Clathrate hydrates hydrate formation

A rather nnexpected solnbilization phenomenon has also been described, i.e., the pressnre-indnced encapsnlation of low-molecnlar-weight gases in the aqneons micellar core, followed by clathrate hydrate formation [144,145],... 

Classifying particles, in filtration, 11 326 Class I hybrids, 13 536, 543, 544 Class II hybrids, 13 536, 543 Clastogenesis, 25 206 Clathrate hydrates, 14 170—171 Clathrate receptor chemistry, 16 797 Clathrates, 12 374 14 159, 170-182 formation of, 10 633-635 26 869 Hofmann- and Werner-type, 14 171-172 phenol-type, 14 180 tri-o-thymotide, 14 179 Claus catalysts... 

Mochizuki, T. (2003). Clathrate hydrate formation at liquid/liquid interface under shear water flow. J. Crystal Growth, 249, 372-380. 

Ohmura, R. Uchida, T. Takeya, S. Nagao, J. Minagawa, H. Ebinuma, T. Narita, H. (2003 a). Clathrate hydrate formation in (methane + water + methylcyclohexanone) systems the first phase equilibrium data. J. Chem. Thermodynamics, 35, 2045-2054. 

Uchida, T. Ebinuma, T. Kawabata, J. Narita, H. (1999b). Microscopic observations of formation processes of clathrate-hydrate films at an interface between water and carbon dioxide. J. Crystal Growth, 204 (3), 348-356. 

Zeng, H. Wilson, L.D. Walker, V.K. Ripmeester, J.A. (2003). The inhibition of tetrahydrofuran clathrate-hydrate formation with antifreeze protein. Can. J. Phys., 81 (1-2), 17-24. 

A (gas) clathrate hydrate is a crystalline compound which can be obtained by the formation of a hydrogen-bonded host lattice around one or more species of guest molecules. It s a pleasing thought to a crystallographer that when it snows on the outer planets it might snow gas hydrates. (Jeffrey and McMullan, 1967.)... 

Dyadin et al. discover that H2 forms a clathrate hydrate at high pressures up to 1.5 GPa 2004 Camargo et al. and BP/SINTEF introduce cold flow concept to prevent hydrate plug formation without the need of chemical additives... 

Nguyen, H.T., Clathrate Hydrate Formation and Protein Solubilization in Reversed Micelles, Ph.D. Thesis, Tulane University, LA (1991). 

Turner, D., Clathrate Hydrate Formation in Water-in-Oil Dispersions, Golden, Colorado School of Mines, Golden, CO (2005). 

If water will normally form ice in the absence of a solute molecule, the question arises about the mechanism for forming a clathrate with an exact structure, when the solubility of hydrocarbon molecules in liquid water is known to be small (or negligible in ice), relative to the amount of hydrocarbon needed for hydrates. Thus, along with the definition of what the hydrate structures are, comes the logical question of how these structures form. During the past two decades, sophisticated experimental and modeling tools have been applied to address this question. The microscopic mechanism and the macroscopic kinetics of hydrate formation are the major considerations of Chapter 3. 

In a review of the thermodynamics of water, Franks and Reid (1973) showed that the optimum molecular size range for maximum solubility was similar to hydrate stability. Franks and Reid noted, this is not intended to imply that long-lived clathrate structures exist in solution—only that the stabilization of the water structure by the apolar solutes resembles the stabilization of water in a clathrate lattice. Glew (1962) noted that, within experimental error, the heat of solution for ten hydrate formers (including methane, ethane, propane, and hydrogen sulfide) was the same as the heat of hydrate formation from gas and ice, thereby suggesting the coordination of the aqueous solute with surrounding water molecules. 

The number of guest molecules in a locally ordered arrangement exceeds that in the critical nucleus. Guest-guest and host-host cluster order parameters take on values that are very close to the clathrate hydrate phase, which results in formation of a critical nucleus. 

Figure 6.4 (a) ExxonMobil flow loop for hydrate formation, before installing the FBRM instrument, peripheral equipment and housing. (From Turner, D., Clathrate Hydrate Formation in Water-in-Oil Dispersions, Ph.D. Thesis, Colorado School of Mines, Golden, CO 2005. With permission.) (b) Flow wheel apparatus for hydrate formation during flow simulation. (Reproduced from Bakkeng, S.E., Fredriksen, A.E., in Proc. First International Conference on Natural Gas Hydrates, 715, 502 (1994). With permission from the New York Academy of Sciences.)... 

COLOR FIGURE 8.8 Plug formation via aggregation in an oil-dominated system. (From Turner, D.J., Clathrate Hydrate Formation in Water-in-Oil Dispersions, Ph.D. Thesis, Colorado School of Mines, Golden, CO (2004). With permission.)... 

With the growth of the oil and gas industry in the USA, it was realised as early as 1934 that the blocking of gas pipelines at temperatures where normal water would not freeze was being caused by clathrate hydrate formation. The combination of water and hydrocarbons at low temperature, and often increased pressure, are ideal conditions for hydrate formation. Much understanding of this phenomenon has been gained since that time, but as drilling and transportation conditions become more extreme, clathrate hydrate formation continues to be a major problem and is still a very active area of research. 

This is also the optimum size for guests in clathrate hydrates, confirming the close link between methane solutions and methane hydrate discussed by Glew (1962). Indeed the mechanism of solid hydrate clathrate formation may involve the formation of this structure in the aqueous solution (Ewing and Ionescu, 1974).,... 

Nakayama H, Watanabe K (1978) Hydrates of organic compounds. III. The formation of clathrate-like hydrates of tetrabutylammonium dicarboxylates. Bull Chem Soc Jpn 51 2518-2522... 

---