Vapor-liquid equilibria gasoline

Chamorro, C. R. Segovia, J. J. Martin, M. C. Villamanan, M. A. Thermodynamics of octane enhancing additives in gasolines vapor-liquid equilibrium of the ternary system di-isopropyl ether (DIPE) + cyclohexane + benzene at 313.15 K Entropie 2000,36(224/225), 86-92... 

Vapor Pressure—Equilibrium pressure exerted by vapors over a liquid at a given temperature [2.1, 2.3]. The Reid vapor pressure (RVP) is typically used to describe the vapor pressure of petroleum fuels without oxygenates at 100°F (ASTM Test Method D 323, Test Method for Vapor Pressure of Petroleum Products) [2.5]. The term true vapor pressure is often used to distinguish between vapor pressure and Reid vapor pressure. The Reid vapor pressure test involves saturating the fuel with water before testing and cannot be used for gasoline-alcohol blends or neat alcohol fuels a new procedure has been developed which does not use water and is called Dry Vapor Pressure Equivalent, or DVPE (see ASTM D 4814-95c under Additional Information section). 

When vaporization occurs in an open container, as when water evaporates from a bowl, the Vapor spreads away from the liquid. Little, if any, is recaptured at the surface of the liquid. Equilibrium never occurs, and the vapor continues to form until the liquid evaporates to dryness. Substances with high vapor pressure (such as gasoline) evaporate more quickly than substances with low vapor pressure (such as motor oh). Liquids that evaporate readily are said to be volatile. 

Henry s law constants for most of the compounds of interest can be found in the literature.54 Figure 18.11 shows Henry s law constants for TCE, EDC and several gasoline compounds.19 These data are derived from water solubility data and the equilibrium vapor pressure of pure liquids at certain temperatures, and may be extrapolated correctly to field design work. Temperature has a major effect on Henry s constant and on stripper performance. Each rise of 10°C in temperature... 

In a natural gasoline fractionation system there are usually six chemical species present in appreciable quantities methane, ethane, propane, isobutane, n-butane, and n-pentane. A mixture of these species is placed in a closed vessel from which all air has been removed. If the temperature and pressure are fixed so that both liquid and vapor phases exist at equilibrium, how many additional phase-rule variables must be chosen to fix the compositions of both phases ... 

When an ideal liquid solution containing two volatile components is in equilibrium with its vapor, the more volatile component will he relatively richer in the vapor. This fact forms the basis of distillation, a technique used to separate (or partially separate) mixtures containing volatile components. Distillation is the procedure by which a moonshiner obtains whiskey using a still and by which petrochemical plants achieve the separation of crude petroleum into gasoline, diesel fuel, lubricating oil, and so forth ( FIGURE 13.22). Distillation is also used routinely on a small scale in the laboratory. 

---