Antoine parameters

Extensive tabulations of Antoine parameters are available for many chemicals of importance to engineers, chemists, and environmental scientists (9,19,20). Caution is in order when using tabulated Antoine constants because several forms of the correlating equation are found in the Hterature. In particular, there are variations in the sign before the second term, the units of temperature, and the use of natural or decimal logarithms of the vapor pressure. 

At present there are two fundamentally different approaches available for calculating phase equilibria, one utilising activity coefficients and the other an equation of state. In the case of vapour-liquid equilibrium (VLE), the first method is an extension of Raoult s Law. For binary systems it requires typically three Antoine parameters for each component and two parameters for the activity coefficients to describe the pure-component vapour pressure and the phase equilibrium. Further parameters are needed to represent the temperature dependence of the activity coefficients, therebly allowing the heat of mixing to be calculated. 

Estimate the van Laar parameters of methanol (1) and 1,2-dichloro-ethane (2) from equilibria data obtained at T = 323.15 and shown in Table 3.9 if the Antoine parameters for these components are (ref. 52) Aj = 23.8843,... 

Dreisbach, R. R., 1955, Physical Properties of Chemical Compounds, Vols. 1,2, and 3 (Advances in Chemistry Scries, Nos. 5, 22 and 29). American Chemical Society, Washington, D.C. Antoine parameters are given for organic compounds in these books frequently Ihcsc have been taken from other compilations. 

Useful correlations exist among the Antoine parameters (or at least relationships among them) and molecular structure. 

The Antoine parameters were determined on the basis of two experimental points. 

The Antoine parameters in the temperature range 233 to 264 K were calculated based original experimental data [63-quinow] and Cox-Othmer diagram. Partial decomposition of the compound is reported at temperatures above 400 K. 

There are two sources of original experimental data for this compound which are in good agreement with each other (the difference over the temperature interval is about 1.5%). We have presented three different sets of the Antoine parameters (one for each data set reported and one for the combination of all the data). 

Figure 6.16 shows a comparison between calculated and experimental data, with Antoine parameters from the database, and Maximum Likelihood objective function. The accuracy is sufficient for technical computations, but it could be better when Antoine parameters are simultaneously regressed. 

Antoine parameters of selected organic compounds 397 Properties of water 399... 

Three moles of benzene, four moles of acetonitrile, and four moles of water are placed in a closed vessel and brought into VLLE at 333 K, 0.70 bar. Assume the liquid phases obey the NRTL equations (Appendix J), with parameter values given in Table J.l. Appendix D contains Antoine parameters for vapor pressures of the pure-components. Use the double Rachford-Rice algorithm of Figure 11.6 to determine the following ... 

Vapor pressures of most pure fluids can be adequately correlated by the Antoine equation (8.2.31). The following table provides values of the Antoine parameters for a few fluids. These apply for the vapor pressure P in bar and temperature T in Kelvin [1]. 

The numerical values of the Antoine parameters depend on the working units of and T, which can vary from source to source. It is important to establish, by checking with the source of the data, what are the proper units of pressure and temperature to be used with a given set of parameters. Also important is to establish whether the... 

Alternatively, the saturation temperature at 20 bar is calculated to be 483 K = 210 °C, less than the temperature of the system. From this again we conclude that the phase is superheated vapor. However, at 483 K, temperature is outside the range of the Antoine parameters therefore, this result should not be considered reliable. 

For water the Antoine-parameters occurring in this equation are tabulated as follows in mbar and T in °C) ... 

VLE data, the results of two thermodynamic consistency tests, and the parameters of different -models, such as the Wilson, NRTL, and UNIQUAC equation. Additionally, the parameters of the Margules [28] and van Laar [29] equation are listed. Furthermore, the calculated results for the different models are given. For the model which shows the lowest mean deviation in vapor phase mole fraction the results are additionally shown in graphical form together with the experimental data and the calculated activity coefficients at infinite dilution. In the appendix of the data compilation the reader will find the additionally required pure component data, such as the molar volumes for the Wilson equation, the relative van der Waals properties for the UNIQUAC equation, and the parameters of the dimerization constants for carboxylic acids. Usually, the Antoine parameter A is adjusted to A to start from the vapor pressure data given by the authors, and to use the -model parameters only to describe the deviation from Raoult s law. Since in this data compilation only VLE data up to 5000 mm Hg are presented, ideal vapor phase behavior is assumed when fitting the parameters. For systems with carboxylic acids the association model is used to describe the deviation from ideal vapor phase behavior. 

P8.14 The vapor pressures of liquid anthracene and phenanthrene can be described by the Antoine equation using the Antoine parameters given below. Calculate the vapor-liquid-solid equilibrium (VLSE) along the solid-liquid saturation curve assuming ideal mixture behavior in the liquid phase. Melting points and heats of fusion of both components are given in example P8.1 above. Compare the vapor-liquid separation factors to those of an isothermal VLE data set at 220 "C (calculate assuming ideal liquid mixture behavior). 

Here the subscript o means that the derivative is taken along the saturation line, where the liquid is in equilibrium with the vapor. On the contrary, if the Antoine parameters are known, the molar heat of vaporization can be estimated from ... 

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