In two previous papers (Cordeiro et al., 1973a, b ) a methane pressurization process was described by which the solubility of high molecular weight hydrocarbons in a solid phase could be enhanced within a liquid hydrocarbon phase by pressurizing the solid-liquid system with methane gas. This solubility enhancement was demonstrated to occur for two diverse hydrocarbon solids in the following prototype systems : System I: methane (gas) -normal decane (liquid) -normal dotriacontane (solid) System 11: methane (gas) -normal decane (liquid) -phenanthrene (solid) and some speculation was offered concerning the selectivity of aromatic vs. paraffinic solids of similar melting point under methane pressurization with n-decane being the liquid solvent in each case.In this paper, several thermodynamic aspects of the process are considered with respect to the Systems I and I1 and also System 111: methane (gas)-trans decalin (liquid) -normal dotriacontane (solid) the study of which has been recently completed. These experimental results are presented below. EXPERIMENT-SYSTEM IllAn experimental study of the phase equilibria behavior of the ternary system methane-trans decalin-normal dotriacontane was performed. The data was correlated with the Flory-Huggins model (Flory, 1942; Huggins, 1942) solely for the purpose of aiding the later thermodynamic analysis of the system with respect to process behavior. Our previous work (Cordeiro et al. 1973a) presents the equations of this model in detail. The model works as well as with System I, and better than with System 11, using the following partial molar volume and inter- where T is "K. The data are applicable in the range of 323-340°K up to pressures of 70 abn. These data were obtained from the following laboratory experiments, each of which was reproduced at least once.

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In a recent paper (Cordeiro et al., 1972), the authors demonstrated that methane pressurization of solutions of n-decane and n-dotriacontane in equilibrium with a solid phase of n-dotriacontane will enhance the solubility of the high-molecular-weight paraffin n-dotriacontane. The experimental method and data correlation using the FloryHuggins model were presented in detail. The significance of this work lies in its potential application to petroleum recovery, specifically recovery of those high-molecularweight materials left behind after primary and secondary recovery techniques have been employed. Salient features of this methane pressurization process are enhanced solubilities of high-molecular-weight materials due to methane swelling of the liquid phase, increased fluidity of the liquid phase caused by the presence of the methane, and subsequent ease of methane by outgassing.This note reports the effect of methane pressurization on a second prototype ternary three-phase system in which the role of paraffin n-dotriacontane is played by the aromatic phenanthrene. Included is an assessment of the process in terms of its selectivity in solubilizing aromatics versus paraffins in a liquid phase containing n-decane.Thermodynamically speaking, in addition to liquid phase composition, the process derivatives The experimental plan of attack pursued before (Cordeiro et al.) was again followed. For the prototype system with phenanthrene (denoted by subscript 14), the temperature range studied was broader, since the freezing point depression of the phenanthrene was greater due to the addition of n-decane. Furthermore, to expedite the Flory-Huggins correlation for the phenanthrene system, a less suitable candidate for that model, it was found necessary to include composition dependence, by no means insignificant in this case, into vi. We found T / T , as our earlier work with n-dotriacontane. Table 1 maps out methane pressurization of the new system at 369.15"K ( T / T , = 0.9930) while Table 2, via a sample calculation, demonstrates in moles the same isothermal pressurization process.Similarities between the two processes studied (that is, aromatic and paraffinic solid phases) are that (1 > 0 always and (2 is a strong function of T/T,, demonstrating that solids near their melting points are preferentially dissolved.At T / T , = 0.9930, both phenanthrene and n-dotriacontane exhibit a limiting pressure, at which point one can simply dissolve solid with methane indefinitely. This behavior is indicated in Figure 1