Aggregated structure of flocculated asphaltenes

Many petroleum processing problems are related to asphaltene flocculation. A detailed understanding of the colloidal structure of asphaltenes in oil c an play a decisive role in improving processing facilities and/or operating conditions. The structure of the flocculated part of the asphaltenes of a crude oil far above the flocculation threshold was studied to understand it s links with macroscopic phase separation. Asphaltene filtrations were perf ormed using filter pore sizes from 0.025 to 10 mum. According to small angl e X-ray scattering (SAXS) spectra and density measurements, these extracted asphaltenes in toluene solution did not have any physical differences. mea surements of nanometric sizes for the dispersed par articles after dissolut ion in toluene show that micron-size flocculated asphaltenes are strongly a ggregated structures. Therefore, filtration experiments separate asphaltene s corresponding to various aggregates of similar entities using electron mi crographs of asphaltene powers show spherically shaped aggregates of micron size. SAXS and USAXS techniques were used to investigate the internal stru cture of the asphaltenes powder. The aggregates are clearly a compact organ ization of asphaltenic material. This dense structure explains why floccula ted asphaltenes are subject to sedimentation, which induces the visible mac roscopic phase separation.