Critical constants of the naphthenic hydrocarbons

Abstract

Group-contribution values are presented and, together with those already developed for the aliphatic hydrocarbons (10, ZZ), make possibfe the evaluation of both van der Waals' constants for the naphthenic hydrocarbons. These constants can be used to produce the critical temperatures, pressures, and volumes of these compounds entirely from a knowledge of their chemical structure.Critical constants have been calculated for several naphthenes, and from a comparison of them with the constants resulting from the methods of Riedel (5, 6 ) and Lydersen (3) it was found that the critical constants calculated by these three methods were in fair agreement for naphthenes having short alkyl side chains and progressively deviated from each other as the chains were permitted to lengthen. An appraisal has been made on five naphthenes along the lines proposed by Sondak and Thodos (9) in order to see whether these calculated critical constants properly represent the vapor-pressure function resulting from vapor-pressure data found in the literature for these hydrocarbons.Critical constants have been produced for more than 6fty naphthenes, for which vaporpressure data are available in the literature, and w i l l be used in a separate, comprehensive vapor-pressure study for hydrocarbons of this type.

Improved structure–property relationship models for prediction of critical properties

“…Thodos [79,80] developed group increments for the van der Waals parameters "a" and "b" of paraffins. Later, Thodos and co-workers [79][80][81][82] extended the work to other homologous series.…”

Gas-liquid chromatographic study of the thermodynamics of solution in dipropionitriles

“…y = 0.430 -0.886 ( y) -0.694 -0.0375 ( -1)( ) (7) where VQ and Tc are the critical volume and critical temperatures of solutes, respectively. For the cycloheptane system no experimental Tc and Vc values were available, and so the data were computed using van der Waal's constant (40). For oxygenated compounds, like acetone, diethyl ether, and methanol, ß22 data were obtained from interpolation of literature (41,42) data (reported at different temperatures).…”

“…Acetone data also indicate enhanced solute-solvent CARBON No -Figure 3. Incremental relation between excess free energy and molecular structure for n-paraffins in propionitriles, at 40 °C interactions with these propionitriles.…”

Critical Properties of Hydrocarbon Systems

“…13. In a first approach, the gas oil is treated as one average component, and the characterization is based on the measured molecular weight and the measured elemental composition (Sec.…”