Date of Award


Document Type


Degree Name

Master of Science (MS)


Chemical Engineering


The major purpose of this study was to determine the vapor-liquid equilibrium of A04 (anthracene oil #4) solvent at typical coal liquefaction operating conditions. The experimental apparatus used was the University of North Dakota's single-stage, hot charge, batch autoclave system which was specially designed to simultaneously sample both liquid and vapor phases. Six autoclave runs were made according to the following test matrix: (a) one run to determine the vapor pressure of A04 at temperatures ranging from 20 to 440 C, and (b) five time sample runs to determine the AO4 vapor-liquid equilibrium distribution at temperatures ranging from 300 to 440 C and average autoclave pressures of 2100, 2560, 3050, 3635, and 4010 psia. Each autoclave run consisted of a 1200 gram charge of solvent, and nitrogen gas was used to build reactor pressures to the desired levels.

The vapor pressure of A04 increased with increasing temperature from a low value of 16 psia at 21.5 C to a high value of 354 psia at 443.7 C. This increase in vapor pressure occurred gradually at the lower temperatures (21.5 to 100 C) and with increasing slope as the temperature increased. The Clausius-Clapeyron relationship was used to further analyze the pressure-temperature data. From this analysis, three distinct enthalpies of vaporization corresponding to the light, middle, and heavy oil components of AO4 (assuming ideal gas behavior) were determined to be 979, 6316, and 30,920 Btu/lbmole, respectively. In addition, results indicate that the molar volume of A04 in the gas phase dramatically decreased from a high value of 239.8 cu.ft./lbmole at 16.5 psia to a value of 6.9 cu.ft./lbmole at 134 psia, and then leveled out at a final value of 0.5 cu.ft./lbmole at 328 psia. It was also found that as the temperature increased, the weight fraction of A04 in the vapor phase increased from 0.8 percent to a maximum of 68 percent. At the highest temperature studied (440 C), the weight fraction of A04 in the vapor phase varied from 45 percent at 4010 psia to 68 percent at 2560 psia. In addition, the fractions of light and middle oils present in the liquid phase decreased from 88 percent to 69 percent as the temperature increased.