Equilibria of simple natural gas components

The accuracy of hydrate data has seldom been specified by experimentalists. In the following data, only a cursory effort has been made to exclude inaccurate data for simple hydrates. All three-phase data sets for simple hydrates were plotted (as logarithm pressure versus absolute temperature) to determine outliers. 

In general, the data accuracy was surprisingly good. For example, while Deaton and Frost (1946, p. 13) specified that their pure ethane contained 2.1% propane and 0.8% methane, effects of those impurities may have counterbalanced each other those impurities were insufficient to cause the data to fall outside the line formed by other ethane data sets. On the other hand, the simple hydrate data of Hammerschmidt (1934) for propane and isobutane all appear to be outliers on such semilogarithmic plots, because they are at temperatures much too far above the upper quadruple (Q2) point. Obvious outlying data were excluded from this work less obvious outliers may be determined by inspection of the plots and subsequent numerical comparisons. The data, followed by the semilogarithmic plots 

FIGURE 6.18 Raman spectra of the hydrate (Collected by Subramanian.) 

While most of the simple hydrate data consist of the three-phase and quadruple point type, the available two-phase simple hydrate data are listed for methane, ethane, propane, and carbon dioxide. Plots of these data are not suitable for comparison between data sets and are therefore not provided. 

FIGURE 6.19 Raman spectra of carbon dioxide in the liquid, hydrate, and aqueous phase. (Reproduced from Nakano, S., Moritoki, M., Ohgaki, K., J. Chem. Eng. Data, 43, 807 (1998b). With permission from the American Chemical Society.) and hydrogen. (Reproduced from Florusse, L.J., Peters, C.J., Schoonman, J., Hester, K.C., Koh, C.A., Dec, S.F., Marsh, K.N., Sloan, E.D., Science, 306, 469 (2004).) 

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