Vapor pressure hydrocarbons

Compilation of physical properties for 321 heavy hydrocarbons. Vapor pressures at low pressures. ... 

Solubility increases with temperature. This increase is, however, smaller than the increase in hydrocarbon vapor pressure. 

Vapor Pressures and Adsorption Isotherms. The key variables affecting the rate of destmction of soHd wastes are temperature, time, and gas—sohd contacting. The effect of temperature on hydrocarbon vaporization rates is readily understood in terms of its effect on Hquid and adsorbed hydrocarbon vapor pressures. For Hquids, the Clausius-Clapeyron equation yields... 

The approximate location of the upper quadruple point Q2 (Lw-H-V-Lhc) is located by the intersection of the Lw-H-V line with the Lw-V-Lhc line. The termination of the three-phase (Lw-V-Lhc) line is the critical point that approximates the two-phase (Vhc-Lhc) critical point of the pure hydrocarbon vapor pressure. As a consequence, the intersection of the pure hydrocarbon vapor pressure with the Lw-H-V line (determined as in Section 4.2) provides the pressure and temperature of the upper quadruple point Q2. 

The three-phase (Lw-V-Lhc) pressure-temperature line is approximated by the vapor pressure (Vhc-Lhc) locus for the pure component due to two effects, both of which are caused by the hydrogen-bond phenomenon described in Chapter 2. First, hydrogen bonds cause almost complete immiscibility between the hydrocarbon liquid and the aqueous liquid, so that the total pressure may be closely approximated by the sum of the vapor pressures of the hydrocarbon phase and that of water. Second, hydrogen bonds cause such a self-attraction of the water molecules that the water vapor pressure is very low, composing only a small fraction of the total vapor pressure at any temperature. Because each immiscible liquid phase essentially exerts its own vapor pressure, and because the water vapor pressure is very small, the hydrocarbon vapor pressure is a very good approximation of the three-phase (Lw-V-Lhc) locus. 

Thermodynamic properties of nonideal hydrocarbon mixtures can be predicted by a single equation of state if it is valid for both the vapor and liquid phases. Although the Benedict-Webb-Rubin (B-W-R) equation of state has received the most attention, numerous attempts have been made to improve the much simpler R-K equation of state so that it will predict liquid-phase properties with an accuracy comparable to that for the vapor phase. The major difficulty with the original R-K equation is its failure to predict vapor pressure accurately, as was exhibited in Fig. 4.3. Following the success of earlier work by Wilson, Soave added a third parameter, the Pitzer acentric factor, to the R-K equation and obtained almost exact agreement with pure hydrocarbon vapor pressure... 

A number of important basicity studies have used distribution techniques to compare aromatic hydrocarbons. Vapor pressure and Henry s law studies (47,236,331) have been reviewed in two recent papers (270,331). McCaulay and Lien (236) also compared basicities of all the methyl benzenes through their solubility in HF-BFa mixtures. 

American Petroleum Institute, Bibliographies on Hydrocarbons, Vols. 1-4, "Vapor-Liquid Equilibrium Data for Hydrocarbon Systems" (1963), "Vapor Pressure Data for Hydrocarbons" (1964), "Volumetric and Thermodynamic Data for Pure Hydrocarbons and Their Mixtures" (1964), "Vapor-Liquid Equilibrium Data for Hydrocarbon-Nonhydrocarbon Gas Systems" (1964), API, Division of Refining, Washington. 

Zwolinski, B. J., and R. C. Wilhoit "Vapor Pressures and Heats of Vaporization of Hydrocarbons and Related Compounds," Thermodynamic Research Center, Dept, of Chemistry, Texas A M University, College Station, Texas, 1971. 

For non-polar components like hydrocarbons, the results are very satisfactory for calculations of vapor pressure, density, enthalpy, and specific, heat and reasonably close for viscosity and conductivity provided that is greater than 0.10. 

The true vapor pressure of hydrocarbons is expressed in bar and represents the vapor pressure directly above a saturated liquid in equilibrium with the vapor that rises over it. 

For pure hydrocarbons and petroleum fractions the vapor pressure can be calculated by three methods which are ... 

When the critical constants for a pure substance or the pseudocritical constants for a petroleum fraction are known, the vapor pressure for hydrocarbons and petroleum fractions can be calculated using the Lee and Kesler equations ... 

This method is based on the expression proposed by Lee and Kesler in 1975. It applies mainly to light hydrocarbons. The average error is around 2% when the calculated vapor pressure is greater than 0.1 bar. 

Maxwell and Bonnel (1955) proposed a method to calculate the vapor pressure of pure hydrocarbons or petroleum fractions whose normal boiling point and specific gravity are known. It is iterative if the boiling point is greater than 366.5 K ... 

Their satisfactory combustion requires no particular characteristics and the specifications are solely concerned with safety considerations (vapor pressure) and the C3 and C4 hydrocarbon distribution. 

Commercial butane comprises mainly C4 hydrocarbons, with propane and propylene content being less than 19 volume %. The density should be equal to or greater than 0.559 kg/1 at 15°C (0.513 kg/1 at 50°C). The maximum vapor pressure should be 6.9 bar at 50°C and the end point less than or equal to 1°C. 

The measurement of the vapor pressure and flash point of crude oils enables the light hydrocarbon content to be estimated. 

Adsorption may occur from the vapor phase rather than from the solution phase. Thus Fig. Ill-16 shows the surface tension lowering when water was exposed for various hydrocarbon vapors is the saturation pressure, that is, the vapor pressure of the pure liquid hydrocarbon. The activity of the hydrocarbon is given by its vapor pressure, and the Gibbs equation takes the form... 

In contrast, the ultrasonic irradiation of organic Hquids has been less studied. SusHck and co-workers estabHshed that virtually all organic Hquids wiU generate free radicals upon ultrasonic irradiation, as long as the total vapor pressure is low enough to allow effective bubble coUapse (49). The sonolysis of simple hydrocarbons (for example, alkanes) creates the same kinds of products associated with very high temperature pyrolysis (50). Most of these products (H2, CH4, and the smaller 1-alkenes) derive from a weU-understood radical chain mechanism. 

Hydroca.rbons. Hydrocarbonsn such as propane, butane, and isobutane, which find use as propellants, are assigned numbers based upon their vapor pressure in psia at 21°C. For example, as shown in Table 2, aerosol-grade propane is known as A-108, / -butane as A-17. Blends of hydrocarbons, eg, A-46, and blends of hydrocarbons and hydrochlorocarbons orHCFCs are also used. The chief problem associated with hydrocarbon propellants is their flammabihty. 

Hydrocarbons have, for the most part, replaced CFCs as propellants. Most personal products such as hair sprays, deodorants, and antiperspirants, as well as household aerosols, are formulated using hydrocarbons or some form of hydro-carbon—halocarbon blend. Blends provide customized vapor pressures and, if halocarbons are utilized, a decrease in flammabiUty. Some blends form azeotropes which have a constant vapor pressure and do not fractionate as the contents of the container are used. 

Phosphoric Acid Fuel Cell. Concentrated phosphoric acid is used for the electrolyte ia PAFC, which operates at 150 to 220°C. At lower temperatures, phosphoric acid is a poor ionic conductor (see Phosphoric acid and the phosphates), and CO poisoning of the Pt electrocatalyst ia the anode becomes more severe when steam-reformed hydrocarbons (qv) are used as the hydrogen-rich fuel. The relative stabiUty of concentrated phosphoric acid is high compared to other common inorganic acids consequentiy, the PAFC is capable of operating at elevated temperatures. In addition, the use of concentrated (- 100%) acid minimizes the water-vapor pressure so water management ia the cell is not difficult. The porous matrix used to retain the acid is usually sihcon carbide SiC, and the electrocatalyst ia both the anode and cathode is mainly Pt. 

Heats of adsorption for hydrocarbons typically range from —20 to —70 kJ/mol (—4.8 to —16.7 kcal/mol ). Equations 1 and 4 both indicate that vapor pressures increase exponentially with increasing temperature. 

Anionic polymerization of vinyl monomers can be effected with a variety of organometaUic compounds alkyllithium compounds are the most useful class (1,33—35). A variety of simple alkyllithium compounds are available commercially. Most simple alkyllithium compounds are soluble in hydrocarbon solvents such as hexane and cyclohexane and they can be prepared by reaction of the corresponding alkyl chlorides with lithium metal. Methyllithium [917-54-4] and phenyllithium [591-51-5] are available in diethyl ether and cyclohexane—ether solutions, respectively, because they are not soluble in hydrocarbon solvents vinyllithium [917-57-7] and allyllithium [3052-45-7] are also insoluble in hydrocarbon solutions and can only be prepared in ether solutions (38,39). Hydrocarbon-soluble alkyllithium initiators are used directiy to initiate polymerization of styrene and diene monomers quantitatively one unique aspect of hthium-based initiators in hydrocarbon solution is that elastomeric polydienes with high 1,4-microstmcture are obtained (1,24,33—37). Certain alkyllithium compounds can be purified by recrystallization (ethyllithium), sublimation (ethyllithium, /-butyUithium [594-19-4] isopropyllithium [2417-93-8] or distillation (j -butyUithium) (40,41). Unfortunately, / -butyUithium is noncrystaUine and too high boiling to be purified by distiUation (38). Since methyllithium and phenyllithium are crystalline soUds which are insoluble in hydrocarbon solution, they can be precipitated into these solutions and then redissolved in appropriate polar solvents (42,43). OrganometaUic compounds of other alkaU metals are insoluble in hydrocarbon solution and possess negligible vapor pressures as expected for salt-like compounds. 

Tetrahydronaphthalene [119-64-2] (Tetralin) is a water-white Hquid that is insoluble in water, slightly soluble in methyl alcohol, and completely soluble in other monohydric alcohols, ethyl ether, and most other organic solvents. It is a powerhil solvent for oils, resins, waxes, mbber, asphalt, and aromatic hydrocarbons, eg, naphthalene and anthracene. Its high flash point and low vapor pressure make it usehil in the manufacture of paints, lacquers, and varnishes for cleaning printing ink from rollers and type in the manufacture of shoe creams and floor waxes as a solvent in the textile industry and for the removal of naphthalene deposits in gas-distribution systems (25). The commercial product typically has a tetrahydronaphthalene content of >97 wt%, with some decahydronaphthalene and naphthalene as the principal impurities. 

Ground turbine fuels are not subject to the constraints of an aircraft operating at reduced pressures of altitude. The temperature of fuel in ground tanks varies over a limited range, eg, 10—30°C, and the vapor pressure is defined by a safety-handling factor such as flash point temperature. Volatile fuels such as naphtha (No. 0-GT) are normally stored in a ground tank equipped with a vapor recovery system to minimise losses and meet local air quaUty codes on hydrocarbons. 

Vapor Pressure. The Shiley Infusaid implantable infusion pump utilizes energy stored in a two-phase fluorinated hydrocarbon fluid. The pump consists of a refillable chamber that holds the dmg and a chamber that holds the fluid. The equiUbrium vapor pressure of the fluid, a constant 60 kPa (450 mm Hg), compresses the bellows, pumping the dmg through a bacterial filter, a capillary flow restrictor, and an infusion cannula to the target body site (56,116). 

Prediction Methods Two methods have gained almost universal acceptance for prediction of the vapor pressure of pure hydrocarbons. 

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