The Role of Allotropic Forms of Carbon-Based Nanostructures on Asphaltene Stability in Crude Oil Medium: Experimental and Computational Studies

Asphaltene precipitation and deposition in various sections of the oil production system pose significant flow assurance challenges, leading to considerable economic implications. Previous studies highlight the significance of carbon-based nanostructures in inhibiting and managing asphaltene-related problems in the petroleum industry. However, the impact of different allotropic forms of carbon-based nanostructures on asphaltene formation and stability in crude oil has not yet been explored. Here, microscopy and asphaltene dispersant analyses are utilized to assess the effect of different allotropic forms of carbon-based nanostructures on asphaltene precipitation in crude oil. Also, density functional theory (DFT) and density functional tight binding (DFTB) methods are applied to describe the molecular behavior of the carbon nanostructures (CNSs) and asphaltene. Treatment of crude oil with 100 ppm of carbon-based nanostructures results in delay of asphaltene onset of precipitation from 23 vol % n-C7 to 27, 36, and 41 vol % for graphene (G), carbon nanotubes (CNT), and fullerene-like carbon particles (FCP), respectively. The efficiency of the carbon-based nanostructures for postponement of asphaltene onset of precipitation (AOP) and reducing the size of asphaltene aggregates is in following decreasing order of FCP > CNTs > G. This performance of the carbon-based nanostructures is allocated to electron-cloud formation in the oil phase and strong π–π interactions between asphaltene molecules and the electron-cloud of aromatic rings of nanostructures. Higher efficiency of FCP compared to other nanostructures is described by the more effective surface geometry of FCP, which causes stronger π–π interactions between asphaltene aggregates and nanostructures. In contrast to various types of nanoparticles, carbon-based nanostructures, such as fullerene-like carbon particles and carbon nanotubes, effectively manage asphaltene precipitation and aggregation at low dosages of approximately 100 ppm or less. The minimum equilibrium distance for each carbon-based nanostructure is about 2.5 Å, inferring the key role of the vdW forces in the stability of these complexes. DFTB modeling indicates that the binding energy values increase as the curvature of the carbon allotropes decreases.