Microstructural study of asphaltene precipitated with methylene chloride and n-hexane☆

This work presents a study of the microstructure, molecular structure and elemental composition of asphaltene precipitated from vacuum residue using a solvent mixture. The infrared spectroscopy (FTIR) results show vibration bands of functional groups such as aromatic C–H (4 adj H and 1 adj H) and sulfoxide (C2SO). Low vacuum scanning electron microscopy (LV-SEM) reveals a highly porous and a smooth surface asphaltene. C, S and V are the main elements identified by energy dispersive X-ray spectroscopy (EDS) analysis, though some variations in concentration were observed between the porous and the smooth surface asphaltene. Transmission electron microscopy (TEM) analysis shows that asphaltenes are constituted by nanometric particles (micelles) of ∼50 nm in diameter. These particles conform agglomerates (flocs) from ∼350 to ∼550 nm in size, some of them in layer arrangement with a tendency to graphitize. These results reveal important information about flocculation processes of the asphaltene.