Research Thrust I
Asphaltene Adsorption, Aggregation, and Interfacial Effect
Asphaltenes are polyaromatic constituents of fossil fuels (petroleum, tar, coal) that cause several important technical, economic and environmental problems. For instance, their low aqueous solubility and volatility coupled to high affinity to polar surfaces make asphaltenes a major constituent of oil slicks covering shorelines and sea life after oil spills.
Asphaltenes are also largely responsible for the poor energy efficiency of tar sands extraction: almost half of hydrocarbons in place are burnt to help produce the remaining half. This effect is partly due to the extreme tar viscosities caused by colloidal asphaltenes, as well as partly due to the ability of asphaltenes to strongly adsorb on polar surfaces and thereby hold tar, sand and water together. Asphaltenes adsorption on polar surfaces is very poorly understood. It has long been suggested that colloidal-like aggregates adsorbed whenever the driving force could not be clearly identified. A new paradigm has been proposed by researchers working together at CCNY and SINTEF based upon the relationship between molecular crowding and interfacial tension: asphaltenes would first adsorb as individual molecular ‘monomers’ due to the electronic properties of their polyaromatic cores. Recent DFT-based simulations in a collaboration between CCNY and LCPQ seem to confirm this conclusion.
The quantitative analysis of adsorption dynamics remains difficult due to the broad polydispersity of asphaltene molecular structures and weights, the non-linearity of adsorption mechanisms, and the lack of multi-component adsorption models. This proposal aims at solving these issues for water/oil and oil/solid interfaces using a combination of multi-scale simulations and experiments.
Quantum-based methods will generate interfacial conformations, adsorption energies, and interaction potentials for selected molecular structures, which will subsequently be transferred to classical molecular dynamic simulations to generate averaged models such as mixture adsorption isotherms and equation of states. The latter models will be coupled with diffusion calculations for direct comparison with experimental results (dynamic interfacial tension, quartz crystal microbalance) obtained with bulk asphaltenes or fractions of them (to separate components of different surface activity), whose molecular-level compositions and structures will be characterized by NMR. This approach will be complemented with lattice-Boltzmann simulations to capture the three-phase wettability behavior at droplet and particle scales.
CCNY: Vincent Pauchard, Sanjoy Banerjee, Robert Messinger, Joel Koplik, Taehun Lee, Fang Liu, Shaghayegh Darjani
SINTEF: Martin Fossen
INP-LGC: Olivier Masbernat
LCPQ: Aude Simon
IPF: Ulrich Scheler