Phase Behavior in the Methane-propane-n-pentane System

Abstract

Abstract The compositions of coexisting phases in the methane-propane-n-pentanesystem were determined at 160? and 220?F. throughout the two-phase region, atpressures above 500 lb. per sq. in. The experimental results permitted thecalculation of gas-liquid equilibrium constants as well as the establishment ofthe critical behavior of this ternary system. Introduction Although many binary paraffin hydrocarbon systems have been investigated, the experimental work relating to the phase behavior of ternary paraffinhydrocarbon mixtures at elevated pressures is relatively scarce, being limitedto a study of the methane-propane-n-pentane system at 100?F. However, Guter andco-workers have studied the phase behavior of the methane-ethane-ethylenesystem at relatively low temperatures. Information concerning the phasebehavior of ternary systems is of value in predicting the behavior of thecomponents in multi component systems, since the influence of pressure, temperature, and concentration may be individually ascertained. In the light ofthe importance of such information, the study of this ternary system wasextended to higher temperatures in order to increase the field of temperaturein which the data could be applied. Since all states encountered in this investigation are above the criticaltemperature of methane, the details of its phase behavior are not of directsignificance. The properties of propane in the heterogeneous region were takenfrom a correlations based upon recently published data. The correspondinginformation for n-pentane was taken from experimentally measured vaporpressures and volumetric data. The methane-propane system has been studiedthroughout the two-phase region at temperatures above 70?F., while the phasebehavior of the propane-n-pentane system has been established for temperaturesabove 16o?F. The volumetric and phase behavior of the methane-n-pentane systemhas been studied in detail. The experimental measurements serve to establishwith adequate accuracy the phase behavior of the components and of theconstituent binary systems for this ternary system. It is believed that, withthe exception of the measurements for the methane-propane system, theuncertainties in the earlier data relating to the pure substances and thebinary mixtures are probably less than those associated with the valuesreported here. T.P. 1490