THE EFFECTS OF HETEROATOMS IN ASPHALTENE STRUCTURE MODELS ON MOLECULAR AGGREGATION BEHAVIOR

• Main Author: Fahri Afiki, Muhammad
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/75363
• Institution: Institut Teknologi Bandung

One of the problems in petroleum industry is the formation of asphaltene molecular aggregates. Asphaltene is a petroleum fraction in the form of polycyclic aromatic compounds. The presence of heteroatom in asphaltene molecule could increase asphaltene intermolecular interaction and its aggregation behavior. Computational modeling is used to investigate the mechanism of asphaltene molecular aggregation. An asphaltene molecule has been modeled using ORCA software with B3LYP functional, D4 dispersion correction, and def2-SVP basis set. The asphaltene molecule is modeled as a polycyclic aromatic compound with a variation of N, O, and S heteroatoms on four sites. The model is carried out on the monomer and dimer of the asphaltene molecule to represent asphaltene molecule and aggregate. The tendency of asphaltene monomer molecules to form dimers is analyzed using HOMO-LUMO, electrostatic potential, and delocalization extent of monomer, while thermodynamic parameter, reduced density gradient, independent gradient model, and atoms in molecules analysis is done on dimer. The result showed that heteroatom presence on aromatic moiety of asphaltene molecule increases the molecular polarizability and supports ? interaction. When a heteroatom is located on far side of aromatic moiety, the electron density shifts toward each heteroatom and causes an increase of hydrogen bond formation tendency. The spontanity of dimerization is enthalpy- driven. Analysis on the asphaltene dimer revealed the ? interaction and hydrogen bond as dominant mode of interaction. The strength of hydrogen bond is influenced by the type and size of localized orbital as the characteristic of each heteroatom.