International Conference on Gas Hydrates (ICGH) (6th : 2008)

EFFECT OF CLATHRATE STRUCTURE AND PROMOTER ON THE PHASE BEHAVIOUR OF HYDROGEN CLATHRATES Chapoy, Antonin; Anderson, Ross; Tohidi, Bahman Jul 31, 2008

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
59278-5320_1.pdf [ 333.23kB ]
Metadata
JSON: 59278-1.0041095.json
JSON-LD: 59278-1.0041095-ld.json
RDF/XML (Pretty): 59278-1.0041095-rdf.xml
RDF/JSON: 59278-1.0041095-rdf.json
Turtle: 59278-1.0041095-turtle.txt
N-Triples: 59278-1.0041095-rdf-ntriples.txt
Original Record: 59278-1.0041095-source.json
Full Text
59278-1.0041095-fulltext.txt
Citation
59278-1.0041095.ris

Full Text

Proceedings of the 6th International Conference on Gas Hydrates (ICGH 2008), Vancouver, British Columbia, CANADA, July 6-10, 2008.  EFFECT OF CLATHRATE STRUCTURE AND PROMOTER ON THE PHASE BEHAVIOUR OF HYDROGEN CLATHRATES Antonin Chapoy, Ross Anderson, Bahman Tohidi ∗ Centre for Gas Hydrate Research, Institute of Petroleum Engineering Heriot-Watt University, Edinburgh,EH14 4AS UNITED KINGDOM  ABSTRACT Hydrogen is currently considered by many as the “fuel of the future”. It is particularly favoured as a replacement for fossil fuels due to its clean-burning properties; the waste product of combustion being water. While hydrogen is relatively easy to produce, there is currently a lack of practical storage methods for molecular H2, and this is greatly hindering the use of hydrogen as a fuel. Gases are normally stored in vessels under only moderate pressures and in liquid form where possible, which yields the highest energy density. However, to store reasonable quantities of hydrogen in similar volume containers, cryogenic temperatures or extreme pressure are required. Many potential hydrogen storage technologies are currently under investigation, including adsorption on metal hydrides, nanotubes and glass microspheres, and the chemical breakdown of compounds containing hydrogen to release H2. Recent studies have sparked interest in hydrates as a potential hydrogen storage material. The molecular storage of hydrogen in clathrate hydrates could offer significant benefits with regard to ease of formation/regeneration, cost and safety, as compared to other storage materials currently under investigation. Here, we present new experimental hydrate stability data for sII forming hydrogen–water (up to pressures of 180 MPa) and hydrogen–water–tetrahydrofuran systems, the structure-H forming hydrogen–water– methyclycohexane system, and semi-clathrate forming hydrogen–water–tetra-n-butyl ammonium bromide/tetra–n-butyl ammonium fluoride systems. Keywords: gas hydrates, hydrogen, tetrahydrofuran, methylcyclohexane, ammonium bromide, tetra-n-butyl ammonium fluoride, experimental data NOMENCLATURE P Pressure [MPa] T Temperature [K] H Hydrate I Ice I1 Ice I I3 Ice III I4 Ice IV I5 Ice V L Liquid MCH Methylcyclohexane Q1 Quadruple point (I+V+L+H) sI Structure-I sII Structure-II sH Structure-H ∗  TBAB TBAF THF V  tetra-n-butyl  Tetra-n-butyl ammonium bromide Tetra-n-butyl ammonium fluoride Tetrahydrofuran Vapour  INTRODUCTION It is now widely accepted that anthropogenic CO2 emissions from the burning of fossil fuels are largely responsible for the rapid rise in global temperatures recorded over the past century. Worldwide concerns over the threat of global warming have provoked industrialised countries into working to reduce carbon emissions, with specific targets being laid out in the 1997 Kyoto Protocol agreement. To meet these goals, nations  Corresponding author: Phone: +44(0)1314 513 672 Fax +44(0)1314 513 127 E-mail: Bahman.Tohidi@pet.hw.ac.uk  must increase investment in ‘clean’, renewable sources of energy, and develop solutions for reducing CO2 (and other greenhouse gases) emissions from existing and new fossil fuel usage. There are a variety of renewable, carbon-free options for energy generation, including hydroelectric, wind, solar, and wave power. Hydroelectric and wind technology (e.g. wind farms) are well developed and commercially viable, but expansion can be hampered by the availability of suitable sites and local environmental/ecological concerns. Solar and wave power require further development before they become competitive, and face similar location/logistical problems. Nuclear is currently a favoured option for many governments, and is billed as ‘clean’ due to negligible carbon emissions. However, public concerns over safety present a considerable stumbling block to development; these in part being fuelled by the lack of a concrete consensus on long term radioactive waste disposal solutions. A further major problem with nuclear power, and probably the biggest hurdle to immediate expansion, is the high cost and long construction time of nuclear power plants. Hydrogen is currently considered by many as the ‘fuel of the future’. It is particularly favoured as a replacement for fossil fuels due to its cleanburning properties; the waste product of combustion being water. Many processes can be used to produce hydrogen (e.g. steam reforming of natural gas, catalytic decomposition of natural gas, partial oxidation of heavy oil, coal gasification, steam-iron coal gasification, water electrolysis, thermo-chemical, photochemical, photoelectrochemical and photo-biological processes). While hydrogen is relatively easy to produce, there is currently a lack of practical storage methods for molecular H2, and this is greatly hindering the use of hydrogen as a fuel. Gases are normally stored in vessels under only moderate pressures (for safety), and in liquid form where possible (e.g. propane, butane), which yields the highest energy density. However, to store reasonable quantities of hydrogen in similar volume containers, cryogenic temperatures (liquid H2 T<20 K) or extreme pressures (100’s of MPa) are required. As a result, the widespread use of hydrogen as a fuel, particularly for non-stationary applications (e.g. powering motor vehicles), is currently restricted.  Many potential hydrogen storage technologies are currently under investigation, including adsorption on metal hydrides, nanotubes and glass microspheres, and the chemical breakdown of compounds containing hydrogen to release H2. Hydrogen storage in carbon structures and metal hydrides are currently the leading areas of research. While these are promising technologies, both still have considerable limitations (Sandí, 2004 [1]). Metal hydrides provide a potential safe, stable storage media, yet incur a large weight penalty and require very high temperatures (> 200 °C) to trap/release hydrogen. Absorption of H2 in carbon microstructures requires much less extreme conditions, however consistent and commercially viable H2 contents have yet to be achieved. Recent studies have sparked interest in gas (or clathrate) hydrates as potential hydrogen storage materials [2-3]. When compressed into the cages of a clathrate hydrate, the distance between gas molecules can approach that of the liquid state, making for very high compression ratios. For example, 1 m3 of sI methane hydrate can hold up to 175 m3 of gas at standard conditions. This has led to considerable research into gas hydrates as a potential means for the storage and transportation of gases. However, for common sI and sII hydrates, either high pressures (10’s of MPa) or low temperatures (subzero) are needed for stability, which introduces significant technical and operational costs. There have been various attempts to increase hydrate stability to lower pressures by employing hydrate ‘promoters’ (e.g., THF, propane). However, these ‘promoters’ occupy most of the large cavities, reducing the storage capacity. Until recently (and for the largely forgotten study of Villard, 1887 [4]), hydrogen was considered not to form gas hydrates due to its molecular diameter being too small to stabilise cavities. However, Mao et al. (2002) [2] demonstrated that pure hydrogen can form sII clathrate hydrates at very high pressures and low temperatures, sparking interest in hydrates as a potential hydrogen storage material. Florusse et al. (2004) [5] have subsequently shown that the pressure required to stabilise hydrogen in clathrates can be greatly reduced by adding a second guest ‘promoter’, namely tetrahydrofuran/THF (~5 MPa at 7 °C). The molecular storage of hydrogen in clathrate hydrates could offer significant benefits with regard to ease of formation/regeneration, cost and  safety, as compared to other current storage materials currently under investigation. However, it is now widely accepted that common clathrate structures (sI, sII, sH) cannot achieve H2 storage goals. This leaves the option of investigating alternative new clathrate structures and their potential uses for H2 storage and/or separation.  bromide (50 wt%) in water and tetra-n-butyl ammonium fluoride (75 wt%) in water were purchased from Sigma-Aldrich. Deionised water was used to dilute tetra-n-butyl ammonium bromide, dilute tetra-n-butyl ammonium fluoride and tetrahydrofuran to the different desired aqueous mass fractions used in experiments.  Here, we present new experimental hydrate stability data for sII forming hydrogen–water (up to pressures of 180 MPa) and hydrogen–water– tetrahydrofuran systems, the structure-H forming hydrogen–water–methyclycohexane system, and semi-clathrate forming hydrogen–water–tetra-nbutyl ammonium bromide/tetra–n-butyl ammonium fluoride systems.  Ultra-High Pressure Apparatus The ‘ultra-high pressure’ hydrate set-up was used for tests up to 200 MPa. It comprises of a 45ml cell constructed of AISI 660 steel, which is compatible with many oilfield chemicals, including aqueous solutions containing salts and/or organic hydrate inhibitors. A schematic of the setup is shown in Figure 2, which is pressure tested to 200 MPa. Cell temperature is monitored with a PRT (Platinum Resistance Thermometer) with the sensing part in contact with test fluids. Cell pressure is measured using a Quartzdyne pressure transducer accurate to 0.05 MPa. System temperature is controlled by circulating coolant from a cryostat through a jacket surrounding the cell. Mixing is achieved by rocking the cell through 180° using a compressed air-driven mechanism. To aid mixing, steel ball-bearings are placed inside the cell.  EXPERIMENTAL Clathrate dissociation and/or ice melting PT conditions were determined by standard constant volume cell isochoric equilibrium step-heating techniques. This method, which is based upon the direct detection (from pressure) of bulk density changes occurring during phase transitions, produces very reliable, repeatable phase equilibrium measurements. [6]. Two set-ups were used; one for pressures up to 40 MPa and a second for pressures up to 200 MPa.  WATER JACKET  Pressure  No hydrate Hydrate dissociation and gas release  Dissociation Point  CONSTANT TEM PERATURE BATH  HIGH PRESSURE CELL PRESSURE TRANSDUCER  PRT  Hydrate dissociation + Thermal expansion Thermal expansion  Temperature  Figure 1 Dissociation point determination from equilibrium step-heating data. The equilibrium dissociation point is determined as being the intersection between the hydrate dissociation (gas release related pressure rise with increasing temperature) and the linear thermal expansion (no hydrate) curves Materials Hydrogen was purchased from BOC gases with a certified purity greater than 99.995 vol. %. THF, from Prolabo, had a certified purity of 99.975 % min. Methylcyclohexane from Sigma-Aldrich had a certified purity 99.5%. Tetra-n-butyl ammonium  Figure 2 Schematic of ultra high pressure rig High Pressure Apparatus Figure 3 shows the apparatus used to determine phase equilibrium conditions at pressures lower than 40 MPa. The set-up comprises of a 500 ml stainless steel cylindrical autoclave cell. Temperature control (0.1 K) is again provided by a circulating coolant/jacket system. A PRT determines cell temperature, while pressure is measured by means of a strain gauge transducer. To achieve rapid thermodynamic equilibrium through good mixing of the fluids, a magnetic  motor driven stirrer was used for agitation of fluids. PC interface Magnetic motor  PRT Coolant Jacket Pressure Transducer Stirrer blade Inlet / oulet  Figure 3 Schematic of high pressure rig Experimental Procedures For the H2-H2O and H2-MCH-H2O systems, the ultra high pressure rig (200 MPa) was used. For all other systems, the high pressure autoclave set-up (40 MPa) was used. A typical test to determine the hydrate dissociation point of a system was as follows: The equilibrium cell was first cleaned and vacuumed, then charged with the desired components. For the H2-THF-H2O, H2-TBABH2O and H2-TBAF-H2O systems, the aqueous liquid solutions were first prepared to the desired concentration (19 mass%, 43 mass% and 35 mass%, respectively), loaded into the cell, then hydrogen injected directly from a high pressure cylinder to achieve the desired starting pressure.  wise (usually 0.5ºC intervals), allowing enough time at each temperature step for equilibrium to be reached (sometimes in excess of 24h for the H2H2O system). At temperatures below the point of complete dissociation, gas is released from decomposing hydrates, giving a marked rise in the cell pressure with each temperature step (Figure 1). However, once the cell temperature has passed the final hydrate dissociation point, and all clathrates have disappeared from the system, a further rise in the temperature will result only in a relatively small pressure rise due to thermal expansion. This process results in two traces with very different slopes on a pressure versus temperature (P/T) plot; one before and one after the dissociation point. The point where these two traces intersect (i.e., an abrupt change in the slope of the P/T plot) is taken as the dissociation point (see Figure 1). Following measurement of a single dissociation point, cell pressure was increased by injection of water (for the H2-H2O and H2-MCH-H2O systems) or hydrogen to reach the next desired condition, before the cycle was repeated to determine a further point on the phase boundary for the system. RESULTS AND DISCUSSION Experimental clathrate hydrate dissociations were obtained for the binary system H2-H2O and for the ternary systems H2-MCH-H2O, H2-THF-H2O, H2TBAB-H2O and H2-TBAF-H2O. Measured equilibrium hydrate dissociation conditions are reported in Tables 1 5, and plotted in Figure 4. 1000  For all systems, the cell temperature was set to a point well outside the expected hydrate stability zone for the system under study during loading. Temperature was then lowered to form hydrates; growth being detected by an associated drop in cell pressure (as gas becomes trapped in hydrate structures). Cell temperature was then raised step-  I5  I4 I3  P / MPa  For the H2-H2O system, half of the volume of the cell was initially preloaded with water, then hydrogen injected to achieve a pressure of 70 MPa. To attain higher pressures, water was subsequently injected using a high pressure hand pump. For H2-MCH-H2O tests, procedures were similar; water injection to pre-loaded systems being used increase pressures beyond 70 MPa.  sII: H2  sH: H2-MCH sII:H2-THF  100  10 I1  1 250  260  270  H2-TBAB  280  T/K  290  H2-TBAF  300  310  Figure 4 Effect of clathrate structure and promoter on the phase behaviour of hydrogen clathrates. This work: ¡:H2; S:H2-MCH;‘: H2-THF; U: H2-TBAB; □: H2-TBAB. ½: H2, data from Vos et al. [7] c: H2, data from Dyadin et al. [8] z: D2, data from Lokshin and Zhao [9](D2-D2O system); z: H2-THF data from Florusse et al. [5].  the ice I curve intersect is taken as the quadruple point (Figure 6).  300  P / MPa  250  I3  sII: H2 sH: H2-MCH  200 I1  150 100 50 0 250  260  270  280  290  T/K  Figure 5 Experimental clathrate hydrate dissociation for the binary system H2-H2O (¡: this work; c: H2, data from Dyadin et al. [8] z: H2, data from Lokshin and Zhao [9]) and for the ternary system H2-MCH-H2O (‘: this work). H2-H2O binary system For the binary system H2-H2O, there is an obvious scattered in the clathrate hydrate dissociation point reported from different authors, deviations sometimes being in excess of 3 K (Figure 5). Dyadin et al. [8] stated that in some experiments, equilibrium states were not actually achieved, whereas Lokshin and Zhao [9] studied the D2-D2O system. In Figure 6, a typical dissociation point measurement is shown, hydrate dissociation is characterised by essentially congruent decomposition on the phase boundary. 140  Ice Melting Point  P / MPa  130 120 110  Dissociation Point  Q1  100 90 80 255  Start Point  Ice Formation  I1  260  265  T/K  270  275  Figure 6 Typical clathrate hydrate dissociation point measurement for the binary system H2-H2O (c: equilibrium points; ¡: estimated Q1) . Experimental clathrate hydrate dissociation points: z: this work; U: H2, data from Dyadin et al. [8] ‘: H2, data from Lokshin and Zhao [9]. The quadruple point, Q1 − where ice, vapour, liquid and hydrate coexist for this system (I+V+L+H) − has been estimated. The point where the best fitted curve to our experimental data and  Texp / K (±0.1) 269.15 268.15 267.15 266.45 265.25 264.45 Q1†:263.85  Pexp / MPa (±0.05) 178.41 160.76 146.80 134.97 120.75 111.38 105.00  Table 1. Experimental clathrate hydrate dissociation (H+L+V > L+V) for the binary system H2-H2O (†Estimated) The cage occupancy for this system has also been the subject of some debate. Mao et al. [2] were the first to report that hydrogen could form simple cubic structure-II clathrate hydrates at high pressures (200 MPa at 280 K) and/or cryogenic temperatures (145 K). Authors estimated a clathrate stochiometry of H2.2H2O based on double H2 occupancy of all sixteen small pentagonal dodecahedral (512) cavities, and quadruple occupancy of larger hexakaidecahedral (51264) cavities, giving a maximum hydrogen storage capacity of 5 mass%. Subsequently, in 2004, Lovskin et al. [3] demonstrated that the hexakaidecahedral cage can hold up to four hydrogen molecules (2 to 4 depending on T and P), but the small pentagonal dodecahedral cage can hold only one hydrogen molecule, leading to a maximum hydrogen capacity of 3.77 mass%. H2-MCH-H2O ternary system By adding a second guest − the well-known structure-H former methylcyclohexane − it is possible to stabilize hydrogen in a clathrate structure at significantly lower pressures than those for pure structure-II hydrogen clathrate hydrates (Figure 5). Measured experimental equilibrium hydrate dissociation conditions for this system are reported in Table 2. The structure-H unit crystal is made up of three small dodecahedron cages (512), two medium irregular dodecahedron cages (435663), and one large icosahedral cage (51268), in total requiring 34 water molecules. A theoretical H2 storage capacity can be estimated for this system assuming single occupancy of the small and medium cages by  hydrogen, and full occupancy of the large cage by MCH. The maximum hydrogen capacity for this guest configuration would be 1.38 mass%. Texp / K (±0.1) 279.55 278.55 277.15 275.95 274.95 273.95  Pexp / MPa (±0.05) 149.66 135.17 117.08 102.62 94.48 83.72  Table 2. Experimental clathrate hydrate dissociation (H+L+LHC+V > L+ LHC +V) for the ternary system H2-MCH-H2O H2-THF-H2O ternary system Experimental clathrate hydrate dissociation for the ternary system H2-THF-H2O has been measured with a stoichiometric THF to water ratio of 1:17 (Table 3). The hydrogen content of binary H2-THF hydrates has been the subject of some controversy. Lee et al. [10] claimed that the hydrogen content of sII H2-THF clathrates could be greatly increased (up to ~4 mass% H2) at modest pressures (12 MPa) by “tuning” THF contents. Based on Raman, MAS NMR and volumetric measurements, authors argued that clathrate dodecahedral cavities could accommodate two H2 molecules, and, at initial aqueous THF concentrations below the atmospheric eutectic composition (~1.0 mole%), in the hydrate-ice-vapour region (H+I+V) region, clusters of four hydrogen molecules could replace THF in large hexakaidecahedral cavities, whereby greatly increasing H2 content. However the most recent detailed study of H2−THF clathrate hydrogen contents directly contradicts the findings of these authors; Strobel et al. [11], using volumetric measurements in conjunction with Raman and MAS NMR data, concluded that small cavities can only accommodate single H2 molecules, and that, irrespective of initial aqueous THF concentration and/or formation conditions, large cavities are always fully occupied by THF. A maximum hydrogen content of around 1 mass% was reported. Similarly, Anderson et al. [12] tried to replicate the work of Lee et al., and confirmed the findings of Strobel et al. [11], i.e. that no evidence for H2 entering and stabilising the large sII cavity under tested conditions was found.  These conclusions were also supported by the more recent work of Talyzin [13]. To date, the results of Lee et al. [10] have not been independently replicated. Texp / K (±0.1) 281.20 282.80 286.00 288.20  Pexp / MPa (±0.05) 8.69 14.46 28.15 38.58  Table 3. Experimental clathrate hydrate dissociation (H+L+V > L+V) for the ternary system H2-THF-H2O (w=19 wt%) Semi-clathrate hydrates Semi-clathrate hydrates share many of the physical and structural properties of classical clathrate hydrates (sI, II and H). Both hydrate classes comprise of a hydrogen-bonded water latticework based primarily around the pentagonal dodecahedra (512) unit of structure. Structural variety arises from the way dodecahedra associate; face sharing or bonding between vertices adjusting to create a variety of interstitial multifaceted polyhedra for accommodation of (guest) gas molecules or ion pairs without significantly disrupting the hydrogen-bonding scheme of the water framework [14]. The principal difference between the two classes is that, in true clathrate hydrates, guest molecules are not physically bonded to the water lattice, rather they are stabilised within and lend stability to cavities through van der Waals interactions. In contrast, in semi-clathrates, guest molecules can both physically bond with the water structure and occupy cavities; for the quaternary (or peralkyl) ammonium salt semi-clathrates, the QAS hydrophobic cation takes a cage filling role, whilst the negatively charged anion is hydrogen bonded with water latticework [14,15]. Although semiclathrates are primarily composed of water (often >95 mole% H2O), this configuration lends great thermal stability to structure, giving some semiclathrates melting temperatures in excess of 303.15 K at atmospheric pressure.  Texp / K (±0.1) 286.05 286.25 287.10 287.90 288.00  Pexp / MPa (±0.05) 3.60 5.23 12.41 21.29 23.07  Table 4. Experimental semi-clathrate hydrate dissociation (H+L+ V > L +V) for the ternary system H2-TBAB-H2O (w=43 mass%) In this work, semi-clathrate hydrate phase equilibria were determined experimentally for H2TBAB-H2O and H2-TBAF-H2O systems under hydrogen pressures up to 25 MPa over the temperature range 286 to 303 K (Tables 4 and 5). Figure 4 shows that binary H2-QAS semi-clathrate hydrates demonstrate greatly increased thermal and low pressure stability when compared with H2 and binary H2-THF clathrate hydrates. However, assuming full occupancy of the small-sized cage by hydrogen, the theoretical storage capacity is only 0.6 wt%. Texp / K (±0.1) 301.73 302.40  Pexp / MPa (±0.05) 4.81 10.13  Table 5. Experimental semi-clathrate hydrate dissociation (H+L+ V > L +V) for the ternary system H2-TBAF-H2O (w=35 mass%) CONCLUSIONS We have presented new experimental hydrate stability data for sII forming hydrogen–water (up to pressures of 180 MPa) and hydrogen–water– tetrahydrofuran systems, the structure-H forming hydrogen–water–methyclycohexane system, and semi-clathrate forming hydrogen–water–tetra-nbutyl ammonium bromide/tetra–n-butyl ammonium fluoride systems. This data provides better delineation of hydrogen stability fields, for which there is notable scatter for some systems (notably the H2-H2O). The theoretical hydrogen storage potential of these structures has also been assessed, and it is concluded that data to date indicate that the more favourable the thermodynamic stability of binary H2-promoter clathrate is, the lower the hydrogen content.  Acknowledgments The authors thank Colin Flockhart, Thomas McGravie, and Jim Allison for manufacture and maintenance of experimental equipment. This work is part of a project supported by the UK Engineering and Physical Science Research Council (EPSRC Grant EP/E04803X/1), which is gratefully acknowledged. REFERENCES [1] Sandí G. Hydrogen Storage and its limitation. Electrochem. Soc. Interface 2004;13:40-45. [2] Mao WL, Mao HK, Goncharov AF, Struzhkin VV, Guo QZ, Hu JZ, Shu JF, Hemley RJ, Somayazulu M, Zhao YS. Hydrogen clusters in clathrate hydrate, Science 2002; 297: 22472249. [3] Lokshin KA, Zhao YS, He DW, Mao WL, Mao HK, Hemley RJ, Lobanov MV, Greenblatt M. Structure and dynamics of hydrogen molecules in the novel clathrate hydrate by high pressure neutron diffraction. Phys. Rev. Lett. 2004;93(12): Art. No. 125503. [4] Villard MP. Etude expérimentale des hydrates de gaz. Annales de chimie et de physique 1897 ; 11(7):289-394. [5] Florusse LJ, Peters CJ, Schoonman J, Hester KC, Koh C, Dec SF, Marsh KN, Sloan ED. Stable Low-Pressure Hydrogen Clusters Stored in a Binary Clathrate Hydrate. Science 2004;306(5695):469-471. [6] Tohidi B, Burgass RW, Danesh A, Todd AC, Østergaard KK. Improving the Accuracy of Gas Hydrate Dissociation Point Measurements. Ann. N.Y. Acad. Sci. 2000;912:924-931. [7] Vos, W.L. Finger LW, Hemley RJ, Mao HK. Novel H2-H2O clathrates at high pressures. Physical Review Letters 1993;71(19):31503153. [8] Dyadin YA. Larionov EG, Manakov AY, Zhurko FV, Aladko EY, Mikina TV, Komarov VY. Clathrate hydrates of hydrogen and neon Mendeleev Communications 1999;5:209-210. [9] Lokshin KA, Zhao YS. Fast synthesis method and phase diagram of hydrogen clathrate hydrate. Applied Physics Letters 2005;88(13): Art. No. 131909. [10] Lee H, Lee JW, Kim DY, Park J, Seo YT, Zeng H, Moudrakovski IL, Ratcliffe CI, Ripmeester JA. Tuning clathrate hydrates for hydrogen storage. Nature 2005; 434(7034): 743-746.  [11] Strobel TA, Taylor CJ, Hester KC, Dec SF, Koh CA, Miller KT, Sloan ED. Molecular hydrogen storage in binary THF-H2 clathrate hydrates. J. Phys. Chem. B. 2006;110(34): 17121-17125. [12] Anderson R, Chapoy A, Tohidi B. Phase Relations and Binary Clathrate Hydrate Formation in the system H2-THF-H2O. Langmuir 2007;23(6):3440-3444. [13] Talyzin A. Feasibility of H2–THF–H2O clathrate hydrates for hydrogen storage applications. Int. J. of Hydrogen Energy 2007 in press. [14] Jeffrey G.A. Hydrate Inclusion Compounds. In: Inclusion Compounds 1. Atwood, JL, Davies JED, MacNichol DD, editors, Academic Press: London, 1983, p 135. [15] Davidson DW. Clathrate Hydrates. In: Water: A Comprehensive Treatise. Vol. 2, Franks F, editor. Plenum Press: New York, London, 1973. p. 115.  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.59278.1-0041095/manifest

Comment

Related Items