Following our previous communications on the impact of the amount of water phase on the time required at each temperature‐step 1 and the limitations of visual techniques in determining hydrate dissociation points, 2 a series of tests were conducted in this laboratory to investigate the impact of measuring techniques, mixing efficiency, heating method and heating rate on the accuracy of hydrate dissociation point measurements. The results showed that nonvisual techniques combined with stepwise heating and satisfactory mixing could save a significant amount of time while providing accurate hydrate dissociation data.

This review includes the current state of the art understanding and advances in technical developments about various fields of gas hydrates, which are combined with expert perspectives and analyses.

Tetrabutyl ammonium bromide (TBAB) forms a semi-clathrate hydrate, which can incorporate small gas molecules such as methane and nitrogen. It has recently been used for separation of gases. However, there are very limited experimental data on the phase boundaries of the gas hydrate form in the presence of TBAB. In this work, we present new experimental data at high-pressure TBAB, w ) 0.10, TBAB (w ) 0.10 and 0.43) + hydrogen, TBAB (w ) 0.05, 0.10, 0.20, and 0.30) + methane, TBAB (w ) 0.10) + nitrogen, TBAB (w ) 0.1 and 0.427) + carbon dioxide, and TBAB (w ) 0.05, 0.10, and 0.43) + natural gas semi-clathrate hydrate phase boundaries. In another part of this work, the results of visual observations of the methane + TBAB semi-clathrate hydrate morphology and the methane gas bubbles released from methane + TBAB semi-clathrate hydrates on dissociation are presented. Finally, the effect of TBAB mass fraction on hydrate promotion and the stability of the new semiclathrate hydrate are presented.

in Wiley InterScience (www.interscience.wiley.com). 2 and CH 4 hydrates. Data for Carbon monoxide occurs in abundance throughout the cosmos, potentially in clathrate form, whereas on Earth, it forms a notable constituent of industrial flue gases. It has been proposed that hydrate technology could be used in CO 2 separation from flue gases, and in subsea flue gas CO 2 disposal. This-and the likely widespread occurrence of CO clathrates in the cosmos-means it is important that the phase behavior of CO hydrates is known. Here, we present experimental H-L-V (hydrate-liquid-vapor) equilibrium data for CO, CO-CO 2 , and CO-C 3 H 8 (propane) clathrate hydrates. Data were generated by a reliable step-heating technique validated using measured data for CO IntroductionGas hydrates, or clathrate hydrates, are a group of nonstoichiometric, icelike crystalline compounds formed through a combination of water and suitably sized "guest " molecules under low-temperature and elevated pressure conditions. In the clathrate lattice, water molecules form hydrogen-bonded cagelike structures, encapsulating the guest molecules, which generally consist of low molecular diameter gases and organic compounds. A concise review of gas hydrates is given by Sloan. 1 Alongside molecular hydrogen and water, carbon monoxide is one of the most abundant molecules in the cosmos. It is found in solid, gaseous, and potentially clathrate hydrate forms throughout the galaxy, either in interstellar gas clouds, or as a component of comets and planetary bodies. [2][3][4] In the terrestrial environment, CO forms a notable constituent of flue and other exhaust gases resulting from the combustion of organic materials.Recently, hydrate technology has been proposed as a means for CO 2 separation from industrial flue gases. 5 Carbon monoxide is a common component of such gases, and thus its effects on hydrate equilibria should be considered in process design. Similarly, any CO present in CO 2 destined for proposed hydrate sequestration schemes 6,7 will also influence the phase behavior. These factors, and the potential widespread abundance of CO clathrates in the cosmos, warrant an improved understanding of CO clathrate hydrate equilibria.Currently, only very limited data are available in the literature concerning CO hydrates. Carbon monoxide is similar in molecular size to oxygen and nitrogen. Given that both O 2 and N 2 can form simple (single guest) gas hydrates, it was proposed in the 1960s that carbon monoxide should also form clathrates. 2,8,9 In the absence of experimental data, Miller 3 and 4 however, using the classical Lennard-Jones-Devonshire (LJD) cell model (with cell parameters apparently modified from those of nitrogen hydrates), concluded that structure I would be the more stable structure for carbon monoxide, giving a dissociation pressure around 20% lower than that for structure II at the same temperature. Davidson et al. 10 subsequently resolved this issue through low-temperature X-ray powder diffraction studies, which demonstrated that ...

We present experimental structure-I clathrate hydrate (methane, carbon dioxide, and methane-carbon dioxide) equilibrium and ice-melting data for mesoporous silica glass. In both cases, high capillary pressures result in depressed solid decomposition temperatures (clathrate dissociation and ice melting), as a function of pore diameter. Clathrate dissociation data show a significant improvement over existing literature data, which is attributed to the improved experimental techniques and interpretative methods used. Through application of a melting (or clathrate dissociation) modified Gibbs-Thomson relationship to experimental data, we determine similar values of 32 ( 2, 32 ( 3, and 30 ( 3 mJ/m 2 for ice-water, methane clathrate-water, and carbon dioxide clathrate-water interfacial tensions, respectively. The data are important for the accurate thermodynamic modeling of clathrate systems, particularly with respect to subsea sedimentary environments, and should prove useful in the simulation of potential methane hydrate exploitation and carbon dioxide sequestration schemes.

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