Effect of Heteroatoms of Asphaltene Structure Models on Molecular Aggregation Behavior
Muhammad Fahri Afiki (a), Mia Ledyastuti (a*)

a) Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung
Jalan Ganesha 10, Bandung 40132, Indonesia
*mia.ledyastuti[at]itb.ac.id

Abstract

One of the problems in the petroleum industry is the formation of asphaltene molecular aggregates. Asphaltene is a petroleum fraction in the form of polycyclic aromatic compounds. Computational modeling can be used to investigate the mechanism of asphaltene molecular aggregation. An asphaltene molecule has been modeled using B3LYP level of theory with DFT-D4 dispersion correction for dimers and def2-SVP basis set. The asphaltene molecule is modeled as a polycyclic aromatic compound with variations of N, O, and S heteroatoms. The modeling is carried out on the monomer and dimer of the asphaltene molecule. The tendency of asphaltene monomer molecules to form dimers is analyzed by calculating the electrophilicity index (&#969-) which is a function of chemical hardness (&#951-) and electronic chemical potential (&#956-) of the molecule. The result shows that the presence of the N atom in a certain position increases the electron density in the aromatic ring. Meanwhile, the presence of O and S atoms in the aliphatic tail causes the electron density to shift towards each of these heteroatoms. The substitution of the carbon atom connecting the aromatic ring and aliphatic chain by the three heteroatoms causes the polarity of the asphaltene molecule to increase.

Keywords: asphaltene, DFT, heteroatom

Topic: CHEMISTRY AND MATERIAL SCIENCES