Thermodynamic Equilibria in Xylene Isomerization. 2. The Thermodynamic Properties ofm-Xylene

Abstract

Measurements leading to the calculation of the ideal-gas thermodynamic properties for m-xylene are reported. Experimental methods included adiabatic heat-capacity calorimetry (5 K to 430 K), vibratingtube densitometry (323 K to 523 K), comparative ebulliometry (309 K to 453 K), and differential-scanning calorimetry (DSC). The critical temperature was measured by DSC. Saturation heat capacities for the liquid phase between 430 K and 550 K and the critical pressure were derived with the vapor-pressure and DSC results. Results were combined with an enthalpy of combustion reported in the literature to derive standard molar entropies, enthalpies, and Gibbs free energies of formation at selected temperatures between 250 K and 550 K. The standard state is defined as the ideal gas at the pressure p ) p°) 101.325 kPa. Standard entropies are compared with those calculated statistically on the basis of assigned vibrational spectra for the vapor phase. All results are compared with literature values. † Contribution No. 361 from the Bartlesville Thermodynamics Group.

Possible precursors and products of deep hydrodesulfurization of gasoline and distillate fuels III. The thermodynamic properties of 1,2,3,4-tetrahydrodibenzothiophene

“…The Bartlesville Thermodynamics Group successfully applied this formulation for third virial coefficients in analyses of the thermodynamic properties of a range of compounds in recent years. The list of compounds studied includes benzene and methylbenzene [30], the xylenes [61][62][63], 2-methylaniline [64], pyridine [65], the methyl pyridines [66,67], and the dimethylpyridines [68]. In all the listed cases the agreement between the properties derived using this formulation and those obtained from statistical thermodynamics via accurate spectroscopic measurements has been better than 0.1% over a temperature range of greater than 250 K. Third virial coefficients are required for accurate calculation of the volume of gas for pressures greater than 0.1 MPa.…”

Thermodynamic properties of the methylpyridines. Part 2. Vapor pressures, heat capacities, critical properties, derived thermodynamic functions between the temperatures 250 K and 560 K, and equilibrium isomer distributions for all temperatures ≥250 K

“…Second virial coefficients were estimated with the corresponding-states equation of Pitzer and Curl, (32) and third virial coefficients were estimated with the corresponding-states method of Orbey and Vera. (33) This formulation for third virial coefficients was applied successfully in analyses of the thermodynamic properties of pyridine, (34) benzene and methylbenzene, (24) 2-methylaniline, (35) the xylenes, (36)(37)(38) ethylbenzene, (39) and the dimethylpyridines. (40) Uncertainties in the virial coefficients were assumed to be 10 per cent.…”

“…It has been shown (24,(34)(35)(36)(37)(38)(39)(40) that reconciliation of standard entropies T 0 S o m (cal) derived from thermophysical property studies (table 8) with standard entropies T 0 S o m (stat) derived with assigned vibrational spectra and the methods of statistical mechanics can be exploited cent. The method used to estimate the uncertainties was described previously.…”

Possible precursors and products of deep hydrodesulfurization of gasoline and distillate fuels IV. Heat capacities, enthalpy increments, vapor pressures, and derived thermodynamic functions for dicyclohexylsulfide between the temperatures (5 and 520) K

“…[25], and third virial coefficients were estimated with the corresponding-states method of Orbey and Vera [26]. This formulation for third virial coefficients was applied successfully in analyses of the thermodynamic properties of a range of compounds in recent years including benzene and methylbenzene [27], the xylenes [28][29][30], 2-methylaniline [31], pyridine [32], the methyl pyridines [33,34], and the dimethylpyridines [35]. In all cases the agreement between the properties derived using this formulation and those obtained from statistical thermodynamics via accurate spectroscopic measurements has been better than 0.1% over a temperature range of greater than 250 K. Third virial coefficients are required for accurate calculation of the volume of gas for pressures greater than 0.1 MPa.…”