(155f) Asphaltene Destabilization Mechanism Investigated By Ultra-Small Angle X-Ray Scattering and in Situ Titration

Asphaltene destabilization causes plugging in oil-transportation pipelines and induces complications in refineries by fouling. Micron size insoluble asphaltenes clusters have been extensively investigated by optical microscopy (>1 micron detection), and soluble asphaltene behavior has been studied by small angle X-ray scattering (<50 nm detection). However, the gap in characterization from 50 nm to 1 micron has left the mechanism of asphaltene destabilization obscure. Ultra-small-angle X-ray scattering (USAXS) was recently demonstrated by our team to be a powerful technique that could monitor this previously overlooked length scale between 50 nm and 1 micron (Yang et al., 2018) (Ismail et al., 2018). However, the rate of asphaltene destabilization can vary significantly with slight changes in heptane concentration around the “onset point,” and in situ monitoring of asphaltene destabilization is necessary to capture the initial stages of this process. In this talk, we will discuss the asphaltene destabilization mechanism using continuous length scale monitoring to understand the gradual association of asphaltene molecules to micron size insoluble clusters. We implemented a flow-cell system to investigate the real-time formation of nanoaggregates, soluble and insoluble clusters. Heptane was used as an anti-solvent and titrated into an asphaltenes-toluene solution at a different flow rate for precise control of the rate of asphaltene destabilization. USAXS was used to monitor the overall destabilization process at a time resolution of <5 minutes. This technique is effective to probe the size, internal structure, overall shape, and surface morphology within a range from 1 nm to 5 microns. The results demonstrate that asphaltenes aggregate together to form insoluble particles with size on the order of 100 nm which then further cluster form insoluble fractal flocs of size >1 micron. Direct monitoring of the asphaltene destabilization process from the initial stages of aggregation is essential to understand the best modeling approaches for phase behavior, aggregation, deposition, and inhibition mechanisms of action. These results help to understand the role of solvent environment, temperature, and pressure on asphaltene stability to provide constructive knowledge for asphaltenes inhibitor research.