Date of Award


Document Type


Degree Name

Master of Science (MS)


Chemical Engineering



This thesis details the vapor-liquid equilibrium of a simulated coal liquefaction solution at typical reaction conditions. The test solution contained 25 mass percent solvent refined lignite (SRL) in an anthracene oil (A04). Six autoclave runs were performed using the University of North Dakota Energy Research Center's (UNDERC) single- stage, hot- charge, batch autoclave system; one to determine the vapor pressure of the solution, and five runs to determine the pressure and temperature effects on the vapor-liquid behavior. The five runs were conducted at near constant pressures, averaging 2050, 2570, 3077, 3629, and 4020 psia. During each run the temperature was increased from 300° C to 440° C with samples taken at 20° C intervals. The A04-SRL solution used was spiked with CaCO^ in order to determine the vapor-liquid distribution. A tetrahydrofuran (THF) solubility test was used to find the amount of CaCO^ in the liquid samples. Microdisti11a- tion was used to determine the compositions of both the liquid and vapor samples.

Data from the vapor pressure run were fit to the Clausius-Clapeyron equation which yielded two linear regions. The first region was from 215° C to 375° C with an enthalpy of vaporization (AH) value of 7200 calories/mole. The second region was from 410° C to 450° C with a AH value of 28,000 calories/mole.

Data from the five time sample runs were fit to a modified version of the Clausius-Clapeyron equation. The physical significance of the relationship was masked by liquefaction reactions. Due to the reactions, which converted heavier oils to lighter products, the mass percent of heavy and residual oils in the liquid phase remained nearly constant and independent of both temperature and pressure. The mass of the vapor phase decreased with increasing pressure at the lower temperatures, but appeared to be independent of pressure at 440° C.