Vapor pressures and heats of vaporization of primary coal tars. Quarterly technical progress report, 1 January 1995--31 March 1995

摘要

The vapor pressure correlations that exist at present for coal tars are very crude and they are not considered reliable to even an order of magnitude when applied to tars. Sophisticated general correlative approaches are slowly being developed, based upon group contribution methods, or based upon some key functional features of the molecules. These are as yet difficult to apply to coal tars. The detailed group contribution methods, in which fairly precise structural information is needed, do not lend themselves well for application to very complex, poorly characterized coal tars. The methods based upon more global types of characterizations have not yet dealt much with the question of oxygenated functional groups. In short, only very limited correlations exist, and these are not considered reliable to even an order of magnitude when applied to tars. The present project seeks to address this important gap in the near term by direct measurement of vapor pressures of coal tar fractions, by application of well-established techniques and modifications thereof. The principal objectives of the program are to: (1) obtain data on the vapor pressures and heats of vaporization of tars from a range of ranks of coal, (2) develop correlations based on a minimum set of conveniently measurable characteristics of the tars, (3) develop equipment that would allow performing such measurements in a reliable, straightforward fashion. A significant amount of time has been devoted during this quarter to testing the equipment for measurements by the Knudsen effusion method. The basic technique was described in the 9th Quarterly Report how the performance of the apparatus was checked by measuring, as a function of temperature, the vapor pressures of anthracene between 25 and 130(degrees)C, pyrene between 35 and 125(degrees)C, and coronene between 145 and 235(degrees)C.