Correlation of Interfacial Tension of Hydrocarbons

Correlation of interfacial tension of the methane-n-pentane and methane-n-decane systems was made by Hough and Stegemeier by the use of the Weinaug and Katz equation. The methane-n-heptane and ethylene-n-heptane systems were investigated by the authors. Additional systems taken from the literature were the methane-propane system by Weinaug and Katz, the methane-n-butane system by Pennington and Hough, and the n-butane-carbon dioxide system by Brauer and Hough. These systems were analyzed by the Weinaug-Katz equation and the Sugden equation on the IBM 1620 II computer using a regression analysis program. Parachor and exponent values for each component and system were determined. The experimental work was close to the critical point of the light component in the n-butane-carbon dioxide and ethylene-n-heptane systems, between the critical points of the light and heavy components in the methane-n-pentane, methane-n-heptane and methane-n-decane systems, and close to the critical point of the heavy component in the methane-propane and methane-n-butane systems. An empirical formula was developed to find a value of the constant B in the Sugden equation for binary hydrocarbon systems from the parachor values of the two components. interfacial tension for binary hydrocarbon Systems was found to be a direct function of liquid-vapor phase density difference in the same manner as a single-component system. Discussion Interfacial tension may be defined as the measure of the specific free surface energy between two phases having different compositions. The interfacial tension (IFT) for a binary system may be predicted for any temperature and pressure if the mole fractions and molal volumes of the liquid and gaseous phases are known. One method of correlating IFT was proposed by Weinaug and Katz and modified by Hough and Stegemeier. The modified formula is: (1) where y = interfacial tension, dynes/cmP1 = parachor of the first componentP2 = parachor of the second componentx1, x2 = mole fractions in the liquid phasey1, y2 = mole fractions in the vapor phaseVL, Vv = molal volumes (cu ft/lb mole)1/62.43 = conversion factor, lb/cu ft to gm/ccK = exponent of the parachor relation and subscriptsL = liquidV = vapor1 = component 12 = component 2. In a binary system, there are two degrees of freedom; that is, the values of x1, x2 y1, y2, VL and Vv are determined at any particular temperature and pressure. Therefore, for each temperature and pressure at which an experimental value of IFT was measured, the values of x1, y1, VL and Vv were found, and the following values were calculated: (2) (3) SPEJ P. 345ˆ