Probing Interfacial Structure and Dynamics of Model and Natural Asphaltenes at Fluid-Fluid Interfaces.

Abstract

Asphaltenes are largely responsible for crude oil interfacial behavior. Due to their complex molecular nature, studying connections between interfacial properties and molecular structure is challenging, and these connections remain unclear. Several groups have reported on the interfacial behavior of asphaltenes, but a unified picture of both interfacial dynamics and thermodynamics is still missing. We seek to establish connections between asphaltene interfacial morphology and interfacial dynamics by combining interfacial dilatational deformation with microscopic structural imaging analysis. Understanding the behavior of natural asphaltene samples is made difficult by the inherent molecular variability. Therefore, we have also studied the behavior of an asphaltene model compound to draw fundamental structure-property relationships. This work contains simultaneous interfacial deformation and microscopy in systems of natural and model asphaltenes at air-water and decane-water interfaces. How the dynamics of natural asphaltenes influences the morphological and thermodynamic state of the air-water and decane-water interfaces is discussed based on the deviations observed between isotropic and anisotropic deformations. Areas where model asphaltenes can help us to understand the behavior of natural asphaltenes are identified such as its high surface pressure activity and aggregation character. An aggregation mechanism for model and natural asphaltenes is proposed based on an observed relationship between microscopic and millimetric aggregates.