Transmission electron micrographs obtained with the freeze-fracture re
plication technique on three typical Chinese vacuum residues and their
fractions demonstrate that petroleum vacuum residues are colloidal sy
stems, in which asphaltenes (the n-heptane-insoluble, toluene-soluble
fraction) and heavier resins constitute the dispersed phases and the r
emaining lighter resins, aromatics and saturates the dispersing media.
(C) 1996 Elsevier Science Ltd. .