Structure–Function Relations of Asphaltenes at the Interface
Year: 2023
Journal: Energy & Fuels, Volume 37, 16/11/2023
Authors: Andrews, A. Ballard; Bridot, Jean-Luc; Freudenthal, Oona; Langevin, Dominique; Mullins, Oliver C.
Comparisons of the properties of asphaltenes with very different chemical structures are essential to unravel their structure–function relationships. The different classes of asphaltenes considered here are coal-derived asphaltenes (CDAs) with dominant aromatic carbon, petroleum asphaltenes (PAs) with comparable fractions of aromatic and aliphatic carbon, and immature source-rock asphaltenes (ISAs) with large fractions of aliphatic carbon and also sulfoxide moieties. Recent interfacial rheology studies indicate that PAs and ISAs exhibit somewhat nonlinear, largely elastic dilatational modulus upon significant compression, while CDAs exhibit very large repulsion and film collapse upon even modest compression. These observations indicate the critical rheologic role played by peripheral aliphatic substituents of the asphaltene molecule. Here, the behavior of different asphaltenes and model compounds in forming Langmuir–Blodgett (LB) films is used to probe structure–function relations of interfacial asphaltenes. The ease of LB film preparation of PAs and several model compounds and the inability to form LB films of CDAs are consistent with previous findings that CDA films collapse under modest compression while PAs form robust monolayer films.
