Methane, propane, and n-pentane

Point 1 represents a mixture of methane, propane, and n-pentane which exhibits equilibrium gas and liquid at the temperature and pressure indicated by the diagram. Point 2 represents the composition of the equilibrium gas, and point 3 represents the composition of the equilibrium liquid. The quantity of gas, in fraction of total moles of overall mixture, is represented by the length of line 13 divided by the length of line 23. The quantity of liquid in terms of fraction of total moles of overall mixture is represented by the length of line 12 divided by the length of line 23. ... 

Fig. 2-27. Ternary phase diagram of mixtures of methane, propane, and n-pentane at 1500 psia and 160°F. (Data from Dourson et al., Trans. AIME, 151, 206.)...

Figure 2-27 gives the saturation envelope for mixtures of methane, propane, and n-pentane at the same temperature as Figure 2-26 but at a higher pressure. The bubble-point and dew-point lines join at a critical point. The critical point gives the composition of the mixture, which has a critical pressure of 1500 psia and a critical temperature of 160°F. 

Figure 2—28 shows the various positions the saturation envelopes of mixtures of methane, propane, and n-pentane can take at 160°F as pressure is increased from atmospheric to 2350 psia. Reference to the binary mixtures shown in Figure 2-29 will assist in understanding the reasons for the changes in the shapes of the saturation envelopes as pressure is increased. The numbered dots on Figure 2-29 correspond to the numbered diagrams of Figure 2-28. 

Fig. 2-29. Vapor pressures of methane, propane, and n-pentane with critical loci of binary mixtures. (The numbered points correspond to the diagram numbers on Figure 2-28.)...

As pressure is increased, the size of the two-phase region decreases, Figure 2-28(7), until the critical pressure of a methane-n-pentane mixture is reached, 2350 psia at this temperature, dot 8. At this pressure and at all higher pressures, all mixtures of methane, propane, and n-pentane are single-phase. 

At atmospheric pressure, all mixtures of these components will be gas. See Figure 2-28(1). The temperature is well above the critical temperature of methane, and atmospheric pressure is well below the vapor pressures of propane and n-pentane at 160°F. 

Other types of non-micro-channel, non-micro-flow micro reactors were used for catalyst development and testing [51, 52]. A computer-based micro-reactor system was described for investigating heterogeneously catalyzed gas-phase reactions [52]. The micro reactor is a Pyrex glass tube of 8 mm inner diameter and can be operated up to 500 °C and 1 bar. The reactor inner volume is 5-10 ml, the loop cycle is 0.9 ml, and the pump volume adds a further 9 ml. The reactor was used for isomerization of neopentane and n-pentane and the hydrogenolysis of isobutane, n-butane, propane, ethane, and methane at Pt with a catalyst. 

At pressures above the vapor pressure of propane and less than the critical locus of mixtures of methane and n-pentane, for instance 500 psia, dot 4, the methane-propane and methane-n-pentane binaries exhibit two-phase behavior, and propane-n-pentane mixtures are all liquid. Thus the saturation envelope appears as in Figure 2-28 (4). 

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 ... 

Okabe and Becker examined the photolysis of -butane at 1470 and 1236 A, with and without NO as an inhibitor. Their thorough product analysis, which gave an excellent material balance, showed that the products for the uninhibited reaction are hydrogen, methane, acetylene, ethylene, ethane, propene, propane, butene-1, cis- and tranf-butene-2, iso- and n-pentane, hexanes and small amounts of iso-butane and allene. The most important reactions occurring in the photolysis are... 

The above equation was used to obtain values, at regular intervals of Tr from Tr = 0.5 to Tr = 1, for liquid methane, ethane, propane, n-butane, and n-pentane. The calculated values are compared with some of the available tabulations in the literature (17,18,20) in Figures 1 through 5. Excellent agreement was obtained. 

Isothermal Enthalpy Departures. The isothermal enthalpy departures from the ideal-gas state were calculated for six pure, saturated liquids (methane, ethane, propane, n-butane, i-butane, and n-pentane) using Equation 39. The proposed equation was, of course, used in its derivation... 

Figure 3. RK interaction parameters for the hydrocarbon-hydrocarbon systems ( ), methane-heavier hydrocarbon ( ), ethane-heavier hydrocarbon ( ), propane-heavier hydrocarbon (A), n-butane-heav-ier hydrocarbon and ( ), n-pentane-heavier hydrocarbon.

Figure 1 Experimental shock tube ignition delay time measurements (symbols) and model predictions for methane, propane, n-butane and n-pentane. Also shown are computed predictions for iso-butane.

A method is discussed below for the determination of the composition of an ethylene-butene-1 copolymer containing up to about 10% butene. This technique has been applied to the pyrolysis gas chromatography of ethylene-butene copolymers. Pyrolysis were carried out at 410°C in an evacuated gas vial and the products swept into the gas chromatograph. Under these pyrolysis conditions, it is possible to analyse the pyrolysis gas components and obtain data within a range of about 10% relative. The peaks observed on the chromatogram were methane, ethylene, ethane, combined propylene and propane, isobutane, 1-butene, trans-2-butene, cis-2-butene, 2-methyl-butane and n-pentane. 

The dilated van Laar model is readily generalized to the multicomponent case, as discussed in detail elsewhere (C3, C4). The important technical advantage of the generalization is that it permits good estimates to be made of multicomponent phase behavior using only experimental data obtained for binary systems. For example, Fig. 14 presents a comparison of calculated and observed -factors for the methane-propane-n-pentane system at conditions close to the critical.7... 

A material balance was observed that is consistent with the proposed mechanism within the limits of experimental error. The methane/propane ratio increases from 0.06 at 1 54 torr to 0.11 at 0.54 torr. Considerable uncertainty (approx. 50%) must be attached to these ratios, but the trend is consistent with the higher yield of methane observed by Thrush91 at pressure below 0.1 torr. Fischer and Mains92 question the occurrence of reaction (6) as they could not detect any n-pentane in their reaction products. At the high ethyl radical concentrations obtained in flash photolysis this product would certainly be expected, if a significant concentration of thermal ethyl radicals were present. However, Thrush was unable to detect ethyl radicals spectroscopically under his experimental conditions. Therefore all reactions of ethyl in his system must involve C2H and the extent to which... 

The interaction parameters for binary systems containing water with methane, ethane, propane, n-butane, n-pentane, n-hexane, n-octane, and benzene have been determined using data from the literature. The phase behavior of the paraffin - water systems can be represented very well using the modified procedure. However, the aromatic - water system can not be correlated satisfactorily. Possibly a differetn type of mixing rule will be required for the aromatic - water systems, although this has not as yet been explored. 

Fig. 5. Rate of H—D exchange versus ionization potential of alkanes and aromatic compounds 1 = methane 2 = ethane 3 = propane 4 = n-butane 5 = n-pentane 6 = n-hexane 7 = cyclopentane 8 = cyclohexane 9 = benzene 10 = naphthalene 11 = phenanthrene 12 = 2,2-dimethylbutane (see text) 13 = 1,1-dimethylpropy I benzene (see text) 14 = 2-methylpropane 15 = 2-methylbutane 16 = 2,2-dimethylpropane 17 = 2-methylpentane 18 = 3-methylpentane 19 = 2,3-dimethylbutane 20 = 2,2-dimethylbutane.

EXAMPLE 2-8 Determine the compositions and quantities of equilibrium gas and liquid when 6 lb moles of a mixture of 50 mole percent methane, 15 mole percent propane, and 35 mole percent n-pentane are brought to equilibrium at 16(FF and 500 psia. 

Consider a pressure above the vapor pressure of n-pentane and below vapor pressure of propane, for instance, 200 psia. See dot 2 on Figure 2-29 and Figure 2-28(2). All mixtures of methane and propane are gas. Both the methane-n-pentane binary and the propane-n-pentane binary are in their two-phase regions. Their bubble-point and dew-point compositions appear along the sides of the ternary diagram as the ends of the bubble-point and dew-point lines of the ternary mixtures. 

Above this pressure, dot 6, all mixtures of methane and propane are single phase. Thus only the methane-n-pentane binaries have two-phase behavior, and only the methane-n-pentane side of the ternary diagram can show a bubble point and a dew point. The bubble-point and dewpoint lines of the saturation envelope do not intercept another side of the diagram, rather the two lines join at a critical point, i.e., the composition of the three-component mixture that has a critical pressure of 1500 psia at 160°F. 

A liquid of 80 mole percent propane and 20 mole percent n-pentane is to be diluted with methane. Will all mixtures of the liquid and methane be single phase at 160°F and 1500 psia Explain the reason for your answer. 

Dourson, R.H., Sage, B.H., and Lacey, W.N. Phase Behavior in the Methane-propane-n-pentane System, Trans., AIME (1942) 151, 206-215. 

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