Experimental and DFT studies on the effect of carbon nanoparticles on asphaltene precipitation and aggregation phenomena

Abstract In this study, a new class of carbon nanoparticles (CNPs) is synthesized for inhibition/dispersion of asphaltene precipitation and aggregation in unstable crude oil. The microscopy and asphaltene dispersant experiments are carried out to assess the effects of CNPs on asphaltene precipitation and aggregation. Also, density functional theory is applied to describe the mechanisms of asphaltene adsorption onto the CNPs surfaces. Experimental results demonstrate postponement of asphaltene onset of precipitation from 26 to 37 vol% n-C7 in the presence of 400 ppm of the CNPs which is ascribed to the extra high specific surface area of the CNPs. DLS analysis shows the average size of asphaltene aggregates adsorbed onto the CNPs reduces from 1730 nm in the blank oil to 255 nm in treated oil with CNPs. The results of DFT modeling demonstrate the strong hydrogen interaction between functional groups of the CNPs and active sites of asphaltene. Also, π–π interactions occur between electron cloud of aromatic rings of asphaltene and CNPs with minimum equilibrium distance of 2.94 A. The adsorption energy for the most stable complex of asphaltene and CNPs in the gas and solvent phases are −91.22 and −107.64 kJ/mol, respectively, confirming the strong chemisorption of asphaltene over the CNPs. This research reveals that synthesized CNPs with specific features such as high surface area, potential of covering the external shell with a wide variety of functional groups, low toxicity and cost, and environment-friendly can be successfully implemented as an efficient inhibitor and/or dispersant for asphaltene handling strategies.