Vapor-liquid equilibrium measurement

For binary vapor-liquid equilibrium measurements, the parameters sought are those that minimize the objective function... 

Figure 1. Schematic flow apparatus used for NH3-H20 (and electrolyte) vapor-liquid equilibrium measurements...

TABLE 1. Ammonia-Mater Vapor-Liquid Equilibrium Measurements at 80 C by Flow Cell Method... 

Wilding, W.V., Adams, K.L., Carmichael, A.E., Hull, J.B., Jarman, T.C., Jenkins, K.P., Marshall, T.L., and Wilson, H.L. Vapor-liquid equilibrium measurements on three binary mixtures difluoromethane/hydrogen chloride, c/s-1,3-dichloropropene/frans-dichloropropene, and pyrrole/water, /. Chem. Eng. Data, 47(4) 748-756, 2002. 

Tang, I. N., H. R. Munkelwitz, and J. H. Lee, Vapor-Liquid Equilibrium Measurements for Dilute Nitric Acid Solutions, Atmos. Environ., 22, 2579-2585 (1988). 

Apparatus. All vapor-liquid equilibrium measurements were made by using a modified Othmer still provided with an external electric heater. Total volume of the still was about 500 cm3, of which about 300 cm3 was occupied by liquid. The liquid loaded in the condensate receiver was about 7 cm3. Details of the still are described in a previous paper (5). 

Measurements of binary vapor-liquid equilibria can be expressed in terms of activity coefficients, and then correlated by the Wilson or other suitable equation. Data on all possible pairs of components can be combined to represent the vapor-liquid behavior of the complete mixture. For exploratory purposes, several rapid experimental techniques are applicable. For example, differential ebulliometry can obtain data for several systems in one laboratory day, from which infinite dilution activity coefficients can be calculated and then used to evaluate the parameters of correlating equations. Chromatography also is a well-developed rapid technique for vapor-liquid equilibrium measurement of extractive distillation systems. The low-boiling solvent is deposited on an inert carrier to serve as the adsorbent. The mathematics is known from which the relative volatility of a pair of substances can be calculated from the effluent trace of the elutriated stream. Some of the literature of these two techniques is cited by Walas (1985, pp. 216-217). 

C, vapor-liquid equilibrium, measured range 35.0-60.0°C, Scatchard Raymond 1938)... 

Bobbo, S., Camporese, R., Stryjek, R. (2000a) (Vapor + liquid) equilibrium measurement and correlation of the refrigerant (propane +... 

Bobbo, S., Stryjek, R., Elvassore, N., Bertucco, A. (1998) A recirculation apparatus for vapor-liquid equilibrium measurements of refrigerants. Binary mixtures ofR600a, R134a andR236fa. Fluid Phase Equilibria 150-151, 343-352. 

There is a considerable amount of experimentaldata for properties of mixtures wherein toluene is a principal constituent. Compilations and bibliographies exist for vapor—liquid equilibrium measurements (9,10), liquid—liquid equilibrium measurements (11), and azeotropic data (12,13). 

Select the criterion to be used for thermodynamic consistency. Deviations from thermodynamic consistency arise as a result of experimental errors. Impurities in the samples used for vapor-liquid equilibrium measurements are often the source of error. A complete set of vapor-liquid equilibrium data includes temperature T. pressure P. liquid composition x, and vapor composition y,. Usual practice is to convert these data into activity coefficients by the following equation, which is a rearranged form of the equation that rigorously defines K values (i.e., defines the ratio y, /x, under Related Calculations in Example 3.1) ... 

In Kaw = 8.701 -5760/(T/K), temp range 20-100°C (vapor-liquid equilibrium measurements with additional literature data, Dohnal Fenclovd 1995)... 

Compilations of infinite-dilution activity coefficients, when available for the solute of interest, may be used to rank candidate solvents. Partition ratios at finite concentrations can be estimated from these data by extrapolation from infinite dilution using a suitable correlation equation such as NRTL [Eq. (15-25)]. Examples of these lands of calculations are given by Walas [Phase EquU ria in Chemical Engineering (Butterworth-Heinemann, 1985)]. Most activity coefficients available in the literature are for small organic molecules and are derived from vapor-liquid equilibrium measurements or azeotropic composition data. 

Wilsak, R.A. Campbell, S.W. Thodos, G. Vapor-liquid equilibrium measurements for the n-pentane-methanol system at 372.7, 397.7, and 422.6 K. Fluid Phase Equilib. 1987, 33, 157-171. 

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