Methane + n-butane

Use the Peng-Robinson equation of state to calculate the compositions and densities of the equilibrium liquid and gas of the mixture given below at 160°F and 2000 psia. Use binary interaction coefficients of 0.02 for methane-n-butane, 0.035 for methane-n-decane, and 0.0 for n-butane-n-decane. 

The phase equilibria data for binary guest mixtures are listed under the lighter component. For example, under the heading of binary guest mixtures of methane will be found data for methane + ethane, methane + propane, methane + isobutane, methane + n-butane, methane + nitrogen, methane + carbon dioxide, and methane + hydrogen sulfide. Concentrations are in mole percent or mole fraction in the gas phase, unless otherwise indicated. 

Hydrate Methane + n-butane Reference McLeod and Campbell (1961) Phases Lw-H-V... 

Figure 6.32 Methane + n-butane mixture (Lw-H-Lw qhio) data.

Figure 11 a) Transient permeation behaviour of a binary methan n-butane (50/50)... 

In particular the layers prepared by two subsequent hydrothermal treatments showed an optimal quality. Flux and separation factors of single gas, methane, n-butane, isobutane and 2,2-dimethylbutane as well as mixtures of methane/n-butane, n-butane/isobutane and n-hexane/2,2- dimethylbutane were determined. 

Calculations were carried out for the solubilities of mixtures of hydrocarbons (methane—ethane and methane—n-butane) and for the mixture methane—carbon dioxide in water, because experimental data regarding the solubilities of binary gas mixtures and individual gases are available for these mixtures. ... 

Table 2. Comparison between Predicted and Experimental Solubilities of Methane n-Butane Mixtures in Water at T = 344.25 K ...

The results of the present calculations are compared with experiment in Table 2 and Figures 1 and 2, where y2 is the mole fraction of methane in the gas phase. One can see that there is good agreement between the two. The deviations at P = 20 MPa for the methane—n-butane gas mixture are possibly caused by the experimental uncertainties regarding the solubility of the pure re-butane in water. ... 

Methane, n-butane, isobutane, and cyclohexane have strong C—H bonds (I>c—h > 390 kJ mol and high oxidation potentials (IP > 9.8 ev), and vigorous conditions are required to oxidize these hydrocarbons with inorganic oxidants. On the other hand, toluene and o-, m-, and p-xylenes have weaker C—H bonds ( >c h 355 kJ mol ) and lower ionization potentials (IP < 8.8 eV), and can be oxidized more readily. 

The chain-of-rotators eos often predicts vie information for ternary systems except near the critical point a good example is the mixture of methane, n-butane, and decane. 

Reamer, Sage, and Lacey [Ind. Eng. Chem., 43,1436 (1951)] measured the following equilibrium phase compositions for the methane/n-butane/n-decane system at 2 F and 3000 psia. 

At 190°F and 600 psia, a methane/n-butane vapor mixture of 0.6037 mole fraction methane is in equilibrium with a liquid mixture containing 0.1304 mole fraction methane. Using physical property constants and correlation coefficients from Appendix I,... 

The bulk phase diagrams of pure hydrocarbons and mixtures are well known from the experiments. In the work by Sage et al. [3], the bubble point pressures of methane + n-butane mixtures are determined experimentally from the discontinuity of isothermal compressibility of constant-composition mixture at the point of phase transition. The composition of vapor phase is determined in that work from the residual specific volume of gas. Later experiments employ phase recirculation techniques [4] to achieve vapor-Uquid equilibrium [5, 6], and the phase compositions are analyzed by more advanced methods such as gas chromatography. 

Fig. 1 Component density profiles in vapor-liquid coexistence simulations for methane + n-butane mixture at 330 K 40 atm (a) and 90 atm (b)...

Fig. 2 Phase equilibrium curve of methane + n-butane at 330 K MD model compared to the experimental data [3]. The error bars show statistical uncertainties. The error bars lie within the symbols if not shown...

The phase diagram of the test methane + n-butane system is calculated. 

Sage, B.H., Hicks, B.L., Lacey, W.N. Phase equilibria in hydrocarbon systems. The methane-n-butane system in the two-phase region. Ind. Eng. Chem. 32, 1085 (1940)... 

Elliott, D.G., Chen, R.J.J., Chappelear, P.S., Kobayashi, R. Vapor-liquid equilibrium of methane-n-butane system at low temperatures and high pressures. J. Chem. Eng. Data 19, 71-77 (1974)... 

Type 1 mixtures have continuous gas-liquid critical line and exhibit complete miscibility of the hquids at all temperatures. Mixtures of substances with comparable critical properties or substances belonging to a homologous series form Type 1 unless the size difference between components is large. The critical locus could be convex upward with a maximum or concave down with a minimmn. Examples of Type 1 mixtures are Water + 1-propanol, methane + n-butane, benzene + toluene, and carbon dioxide + n-butane. 

Rutherford, W.M. Calculation of Thermal Diffusion Factors for the Methane-n-Butane System in the Critical and Liquid Regions." AIChE J vol. 9, p. 841,1963,... 

The three phase program was then evaluated by comparing predicted and experimental results for the methane-n-butane-water and n-butane-1 butene-water systems as reported by McKetta and Katz (,9) and Wehe and McKetta (1 ). 

Figures 8 and 9 illustrate the type of agreement that was obtained for the water content and the hydrocarbon distribution in both the hydrocarbon liquid and vapor phases for the methane n-butane-water system. It can be seen from Figure 8 that the predictions reproduce the water content very well at all temperatures. Figure 9 shows that the agreement between experimental and predicted hydrocarbon concentrations in the vapor and liquid phases is good at 100 F, although the agreements does not seem to be as good at 2220 F. The experimental data for 220 F may be open to question since the critical pressure for methane-n-butane mixtures at 220 F is reported to be about 1350 psia by Roberts et al (11). The experimental data of these authors on the methane-n-butane system at 220 F are Included for comparison. It seems doubtful that the presence of water in this system would increase the critical pressure to about 1550 psia as indicated by the three component data. In view of this, the predicted results are thought to be just as good at 220 F as at 100°F.

Table 4 compares our prediction with thermal conductivity data of a nitrogen-ethane mixture from Gilmore and Comings (16). Values from the unmodified equation are given in parentheses. Finally, Table 5 shows the results for a methane-n-butane mixture (17). 

FIG. 8 Dependence of the surface tension on the distance to the phase envelope. The mixture of methane-n-butane at 277.6 K. (From Ref. 25.)... 

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