Using Atomic Force Microscopy To Detect Asphaltene Colloidal Particles in Crude Oils
2017
Balestrin, Lia Beraldo da Silveira | Cardoso, Mateus Borba | Loh, Watson
Asphaltene precipitation is a key problem in the petroleum industry and has been the focus of many studies on their aggregates present in crude oils and on the effects of additives to inhibit their formation and/or deposition. However, most of these studies were performed using model systems, such as asphaltene solutions in organic solvents, making the comparison to real systems more difficult. Herein, we combine different modes (height and phase modes) of atomic force microscopy to identify colloidal particles associated with asphaltene aggregates present in crude oils. Following this methodology, a mica plate is inserted into oil and washed with toluene to remove excess oil. In addition, nanoparticles with dimensions ranging from a few to hundreds of nanometers were observed. Overall, more particles are observed when flocculants, such as heptane, are added, whereas their size decreases when a good solvent for asphaltenes (toluene) is added. Similar colloidal particles are also observed repeating this methodology with asphaltene solutions in toluene, confirming that these somewhat reproduce the asphaltene association observed in crude oils. The addition of an inhibitor, such as dodecylbenzenesulfonic acid, led to observation of more and smaller nanoparticles. The present experimental approach not only confirms the existence of asphaltene colloidal particles in crude oils but also provides an accessible methodology to directly assess how these particles are affected by changes in oil composition or inhibitors.
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