Characterization of Asphaltenes from Brazilian Vacuum Residue Using Heptane−Toluene Mixtures

Brazilian vacuum residue (VR) was separated into insoluble and soluble fractions using n -heptane−toluene mixtures (Heptol). Coking tests performed on the soluble fractions showed that asphaltenes vary in regard to the extent to which they form coke. VR asphaltenes were subfractioned into AS 0−10%, AS 10−20%, AS 20−30%, and AS 30−40% by stepwise extraction using Heptol. The AS 20−30% and AS 30−40% fractions had greater aromaticity and a higher proportion of quaternary aromatic carbons, as well as a larger unit size. These type II asphaltenes produced more coke than did type I asphaltenes, which consist of the AS 0−10% and AS 10−20% fractions.