Structural characterization of asphaltenes obtained from hydroprocessed crude oils by SEM and TEM

Asphaltenes from Maya crude and its hydroprocessed oils at different reaction conditions were precipitated and studied by scanning and transmission electron microscopy (SEM and TEM). In order to better understand the changes occured in asphaltene structure during hydroprocessing the crude oil fractionation procedure with solvents was used to separate asphaltenes based on their solubility properties. Different asphaltene morphologies were observed depending on the mixture of solvents used for fractionating asphaltenes and reaction conditionsat which crude oil was hydroprocessed. A comparison between asphaltenes from hydroprocessed and pure Maya crude oil was carried out on the way to distinguish morphological changes at microscopic level. It was observed that removal of alkyl chains during hydroprocessing makes asphaltenes suffer a rearrangement in solid state favoring stacking of aromatic cores as determined by TEM. SEM microscopy allowed different fractions of asphaltenes for seeing that they are constituted by agglomerate particles, porous structures, and smooth surfaces.