Specific retention volumes and limiting activity coefficients of C4-C8 alkane solutes in C22-C36 n-alkane solvents

Abstract

The specific retention volumes of 21 hydrocarbon solutes are measured on eight liquid phases at 80", loo", and 120°C. The infinite dilution activity 7oefficients and heats of solution are presented and compared with literature data.The basic physical process responsible for retention of a solute in gas-liquid partition chromatography is the partition of a solute or solutes between the gas and liquid phases. Because of this fact, much of the thermodynamic information attainable from a normal (static) solubility or vapor-pressure measurement is also obtainable from gas chromatographic retention volume measurements. In particular, numerous authors (7-4, 6, 8 , 77, 74-79, 25, 26, 28, 3 7 , 38, 3 9 ) have measured infinite dilution activity coefficients and/or other thermodynamic data such as heat of solution, entropy of solution, and partial molar excess enthalpies and entropies.Hydrocarbon systems have been studied extensively by this method. The activity coefficients of C4-Ca hydrocarbon solutes in n-hexadecane, n-heptadecane, and n-octadecane have been measured at lower temperatures (5, 73, 33, 4 7 ) . The normal hydrocarbons in the range c2O-c36 at higher temperatures ( >6O0C) have been studied by several investigators ( 2 0 , 32, 42, 4 5 ) ; however, the studies have been limited in scope, and there is little overlap of the data sets. Hicks and Young ( 2 0 ) studied n-butane, n-pentane, and n-hexane on n-tetracosane and n-octacosane; however, each measurement was at a separate temperature so that little correlation of this data is possible because of the temperature dependence of the activity coefficients in low-molecular-weight solvents at low temperatures. For higher molecular-weight systems at higher temperatures, the activity coefficient is generally independent of temperature, because of low values for the partial molar excess enthalpy of these systems. However, at lower temperatures the activity coefficients generally decrease with increasing temperatures; therefore, it is not advisable to compare data sets at different temperatures for low-molecular-weight systems.Martire and Pollara ( 3 2 ) , Young ( 4 5 ) , and Tewari et al. ( 4 2 ) all reported activity coefficient data for one or more solvents in the range 8O-12O0C, and this literature data will be compared with the results of this report in the Discussion section.Pease and Thorburn ( 3 7 ) have published V, data for 27 alkane solutes on n-octacosane, n-dotriacontane, and n-hexatriacontane at 8O.Oo, 100.0", and 120.0"C. This set of Vg data was used as a reference point for our Vg values, and the comparison will be given in the Discussion section.In many cases, the activity coefficients and heats of solution have been compared with data obtained from static isotherm, vapor pressure, or solubility data. The general conclusions ( 7 2 , 40, 4 3 ) are that the accuracy of the limiting activity coefficients and heats of solution are ' To whom correspondence should be addressed compatible with static data, and that the chromatographic approach offers sev...

Activity coefficients in nearly athermal model polymer/solvent systems

“…This does not agree with the experimental findings. Several experimental studies (see Elbro et al, 1990;Parcher et al, 1975) have shown that the infinite-dilution activity coefficients of alkanes in hydrocarbon mixtures increase with temperature over a sufficiently broad temperature range. This, in fact, means that p should be both temperature and chain length dependent.…”

Analysis of zero‐reference‐pressure EoS/GE models

“…This is shown in Figure 4 for n-hexane (l)/n-hexadecane (2) at 293.15 K and 0.1 bar (Vcl/Vcz = 2.5). Note that the differences in G E cannot be attributed to the difference between the pressure value (0.1 bar) used to generate the results in Experimental data from Parcher et al (1975). This is demonstrated in Figures 5 and 6, where infinite dilution activity coefficients of n-butane in n-alkanes and n-alkanes in n-hexane, respectively, as a function of the carbon number, N,, are plotted.…”

Absorption of sulfur dioxide and nitric oxide by some amines and N‐cyclohexyl‐2‐pyrrolidone

“…The infinite dilution conditions were found in a similar manner. The solvent liquid loading (the weight of solvent coated on the substrate divided by the weight of substrate in the column) was increased until the activity coefficient or Henry's law constants did not vary (Parcher et al 1975). As an example, Figure 2 is a plot of Henry's law constant versus triethylenetetramine liquid loading.…”