Effect of Dilution Ratio on Amount of Asphaltenes Separated from Stock Tank Oil

We have investigated the effect of n‐alkane dilution on the amount of asphaltene separated from stock ‐tank oil. Asphaltenes were produced from three different oils by mixing each oil with varying amounts of n‐alkanes, including n‐pentane, n‐hexane, and n‐heptane. The n‐alkane:oil ratio ranged from 1∶1 to 1000∶1. With increasing n‐alkane:oil ratio, the amount of separated asphaltene initially increased, passed through a maximum, then decreased gradually with further dilution. The maximum occurred at an n‐alkane:oil ratio of around 30∶1 to 40∶1 for n‐hexane and n‐heptane, and 80∶1 for n‐pentane. A two‐component thermodynamic model based on Flory‐Huggins theory was adapted to match the observed trend of produced asphaltene by assuming a polydisperse model of the asphaltene fraction.