Effects of temperature and pressure on asphaltene particle size distributions in bitumen-diluent

Abstract

In order to investigate the effects of temperature and pressure on the size of asphaltene particles, a novel series of pressure and temperature cells were constructed and integrated with a Brinkmann Particle Size Analyzer. Four separate oils, from an asphaltic condensate to a heavy crude oil were examined using n-pentane and nheptane as diluents. Atmospheric pressure investigations with n-heptane as the diluent over the temperature range of 0°C to 50°C showed no change in particle size, but did reveal bimodal distributions. The effect of temperature from 0°C to 100°C and pressure from 2.2 MPa to 5. 6 MPa were successfully explored. Increasing the pressure induced a small change in the mean size of the particles, except for the Lindberg oil particles for which the mean size decreased slightly. A variation of the temperature from 0°C to 100°C showed little effect on asphaltene particle size, except upon the Border condensate. The heavier molecular weight oils from Cold Lake and Lindberg, Alberta formed 11 super agglomerates II or macro-agglomerates at 75 ° C and higher. The Border condensate and Countess oil both displayed instances when a bimodal size distribution was apparent. Most of the runs showed some suggestion of another distribution in addition to the main particle size distribution.