamber transferred to an aluminium base plate to seal the system. Under ambient conditions (P = 870 dbar, T = 4.0 °C, S = 34.2), the densities of natural gas hydrate and liquid CO2 are closely matched and less than that of seawater, where the hydrate cores floated at the top of the chamber fully immersed within the buoyant liquid CO2. Over the following ~48 hours, the system was inspected periodically with the ROV HDTV camera prior to examination with the sea-going laser Raman spectrometer, DORISS II. For this, the chamber was transferred to a Precision Underwater Positioner (PUP) that enabled focusing of the laser beam with sub- mm precision. Our choice of where to focus the laser was based upon the need to explore all phases the cored natural gas hydrate, liquid CO2, any created CO2 hydrate, and any liberated CH4 gas. The natural gas hydrate was composed primarily of CH4, with minor amounts of C2H6 and C3H8, indicating the presence of Structure II hydrate. To date, laboratory experiments have focused on the reaction between pure Structure I CH4 hydrate and CO2 vapour, where the difference in free energy between the CH4 and CO2 hydrate states provides a thermodynamic argument in favour of conversion. However for a Structure II

  18. Phase equilibrium condition of marine carbon dioxide hydrate

    International Nuclear Information System (INIS)

    Sun, Shi-Cai; Liu, Chang-Ling; Ye, Yu-Guang

    2013-01-01

    Highlights: ► CO 2 hydrate phase equilibrium was studied in simulated marine sediments. ► CO 2 hydrate equilibrium temperature in NaCl and submarine pore water was depressed. ► Coarse-grained silica sand does not affect CO 2 hydrate phase equilibrium. ► The relationship between equilibrium temperature and freezing point was discussed. - Abstract: The phase equilibrium of ocean carbon dioxide hydrate should be understood for ocean storage of carbon dioxide. In this paper, the isochoric multi-step heating dissociation method was employed to investigate the phase equilibrium of carbon dioxide hydrate in a variety of systems (NaCl solution, submarine pore water, silica sand + NaCl solution mixture). The experimental results show that the depression in the phase equilibrium temperature of carbon dioxide hydrate in NaCl solution is caused mainly by Cl − ion. The relationship between the equilibrium temperature and freezing point in NaCl solution was discussed. The phase equilibrium temperature of carbon dioxide hydrate in submarine pore water is shifted by −1.1 K to lower temperature region than that in pure water. However, the phase equilibrium temperature of carbon dioxide hydrate in mixture samples of coarsed-grained silica sand and NaCl solution is in agreement with that in NaCl solution with corresponding concentrations. The relationship between the equilibrium temperature and freezing point in mixture samples was also discussed.

  19. Numerical modeling of pore-scale phenomena during CO2 sequestration in oceanic sediments

    International Nuclear Information System (INIS)

    Kang, Qinjun; Tsimpanogiannis, Ioannis N.; Zhang, Dongxiao; Lichtner, Peter C.

    2005-01-01

    Direct disposal of liquid CO 2 on the ocean floor is one of the approaches considered for sequestering CO 2 in order to reduce its concentration in the atmosphere. At oceanic depths deeper than approximately 3000 m, liquid CO 2 density is higher than the density of seawater and CO 2 is expected to sink and form a pool at the ocean floor. In addition to chemical reactions between CO 2 and seawater to form hydrate, fluid displacement is also expected to occur within the ocean floor sediments. In this work, we consider two different numerical models for hydrate formation at the pore scale. The first model consists of the Lattice Boltzmann (LB) method applied to a single-phase supersaturated solution in a constructed porous medium. The second model is based on the Invasion Percolation (IP) in pore networks, applied to two-phase immiscible displacement of seawater by liquid CO 2 . The pore-scale results are upscaled to obtain constitutive relations for porosity, both transverse and for the entire domain, and for permeability. We examine deposition and displacement patterns, and changes in porosity and permeability due to hydrate formation, and how these properties depend on various parameters including a parametric study of the effect of hydrate formation kinetics. According to the simulations, the depth of CO 2 invasion in the sediments is controlled by changes in the pore-scale porosity close to the hydrate formation front. (author)

  20. Hydrate thermal dissociation behavior and dissociation enthalpies in methane-carbon dioxide swapping process

    DEFF Research Database (Denmark)

    Mu, Liang; von Solms, Nicolas

    2018-01-01

    The swapping of methane with carbon dioxide in hydrate has been proposed as a potential strategy for geologic sequestration of carbon dioxide and production of methane from natural hydrate deposits. However, this strategy requires a better understanding of the thermodynamic characteristics of CH4...... and CO2 hydrate as well as (CH4 + CO2) or (CH4 + CO2 + N2) mixed hydrates (since (CO2 + N2) gas mixture is often used as the swapping gas), along with the thermal physics property changes during gas exchange. In this study, a high pressure micro-differential scanning calorimetry (HP μ-DSC) was performed...

  1. Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2}){sub x}F (x=1 and 2): New one-dimensional Bi-coordination materials-Reversible hydration and topotactic decomposition to {alpha}-Bi{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Hye Rim [Department of Chemistry Education, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Lee, Dong Woo [Department of Chemistry, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Ok, Kang Min, E-mail: kmok@cau.ac.kr [Department of Chemistry, Chung-Ang University, Seoul 156-756 (Korea, Republic of)

    2012-03-15

    Two one-dimensional bismuth-coordination materials, Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2}){sub x}F (x=1 and 2), have been synthesized by hydrothermal reactions using Bi{sub 2}O{sub 3}, 2,6-NC{sub 5}H{sub 3}(CO{sub 2}H){sub 2}, HF, and water at 180 Degree-Sign C. Structures of the two materials were determined by single-crystal X-ray diffraction. Although they have different crystal structures, both Bi-organic materials shared a common structural motif, a one-dimensional chain structure consisting of Bi{sup 3+} cations and pyridine dicarboxylate linkers. Detailed structural analyses include infrared spectroscopy, thermogravimetric analysis, and reversible hydration reactions for the coordinated water molecules were reported. Also, thermal decomposition of the rod-shaped Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2})F single crystals at 800 Degree-Sign C led to {alpha}-Bi{sub 2}O{sub 3} that maintained the same morphology of the original crystals. - Graphical abstract: Calcination of the Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2})F single crystals at 800 Degree-Sign C results in the {alpha}-Bi{sub 2}O{sub 3} rods that maintain the original morphology of the crystals. Highlights: Black-Right-Pointing-Pointer Synthesis of one-dimensional chain Bi-organic frameworks. Black-Right-Pointing-Pointer Reversible hydration reactions of Bi[NC{sub 5}H{sub 3}(CO{sub 2}){sub 2}](OH{sub 2})F. Black-Right-Pointing-Pointer Topotactic decomposition maintaining the same morphology of the original crystals.

  2. Comparative Assessment of Advanced Gay Hydrate Production Methods

    Energy Technology Data Exchange (ETDEWEB)

    M. D. White; B. P. McGrail; S. K. Wurstner

    2009-06-30

    Displacing natural gas and petroleum with carbon dioxide is a proven technology for producing conventional geologic hydrocarbon reservoirs, and producing additional yields from abandoned or partially produced petroleum reservoirs. Extending this concept to natural gas hydrate production offers the potential to enhance gas hydrate recovery with concomitant permanent geologic sequestration. Numerical simulation was used to assess a suite of carbon dioxide injection techniques for producing gas hydrates from a variety of geologic deposit types. Secondary hydrate formation was found to inhibit contact of the injected CO{sub 2} regardless of injectate phase state, thus diminishing the exchange rate due to pore clogging and hydrate zone bypass of the injected fluids. Additional work is needed to develop methods of artificially introducing high-permeability pathways in gas hydrate zones if injection of CO{sub 2} in either gas, liquid, or micro-emulsion form is to be more effective in enhancing gas hydrate production rates.

  3. Public subscription project for international joint research proposals in fiscal 2000 - public subscription of international proposal (substitution No.3). Report on achievements in research related to industrial utilization and social systematization of gas hydrate technologies - Separate volume; 2000 nendo kokusai kyodo kenkyu teian kobo jigyo - kokusai teian kobo (daitai No.3). Gas hydrate gijutsu no sangyo riyo shakai system ka ni kansuru kenkyu kaihatsu seika hokokusho (bessatsu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-03-01

    Investigations were performed on important properties when utilization of gas hydrates to industries is discussed, such as production and decomposition speeds and storage stability. Activities have been taken in the following two fields: 1) experimental studies on production and decomposition of gas hydrates, and 2) summarized view on research related to gas hydrate self-retention effect. In Item 1), a production device of stirring system using rotating blades with gas circulation holes (self-suction type) was fabricated to have discussed the production and decomposition speeds. It was made clear that the production speed is governed by the over-cooling degree under the appropriate gas circulation and appropriate stirring conditions, and that the decomposition speed becomes abnormally high unless the self-retention status is maintained. In Item 2), following the introduction, seven researches were introduced, including the first observation of abnormal reaction of gas hydrate under the decreased pressure condition, the research by Yu. P. Handa related to gas hydrate decomposition below zero degree C, and the research by E. Mayer and A. Hall Brucker related to unexpectedly stable nitrogen, oxygen, carbon monoxide and argon clathrate gas hydrate formed from amorphous solid water. (NEDO)

  4. Understanding lattice thermal conductivity in thermoelectric clathrates: A density functional theory study on binary Si-based type-I clathrates

    Science.gov (United States)

    Euchner, Holger; Pailhès, Stéphane; Giordano, Valentina M.; de Boissieu, Marc

    2018-01-01

    Despite their crystalline nature, thermoelectric clathrates exhibit a strongly reduced lattice thermal conductivity. While the reason for this unexpected behavior is known to lie in the peculiarities of the complex crystal structure and the interplay of the underlying guest-host framework, their respective roles are still not fully disentangled and understood. Our ab initio study of the most simple type-I clathrate phase, the binary compound Ba8Si46 and its derivatives Ba8 -xSi46 seeks to identify these mechanisms and provides insight into their origin. Indeed, the strongly decreased lattice thermal conductivity in thermoelectric clathrates is a consequence of a reduction of the acoustic phonon bandwidth, a lowering of the acoustic phonon group velocities, and the amplification of three-phonon-scattering processes. While the complexity of the crystal structure is demonstrated not to be the leading factor, the reasons are manifold. A modified Si-Si interaction causes a first decrease of the sound velocity, whereas the presence of flat Ba modes results in an additional lowering. These modes correspond to confined Bloch states that are localized on the Ba atoms and significantly increase the scattering phase space and, together with an increased anharmonicity of the interatomic interactions, strongly affect the phonon lifetimes.

  5. Structural and thermoelectric properties of the type-I Sn clathrates Cs8Sn46−n(n=0,2) from Density Functional Theory (DFT)

    KAUST Repository

    Egbele, Peter O.; Shoko, Elvis; Joubert, Daniel P.

    2018-01-01

    Sn clathrates are promising phonon glass, electron crystal materials (PGEC), in which the phonon free paths are short and the electron free paths are long. We analysed the relaxed structure of Sn clathrates using four different Density Funtional

  6. Synthesis of TiO2-loaded Co0.85Se thin films with heterostructure and their enhanced catalytic activity for p-nitrophenol reduction and hydrazine hydrate decomposition

    International Nuclear Information System (INIS)

    Zuo, Yong; Song, Ji-Ming; Niu, He-Lin; Mao, Chang-Jie; Zhang, Sheng-Yi; Shen, Yu-Hua

    2016-01-01

    P-nitrophenol (4-NP) and hydrazine hydrate are considered to be highly toxic pollutants in wastewater, and it is of great importance to remove them. Herein, TiO 2 -loaded Co 0.85 Se thin films with heterostructure were successfully synthesized by a hydrothermal route. The as-synthesized samples were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy and selective-area electron diffraction. The results demonstrate that TiO 2 nanoparticles with a size of about 10 nm are easily loaded on the surface of graphene-like Co 0.85 Se nanofilms, and the NH 3  · H 2 O plays an important role in the generation and crystallization of TiO 2 nanoparticles. Brunauer–Emmett–Teller measurement shows that the obtained nanocomposites have a larger specific surface area (199.3 m 2 g −1 ) than that of Co 0.85 Se nanofilms (55.17 m 2 g −1 ) and TiO 2 nanoparticles (19.49 m 2 g −1 ). The catalytic tests indicate Co 0.85 Se–TiO 2 nanofilms have the highest activity for 4-NP reduction and hydrazine hydrate decomposition within 10 min and 8 min, respectively, compared with the corresponding precursor Co 0.85 Se nanofilms and TiO 2 nanoparticles. The enhanced catalytic performance can be attributed to the larger specific surface area and higher rate of interfacial charge transfer in the heterojunction than that of the single components. In addition, recycling tests show that the as-synthesized sample presents stable conversion efficiency for 4-NP reduction. (paper)

  7. Cu and Zn substituted silicon clathrates with the cubic type-II structure. Synthesis and characterization of Cs{sub 8}Na{sub 16}Cu{sub 3.8}Si{sub 132.2} and Cs{sub 8}Na{sub 16}Zn{sub 6.9}Si{sub 129.1}

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Marion C.; Bobev, Svilen [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE (United States)

    2017-12-13

    Studies in the systems Cs-Na-Cu-Si and Cs-Na-Zn-Si yielded the novel clathrates Cs{sub 8}Na{sub 16}(Cu,Si){sub 136} and Cs{sub 8}Na{sub 16}(Zn,Si){sub 136}, both with the cubic type-II structure [space group Fd anti 3m (no. 227), Pearson symbol cF160]. The structures of the title compounds were established from single-crystal X-ray diffraction methods, confirming the complete ordering of the Cs and Na guest atoms. The framework-building Si atoms are found to be randomly substituted by Cu atoms on framework site 96g, exclusively. In the structure of Cs{sub 8}Na{sub 16}(Zn,Si){sub 136}, the refinements indicate that the Zn and Si atoms co-occupy two of the three framework sites with notable preference for site 96g over site 32e. The corresponding refined compositions and unit cell parameters are as follows: Cs{sub 8}Na{sub 16}Cu{sub 3.8}Si{sub 132.2(1)} [a = 14.7583(15) Aa]; Cs{sub 8}Na{sub 16}Zn{sub 6.9}Si{sub 129.1(1)} [a = 14.7682(5) Aa], respectively. The type-II clathrates can be obtained only from experiments employing both Na and Cs, whereas work in the ternary Cs-Cu-Si, Cs-Zn-Si, Na-Cu-Si, and Na-Zn-Si systems failed to yield any clathrate phases. At the same conditions, exploratory studies in the K-Zn-Si and Rb-Zn-Si systems provided evidence that type-I clathrates are favored. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Atomistic modeling of structure II gas hydrate mechanics: Compressibility and equations of state

    Science.gov (United States)

    Vlasic, Thomas M.; Servio, Phillip; Rey, Alejandro D.

    2016-08-01

    This work uses density functional theory (DFT) to investigate the poorly characterized structure II gas hydrates, for various guests (empty, propane, butane, ethane-methane, propane-methane), at the atomistic scale to determine key structure and mechanical properties such as equilibrium lattice volume and bulk modulus. Several equations of state (EOS) for solids (Murnaghan, Birch-Murnaghan, Vinet, Liu) were fitted to energy-volume curves resulting from structure optimization simulations. These EOS, which can be used to characterize the compressional behaviour of gas hydrates, were evaluated in terms of their robustness. The three-parameter Vinet EOS was found to perform just as well if not better than the four-parameter Liu EOS, over the pressure range in this study. As expected, the Murnaghan EOS proved to be the least robust. Furthermore, the equilibrium lattice volumes were found to increase with guest size, with double-guest hydrates showing a larger increase than single-guest hydrates, which has significant implications for the widely used van der Waals and Platteeuw thermodynamic model for gas hydrates. Also, hydrogen bonds prove to be the most likely factor contributing to the resistance of gas hydrates to compression; bulk modulus was found to increase linearly with hydrogen bond density, resulting in a relationship that could be used predictively to determine the bulk modulus of various structure II gas hydrates. Taken together, these results fill a long existing gap in the material chemical physics of these important clathrates.

  9. Atomistic modeling of structure II gas hydrate mechanics: Compressibility and equations of state

    Directory of Open Access Journals (Sweden)

    Thomas M. Vlasic

    2016-08-01

    Full Text Available This work uses density functional theory (DFT to investigate the poorly characterized structure II gas hydrates, for various guests (empty, propane, butane, ethane-methane, propane-methane, at the atomistic scale to determine key structure and mechanical properties such as equilibrium lattice volume and bulk modulus. Several equations of state (EOS for solids (Murnaghan, Birch-Murnaghan, Vinet, Liu were fitted to energy-volume curves resulting from structure optimization simulations. These EOS, which can be used to characterize the compressional behaviour of gas hydrates, were evaluated in terms of their robustness. The three-parameter Vinet EOS was found to perform just as well if not better than the four-parameter Liu EOS, over the pressure range in this study. As expected, the Murnaghan EOS proved to be the least robust. Furthermore, the equilibrium lattice volumes were found to increase with guest size, with double-guest hydrates showing a larger increase than single-guest hydrates, which has significant implications for the widely used van der Waals and Platteeuw thermodynamic model for gas hydrates. Also, hydrogen bonds prove to be the most likely factor contributing to the resistance of gas hydrates to compression; bulk modulus was found to increase linearly with hydrogen bond density, resulting in a relationship that could be used predictively to determine the bulk modulus of various structure II gas hydrates. Taken together, these results fill a long existing gap in the material chemical physics of these important clathrates.

  10. Atomistic modeling of structure II gas hydrate mechanics: Compressibility and equations of state

    Energy Technology Data Exchange (ETDEWEB)

    Vlasic, Thomas M.; Servio, Phillip; Rey, Alejandro D., E-mail: alejandro.rey@mcgill.ca [Department of Chemical Engineering, McGill University, Montreal H3A 0C5 (Canada)

    2016-08-15

    This work uses density functional theory (DFT) to investigate the poorly characterized structure II gas hydrates, for various guests (empty, propane, butane, ethane-methane, propane-methane), at the atomistic scale to determine key structure and mechanical properties such as equilibrium lattice volume and bulk modulus. Several equations of state (EOS) for solids (Murnaghan, Birch-Murnaghan, Vinet, Liu) were fitted to energy-volume curves resulting from structure optimization simulations. These EOS, which can be used to characterize the compressional behaviour of gas hydrates, were evaluated in terms of their robustness. The three-parameter Vinet EOS was found to perform just as well if not better than the four-parameter Liu EOS, over the pressure range in this study. As expected, the Murnaghan EOS proved to be the least robust. Furthermore, the equilibrium lattice volumes were found to increase with guest size, with double-guest hydrates showing a larger increase than single-guest hydrates, which has significant implications for the widely used van der Waals and Platteeuw thermodynamic model for gas hydrates. Also, hydrogen bonds prove to be the most likely factor contributing to the resistance of gas hydrates to compression; bulk modulus was found to increase linearly with hydrogen bond density, resulting in a relationship that could be used predictively to determine the bulk modulus of various structure II gas hydrates. Taken together, these results fill a long existing gap in the material chemical physics of these important clathrates.

  11. Thermodynamic and kinetic verification of tetra-n-butyl ammonium nitrate (TBANO3) as a promoter for the clathrate process applicable to precombustion carbon dioxide capture.

    Science.gov (United States)

    Babu, Ponnivalavan; Yao, Minghuang; Datta, Stuti; Kumar, Rajnish; Linga, Praveen

    2014-03-18

    In this study, tetra-n-butyl ammonium nitrate (TBANO3) is evaluated as a promoter for precombustion capture of CO2 via hydrate formation. New hydrate phase equilibrium data for fuel gas (CO2/H2) mixture in presence of TBANO3 of various concentrations of 0.5, 1.0, 2.0, 3.0, and 3.7 mol % was determined and presented. Heat of hydrate dissociation was calculated using Clausius-Clapeyron equation and as the concentration of TBANO3 increases, the heat of hydrate dissociation also increases. Kinetic performance of TBANO3 as a promoter at different concentrations was evaluated at 6.0 MPa and 274.2 K. Based on induction time, gas uptake, separation factor, hydrate phase CO2 composition, and rate of hydrate growth, 1.0 mol % TBANO3 solution was found to be the optimum concentration at the experimental conditions of 6.0 MPa and 274.2 K for gas hydrate formation. A 93.0 mol % CO2 rich stream can be produced with a gas uptake of 0.0132 mol of gas/mol of water after one stage of hydrate formation in the presence of 1.0 mol % TBANO3 solution. Solubility measurements and microscopic images of kinetic measurements provide further insights to understand the reason for 1.0 mol % TBANO3 to be the optimum concentration.

  12. Well technologies for CO2 geological storage: CO2-resistant cement

    International Nuclear Information System (INIS)

    Barlet-Gouedard, V.; Rimmele, G.; Porcherie, O.; Goffe, B.

    2007-01-01

    Storing carbon dioxide (CO 2 ) underground is considered the most effective way for long-term safe and low-cost CO 2 sequestration. This recent application requires long-term well-bore integrity. A CO 2 leakage through the annulus may occur much more rapidly than geologic leakage through the formation rock, leading to economic loss, reduction of CO 2 storage efficiency, and potential compromise of the field for storage. The possibility of such leaks raises considerable concern about the long-term well-bore isolation and the durability of hydrated cement that is used to isolate the annulus across the producing/injection intervals in CO 2 -storage wells. We propose a new experimental procedure and methodology to study reactivity of CO 2 -Water-Cement systems in simulating the interaction of the set cement with injected supercritical CO 2 under downhole conditions. The conditions of experiments are 90 deg. C under 280 bars. The evolution of mechanical, physical and chemical properties of Portland cement with time is studied up to 6 months. The results are compared to equivalent studies on a new CO 2 -resistant material; the comparison shows significant promise for this new material. (authors)

  13. An innovative approach to enhance methane hydrate formation kinetics with leucine for energy storage application

    International Nuclear Information System (INIS)

    Veluswamy, Hari Prakash; Kumar, Asheesh; Kumar, Rajnish; Linga, Praveen

    2017-01-01

    Highlights: • Innovative combinatorial hybrid approach to reduce nucleation stochasticity and enhance hydrate growth. • Methane hydrate growth curves are similar in UTR and STR configurations in presence of leucine. • Amalgamation of stirred (STR) and unstirred (UTR) configuration is demonstrated. • Reliable method for scale up and commercial production of Solidified Natural Gas (SNG). - Abstract: Natural gas storage in clathrate hydrates or solidified natural gas (SNG) offers the safest, cleanest and the most compact mode of storage aided by the relative ease in natural gas (NG) recovery with minimal cost compared to known conventional methods of NG storage. The stochastic nature of hydrate nucleation and the slow kinetics of hydrate growth are major challenges that needs to be addressed on the SNG production side. A deterministic and fast nucleation coupled with rapid crystallization kinetics would empower this beneficial technology for commercial application. We propose a hybrid combinatorial approach of methane hydrate formation utilizing the beneficial aspect of environmentally benign amino acid (leucine) as a kinetic promoter by combining stirred and unstirred reactor operation. This hybrid approach is simple, can easily be implemented and scaled-up to develop an economical SNG technology for efficient storage of natural gas on a large scale. Added benefits include the minimal energy requirement during hydrate growth resulting in overall cost reduction for SNG technology.

  14. Gas hydrate formation process for pre-combustion capture of carbon dioxide

    International Nuclear Information System (INIS)

    Lee, Hyun Ju; Lee, Ju Dong; Linga, Praveen; Englezos, Peter; Kim, Young Seok; Lee, Man Sig; Kim, Yang Do

    2010-01-01

    In this study, gas hydrate from CO 2 /H 2 gas mixtures with the addition of tetrahydrofuran (THF) was formed in a semi-batch stirred vessel at various pressures and temperatures to investigate the CO 2 separation/recovery properties. This mixture is of interest to CO 2 separation and recovery from Integrated Gasification Combine Cycle (IGCC) power plants. During hydrate formation the gas uptake was determined and composition changes in the gas phase were obtained by gas chromatography. The impact of THF on hydrate formation from the CO 2 /H 2 was observed. The addition of THF significantly reduced the equilibrium formation conditions. 1.0 mol% THF was found to be the optimum concentration for CO 2 capture based on kinetic experiments. The present study illustrates the concept and provides thermodynamic and kinetic data for the separation/recovery of CO 2 (pre-combustion capture) from a fuel gas (CO 2 /H 2 ) mixture.

  15. The effects of ice on methane hydrate nucleation: a microcanonical molecular dynamics study.

    Science.gov (United States)

    Zhang, Zhengcai; Guo, Guang-Jun

    2017-07-26

    Although ice powders are widely used in gas hydrate formation experiments, the effects of ice on hydrate nucleation and what happens in the quasi-liquid layer of ice are still not well understood. Here, we used high-precision constant energy molecular dynamics simulations to study methane hydrate nucleation from vapor-liquid mixtures exposed to the basal, prismatic, and secondary prismatic planes of hexagonal ice (ice Ih). Although no significant difference is observed in hydrate nucleation processes for these different crystal planes, it is found, more interestingly, that methane hydrate can nucleate either on the ice surface heterogeneously or in the bulk solution phase homogeneously. Several factors are mentioned to be able to promote the heterogeneous nucleation of hydrates, including the adsorption of methane molecules at the solid-liquid interface, hydrogen bonding between hydrate cages and the ice structure, the stronger ability of ice to transfer heat than that of the aqueous solution, and the higher occurrence probability of hydrate cages in the vicinity of the ice surface than in the bulk solution. Meanwhile, however, the other factors including the hydrophilicity of ice and the ice lattice mismatch with clathrate hydrates can inhibit heterogeneous nucleation on the ice surface and virtually promote homogeneous nucleation in the bulk solution. Certainly, the efficiency of ice as a promoter and as an inhibitor for heterogeneous nucleation is different. We estimate that the former is larger than the latter under the working conditions. Additionally, utilizing the benefit of ice to absorb heat, the NVE simulation of hydrate formation with ice can mimic the phenomenon of ice shrinking during the heterogeneous nucleation of hydrates and lower the overly large temperature increase during homogeneous nucleation. These results are helpful in understanding the nucleation mechanism of methane hydrate in the presence of ice.

  16. Structural and thermoelectric properties of the type-I Sn clathrates Cs8Sn46−n(n=0,2) from Density Functional Theory (DFT)

    KAUST Repository

    Egbele, Peter O.

    2018-02-08

    Sn clathrates are promising phonon glass, electron crystal materials (PGEC), in which the phonon free paths are short and the electron free paths are long. We analysed the relaxed structure of Sn clathrates using four different Density Funtional Exchange-Correlation functionals. The phonon structures were investigated as a first step in order to determine the phonon contribution to the thermal conductivity. We determined the Seebeck coefficient and electrical conductivity of the clathrate compound and the thermoelectric figure of merit. A glimpse into the dynamics of the system for the evaluation of the thermoelectric and electronic properties is presented.

  17. The effect of hydrate promoters on gas uptake.

    Science.gov (United States)

    Xu, Chun-Gang; Yu, Yi-Song; Ding, Ya-Long; Cai, Jing; Li, Xiao-Sen

    2017-08-16

    Gas hydrate technology is considered as a promising technology in the fields of gas storage and transportation, gas separation and purification, seawater desalination, and phase-change thermal energy storage. However, to date, the technology is still not commercially used mainly due to the low gas hydrate formation rate and the low gas uptake. In this study, the effect of hydrate promoters on gas uptake was systematically studied and analyzed based on hydrate-based CH 4 storage and CO 2 capture from CO 2 /H 2 gas mixture experiments. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC) were employed to analyze the microstructures and gas compositions. The results indicate that the effect of the hydrate promoter on the gas uptake depends on the physical and chemical properties of the promoter and gas. A strong polar ionic promoter is not helpful towards obtaining the ideal gas uptake because a dense hydrate layer is easily formed at the gas-liquid interface, which hinders gas diffusion from the gas phase to the bulk solution. For a weak polar or non-polar promoter, the gas uptake depends on the dissolution characteristics among the different substances in the system. The lower the mutual solubility among the substances co-existing in the system, the higher the independence among the substances in the system; this is so that each phase has an equal chance to occupy the hydrate cages without or with small interactions, finally leading to a relatively high gas uptake.

  18. The mysteries of memory effect and its elimination with antifreeze proteins

    Energy Technology Data Exchange (ETDEWEB)

    Walker, V.; Gordienko, R.; Kuiper, M.; Huva, E.; Wu, Z. [Queen' s Univ., Kingston, ON (Canada). Dept. of Biology; Zeng, H.; Ripmeester, J. [Queen' s Univ., Kingston, ON (Canada). Dept. of Biology]|[National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences

    2008-07-01

    With the decline in easily accessible and conventional hydrocarbon supplies, exploration will focus on hydrocarbons in deep offshore waters, in permafrost or in crystalline water as gas hydrates. Crystallization of water or water-encaged gas molecules takes place when nuclei reach a critical size, but the crystal growth may be inhibited by certain antifreeze proteins (AFPs). In this study, the authors hypothesized that the crystal lattice of gas hydrates may act as an alternative for substrate antifreeze proteins (AFPs). AFP-mediated inhibition of ice and clathrate hydrate crystallization was examined. Since the AFPs had a notable ability to eliminate the memory effect (ME) or the faster reformation of clathrate hydrates after melting, the authors were prompted to examine heterogeneous nucleation. Silica, served as a model nucleator hydrophilic surface. Quartz crystal microbalance-dissipation (QCM-D) experiments showed that an active AFP was tightly adsorbed to the silica surface. However, polyvinylpyrrolidone (PVP) and polyvinylcaprolactam (PVCap), 2 commercial hydrate kinetic inhibitors that do not eliminate ME, were not as tightly adsorbed. A mutant AFP inhibited tetrahydrofuran clathrate hydrate growth, but not ME. QCM-D analysis showed that adsorption of the mutant AFP was more similar to PVCap than the active AFP. It was concluded that although there is no evidence for memory in ice reformation, the crystallization of ice and hydrates, and the elimination of the more rapid recrystallization of hydrates, can be mediated by the same proteins. The properties of adsorbed layers can be effectively monitored by QCM-D. These study results provided useful information about the inhibition mechanism of heterogeneous nucleation of clathrate hydrate. The technique facilitates the screening of potential low dose hydrate inhibitors and residues in AFPs that are involved in silica adsorption. 24 refs., 1 tab., 4 figs.

  19. Compound effect of CaCO3 and CaSO4·2H2O on the strength of steel slag: cement binding materials

    International Nuclear Information System (INIS)

    Qi, Liqian; Liu, Jiaxiang; Liu, Qian

    2016-01-01

    In this study, we replaced 30% of the cement with steel slag to prepare binding material; additionally, small amounts of CaCO 3 and CaSO 4 ·2H 2 O were added. This was done to study the compound effect of CaCO 3 and CaSO 4 ·2H 2 O on the strength of steel slag-cement binding materials. The hydration degree of the steel slag cementitious material was analyzed by XRD, TG and SEM. The results showed that the optimum proportions of CaCO 3 and CaSO 4 ·2H 2 O were 3% and 2%, respectively. Compared with the steel slag-cement binders without adding CaCO 3 and CaSO 4 ·2H 2 O, the compressive strength increased by 59.9% at 3 days and by 17.8% at 28 days. Acting as the nucleation matrix, CaCO 3 could accelerate the hydration of C 3 S. In addition, CaCO 3 was involved in the hydration reaction, generating a new hydration product, which could stably exist in a slurry. Meanwhile, CaSO 4 ·2H 2 O could increase the number of AFt. The compound effect of CaCO 3 and CaSO 4 ·2H 2 O enhanced the intensity of steel slag-cement binding materials and improved the whole hydration behavior. (author)

  20. A Computationally Efficient Equation of State for Ternary Gas Hydrate Systems

    Science.gov (United States)

    White, M. D.

    2012-12-01

    The potential energy resource of natural gas hydrates held in geologic accumulations, using lower volumetric estimates, is sufficient to meet the world demand for natural gas for nearly eight decades, at current rates of increase. As with other unconventional energy resources, the challenge is to economically produce the natural gas fuel. The gas hydrate challenge is principally technical. Meeting that challenge will require innovation, but more importantly, scientific research to understand the resource and its characteristics in porous media. The thermodynamic complexity of gas hydrate systems makes numerical simulation a particularly attractive research tool for understanding production strategies and experimental observations. Simply stated, producing natural gas from gas hydrate deposits requires releasing CH4 from solid gas hydrate. The conventional way to release CH4 is to dissociate the hydrate by changing the pressure and temperature conditions to those where the hydrate is unstable. Alternatively, the guest-molecule exchange technology releases CH4 by replacing it with more thermodynamically stable molecules (e.g., CO2, N2). This technology has three advantageous: 1) it sequesters greenhouse gas, 2) it potentially releases energy via an exothermic reaction, and 3) it retains the hydraulic and mechanical stability of the hydrate reservoir. Numerical simulation of the production of gas hydrates from geologic deposits requires accounting for coupled processes: multifluid flow, mobile and immobile phase appearances and disappearances, heat transfer, and multicomponent thermodynamics. The ternary gas hydrate system comprises five components (i.e., H2O, CH4, CO2, N2, and salt) and the potential for six phases (i.e., aqueous, nonaqueous liquid, gas, hydrate, ice, and precipitated salt). The equation of state for ternary hydrate systems has three requirements: 1) phase occurrence, 2) phase composition, and 3) phase properties. Numerical simulations that predict

  1. National Gas Hydrate Program Expedition 01 offshore India; gas hydrate systems as revealed by hydrocarbon gas geochemistry

    Science.gov (United States)

    Lorenson, Thomas; Collett, Timothy S.

    2018-01-01

    The National Gas Hydrate Program Expedition 01 (NGHP-01) targeted gas hydrate accumulations offshore of the Indian Peninsula and along the Andaman convergent margin. The primary objectives of coring were to understand the geologic and geochemical controls on the accumulation of methane hydrate and their linkages to underlying petroleum systems. Four areas were investigated: 1) the Kerala-Konkan Basin in the eastern Arabian Sea, 2) the Mahanadi and 3) Krishna-Godavari Basins in the western Bay of Bengal, and 4) the Andaman forearc Basin in the Andaman Sea.Upward flux of methane at three of the four of the sites cored during NGHP-01 is apparent from the presence of seafloor mounds, seismic evidence for upward gas migration, shallow sub-seafloor geochemical evidence of methane oxidation, and near-seafloor gas composition that resembles gas from depth.The Kerala-Konkan Basin well contained only CO2 with no detectable hydrocarbons suggesting there is no gas hydrate system here. Gas and gas hydrate from the Krishna-Godavari Basin is mainly microbial methane with δ13C values ranging from −58.9 to −78.9‰, with small contributions from microbial ethane (−52.1‰) and CO2. Gas from the Mahanadi Basin was mainly methane with lower concentrations of C2-C5 hydrocarbons (C1/C2 ratios typically >1000) and CO2. Carbon isotopic compositions that ranged from −70.7 to −86.6‰ for methane and −62.9 to −63.7‰ for ethane are consistent with a microbial gas source; however deeper cores contained higher molecular weight hydrocarbon gases suggesting a small contribution from a thermogenic gas source. Gas composition in the Andaman Basin was mainly methane with lower concentrations of ethane to isopentane and CO2, C1/C2 ratios were mainly >1000 although deeper samples were compositions range from −65.2 to −80.7‰ for methane, −53.1 to −55.2‰ for ethane is consistent with mainly microbial gas sources, although one value recorded of −35.4‰ for propane

  2. Silicon clathrates for lithium ion batteries: A perspective

    International Nuclear Information System (INIS)

    Warrier, Pramod; Koh, Carolyn A.

    2016-01-01

    Development of novel energy storage techniques is essential for the development of sustainable energy resources. Li-ion batteries have the highest rated energy density among rechargeable batteries and have attracted a lot of attention for energy storage in the last 15–20 years. However, significant advancements are required in anode materials before Li-ion batteries become viable for a wide variety of applications, including in renewable energy storage, grid storage, and electric vehicles. While graphite is the current standard anode material in commercial Li-ion batteries, it is Si that exhibits the highest specific energy density among all materials considered for this purpose. Si, however, suffers from significant volume expansion/contraction and the formation of a thick solid-electrolyte interface layer. To resolve these issues, Si clathrates are being considered for anode materials. Clathrates are inclusion compounds and contain cages in which Li could be captured. While Si clathrates offer promising advantages due to their caged structure which enables negligible volume change upon Li insertion, there remains scientific challenges and knowledge gaps to be overcome before these materials can be utilized for Li-ion battery applications, i.e., understanding lithiation/de-lithiation mechanisms, optimizing guest concentrations, as well as safe and economic synthesis routes.

  3. Silicon clathrates for lithium ion batteries: A perspective

    Science.gov (United States)

    Warrier, Pramod; Koh, Carolyn A.

    2016-12-01

    Development of novel energy storage techniques is essential for the development of sustainable energy resources. Li-ion batteries have the highest rated energy density among rechargeable batteries and have attracted a lot of attention for energy storage in the last 15-20 years. However, significant advancements are required in anode materials before Li-ion batteries become viable for a wide variety of applications, including in renewable energy storage, grid storage, and electric vehicles. While graphite is the current standard anode material in commercial Li-ion batteries, it is Si that exhibits the highest specific energy density among all materials considered for this purpose. Si, however, suffers from significant volume expansion/contraction and the formation of a thick solid-electrolyte interface layer. To resolve these issues, Si clathrates are being considered for anode materials. Clathrates are inclusion compounds and contain cages in which Li could be captured. While Si clathrates offer promising advantages due to their caged structure which enables negligible volume change upon Li insertion, there remains scientific challenges and knowledge gaps to be overcome before these materials can be utilized for Li-ion battery applications, i.e., understanding lithiation/de-lithiation mechanisms, optimizing guest concentrations, as well as safe and economic synthesis routes.

  4. Silicon clathrates for lithium ion batteries: A perspective

    Energy Technology Data Exchange (ETDEWEB)

    Warrier, Pramod, E-mail: pramod.warrier@gmail.com; Koh, Carolyn A. [Center for Hydrate Research, Chemical & Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401 (United States)

    2016-12-15

    Development of novel energy storage techniques is essential for the development of sustainable energy resources. Li-ion batteries have the highest rated energy density among rechargeable batteries and have attracted a lot of attention for energy storage in the last 15–20 years. However, significant advancements are required in anode materials before Li-ion batteries become viable for a wide variety of applications, including in renewable energy storage, grid storage, and electric vehicles. While graphite is the current standard anode material in commercial Li-ion batteries, it is Si that exhibits the highest specific energy density among all materials considered for this purpose. Si, however, suffers from significant volume expansion/contraction and the formation of a thick solid-electrolyte interface layer. To resolve these issues, Si clathrates are being considered for anode materials. Clathrates are inclusion compounds and contain cages in which Li could be captured. While Si clathrates offer promising advantages due to their caged structure which enables negligible volume change upon Li insertion, there remains scientific challenges and knowledge gaps to be overcome before these materials can be utilized for Li-ion battery applications, i.e., understanding lithiation/de-lithiation mechanisms, optimizing guest concentrations, as well as safe and economic synthesis routes.

  5. A comparative study of different methods for the generation of tetra-n-butyl ammonium bromide clathrate hydrate slurry in a cold storage air-conditioning system

    International Nuclear Information System (INIS)

    Shi, X.J.; Zhang, P.

    2013-01-01

    Highlights: ► Four kinds of TBAB CHS generation methods are experimentally investigated. ► Accession of CHS into supercooled solution can be helpful to the generation. ► Higher flow rate results in higher energy efficiency of CHS generation. - Abstract: A cold storage air-conditioning system using tetra-n-butyl ammonium bromide (TBAB) clathrate hydrate slurry (CHS) as cold storage medium was built to investigate the high-efficiency method of TBAB CHS generation. In the present study, four kinds of different TBAB CHS generation methods were experimentally investigated and compared, and these methods included continuously cooling, turning off refrigerator while crystals appearing, supercooling release and accession of TBAB CHS into supercooled TBAB aqueous solution. The results showed that continuously cooling would lead to severe adhesion of crystal to the heat exchanger wall, and supercooling release took place with a big stochastic characteristic, hence the first and third method were concluded not reliable. Both the second and fourth methods could maintain the temperature of heat exchanger wall at a relatively higher level, therefore the crystal adhesion to the heat exchanger wall would be reduced significantly, which led to higher coefficient of performance (COP). In addition, accession of TBAB CHS into TBAB supercooled solution could shorten the time of supercooling release, resulting in about 21.8–35.4% shorter generation time than other methods. Moreover, the influence of flow rate on the CHS generation process was investigated, and the results showed that higher flow rate generally resulted in higher system COP

  6. National Gas Hydrate Program Expedition 01 offshore India; gas hydrate systems as revealed by hydrocarbon gas geochemistry

    Science.gov (United States)

    Lorenson, Thomas; Collett, Timothy S.

    2018-01-01

    The National Gas Hydrate Program Expedition 01 (NGHP-01) targeted gas hydrate accumulations offshore of the Indian Peninsula and along the Andaman convergent margin. The primary objectives of coring were to understand the geologic and geochemical controls on the accumulation of methane hydrate and their linkages to underlying petroleum systems. Four areas were investigated: 1) the Kerala-Konkan Basin in the eastern Arabian Sea, 2) the Mahanadi and 3) Krishna-Godavari Basins in the western Bay of Bengal, and 4) the Andaman forearc Basin in the Andaman Sea.Upward flux of methane at three of the four of the sites cored during NGHP-01 is apparent from the presence of seafloor mounds, seismic evidence for upward gas migration, shallow sub-seafloor geochemical evidence of methane oxidation, and near-seafloor gas composition that resembles gas from depth.The Kerala-Konkan Basin well contained only CO2 with no detectable hydrocarbons suggesting there is no gas hydrate system here. Gas and gas hydrate from the Krishna-Godavari Basin is mainly microbial methane with δ13C values ranging from −58.9 to −78.9‰, with small contributions from microbial ethane (−52.1‰) and CO2. Gas from the Mahanadi Basin was mainly methane with lower concentrations of C2-C5 hydrocarbons (C1/C2 ratios typically >1000) and CO2. Carbon isotopic compositions that ranged from −70.7 to −86.6‰ for methane and −62.9 to −63.7‰ for ethane are consistent with a microbial gas source; however deeper cores contained higher molecular weight hydrocarbon gases suggesting a small contribution from a thermogenic gas source. Gas composition in the Andaman Basin was mainly methane with lower concentrations of ethane to isopentane and CO2, C1/C2 ratios were mainly >1000 although deeper samples were exploration and occurs in a forearc basin. Each of these hydrate-bearing systems overlies and is likely supported by the presence and possible migration of gas from deeper gas-prone petroleum

  7. Effect of gas hydrates melting on seafloor slope stability

    Science.gov (United States)

    Sultan, N.; Cochonat, P.; Foucher, J. P.; Mienert, J.; Haflidason, H.; Sejrup, H. P.

    2003-04-01

    Henriet, J.-P.; Mienert, J. (Ed.): Gas hydrates: relevance to world margin stability and climate change. Geological Society Special Publication, 137. The Geological Society: London, UK, p. 267-274. Handa,Y.P., 1989. Effect of Hydrostatic Pressure and Salinity on the Stability of Gas Hydrates. J.Phys.Chem., Vol.94, p.2652-2657. Henry, P., Thomas, M.; Clennell, M.B., 1999. Formation of Natural Gas Hydrates in Marine Sediments 2. Thermodynamic Calculations of Stability Conditions in Porous Sediments,” J. Geophys. Res., 104, p. 23005. Sloan, E.D. Jr., 1998. Clathrate hydrates of natural gases. Marcel Dekker Inc., 2nd edition, New York, pp. 705. Soave G, 1972. Equilibrium

  8. Sequential SO{sub 2}/CO{sub 2} capture enhanced by steam reactivation of a CaO-based sorbent

    Energy Technology Data Exchange (ETDEWEB)

    Vasilije Manovic; Edward J. Anthony [CANMET Energy Technology Centre-Ottawa, Ottawa, ON (Canada). Natural Resources Canada

    2008-07-15

    The steam hydration reactivation characteristics of three limestone samples after multiple CO{sub 2} looping cycles are presented here. The CO{sub 2} cycles were performed in a tube furnace (TF) and the resulting samples were hydrated by steam in a pressure reactor (PR). The reactivation was performed with spent samples after carbonation and calcination stages. The reactivation tests were done with a saturated steam pressure at 200{sup o}C and also at atmospheric pressure and 100 {sup o}C. The characteristics of the reactivation samples were examined using BET and BJH pore characterization (for the original and spent samples, and samples reactivated under different conditions) and also by means of a thermogravimetric analyzer (TGA). The levels of hydration achieved by the reactivated samples were determined as well as the conversions during sulphation and multiple carbonation cycles. It was found that the presence of a CaCO{sub 3} layer strongly hinders sorbent hydration and adversely affects the properties of the reactivated sorbent with regard to its behavior in sulphation and multiple carbonation cycles. Here, hydration of calcined samples under pressure is the most effective method to produce superior sulphur sorbents. However, reactivation of calcined samples under atmospheric conditions also produces sorbents with significantly better properties in comparison to those of the original sorbents. These results show that separate CO{sub 2} capture and SO{sub 2} retention in fluidized bed systems enhanced by steam reactivation is promising even for atmospheric conditions if the material for hydration is taken from the calciner. 49 refs., 5 figs., 3 tabs.

  9. Hydration of amino acids: FTIR spectra and molecular dynamics studies.

    Science.gov (United States)

    Panuszko, Aneta; Adamczak, Beata; Czub, Jacek; Gojło, Emilia; Stangret, Janusz

    2015-11-01

    The hydration of selected amino acids, alanine, glycine, proline, valine, isoleucine and phenylalanine, has been studied in aqueous solutions by means of FTIR spectra of HDO isotopically diluted in H2O. The difference spectra procedure and the chemometric method have been applied to remove the contribution of bulk water and thus to separate the spectra of solute-affected HDO. To support interpretation of obtained spectral results, molecular dynamics simulations of amino acids were performed. The structural-energetic characteristic of these solute-affected water molecules shows that, on average, water affected by amino acids forms stronger and shorter H-bonds than those in pure water. Differences in the influence of amino acids on water structure have been noticed. The effect of the hydrophobic side chain of an amino acid on the solvent interactions seems to be enhanced because of the specific cooperative coupling of water strong H-bond chain, connecting the carboxyl and amino groups, with the clathrate-like H-bond network surrounding the hydrocarbon side chain. The parameter derived from the spectral data, which corresponds to the contributions of the population of weak hydrogen bonds of water molecules which have been substituted by the stronger ones in the hydration sphere of amino acids, correlated well with the amino acid hydrophobicity indexes.

  10. FY1995 molecular control technology for mining of methane-gas-hydrate; 1995 nendo methane hydrate no bunshi seigyo mining

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    The objectives of the investigation are as follows: 1) developing a method to control formation/dissociation of methane-gas-hydrate, 2) developing a technology to displace methane gas by CO{sub 2} in methane-gas-hydrate deposit, 3) developing a technology to produce methane gas from the deposit efficiently. The final purpose of the project is to create new mining industry that solves both the problems of energy and global environment. 1) Clustering of water molecules is found to play the key role in the methane gas hydrate formation. 2) Equilibrium properties and kinetics of gas hydrates formation and dissociation in bulk-scale gas-hydrate are clarified in the practical environmental conditions. 3) Particle size of hydrate deposit influences the formation and dissociation of bulk-scale gas-hydrate crystal. 4) Mass transfer between gas and liquid phase in turbulent bubbly flow is a function of bubble diameter. The mass transfer depends on interfacial dynamics. (NEDO)

  11. Modeling thermodynamic properties of propane or tetrahydrofuran mixed with carbon dioxide or methane in structure-II clathrate hydrates

    NARCIS (Netherlands)

    Fang, Bin; Ning, Fulong; Cao, Pinqiang; Peng, Li; Wu, Jianyang; Zhang, Zhun; Vlugt, T.J.H.; Kjelstrup, Signe

    2017-01-01

    A sound knowledge of thermodynamic properties of sII hydrates is of great importance to understand the stability of sII gas hydrates in petroleum pipelines and in natural settings. Here, we report direct molecular dynamics (MD) simulations of the thermal expansion coefficient, the

  12. High Pressure Properties of a Ba-Cu-Zn-P Clathrate-I

    Directory of Open Access Journals (Sweden)

    Juli-Anna Dolyniuk

    2016-08-01

    Full Text Available The high pressure properties of the novel tetrel-free clathrate, Ba8Cu13.1Zn3.3P29.6, were investigated using synchrotron powder X-ray diffraction. The pressure was applied using a diamond anvil cell. No structural transitions or decomposition were detected in the studied pressure range of 0.1–7 GPa. The calculated bulk modulus for Ba8Cu13.1Zn3.3P29.6 using a third-order Birch-Murnaghan equation of state is 65(6 GPa at 300 K. This bulk modulus is comparable to the bulk moduli of Ge- and Sn-based clathrates, like A8Ga16Ge30 (A = Sr, Ba and Sn19.3Cu4.7P22I8, but lower than those for the transition metal-containing silicon-based clathrates, Ba8TxSi46−x, T = Ni, Cu; 3 ≤ x ≤ 5.

  13. Superconductivity of Ba8Si46-xGax clathrates

    Science.gov (United States)

    Li, Yang; Zhang, Ruihong; Chen, Ning; Ma, Xingqiao; Cao, Guohui; Luo, Z. P.; Hu, C. R.; Ross, Joseph H., Jr.

    2007-03-01

    We have presented a combined experimental and theoretical study of the effect of Gallium substitution on the superconductivity of the type I clathrate Ba8Si46-xGax. In Ga-doped clathrates, the Ga state is found to be strongly hybridized with the cage conduction-band state. Ga substitution results in a shift toward to a lower energy, a decrease of density of states at Fermi level, a lowering of the carrier concentration and a breakage of integrity of the sp3 hybridized networks. These play key roles in the suppression of superconductivity. For Ba8Si40Ga6, the onset of the superconducting transition occurs at Tc=3.3 K. The investigation of the magnetic superconducting state shows that Ba8Si40Ga6 is a type II superconductor. The critical magnetic fields were measured to be Hc1=35 Oe and Hc2=8.5 kOe. Our estimate of the lectron-phonon coupling reveals that Ba8Si40Ga6 is a moderate phonon-mediated BCS superconductor.

  14. Effect of hydration on the amide I band in the binary solvents dioxane-D2O and dioxane-H2O

    International Nuclear Information System (INIS)

    Kobayashi, M.; Kobayashi, M.

    1980-01-01

    Hydration of amides in aqueous solutions has been studied by measuring the infrared spectra of amides (benzamide, p-methoxybenzamide, and ropionamide) in dioxane-D 2 O and dioxane-H 2 O mixtures. The absorption due to the C=O stretching (or amide I band) exhibited a very remarkable red shift accompanied by a characteristic change of the band shape as the water content in the medium increased. The spectral change is attributed to the change of the hydration state at the carbonyl oxygen. In the aqueous mixtures, amide molecules participate in an equilibrium among various states of hydration. The weighted mean frequency of the ν/sub C = O/ absorption, anti ν/sub C = O/, varied in proportion to the water contained in the medium. The difference between the anti ν/sub C = O/ value in pure water and that in pure dioxane,Δ anti ν, was used as a measure of the maximum degree of hydration. It was larger for propionamide than for the aromatic amides, suggesting that the steric effect of the substituents is of major importance in hydration. The isotope effect, Δ anti ν/sub D 2 O//Δ anti ν/sub H 2 O/, in the range from 1.4 to 1.6 for all cases examined, indicated that stronger hydration of amides occurred with D 2 O than with H 2 O

  15. Paraffin molecule mobility in channel clathrates of urea on spectroscopic NMR relaxation data

    CERN Document Server

    Kriger, Y G; Chekhova, G N

    2001-01-01

    The temperature dependences of the protons spin-lattice relaxation time (T sub I) in the channel clathrates of urea with paraffins are measured. The data on the T sub I are interpreted within the frames of the model of the paraffins molecules and their fragments orientation in the clathrate channels. The dynamics peculiarities are connected with the disproportion effects of these compounds

  16. Adsorption of Dissolved Gases (CH4, CO2, H2, Noble Gases) by Water-Saturated Smectite Clay Minerals

    Science.gov (United States)

    Bourg, I. C.; Gadikota, G.; Dazas, B.

    2016-12-01

    Adsorption of dissolved gases by water-saturated clay minerals plays important roles in a range of fields. For example, gas adsorption in on clay minerals may significantly impact the formation of CH4 hydrates in fine-grained sediments, the behavior of CH4 in shale, CO2 leakage across caprocks of geologic CO2 sequestration sites, H2 leakage across engineered clay barriers of high-level radioactive waste repositories, and noble gas geochemistry reconstructions of hydrocarbon migration in the subsurface. Despite its importance, the adsorption of gases on clay minerals remains poorly understood. For example, some studies have suggested that clay surfaces promote the formation of CH4 hydrates, whereas others indicate that clay surfaces inhibit the formation of CH4 hydrates. Here, we present molecular dynamics (MD) simulations of the adsorption of a range of gases (CH4, CO2, H2, noble gases) on clay mineral surfaces. Our results indicate that the affinity of dissolved gases for clay mineral surfaces has a non-monotone dependence on the hydrated radius of the gas molecules. This non-monotone dependence arises from a combination of two effects: the polar nature of certain gas molecules (in particular, CO2) and the templating of interfacial water structure by the clay basal surface, which results in the presence of interfacial water "cages" of optimal size for intermediate-size gas molecules (such as Ne or Ar).

  17. Carbon dioxide induced bubble formation in a CH4-CO2-H2O ternary system: a molecular dynamics simulation study.

    Science.gov (United States)

    Sujith, K S; Ramachandran, C N

    2016-02-07

    The extraction of methane from its hydrates using carbon dioxide involves the decomposition of the hydrate resulting in a CH4-CO2-H2O ternary solution. Using classical molecular dynamics simulations, we investigate the evolution of dissolved gas molecules in the ternary system at different concentrations of CO2. Various compositions considered in the present study resemble the solution formed during the decomposition of methane hydrates at the initial stages of the extraction process. We find that the presence of CO2 aids the formation of CH4 bubbles by causing its early nucleation. Elucidation of the composition of the bubble revealed that in ternary solutions with high concentration of CO2, mixed gas bubbles composed of CO2 and CH4 are formed. To understand the role of CO2 in the nucleation of CH4 bubbles, the structure of the bubble formed was analyzed, which revealed that there is an accumulation of CO2 at the interface of the bubble and the surrounding water. The aggregation of CO2 at the bubble-water interface occurs predominantly when the concentration of CO2 is high. Radial distribution function for the CH4-CO2 pair indicates that there is an increasingly favorable direct contact between dissolved CH4 and CO2 molecules in the bubble-water interface. It is also observed that the presence of CO2 at the interface results in the decrease in surface tension. Thus, CO2 leads to greater stability of the bubble-water interface thereby bringing down the critical size of the bubble nuclei. The results suggest that a rise in concentration of CO2 helps in the removal of dissolved CH4 thereby preventing the accumulation of methane in the liquid phase. Thus, the presence of CO2 is predicted to assist the decomposition of methane hydrates in the initial stages of the replacement process.

  18. Advances in Geological CO{sub 2} Sequestration and Co-Sequestration with O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Verba, Circe A; O& #x27; Connor, William K.; Ideker, J.H.

    2012-10-28

    The injection of CO{sub 2} for Enhanced Oil Recovery (EOR) and sequestration in brine-bearing formations for long term storage has been in practice or under investigation in many locations globally. This study focused on the assessment of cement wellbore seal integrity in CO{sub 2}- and CO{sub 2}-O{sub 2}-saturated brine and supercritical CO{sub 2} environments. Brine chemistries (NaCl, MgCl{sub 2}, CaCl{sub 2}) at various saline concentrations were investigated at a pressure of 28.9 MPa (4200 psi) at both 50{degree}C and 85{degree}C. These parameters were selected to simulate downhole conditions at several potential CO{sub 2} injection sites in the United States. Class H portland cement is not thermodynamically stable under these conditions and the formation of carbonic acid degrades the cement. Dissociation occurs and leaches cations, forming a CaCO{sub 3} buffered zone, amorphous silica, and other secondary minerals. Increased temperature affected the structure of C-S-H and the hydration of the cement leading to higher degradation rates.

  19. The Driving Forces of Guest Substitution in Gas Hydrates—A Laser Raman Study on CH4-CO2 Exchange in the Presence of Impurities

    Directory of Open Access Journals (Sweden)

    Bettina Beeskow-Strauch

    2012-02-01

    Full Text Available The recovery of CH4 gas from natural hydrate formations by injection of industrially emitted CO2 is considered to be a promising solution to simultaneously access an unconventional fossil fuel reserve and counteract atmospheric CO2 increase. CO2 obtained from industrial processes may contain traces of impurities such as SO2 or NOx and natural gas hydrates may contain higher hydrocarbons such as C2H6 and C3H8. These additions have an influence on the properties of the resulting hydrate phase and the conversion process of CH4-rich hydrates to CO2-rich hydrates. Here we show results of a microscopic and laser Raman in situ study investigating the effects of SO2-polluted CO2 and mixed CH4-C2H6 hydrate on the exchange process. Our study shows that the key driving force of the exchange processes is the establishment of the chemical equilibrium between hydrate phase and the surrounding phases. The exchange rate is also influenced by the guest-to-cavity ratio as well as the thermodynamic stability in terms of p-T conditions of the original and resulting hydrate phase. The most effective molecule exchange is related to structural changes (sI-sII which indicates that hydrate decomposition and reformation processes are the occurring processes.

  20. Modelling of tetrahydrofuran promoted gas hydrate systems for carbon dioxide capture processes

    DEFF Research Database (Denmark)

    Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens

    2014-01-01

    A thermodynamic study of a novel gas hydrate based CO2 capture process is presented.•Model predicts this process unsuitable for CO2 capture from power station flue gases. A thermodynamic modelling study of both fluid phase behaviour and hydrate phase behaviour is presented for the quaternary system...... of water, tetrahydrofuran, carbon dioxide and nitrogen. The applied model incorporates the Cubic-Plus-Association (CPA) equation of state for the fluid phase description and the van der Waals-Platteeuw hydrate model for the solid (hydrate) phase. Six binary pairs are studied for their fluid phase behaviour...... accurate descriptions of both fluid- and hydrate phase equilibria in the studied system and its subsystems. The developed model is applied to simulate two simplified, gas hydrate-based processes for post-combustion carbon dioxide capture from power station flue gases. The first process, an unpromoted...

  1. Isotopic effect in the hydration reactions of 2, 2, 2 - trichloro - 1 - arylethanones

    International Nuclear Information System (INIS)

    Marconi, D.O.M.; Zucco, C.; Tanaka, A.S.; Nome, F.

    1985-01-01

    The equilibrium constants and rate constants for hydration and de-hydration of 2, 2, 2 - trichloro - 1 - arylethanones in tetrahydrofurane (THF) / H 2 O - D 2 O e THF/H 2 O using the proton inventory technique involved in the transition state are studied. (M.J.C.) [pt

  2. Natural Gas Hydrate as a Storage Mechanism for Safe, Sustainable and Economical Production from Offshore Petroleum Reserves

    Directory of Open Access Journals (Sweden)

    Michael T. Kezirian

    2017-06-01

    Full Text Available Century Fathom presents an innovative process to utilize clathrate hydrates for the production, storage and transportation of natural gas from off-shore energy reserves in deep ocean environments. The production scheme was developed by considering the preferred state of natural gas in the deep ocean and addressing the hazards associated with conventional techniques to transport natural gas. It also is designed to mitigate the significant shipping cost inherent with all methods. The resulting proposed scheme restrains transport in the hydrate form to the ocean and does not attempt to supply energy to the residential consumer. Instead; the target recipients are industrial operations. The resulting operational concept is intrinsically safer by design; environmentally sustainable and significantly cost-effective compared with currently proposed schemes for the use of natural gas hydrates and has the potential to be the optimal solution for new production of reserves; depending on the distance to shore and capacity of the petroleum reserve. A potential additional benefit is the byproduct of desalinated water.

  3. Compound effect of CaCO{sub 3} and CaSO{sub 4}·2H{sub 2}O on the strength of steel slag: cement binding materials

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Liqian; Liu, Jiaxiang; Liu, Qian, E-mail: ljxpost@263.net [Beijing Key Laboratory of Electrochemical Process and Technology for Materials, The State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing (China)

    2016-03-15

    In this study, we replaced 30% of the cement with steel slag to prepare binding material; additionally, small amounts of CaCO{sub 3} and CaSO{sub 4}·2H{sub 2}O were added. This was done to study the compound effect of CaCO{sub 3} and CaSO{sub 4}·2H{sub 2}O on the strength of steel slag-cement binding materials. The hydration degree of the steel slag cementitious material was analyzed by XRD, TG and SEM. The results showed that the optimum proportions of CaCO{sub 3} and CaSO{sub 4}·2H{sub 2}O were 3% and 2%, respectively. Compared with the steel slag-cement binders without adding CaCO{sub 3} and CaSO{sub 4}·2H{sub 2}O, the compressive strength increased by 59.9% at 3 days and by 17.8% at 28 days. Acting as the nucleation matrix, CaCO{sub 3} could accelerate the hydration of C{sub 3}S. In addition, CaCO{sub 3} was involved in the hydration reaction, generating a new hydration product, which could stably exist in a slurry. Meanwhile, CaSO{sub 4}·2H{sub 2}O could increase the number of AFt. The compound effect of CaCO{sub 3} and CaSO{sub 4}·2H{sub 2}O enhanced the intensity of steel slag-cement binding materials and improved the whole hydration behavior. (author)

  4. Molecular dynamics study of CO2 hydrate dissociation: Fluctuation-dissipation and non-equilibrium analysis.

    Science.gov (United States)

    English, Niall J; Clarke, Elaine T

    2013-09-07

    Equilibrium and non-equilibrium molecular dynamics (MD) simulations have been performed to investigate thermal-driven break-up of planar CO2 hydrate interfaces in liquid water at 300-320 K. Different guest compositions, at 85%, 95%, and 100% of maximum theoretical occupation, led to statistically-significant differences in the observed initial dissociation rates. The melting temperatures of each interface were estimated, and dissociation rates were observed to be strongly dependent on temperature, with higher dissociation rates at larger over-temperatures vis-à-vis melting. A simple coupled mass and heat transfer model developed previously was applied to fit the observed dissociation profiles, and this helps to identify clearly two distinct régimes of break-up; a second well-defined region is essentially independent of composition and temperature, in which the remaining nanoscale, de facto two-dimensional system's lattice framework is intrinsically unstable. From equilibrium MD of the two-phase systems at their melting point, the relaxation times of the auto-correlation functions of fluctuations in number of enclathrated guest molecules were used as a basis for comparison of the variation in the underlying, non-equilibrium, thermal-driven dissociation rates via Onsager's hypothesis, and statistically significant differences were found, confirming the value of a fluctuation-dissipation approach in this case.

  5. Nasogastric Hydration in Infants with Bronchiolitis Less Than 2 Months of Age.

    Science.gov (United States)

    Oakley, Ed; Bata, Sonny; Rengasamy, Sharmila; Krieser, David; Cheek, John; Jachno, Kim; Babl, Franz E

    2016-11-01

    To determine whether nasogastric hydration can be used in infants less than 2 months of age with bronchiolitis, and characterize the adverse events profile of these infants compared with infants given intravenous (IV) fluid hydration. A descriptive retrospective cohort study of children with bronchiolitis under 2 months of age admitted for hydration at 3 centers over 3 bronchiolitis seasons was done. We determined type of hydration (nasogastric vs IV fluid hydration) and adverse events, intensive care unit admission, and respiratory support. Of 491 infants under 2 months of age admitted with bronchiolitis, 211 (43%) received nonoral hydration: 146 (69%) via nasogastric hydration and 65 (31%) via IV fluid hydration. Adverse events occurred in 27.4% (nasogastric hydration) and 23.1% (IV fluid hydration), difference of 4.3%; 95%CI (-8.2 to 16.9), P = .51. The majority of adverse events were desaturations (21.9% nasogastric hydration vs 21.5% IV fluid hydration, difference 0.4%; [-11.7 to 12.4], P = .95). There were no pulmonary aspirations in either group. Apneas and bradycardias were similar in each group. IV fluid hydration use was positively associated with intensive care unit admission (38.5% IV fluid hydration vs 19.9% nasogastric hydration; difference 18.6%, [5.1-32.1], P = .004); and use of ventilation support (27.7% IV fluid hydration vs 15.1% nasogastric hydration; difference 12.6 [0.3-23], P = .03). Fewer infants changed from nasogastric hydration to IV fluid hydration than from IV fluid hydration to nasogastric hydration (12.3% vs 47.7%; difference -35.4% [-49 to -22], P hydration can be used in the majority of young infants admitted with bronchiolitis. Nasogastric hydration and IV fluid hydration had similar rates of complications. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Hydrate bearing clayey sediments: Formation and gas production concepts

    KAUST Repository

    Jang, Jaewon; Santamarina, Carlos

    2016-01-01

    Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2single bondCH4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

  7. Hydrate bearing clayey sediments: Formation and gas production concepts

    KAUST Repository

    Jang, Jaewon

    2016-06-20

    Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2single bondCH4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

  8. A DFT-based comparative equilibrium study of thermal dehydration and hydrolysis of CaCl2 hydrates and MgCl2 hydrates for seasonal heat storage

    NARCIS (Netherlands)

    Pathak, A.D.; Gaastra-Nedea, S.V.; Zondag, H.A.; Rindt, C.C.M.; Smeulders, D.M.J.

    2016-01-01

    Salt hydrates store solar energy in chemical form via a reversible dehydration–hydration reaction. However, as a side reaction to dehydration, hydrolysis (HCl formation) may occur in chloride based salt hydrates (specially in MgCl2 hydrates), affecting the durability of the storage system. The

  9. Competition between intermolecular interaction and configuration entropy as the structure-determining factor for inclusion compounds

    Energy Technology Data Exchange (ETDEWEB)

    Subbotin, O.; Belosludov, V.; Adamova, T. [Russian Academy of Science, Novosibirsk (Russian Federation). Nikolaev Inst. of Inorganic Chemistry; Belosludov, R.; Kawazoe, Y. [Tohoku Univ., Aoba-ku, Sendai (Japan). Inst. for Materials Research; Kudoh, J.I. [Tohoku Univ., Aoba-ku, Sendai (Japan). Center for Northeast Asia Studies

    2008-07-01

    This paper presented a newly developed method to accurately predict the thermodynamic properties of clathrate hydrates, particularly their structural phase transitions under pressure. The method is based on the theory of Van-der-Waals and Platteeuw with some modifications that include the influence of guest molecules on the host lattice. The model was used to explain the exception from the established rule that small guest molecules form structure s1 and large molecules form structure s2 hydrates. In this study, the thermodynamic properties of argon (Ar) hydrate and methane hydrate, each in both cubic structure s1 and s2 were modelled. The model showed that two competing factors play a role in the formation of inclusions, notably the intermolecular interaction of guest molecules with water molecules, and the configuration entropy. Competition of these 2 factors determines the structure of hydrate formed at different pressures. The model provides an accurate description of the thermodynamic properties of gas hydrates and how they behave under pressure. For the argon hydrates, the structural phase transition from structure s2 to s1 at high pressure was predicted, while methane hydrates were predicted to be metastable in the s2 structure. The model can be used for other inclusion compounds with the same type of composition such as clathrate silicon, zeolites, and inclusion compounds of semiconductor elements. 17 refs., 5 figs.

  10. Measurements of gas permeability and non-Darcy flow in gas-water-hydrate systems

    Energy Technology Data Exchange (ETDEWEB)

    Ersland, G.; Husebo, J.; Graue, A.; Kvamme, B. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology; Baldwin, B. [Green Country Petrophysics LLC, Dewey, OK (United States); Stevens, J.; Howard, J. [ConocoPhillips, OK (United States)

    2008-07-01

    Storage of carbon dioxide (CO{sub 2}) in natural gas hydrate reservoirs may offer stable long-term storage of a greenhouse gas while benefiting from methane production, without requiring heat. By exposing hydrate to a thermodynamically preferred hydrate former, CO{sub 2}, the hydrate may be maintained macroscopically in the solid state and retain the stability of the formation. However, there is concern over the flow capacity in such reservoirs. This depends on several factors, notably thermodynamic destabilization of hydrate in small pores due to capillary effects; the presence of liquid channels separating the hydrate from the mineral surfaces; and, the connectivity of gas or liquid filled pores and channels. This paper described a technique for measuring gas permeability in gas-water-hydrate systems. It reported on several experiments that measured gas permeability during stages of hydrate growth in sandstone core plugs. Interactions between minerals and surrounding molecules were also discussed. The formation of methane hydrate in porous media was monitored and quantified with magnetic resonance imaging (MRI). MRI images of hydrate growth within the porous rock were provided along with measurements of gas permeability and non-Darcy flow effects at various hydrate saturations. Gas permeability was measured at steady state flow of methane through the hydrate-bearing core sample. Significant gas permeability was recorded for porous sandstone even when hydrates occupied up to 60 per cent of the pore space. It was concluded that MRI imaging can be used effectively to map and quantify hydrate saturation in sandstone core plugs. 27 refs., 2 tabs., 10 figs.

  11. Co3(PO4)2·4H2O

    Science.gov (United States)

    Lee, Young Hoon; Clegg, Jack K.; Lindoy, Leonard F.; Lu, G. Q. Max; Park, Yu-Chul; Kim, Yang

    2008-01-01

    Single crystals of Co3(PO4)2·4H2O, tricobalt(II) bis­[ortho­phosphate(V)] tetra­hydrate, were obtained under hydro­thermal conditions. The title compound is isotypic with its zinc analogue Zn3(PO4)2·4H2O (mineral name hopeite) and contains two independent Co2+ cations. One Co2+ cation exhibits a slightly distorted tetra­hedral coordination, while the second, located on a mirror plane, has a distorted octa­hedral coordination environment. The tetra­hedrally coordinated Co2+ is bonded to four O atoms of four PO4 3− anions, whereas the six-coordinate Co2+ is cis-bonded to two phosphate groups and to four O atoms of four water mol­ecules (two of which are located on mirror planes), forming a framework structure. In addition, hydrogen bonds of the type O—H⋯O are present throughout the crystal structure. PMID:21200978

  12. Iodine capture by Hofmann-type clathrate Ni(II)(pz)[Ni(II)(CN)_4

    International Nuclear Information System (INIS)

    Massasso, Giovanni; Long, Jerome; Haines, Julien; Devautour-Vinot, Sabine; Maurin, Guillaume; Larionova, Joulia; Guerin, Christian; Guari, Yannick; Grandjean, Agnes; Onida, Barbara; Donnadieu, Bruno

    2014-01-01

    The thermally stable Hofmann-type clathrate framework Ni(II)(pz)[Ni(II)(CN)_4] (pz = pyrazine) was investigated for the efficient and reversible sorption of iodine (I_2) in the gaseous phase and in solution with a maximum adsorption capacity of 1 mol of I_2 per 1 mol of Ni(II)pz)[Ni(II)(CN)_4] in solution. (authors)

  13. Distribution of Al atoms in the clathrate-I phase Ba8AlxSi46-x at x = 6.9.

    Science.gov (United States)

    Bobnar, Matej; Böhme, Bodo; Wedel, Michael; Burkhardt, Ulrich; Ormeci, Alim; Prots, Yurii; Drathen, Christina; Liang, Ying; Nguyen, Hong Duong; Baitinger, Michael; Grin, Yuri

    2015-07-28

    The clathrate-I phase Ba8AlxSi46-x has been structurally characterized at the composition x = 6.9 (space group Pm3[combining macron]n, no. 223, a = 10.4645(2) Å). A crystal structure model comprising the distribution of aluminium and silicon atoms in the clathrate framework was established: 5.7 Al atoms and 0.3 Si atoms occupy the crystallographic site 6c, while 1.2 Al atoms and 22.8 Si atoms occupy site 24k. The atomic distribution was established based on a combination of (27)Al and (29)Si NMR experiments, X-ray single-crystal diffraction and wavelength-dispersive X-ray spectroscopy.

  14. Phase equilibria with hydrate formation in H2O + CO2 mixtures modeled with reference equations of state

    Czech Academy of Sciences Publication Activity Database

    Jäger, A.; Vinš, Václav; Gernert, J.; Span, R.; Hrubý, Jan

    2013-01-01

    Roč. 338, Januar (2013), s. 100-113 ISSN 0378-3812 R&D Projects: GA ČR(CZ) GPP101/11/P046; GA ČR(CZ) GAP101/11/1593 Institutional support: RVO:61388998 Keywords : carbon dioxide * gas hydrate * modeling Subject RIV: BJ - Thermodynamics Impact factor: 2.241, year: 2013 http://www.sciencedirect.com/science/article/pii/S0378381212005158

  15. Ab initio molecular dynamics simulations reveal localization and time evolution dynamics of an excess electron in heterogeneous CO2-H2O systems.

    Science.gov (United States)

    Liu, Ping; Zhao, Jing; Liu, Jinxiang; Zhang, Meng; Bu, Yuxiang

    2014-01-28

    In view of the important implications of excess electrons (EEs) interacting with CO2-H2O clusters in many fields, using ab initio molecular dynamics simulation technique, we reveal the structures and dynamics of an EE associated with its localization and subsequent time evolution in heterogeneous CO2-H2O mixed media. Our results indicate that although hydration can increase the electron-binding ability of a CO2 molecule, it only plays an assisting role. Instead, it is the bending vibrations that play the major role in localizing the EE. Due to enhanced attraction of CO2, an EE can stably reside in the empty, low-lying π(*) orbital of a CO2 molecule via a localization process arising from its initial binding state. The localization is completed within a few tens of femtoseconds. After EE trapping, the ∠OCO angle of the core CO2 (-) oscillates in the range of 127°∼142°, with an oscillation period of about 48 fs. The corresponding vertical detachment energy of the EE is about 4.0 eV, which indicates extreme stability of such a CO2-bound solvated EE in [CO2(H2O)n](-) systems. Interestingly, hydration occurs not only on the O atoms of the core CO2 (-) through formation of O⋯H-O H-bond(s), but also on the C atom, through formation of a C⋯H-O H-bond. In the latter binding mode, the EE cloud exhibits considerable penetration to the solvent water molecules, and its IR characteristic peak is relatively red-shifted compared with the former. Hydration on the C site can increase the EE distribution at the C atom and thus reduce the C⋯H distance in the C⋯H-O H-bonds, and vice versa. The number of water molecules associated with the CO2 (-) anion in the first hydration shell is about 4∼7. No dimer-core (C2O4 (-)) and core-switching were observed in the double CO2 aqueous media. This work provides molecular dynamics insights into the localization and time evolution dynamics of an EE in heterogeneous CO2-H2O media.

  16. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.; Yoon, S.; Wentzcovitch, R. M.; Monteiro, P. J. M.

    2014-01-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  17. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.

    2014-07-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  18. On the intermolecular vibrational coupling, hydrogen bonding, and librational freedom of water in the hydration shell of mono- and bivalent anions.

    Science.gov (United States)

    Ahmed, Mohammed; Namboodiri, V; Singh, Ajay K; Mondal, Jahur A

    2014-10-28

    The hydration energy of an ion largely resides within the first few layers of water molecules in its hydration shell. Hence, it is important to understand the transformation of water properties, such as hydrogen-bonding, intermolecular vibrational coupling, and librational freedom in the hydration shell of ions. We investigated these properties in the hydration shell of mono- (Cl(-) and I(-)) and bivalent (SO4(2-) and CO3(2-)) anions by using Raman multivariate curve resolution (Raman-MCR) spectroscopy in the OH stretch, HOH bend, and [bend+librational] combination bands of water. Raman-MCR of aqueous Na-salt (NaCl, NaI, Na2SO4, and Na2CO3) solutions provides ion-correlated spectra (IC-spectrum) which predominantly bear the vibrational characteristics of water in the hydration shell of respective anions. Comparison of these IC-spectra with the Raman spectrum of bulk water in different spectral regions reveals that the water is vibrationally decoupled with its neighbors in the hydration shell. Hydrogen-bond strength and librational freedom also vary with the nature of anion: hydrogen-bond strength, for example, decreases as CO3(2-) > SO4(2-) > bulk water ≈ Cl(-) > I(-); and the librational freedom increases as CO3(2-) ≈ SO4(2-) water water in the hydration shell of anions.

  19. Dehydration behaviour of hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Dette, S.S.; Stelzer, T.; Jones, M.J.; Ulrich, J. [Martin-Luther-Universitaet Halle-Wittenberg, Zentrum fuer Ingenieurwissenschaften, Verfahrenstechnik/TVT, 06099 Halle (Germany)

    2010-07-15

    Immersing a crystalline solvate in a suitable anti-solvent can induce phase transformation to solvent-free solid phase. In certain cases the solvent-mediated phase transition results in the generation of hollow, tubular structures. Both the tube dimensions of sodium-2-keto-L-gulonate anhydrate (skga) and the dehydration kinetics of sodium-2-keto-L-gulonate monohydrate (skgm) can be modified by the antisolvent employed. An explanation for the variable dehydration behaviour of skgm in the antisolvents is presented here. Furthermore, other crystalline hydrates were dehydrated in dry methanol. Providing an operational window can be found, any hydrate material could possibly find use in the production of tubes (micro- or nanotubes for different applications). The experimental conditions selected (dry methanol as antisolvent, dehydration temperature at 25 C) for the dehydration did not lead to the anhydrate tube growth for all hydrates investigated. Based upon the results presented here a first hypothesis is presented to explain this effect. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Numerical simulation of Class 3 hydrate reservoirs exploiting using horizontal well by depressurization and thermal co-stimulation

    International Nuclear Information System (INIS)

    Yang, Shengwen; Lang, Xuemei; Wang, Yanhong; Wen, Yonggang; Fan, Shuanshi

    2014-01-01

    Highlights: • Depressurization and thermal co-stimulation using horizontal well were proposed. • 3D stimulation showed that gas release rate was 3 × 10 5 m 3 per day within 450 days. • 2D stimulation showed that Class 3 hydrates could be dissociated within 8500 days. • 2D Simulation showed that heat flow was 1620 W lasting 1500 days, and decreased fast. • 1.1× 10 5 kg water was collected within 2000 days and then no more water was produced. - Abstract: Class 3 hydrate reservoirs exploiting using horizontal well by depressurization and thermal co-stimulation was simulated using the HydarteResSim code. Results showed that more than 20% of hydrates in the reservoirs had been dissociated within 450 days at the well temperature of 42 °C and well pressure of 0.1P 0 , 0.2P 0 (P 0 is the initial pressure of the reservoirs, simplifying 42 °C and 0.1P 0 , 42 °C and 0.2P 0 ). While the production behavior of 42 °C and 0.5P 0 , 42 °C and 0.8P 0 were not so exciting. In order to understand the production character of the well in long term, the cross section of 1 m length reservoirs was simulated. Simulation results showed that 4.5 × 10 5 m 3 gas would be collected within 4500 days and 1.1 × 10 6 kg water could be produced within 1500 days in the well at 42 °C and 0.1P 0 . 3.5 × 10 5 m 3 gas would be collected within 8500 days and 1.1 × 10 6 kg water could be produced within 1500 days in the well at 42 °C and 0.2P 0 . The heat flow was 1620 W at the beginning and then decreased rapidly in the two cases. For reservoirs of 1495.2 m in length, about 6.7 × 10 8 m 3 and 5.3 × 10 8 m 3 gas would be collected in the well corresponding to conditions of 42 °C and 0.1P 0 , and 42 °C and 0.2P 0

  1. Effects of substituting D2O for H2O on SANS measurements of hydrating cement

    International Nuclear Information System (INIS)

    Sabine, T.M.; Prior, M.J.

    2002-01-01

    Full text: Small angle neutron scattering (SANS) measurements of cement have been found useful in the investigation of the shape and growth of particles formed during hydration. Calorimetric measurements of hydrating cement samples have shown that the substitution of D 2 O for H 2 O has the effect of slowing the hydration process. In order to throw some light on this phenomenon, we have measured SANS profiles from cement samples hydrating in H 2 O and D 2 O. This involved obtaining SANS profiles at half-hourly intervals during the initial stage of hydration. The only instruments capable of this at present are located at the Hahn-Meitner Institute in Berlin and at the Nuclear Physics Institute at Rez near Prague. Initial experiments carried out on the V12a UltraSANS diffractometer at The Hahn-Meitner Institute were only partially successful owing to excessive multiple scattering in the D 2 O samples. Subsequent measurements were therefore carried out on the similar instrument at Rez near Prague which operates at a shorter neutron wavelength. Results from these measurements show profound differences in the evolution of cements hydrating in D 2 O and those hydrating in H 2 O

  2. Theoretical study on the spectroscopic properties of CO3(*-).nH2O clusters: extrapolation to bulk.

    Science.gov (United States)

    Pathak, Arup K; Mukherjee, Tulsi; Maity, Dilip K

    2008-10-24

    Vertical detachment energies (VDE) and UV/Vis absorption spectra of hydrated carbonate radical anion clusters, CO(3)(*-).nH(2)O (n=1-8), are determined by means of ab initio electronic structure theory. The VDE values of the hydrated clusters are calculated with second-order Moller-Plesset perturbation (MP2) and coupled cluster theory using the 6-311++G(d,p) set of basis functions. The bulk VDE value of an aqueous carbonate radical anion solution is predicted to be 10.6 eV from the calculated weighted average VDE values of the CO(3)(*-).nH(2)O clusters. UV/Vis absorption spectra of the hydrated clusters are calculated by means of time-dependent density functional theory using the Becke three-parameter nonlocal exchange and the Lee-Yang-Parr nonlocal correlation functional (B3LYP). The simulated UV/Vis spectrum of the CO(3)(*-).8H(2)O cluster is in excellent agreement with the reported experimental spectrum for CO(3)(*-) (aq), obtained based on pulse radiolysis experiments.

  3. Reconsideration on Hydration of Sodium Ion: From Micro-Hydration to Bulk Hydration

    Science.gov (United States)

    Yongquan, Zhou; Chunhui, Fang; Yan, Fang; Fayan, Zhu; Haiwen, Ge; Hongyan, Liu

    2017-12-01

    Micro hydration structures of the sodium ion, [Na(H2O) n ]+, n = 1-12, were probed by density functional theory (DFT) at B3LYP/aug-cc-pVDZ level in both gaseous and aqueous phase. The predicted equilibrium sodium-oxygen distance of 0.240 nm at the present level of theory. The four-, five- and six-coordinated cluster can transform from each other at the ambient condition. The analysis of the successive water binding energy and natural charge population (NBO) on Na+ clearly shows that the influence of Na+ on the surrounding water molecules goes beyond the first hydration shell with the hydration number of 6. The Car-Parrinello molecular dynamic simulation shows that only the first hydration sphere can be found, and the hydration number of Na+ is 5.2 and the hydration distance ( r Na-O) is 0.235 nm. All our simulations mentioned in the present paper show an excellent agreement with the diffraction result from X-ray scattering study.

  4. LABORATORY EXPERIMENTS TO SIMULATE CO2 OCEAN DISPOSAL

    Energy Technology Data Exchange (ETDEWEB)

    Stephen M. Masutani

    1999-12-31

    This Final Technical Report summarizes the technical accomplishments of an investigation entitled ''Laboratory Experiments to Simulate CO{sub 2} Ocean Disposal'', funded by the U.S. Department of Energy's University Coal Research Program. This investigation responds to the possibility that restrictions on greenhouse gas emissions may be imposed in the future to comply with the Framework Convention on Climate Change. The primary objective of the investigation was to obtain experimental data that can be applied to assess the technical feasibility and environmental impacts of oceanic containment strategies to limit release of carbon dioxide (CO{sub 2}) from coal and other fossil fuel combustion systems into the atmosphere. A number of critical technical uncertainties of ocean disposal of CO{sub 2} were addressed by performing laboratory experiments on liquid CO{sub 2} jet break-up into a dispersed droplet phase, and hydrate formation, under deep ocean conditions. Major accomplishments of this study included: (1) five jet instability regimes were identified that occur in sequence as liquid CO{sub 2} jet disintegration progresses from laminar instability to turbulent atomization; (2) linear regression to the data yielded relationships for the boundaries between the five instability regimes in dimensionless Ohnesorge Number, Oh, and jet Reynolds Number, Re, space; (3) droplet size spectra was measured over the full range of instabilities; (4) characteristic droplet diameters decrease steadily with increasing jet velocity (and increasing Weber Number), attaining an asymptotic value in instability regime 5 (full atomization); and (5) pre-breakup hydrate formation appears to affect the size distribution of the droplet phase primary by changing the effective geometry of the jet.

  5. Structure of cometary atmospheres. II. Ion distribution

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, M [Tokyo Univ. (Japan). Inst. of Space and Aeronautical Science

    1976-04-01

    The distributions of various kinds of molecular ions in the atmospheres of new and old comets made up from dirty ice of the second kind (H/sub 2/O ice and hydrate clathrates of CO and N/sub 2/) have been computed at various heliocentric distances, by taking into account photoionization, ion-molecular reactions, electron-ion recombinations, and some transport effects. The results have been compared with observations and other computations. It is argued that dirty ice of the second kind model will impose a restriction on the theory of the origin of the solar system.

  6. Evaluation of Hydrate Inhibition Performance of Water-soluble Polymers using Torque Measurement and Differential Scanning Calorimeter

    International Nuclear Information System (INIS)

    Shin, Kyuchul; Park, Juwoon; Kim, Jakyung; Kim, Hyunho; Seo, Yutaek; Lee, Yohan; Seo, Yongwon

    2014-01-01

    In this work, hydrate inhibition performance of water-soluble polymers including pyrrolidone, caprolactam, acrylamide types were evaluated using torque measurement and high pressure differential scanning calorimeter (HP µ-DSC). The obtained experimental results suggest that the studied polymers represent the kinetic hydrate inhibition (KHI) performance. 0.5 wt% polyvinylcaprolactam (PVCap) solution shows the hydrate onset time of 34.4 min and subcooling temperature of 15.9 K, which is better KHI performance than that of pure water - hydrate onset time of 12.3 min and subcooling temperature of 6.0 K. 0.5 wt% polyvinylpyrrolidone (PVP) solution shows the hydrate onset time of 27.6 min and the subcooling temperature of 13.2 K while polyacrylamide-co-acrylic acid partial sodium salt (PAM-co-AA) solution shows less KHI performance than PVP solution at both 0.5 and 5.0 wt%. However, PAM-co-AA solution shows slow growth rate and low hydrate amount than PVCap. In addition to hydrate onset and growth condition, torque change with time was investigated as one of KHI evaluation methods. 0.5 wt% PVCap solution shows the lowest average torque of 6.4 N cm and 0.5 wt% PAM-co-AA solution shows the average torque of 7.2 N cm. For 0.5 wt% PVP solution, it increases 11.5 N cm and 5.0 wt% PAM-co-AA solution shows the maximum average torque of 13.4 N cm, which is similar to the average torque of pure water, 15.2 N cm. Judging from the experimental results obtained by both an autoclave and a HP µ-DSC, the PVCap solution shows the best performance among the KHIs in terms of delaying hydrate nucleation. From these results, it can be concluded that the torque change with time is useful to identify the flow ability of tested solution, and the further research on the inhibition of hydrate formation can be approached in various aspects using a HP µ-DSC

  7. Upscaling of enzyme enhanced CO2 capture

    DEFF Research Database (Denmark)

    Gladis, Arne Berthold

    Fossil fuels are the backbone of the energy generation in the coming decades for USA, China, India and Europe, hence high greenhouse gas emissions are expected in future. Carbon capture and storage technology (CCS) is the only technology that can mitigate greenhouse gas emissions from fossil fuel...... the mass transfer of CO2 with slow-capturing but energetically favorable solvents can open up a variety of new process options for this technology. The ubiquitous enzyme carbonic anhydrase (CA), which enhances the mass transfer of CO2 in the lungs by catalyzing the reversible hydration of CO2, is one very...... enhanced CO2 capture technology by identifying the potentials and limitations in lab and in pilot scale and benchmarking the process against proven technologies. The main goal was to derive a realistic process model for technical size absorbers with a wide range of validity incorporating a mechanistic...

  8. Phase equilibria, crystal chemistry, electronic structure and physical properties of Ag-Ba-Ge clathrates

    Energy Technology Data Exchange (ETDEWEB)

    Zeiringer, I.; Chen Mingxing [Institute of Physical Chemistry, University of Vienna, Waehringerstr. 42, 1090 Wien (Austria); Bednar, I.; Royanian, E.; Bauer, E. [Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, 1040 Wien (Austria); Podloucky, R.; Grytsiv, A. [Institute of Physical Chemistry, University of Vienna, Waehringerstr. 42, 1090 Wien (Austria); Rogl, P., E-mail: peter.franz.rogl@univie.ac.at [Institute of Physical Chemistry, University of Vienna, Waehringerstr. 42, 1090 Wien (Austria); Effenberger, H. [Institute of Mineralogy and Crystallography, University of Vienna, A-1090 Wien (Austria)

    2011-04-15

    In the Ag-Ba-Ge system the clathrate type-{Iota} solid solution, Ba{sub 8}Ag{sub x}Ge{sub 46-x-y{open_square}y}, extends at 800 deg. C from binary Ba{sub 8}Ge{sub 43{open_square}3} ({open_square} is a vacancy) to Ba{sub 8}Ag{sub 5.3}Ge{sub 40.7}. For the clathrate phase (1 {<=} x {<=} 5.3) the cubic space group Pm3-bar n was established by X-ray powder diffraction and confirmed by X-ray single-crystal analyses of the samples Ba{sub 8}Ag{sub 2.3}Ge{sub 41.9{open_square}1.8} and Ba{sub 8}Ag{sub 4.4}Ge{sub 41.3{open_square}0.3}. Increasing the concentration of Ag causes the lattice parameters of the solid solution to increase linearly from a value of a = 1.0656 (x = 0, y = 3) to a = 1.0842 (x = 4.8, y = 0) nm. Site preference determination using X-ray refinement reveals that Ag atoms preferentially occupy the 6d site randomly mixed with Ge and vacancies, which become filled in the compound Ba{sub 8}Ag{sub 4.8}Ge{sub 41.2} when the Ag content increases. At 600 {sup o}C the phase region of the clathrate solution Ba{sub 8}Ag{sub x}Ge{sub 46-x-y{open_square}y} becomes separated from the Ba-Ge boundary and extends from 6.6 to 9.8 at.% Ag. The compound Ba{sub 6}Ge{sub 25} (clathrate type-{Iota}X) dissolves at 800 {sup o}C a maximum of 1.5 at.% Ag. The homogeneity regions of the two ternary compounds BaAg{sub 2-x}Ge{sub 2+x} (ThCr{sub 2}Si{sub 2}-type, 0.2 {<=} x {<=} 0.7) and Ba(Ag{sub 1-x}Ge{sub x}){sub 2} (AlB{sub 2}-type, 0.65 {<=} x {<=} 0.75) were established at 800 deg. C. Studies of transport properties for the series of Ba{sub 8}Ag{sub x}Ge{sub 46-x-y{open_square}y} compounds evidenced that electrons are the predominant charge carriers with the Fermi energy close to a gap. Its position can be fine-tuned by the substitution of Ge by Ag atoms and by mechanical processing of the starting material, Ba{sub 8}Ge{sub 43}. The proximity of the electronic structure at Fermi energy of Ba{sub 8}Ag{sub x}Ge{sub 46-x-y{open_square}y} to a gap is also corroborated by density

  9. The influence of Na2O on the hydration of C3A II. Suspension hydration

    NARCIS (Netherlands)

    Spierings, G.A.C.M.; Stein, H.N.

    1976-01-01

    The influence of Na2O on the hydration of C3A was studied in suspensions from the start of the reaction onwards. The heat evolution rate in very early stages of the hydration, measured at varying NaOH concentrations, and SEM, indicate that at NaOH concentrations larger then 0.1 M the reaction

  10. Geochemistry of clathrate-derived methane in Arctic Ocean waters

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, S.M.; Reagan, M.T.; Moridis, G.J.; Cameron-Smith, P.J.

    2010-03-15

    Alterations to the composition of seawater are estimated for microbial oxidation of methane from large polar clathrate destabilizations, which may arise in the coming century. Gas fluxes are taken from porous flow models of warming Arctic sediment. Plume spread parameters are then used to bracket the volume of dilution. Consumption stoichiometries for the marine methanotrophs are based on growth efficiency and elemental/enzyme composition data. The nutritional demand implied by extra CH{sub 4} removal is compared with supply in various high latitude water masses. For emissions sized to fit the shelf break, reaction potential begins at one hundred micromolar and falls to order ten a thousand kilometers downstream. Oxygen loss and carbon dioxide production are sufficient respectively to hypoxify and acidify poorly ventilated basins. Nitrogen and the monooxygenase transition metals may be depleted in some locations as well. Deprivation is implied relative to existing ecosystems, along with dispersal of the excess dissolved gas. Physical uncertainties are inherent in the clathrate abundance, patch size, outflow buoyancy and mixing rate. Microbial ecology is even less defined but may involve nutrient recycling and anaerobic oxidizers.

  11. In-situ study of the thermal properties of hydrate slurry by high pressure DSC

    Energy Technology Data Exchange (ETDEWEB)

    Sari, O.; Hu, J.; Brun, F.; Erbeau, N. [Institute of Thermal Engineering, University of Applied Sciences of Western Switzerland, Yverdon-les-Bains (Switzerland); Homsy, P. [Nestec, Vevey (Switzerland); Logel, J.-C. [Axima Refrigeration, Bischheim (France)

    2008-07-01

    Knowing the enthalpy of hydrate slurry is very essential for energy balance and industrial applications. No direct measurement processes had been developed in this field in the past time. A new experimental method with special device has been developed to carry out on-line measurement of the thermal properties for hydrate slurry under dynamic conditions. With this special device, it is possible to deliver the hydrate slurry to the high pressure DSC (Differential Scanning Calorimetry) directly from the production tank or pipes. Thermal data acquisition will be performed afterwards by DSC. The investigated conditions were at pressure of 30 bar and temperature of {approx}+7 {sup o}C. The dissociation enthalpy of CO{sub 2} hydrate slurry was about 54 kJ/kg, corresponding 10.8% of solid fraction. The on-line measurement results for CO{sub 2} hydrate slurry give a good tendency to apply this phase change slurry to the industrial refrigeration process. (author)

  12. Towards understanding the role of amines in the SO2 hydration and the contribution of the hydrated product to new particle formation in the Earth's atmosphere.

    Science.gov (United States)

    Lv, Guochun; Nadykto, Alexey B; Sun, Xiaomin; Zhang, Chenxi; Xu, Yisheng

    2018-08-01

    By theoretical calculations, the gas-phase SO 2 hydration reaction assisted by methylamine (MA) and dimethylamine (DMA) was investigated, and the potential contribution of the hydrated product to new particle formation (NPF) also was evaluated. The results show that the energy barrier for aliphatic amines (MA and DMA) assisted SO 2 hydration reaction is lower than the corresponding that of water and ammonia assisted SO 2 hydration. In these hydration reactions, nearly barrierless reaction (only a barrier of 0.1 kcal mol -1 ) can be found in the case of SO 2  + 2H 2 O + DMA. These lead us to conclude that the SO 2 hydration reaction assisted by MA and DMA is energetically facile. The temporal evolution for hydrated products (CH 3 NH 3 + -HSO 3 - -H 2 O or (CH 3 ) 2 NH 2 + -HSO 3 - -H 2 O) in molecular dynamics simulations indicates that these complexes can self-aggregate into bigger clusters and can absorb water and amine molecules, which means that these hydrated products formed by the hydration reaction may serve as a condensation nucleus to initiate the NPF. Copyright © 2018 Elsevier Ltd. All rights reserved.

  13. In Situ Raman Analyses of Natural Gas and Gas Hydrates at Hydrate Ridge, Oregon

    Science.gov (United States)

    Peltzer, E. T.; White, S. N.; Dunk, R. M.; Brewer, P. G.; Sherman, A. D.; Schmidt, K.; Hester, K. C.; Sloan, E. D.

    2004-12-01

    During a July 2004 cruise to Hydrate Ridge, Oregon, MBARI's sea-going laser Raman spectrometer was used to obtain in situ Raman spectra of natural gas hydrates and natural gas venting from the seafloor. This was the first in situ analysis of gas hydrates on the seafloor. The hydrate spectra were compared to laboratory analyses performed at the Center for Hydrate Research, Colorado School of Mines. The natural gas spectra were compared to MBARI gas chromatography (GC) analyses of gas samples collected at the same site. DORISS (Deep Ocean Raman In Situ Spectrometer) is a laboratory model laser Raman spectrometer from Kaiser Optical Systems, Inc modified at MBARI for deployment in the deep ocean. It has been successfully deployed to depths as great as 3600 m. Different sampling optics provide flexibility in adapting the instrument to a particular target of interest. An immersion optic was used to analyze natural gas venting from the seafloor at South Hydrate Ridge ( ˜780 m depth). An open-bottomed cube was placed over the vent to collect the gas. The immersion optic penetrated the side of the cube as did a small heater used to dissociate any hydrate formed during sample collection. To analyze solid hydrates at both South and North Hydrate Ridge ( ˜590 m depth), chunks of hydrate were excavated from the seafloor and collected in a glass cylinder with a mesh top. A stand-off optic was used to analyze the hydrate inside the cylinder. Due to the partial opacity of the hydrate and the small focal volume of the sampling optic, a precision underwater positioner (PUP) was used to focus the laser spot onto the hydrate. PUP is a stand-alone system with three degrees-of-freedom, capable of moving the DORISS probe head with a precision of 0.1 mm. In situ Raman analyses of the gas indicate that it is primarily methane. This is verified by GC analyses of samples collected from the same site. Other minor constituents (such as CO2 and higher hydrocarbons) are present but may be in

  14. Properties of samples containing natural gas hydrate from the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well, determined using Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI)

    Science.gov (United States)

    Winters, W.J.

    1999-01-01

    As part of an ongoing laboratory study, preliminary acoustic, strength, and hydraulic conductivity results are presented from a suite of tests conducted on four natural-gas-hydrate-containing samples from the Mackenzie Delta JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well. The gas hydrate samples were preserved in pressure vessels during transport from the Northwest Territories to Woods Hole, Massachusetts, where multistep tests were performed using GHASTLI (Gas Hydrate And Sediment Test Laboratory Instrument), which recreates pressure and temperature conditions that are stable for gas hydrate. Properties and changes in sediment behaviour were measured before, during, and after controlled gas hydrate dissociation. Significant amounts of gas hydrate occupied the sample pores and substantially increased acoustic velocity and shear strength.

  15. First Study of Poly(3-Methylene-2-Pyrrolidone) as a Kinetic Hydrate Inhibitor

    DEFF Research Database (Denmark)

    Abrahamsen, Eirin; Heyns, Ingrid Marié; von Solms, Nicolas

    2017-01-01

    Formation of gas hydrates is a problem in the petroleum industry where the gas hydrates can cause blockage of the flowlines. Kinetic hydrate inhibitors (KHIs) are water-soluble polymers, sometimes used in combination synergistically or with non-polymeric synergists, that are used to prevent gas h...... are preferable in KHI polymers as long as they are water-soluble at hydrate-forming temperatures.......Formation of gas hydrates is a problem in the petroleum industry where the gas hydrates can cause blockage of the flowlines. Kinetic hydrate inhibitors (KHIs) are water-soluble polymers, sometimes used in combination synergistically or with non-polymeric synergists, that are used to prevent gas...... hydrate blockages. They have been used in the field successfully since 1995. In this paper, we present the first KHI results for the polymer, poly(3-methylene-2-pyrrolidone) (P(3M2P)), which is structurally similar to poly(N-vinylpyrrolidone) (PVP), one of the first KHIs to be discovered. 3M2P polymers...

  16. Global Assessment of Methane Gas Hydrates: Outreach for the public and policy makers

    Science.gov (United States)

    Beaudoin, Yannick

    2010-05-01

    The United Nations Environment Programme (UNEP), via its official collaborating center in Norway, GRID-Arendal, is in the process of implementing a Global Assessment of Methane Gas Hydrates. Global reservoirs of methane gas have long been the topic of scientific discussion both in the realm of environmental issues such as natural forces of climate change and as a potential energy resource for economic development. Of particular interest are the volumes of methane locked away in frozen molecules known as clathrates or hydrates. Our rapidly evolving scientific knowledge and technological development related to methane hydrates makes these formations increasingly prospective to economic development. In addition, global demand for energy continues, and will continue to outpace supply for the foreseeable future, resulting in pressure to expand development activities, with associated concerns about environmental and social impacts. Understanding the intricate links between methane hydrates and 1) natural and anthropogenic contributions to climate change, 2) their role in the carbon cycle (e.g. ocean chemistry) and 3) the environmental and socio-economic impacts of extraction, are key factors in making good decisions that promote sustainable development. As policy makers, environmental organizations and private sector interests seek to forward their respective agendas which tend to be weighted towards applied research, there is a clear and imminent need for a an authoritative source of accessible information on various topics related to methane gas hydrates. The 2008 United Nations Environment Programme Annual Report highlighted methane from the Arctic as an emerging challenge with respect to climate change and other environmental issues. Building upon this foundation, UNEP/GRID-Arendal, in conjunction with experts from national hydrates research groups from Canada, the US, Japan, Germany, Norway, India and Korea, aims to provide a multi-thematic overview of the key

  17. TOUGH+HYDRATE v1.2 User's Manual: A Code for the Simulation of System Behavior in Hydrate-Bearing Geologic Media

    Energy Technology Data Exchange (ETDEWEB)

    Moridis, George J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kowalsky, Michael B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Pruess, Karsten [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2012-08-01

    TOUGH+HYDRATE v1.2 is a code for the simulation of the behavior of hydratebearing geologic systems, and represents the second update of the code since its first release [Moridis et al., 2008]. By solving the coupled equations of mass and heat balance, TOUGH+HYDRATE can model the non-isothermal gas release, phase behavior and flow of fluids and heat under conditions typical of common natural CH4-hydrate deposits (i.e., in the permafrost and in deep ocean sediments) in complex geological media at any scale (from laboratory to reservoir) at which Darcy’s law is valid. TOUGH+HYDRATE v1.2 includes both an equilibrium and a kinetic model of hydrate formation and dissociation. The model accounts for heat and up to four mass components, i.e., water, CH4, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dissociation or formation, phase changes and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects and inhibitor-induced effects. TOUGH+HYDRATE is a member of TOUGH+, the successor to the TOUGH2 [Pruess et al., 1991] family of codes for multi-component, multiphase fluid and heat flow developed at the Lawrence Berkeley National Laboratory. It is written in standard FORTRAN 95/2003, and can be run on any computational platform (workstation, PC, Macintosh) for which such compilers are available.

  18. High-pressure studies on a new superconducting clathrate: Ba sub 6 Ge sub 2 sub 5

    CERN Document Server

    Yuan, H Q; Carrillo-Cabrera, W; Paschen, S; Sparn, G; Baenitz, M; Grin, Y; Steglich, F

    2002-01-01

    The effect of pressure on the low-temperature states of the newly discovered clathrate Ba sub 6 Ge sub 2 sub 5 is investigated by means of measurements of the electrical resistivity. At ambient pressure, Ba sub 6 Ge sub 2 sub 5 undergoes a two-step structural phase transition between 230 and 180 K from metallic behaviour to a high-resistivity state characterized by a mean free path of about 3 A. Interestingly, a Bardeen-Cooper-Schrieffer-like (BCS-like) superconducting transition occurs at T sub C approx 0.24 K from the resulting 'bad metal'. With increasing pressure, the structural phase transition is depressed but T sub C increases drastically. T sub C reaches a maximum value of 3.85 K at the critical pressure p sub C approx 2.8 GPa, where the structural distortion is completely suppressed and the system exhibits metallic behaviour. Higher pressures lead to a slight decrease of T sub C.

  19. Magnetic behavior of cobalt bromide hydrates including a deuterated form

    Energy Technology Data Exchange (ETDEWEB)

    DeFotis, G.C., E-mail: gxdefo@wm.edu; Hampton, A.S.; Van Dongen, M.J.; Komatsu, C.H.; DeSanto, C.L.; Davis, C.M.

    2017-04-15

    The magnetic properties of little examined CoBr{sub 2}• 2H{sub 2}O and new CoBr{sub 2}• H{sub 2}O and CoBr{sub 2}• D{sub 2}O are studied. Curie-Weiss fits, χ{sub M}=C/(T-θ), yield θ of −9.9, 9.4 and 10.0 K, respectively, over a 30–80 K linear range for each. Higher temperature data are fit assuming two moderately separated low lying Kramers doublets, with exchange accounted for in a mean-field approximation. Susceptibility maxima appear at 9.5, 15.4 and 15.5 K, with χ{sub max} of 0.163, 0.375 and 0.435 emu/mol, respectively. Antiferromagnetic ordering is estimated to occur at 9.0, 13.7 and 13.8 K, in the same order. The ratio T{sub c}/T{sub max} is 0.95, 0.89 and 0.89, respectively, suggesting little low dimensional magnetic character in singly hydrated systems. Data at lower temperatures for the dihydrate are fit with an antiferromagnetic 3D-Ising model. For singly hydrated systems the large size of χ{sub max} prevents this; weakened interchain antiferromagnetic interactions yield enhanced susceptibility maxima. Magnetization data exhibit field induced transitions near 13.5 kG for the dihydrate, and near 6.5 kG for singly hydrated systems with enhanced hysteresis. These transitions are interpreted as metamagnetic in nature. - Highlights: • CoBr{sub 2}• 2H{sub 2}O has a larger susceptibility maximum at lower temperature than CoCl{sub 2}• 2H{sub 2}O. • Enhanced antiferromagnetic susceptibility maxima occur in CoBr{sub 2}·H{sub 2}O and CoBr{sub 2}• D{sub 2}O. • Metamagnetic transitions occur at much lower fields in monohydrates than dehydrate. • Interchain antiferromagnetic exchange is weaker in monohydrates than dehydrate. • CoBr{sub 2}• H{sub 2}O exhibit spin glass behavior similar to that seen previously in CoCl{sub 2}·H{sub 2}O.

  20. Molecular Simulation Models of Carbon Dioxide Intercalation in Hydrated Sodium Montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Myshakin, Evgeniy [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Saidi, Wissam [Univ. of Pittsburgh, PA (United States); Romanov, Vyacheslav [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Cygan, Randall [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jordan, Kenneth [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Univ. of Pittsburgh, PA (United States); Guthrie, George [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-22

    In this study, classical molecular dynamics simulations and density functional theory (DFT)-based molecular dynamics are used to elucidate the process of CO2 intercalation into hydrated Na-montmorillonite at P-T conditions relevant to geological formations suitable for CO2 storage. Of particular interest are the structural and transport properties of interlayer species after CO2 intercalation. The conducted simulations allowed the research team to quantify expansion/contraction of smectite as a function of CO2 and H2O compositions. The resulting swelling curves can be used to gauge the amount of stored CO2, compare it to the experiment, and estimate changes in geomechanical properties of the storage formation. The obtained results showed that the infrared signal of the asymmetric stretch vibration of CO2 molecule is extremely sensitive to the solvent environment. The extent of the frequency shift relative to the gas-phase value can be used to probe hydration level in the interlayer with intercalated CO2. Interaction of supercritical CO2 with brine in deep geological formations promotes an increase of hydrophobicity of clay surfaces. As a result of wettability alteration, estimated diffusion constants of CO2 and H2O increase with the increased CO2 load; this can contribute to faster migration of CO2 throughout the formation.

  1. Detailed evaluation of gas hydrate reservoir properties using JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well downhole well-log displays

    Science.gov (United States)

    Collett, T.S.

    1999-01-01

    The JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well project was designed to investigate the occurrence of in situ natural gas hydrate in the Mallik area of the Mackenzie Delta of Canada. Because gas hydrate is unstable at surface pressure and temperature conditions, a major emphasis was placed on the downhole logging program to determine the in situ physical properties of the gas-hydrate-bearing sediments. Downhole logging tool strings deployed in the Mallik 2L-38 well included the Schlumberger Platform Express with a high resolution laterolog, Array Induction Imager Tool, Dipole Shear Sonic Imager, and a Fullbore Formation Microlmager. The downhole log data obtained from the log- and core-inferred gas-hydrate-bearing sedimentary interval (897.25-1109.5 m log depth) in the Mallik 2L-38 well is depicted in a series of well displays. Also shown are numerous reservoir parameters, including gas hydrate saturation and sediment porosity log traces, calculated from available downhole well-log and core data. The gas hydrate accumulation delineated by the Mallik 2L-38 well has been determined to contain as much as 4.15109 m3 of gas in the 1 km2 area surrounding the drill site.

  2. Structure and physical properties of type-I clathrate solid-solution Ba8PtxGe46-x-y□y (□=vacancy)

    International Nuclear Information System (INIS)

    Melnychenko-Koblyuk, N.; Grytsiv, A.; Rogl, P.; Rotter, M.; Lackner, R.; Bauer, E.; Fornasari, L.; Marabelli, F.; Giester, G.

    2007-01-01

    Formation, crystal chemistry, and physical properties were investigated for the solid-solution Ba 8 Pt x Ge 46-x-y □ y (□ is a vacancy) deriving from binary clathrate Ba 8 Ge 43 □ 3 with a solubility limit of ∼3.5 Pt atoms/f.u. at T=800 deg. C. Structural investigations throughout the homogeneity region confirm isotypism with the cubic primitive clathrate type-I structure (space group type Pm3n) and lattice parameters ranging from a=1.0657(2) nm for Ba 8 Ge 43 □ 3 to a=1.0752(2) nm for Ba 8 Pt 3.5 Ge 41.5 □ 1.0 . Phase relations for the region concerning the clathrate solution were derived at subsolidus temperatures as well as at 800 deg. C. Transport properties evidence electrons as the majority charge carriers in the system with a slight dependency on the Pt content. The system is located close to a semiconducting regime with a gap in the electronic density of states of a few thousand K. No low temperature maximum is obvious from thermal conductivity which is dominated by the lattice contribution. Thermal conductivity furthermore documents a high efficiency of phonon scattering on vacancies

  3. The melting curve of tetrahydrofuran hydrate in D2O

    International Nuclear Information System (INIS)

    Hanley, H.J.M.; Meyers, G.J.; White, J.W.; Sloan, E.D.

    1989-01-01

    Melting points for the tetrahydrofuran/D 2 O hydrate in equilibrium with the air-saturated liquid at atmospheric pressure are reported. The melting points were measured by monitoring the absorbance of the solution. Overall, the melting-point phase boundary curve is about 2.5 K greater than the corresponding curve for the H 2 O hydrate, with a congruent melting temperature of 281 ± 0.5 K at a D 2 O mole fraction of 0.936. The phase boundary is predicted to within 5% if the assumption is made that the THF occupancy in the D 2 O and H 2 O hydrates is the same. The authors measure an occupancy of 99.9%. The chemical potential of the empty lattice in D 2 O is estimated to be 5% greater than in H 2 O

  4. Use of hydrate for sequestering CO{sub 2} in the deep ocean

    Energy Technology Data Exchange (ETDEWEB)

    North, W.J.; Morgan, J.J. [California Inst. of Technology, Pasadena, CA (United States); Spencer, D.F. [Electric Power Research Inst., Palo Alto, CA (United States)] [and others

    1993-12-31

    Tremendous amounts of CO{sub 2} are accumulating annually in the atmosphere (ca 3 gigatons of carbon per year at present). Prevention or significant amelioration of this atmospheric buildup will obviously require a grand scale corrective activity. A potential solution to the problem might involve sequestering CO{sub 2} in an alternate reservoir. The ocean immediately comes to mind as a reservoir of appropriate magnitude to accommodate the huge quantities of CO{sub 2} involved. Presumably there would be a trade-off: we would achieve a semi-clean atmosphere for an as- yet-to-be-determined impact in the ocean. Minimizing any oceanic impacts would enhance attractiveness of the trade-off.

  5. Ab initio molecular dynamics simulations reveal localization and time evolution dynamics of an excess electron in heterogeneous CO{sub 2}–H{sub 2}O systems

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ping; Zhao, Jing; Liu, Jinxiang; Zhang, Meng; Bu, Yuxiang, E-mail: byx@sdu.edu.cn [School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100 (China)

    2014-01-28

    In view of the important implications of excess electrons (EEs) interacting with CO{sub 2}–H{sub 2}O clusters in many fields, using ab initio molecular dynamics simulation technique, we reveal the structures and dynamics of an EE associated with its localization and subsequent time evolution in heterogeneous CO{sub 2}–H{sub 2}O mixed media. Our results indicate that although hydration can increase the electron-binding ability of a CO{sub 2} molecule, it only plays an assisting role. Instead, it is the bending vibrations that play the major role in localizing the EE. Due to enhanced attraction of CO{sub 2}, an EE can stably reside in the empty, low-lying π{sup *} orbital of a CO{sub 2} molecule via a localization process arising from its initial binding state. The localization is completed within a few tens of femtoseconds. After EE trapping, the ∠OCO angle of the core CO{sub 2}{sup −} oscillates in the range of 127°∼142°, with an oscillation period of about 48 fs. The corresponding vertical detachment energy of the EE is about 4.0 eV, which indicates extreme stability of such a CO{sub 2}-bound solvated EE in [CO{sub 2}(H{sub 2}O){sub n}]{sup −} systems. Interestingly, hydration occurs not only on the O atoms of the core CO{sub 2}{sup −} through formation of O⋯H–O H–bond(s), but also on the C atom, through formation of a C⋯H–O H–bond. In the latter binding mode, the EE cloud exhibits considerable penetration to the solvent water molecules, and its IR characteristic peak is relatively red-shifted compared with the former. Hydration on the C site can increase the EE distribution at the C atom and thus reduce the C⋯H distance in the C⋯H–O H–bonds, and vice versa. The number of water molecules associated with the CO{sub 2}{sup −} anion in the first hydration shell is about 4∼7. No dimer-core (C{sub 2}O{sub 4}{sup −}) and core-switching were observed in the double CO{sub 2} aqueous media. This work provides molecular dynamics

  6. Confined release of CO{sub 2} into the ocean

    Energy Technology Data Exchange (ETDEWEB)

    Adams, E.E.; Zhang, X.Y.; Herzog, H.J. [Massachusetts Inst. of Technology, Cambridge, MA (United States)] [and others

    1993-12-31

    To help reduce global warming, it has been proposed to sequester some CO{sub 2} in the deep ocean. However, current pipe technology is limited to about 600-650 m{sup 4}, so deeper transport requires other means. Recently, it was suggested that CO{sub 2} could be released at depths of 200 - 400 m as a concentrated seawater solution. The dense solution would form a negatively buoyant gravity current and sink to greater depth. In the following we expand our previous calculations showing that an unconfined release of CO{sub 2} will not create sufficient concentration or negative buoyancy. However, release of either compressed gaseous or liquid CO{sub 2} into an appropriately designed confinement vessel could produce sufficient concentration to transport the current to deeper water. Furthermore, such a scheme may facilitate formation of CO{sub 2} hydrate particles that are heavier than seawater, causing further sinking. A recently completed Research Needs assessment study which we conducted for DOE concludes that shallow water disposal of CO{sub 2} may be the most promising CO{sub 2} disposal option.

  7. Effect of rice husk ash addition on CO2 capture behavior of calcium-based sorbent during calcium looping cycle

    International Nuclear Information System (INIS)

    Li, Yingjie; Zhao, Changsui; Ren, Qiangqiang; Duan, Lunbo; Chen, Huichao; Chen, Xiaoping

    2009-01-01

    Rice husk ash/CaO was proposed as a CO 2 sorbent which was prepared by rice husk ash and CaO hydration together. The CO 2 capture behavior of rice husk ash/CaO sorbent was investigated in a twin fixed bed reactor system, and its apparent morphology, pore structure characteristics and phase variation during cyclic carbonation/calcination reactions were examined by SEM-EDX, N 2 adsorption and XRD, respectively. The optimum preparation conditions for rice husk ash/CaO sorbent are hydration temperature of 75 C, hydration time of 8 h, and mole ratio of SiO 2 in rice husk ash to CaO of 1.0. The cyclic carbonation performances of rice husk ash/CaO at these preparation conditions were compared with those of hydrated CaO and original CaO. The temperature at 660 C-710 C is beneficial to CO 2 absorption of rice husk ash/CaO, and it exhibits higher carbonation conversions than hydrated CaO and original CaO during multiple cycles at the same reaction conditions. Rice husk ash/CaO possesses better anti-sintering behavior than the other sorbents. Rice husk ash exhibits better effect on improving cyclic carbonation conversion of CaO than pure SiO 2 and diatomite. Rice husk ash/CaO maintains higher surface area and more abundant pores after calcination during the multiple cycles; however, the other sorbents show a sharp decay at the same reaction conditions. Ca 2 SiO 4 found by XRD detection after calcination of rice husk ash/CaO is possibly a key factor in determining the cyclic CO 2 capture behavior of rice husk ash/CaO. (author)

  8. Methane hydrate stability and anthropogenic climate change

    Directory of Open Access Journals (Sweden)

    D. Archer

    2007-07-01

    Full Text Available Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO2.

    Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.

    The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release as much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

  9. Raman scattering of type-I clathrate compounds

    International Nuclear Information System (INIS)

    Takasu, Y.; Hasegawa, T.; Ogita, N.; Udagawa, M.; Avila, M.A.; Takabatake, T.

    2006-01-01

    Lattice dynamical properties of the type-I clathrate compounds of A 8 Ga 16 Ge 30 (A=Eu, Sr, Ba) have been investigated by Raman scattering. We are successful in the assignment of the observed Raman active phonons to proper symmetry and are able to separate the guest atom origin modes from framework origin modes for the first time experimentally. From the measurements of temperature dependence of the guest origin peaks, we also demonstrate the difference of the behavior of the guest atom at high temperature and low temperature

  10. Atmospheric pCO2 reconstructed across five early Eocene global warming events

    Science.gov (United States)

    Cui, Ying; Schubert, Brian A.

    2017-11-01

    Multiple short-lived global warming events, known as hyperthermals, occurred during the early Eocene (56-52 Ma). Five of these events - the Paleocene-Eocene Thermal Maximum (PETM or ETM1), H1 (or ETM2), H2, I1, and I2 - are marked by a carbon isotope excursion (CIE) within both marine and terrestrial sediments. The magnitude of CIE, which is a function of the amount and isotopic composition of carbon added to the ocean-atmosphere system, varies significantly between marine versus terrestrial substrates. Here we use the increase in carbon isotope fractionation by C3 land plants in response to increased pCO2 to reconcile this difference and reconstruct a range of background pCO2 and peak pCO2 for each CIE, provided two potential carbon sources: methane hydrate destabilization and permafrost-thawing/organic matter oxidation. Although the uncertainty on each pCO2 estimate using this approach is low (e.g., median uncertainty = + 23% / - 18%), this work highlights the potential for significant systematic bias in the pCO2 estimate resulting from sampling resolution, substrate type, diagenesis, and environmental change. Careful consideration of each of these factors is required especially when applying this approach to a single marine-terrestrial CIE pair. Given these limitations, we provide an upper estimate for background early Eocene pCO2 of 463 +248/-131 ppmv (methane hydrate scenario) to 806 +127/-104 ppmv (permafrost-thawing/organic matter oxidation scenario). These results, which represent the first pCO2 proxy estimates directly tied to the Eocene hyperthermals, demonstrate that early Eocene warmth was supported by background pCO2 less than ∼3.5× preindustrial levels and that pCO2 > 1000 ppmv may have occurred only briefly, during hyperthermal events.

  11. International Collaboration on CO2 Sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Peter H. Israelsson; E. Eric Adams

    2007-06-30

    On December 4, 1997, the US Department of Energy (USDOE), the New Energy and Industrial Technology Development Organization of Japan (NEDO), and the Norwegian Research Council (NRC) entered into a Project Agreement for International Collaboration on CO{sub 2} Ocean Sequestration. Government organizations from Japan, Canada, and Australia, and a Swiss/Swedish engineering firm later joined the agreement, which outlined a research strategy for ocean carbon sequestration via direct injection. The members agreed to an initial field experiment, with the hope that if the initial experiment was successful, there would be subsequent field evaluations of increasingly larger scale to evaluate environmental impacts of sequestration and the potential for commercialization. The evolution of the collaborative effort, the supporting research, and results for the International Collaboration on CO{sub 2} Ocean Sequestration were documented in almost 100 papers and reports, including 18 peer-reviewed journal articles, 46 papers, 28 reports, and 4 graduate theses. These efforts were summarized in our project report issued January 2005 and covering the period August 23, 1998-October 23, 2004. An accompanying CD contained electronic copies of all the papers and reports. This report focuses on results of a two-year sub-task to update an environmental assessment of acute marine impacts resulting from direct ocean sequestration. The approach is based on the work of Auerbach et al. [6] and Caulfield et al. [20] to assess mortality to zooplankton, but uses updated information concerning bioassays, an updated modeling approach and three modified injection scenarios: a point release of negatively buoyant solid CO{sub 2} hydrate particles from a moving ship; a long, bottom-mounted diffuser discharging buoyant liquid CO{sub 2} droplets; and a stationary point release of hydrate particles forming a sinking plume. Results suggest that in particular the first two discharge modes could be

  12. Composition and method for hydrogen storage

    Science.gov (United States)

    Mao, Wendy L. (Inventor); Mao, Ho-Kwang (Inventor)

    2004-01-01

    A method for hydrogen storage includes providing water and hydrogen gas to a containment volume, reducing the temperature of the water and hydrogen gas to form a hydrogen clathrate at a first cryogenic temperature and a first pressure and maintaining the hydrogen clathrate at second cryogenic temperature within a temperature range of up to 250 K to effect hydrogen storage. The low-pressure hydrogen hydrate includes H.sub.2 O molecules, H.sub.2 molecules and a unit cell including polyhedron cages of hydrogen-bonded frameworks of the H.sub.2 O molecules built around the H.sub.2 molecules.

  13. Process design of a new injection method of liquid CO2 at the intermediate depths in the ocean using a static mixer

    International Nuclear Information System (INIS)

    Tajima, Hideo; Yamasaki, Akihiro; Kiyono, Fumio

    2005-01-01

    Process design for a new injection method of liquid CO 2 using a static mixer was conducted based on laboratory experimental results on the formation process of liquid CO 2 drops covered with hydrate film by a Kenics-type static mixer, and numerical simulation of the liquid CO 2 drops at 500 and 1500 m. The Sauter Mean Diameter (SMD) of the liquid CO 2 drops covered with hydrate film was dramatically decreased with the use of the static mixer; empirical equations were obtained for the SMD, and also the maximum and minimum diameters of the liquid CO 2 drops for a given flow velocity (Weber number, We). The ascending and dissolving behavior of a liquid CO 2 drop with hydrate released in the ocean at an intermediate depth was numerically simulated, and the maximum drop diameter to avoid evaporation of the drop before complete dissolution was estimated. Based on these results, scaling up of the static mixer was conducted by assuming a disposal process of CO 2 emitted from a 100-MW thermal power plant, and the mixer diameter was determined as a function of the given SMD. Moreover, the power consumption of the static mixer was evaluated and found to be almost negligible. (author)

  14. Pressure-induced phase transformations in the Ba8Si46 clathrate

    DEFF Research Database (Denmark)

    Yang, Lirong; Ma, Y.M.; Iitaka, T.

    2006-01-01

    The nature of isostructural transformations of a type-I Ba8Si46 clathrate has been studied by in situ high-pressure angle-dispersive x-ray powder diffraction using liquid He as pressure transmitting medium. The good quality of the diffraction data permitted refinement of structural and thermal...

  15. Enhancement of CO Evolution by Modification of Ga2O3 with Rare-Earth Elements for the Photocatalytic Conversion of CO2 by H2O.

    Science.gov (United States)

    Tatsumi, Hiroyuki; Teramura, Kentaro; Huang, Zeai; Wang, Zheng; Asakura, Hiroyuki; Hosokawa, Saburo; Tanaka, Tsunehiro

    2017-12-12

    Modification of the surface of Ga 2 O 3 with rare-earth elements enhanced the evolution of CO as a reduction product in the photocatalytic conversion of CO 2 using H 2 O as an electron donor under UV irradiation in aqueous NaHCO 3 as a pH buffer, with the rare-earth species functioning as a CO 2 capture and storage material. Isotope experiments using 13 CO 2 as a substrate clearly revealed that CO was generated from the introduced gaseous CO 2 . In the presence of the NaHCO 3 additive, the rare-earth (RE) species on the Ga 2 O 3 surface are transformed into carbonate hydrates (RE 2 (CO 3 ) 3 ·nH 2 O) and/or hydroxycarbonates (RE 2 (OH) 2(3-x) (CO 3 ) x ) which are decomposed upon photoirradiation. Consequently, Ag-loaded Yb-modified Ga 2 O 3 exhibits much higher activity (209 μmol h -1 of CO) than the pristine Ag-loaded Ga 2 O 3 . The further modification of the surface of the Yb-modified Ga 2 O 3 with Zn afforded a selectivity toward CO evolution of 80%. Thus, we successfully achieved an efficient Ag-loaded Yb- and Zn-modified Ga 2 O 3 photocatalyst with high activity and controllable selectivity, suitable for use in artificial photosynthesis.

  16. CO2 sequestration using principles of shell formation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung-Woo; Jang, Young-Nam [CO2 Sequestration Research Department, Korea Institute of Geoscience and Mineral Resources (Korea, Republic of); Lee, Si-Hyun; Lim, Kyoung-Soo; Jeong, Soon-Kwan [Energy Conservation Research Department of Clean Energy System Research Center, Korea Institute of Energy Research (Korea, Republic of)

    2011-06-15

    The biomimetic sequestration of carbon dioxide to reduce the CO2 emitted into the atmosphere is introduced in this paper. Bivalve shells are used as a good model of CO2 sequestration in this paper, because the shell is derived from the calcium ions and CO2 in seawater. Carbonic anhydrase, hemocyte from diseased shell (HDS) and extrapallial fluid (EFP) are involved in shell formation. This paper compares the soluble protein extracted from Crassostrea gigas with bovine carbonic anhydrase II in terms of their ability to promote CO2 hydration and the production of calcium precipitates. The result demonstrates that HDS has more functional groups to bind calcium ions in aqueous systems, and a different process of calcium precipitation, than does bovine carbonic anhydrase II. To understand molecular weight and secondary protein structure, mass-spectroscopic analysis (MALDI-TOF) and circular dichroism (CD) analysis were used. With regard to EPF, EPF related to shell formation is composed of several fractions and plays a role in sequestration of CO2.

  17. The role of pH in the vapor hydration at 175 °C of the French SON68 glass

    International Nuclear Information System (INIS)

    Ait Chaou, Abdelouahed; Abdelouas, Abdesselam; El Mendili, Yassine; Martin, Christelle

    2017-01-01

    The French simulated nuclear waste SON68 glass was altered in the presence of water vapor at 175 °C and 98% of relative humidity under several atmospheres (NH_3, H_2S, CO_2 and argon). The objectives were to study the role of pH on hydration kinetics and secondary phases formation. The hydration was followed by infrared spectroscopy and the nature and extent of alteration products were determined by characterizing the reacted glass surface with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), μ-Raman spectroscopy and X-ray diffraction (XRD). The glass hydration/alteration rate clearly increased with increasing pH, that is controlled by the gas atmosphere, as the following: NH_3 > Ar > CO_2 > H_2S. This can directly be linked to the secondary phases precipitated on the glass surface. Hence, the major alteration products observed at high pH (under NH_3 and Ar) are analcime and Ca-silicates hydrates (CSH) while at low pH (under CO_2 and H_2S) only a hydrated gel layer was identified. - Highlights: • The vapor hydration study of the SON68 glass under geological conditions. • The secondary phases formation in the alteration of SON68 glass. • The pH effect on the alteration kinetics of glass.

  18. Is Br2 hydration hydrophobic?

    Science.gov (United States)

    Alcaraz-Torres, A; Gamboa-Suárez, A; Bernal-Uruchurtu, M I

    2017-02-28

    The spectroscopic properties of bromine in aqueous systems suggest it can behave as either hydrophilic or hydrophobic solute. In small water clusters, the halogen bond and the hydrogen-halogen interaction are responsible for its specific way of binding. In water hydrates, it is efficiently hosted by two different cages forming the crystal structure and it has been frequently assumed that there is little or no interaction between the guest and the host. Bromine in liquid solution poses a challenging question due to its non-negligible solubility and the large blue shift measured in its absorption spectra. Using a refined semi-empirical force field, PM3-PIF, we performed a Born-Oppenheimer molecular dynamics study of bromine in liquid water. Here we present a detailed study in which we retrieved the most representative hydration structures in terms of the most frequent positions around bromine and the most common water orientations. Albeit being an approximate description of the total hydration phenomenon, it captures the contribution of the leading molecular interactions in form of the recurrent structures. Our findings confirm that the spectroscopic signature is mainly caused by the closest neighbors. The dynamics of the whole first hydration shell strongly suggests that the external molecules in that structure effectively isolate the bulk from the presence of bromine. The solvation structure fluctuates from a hydrophilic to a hydrophobic-like environment along the studied trajectory.

  19. Microbial community in a sediment-hosted CO(2) lake of the southern Okinawa Trough hydrothermal system RID C-8303-2011

    DEFF Research Database (Denmark)

    Inagaki, Fumio; Kuypers, Marcel M. M.; Tsunogai, Urumu

    2006-01-01

    pavements above the CO(2) lake, decreasing to strikingly low cell numbers (107 CM-3) at the liquid CO(2)/CO(2)-hydrate interface. The key groups in these sediments were as follows: (i) the anaerobic methanotrophic archaea ANME-2c and the Eel-2 group of Deltaproteobacteria and (ii) sulfur...

  20. Gas composition and isotopic geochemistry of cuttings, core, and gas hydrate from the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well

    Science.gov (United States)

    Lorenson, T.D.

    1999-01-01

    Molecular and isotopic composition of gases from the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well demonstrate that the in situ gases can be divided into three zones composed of mixtures of microbial and thermogenic gases. Sediments penetrated by the well are thermally immature; thus the sediments are probably not a source of thermogenic gas. Thermogenic gas likely migrated from depths below 5000 m. Higher concentrations of gas within and beneath the gas hydrate zone suggest that gas hydrate is a partial barrier to gas migration. Gas hydrate accumulations occur wholly within zone 3, below the base of permafrost. The gas in gas hydrate resembles, in part, the thermogenic gas in surrounding sediments and gas desorbed from lignite. Gas hydrate composition implies that the primary gas hydrate form is Structure I. However, Structure II stabilizing gases are more concentrated and isotopically partitioned in gas hydrate relative to the sediment hosting the gas hydrate, implying that Structure II gas hydrate may be present in small quantities.

  1. Advanced research and development of gas hydrate resources. R and D of exploration and others - R and D of excavation technologies and others - surveys/researches on methods of evaluating environmental effects - surveys/researches on application systems; Gas hydrate shigenka gijutsu sendo kenkyu kaihatsu. Tansa nado ni kansuru kenkyu kaihatsu / kussaku gijutsu nado ni kansuru kenkyu kaihatsu / kankyo eikyo hyokaho no chosa kenkyu / riyo system ni kansuru chosa kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    Gas hydrate is a clathrate compound in a gaseous molecule as the host, stable under relatively mild environments. It is deposited in the 600m or deeper sea bottoms to form the gas hydrate deposit and massively occurring in the sea areas around Japan. This deposit has been studied viewed from natural gas resources, causes for natural hazards and contribution to the global warming. This project excavates a well in the deposit, to study possibilities of the technologies for decomposing, fluidizing and lifting the hydrate as the gas source, and for establishing the natural gas transporting/mooring systems in which its characteristics are utilized. The R and D activities are directed to the 4 areas, (1) development of the exploration technologies to determine the deposit sea area, quantity and conditions, (2) development of the stable well-excavation technologies, (3) studies on the effects of gas production on the environments, and development of the system for predicting the effects, (4) and studies on the application systems. The item (3) finds out the transportation/storage system possibly more economical than the current freezing/liquefaction technologies. The item (3) has the development themes of evaluating the geohazards caused by excavation and gas production, and their effects on the ecological systems. (NEDO)

  2. A geometry-based simulation of the hydration of ions and small molecules

    International Nuclear Information System (INIS)

    Plumridge, T.H.

    2001-01-01

    The behaviour of solutes in water is of universal significance, but still not fully understood. This thesis provides details of a new computer simulation technique used to investigate the hydration of ions and small molecules. In contrast to conventional techniques such as molecular dynamics, this is a purely geometric method involving no forcefield or energy terms. Molecules of interest are modelled using crystallographic data to ensure that the structures are accurate. Water molecules are added randomly at any hydrogen bonding site in chains. At each addition the chain is rotated through all available space testing for the possibility of ring formation. The constraints used by the program to decide whether a ring should be conserved, i.e. whether the ring-forming hydrogen bond is viable were derived from a survey of (i) all available ice and clathrate hydrate structures and (ii) the hydrates of small biological molecules from the Cambridge Crystallographic Data Centre. If a ring forms, it is conserved and the process restarted with the addition of another random water. If the chain reaches a certain length and no hydrogen bonding opportunities are detected, the water chain is dissolved, and the process restarted. Using these techniques structure makers such as sulfate will readily allow structured water to form around them leading to large networks, whereas structure breakers such as urea will not allow any water chains to bridge the hydrogen bonding groups. The software has been tested with a set of twenty widely varying solutes and has produced results which generally agree with experimental data for structure makers and breakers, and also agrees well with traditional techniques such as molecular dynamics and Monte Carlo techniques. (author)

  3. Influence of limestone on the hydration of Portland cements

    International Nuclear Information System (INIS)

    Lothenbach, Barbara; Le Saout, Gwenn; Gallucci, Emmanuel; Scrivener, Karen

    2008-01-01

    The influence of the presence of limestone on the hydration of Portland cement was investigated. Blending of Portland cement with limestone was found to influence the hydrate assemblage of the hydrated cement. Thermodynamic calculations as well as experimental observations indicated that in the presence of limestone, monocarbonate instead of monosulfate was stable. Thermodynamic modelling showed that the stabilisation of monocarbonate in the presence of limestone indirectly stabilised ettringite leading to a corresponding increase of the total volume of the hydrate phase and a decrease of porosity. The measured difference in porosity between the 'limestone-free' cement, which contained less than 0.3% CO 2 , and a cement containing 4% limestone, however, was much smaller than calculated. Coupling of thermodynamic modelling with a set of kinetic equations which described the dissolution of the clinker, predicted quantitatively the amount of hydrates. The quantities of ettringite, portlandite and amorphous phase as determined by TGA and XRD agreed well with the calculated amounts of these phases after different periods of time. The findings in this paper show that changes in the bulk composition of hydrating cements can be followed by coupled thermodynamic models. Comparison between experimental and modelled data helps to understand in more detail the dominating processes during cement hydration

  4. In vivo predictive dissolution: transport analysis of the CO2 , bicarbonate in vivo buffer system.

    Science.gov (United States)

    Krieg, Brian J; Taghavi, Seyed Mohammad; Amidon, Gordon L; Amidon, Gregory E

    2014-11-01

    Development of an oral in vivo predictive dissolution medium for acid drugs with a pKa in the physiological range (e.g., Biopharmaceutics Classification System Class IIa) requires transport analysis of the complex in vivo CO2 /bicarbonate buffering system. In this report, we analyze this buffer system using hydrodynamically defined rotating disk dissolution. Transport analysis of drug flux was predicted using the film model approach of Mooney et al based on equilibrium assumptions as well as accounting for the slow hydration reaction, CO2 + H2 O → H2 CO3 . The accuracy of the models was compared with experimentally determined results using the rotating disk dissolution of ibuprofen, indomethacin, and ketoprofen. The equilibrium and slow hydration reaction rate models predict significantly different dissolution rates. The experimental results are more accurately predicted by accounting for the slow hydration reaction under a variety of pH and hydrodynamic conditions. Although the complex bicarbonate buffering system requires further consideration given its dynamic nature in vivo, a simplifying irreversible reaction (IRR) transport analysis accurately predicts in vitro rotating disk dissolution rates of several carboxylic acid drugs. This IRR transport model provides further insight into bicarbonate buffer and can be useful in developing more physiologically relevant buffer systems for dissolution testing. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  5. International research cooperation project. Assessment report on the R and D of the comprehensive development/utilization technology of energy of gas hydrate resource; Gas hydrate shigen no energy sogo kaihatsu riyo gijutsu no kenkyu kaihatsu hyoka hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    As to 'the R and D of the comprehensive development/utilization technology of gas hydrate resource,' assessment was conducted and reported from an aspect of the third party. This R and D is a timely project being aimed at establishing the basic technology on gas hydrate from both aspects of fundamental research and practical research. In the development of gas hydrate resource in the tundra zone, the development of measuring methods for thermal conductivity and dielectric constants advanced the establishment of a guide for exploration and possibilities of assessment of the resource amount. In the development/production, it can be said that the knowledge/information collected by exchanging methane in gas hydrate with CO2 means no needs for new supply of heat and also contributes to the isolation of CO2. As to the utilization technology, the results were rated very high also internationally of tackling the quantitative evaluation method at molecular levels of the gas included in hydrate using Raman spectroscopy to establish the industrial gas separation method using the low-temperature environment in the tundra zone. (NEDO)

  6. The infrared spectral properties of frozen volatiles. [in cometary nuclei

    Science.gov (United States)

    Fink, U.; Sill, G. T.

    1982-01-01

    Since Whipple's dirty snowball model of comet nuclei, it has been generally accepted that volatile ices help to explain cometary phenomena. The infrared spectral properties of many substances that are potential candidates for frozen volatiles in the solar system are being pursued; indeed some of these frozen materials have been found in the solar system: H2O, CO2, and SO2. A review of laboratory spectra in the range 1 to 20 microns of H2O, CO2, SO2, CH4, NH3, H2S, CO, NH4HS and NH3.H2O is presented. Both reflection spectra of thick frosts and transmission spectra of thin films are shown, and their main characteristics are described. Hydrates, clathrates, and composite spectra are discussed. When it is possible to observe the nuclei of comets at close range, it may be possible to identify frozen volatiles by their infrared spectra.

  7. Crystal water as the mol-ecular glue for obtaining different co-crystal ratios: the case of gallic acid tris-caffeine hexa-hydrate.

    Science.gov (United States)

    Vella-Zarb, L; Baisch, U

    2018-04-01

    The crystal structure of the hexa-hydrate co-crystal of gallic acid and caffeine, C 7 H 6 O 5 ·3C 8 H 10 N 4 O 2 ·6H 2 O or GAL3CAF·6H 2 O , is a remarkable example of the importance of hydrate water acting as structural glue to facilitate the crystallization of two components of different stoichiometries and thus to compensate an imbalance of hydrogen-bond donors and acceptors. The water mol-ecules provide the additional hydrogen bonds required to form a crystalline solid. Whereas the majority of hydrogen bonds forming the inter-molecular network between gallic acid and caffeine are formed by crystal water, only one direct classical hydrogen bond between two mol-ecules is formed between the carb-oxy-lic oxygen of gallic acid and the carbonyl oxygen of caffeine with d ( D ⋯ A ) = 2.672 (2) Å. All other hydrogen bonds either involve crystal water or utilize protonated carbon atoms as donors.

  8. Direct measurement of methane hydrate composition along the hydrate equilibrium boundary

    Science.gov (United States)

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2005-01-01

    The composition of methane hydrate, namely nW for CH 4??nWH2O, was directly measured along the hydrate equilibrium boundary under conditions of excess methane gas. Pressure and temperature conditions ranged from 1.9 to 9.7 MPa and 263 to 285 K. Within experimental error, there is no change in hydrate composition with increasing pressure along the equilibrium boundary, but nW may show a slight systematic decrease away from this boundary. A hydrate stoichiometry of n W = 5.81-6.10 H2O describes the entire range of measured values, with an average composition of CH4??5.99(??0.07) H2O along the equilibrium boundary. These results, consistent with previously measured values, are discussed with respect to the widely ranging values obtained by thermodynamic analysis. The relatively constant composition of methane hydrate over the geologically relevant pressure and temperature range investigated suggests that in situ methane hydrate compositions may be estimated with some confidence. ?? 2005 American Chemical Society.

  9. Accelerated weathering of limestone for CO2 mitigation: Opportunities for the stone and cement industries

    Science.gov (United States)

    Langer, William H.; San, Juan A.; Rau, Greg H.; Caldeira, Ken

    2009-01-01

    Large amounts of limestone fines co-produced during the processing of crushed limestone may be useful in the sequestration of carbon dioxide (CO2). Accelerated weathering of limestone (AWL) is proposed as a low-tech method to capture and sequester CO2 from fossil fuel-fired power plants and other point sources such as cement manufacturing. AWL reactants are readily available, inexpensive and environmentally benign. Waste CO2 is hydrated with water to produce carbonic acid. This reacts with and is neutralized by limestone fines, thus converting CO2 gas to dissolved calcium bicarbonate.

  10. Fiscal 2000 survey report. Feasibility study of reciprocative transportation system for carbon dioxide and natural gas utilizing gas hydrate; 2000 nendo gas hidrate wo riyosuru nisanka tanso to tennen gas no kogo yuso system no kanosei chosa hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-03-01

    A reciprocative CO2/CH{sub 4} transportation system will constitute a foundation on which minor gas fields may be made good use of in the Asia-Pacific region. For the construction of such a system, a survey is conducted into key technologies of separating CO2 from combustion exhaust with the aid of the hydrate process, reciprocative CO2/CH{sub 4} transportation with hydrate acting as medium, and subsurface CO2 storage and its utilization in minor gas fields or the like. The contents of the survey and the results fall in six areas, which are (1) the states of greenhouse gas reduction and natural gas utilization, (2) reciprocative CO2/CH{sub 4} transportation with hydrate acing as medium, (3) CO2 separation from combustion exhaust with the aid of the hydrate process, (4) reciprocative CO2/CH{sub 4} transportation with hydrate acing as medium, (5) subsurface CO2 storage and its utilization in minor gas fields, and (6) the establishment of a reciprocative CO2/CH{sub 4} transportation system and the evaluation of its cost performance. (NEDO)

  11. Sequestering CO2 by mineralization into useful nesquehonite-based products

    Directory of Open Access Journals (Sweden)

    Fredrik Paul Glasser

    2016-02-01

    Full Text Available The precipitation of magnesium hydroxy-carbonate hydrates has been suggested as a route to sequester CO2 into solids. We report the development of self-cementing compositions based on nesquehonite, MgCO3·3H2O, that are made from CO2-containing gas streams, the CO2 being separated from other gases by its high solubility in alkaline water, while magnesium is typically provided by waste desalination brines. Precipitation conditions are adjusted to optimize the formation of nesquehonite and the crystalline solid can readily be washed free of chloride. Products can be prepared to achieve self-cementation following two routes: (i thermal activation of the nesquehonite then rehydration of the precursor or (ii direct curing of a slurry of nesquehonite. The products thus obtained contain ~ 30 wt% CO2 and could form the basis for a new generation of lightweight, thermally insulating boards, blocks and panels, with sufficient strength for general construction.

  12. Hydration Properties of Ground Granulated Blast-Furnace Slag (GGBS Under Different Hydration Environments

    Directory of Open Access Journals (Sweden)

    Shuhua LIU

    2017-02-01

    Full Text Available The hydration properties of various cementitious materials containing Ground Granulated Blast-furnace Slag (GGBS, two alkali-activated slag cements (AAS-1 and AAS-2 in which sodium silicate and sodium hydroxide act as alkaline activators respectively, supersulfated cement (SSC and slag Portland cement(PSC, are compared with ordinary Portland cement (OPC to investigate the effect of activating environment on the hydration properties in this study by determining the compressive strength of the pastes, the hydration heat of binders within 96 hours, and the hydration products at age of 28 days. The results show that C-S-H gels are the main hydrated products for all cementitious systems containing GGBS. Ca(OH2 is the hydration products of OPC and PSC paste. However, ettringite and gypsum crystals instead of Ca(OH2 are detected in SSC paste. Additionally, tobermorite, a crystalline C-S-H, and calcite are hydrated products in AAS-1. Tobermorite, cowlesite and calcite are hydrated products of AAS-2 as well. Based on strength results, AAS-1 paste exhibits the highest compressive strength followed by POC, PSC, SSC in order at all testing ages and AAS-2 give the lowest compressive strength except for the early age at 3 days, which is higher than SSC but still lower than PSC. From hydration heat analysis, alkalinity in the reaction solution is a vital factor influencing the initial hydration rate and the initial hydration rate from higher to lower is AAS-2, AAS-1, OPC, PSC and SSC. Although AAS possesses a faster reaction rate in the initial hours, cumulative hydration heat of AAS is comparably lower than that of OPC, but higher than those of PSC and SSC in turn, which indicates that the hydration heat of clinkers is much higher than that of slag.DOI: http://dx.doi.org/10.5755/j01.ms.23.1.14934

  13. Hydrocarbon test in lower-layer atmosphere to predict deep-sea petroleum or hydrate in the Okinawa Trough: an example

    Institute of Scientific and Technical Information of China (English)

    Gong Jianming; Chen Jianwen; Li Gang; Zhang Xunhua; Li Jipeng; Huang Fulin

    2003-01-01

    Light hydrocarbon (methane, ethane, propane, butane and CO2) test and C isotopic analysis of CO2 are conducted for over 100 lower-layer atmospheric samples from the East China Sea slope and the Okinawa Trough. The results show that the lower-layer atmosphere mainly consists of CO2 and then of CH4, and the CO2 concentrations are calculated to have a high average value of 0.87 ω/10-2 ,about three times that of the regional background (0.3 ω/10-2). The result also shows that the average value of C isotope - 20.8 × 10 -3 is given to the CO2, inferring that it is inorganic gas.Thus, for the future ' s work in the Okinawa Trough, special attention should be paid to CO2 hydrate,which is very possibly an important hydrate type.

  14. The millennial atmospheric lifetime of anthropogenic CO2

    International Nuclear Information System (INIS)

    Archer, D.

    2008-01-01

    The notion is pervasive in the climate science community and in the public at large that the climate impacts of fossil fuel CO 2 release will only persist for a few centuries. This conclusion has no basis in theory or models of the atmosphere/ocean carbon cycle, which we review here. The largest fraction of the CO 2 recovery will take place on time scales of centuries, as CO 2 invades the ocean, but a significant fraction of the fossil fuel CO 2 , ranging in published models in the literature from 20-60%, remains airborne for a thousand years or longer. Ultimate recovery takes place on time scales of hundreds of thousands of years, a geologic longevity typically associated in public perceptions with nuclear waste. The glacial/interglacial climate cycles demonstrate that ice sheets and sea level respond dramatically to millennial-timescale changes in climate forcing. There are also potential positive feedbacks in the carbon cycle, including methane hydrates in the ocean, and peat frozen in permafrost, that are most sensitive to the long tail of the fossil fuel CO 2 in the atmosphere

  15. Crystal structure and thermoelectric properties of clathrate, Ba{sub 8}Ni{sub 3.5}Si{sub 42.0}: Small cage volume and large disorder of the guest atom

    Energy Technology Data Exchange (ETDEWEB)

    Roudebush, John H., E-mail: jhr@princeton.edu [Department of Chemistry, University of California, One Shields Ave., Davis, CA 95616 (United States); Orellana, Mike [Department of Chemistry, University of California, One Shields Ave., Davis, CA 95616 (United States); Bux, Sabah [Thermal Energy Conversion Technologies Group, Jet Propulsion Laboratory/California Institute of Technology, Pasadena, CA 91109 (United States); Yi Tanghong; Kauzlarich, Susan M. [Department of Chemistry, University of California, One Shields Ave., Davis, CA 95616 (United States)

    2012-08-15

    Samples with the type-I clathrate composition Ba{sub 8}Ni{sub x}Si{sub 46-x} have been synthesized and their structure and thermoelectric properties characterized. Microprobe analysis indicates the Ni incorporation to be 2.62{<=}x{<=}3.53. The x=3.5 phase crystallizes in the type-I clathrate structure (space group: Pm-3n) with a lattice parameter of 10.2813(3) A. The refined composition was Ba{sub 8}Ni{sub 3.5}Si{sub 42.0}, with small vacancies, 0.4 and 0.5 atoms per formula unit, at the 2a and 6c sites, respectively. The position of the Ba2 atom in the large cage was modeled using a 4-fold split position (24j site), displaced 0.18 A from the cage center (6d site). The volume of the large cage is calculated to be 146 A{sup 3}, smaller than other clathrates with similar cation displacement. The sample shows n-type behavior with a maximum of -50 {mu}V/K at 823 K above which the Seebeck coefficient decreases, suggesting mixed carriers. Lattice thermal conductivity, {kappa}{sub l}, is 55 mW/K above 600 K. - Graphical abstract: Seebeck coefficient and resistivity of the type-I clathrate Ba{sub 8}Ni{sub 3.5}Si{sub 41.0}. Structure show's large displacement of the Ba cation in the large cage (6c site). Highlights: Black-Right-Pointing-Pointer Crystal structure of the Ba{sub 8}Ni{sub 3.5}Si{sub 41.0} reported. Black-Right-Pointing-Pointer Vacancies at the 2a and 6c sites. Black-Right-Pointing-Pointer Large disorder of Ba guest atom, 0.18 A from cage center. Black-Right-Pointing-Pointer Structure is compared to Ba{sub 8}Si{sub 46} and other type-I clathrates. Black-Right-Pointing-Pointer Max Seebeck of -50.7 {mu}V/C at 798.4 K, thermal conductivity {approx}55 mW/K.

  16. An ab initio and AIM investigation into the hydration of 2-thioxanthine

    Directory of Open Access Journals (Sweden)

    Fossey John S

    2010-03-01

    Full Text Available Abstract Background Hydration is a universal phenomenon in nature. The interactions between biomolecules and water of hydration play a pivotal role in molecular biology. 2-Thioxanthine (2TX, a thio-modified nucleic acid base, is of significant interest as a DNA inhibitor yet its interactions with hydration water have not been investigated either computationally or experimentally. Here in, we reported an ab initio study of the hydration of 2TX, revealing water can form seven hydrated complexes. Results Hydrogen-bond (H-bond interactions in 1:1 complexes of 2TX with water are studied at the MP2/6-311G(d, p and B3LYP/6-311G(d, p levels. Seven 2TX...H2O hydrogen bonded complexes have been theoretically identified and reported for the first time. The proton affinities (PAs of the O, S, and N atoms and deprotonantion enthalpies (DPEs of different N-H bonds in 2TX are calculated, factors surrounding why the seven complexes have different hydrogen bond energies are discussed. The theoretical infrared and NMR spectra of hydrated 2TX complexes are reported to probe the characteristics of the proposed H-bonds. An improper blue-shifting H-bond with a shortened C-H bond was found in one case. NBO and AIM analysis were carried out to explain the formation of improper blue-shifting H-bonds, and the H-bonding characteristics are discussed. Conclusion 2TX can interact with water by five different H-bonding regimes, N-H...O, O-H...N, O-H...O, O-H...S and C-H...O, all of which are medium strength hydrogen bonds. The most stable H-bond complex has a closed structure with two hydrogen bonds (N(7-H...O and O-H...O, whereas the least stable one has an open structure with one H-bond. The interaction energies of the studied complexes are correlated to the PA and DPE involved in H-bond formation. After formation of H-bonds, the calculated IR and NMR spectra of the 2TX-water complexes change greatly, which serves to identify the hydration of 2TX.

  17. The stability evaluation of lime mud as transesterification catalyst in resisting CO2 and H2O for biodiesel production

    International Nuclear Information System (INIS)

    Li, Hui; Niu, Sheng-li; Lu, Chun-mei; Cheng, Shi-qing

    2015-01-01

    Highlights: • Lime mud (LM) is pretreated with calcination, hydration and desiccation. • The alkali solubility is the amount of alkali compounds dissolved in methanol. • The soluble alkali amount in LM700-H is higher than that of CaO–H. • LM700 possesses a stronger capability than CaO in resisting H 2 O and CO 2 . - Abstract: The most outstanding property of the heterogeneous transesterification catalysts is recyclable, but their catalytic activity may be depressed for the absorption of moisture (H 2 O) and carbon dioxide (CO 2 ) in air, especially for the basic ones. Lime mud (LM) is effective in catalyzing transesterification, yet its property in resisting H 2 O and CO 2 is indistinct, which should be emphasized. In this study, the LM based transesterification catalyst is prepared through calcinations. Then, it is hydrated and desiccated to simulate the contamination by H 2 O and CO 2 . Further, the fresh and the contaminated catalysts are characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Hammette indicator, Brunauer–Emmett–Teller (BET) surface area and soluble alkali examination, to reveal the mechanism of LM in resisting H 2 O and CO 2 . Meanwhile, the analytical grade calcium oxide (CaO) is chosen for comparison. Finally, to comprehensively investigate the influences of H 2 O and CO 2 on LM in catalyzing transesterification, the factors of the catalyst addition percentage, molar ratio of methanol to oil and transesterification temperature are evaluated

  18. Dynamics of Permafrost Associated Methane Hydrate in Response to Climate Change

    Science.gov (United States)

    You, K.; Flemings, P. B.

    2014-12-01

    The formation and melting of methane hydrate and ice are intertwined in permafrost regions. A shortage of methane supply leads to formation of hydrate only at depth, below the base of permafrost. We consider a system with the ground surface initially at 0 oC with neither ice nor hydrate present. We abruptly decrease the temperature from 0 to -10 oC to simulate the effect of marine regression/ global cooling. A low methane supply rate of 0.005 kg m-2 yr-1 from depth leads to distinct ice and hydrate layers: a 100 m continuous hydrate layer is present beneath 850 m at 80 k.y.. However, a high methane supply rate of 0.1 kg m-2 yr-1 leads to 50 m ice-bonded methane hydrate at the base of permafrost, and the hydrate layer distributes between the depth of 350 and 700 m at 80 k.y.. We apply our model to illuminate future melting of hydrate at Mallik, a known Arctic hydrate accumulation. We assume a 600 m thick ice saturated (average 90%) layer extending downward from the ground surface. We increase the surface temperature linearly from -6 to 0 oC for 300 yr and then keep the surface temperature at 0 oC to reflect future climate warming caused by doubling of CO2. Hydrate melting is initiated at the base of the hydrate layer after 15 k.y.. Methane gas starts to vent to the atmosphere at 38 k.y. with an average flux of ~ 0.35 g m-2 yr-1. If the 600 m thick average ice saturation is decreased to half (45%) (or to zero), methane gas starts to vent to the atmosphere at 29 k.y. (or at 20 k.y.) with the same average flux. These results are found by a newly-developed fully-coupled multiphase multicomponent fluid flow and heat transport model. Our thermodynamic equilibrium-based model emphasizes the role of salinity in both ice and hydrate dynamics.

  19. Pressure-induced amorphization and collapse of magnetic order in the type-I clathrate Eu8Ga16Ge30

    Science.gov (United States)

    Mardegan, J. R. L.; Fabbris, G.; Veiga, L. S. I.; Adriano, C.; Avila, M. A.; Haskel, D.; Giles, C.

    2013-10-01

    We investigate the low temperature structural and electronic properties of the type-I clathrate Eu8Ga16Ge30 under pressure using x-ray powder diffraction (XRD), x-ray absorption near-edge structure (XANES), and x-ray magnetic circular dichroism (XMCD) techniques. The XRD measurements reveal a transition to an amorphous phase above 18 GPa. Unlike previous reports on other clathrate compounds, no volume collapse is observed prior to the crystalline-amorphous phase transition which takes place when the unit cell volume is reduced to 81% of its ambient pressure value. Fits of the pressure-dependent relative volume to a Murnaghan equation of state yield a bulk modulus B0=65±3 GPa and a pressure derivative B0'=3.3±0.5. The Eu L2-edge XMCD data shows quenching of the magnetic order at a pressure coincident with the crystalline-amorphous phase transition. This information along with the persistence of an Eu2+ valence state observed in the XANES spectra up to the highest pressure point (22 GPa) indicates that the suppression of XMCD intensity is due to the loss of long range magnetic order. When compared with other clathrates, the results point to the importance of guest ion-cage interactions in determining the mechanical stability of the framework structure and the critical pressure for amorphization. Finally, the crystalline structure is not found to recover after pressure release, resulting in an amorphous material that is at least metastable at ambient pressure and temperature.

  20. Amount of gas hydrate estimated from compressional- and shear-wave velocities at the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well

    Science.gov (United States)

    Lee, M.W.

    1999-01-01

    The amount of in situ gas hydrate concentrated in the sediment pore space at the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well was estimated by using compressional-wave (P-wave) and shear-wave (S-wave) downhole log measurements. A weighted equation developed for relating the amount of gas hydrate concentrated in the pore space of unconsolidated sediments to the increase of seismic velocities was applied to the acoustic logs with porosities derived from the formation density log. A weight of 1.56 (W=1.56) and the exponent of 1 (n=1) provided consistent estimates of gas hydrate concentration from the S-wave and the P-wave logs. Gas hydrate concentration is as much as 80% in the pore spaces, and the average gas hydrate concentration within the gas-hydrate-bearing section from 897 m to 1110 m (excluding zones where there is no gas hydrate) was calculated at 39.0% when using P-wave data and 37.8% when using S-wave data.

  1. Silvering substrates after CO2 snow cleaning

    Science.gov (United States)

    Zito, Richard R.

    2005-09-01

    There have been some questions in the astronomical community concerning the quality of silver coatings deposited on substrates that have been cleaned with carbon dioxide snow. These questions center around the possible existence of carbonate ions left behind on the substrate by CO2. Such carbonate ions could react with deposited silver to produce insoluble silver carbonate, thereby reducing film adhesion and reflectivity. Carbonate ions could be produced from CO2 via the following mechanism. First, during CO2 snow cleaning, a small amount of moisture can condense on a surface. This is especially true if the jet of CO2 is allowed to dwell on one spot. CO2 gas can dissolve in this moisture, producing carbonic acid, which can undergo two acid dissociations to form carbonate ions. In reality, it is highly unlikely that charged carbonate ions will remain stable on a substrate for very long. As condensed water evaporates, Le Chatelier's principle will shift the equilibrium of the chain of reactions that produced carbonate back to CO2 gas. Furthermore, the hydration of CO2 reaction of CO2 with H20) is an extremely slow process, and the total dehydrogenation of carbonic acid is not favored. Living tissues that must carry out the equilibration of carbonic acid and CO2 use the enzyme carbonic anhydrase to speed up the reaction by a factor of one million. But no such enzymatic action is present on a clean mirror substrate. In short, the worst case analysis presented below shows that the ratio of silver atoms to carbonate radicals must be at least 500 million to one. The results of chemical tests presented here support this view. Furthermore, film lift-off tests, also presented in this report, show that silver film adhesion to fused silica substrates is actually enhanced by CO2 snow cleaning.

  2. astrophysical significance

    Directory of Open Access Journals (Sweden)

    Dartois E.

    2014-02-01

    Full Text Available Clathrate hydrates, ice inclusion compounds, are of major importance for the Earth’s permafrost regions and may control the stability of gases in many astrophysical bodies such as the planets, comets and possibly interstellar grains. Their physical behavior may provide a trapping mechanism to modify the absolute and relative composition of icy bodies that could be the source of late-time injection of gaseous species in planetary atmospheres or hot cores. In this study, we provide and discuss laboratory-recorded infrared signatures of clathrate hydrates in the near to mid-infrared and the implications for space-based astrophysical tele-detection in order to constrain their possible presence.

  3. Sequestering CO{sub 2} by Mineralization into Useful Nesquehonite-Based Products

    Energy Technology Data Exchange (ETDEWEB)

    Glasser, Fredrik Paul, E-mail: f.p.glasser@abdn.ac.uk; Jauffret, Guillaume; Morrison, Jennie [Department of Chemistry, University of Aberdeen, Aberdeen (United Kingdom); Galvez-Martos, Jose-Luis; Patterson, Naomi; Imbabi, Mohammed Salah-Eldin [School of Engineering, University of Aberdeen, Aberdeen (United Kingdom)

    2016-02-11

    The precipitation of magnesium hydroxy-carbonate hydrates has been suggested as a route to sequester CO{sub 2} into solids. We report the development of self-cementing compositions based on nesquehonite, MgCO{sub 3}⋅3H{sub 2}O, that are made from CO{sub 2}-containing gas streams, the CO{sub 2} being separated from other gases by its high solubility in alkaline water, while magnesium is typically provided by waste desalination brines. Precipitation conditions are adjusted to optimize the formation of nesquehonite and the crystalline solid can readily be washed free of chloride. Products can be prepared to achieve self-cementation following two routes: (i) thermal activation of the nesquehonite then rehydration of the precursor or (ii) direct curing of a slurry of nesquehonite. The products thus obtained contain ~30 wt% CO{sub 2} and could form the basis for a new generation of lightweight, thermally insulating boards, blocks, and panels, with sufficient strength for general construction.

  4. Ultrafast phosphate hydration dynamics in bulk H2O

    Science.gov (United States)

    Costard, Rene; Tyborski, Tobias; Fingerhut, Benjamin P.; Elsaesser, Thomas

    2015-06-01

    Phosphate vibrations serve as local probes of hydrogen bonding and structural fluctuations of hydration shells around ions. Interactions of H2PO4- ions and their aqueous environment are studied combining femtosecond 2D infrared spectroscopy, ab-initio calculations, and hybrid quantum-classical molecular dynamics (MD) simulations. Two-dimensional infrared spectra of the symmetric ( ν S ( PO2 - ) ) and asymmetric ( ν A S ( PO2 - ) ) PO 2- stretching vibrations display nearly homogeneous lineshapes and pronounced anharmonic couplings between the two modes and with the δ(P-(OH)2) bending modes. The frequency-time correlation function derived from the 2D spectra consists of a predominant 50 fs decay and a weak constant component accounting for a residual inhomogeneous broadening. MD simulations show that the fluctuating electric field of the aqueous environment induces strong fluctuations of the ν S ( PO2 - ) and ν A S ( PO2 - ) transition frequencies with larger frequency excursions for ν A S ( PO2 - ) . The calculated frequency-time correlation function is in good agreement with the experiment. The ν ( PO2 - ) frequencies are mainly determined by polarization contributions induced by electrostatic phosphate-water interactions. H2PO4-/H2O cluster calculations reveal substantial frequency shifts and mode mixing with increasing hydration. Predicted phosphate-water hydrogen bond (HB) lifetimes have values on the order of 10 ps, substantially longer than water-water HB lifetimes. The ultrafast phosphate-water interactions observed here are in marked contrast to hydration dynamics of phospholipids where a quasi-static inhomogeneous broadening of phosphate vibrations suggests minor structural fluctuations of interfacial water.

  5. Gas hydrate dissociation prolongs acidification of the Anthropocene oceans

    NARCIS (Netherlands)

    Boudreau, B.P.; Luo, Yiming; Meysman, Filip J R; Middelburg, J.J.; Dickens, G.R.

    2015-01-01

    Anthropogenic warming of the oceans can release methane (CH4) currently stored in sediments as gas hydrates. This CH4 will be oxidized to CO2, thus increasing the acidification of the oceans. We employ a biogeochemical model of the multimillennial carbon cycle to determine the evolution of the

  6. Thermodynamic properties of Portland cement hydrates in the system CaO-Al2O3-SiO2-CaSO4-CaCO3-H2O

    International Nuclear Information System (INIS)

    Matschei, Thomas; Lothenbach, Barbara; Glasser, Fredrik P.

    2007-01-01

    A database is presented for commonly-encountered cement substances including C-S-H, Ca(OH) 2 , selected AFm, AFt and hydrogarnet compositions as well as solid solutions. The AFm compositions include straetlingite. The data were obtained for the most part from experiment and many of the predicted reactions were confirmed by focussed experiments. The temperature-dependence of the thermodynamic data for the above phases, determined partly from experiment and partly from thermodynamic estimations, are also tabulated in the range 1 deg. C to 99 deg. C. Relative to previous databases, sulfate AFm is shown to have a definite range of stability range at 25 deg. C thus removing long-standing doubts about its stability in normal hydrated cement pastes. Carbonate is shown to interact strongly with stabilisation of AFm across a broad range of temperatures and, at low temperatures, to substitute into AFt. The new database enables the ultimate hydrate mineralogy to be calculated from chemistry: most solid assemblages, the persistence of C-S-H apart, correspond closely to equilibrium. This realisation means that hydrate assemblages can be controlled. The development of a thermodynamic approach also enables a fresh look at how mineralogical changes occur in response to environmentally-conditioned reactions; several papers showing applications are cited

  7. Mineralogy of C-S-H belite hydrates incorporating Zn-Al-Ti layered double hydroxides

    Directory of Open Access Journals (Sweden)

    Amor F.

    2018-01-01

    Full Text Available Recently, the belitic cements with low alite content were the subject of several research works which aimed to replace the Ordinary Portland Clinker (OPC for ecological reasons (reduction of CO2 emissions, so to understand the reactivity of this cement, the hydration study of the C2S “dicalcium silicate” phase is primordial research step. As well for a clean environment, the TiO2 photocatalyst has been extensively applied in the science of building materials because of its ability to degrade the cement surface pollutants. New photocatalyst based layered double hydroxides (LDH associated with zinc, aluminium and TiO2 was introduced to increase the compatibility with mortars. The present work is subjected to investigate the effect of the layered double hydroxides on the hydration of C2S in following the evolution of hydration by X-ray diffraction at 2, 7, 28 and 90 days and analyzing the calcium/silicon ratio of different formed hydrates.

  8. THE INFLUENCE OF CO2 ON WELL CEMENT

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    2010-12-01

    Full Text Available Carbon capture and storage is one way to reduce emissions of greenhouse gases in the atmosphere. Underground gas storage operations and CO2 sequestration in aquifers relay on both the proper wellbore construction and sealing properties of the cap rock. CO2 injection candidates may be new wells or old wells. In both cases, the long-term wellbore integrity (up to 1 000 years is one of the key performance criteria in the geological storage of CO2. The potential leakage paths are the migration CO2 along the wellbore due to poor cementation and flow through the cap rock. The permeability and integrity of the set cement will determine how effective it is in preventing the leakage. The integrity of the cap rock is assured by an adequate fracture gradient and by sufficient set cement around the casing across the cap rock and without a micro-annulus. CO2 storage in underground formations has revived the researc of long term influence of the injected CO2 on Portland cements and methods for improving the long term efficiency of the wellbore sealant. Some researchers predicted that set cement will fail when exposed to CO2 leading to potential leakage to the atmosphere or into underground formations that may contain potable water. Other researchers show set cement samples from 30 to 50 year-old wells (CO2 EOR projects that have maintained sealing integrity and prevented CO2 leakage, in spite of some degree of carbonation. One of reasons for the discrepancy between certain research lab tests and actual field performance measurements is the absence of standard protocol for CO2 resistance-testing devices, conditions, or procedures. This paper presents potential flow paths along the wellbore, CO2 behaviour under reservoir conditions, and geochemical alteration of hydrated Portland cement due to supercritical CO2 injection.

  9. The millennial atmospheric lifetime of anthropogenic CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Archer, D. [University of Chicago, IL (United States). Department of the Geophysical Sciences; Brovkin, V. [Potsdam Institute for Climate Impact Research (Germany)

    2008-10-15

    The notion is pervasive in the climate science community and in the public at large that the climate impacts of fossil fuel CO{sub 2} release will only persist for a few centuries. This conclusion has no basis in theory or models of the atmosphere/ocean carbon cycle, which we review here. The largest fraction of the CO{sub 2} recovery will take place on time scales of centuries, as CO{sub 2} invades the ocean, but a significant fraction of the fossil fuel CO{sub 2}, ranging in published models in the literature from 20-60%, remains airborne for a thousand years or longer. Ultimate recovery takes place on time scales of hundreds of thousands of years, a geologic longevity typically associated in public perceptions with nuclear waste. The glacial/interglacial climate cycles demonstrate that ice sheets and sea level respond dramatically to millennial-timescale changes in climate forcing. There are also potential positive feedbacks in the carbon cycle, including methane hydrates in the ocean, and peat frozen in permafrost, that are most sensitive to the long tail of the fossil fuel CO{sub 2} in the atmosphere.

  10. Canadian CO2 Capture and Storage Technology Network : promoting zero emissions technologies

    International Nuclear Information System (INIS)

    2004-11-01

    This brochure provided information on some Canadian initiatives in carbon dioxide (CO 2 ) capture and storage. There has been growing interest in the implementation of components of CO 2 capture, storage and utilization technologies in Canada. Technology developments by the CANMET Energy Technology Centre concerning CO 2 capture using oxy-fuel combustion and amine separation were examined. Techniques concerning gasification of coal for electricity production and CO 2 capture were reviewed. Details of a study of acid gas underground injection were presented. A review of monitoring technologies in CO 2 storage in enhanced oil recovery was provided. Issues concerning the enhancement of methane recovery through the monitoring of CO 2 injected into deep coal beds were discussed. Storage capacity assessment of Canadian sedimentary basins, coal seams and oil and gas reservoirs were reviewed, in relation to their suitability for CO 2 sequestration. Details of the International Test Centre for Carbon Dioxide Capture in Regina, Saskatchewan were presented, as well as issues concerning the sequestration of CO 2 in oil sands tailings streams. A research project concerning the geologic sequestration of CO 2 and simultaneous CO 2 and methane production from natural gs hydrate reservoirs was also discussed. 12 figs.

  11. Evaluation of CO2-based cold sterilization of a model hydrogel.

    Science.gov (United States)

    Jiménez, A; Zhang, J; Matthews, M A

    2008-12-15

    The purpose of the present work is to evaluate a novel CO(2)-based cold sterilization process in terms of both its killing efficiency and its effects on the physical properties of a model hydrogel, poly(acrylic acid-co-acrylamide) potassium salt. Suspensions of Staphylococcus aureus and Escherichia coli were prepared for hydration and inoculation of the gel. The hydrogels were treated with supercritical CO(2) (40 degrees C, 27.6 MPa). The amount of bacteria was quantified before and after treatment. With pure CO(2), complete killing of S. aureus and E. coli was achieved for treatment times as low as 60 min. After treatment with CO(2) plus trace amounts of H(2)O(2) at the same experimental conditions, complete bacteria kill was also achieved. For times less than 30 min, incomplete kill was noted. Several physical properties of the gel were evaluated before and after SC-CO(2) treatment. These were largely unaffected by the CO(2) process. Drying curves showed no significant change between treated (pure CO(2) and CO(2) plus 30% H(2)O(2)) and untreated samples. The average equilibrium swelling ratios were also very similar. No changes in the dry hydrogel particle structure were evident from SEM micrographs.

  12. Adsorption of methane and CO2 onto olivine surfaces in Martian dust conditions

    Science.gov (United States)

    Escamilla-Roa, Elizabeth; Martin-Torres, Javier; Sainz-Díaz, C. Ignacio

    2018-04-01

    Methane has been detected on all planets of our Solar System, and most of the larger moons, as well as in dwarf-planets like Pluto and Eric. The presence of this molecule in rocky planets is very interesting because its presence in the Earth's atmosphere is mainly related to biotic processes. Space instrumentation in orbiters around Mars has detected olivine on the Martian soil and dust. On the other hand the measurements of methane from the Curiosity rover report detection of background levels of atmospheric methane with abundance that is lower than model estimates of ultraviolet degradation of accreted interplanetary dust particles or carbonaceous chondrite material. Additionally, elevated levels of methane about this background have been observed implying that Mars is episodically producing methane from an additional unknown source, making the reasons of these temporal fluctuations of methane a hot topic in planetary research. The goal of this study is to investigate at atomic level the interactions during the adsorption processes of methane and other Mars atmospheric species (CO2, H2O) on forsterite surfaces, through electronic structure calculations based on the Density Functional Theory (DFT). We propose two models to simulate the interaction of adsorbates with the surface of dust mineral, such as binary mixtures (5CH4+5H2O/5CH4+5CO2) and as a semi-clathrate adsorption. We have obtained interesting results of the adsorption process in the mixture 5CH4+5CO2. Associative and dissociative adsorptions were observed for water and CO2 molecules. The methane molecules were only trapped and held by water or CO2 molecules. In the dipolar surface, the adsorption of CO2 molecules produced new species: one CO from a CO2 dissociation, and, two CO2 molecules chemisorbed to mineral surface forming in one case a carbonate group. Our results suggest that CO2 has a strong interaction with the mineral surface when methane is present. These results could be confirmed after the

  13. Understanding hydration of Zn(2+) in hydrothermal fluids with ab initio molecular dynamics

    NARCIS (Netherlands)

    Liu, X.; Lu, X.; Wang, R.; Meijer, E.J.

    2011-01-01

    With ab initio molecular dynamics simulations, the free-energy profiles of hydrated Zn2+ are calculated for both gaseous and aqueous systems from ambient to supercritical conditions, and from the derived free-energy information, the speciation of hydrated Zn2+ has been revealed. It is shown that the

  14. Hydrate phase equilibria of furan, acetone, 1,4-dioxane, TBAC and TBAF

    International Nuclear Information System (INIS)

    Kamran-Pirzaman, Arash; Pahlavanzadeh, Hassan; Mohammadi, Amir H.

    2013-01-01

    Highlights: • Experimental hydrate dissociation conditions are reported for CO 2 /methane + some water soluble/insoluble hydrate formers. • An isochoric pressure-search method was used to generate the experimental data. • The data are compared with the corresponding literature data in the presence of pure water. • The hydrate promotion effects of acetone, 1,4-dioxane, furan, TBAC and TBAF are discussed. -- Abstract: In this communication, we first report experimental hydrate dissociation pressures for the methane/carbon dioxide + furan/acetone/1,4-dioxane + water and the methane + tetra n-butyl ammonium chloride (TBAC) + water as well as the carbon dioxide + tetra n-butyl ammonium floride (TBAF) + water systems in the temperature ranges of (269.9 to 303.3) K. An isochoric pressure-search method was used to generate the experimental data. The hydrate dissociation data are compared with the corresponding literature data, if exists, and the literature data in the presence of pure water and acceptable agreement is observed. A discussion is made on hydrate promotion effects of acetone, 1,4-dioxane, furan, TBAC and TBAF

  15. Waters of Hydration of Cupric Hydrates: A Comparison between Heating and Absorbance Methods

    Science.gov (United States)

    Barlag, Rebecca; Nyasulu, Frazier

    2011-01-01

    The empirical formulas of four cupric hydrates are determined by measuring the absorbance in aqueous solution. The Beer-Lambert Law is verified by constructing a calibration curve of absorbance versus known Cu[superscript 2+](aq) concentration. A solution of the unknown hydrate is prepared by using 0.2-0.3 g of hydrate, and water is added such…

  16. Onset and stability of gas hydrates under permafrost in an environment of surface climatic change : past and future

    International Nuclear Information System (INIS)

    Majorowicz, J.A.; Osadetz, K.; Safanda, J.

    2008-01-01

    This paper presented a model designed to simulate permafrost and gas hydrate formation in a changing surface temperature environment in the Beaufort-Mackenzie Basin (BMB). The numerical model simulated surface forcing due to general cooling trends that began in the late Miocene era. This study modelled the onset of permafrost formation and subsequent gas hydrate formation in the changing surface temperature environment for the BMB. Paleoclimatic data were used. The 1-D model was constrained by deep heat flow from well bottom hole temperatures; conductivity; permafrost thickness; and the thickness of the gas hydrates. The model used latent heat effects for the ice-bearing permafrost and hydrate intervals. Surface temperatures for glacial and interglacial histories for the last 14 million years were considered. The model also used a detailed Holocene temperature history as well as a scenario in which atmospheric carbon dioxide (CO 2 ) levels were twice as high as current levels. Two scenarios were considered: (1) the formation of gas hydrates from gas entrapped under geological seals; and (2) the formation of gas hydrates from gas located in free pore spaces simultaneously with permafrost formation. Results of the study showed that gas hydrates may have formed at a depth of 0.9 km only 1 million years ago. Results of the other modelling scenarios suggested that the hydrates formed 6 million years ago, when temperature changes caused the gas hydrate layer to expand both downward and upward. Detailed models of more recent glacial and interglacial histories showed that the gas hydrate zones will persist under the thick body of the BMB permafrost through current interglacial warming as well as in scenarios where atmospheric CO 2 is doubled. 28 refs., 13 figs

  17. Prediction of CO2 leakage during sequestration into marine sedimentary strata

    International Nuclear Information System (INIS)

    Li, Qi; Wu Zhishen; Li Xiaochun

    2009-01-01

    Deep ocean storage of CO 2 could help reduce the atmospheric level of greenhouse gas as part of a climate change mitigation strategy. In this paper, a multiphase flow model of CO 2 sequestration into deep ocean sediments was designed associated with the formation of CO 2 hydrates. A simplified assumption was proposed to predict the critical time of CO 2 leakage from marine sedimentary strata into seawater. Moreover, some principal parameters, which include the permeability, anisotropy, total injection amount, and length of the injection part of wellbores, were investigated by numerical simulations. The numerical estimates are used to assess the feasibility and effectiveness of CO 2 storage in deep ocean sediments. Accurately predicting the actual fate of liquid CO 2 sequestered into the marine sedimentary strata at depths greater than 500 m is complicated by uncertainties associated with not only the chemical-physical behavior of CO 2 under such conditions but also the geo-environment of disposal sites. Modeling results have shown some implications that the effectiveness of CO 2 ocean sequestration depends mainly on the injection conditions (such as injection rate, total injection amount, and the depth of injection), the site geology (such as permeability and anisotropy of disposal formations), and the chemical-physical behavior of CO 2 in marine environment

  18. Ultrafast phosphate hydration dynamics in bulk H2O

    International Nuclear Information System (INIS)

    Costard, Rene; Tyborski, Tobias; Fingerhut, Benjamin P.; Elsaesser, Thomas

    2015-01-01

    Phosphate vibrations serve as local probes of hydrogen bonding and structural fluctuations of hydration shells around ions. Interactions of H 2 PO 4 − ions and their aqueous environment are studied combining femtosecond 2D infrared spectroscopy, ab-initio calculations, and hybrid quantum-classical molecular dynamics (MD) simulations. Two-dimensional infrared spectra of the symmetric (ν S (PO 2 − )) and asymmetric (ν AS (PO 2 − )) PO 2 − stretching vibrations display nearly homogeneous lineshapes and pronounced anharmonic couplings between the two modes and with the δ(P-(OH) 2 ) bending modes. The frequency-time correlation function derived from the 2D spectra consists of a predominant 50 fs decay and a weak constant component accounting for a residual inhomogeneous broadening. MD simulations show that the fluctuating electric field of the aqueous environment induces strong fluctuations of the ν S (PO 2 − ) and ν AS (PO 2 − ) transition frequencies with larger frequency excursions for ν AS (PO 2 − ). The calculated frequency-time correlation function is in good agreement with the experiment. The ν(PO 2 − ) frequencies are mainly determined by polarization contributions induced by electrostatic phosphate-water interactions. H 2 PO 4 − /H 2 O cluster calculations reveal substantial frequency shifts and mode mixing with increasing hydration. Predicted phosphate-water hydrogen bond (HB) lifetimes have values on the order of 10 ps, substantially longer than water-water HB lifetimes. The ultrafast phosphate-water interactions observed here are in marked contrast to hydration dynamics of phospholipids where a quasi-static inhomogeneous broadening of phosphate vibrations suggests minor structural fluctuations of interfacial water

  19. Systematic Studies on Anharmonicity of Rattling Phonons in Type I Clathrates by Low Temperature Heat Capacity Measurements

    Science.gov (United States)

    Tanigaki, Katsumi; Wu, Jiazhen; Tanabe, Yoichi; Heguri, Satoshi; Shiimotani, Hidekazu; Tohoku University Collaboration

    2014-03-01

    Clathrates are featured by cage-like polyhedral hosts mainly composed of the IVth group elements of Si, Ge, or Sn and alkali metal or alkaline-earth metal elements can be accommodated inside as a guest atom. One of the most intriguing issues in clathrates is their outstanding high thermoelectric performances thanks to the low thermal conductivity. Being irrespective of good electric conductivity σ, the guest atom motions provide a low-energy lying less-dispersive phonons and can greatly suppress thermal conductivity κ. This makes clathrates close to the concept of ``phonon glass electron crystal: PGEC'' and useful in thermoelectric materials from the viewpoint of the figure of merit. In the present study, we show that the local phonon anharmonicity indicated by the tunneling-term of the endohedral atoms (αT) and the itinerant-electron term (γeT), both of which show T-linear dependences in specific heat Cp, can successfully be separated by employing single crystals with various carrier concentrations in a wide range of temperture experimennts. The factors affecting on the phonon anharmonicity as well as the strength of electron-phonon interactions will be discussed based on our recent experiments. The research was financially supported by Ministry of Education, Science, Sports and Culture, Grant in Aid for Science, and Technology of Japan.

  20. Desalination of Produced Water via Gas Hydrate Formation and Post Treatment

    OpenAIRE

    Niu, Jing

    2012-01-01

    This study presents a two-step desalination process, in which produced water is cleaned by forming gas hydrate in it and subsequently dewatering the hydrate to remove the residual produced water trapped in between the hydrate crystals. All experiments were performed with pressure in the range of 450 to 800psi and temperature in the range of -1 to 1°C using CO? as guest molecule for the hydrate crystals. The experiments were conducted using artificial produced waters containing different amoun...

  1. Stability of sorbents based on hydrated TiO2 with different content of ZrO2

    International Nuclear Information System (INIS)

    Malykh, T.G.; Sharygin, L.M.

    1983-01-01

    The effect of ZrO 2 content in hydrated titanium dioxide on i s hydrothermat stabitity in the 120-350 deg C range, is investigated. It is shown that the specific surface of hydrated titanium dioxide in the process of hydrothermal treatment at different temperatures changes within a number of stages and depends on the zirconium dioxide contents in it. Sorbents are stable under hydrothermal conditions at temperatures not exceeding 300 deg C. The stabilizing effect of zirconiUm dioxide on the properties of hydrated titanium dioxide is most pronounced at 350 deg C

  2. Hydration of a low-alkali CEM III/B–SiO2 cement (LAC)

    International Nuclear Information System (INIS)

    Lothenbach, Barbara; Le Saout, Gwenn; Ben Haha, Mohsen; Figi, Renato; Wieland, Erich

    2012-01-01

    The hydration of a low-alkali cement based on CEM III/B blended with 10 wt.% of nanosilica has been studied. The nanosilica reacted within the first days and 90% of the slag reacted within 3.5 years. C-S-H (Ca/Si ∼ 1.2, Al/Si ∼ 0.12), calcite, hydrotalcite, ettringite and possibly strätlingite were the main hydrates. The pore water composition revealed ten times lower alkali concentrations than in Portland cements. Reducing conditions (HS − ) and a pH value of 12.2 were observed. Between 1 month and 3.5 years of hydration more hydrates were formed due to the ongoing slag reaction but no significant differences in the composition of the pore solution or solid phase assemblage were observed. On the basis of thermodynamic calculations it is predicted that siliceous hydrogarnet could form in the long-term and, in the presence of siliceous hydrogarnet, also thaumasite. Nevertheless, even after 3.5 year hydration, neither siliceous hydrogarnet nor thaumasite have been observed.

  3. THCM Coupled Model for Hydrate-Bearing Sediments: Data Analysis and Design of New Field Experiments (Marine and Permafrost Settings)

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Marcelo J. [Texas A & M Univ., College Station, TX (United States); Santamarina, J. Carlos [King Abdullah Univ. of Science and Technology (Saudi Arabia)

    2017-02-14

    Gas hydrates are solid compounds made of water molecules clustered around low molecular weight gas molecules such as methane, hydrogen, and carbon dioxide. Methane hydrates form under pressure (P) and temperature (T) conditions that are common in sub-permafrost layers and in deep marine sediments. Stability conditions constrain the occurrence of gas hydrates to submarine sediments and permafrost regions. The amount of technically recoverable methane trapped in gas hydrate may exceed 104tcf. Gas hydrates are a potential energy resource, can contribute to climate change, and can cause large-scale seafloor instabilities. In addition, hydrate formation can be used for CO2 sequestration (also through CO2-CH4 replacement), and efficient geological storage seals. The experimental study of hydrate bearing sediments has been hindered by the very low solubility of methane in water (lab testing), and inherent sampling difficulties associated with depressurization and thermal changes during core extraction. This situation has prompted more decisive developments in numerical modeling in order to advance the current understanding of hydrate bearing sediments, and to investigate/optimize production strategies and implications. The goals of this research has been to addresses the complex thermo-hydro-chemo-mechanical THCM coupled phenomena in hydrate-bearing sediments, using a truly coupled numerical model that incorporates sound and proven constitutive relations, satisfies fundamental conservation principles. Analytical solutions aimed at verifying the proposed code have been proposed as well. These tools will allow to better analyze available data and to further enhance the current understanding of hydrate bearing sediments in view of future field experiments and the development of production technology.

  4. Lanthanite-(Nd), Nd2(CO3)3·8H2O

    Science.gov (United States)

    Morrison, Shaunna M.; Andrade, Marcelo B.; Wenz, Michelle D.; Domanik, Kenneth J.; Downs, Robert T.

    2013-01-01

    Lanthanite-(Nd), ideally Nd2(CO3)3·8H2O [dineodymium(III) tricarbonate octa­hydrate], is a member of the lanthanite mineral group characterized by the general formula REE 2(CO3)3·8H2O, where REE is a 10-coordinated rare earth element. Based on single-crystal X-ray diffraction of a natural sample from Mitsukoshi, Hizen-cho, Karatsu City, Saga Prefecture, Japan, this study presents the first structure determination of lanthanite-(Nd). Its structure is very similar to that of other members of the lanthanite group. It is composed of infinite sheets made up of corner- and edge-sharing of two NdO10-polyhedra (both with site symmetry ..2) and two carbonate triangles (site symmetries ..2 and 1) parallel to the ab plane, and stacked perpendicular to c. These layers are linked to one another only through hydrogen bonding involving the water mol­ecules. PMID:23476479

  5. Carbonate hydrates of the heavy alkali metals: preparation and structure of Rb{sub 2}CO{sub 3} . 1.5 H{sub 2}O und Cs{sub 2}CO{sub 3} . 3 H{sub 2}O; Carbonat-Hydrate der schweren Alkalimetalle: Darstellung und Struktur von Rb{sub 2}CO{sub 3} . 1,5 H{sub 2}O und Cs{sub 2}CO{sub 3} . 3 H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Cirpus, V.; Wittrock, J.; Adam, A. [Koeln Univ. (Germany). Inst. fuer Anorganische Chemie

    2001-03-01

    Rb{sub 2}CO{sub 3} . 1.5 H{sub 2}O and Cs{sub 2}CO{sub 3} . 3 H{sub 2}O were prepared from aqueous solution and by means of the reaction of dialkylcarbonates with RbOH and CsOH resp. in hydrous alcoholes. Based on four-circle diffractometer data, the crystal structures were determined (Rb{sub 2}CO{sub 3} . 1.5 H{sub 2}O: C2/c (no. 15), Z = 8, a = 1237.7(2) pm, b = 1385.94(7) pm, c = 747.7(4) pm, {beta} = 120.133(8) , V{sub EZ} = 1109.3(6) . 10{sup 6} pm{sup 3}; Cs{sub 2}CO{sub 3} . 3 H{sub 2}O: P2/c (no. 13), Z = 2, a = 654.5(2) pm, b = 679.06(6) pm, c = 886.4(2) pm, {beta} = 90.708(14) , V{sub EZ} = 393.9(2) . 10{sup 6} pm{sup 3}). Rb{sub 2}CO{sub 3} . 1.5 H{sub 2}O is isostructural with K{sub 2}CO{sub 3} . 1.5 H{sub 2}O. In case of Cs{sub 2}CO{sub 3} . 3 H{sub 2}O no comparable structure is known. Both structures show {sub {infinity}}{sup 1}[(CO{sub 3}{sup 2-})(H{sub 2}O)]-chains, being connected via additional H{sub 2}O forming columns (Rb{sub 2}CO{sub 3} . 1.5 H{sub 2}O) and layers (Cs{sub 2}CO{sub 3} . 3 H{sub 2}O), respectively. (orig.)

  6. Carbonation of wollastonite(001) competing hydration: microscopic insights from ion spectroscopy and density functional theory.

    Science.gov (United States)

    Longo, Roberto C; Cho, Kyeongjae; Brüner, Philipp; Welle, Alexander; Gerdes, Andreas; Thissen, Peter

    2015-03-04

    In this paper, we report about the influence of the chemical potential of water on the carbonation reaction of wollastonite (CaSiO3) as a model surface of cement and concrete. Total energy calculations based on density functional theory combined with kinetic barrier predictions based on nudge elastic band method show that the exposure of the water-free wollastonite surface to CO2 results in a barrier-less carbonation. CO2 reacts with the surface oxygen and forms carbonate (CO3(2-)) complexes together with a major reconstruction of the surface. The reaction comes to a standstill after one carbonate monolayer has been formed. In case one water monolayer is covering the wollastonite surface, the carbonation is no more barrier-less, yet ending in a localized monolayer. Covered with multilayers of water, the thermodynamic ground state of the wollastonite completely changes due to a metal-proton exchange reaction (also called early stage hydration) and Ca(2+) ions are partially removed from solid phase into the H2O/wollastonite interface. Mobile Ca(2+) reacts again with CO2 and forms carbonate complexes, ending in a delocalized layer. By means of high-resolution time-of-flight secondary-ion mass spectrometry images, we confirm that hydration can lead to a partially delocalization of Ca(2+) ions on wollastonite surfaces. Finally, we evaluate the impact of our model surface results by the meaning of low-energy ion-scattering spectroscopy combined with careful discussion about the competing reactions of carbonation vs hydration.

  7. Carbonation and CO2 uptake of concrete

    International Nuclear Information System (INIS)

    Yang, Keun-Hyeok; Seo, Eun-A; Tae, Sung-Ho

    2014-01-01

    This study developed a reliable procedure to assess the carbon dioxide (CO 2 ) uptake of concrete by carbonation during the service life of a structure and by the recycling of concrete after demolition. To generalize the amount of absorbable CO 2 per unit volume of concrete, the molar concentration of carbonatable constituents in hardened cement paste was simplified as a function of the unit content of cement, and the degree of hydration of the cement paste was formulated as a function of the water-to-cement ratio. The contribution of the relative humidity, type of finishing material for the concrete surface, and the substitution level of supplementary cementitious materials to the CO 2 diffusion coefficient in concrete was reflected using various correction factors. The following parameters varying with the recycling scenario were also considered: the carbonatable surface area of concrete crusher-runs and underground phenomena of the decreased CO 2 diffusion coefficient and increased CO 2 concentration. Based on the developed procedure, a case study was conducted for an apartment building with a principal wall system and an office building with a Rahmen system, with the aim of examining the CO 2 uptake of each structural element under different exposure environments during the service life and recycling of the building. As input data necessary for the case study, data collected from actual surveys conducted in 2012 in South Korea were used, which included data on the surrounding environments, lifecycle inventory database, life expectancy of structures, and recycling activity scenario. Ultimately, the CO 2 uptake of concrete during a 100-year lifecycle (life expectancy of 40 years and recycling span of 60 years) was estimated to be 15.5%–17% of the CO 2 emissions from concrete production, which roughly corresponds to 18%–21% of the CO 2 emissions from the production of ordinary Portland cement. - Highlights: • CO 2 uptake assessment approach owing to the

  8. Polyethylene glycol drilling fluid for drilling in marine gas hydrates-bearing sediments: an experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, G.; Liu, T.; Ning, F.; Tu, Y.; Zhang, L.; Yu, Y.; Kuang, L. [China University of Geosciences, Faculty of Engineering, Wuhan (China)

    2011-07-01

    Shale inhibition, low-temperature performance, the ability to prevent calcium and magnesium-ion pollution, and hydrate inhibition of polyethylene glycol drilling fluid were each tested with conventional drilling-fluid test equipment and an experimental gas-hydrate integrated simulation system developed by our laboratory. The results of these tests show that drilling fluid with a formulation of artificial seawater, 3% bentonite, 0.3% Na{sub 2}CO{sub 3}, 10% polyethylene glycol, 20% NaCl, 4% SMP-2, 1% LV-PAC, 0.5% NaOH and 1% PVP K-90 performs well in shale swelling and gas hydrate inhibition. It also shows satisfactory rheological properties and lubrication at temperature ranges from -8 {sup o}C to 15 {sup o}C. The PVP K-90, a kinetic hydrate inhibitor, can effectively inhibit gas hydrate aggregations at a dose of 1 wt%. This finding demonstrates that a drilling fluid with a high addition of NaCl and a low addition of PVP K-90 is suitable for drilling in natural marine gas-hydrate-bearing sediments. (authors)

  9. Polyethylene Glycol Drilling Fluid for Drilling in Marine Gas Hydrates-Bearing Sediments: An Experimental Study

    Directory of Open Access Journals (Sweden)

    Lixin Kuang

    2011-01-01

    Full Text Available Shale inhibition, low-temperature performance, the ability to prevent calcium and magnesium-ion pollution, and hydrate inhibition of polyethylene glycol drilling fluid were each tested with conventional drilling-fluid test equipment and an experimental gas-hydrate integrated simulation system developed by our laboratory. The results of these tests show that drilling fluid with a formulation of artificial seawater, 3% bentonite, 0.3% Na2CO3, 10% polyethylene glycol, 20% NaCl, 4% SMP-2, 1% LV-PAC, 0.5% NaOH and 1% PVP K-90 performs well in shale swelling and gas hydrate inhibition. It also shows satisfactory rheological properties and lubrication at temperature ranges from −8 °C to 15 °C. The PVP K-90, a kinetic hydrate inhibitor, can effectively inhibit gas hydrate aggregations at a dose of 1 wt%. This finding demonstrates that a drilling fluid with a high addition of NaCl and a low addition of PVP K-90 is suitable for drilling in natural marine gas-hydrate-bearing sediments.

  10. Storage capacity of hydrogen in gas hydrates

    International Nuclear Information System (INIS)

    Tsuda, Takaaki; Ogata, Kyohei; Hashimoto, Shunsuke; Sugahara, Takeshi; Sato, Hiroshi; Ohgaki, Kazunari

    2010-01-01

    The storage capacity of H 2 in the THF, THT, and furan hydrates was studied by p-V-T measurements. We confirmed that the storage and release processes of H 2 in all hydrates could be performed reversibly by pressure swing without destroying of hydrate cages. H 2 absorption in both THT and furan hydrates is much faster than THF hydrate in spite of same unit-cell structure. On the other hand, the storage amounts of H 2 are coincident in the all additive hydrates and would reach at about 1.0 mass% asymptotically.

  11. Vertical seismic profile data from well Mallik 2L-38 for gas hydrate studies

    Energy Technology Data Exchange (ETDEWEB)

    Mi, Y [Calgary Univ., AB (Canada). Dept. of Geology and Geophysics; Walia, R [Victoria Univ., BC (Canada) School of Earth and Ocean Sciences; Hyndman, R [Geological Survey of Canada, Sidney, BC (Canada) Pacific Geoscience Centre

    1999-07-01

    A gas hydrate research well was drilled in the Canadian Arctic to study gas hydrates in a permafrost setting in a collaborative research project between the Japan National Oil Corp., the Geological Survey of Canada and other agencies. The multidisciplinary study included an electromagnetic survey, permafrost and gas hydrate coring, comprehensive downhole geophysical logging and measurement. Laboratory studies concerned studies on recovered cuttings and core including sedimentology, physical properties, geochemistry, and reservoir characteristics of the Mallik gas accumulation. As part of the Mallik 2L-38 field program, a vertical seismic profiling survey was conducted at zero and other offset source positions with three component receiver tools and horizontal and vertical vibration sources. A special effort was made to record shear wave data, which will be used to estimate the effect of gas hydrate on formation velocities and to determine gas hydrate concentration as a function of the Mallik gas accumulation. From the initial VSP analysis, certain conclusions follow: 1) zero offset vertical vibration component Z and horizontal X component data give reliable velocity determination within the gas hydrate formation zone. P wave velocities from offset VSP data show an excellent consistency with that from offset data and with the sonic log. And 2) the VSP data permit reliable identification of gas hydrate bearing zones. Abstract only included.

  12. Methane and carbon dioxide hydrates on Mars: Potential origins, distribution, detection, and implications for future in situ resource utilization

    Science.gov (United States)

    Pellenbarg, Robert E.; Max, Michael D.; Clifford, Stephen M.

    2003-04-01

    There is high probability for the long-term crustal accumulation of methane and carbon dioxide on Mars. These gases can arise from a variety of processes, including deep biosphere activity and abiotic mechanisms, or, like water, they could exist as remnants of planetary formation and by-products of internal differentiation. CH4 and CO2 would tend to rise buoyantly toward the planet's surface, condensing with water under appropriate conditions of temperature and pressure to form gas hydrate. Gas hydrates are a class of materials created when gas molecules are trapped within a crystalline lattice of water-ice. The hydrate stability fields of both CH4 and CO2 encompass a portion of the Martian crust that extends from within the water-ice cryosphere, from a depth as shallow as ~10-20 m to as great as a kilometer or more below the base of the Martian cryosphere. The presence and distribution of methane and carbon dioxide hydrates may be of critical importance in understanding the geomorphic evolution of Mars and the geophysical identification of water and other volatiles stored in the hydrates. Of critical importance, Martian gas hydrates would ensure the availability of key in situ resources for sustaining future robotic and human exploration, and the eventual colonization, of Mars.

  13. Solubility Modeling of the Binary Systems Fe(NO3)3–H2O, Co(NO3)2–H2O and the Ternary System Fe(NO3)3–Co(NO3)2–H2O with the Extended Universal Quasichemical (UNIQUAC) Model

    DEFF Research Database (Denmark)

    Arrad, Mouad; Kaddami, Mohammed; Goundali, Bahija El

    2016-01-01

    Solubility modeling in the binary system Fe(NO3)3–H2O, Co(NO3)2–H2O and the ternary system Fe(NO3)3–Co(NO3)2–H2O is presented. The extended UNIQUAC model was applied to the thermodynamic assessment of the investigated systems. The model parameters obtained were regressed simultaneously using...... the available databank but with more experimental points, recently published in the open literature. A revision of previously published parameters for the cobalt ion and new parameters for the iron(III) nitrate system are presented. Based on this set of parameters, the equilibrium constants of hydrates...

  14. Charge transfer reactions between gas-phase hydrated electrons, molecular oxygen and carbon dioxide at temperatures of 80-300 K.

    Science.gov (United States)

    Akhgarnusch, Amou; Tang, Wai Kit; Zhang, Han; Siu, Chi-Kit; Beyer, Martin K

    2016-09-14

    The recombination reactions of gas-phase hydrated electrons (H2O)n˙(-) with CO2 and O2, as well as the charge exchange reaction of CO2˙(-)(H2O)n with O2, were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry in the temperature range T = 80-300 K. Comparison of the rate constants with collision models shows that CO2 reacts with 50% collision efficiency, while O2 reacts considerably slower. Nanocalorimetry yields internally consistent results for the three reactions. Converted to room temperature condensed phase, this yields hydration enthalpies of CO2˙(-) and O2˙(-), ΔHhyd(CO2˙(-)) = -334 ± 44 kJ mol(-1) and ΔHhyd(O2˙(-)) = -404 ± 28 kJ mol(-1). Quantum chemical calculations show that the charge exchange reaction proceeds via a CO4˙(-) intermediate, which is consistent with a fully ergodic reaction and also with the small efficiency. Ab initio molecular dynamics simulations corroborate this picture and indicate that the CO4˙(-) intermediate has a lifetime significantly above the ps regime.

  15. Sequestering CO2 in the Ocean: Options and Consequences

    Science.gov (United States)

    Rau, G. H.; Caldeira, K.

    2002-12-01

    The likelihood of negative climate and environmental impacts associated with increasing atmospheric CO2 has prompted serious consideration of various CO2 mitigation strategies. Among these are methods of capturing and storing of CO2 in the ocean. Two approaches that have received the most attention in this regard have been i) ocean fertilization to enhanced biological uptake and fixation of CO2, and ii) the chemical/mechanical capture and injection of CO2 into the deep ocean. Both methods seek to enhance or speed up natural mechanisms of CO2 uptake and storage by the ocean, namely i) the biological CO2 "pump" or ii) the passive diffusion of CO2 into the surface ocean and subsequent mixing into the deep sea. However, as will be reviewed, concerns about the capacity and effectiveness of either strategy in long-term CO2 sequestration have been raised. Both methods are not without potentially significant environmental impacts, and the costs of CO2 capture and injection (option ii) are currently prohibitive. An alternate method of ocean CO2 sequestration would be to react and hydrate CO2 rich waste gases (e.g., power plant flue gas) with seawater and to subsequently neutralize the resulting carbonic acid with limestone to produce calcium and bicarbonate ions in solution. This approach would simply speed up the CO2 uptake and sequestration that naturally (but very slowly) occurs via global carbonate weathering. This would avoid much of the increased acidity associated with direct CO2 injection while obviating the need for costly CO2 separation and capture. The addition of the resulting bicarbonate- and carbonate-rich solution to the ocean would help to counter the decrease in pH and carbonate ion concentration, and hence loss of biological calcification that is presently occurring as anthropogenic CO2 invades the ocean from the atmosphere. However, as with any approach to CO2 mitigation, the costs, impacts, risks, and benefits of this method need to be better understood

  16. Calcium aluminates hydration in presence of amorphous SiO2 at temperatures below 90 deg. C

    International Nuclear Information System (INIS)

    Rivas Mercury, J.M.; Turrillas, X.; Aza, A.H. de; Pena, P.

    2006-01-01

    The hydration behaviour of Ca 3 Al 2 O 6 , Ca 12 Al 14 O 33 and CaAl 2 O 4 with added amorphous silica at 40, 65 and 90 deg. C has been studied for periods ranging from 1 to 31 days. In hydrated samples crystalline phases like katoite (Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x ) and gibbsite, Al(OH) 3 , were identified, likewise amorphous phases like Al(OH) x , calcium silicate hydrates, C-S-H, and calcium aluminosilicate hydrates, C-S-A-H, were identified. The stoichiometry of Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x (0≤3-x≤0.334), which was the main crystalline product, was established by Rietveld refinement of X-ray and neutron diffraction data and by transmission electron microscopy. - Graphical abstract: Katoite, Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x (0≤3-x≤0.334), was identified besides gibbsite, Al(OH) 3 , as a crystalline stable hydration products in Ca 3 Al 2 O 6 , Ca 12 Al 14 O 33 and CaAl 2 O 4 hydrated with added amorphous silica between 40 and 90 deg. C

  17. Growth of a Hydrate Mound in the Sea of Japan over 300 ka as Revealed by U-Th Ages of MDAC and by H2S Concentrations of Massive Hydrates

    Science.gov (United States)

    Matsumoto, R.; Snyder, G. T.; Hiruta, A.; Kakizaki, Y.; Huang, C. Y.; Shen, C. C.

    2017-12-01

    The geological and geophysical exploration of gas hydrate in the Sea of Japan has revealed that hydrates occur as thick massive deposits within gas chimneys which often give rise to pingo-like hydrate mounds on the seafloor. We examine one case in which LWD has demonstrated anomalous profiles including both very low natural gamma ray (<10 API) and high acoustic velocities (2.5 to 3.5 km/s) extending down to 120mbsf, the base of gas hydrate stability (BGHS)[1]. Both conventional and pressure coring have confirmed thick, massive deposits of pure-gas hydrates. Hydrates in the shallow subsurface (< 20mbsf) are characterized by high H2S concentrations corresponding to AOM-induced production of HS-. The deeper hydrates generally have negligible amounts of H2S, with occasional exceptions in which H2S is moderately high. These observations lead us to conclude that both the re-equilibration and growth of hydrates in high CH4 and low to zero H2S conditions has continued during burial, and that this ongoing growth is an essential processes involved in the development of massive hydrates in the Sea of Japan.Regardless of depth, the Japan Sea gas hydrates are closely associated with 13-C depleted, methane-derived authigenic carbonates (MDACs). These MDACs are considered to have been formed at near-SMT depths as a response to increased alkalinity caused by AOM and, as such, MDACs are assumed to represent approximate paleo-seafloor at times of enhanced methane flux and intensive accumulation of gas hydrate in shallow subsurface. U-Th ages of MDACs collected from various depths in a mound-chimney system in central Joetsu Spur have revealed that the paleo-seafloor of 300 ka is presently situated at 30 to 55 mbsf within the gas chimney, in contrast to off-mound sites where it is situated at 100 mbsf. This suggests that at 300 ka the mound stood as a "hydrate-pingo" of 70 m high relative to the surrounding sea floor. At this time, the BGHS shoaled upwards 10m due to eustatic sea

  18. Performance of local correlation methods for halogen bonding: The case of Br2-(H2O)n,n = 4,5 clusters and Br2@5(12)6(2) clathrate cage.

    Science.gov (United States)

    Batista-Romero, Fidel A; Pajón-Suárez, Pedro; Bernal-Uruchurtu, Margarita I; Hernández-Lamoneda, Ramón

    2015-09-07

    The performance of local correlation methods is examined for the interactions present in clusters of bromine with water where the combined effect of hydrogen bonding (HB), halogen bonding (XB), and hydrogen-halogen (HX) interactions lead to many interesting properties. Local methods reproduce all the subtleties involved such as many-body effects and dispersion contributions provided that specific methodological steps are followed. Additionally, they predict optimized geometries that are nearly free of basis set superposition error that lead to improved estimates of spectroscopic properties. Taking advantage of the local correlation energy partitioning scheme, we compare the different interaction environments present in small clusters and those inside the 5(12)6(2) clathrate cage. This analysis allows a clear identification of the reasons supporting the use of local methods for large systems where non-covalent interactions play a key role.

  19. Novel understanding of calcium silicate hydrate from dilute hydration

    KAUST Repository

    Zhang, Lina

    2017-05-13

    The perspective of calcium silicate hydrate (C-S-H) is still confronting various debates due to its intrinsic complicated structure and properties after decades of studies. In this study, hydration at dilute suspension of w/s equaling to 10 was conducted for tricalcium silicate (C3S) to interpret long-term hydration process and investigate the formation, structure and properties of C-S-H. Based on results from XRD, IR, SEM, NMR and so forth, loose and dense clusters of C-S-H with analogous C/S ratio were obtained along with the corresponding chemical formulae proposed as Ca5Si4O13∙6.2H2O. Crystalline structure inside C-S-H was observed by TEM, which was allocated at the foil-like proportion as well as the edge of wrinkles of the product. The long-term hydration process of C3S in dilute suspension could be sketchily described as migration of calcium hydroxide and in-situ growth of C-S-H with equilibrium silicon in aqueous solution relatively constant and calcium varied.

  20. Enhanced growth of the red alga Porphyra-Yezoensis Ueda in high CO sub 2 concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Gao, K.; Aruga, Y.; Asada, K.; Ishihara, T.; Akano, T.; Kiyohara, M. (Kansai Environmental Engineering Centre, Osaka (Japan))

    1991-12-01

    Leafy thalli of the red alga Porphyra yezoensis Ueda, initiated from conchospores released from free-living conchocelis, were cultured using aeration with high CO{sub 2}. It was found that the higher the CO{sub 2} concentration, the faster the growth of the thalli. Aeration with elevated CO{sub 2} lowered pH in dark, but raised pH remarkably in light with the thalli, because the photosynthetic conversion of HCO{sub 3} {sup -} to OH{sup -} and CO{sub 2} proceeded much faster than the dissociation of hydrated CO{sub 2} releasing H{sup +}. Photosynthesis of the alga was found to be enhanced in the seawater of elevated dissolved inorganic carbon DIC, CO{sub 2} + HCO{sub 3}{sup -} + CO{sub 3}{sup -}. It is concluded that the increased pH in the light resulted in the increase of DIC in the culture media, thus enhancing photosynthesis and growth. The relevance of the results to removal of atmospheric CO{sub 2} by marine algae is discussed.

  1. Methods to determine hydration states of minerals and cement hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Baquerizo, Luis G., E-mail: luis.baquerizoibarra@holcim.com [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Matschei, Thomas [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Scrivener, Karen L. [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Saeidpour, Mahsa; Thorell, Alva; Wadsö, Lars [Building Materials, Lund University, Box 124, 221 000 Lund (Sweden)

    2014-11-15

    This paper describes a novel approach to the quantitative investigation of the impact of varying relative humidity (RH) and temperature on the structure and thermodynamic properties of salts and crystalline cement hydrates in different hydration states (i.e. varying molar water contents). The multi-method approach developed here is capable of deriving physico-chemical boundary conditions and the thermodynamic properties of hydrated phases, many of which are currently missing from or insufficiently reported in the literature. As an example the approach was applied to monosulfoaluminate, a phase typically found in hydrated cement pastes. New data on the dehydration and rehydration of monosulfoaluminate are presented. Some of the methods used were validated with the system Na{sub 2}SO{sub 4}–H{sub 2}O and new data related to the absorption of water by anhydrous sodium sulfate are presented. The methodology and data reported here should permit better modeling of the volume stability of cementitious systems exposed to various different climatic conditions.

  2. Methods to determine hydration states of minerals and cement hydrates

    International Nuclear Information System (INIS)

    Baquerizo, Luis G.; Matschei, Thomas; Scrivener, Karen L.; Saeidpour, Mahsa; Thorell, Alva; Wadsö, Lars

    2014-01-01

    This paper describes a novel approach to the quantitative investigation of the impact of varying relative humidity (RH) and temperature on the structure and thermodynamic properties of salts and crystalline cement hydrates in different hydration states (i.e. varying molar water contents). The multi-method approach developed here is capable of deriving physico-chemical boundary conditions and the thermodynamic properties of hydrated phases, many of which are currently missing from or insufficiently reported in the literature. As an example the approach was applied to monosulfoaluminate, a phase typically found in hydrated cement pastes. New data on the dehydration and rehydration of monosulfoaluminate are presented. Some of the methods used were validated with the system Na 2 SO 4 –H 2 O and new data related to the absorption of water by anhydrous sodium sulfate are presented. The methodology and data reported here should permit better modeling of the volume stability of cementitious systems exposed to various different climatic conditions

  3. Numerical simulation of CO2 leakage from a geologic disposal reservoir, including transitions from super- to sub-critical conditions, and boiling of liquid of CO2

    International Nuclear Information System (INIS)

    Pruess, Karsten

    2003-01-01

    The critical point of CO 2 is at temperature and pressure conditions of T crit = 31.04 C, P crit = 73.82 bar. At lower (subcritical) temperatures and/or pressures, CO 2 can exist in two different phase states, a liquid and a gaseous state, as well as in two-phase mixtures of these states. Disposal of CO 2 into brine formations would be made at supercritical pressures. However, CO 2 escaping from the storage reservoir may migrate upwards towards regions with lower temperatures and pressures, where CO 2 would be in subcritical conditions. An assessment of the fate of leaking CO 2 requires a capability to model not only supercritical but also subcritical CO 2 , as well as phase changes between liquid and gaseous CO 2 in sub-critical conditions. We have developed a methodology for numerically simulating the behavior of water-CO 2 mixtures in permeable media under conditions that may include liquid, gaseous, and supercritical CO 2 . This has been applied to simulations of leakage from a deep storage reservoir in which a rising CO 2 plume undergoes transitions from supercritical to subcritical conditions. We find strong cooling effects when liquid CO 2 rises to elevations where it begins to boil and evolve a gaseous CO 2 phase. A three-phase zone forms (aqueous - liquid - gas), which over time becomes several hundred meters thick as decreasing temperatures permit liquid CO 2 to advance to shallower elevations. Fluid mobilities are reduced in the three-phase region from phase interference effects. This impedes CO 2 upflow, causes the plume to spread out laterally, and gives rise to dispersed CO 2 discharge at the land surface. Our simulation suggests that temperatures along a CO 2 leakage path may decline to levels low enough so that solid water ice and CO 2 hydrate phases may be formed

  4. Strong Dependence of Hydration State of F-Actin on the Bound Mg(2+)/Ca(2+) Ions.

    Science.gov (United States)

    Suzuki, Makoto; Imao, Asato; Mogami, George; Chishima, Ryotaro; Watanabe, Takahiro; Yamaguchi, Takaya; Morimoto, Nobuyuki; Wazawa, Tetsuichi

    2016-07-21

    Understanding of the hydration state is an important issue in the chemomechanical energetics of versatile biological functions of polymerized actin (F-actin). In this study, hydration-state differences of F-actin by the bound divalent cations are revealed through precision microwave dielectric relaxation (DR) spectroscopy. G- and F-actin in Ca- and Mg-containing buffer solutions exhibit dual hydration components comprising restrained water with DR frequency f2 (fw). The hydration state of F-actin is strongly dependent on the ionic composition. In every buffer tested, the HMW signal Dhyme (≡ (f1 - fw)δ1/(fwδw)) of F-actin is stronger than that of G-actin, where δw is DR-amplitude of bulk solvent and δ1 is that of HMW in a fixed-volume ellipsoid containing an F-actin and surrounding water in solution. Dhyme value of F-actin in Ca2.0-buffer (containing 2 mM Ca(2+)) is markedly higher than in Mg2.0-buffer (containing 2 mM Mg(2+)). Moreover, in the presence of 2 mM Mg(2+), the hydration state of F-actin is changed by adding a small fraction of Ca(2+) (∼0.1 mM) and becomes closer to that of the Ca-bound form in Ca2.0-buffer. This is consistent with the results of the partial specific volume and the Cotton effect around 290 nm in the CD spectra, indicating a change in the tertiary structure and less apparent change in the secondary structure of actin. The number of restrained water molecules per actin (N2) is estimated to be 1600-2100 for Ca2.0- and F-buffer and ∼2500 for Mg2.0-buffer at 10-15 °C. These numbers are comparable to those estimated from the available F-actin atomic structures as in the first water layer. The number of HMW molecules is roughly explained by the volume between the equipotential surface of -kT/2e and the first water layer of the actin surface by solving the Poisson-Boltzmann equation using UCSF Chimera.

  5. In situ measurement of magnesium carbonate formation from CO2 using static high-pressure and -temperature 13C NMR.

    Science.gov (United States)

    Surface, J Andrew; Skemer, Philip; Hayes, Sophia E; Conradi, Mark S

    2013-01-02

    We explore a new in situ NMR spectroscopy method that possesses the ability to monitor the chemical evolution of supercritical CO(2) in relevant conditions for geological CO(2) sequestration. As a model, we use the fast reaction of the mineral brucite, Mg(OH)(2), with supercritical CO(2) (88 bar) in aqueous conditions at 80 °C. The in situ conversion of CO(2) into metastable and stable carbonates is observed throughout the reaction. After more than 58 h of reaction, the sample was depressurized and analyzed using in situ Raman spectroscopy, where the laser was focused on the undisturbed products through the glass reaction tube. Postreaction, ex situ analysis was performed on the extracted and dried products using Raman spectroscopy, powder X-ray diffraction, and magic-angle spinning (1)H-decoupled (13)C NMR. These separate methods of analysis confirmed a spatial dependence of products, possibly caused by a gradient of reactant availability, pH, and/or a reaction mechanism that involves first forming hydroxy-hydrated (basic, hydrated) carbonates that convert to the end-product, anhydrous magnesite. This carbonation reaction illustrates the importance of static (unmixed) reaction systems at sequestration-like conditions.

  6. Communication: Quantitative Fourier-transform infrared data for competitive loading of small cages during all-vapor instantaneous formation of gas-hydrate aerosols

    Science.gov (United States)

    Uras-Aytemiz, Nevin; Abrrey Monreal, I.; Devlin, J. Paul

    2011-10-01

    A simple method has been developed for the measurement of high quality FTIR spectra of aerosols of gas-hydrate nanoparticles. The application of this method enables quantitative observation of gas hydrates that form on subsecond timescales using our all-vapor approach that includes an ether catalyst rather than high pressures to promote hydrate formation. The sampling method is versatile allowing routine studies at temperatures ranging from 120 to 210 K of either a single gas or the competitive uptake of different gas molecules in small cages of the hydrates. The present study emphasizes hydrate aerosols formed by pulsing vapor mixtures into a cold chamber held at 160 or 180 K. We emphasize aerosol spectra from 6 scans recorded an average of 8 s after "instantaneous" hydrate formation as well as of the gas hydrates as they evolve with time. Quantitative aerosol data are reported and analyzed for single small-cage guests and for mixed hydrates of CO2, CH4, C2H2, N2O, N2, and air. The approach, combined with the instant formation of gas hydrates from vapors only, offers promise with respect to optimization of methods for the formation and control of gas hydrates.

  7. Green remediation of contaminated sediment by stabilization/solidification with industrial by-products and CO2 utilization.

    Science.gov (United States)

    Wang, Lei; Chen, Liang; Tsang, Daniel C W; Li, Jiang-Shan; Yeung, Tiffany L Y; Ding, Shiming; Poon, Chi Sun

    2018-08-01

    Navigational dredging is an excavation of marine/freshwater sediment to maintain channels of sufficient depth for shipping safety. Due to historical inputs of anthropogenic contaminants, sediments are often contaminated by metals/metalloids, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and other contaminants. Its disposal can present significant environmental and financial burdens. This study developed a novel and green remediation method for contaminated sediment using stabilization/solidification with calcium-rich/low-calcium industrial by-products and CO 2 utilization. The hydration products were evaluated by quantitative X-ray diffraction analysis and thermogravimetric analysis. The incorporation of calcium carbide residue (CCR) facilitated hydration reaction and provided relatively high 7-d strength. In contrast, the addition of Class-F pulverized fly ash (PFA) and ground granulated blast furnace slag (GGBS) was beneficial to the 28-d strength development due to supplementary pozzolanic and hydration reactions. The employment of 1-d CO 2 curing was found to promote strength development (98%) and carbon sequestration (4.3wt%), while additional 7-d air curing facilitated cement rehydration and further carbonation in the sediment blocks. The leachability tests indicated that all studied binders, especially CCR binder, effectively immobilized contaminants in the sediments. The calcium-rich CCR and GGBS were regarded as promising candidates for augmenting the efficacy of CO 2 curing, whereas GGBS samples could be applicable as eco-paving blocks in view of their superior 28-d strength. This study presents a new and sustainable way to transform contaminated sediment into value-added materials. Copyright © 2018 Elsevier B.V. All rights reserved.

  8. The economics of exploiting gas hydrates

    International Nuclear Information System (INIS)

    Döpke, Lena-Katharina; Requate, Till

    2014-01-01

    We investigate the optimal exploitation of methane hydrates, a recent discovery of methane resources under the sea floor, mainly located along the continental margins. Combustion of methane (releasing CO2) and leakage through blow-outs (releasing CH4) contribute to the accumulation of greenhouse gases. A second externality arises since removing solid gas hydrates from the sea bottom destabilizes continental margins and thus increases the risk of marine earthquakes. We show that in such a model three regimes can occur: i) resource exploitation will be stopped in finite time, and some of the resource will stay in situ, ii) the resource will be used up completely in finite time, and iii) the resource will be exhausted in infinite time. We also show how to internalize the externalities by policy instruments. - Highlights: • We set up a model of optimal has hydrate exploitation • We incorporate to types of damages: contribution to global warming and geo-hazards • We characterize optimal exploitation paths and study decentralization with an exploitation tax. • Three regimes can occur: • i) exploitation in finite time and some of the stock remaining in situ, • ii) exploitation in finite time and the resource will be exhausted, • iii) exploitation and exhaustion in infinite time

  9. Unraveling the reaction mechanism on nitrile hydration catalyzed by [Pd(OH2)4]2+: insights from theory.

    Science.gov (United States)

    Tílvez, Elkin; Menéndez, María I; López, Ramón

    2013-07-01

    Density functional theory methodologies combined with continuum and discrete-continuum descriptions of solvent effects were used to investigate the [Pd(OH2)4](2+)-catalyzed acrylonitrile hydration to yield acrylamide. According to our results, the intramolecular hydroxide attack mechanism and the external addition mechanism of a water molecule with rate-determining Gibbs energy barriers in water solution of 27.6 and 28.3 kcal/mol, respectively, are the most favored. The experimental kinetic constants of the hydration started by hydroxide, k(OH), and water, k(H2O), attacks for the cis-[Pd(en)(OH2)2](2+)-catalyzed dichloroacetonitrile hydration rendered Gibbs energy barriers whose energy difference, 0.7 kcal/mol, is the same as that obtained in the present study. Our investigation reveals the nonexistence of the internal attack of a water ligand for Pd-catalyzed nitrile hydration. At the low pHs used experimentally, the equilibrium between [Pd(OH2)3(nitrile)](2+) and [Pd(OH2)2(OH)(nitrile)](+) is completely displaced to [Pd(OH2)3(nitrile)](2+). Experimental studies in these conditions stated that water acts as a nucleophile, but they could not distinguish whether it was a water ligand, an external water molecule, or a combination of both possibilities. Our theoretical explorations clearly indicate that the external water mechanism becomes the only operative one at low pHs. On the basis of this mechanistic proposal it is also possible to ascribe an (1)H NMR signal experimentally detected to the presence of a unidentate iminol intermediate and to explain the influence of nitrile concentration reported experimentally for nitriles other than acrylonitrile in the presence of aqua-Pd(II) complexes. Therefore, our theoretical point of view on the mechanism of nitrile hydration catalyzed by aqua-Pd(II) complexes can shed light on these relevant processes at a molecular level as well as afford valuable information that can help in designing new catalysts in milder and more

  10. Indian continental margin gas hydrate prospects : results of the Indian National Gas Hydrate Program (NGHP) expedition 01

    Energy Technology Data Exchange (ETDEWEB)

    Collett, T [United States Geological Survey, Denver, CO (United States); Riedel, M. [McGill Univ., Montreal, PQ (Canada). Dept. of Earth and Planetary Sciences; Cochran, J.R. [Columbia Univ., Palisades, NY (United States). Lamont Doherty Earth Observatory; Boswell, R. [United States Dept. of Energy, Morgantown, WV (United States). National Energy Technology Lab; Kumar, P. [Pushpendra Kumar Oil and Natural Gas Corp. Ltd., Mumbai (India). Inst. of Engineering and Ocean Technology; Sathe, A.V. [Oil and Natural Gas Corp. Ltd., Uttaranchal (India). KDM Inst. of Petroleum Exploration

    2008-07-01

    The geologic occurrence of gas hydrate deposits along the continental margins of India were investigated in the first expedition of the Indian National Gas Hydrate Program (NGHP). The objective was to determine the regional context and characteristics of the gas hydrate deposits through scientific ocean drilling, logging, and analytical activities. A research drill ship was the platform for the drilling operation. The geological and geophysical studies revealed 2 geologically distinct areas with inferred gas hydrate occurrences, notably the passive continental margins of the Indian Peninsula and along the Andaman convergent margin. The NGHP Expedition 01 focused on understanding the geologic and geochemical controls on the occurrence of gas hydrate in these 2 diverse settings. The study established the presence of gas hydrates in Krishna-Godavari, Mahanadi and Andaman basins. Site 10 in the Krishna-Godavari Basin was discovered to be the one of the richest gas hydrate accumulations yet documented, while site 17 in the Andaman Sea had the thickest and deepest gas hydrate stability zone yet known. The existence of a fully-developed gas hydrate system in the Mahanadi Basin was also discovered. Most of the gas hydrate occurrences discovered during this expedition appeared to contain mostly methane which was generated by microbial processes. However, there was also evidence of a thermal origin for a portion of the gas within the hydrates of the Mahanadi Basin and the Andaman offshore area. Gas hydrate in the Krishna-Godavari Basin appeared to be closely associated with large scale structural features, in which the flux of gas through local fracture systems, generated by the regional stress regime, controlled the occurrence of gas hydrate. 3 refs., 1 tab., 2 figs.

  11. Vibrational spectra of the hydrated carbonate minerals ikaite, monohydrocalcite, lansfordite and nesquehonite

    Science.gov (United States)

    Coleyshaw, Esther E.; Crump, Gregory; Griffith, William P.

    2003-08-01

    The Raman (200-4000 cm -1) and infrared (600-4000 cm -1) spectra of four rare carbonate hydrate minerals are reported. These are naturally occurring and synthetic ikaite CaCO 3 · 6H 2O, and nesquehonite MgCO 3 · 3H 2O; natural monohydrocalcite CaCO 3 · H 2O, and synthetic lansfordite MgCO 3 · 5H 2O. The spectra of synthetic ikaite partially substituted with 2H 2O and also with 13C were measured, as were those of synthetic deuteriated nesquehonite. Spectra of ikaite and lansfordite, both of which decompose at room temperatures, were measured below 0 °C. Assignments of fundamental modes are proposed.

  12. Gene encoding gamma-carbonic anhydrase is cotranscribed with argC and induced in response to stationary phase and high CO2 in Azospirillum brasilense Sp7.

    Science.gov (United States)

    Kaur, Simarjot; Mishra, Mukti N; Tripathi, Anil K

    2010-07-04

    Carbonic anhydrase (CA) is a ubiquitous enzyme catalyzing the reversible hydration of CO2 to bicarbonate, a reaction underlying diverse biochemical and physiological processes. Gamma class carbonic anhydrases (gamma-CAs) are widespread in prokaryotes but their physiological roles remain elusive. At present, only gamma-CA of Methanosarcina thermophila (Cam) has been shown to have CA activity. Genome analysis of a rhizobacterium Azospirillum brasilense, revealed occurrence of ORFs encoding one beta-CA and two gamma-CAs. One of the putative gamma-CA encoding genes of A. brasilense was cloned and overexpressed in E. coli. Electrometric assays for CA activity of the whole cell extracts overexpressing recombinant GCA1 did not show CO2 hydration activity. Reverse transcription-PCR analysis indicated that gca1 in A. brasilense is co-transcribed with its upstream gene annotated as argC, which encodes a putative N-acetyl-gamma-glutamate-phosphate reductase. 5'-RACE also demonstrated that there was no transcription start site between argC and gca1, and the transcription start site located upstream of argC transcribed both the genes (argC-gca1). Using transcriptional fusions of argC-gca1 upstream region with promoterless lacZ, we further demonstrated that gca1 upstream region did not have any promoter and its transcription occurred from a promoter located in the argC upstream region. The transcription of argC-gca1 operon was upregulated in stationary phase and at elevated CO2 atmosphere. This study shows lack of CO2 hydration activity in a recombinant protein expressed from a gene predicted to encode a gamma-carbonic anhydrase in A. brasilense although it cross reacts with anti-Cam antibody raised against a well characterized gamma-CA. The organization and regulation of this gene along with the putative argC gene suggests its involvement in arginine biosynthetic pathway instead of the predicted CO2 hydration.

  13. Processes for the control of 14CO2 during reprocessing

    International Nuclear Information System (INIS)

    Notz, K.J.; Holladay, D.W.; Forsberg, C.W.; Haag, G.L.

    1980-01-01

    The fixation of 14 CO 2 may be required at some future time because of the significant fractional contribution of 14 C, via the ingestion pathway, to the total population dose from the nuclear fuel cycle, even though the actual quantity of this dose is very small when compared to natural background. The work described here was done in support of fuel reprocessing development, of both graphite fuel (HTGRs) and metal-clad fuel (LWRs and LMFBRs), and was directed to the control of 14 CO 2 released during reprocessing operations. However, portions of this work are also applicable to the control of 14 CO 2 released during reactor operation. The work described falls in three major areas: (1) The application of liquid-slurry fixation with Ca(OH) 2 , which converts the CO 2 to CaCO 3 , carried out after treatment of the CO 2 -containing stream to remove other gaseous radioactive components, mainly 85 Kr. This approach is primarily for application to HTGR fuel reprocessing. (2) The above process for CO 2 fixation, but used ahead of Kr removal, and followed by a molecular sieve process to take out the 85 Kr. This approach was developed for use with HTGR reprocessing, but certain aspects also have application to metal-clad fuel reprocessing and to reactor operation. (3) The use of solid Ba(OH) 2 hydrate reacting directly with the gaseous phase. This process is generally applicable to both reprocessing and to reactor operation

  14. NH3 quantum rotators in Hofmann clathrates: intensity and width of rotational transition lines

    International Nuclear Information System (INIS)

    Vorderwisch, Peter; Sobolev, Oleg; Desmedt, Arnaud

    2004-01-01

    Inelastic structure factors for rotational transitions of uniaxial NH 3 quantum rotators, measured in a Hofmann clathrate with biphenyl as guest molecule, agree with those calculated for free rotators. A finite intrinsic line width, found for rotational transitions involving the rotational level j=3 at low temperature, supports a recently suggested model based on resonant rotor-rotor coupling

  15. Pressure/temperature fluid cell apparatus for the neutron powder diffractometer instrument: Probing atomic structure in situ

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hsiu-Wen; Fanelli, Victor R.; Reiche, Helmut M.; Larson, Eric; Taylor, Mark A.; Siewenie, Joan [Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Xu, Hongwu [Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Zhu, Jinlong [High Pressure Science and Engineering Center, Department of Physics and Astronomy, The University of Nevada, Las Vegas, Nevada 89154, USA and National Lab for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Page, Katharine, E-mail: pagekl@ornl.gov [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2014-12-15

    This contribution describes a new local structure compatible gas/liquid cell apparatus for probing disordered materials at high pressures and variable temperatures in the Neutron Powder Diffraction instrument at the Lujan Neutron Scattering Center, Los Alamos National Laboratory. The new sample environment offers choices for sample canister thickness and canister material type. Finite element modeling is utilized to establish maximum allowable working pressures of 414 MPa at 15 K and 121 MPa at 600 K. High quality atomic pair distribution function data extraction and modeling have been demonstrated for a calibration standard (Si powder) and for supercritical and subcritical CO{sub 2} measurements. The new sample environment was designed to specifically target experimental studies of the local atomic structures involved in geologic CO{sub 2} sequestration, but will be equally applicable to a wide variety of energy applications, including sorption of fluids on nano/meso-porous solids, clathrate hydrate formation, catalysis, carbon capture, and H{sub 2} and natural gas uptake/storage.

  16. Geodetic data support trapping of ethane in Titan's polar crust

    Science.gov (United States)

    Sotin, Christophe; Rambaux, Nicolas

    2016-04-01

    Titan's surface is characterized by polar depressions that strongly influence interpretations of the gravity data. This study investigates several geodynamical models that can explain these depressions. For each model, the values of the three moments of inertia are computed numerically by discretizing the interior in spherical coordinates. The study shows that a Pratt model where the polar subsurface is made of ethane clathrates can explain the polar depression, the abrupt jump in altitude at about 60 degrees latitude, and the values of the degree 2 gravity coefficients. This model, proposed by Choukroun and Sotin [1], is based on the stability of ethane clathrate hydrates relative to methane clathrate hydrates. In addition to fitting the geodetic data, it explains the absence of ethane in Titan's atmosphere although ethane is the main product of the photolysis of methane. Other geophysical models based on latitudinal variations in the tidal heating production or in the heat flux at the base of the icy crust do not provide such a good match to the gravity and topographic observations. The ethane-clathrate model predicts that all the ethane produced by photolysis of methane at the present rate during the last billion years could be stored in the polar subsurface. It is consistent with the age of Titan's surface and that of Titan's atmospheric methane inferred from geological and geochemical observations by the Cassini/Huygens mission. The present study also emphasizes the role of mass anomalies on the interpretation of the degree 2 gravity coefficients. It shows that for Titan, a slow rotator, the values of the two equatorial moments of inertia (MoI) are largely affected by the polar depressions whereas the value of polar MoI is not. Therefore, as pointed out by previous calculations [2], calculating the moment of inertia (MoI) factor from the value of J2 could lead to major errors. This is not the case for our preferred Titan's model for which the negative polar

  17. Mathematical model of the methane replacement by carbon dioxide in the gas hydrate reservoir taking into account the diffusion kinetics

    Science.gov (United States)

    Musakaev, N. G.; Khasanov, M. K.; Rafikova, G. R.

    2018-03-01

    The problem of the replacement of methane in its hydrate by carbon dioxide in a porous medium is considered. The gas-exchange kinetics scheme is proposed in which the intensity of the process is limited by the diffusion of CO2 through the hydrate layer formed between the gas mixture flow and the CH4 hydrate. Dynamics of the main parameters of the process is numerically investigated. The main characteristic stages of the process are determined.

  18. Changes in structure and preferential cage occupancy of ethane hydrate and ethane-methane mixed gas hydrate under high pressure

    International Nuclear Information System (INIS)

    Hirai, H; Takahara, N; Kawamura, T; Yamamoto, Y; Yagi, T

    2010-01-01

    Structural changes and preferential cage occupancies were examined for ethane hydrate and ethane-methane mixed gas hydrates with five compositions in a pressure range of 0.2 to 2.8 GPa at room temperature. X-ray diffractometry and Raman spectroscopy showed the following structural changes. The initial structure, structure I (sI), of ethane hydrate was retained up to 2.1 GPa without any structural change. For the mixed hydrates, sI was widely distributed throughout the region examined except for the methane-rich and lower pressure regions, where sII and sH appeared. Above 2.1 GPa ethane hydrate and all of the mixed hydrates decomposed into ice VI and ethane fluid or methane-ethane fluid, respectively. The Raman study revealed that occupation of the small cages by ethane molecules occurred above 0.1 GPa in ethane hydrate and continued up to decomposition at 2.1 GPa, although it was thought that ethane molecules were contained only in the large cage.

  19. Atmospheric chemistry of perfluorinated aldehyde hydrates (n-C(x)F(2x+1)CH(OH)2, x = 1, 3, 4)

    DEFF Research Database (Denmark)

    Andersen, Mads Peter Sulbæk; Toft, A.; Nielsen, O.J.

    2006-01-01

    . Bubbling CF(3)CHO/air mixtures through liquid water led to >80% conversion of CF(3)CHO into the hydrate within the approximately 2 s taken for passage through the bubbler. These results suggest that OH radical initiated oxidation of C(x)F(2x+1)CH(OH)(2) hydrates could be a significant source...

  20. Barley seed radiosensitivity following post-hydration in oxygen-, nitrogen- and nitrous oxide-saturated water, 1

    International Nuclear Information System (INIS)

    Singh, S.P.; Kesavan, P.C.

    1990-01-01

    Dry (∼3.5 and 4.0 per cent moisture content) barley seeds were exposed to 350 Gy of 60 Co-γ-rays in vacuo and post-hydrated at 4degC for 8 h in O 2 -, N 2 -, or N 2 O-saturated water. The effect of caffeine and t-butyl alcohol (t-BuOH) dissolved in the post-hydration medium on the magnitude of damage developing under these three different gaseous circumstances was studied. The post-irradiation damage and its modification by caffeine and t-BuOH was assessed in terms of 8-day-old seedling injury, peroxidase activity and total peroxides in the 8-day-old seedlings. Post-irradiation O 2 -saturated hydration caused maximal 8-day-old seedling injury, and increased peroxidase activity with concomitant reduction in total peroxides. Both caffeine and t-BuOH afforded significant radioprotection against post-irradiation O 2 -dependent damage. Post-irradiation N 2 O-saturated hydration was even more significantly radioprotective than the N 2 -saturated post-hydration. Under these circumstances, t-BuOH exerted no effect whatsoever on the N 2 - and N 2 O-mediated post-irradiation damage. Caffeine, on the other hand, significantly potentiated these two components of damage. A brief consideration of the physicochemical events which possibly account for the observed effects is presented. (author)

  1. Multi-channel electrical impedance tomography for regional tissue hydration monitoring

    International Nuclear Information System (INIS)

    Chen, Xiaohui; Kao, Tzu-Jen; Ashe, Jeffrey M; Boverman, Gregory; Sabatini, James E; Davenport, David M

    2014-01-01

    Poor assessment of hydration status during hemodialysis can lead to under- or over-hydration in patients with consequences of increased morbidity and mortality. In current practice, fluid management is largely based on clinical assessments to estimate dry weight (normal hydration body weight). However, hemodialysis patients usually have co-morbidities that can make the signs of fluid status ambiguous. Therefore, achieving normal hydration status remains a major challenge for hemodialysis therapy. Electrical impedance technology has emerged as a promising method for hydration monitoring due to its non-invasive nature, low cost and ease-of-use. Conventional electrical impedance-based hydration monitoring systems employ single-channel current excitation (either 2-electrode or 4-electrode methods) to perturb and extract averaged impedance from bulk tissue and use generalized models from large populations to derive hydration estimates. In the present study, a prototype, single-frequency electrical impedance tomography (EIT) system with simultaneous multi-channel current excitation was used to enable regional hydration change detection. We demonstrated the capability to detect a difference in daily impedance change between left leg and right leg in healthy human subjects, who wore a compression sock only on one leg to reduce daily gravitational fluid accumulation. The impedance difference corresponded well with the difference of lower leg volume change between left leg and right leg measured by volumetry, which on average is ∼35 ml, accounting for 0.7% of the lower leg volume. We have demonstrated the feasibility of using multi-channel EIT to extract hydration information in different tissue layers with minimal skin interference. Our simultaneous, multi-channel current excitation approach provides an effective method to separate electrode contact impedance and skin condition artifacts from hydration signals. The prototype system has the potential to be used in

  2. Multi-channel electrical impedance tomography for regional tissue hydration monitoring.

    Science.gov (United States)

    Chen, Xiaohui; Kao, Tzu-Jen; Ashe, Jeffrey M; Boverman, Gregory; Sabatini, James E; Davenport, David M

    2014-06-01

    Poor assessment of hydration status during hemodialysis can lead to under- or over-hydration in patients with consequences of increased morbidity and mortality. In current practice, fluid management is largely based on clinical assessments to estimate dry weight (normal hydration body weight). However, hemodialysis patients usually have co-morbidities that can make the signs of fluid status ambiguous. Therefore, achieving normal hydration status remains a major challenge for hemodialysis therapy. Electrical impedance technology has emerged as a promising method for hydration monitoring due to its non-invasive nature, low cost and ease-of-use. Conventional electrical impedance-based hydration monitoring systems employ single-channel current excitation (either 2-electrode or 4-electrode methods) to perturb and extract averaged impedance from bulk tissue and use generalized models from large populations to derive hydration estimates. In the present study, a prototype, single-frequency electrical impedance tomography (EIT) system with simultaneous multi-channel current excitation was used to enable regional hydration change detection. We demonstrated the capability to detect a difference in daily impedance change between left leg and right leg in healthy human subjects, who wore a compression sock only on one leg to reduce daily gravitational fluid accumulation. The impedance difference corresponded well with the difference of lower leg volume change between left leg and right leg measured by volumetry, which on average is ~35 ml, accounting for 0.7% of the lower leg volume. We have demonstrated the feasibility of using multi-channel EIT to extract hydration information in different tissue layers with minimal skin interference. Our simultaneous, multi-channel current excitation approach provides an effective method to separate electrode contact impedance and skin condition artifacts from hydration signals. The prototype system has the potential to be used in clinical

  3. Effect of MXene (Nano-Ti3C2 on Early-Age Hydration of Cement Paste

    Directory of Open Access Journals (Sweden)

    Haibin Yin

    2015-01-01

    Full Text Available As a new two-dimensional material, MXene (nano-Ti3C2 has been widely applied in many fields, especially for reinforced composite materials. In this paper, mechanical testing, X-ray diffraction (XRD, hydration heat, scanning electron microscope (SEM, and EDS analysis were used to analyze the impact of MXene on cement hydration properties. The obtained results revealed that (a MXene could greatly improve the early compressive strength of cement paste with 0.04 wt% concentration, (b the phase type of early-age hydration products has not been changed after the addition of MXene, (c hydration exothermic rate within 72 h has small difference at different amount of MXene, and (d morphologies of hydration products were varied with the dosage of MXene, a lot of tufted ettringites appeared in 3 d hydration products when the content of MXene was 0.04 wt%, which will have a positive effect on improving the early mechanical properties of cement paste. MXene has inhibited the Portland cement hydration process; the main role of MXene in the cement hydration process is to promote the messy ettringite becoming regular distribution at a node and form network connection structure in the crystals growth process, making the mechanics performance of cement paste significantly improved.

  4. Metal chloride hydrates as Lewis acid catalysts in multicomponent synthesis of 2,4,5-triarylimidazoles or 2,4,5-triaryloxazoles

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Marcelo V. [Departamento de Engenharia de Processos, Fundacao de Ciencia e Tecnologia, Cachoeirinha, RS (Brazil); Russowsky, Dennis, E-mail: dennis@iq.ufrgs.br [Laboratorio de Sinteses Organicas, Instituto de Quimica, Universidade Federal do Rio Grande do Sul, Porto Alegre-RS (Brazil); Ruthner, Marcelo M.; Fontoura, Luiz A.M. [Curso de Quimica, Universidade Luterana do Brasil, Canoas, RS (Brazil)

    2012-07-01

    A series of nine metal chloride hydrates (ZnCl{sub 2}.2H{sub 2}O, SnCl{sub 2}.2H{sub 2}O, CdCl{sub 2}.2H{sub 2}O, MnCl{sub 2}.4H{sub 2}O, CoCl{sub 2}.6H{sub 2}O, SrCl{sub 2}.6H{sub 2}O, NiCl{sub 2}.6H{sub 2}O, CrCl{sub 3}.6H{sub 2}O and CeCl{sub 3}.7H{sub 2}O) was investigated as mild and inexpensive Lewis acid catalysts to promote the multicomponent synthesis of triarylimidazoles. Reactions starting from benzil showed the best results when SnCl{sub 2}.2H{sub 2}O was used, while for benzoin as the starting material, CeCl{sub 3}.7H{sub 2}O was more efficient. All reactions were performed in EtOH as solvent. These catalysts were also successfully employed in the synthesis of triaryloxazoles. (author)

  5. Effects of chlorides on the hydration of 12CaO{center_dot}7Al2O3 solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Sango, H.; Miyakawa, T.; Yasue, T.; Arai, Y. [Nihon Univ., Tokyo (Japan). Faculty of Science and Engineering

    1995-01-01

    The purpose of this paper was to compare the hydration rate of C12A7ss and to study the effects of chlorides on the hydration products and the hydration rate of C12A7ss. In this paper, `C12A7ss` is a general term for C11A7{center_dot}Ca(OH)2, 11CaO{center_dot}7Al2O3{center_dot}CaF2 and 11CaO{center_dot}7Al2O3{center_dot}CaCl2. The hydration process and the hydration rate of 12CaO{center_dot}7Al2O3 solution (C12A7ss) with and without various chlorides (CaCl2, MgCl2, NaCl, NH4Cl and AlCl3) has been determined at 25{degree}C. Various C12A7ss were prepared in burning method. When C12A7ss with various chlorides are hydrated, 3CaO{center_dot} Al2O3{center_dot}CaCl2{center_dot}10H2O(Friedel`s salt) is formed as the primary hydrate. The hydration rate of C12A7ss is decreased by the coexistence of CaCl2, MgCl2, NaCl or NH4Cl except AlCl3. As a result, the setting time of C12A7ss is extended and the unhydrate exists for a long time comparatively. 14 refs., 7 figs., 1 tab.

  6. Hydrate-CASM for modeling Methane Hydrate-Bearing Sediments

    Science.gov (United States)

    De La Fuente Ruiz, M.; Vaunat, J.; Marin Moreno, H.

    2017-12-01

    A clear understanding of the geomechanical behavior of methane hydrate-bearing sediments (MHBS) is crucial to assess the stability of the seafloor and submarine infrastructures to human and natural loading changes. Here we present the Hydrate-CASM, a new elastoplastic constitutive model to predict the geomechanical behavior of MHBS. Our model employs the critical state model CASM (Clay and Sand Model) because of its flexibility in describing the shape of the yield surface and its proven ability to predict the mechanical behavior of sands, the most commercially viable hydrate reservoirs. The model considers MHBS as a deformable elastoplastic continuum, and hydrate-related changes in the stress-strain behavior are predicted by a densification mechanism. The densification attributes the mechanical contribution of hydrate to; a reduction of the available void ratio; a decrease of the swelling line slope; and an increase of the volumetric yield stress. It is described by experimentally derived physical parameters except from the swelling slope coefficient that requires empirical calibration. The Hydrate-CASM is validated against published triaxial laboratory tests performed at different confinement stresses, hydrate saturations, and hydrate morphologies. During the validation, we focused on capturing the mechanical behavior of the host sediment and consider perturbations of the sediment's mechanical properties that could result from the sample preparation. Our model successfully captures the experimentally observed influence of hydrate saturation in the magnitude and trend of the stiffness, shear strength, and dilatancy of MHBS. Hence, we propose that hydrate-related densification changes might be a major factor controlling the geomechanical response of MHBS.

  7. Early Mars serpentinization-derived CH4 reservoirs, H2 induced warming and paleopressure evolution

    Science.gov (United States)

    Lasue, J.; Chassefiere, E.; Langlais, B.; Quesnel, Y.

    2016-12-01

    CH4 has been observed on Mars both by remote sensing and in situ during the past 15 years. Early Mars serpentinization is one possible abiotic mechanism that could not only produce methane, but also explain the observed Martian remanent magnetic field. Assuming a cold early Mars, a cryosphere could trap such CH4 as clathrates in stable form at depth. We recently estimated the maximum storage capacity of such clathrate layer to be about 2x1019 to 2x1020 moles of methane. Such reservoirs may be stable or unstable, depending on many factors that are poorly constrained: major and sudden geological events such as the Tharsis bulge formation, the Hellas impact or the martian polar wander, could have destabilized the clathrates early in the history of the planet and released large quantities of gas in the atmosphere. Here we estimate the associated amounts of serpentinization-derived CH4 stored in the cryosphere that have been released to the atmosphere at the end of the Noachian and the beginning of the Hesperian. Due to rapid clathrate dissociation and photochemical conversion of CH4 to H2, these episodes of massive CH4 release may have resulted in transient H2-rich atmospheres, at typical levels of 10-20% in a background 1-2 bar CO2 atmosphere. We propose that the early Mars cryosphere had a sufficient CH4 storage capacity to have maintained H2-rich transient atmospheres during a total time period up to several Myr or tens of Myr, having potentially contributed - by collision-induced heating effect of atmospheric H2 - to the formation of valley networks during the late Noachian and early Hesperian.

  8. Global Energy Issues and Alternate Fueling

    Science.gov (United States)

    Hendricks, Robert C.

    2007-01-01

    This viewgraph presentation describes world energy issues and alternate fueling effects on aircraft design. The contents include: 1) US Uses about 100 Quad/year (1 Q = 10(exp 15) Btu) World Energy Use: about 433 Q/yr; 2) US Renewable Energy about 6%; 3) Nuclear Could Grow: Has Legacy Problems; 4) Energy Sources Primarily NonRenewable Hydrocarbon; 5) Notes; 6) Alternate Fuels Effect Aircraft Design; 7) Conventional-Biomass Issue - Food or Fuel; 8) Alternate fuels must be environmentally benign; 9) World Carbon (CO2) Emissions Problem; 10) Jim Hansen s Global Warming Warnings; 11) Gas Hydrates (Clathrates), Solar & Biomass Locations; 12) Global Energy Sector Response; 13) Alternative Renewables; 14) Stratospheric Sulfur Injection Global Cooling Switch; 15) Potential Global Energy Sector Response; and 16) New Sealing and Fluid Flow Challenges.

  9. Hydration rate of obsidian.

    Science.gov (United States)

    Friedman, I; Long, W

    1976-01-30

    The hydration rates of 12 obsidian samples of different chemical compositions were measured at temperatures from 95 degrees to 245 degrees C. An expression relating hydration rate to temperature was derived for each sample. The SiO(2) content and refractive index are related to the hydration rate, as are the CaO, MgO, and original water contents. With this information it is possible to calculate the hydration rate of a sample from its silica content, refractive index, or chemical index and a knowledge of the effective temperature at which the hydration occurred. The effective hydration temperature can be either measured or approximated from weather records. Rates have been calculated by both methods, and the results show that weather records can give a good approximation to the true EHT, particularly in tropical and subtropical climates. If one determines the EHT by any of the methods suggested, and also measures or knows the rate of hydration of the particular obsidian used, it should be possible to carry out absolute dating to +/- 10 percent of the true age over periods as short as several years and as long as millions of years.

  10. Model for gas hydrates applied to CCS systems part II. Fitting of parameters for models of hydrates of pure gases

    Czech Academy of Sciences Publication Activity Database

    Vinš, Václav; Jäger, A.; Hrubý, Jan; Span, R.

    2017-01-01

    Roč. 435, March (2017), s. 104-117 ISSN 0378-3812 R&D Projects: GA MŠk(CZ) 7F14466; GA ČR(CZ) GJ15-07129Y Institutional support: RVO:61388998 Keywords : carbon capture and storage * clathrate * parameter fitting Subject RIV: BJ - Thermodynamics Impact factor: 2.473, year: 2016 http://ac.els-cdn.com/S0378381216306069/1-s2.0-S0378381216306069-main.pdf?_tid=7b6bf82c-2f22-11e7-8661-00000aab0f02&acdnat=1493721260_17561db239dd867f17c2ad3bda9a5540

  11. Crystal structures of hydrates of simple inorganic salts. III. Water-rich aluminium halide hydrates: AlCl3 · 15H2O, AlBr3 · 15H2O, AlI3 · 15H2O, AlI3 · 17H2O and AlBr3 · 9H2O.

    Science.gov (United States)

    Schmidt, Horst; Hennings, Erik; Voigt, Wolfgang

    2014-09-01

    Water-rich aluminium halide hydrate structures are not known in the literature. The highest known water content per Al atom is nine for the perchlorate and fluoride. The nonahydrate of aluminium bromide, stable pentadecahydrates of aluminium chloride, bromide and iodide, and a metastable heptadecahydrate of the iodide have now been crystallized from low-temperature solutions. The structures of these hydrates were determined and are discussed in terms of the development of cation hydration spheres. The pentadecahydrate of the chloride and bromide are isostructural. In AlI(3) · 15H2O, half of the Al(3+) cations are surrounded by two complete hydration spheres, with six H2O in the primary and 12 in the secondary. For the heptadecahydrate of aluminium iodide, this hydration was found for every Al(3+).

  12. Low-δD hydration rinds in Yellowstone perlites record rapid syneruptive hydration during glacial and interglacial conditions

    Science.gov (United States)

    Bindeman, Ilya N.; Lowenstern, Jacob B.

    2016-01-01

    Hydration of silicic volcanic glass forms perlite, a dusky, porous form of altered glass characterized by abundant “onion-skin” fractures. The timing and temperature of perlite formation are enigmatic and could plausibly occur during eruption, during post-eruptive cooling, or much later at ambient temperatures. To learn more about the origin of natural perlite, and to fingerprint the hydration waters, we investigated perlitic glass from several synglacial and interglacial rhyolitic lavas and tuffs from the Yellowstone volcanic system. Perlitic cores are surrounded by a series of conchoidal cracks that separate 30- to 100-µm-thick slivers, likely formed in response to hydration-induced stress. H2O and D/H profiles confirm that most D/H exchange happens together with rapid H2O addition but some smoother D/H variations may suggest separate minor exchange by deuterium atom interdiffusion following hydration. The hydrated rinds (2–3 wt% H2O) transition rapidly (within 30 µm, or by 1 wt% H2O per 10 µm) to unhydrated glass cores. This is consistent with quenched “hydration fronts” where H2O diffusion coefficients are strongly dependent on H2O concentrations. The chemical, δ18O, and δD systematics of bulk glass records last equilibrium between ~110 and 60 °C without chemical exchange but with some δ18O exchange. Similarly, the δ18O of water extracted from glass by rapid heating suggests that water was added to the glass during cooling at higher rates of diffusion at 60–110 °C temperatures, compared with values expected from extrapolation of high-temperature (>400 °C) experimental data. The thick hydration rinds in perlites, measuring hundreds of microns, preserve the original D/H values of hydrating water as a recorder of paleoclimate conditions. Measured δD values in perlitic lavas are −150 to −191 or 20–40 ‰ lower than glass hydrated by modern Yellowstone waters. This suggests that Yellowstone perlites record the low-δD signature

  13. The Temperature Dependence of the Partition of CH4 and C2H6 in Structure I Hydrates

    Science.gov (United States)

    Cheng, H.; Lu, W.

    2017-12-01

    At present, we mainly use hydrocarbon gas and carbon isotope composition to determine the gas source of natural gas hydrate. Judging the type of gas source plays a key role in the evaluation of hydrate reservoirs, but there is still controversy over this approach. Considering the crystal properties of hydrate, the process of aggregation and decomposition of natural gas hydrates may have an important effect on the gas composition. We used CH4 (C1), C2H6 (C2) and their mixture as gas sources to synthesize hydrates from aqueous solution in high-pressure capillary tubes. Gas concentration in hydrates grew at different temperatures was measured with quantitative Raman spectroscopy. The results show that concentrations of gas in pure methane and pure ethane hydrates increase with temperature. The results of the mixture are similar to pure gas below 288.15 K, the concentration of C1 in small cages (SC, 512) slowly increased, but the competitive relationship between methane and ethane in large cages (LC, 51262) become obvious after 288.15 K. From 278.15 K to 294.15 K, the value of C1/C2 decreased from 26.38 to 6.61, gradually closing to the original gas composition of 4. We find that gas hydrates are more likely to gather C1 when they accumulate. The lower the temperature is, the more obvious it will be, and the closer the value of C1/C2 is to the microbial gases.

  14. Crystal structure of the sodium cobaltate deuterate superconductor NaxCoO2ṡ4xD2O (x≈1/3)

    Science.gov (United States)

    Jorgensen, J. D.; Avdeev, M.; Hinks, D. G.; Burley, J. C.; Short, S.

    2003-12-01

    Neutron and x-ray powder diffraction have been used to investigate the crystal structures of a sample of the newly-discovered superconducting sodium cobaltate deuterate compound with composition Na0.31(3)CoO2ṡ1.25(2)D2O and its anhydrous parent compound Na0.61(1)CoO2. The anhydrous parent compound Na0.61(1)CoO2 has two partially occupied Na sites sandwiched, in the same plane, between CoO2 layers. When Na is removed to make the superconducting composition, the Na site that experiences the strongest Na Co repulsion is emptied while the occupancy of the other Na site is reduced to about one third. The deuterate superconducting compound is formed by coordinating four D2O molecules (two above and two below) to each remaining Na ion in a way that gives Na O distances nearly equal to those in the parent compound. One deuteron of the D2O molecule is hydrogen bonded to an oxygen atom in the CoO2 plane and the oxygen atom and the second deuteron of each D2O molecule lie approximately in a plane between the Na layer and the CoO2 layers. This coordination of Na by four D2O molecules leads in a straightforward way to ordering of the Na ions and D2O molecules consistent with the observation of additional shorter-range scattering features in the diffraction data. The sample studied here, which has Tc=4.5 K, has a refined composition of Na0.31(3)CoO2ṡ1.25(2)D2O, in agreement with the expected 1:4 ratio of Na to D2O. These results show that the optimal superconducting composition should be viewed as a specific hydrated compound, not a solid solution of Na and D2O (H2O) in NaxCoO2ṡD2O. The hydrated superconducting compound may be stable over a limited range of Na and D2O concentration, but studies of Tc and other physical properties vs Na or D2O composition should be viewed with caution until it is verified that the compound remains in the same phase over the composition range of the study.

  15. Crystal structure of the sodium cobaltate deuterate superconductor NaxCoO2·4xD2O (x≅(1/3))

    International Nuclear Information System (INIS)

    Jorgensen, J.D.; Avdeev, M.; Hinks, D.G.; Burley, J.C.; Short, S.

    2003-01-01

    Neutron and x-ray powder diffraction have been used to investigate the crystal structures of a sample of the newly-discovered superconducting sodium cobaltate deuterate compound with composition Na 0.31(3) CoO 2 ·1.25(2)D 2 O and its anhydrous parent compound Na 0.61(1) CoO 2 . The anhydrous parent compound Na 0.61(1) CoO 2 has two partially occupied Na sites sandwiched, in the same plane, between CoO 2 layers. When Na is removed to make the superconducting composition, the Na site that experiences the strongest Na-Co repulsion is emptied while the occupancy of the other Na site is reduced to about one third. The deuterate superconducting compound is formed by coordinating four D 2 O molecules (two above and two below) to each remaining Na ion in a way that gives Na-O distances nearly equal to those in the parent compound. One deuteron of the D 2 O molecule is hydrogen bonded to an oxygen atom in the CoO 2 plane and the oxygen atom and the second deuteron of each D 2 O molecule lie approximately in a plane between the Na layer and the CoO 2 layers. This coordination of Na by four D 2 O molecules leads in a straightforward way to ordering of the Na ions and D 2 O molecules consistent with the observation of additional shorter-range scattering features in the diffraction data. The sample studied here, which has T c =4.5 K, has a refined composition of Na 0.31(3) CoO 2 ·1.25(2)D 2 O, in agreement with the expected 1:4 ratio of Na to D 2 O. These results show that the optimal superconducting composition should be viewed as a specific hydrated compound, not a solid solution of Na and D 2 O (H 2 O) in Na x CoO 2 ·D 2 O. The hydrated superconducting compound may be stable over a limited range of Na and D 2 O concentration, but studies of T c and other physical properties vs Na or D 2 O composition should be viewed with caution until it is verified that the compound remains in the same phase over the composition range of the study

  16. Scientific results of the Second Gas Hydrate Drilling Expedition in the Ulleung Basin (UBGH2)

    Science.gov (United States)

    Ryu, Byong-Jae; Collett, Timothy S.; Riedel, Michael; Kim, Gil-Young; Chun, Jong-Hwa; Bahk, Jang-Jun; Lee, Joo Yong; Kim, Ji-Hoon; Yoo, Dong-Geun

    2013-01-01

    As a part of Korean National Gas Hydrate Program, the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) was conducted from 9 July to 30 September, 2010 in the Ulleung Basin, East Sea, offshore Korea using the D/V Fugro Synergy. The UBGH2 was performed to understand the distribution of gas hydrates as required for a resource assessment and to find potential candidate sites suitable for a future offshore production test, especially targeting gas hydrate-bearing sand bodies in the basin. The UBGH2 sites were distributed across most of the basin and were selected to target mainly sand-rich turbidite deposits. The 84-day long expedition consisted of two phases. The first phase included logging-while-drilling/measurements-while-drilling (LWD/MWD) operations at 13 sites. During the second phase, sediment cores were collected from 18 holes at 10 of the 13 LWD/MWD sites. Wireline logging (WL) and vertical seismic profile (VSP) data were also acquired after coring operations at two of these 10 sites. In addition, seafloor visual observation, methane sensing, as well as push-coring and sampling using a Remotely Operated Vehicle (ROV) were conducted during both phases of the expedition. Recovered gas hydrates occurred either as pore-filling medium associated with discrete turbidite sand layers, or as fracture-filling veins and nodules in muddy sediments. Gas analyses indicated that the methane within the sampled gas hydrates is primarily of biogenic origin. This paper provides a summary of the operational and scientific results of the UBGH2 expedition as described in 24 papers that make up this special issue of the Journal of Marine and Petroleum Geology.

  17. Ultrasonic sound speed of hydrating calcium sulphate hemihydrate; part 2, the correlation of sound velocity to hydration degree

    NARCIS (Netherlands)

    de Korte, A.C.J.; Brouwers, Jos; Fischer, H.B; Matthes, C.; Beuthan, C.

    2011-01-01

    In this article the sound velocity through a mix is correlated to the hydration degree of the mix. Models are presented predicting the sound velocity through fresh slurries and hardened products. These two states correspond to the starting and finishing point of the hydration process. The present

  18. Ultrasonic sound speed of hydrating calcium sulphate hemihydrate; Part 2, The correlation of sound velocity to hydration degree

    NARCIS (Netherlands)

    Korte, de A.C.J.; Brouwers, H.J.H.; Fischer, H.B.; Mattes, Chr.; Beutha, C.

    2011-01-01

    In this article the sound velocity through a mix is correlated to the hydration degree of the mix. Models are presented predicting the sound velocity through fresh slurries and hardened products. These two states correspond to the starting and finishing point of the hydration process. The present

  19. A 2D Micromodel Study of Fines Migration and Clogging Behavior in Porous Media: Implications of Fines on Methane Extraction from Hydrate-Bearing Sediments

    Science.gov (United States)

    Cao, S. C.; Jang, J.; Waite, W. F.; Jafari, M.; Jung, J.

    2017-12-01

    Fine-grained sediment, or "fines," exist nearly ubiquitously in natural sediment, even in the predominantly coarse-grained sediments that host gas hydrates. Fines within these sandy sediments can play a crucial role during gas hydrate production activities. During methane extraction, several processes can alter the mobility and clogging potential of fines: 1) fluid flow as the formation is depressurized to release methane from hydrate; 2) pore-fluid chemistry shifts as pore-fluid brine freshens due to pure water released from dissociating hydrate; 3) the presence of a moving gas/water interface as gas evolves from dissociating hydrate and moves through the reservoir toward the production well. To evaluate fines migration and clogging behavior changes resulting from methane gas production and pore-water freshening during hydrate dissociation, 2D micromodel experiments have been conducted on a selection of pure fines, pore-fluids, and micromodel pore-throat sizes. Additionally, tests have been run with and without an invading gas phase (CO2) to test the significance of a moving meniscus on fines mobility and clogging. The endmember fine particles chosen for this research include silica silt, mica, calcium carbonate, diatoms, kaolinite, illite, and bentonite (primarily made of montmorillonite). The pore fluids include deionized water, sodium chloride brine (2M concentration), and kerosene. The microfluidic pore models, used as porous media analogs, were fabricated with pore-throat widths of 40, 60, and 100 µm. Results from this research show that in addition to the expected dependence of clogging on the ratio of particle-to-pore-throat size, pore-fluid chemistry is also a significant factor because the interaction between a particular type of fine and pore fluid influences that fine's capacity to cluster, clump together and effectively increase its particle "size" relative to the pore-throat width. The presence of a moving gas/fluid meniscus increases the clogging

  20. Vertical seismic profile data from well Mallik 2L-38 for gas hydrate studies

    Energy Technology Data Exchange (ETDEWEB)

    Mi, Y [Calgary Univ., AB (Canada); Walia, R [Victoria Univ., BC (Canada); Hyndman, R D; Sakai, A

    1999-01-01

    A gas hydrate research well was drilled in the Canadian Arctic to determine gas hydrates in a permafrost setting in a collaborative research project between the Japan National Oil Corp., and the Geological Survey of Canada with the participation of other agencies. The multidisciplinary study included an electromagnetic surv