(261c) Moving Away from Critical Parameters: A New Approach to Asphaltenes

Authors: 
Hoepfner, M. P., The University of Utah

Traditionally, the overwhelming complexity of modeling asphaltene processes is simplified to a few key critical parameters to describe such systems. These can include a critical onset condition for asphaltene phase separation or deposition, or the critical nanoaggregate concentration (CNAC) that is used to describe the incipient formation of aggregated structures in good solvents. Flexibility in tunable model parameters facilitates some laxity in rigorous descriptions of asphaltene behavior; however, it is desirable to obtain a continuous description of asphaltene behavior in order to accommodate for the vast polydispersity in asphaltene molecular structures. Recent investigations into asphaltene deposition, aggregation and structure have revealed that critical parameters are not necessary to describe asphaltene behavior, and will be discussed in this talk [1-3]. For example, measurement of the phase boundary for asphaltene precipitation has been shown to be highly time-dependent. Consequently, a critical onset value will be dependent on the technique used for solids detection and the experimental time allocated. However, techniques that are highly sensitive to changes in asphaltene size, such as small-angle neutron scattering, have revealed that small quantities of asphaltenes can slowly precipitate that are virtually impossible to detect with standard approaches [2]. Similar behavior was also observed in capillary asphaltene deposition experiments [1]. Regarding the nanoscale structure of asphaltenes, recent studies have demonstrated that asphaltene nanoaggregate formation and subsequent clustering can also be described as continuous processes [2,3]. Only by knowing the “true” behavior of asphaltenes can the consequences of assumptions or simplifications be accurately assessed for high-throughput and applied studies.

[1] Hoepfner, M. P., et al., “A Fundamental Study of Asphaltene Deposition,” Energy & Fuels, 27 (2), 2013.

[2] Hoepfner, M. P., et al., “The Fractal Aggregation of Asphaltenes,” Langmuir, 29 (28), 2013.

[3] Hoepfner, M. P. and Fogler, H. S., “Multiscale Scattering Investigations of Asphaltene Cluster Breakup, Nanoaggregate Dissociation, and Molecular Ordering,” Langmuir, 29 (49), 2013.