Deviation from Equilibrium Thermodynamics of an Asphaltene Model Compound during Compression-Expansion Experiments at...

Area of Science:

• Colloid and Surface Science
• Petroleum Chemistry
• Materials Science

Background:

• Asphaltenes significantly influence crude oil properties and interfacial behavior.
• Model compounds like C5PeC11 are essential for understanding asphaltene interfacial phenomena.
• Previous studies noted unexplained deviations in asphaltene model compound interfacial behavior.

Purpose of the Study:

• To investigate the interfacial behavior of C5PeC11 at decane-water and air-water interfaces.
• To elucidate the reasons behind the observed non-thermodynamic responses.
• To connect molecular-level interactions with macroscopic interfacial phenomena.

Main Methods:

• Multiscale approach combining Langmuir trough compression-expansion experiments (rectangular and radial).
• Dynamic interfacial stress relaxation measurements.
• Fluorescence microscopy for imaging molecular aggregation.

Main Results:

• Non-thermodynamic interfacial responses are attributed to dominant intermolecular forces over mechanical compression.
• Stable aggregation at the air-water interface prevents the dynamic effect in subsequent compressions.
• The decane-water interface allows reproducible dynamic effects due to oil phase influence on interfacial free energy.

Conclusions:

• Interfacial behavior of asphaltene model compounds is governed by a dynamic effect driven by intermolecular forces.
• The oil phase plays a critical role in the stability and reproducibility of interfacial dynamic effects.
• Multiscale investigations are crucial for distinguishing thermodynamic equilibrium from dynamic responses in interfacial systems.