Theoretical Study of the a-xand ∏-∏-Interactions in Heteroaromatic Monocyclic Molecular Complexes of Benzene, Pyridine, and Thiophene Dinners: Implications on the Resin-Asphaltene Stability in Crude Oil

摘要

Asphaltenes are molecular structures that are composed of polyaromatic and polyheteroaromatic condensed nuclei, where benzene, pyridine, and thiophene rings are the smallest basic structural units. A deep understanding of the electronic features governing the interaction between these primary units is essential for subsequent rationalization of the nature of larger scale inter-and intramolecular interactions between asphaltenes, which could help to enrich die knowledge of why these compounds tend to aggregate and then to flocculate in oil operation processes. In this work, we study the intermolecular interaction potentials of benzene-benzene, thiophene-thiophene, pyridine-pyridine, benzene-pyridine, benzene-thiophene, and pyridine-thiophene molecular complexes by using the self-consistent generalized gradient approximation density functional theory with the Perdew-Wang 91 functional (DFT/GGA PW91) in conjunction with the DNP double numerical basis set In order to understand the dominant electronic interaction of these complexes in terms of the O-71 and ∏-∏ electronic interactions, the three most important structural conformations (parallel, antiparallel, and T-shaped) were chosen. These calculations were performed with the DMo13Materials Studio 4.0 program. It was found that the results of the interaction energies calculated with DFT/GGA PW91 are consistent with those reported in the literature for benzene and thiophene dimers. To gain insight about the stability of the studied complexes, their molecular interaction polarizability was evaluated at the PW91PW91/6-31+G(d,p) level of theory. This property allowed us to explain the attraction and repulsion that occur in these dimer formation processes. These statements were also corroborated at the MP2 and MP4 levels of theory for benzene, pyridine, and thiophene homodimer parallel conformations. Additional CCSD/6-31+G(d,p) calculations were performed for the interaction energies of these dimers. To correlate these findings with the stability of crude oil, a real asphaltene and resin dimer complex structure was fully optimized at the PW91/DNP level. The results of interaction energy, which is in good agreement with the value predicted in the literature, and the large value of the interaction polarizability allowed us to explain the stability of these systems.