Structure-Dynamic Function Relations of Asphaltenes

Asphaltene molecular and nanocolloidal structures have largely been resolved enabling development of structure-function relations of asphaltenes. Atomic force microscopy (AFM) and scanning tunneling microscopy (STM) have provided the first direct molecular structures of many asphaltenes with extension into broader distributions of petroleum pitch. These studies confirmed previous findings of dominant island architecture, moderate-sized polycyclic aromatic hydrocarbons (PAHs) with significant variability in the number and geometry of these rings. The Yen-Mullins model of centroids of molecular and nanocolloidal species of asphaltenes continues to provide foundations for thermodynamic treatment of crude oils, for both bulk and surface. Herein, these asphaltene structures are subject to the stringent test of modeling dynamic function along with static function. Recent results impact evaluation of the molecular management of heavy oil refining for the hydrotreatment process. Roughly, 25,000 reactions were considered acting on ∼17,000 molecules. Reactants and products are probed with ultrahigh-resolution mass spectrometry. In modeling, consistency is required with AFM molecular imaging results of asphaltenes. Excellent agreement is obtained between modeling and experiment, increasing accuracy and robustness. Thermodynamic treatments of asphaltenes in bulk and surface are shown within a structure-dynamic function setting. Two oilfield reservoirs are reviewed which are undergoing different diffusive processes in geologic time. The dynamic model to evaluate both reservoirs couples the simplest solution of the diffusion equation with a quasi-equilibrium state employing the Yen-Mullins model in parts distant from the diffusive process, and excellent agreement between modeling and measurement is obtained. For interfacial tension (IFT), a static model employing the simple Langmuir equation successfully treats solutions of moderate asphaltene concentrations and is consistent with AFM images of asphaltenes. A first-order dynamic correction of time evolution of the IFT can be accounted for considering some molecular polydispersity. Structure-dynamic function relations are established for asphaltenes in three very different arenas.