Pure critical data

This database provides thermophysical property data (phase equilibrium data, critical data, transport properties, surface tensions, electrolyte data) for about 21 000 pure compounds and 101 000 mixtures. DETHERM, with its 4.2 million data sets, is produced by Dechema, FIZ Chcmic (Berlin, Germany) and DDBST GmhH (Oldenburg. Germany). Definitions of the more than SOO properties available in the database can be found in NUMERIGUIDE (sec Section 5.18). 

To obtain an analytic function / in Eq. (55), Chueh uses the Redlich-Kwong equation however, since the application is intended for liquids, the two constants in that equation were not evaluated (as is usually done) from critical data alone, but rather from a fit of the pure-component saturated-liquid volumes. The constants a and b in the equation of Redlich and Kwong are calculated from the relations... 

This introduces two "interaction parameters" per binary pair. The pure component coefficients, a and b i, are evaluated from critical data and the acentricity, as proposed by Soave in his original paper (1). The pure component aii varies with reduced temperature so as to match vapor pressure. (Soave s recently revised expression for a (17) has not been used.)... 

The equation-of-state method, on the other hand, uses typically three parameters p, T andft/for each pure component and one binary interactioncparameter k,, which can often be taken as constant over a relatively wide temperature range. It represents the pure-component vapour pressure curve over a wider temperature range, includes the critical data p and T, and besides predicting the phase equilibrium also describes volume, enthalpy and entropy, thus enabling the heat of mixing, Joule-Thompson effect, adiabatic compressibility in the two-phase region etc. to be calculated. 

Simmrock, K. H., R. Janowsky and A. Ohnsorge, CRITICAL DATA OF PURE SUBSTANCES. Vol. II, Parts 1 and 2, Dechema Chemistry Data Series, 6000 Frankfurt/Main, Germany (1986). 

Kistiakowsky-Fishtine equation puys chem An equation to calculate latent heats of vaporization of pure compounds useful when vapor pressure and critical data are not available., kis-te-a k6f-ske fa shtTn i,kwa-zhan kitol oRG CHEM C40H60O2 One of the provitamins of vitamin A derived from whale liver oil crystallizes from methanol solution. ke,tol ... 

But even if the water at its critical temperature consisted of nearly pure dihydrol, without any trihydrol molecules, it would still be far more highly associated than calculation from Guye s formula would indicate. As shown on p. 300, when the most recent critical data are employed in the calculation, the molecular weight of water at the critical temperature works out at 18-5, and corresponds to almost absolutely pure mbnohydrol. 

If the constants a and 6 are not known it is possible to estimate their values from critical data. It can be shown (see for example Daniels, Outlines of Physical Chemistry) that a = 3P<,F and b -YJZ where Pg and F<, are the critical pressure and critical volume, respectively. The critical pressure is the pressure required to liquefy a pure gas at the critical temperature and the critical volume is the volume of one mole at the critical pressure and temperature. The meaning of these critical quantities will be described more fully in a later chapter. 

Listed here for various chemical species are values for the molar mass (molecular weight), acentric factor >, critical temperature Tc, critical pressure Pc, critical compressibilityfactor Z., critical molar volume Vc, and normal boilingpoint T . Abstracted from Project 801, DIPPR , Design Institute for Physical Property Data of the American Institute of Chemical Engineers, they are reproduced with permission. The full data compilation is published by T. E. Daubert, R. P. Daimer, H. M. Sibul, and C. C. Stebbins, Physical and Thermodynamic Properties of Pure Chemicals Data Compilation, Taylor Francis, Bristol, PA, 1,405 chemicals, extant 1995. Included are values for 26 physical constants and regressed values of parameters in equations for the temperature dependence of 13 theniiodynamicand transport properties. 

The SRK EOS parameters of the pure components can be calculated in terms of their critical pressure and temperature [29]. The binary interaction parameter q can be found from phase equilibria data for the binary mixture. Because, such data are not available, the critical loci data for the systems CO2 (1) + methanol (2) and CO2 (1) + acetone (2) [30] were used to calculate qn (Reference [30]), provided the binary critical data in the form X2 — Pa — Ta, where X2 is the molar fraction of component 2 in the critical mixture. Per the critical pressure and Per the critical temperature of the mixture. The mixture parameter a (a ) in the SRK EOS was calculated for every X2 — P — Per point using the expression [29]... 

In order to maximize the value of the applied thermodynamics system throughout the enterprise, it must be accessible to all process engineers and chemists who require accurate thermophysical property calculations in their daily work. Web applications, which do not require installation of the calculation engine on the user s computer, facilitate ea.sy access to the system. Web applications can be designed to provide pure component data such as normal boiling point and critical properties. They can also provide access to the most frequently carried out calculations, such as phase equilibrium calculations, tabulation, and plotting of pure component properties as a function of temperature and pressure, and mixture property calculations. 

A classical example is the hydrogenation of CO2 in the presence of secondary amines to yield formamides (eq. (7)). The formation of carbamates from the amine and CO2 leads to the presence of a liquid phase that cannot be dissolved in CO2 even at temperatures and pressures way beyond the critical data of pure CO2. Nevertheless, the reaction occurs with extraordinarily high turnover numbers and reaction rates [17, 34], even with catalysts that have no solubility in SCCO2 [35,72]. Most likely, the reaction occurs in the liquid phase, but the supercritical CO2 phase ensures rapid mass transfer of the reactants (CO2, H2) and the product (DMF) between the two phases. It has been shown recently that the addition of ionic liquids (vide infra) can help to control the distribution of reactants, intermediates, and products between the two reaction phases. Additional control over the chemoselectivity of the transformation is thus possible by judicious segregation of various components of the reaction mixture [36, 74]. 

SiMMROCK, K. H., et al, Critical Data of Pure Substances, 2 parts, Dechema, Frankfurt, West Germany, 1986. 

Ambrose, D., Vapor-liquid Critical Properties, N. P. L. Teddington, Middlesex, Rep. 107, 1980 Kudchaker, A. P, G. H. Alani, and B. J. Zwolinski, Chem. Revs. 68 659-735, 1968 Matthews, J. E, Chem. Revs. 72 71-100, 1972 Simmrock, K., R. Janowsky, and A. Ohnsorge, Critical Data of Pure Substances, Parts 1 and 2, Dechema Chemistry Data Series, 1986 Other recent references for critical data can be found in Lide, D. R., CRC Handbook of Chemistry and Physics, 86th ed., CRC Press, Boca Raton, Fla., 2005. 

The major problem of the direct carbonatation of alcohols is of course the formation of water and the unfavorable thermodynamics of the process. Attempts to overcome this problem include the addition of water-trapping agents or start from alcohol derivatives such as ortho esters. A number of such experiments have been carried out under conditions considerably beyond the critical data of pure CO2 [88]. The presence of the supercritical phase as a solvent was explicitly addressed in the synthesis of glycerol carbonate from glycerol and CO2 [89]. The tin-catalyzed conversion of trimethyl ortho ester to dimethyl carbonate in SCCO2 occurred with up to ca. 30 catalytic turnovers, whereby the highest yields and selectivities were observed in the vicinity of the critical pressure of pure CO2 [90]. 

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