Thermodynamic Properties of Biphenyl: Topical Report.

摘要

Ideal-gas thermodynamic properties for biphenyl based on accurate calorimetric measurements were determined between 300 and 700 K, well into the range of typical chemical process temperatures. The calorimetrically derived values provide a firm basis for the prediction of thermodynamic properties for a large family of molecular structures including many substituted biphenyls (such as PCB's) as well as polyphenyls of arbitrary size. Also, results highlighted ambiguities common in the statistical calculation of thermodynamic properties of polycyclic molecules. Critical-property measurement using a differential scanning calorimeter (DSC) showed the commonly accepted assessed value to be in error. This value serves as a ''cornerstone'' in group-contribution critical property estimation schemes, which often are employed by engineers in corresponding-states correlations for the estimation of a great variety of physical properties. Thermodynamically-consistent sublimation vapor pressures were derived to show which of the many literature values are valid; an essential step in the validification of the many reported PCB vapor-pressure measurements, which are key to environmental-impact considerations. Derived Gibbs energies of formation allow the calculation of chemical equilibria in the biphenyl/hydrogen reaction network (published in a companion report; Topical report NIPER-403), which has important ramifications in alternate fuel processing. 85 refs., 11 figs., 16 tabs.