Heterogeneous phase and volumetric behavior of the methane <i>n</i>‐heptane system at low temperatures

Kohn, James P.

doi:10.1002/aic.690070334

Cited by 56 publications

(29 citation statements)

References 13 publications

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“…A quadruple point has been reported by Chang et al [13] and Kohn [14] for the methane-n-heptane system and by Chang and Kobayashi [15] for the methane-toluene system. For such systems, the solubility curve is not continuous from low temperatures up to the solute melting point.…”

Section: Resultsmentioning

confidence: 81%

Solubility of Solid Benzene, Toluene, n-Hexane, and n-Heptane in Liquid Methane

Kuebler¹,

McKinley²

1995

Advances in Cryogenic Engineering

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INTRODUCTIONReliable phase equilibrium data are essential for the design of effective and economical gas treatment processes such as natural gas liquefaction. Data on cryogenic mixtures involving relatively simple molecules are also of theoretical interest. An apparatus and the techniques developed to obtain solid-liquid phase equilibrium data for cryogenic systems are described here. Results are presented for the individual solubilities of solid benzene, toluene, n-hexane, and n-heptane in liquid methane.There are basically two ways to obtain solubility data: the isoplethal method or the isothermal method. The isoplethal method, in which mixtures of known composition are subjected to temperature changes, is not widely used when the solubility is very low. The early work of Stackelberg et al. [1] and the more recent work of Heastie and Lefebvre [2] and Yunker and Halsey [3] are representative of this approach.The use of gas chromatography, which allows the accurate and convenient analysis of vaporized fluid mixtures, has favored increased application of the isothermal or analytical method. Two steps are important in the isothermal method: making the solution and the sampling of this solution for analysis. A usual technique of preparing the solution is to agitate the mixture in the presence of excess solute by mechanical stirring or recirculation of the vapor phase. Jensen and Kurata [4] and Neumann and Mann [5] used the former, while Preston et al. [6] used the recirculation technique. Failure to promote equilibration by agitation can result in systematic errors, as found in the data of Fedorova [']. Solutions can also be formed using a single-pass mode either with solute precipitating from a feed mixture or a previously deposited solute dissolved into a pure solvent feed. Cheung and Zander [8] used the first techni'lue and both techniques have been used in solid-vapor equilibrium measurements ["]. The resultant solution can be flash-evaporated directly to ambient temperature [4.6.8] or the solution can be transferred to a separate chamber and the entire apparatus warmed to ambient temperature [5.'].Discrete samples taken from a bulk solution tend to be poorly reproducible, especially in the parts per million concentration range. Also, the presence of minute quantities of highly soluble contaminants in the solute material can interfere with analysis by gas chromatography. A major advantage of the continuously flowing sample stream is that it attains steady state with respect to adsorption effects in the

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Section: Resultsmentioning

confidence: 81%

Solubility of Solid Benzene, Toluene, n-Hexane, and n-Heptane in Liquid Methane

Kuebler¹,

McKinley²

1995

Advances in Cryogenic Engineering

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“…(6) The three-phase curve {solid heptane (s C7 ) + liquid + vapour} interrupts the three-phase curve l 2 l 1 g at a quadruple point s C7 l 2 l 1 g. (6) Mixtures incorporating an n-alkane with carbon number n e 8 do not show stable (liquid+liquid) equilibria. In these mixtures the three-phase curve (solid high n-alkane+liquid+vapour) (s Cn lg) consists of two branches, as can be seen in figure 1.…”

Section: Introductionmentioning

confidence: 98%

High-pressure phase equilibria of {(1−x)CH4+xCH3(CH2)18CH3}

Kooi

Flöter

Loos

1995

The Journal of Chemical Thermodynamics

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“…At cryogenic temperatures and high pressures, systems such as methane, nheptane (Kohn, 1961) and nitrogen, propane (Schindler et al, 1966) have been reported to show liquid miscibility gaps.…”

Section: Scopementioning

confidence: 97%

Three‐phase equilibria using equations of state

Heidemann

1974

AIChE Journal

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It is demonstrated that a single equation of state may be used to describe all three phases in liquid-liquid-vapor equilibrium situations. Wilson's version of the Redlich-Kwong equation is shown to predict accurately the water solubility in normal paraffins with interaction parameters k12 = 0.50. A simple procedure for three-phase flash computations is presented. Results obtained using this procedure for the system methane, n-butane, water exhibit many of the characteristics of the experimental data of McKetta and Katz (1948). In particular, the water content of the vapor phase and the liquid hydrocarbon phase are accurately predicted. ROBERT A. HEIDEMANN Deportment of Chemical EngineeringUniversity of Calgary Calgary, Alberta T2N 1 N4, Canada SCOPEEquations of state, such as the Benedict-Webb-Rubin equation and the Redlich-Kwong equation, have been increasingly used to describe both phases in vapor-liquid equilibrium computations. In this paper it is shown that it is possible to perform three-phase liquid-liquid-vapor computations using the same equation of state to describe all three phases.Three-phase equilibria occur in the production and processing of natural gas and petroleum wherever significant amounts of water are present. At cryogenic temperatures and high pressures, systems such as methane, nheptane (Kohn, 1961) and nitrogen, propane (Schindler et al., 1966) have been reported to show liquid miscibility gaps.Although this paper is limited to water, normal paraffin examples and only Wilson's version of the Redlich-Kwong equation is considered, the general approach taken is applicable to other equations of state and to other kinds of mixtures. The ability of an equation of state to predict liquid immiscibility and quantitatively correct solubility data provides yet another criterion for evaluation.The computational problems in three-phase equilibria are not trivial. A new algorithm is proposed here for threephase flash calculations. CON C 1 US IONS AN D SIGN I FICA NC EIt has been demonstrated that the liquid phase described by Wilson's version of the Redlich-Kwong equation can be unstable and can separate into two liquid phases of different compositions at equilibrium, depending on the values of the binary interaction parameters. A value of kI2 = 0.50 for normal paraffin, water pairs is found to predict the water solubility in the hydrocarbon liquid with reasonable accuracy. These results open the possibility of using a single equation of state to describe all three phases in liquid-liquid-vapor equilibrium computations.A new computation scheme for multiphase flash problems was presented. This scheme, which is based on free energy minimization, is reliable and easily programmed and may be extended to equilibrium computations with more than three phases present.Using the new computational scheme, it was possible to show that Wilson's version of the Redlich-Kwong equation predicts phase behavior in three-phase systems which exhibit many of the characteristics of experimental systems. In a detailed study o...

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Heterogeneous phase and volumetric behavior of the methane n‐heptane system at low temperatures

Cited by 56 publications

References 13 publications

Solubility of Solid Benzene, Toluene, n-Hexane, and n-Heptane in Liquid Methane

Solubility of Solid Benzene, Toluene, n-Hexane, and n-Heptane in Liquid Methane

High-pressure phase equilibria of {(1−x)CH4+xCH3(CH2)18CH3}

Three‐phase equilibria using equations of state

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