Melting and Fluid Behavior of Asphaltene Films at 200−500 °C

Abstract

The behavior of the asphaltene fraction in crude oils and bitumens plays a significant role in production, separation, and transportation, but low-temperature precipitation measurements are of limited value in projecting the physical state at refining temperatures. The melting behavior of five types of asphaltenes was observed by heating thin films at ca. 16.5 °C/s on Curie-point alloys in an inert atmosphere. The heptane-insoluble asphaltenes from Arab Heavy, Arab Light, Athabasca, Gudao, and Maya all showed evidence for formation of a liquid melt at temperatures between 214 and 311 °C, which was significantly lower than initial reaction temperatures of ca. 400 °C. The majority of the n-heptane-insoluble asphaltenes must exist, therefore, in either a molten phase or as a solution at process temperatures typical of distillation and reaction. With an average melting temperature of 294 °C, the Maya melting point was significantly higher than the melting points of Athabasca, Arab Light, and Arab Heavy, which were in the range of 224−245 °C. This difference in melting point did not correlate with any average chemical properties.