Synthesis and functionalization of carbon nanospheres from asphaltene fraction for crude oil upgrading and viscosity reduction

Nanoparticles provide a promising, cost-effective eco-friendly solution to the challenges posed by heavy-oil reservoirs, significantly enhancing oil recovery rates by reducing viscosity without requiring extensive thermal inputs. In this study, carbon nanospheres (CNSs) and functionalized-CNSs nanofluids were prepared by incorporating surfactants (T80 or BMIMCl). These nanofluids were evaluated for their efficacy in upgrading crude oil, particularly focusing on viscosity-reduction. Rheological tests were conducted across varying shear rates (60–300 s−1) and concentrations (0.02–3 wt.%) to comprehensively assess the impact of these additives on the crude oil's proprieties. The results showed a notable enhancement in crude oil viscosity reduction, with the following order observed: CNS-TiO2 < CNS-TiO2/DMIMCl < CNS-TiO2/T80, yielding reduction rates of 95%, 95.83%, and 97.08%, respectively, at an optimal dosage of 2.75 wt.% and a shear rate of 300 s−1. The surface functionalization of CNS particles and their crystallinity are the main mechanisms driving the reduction in oil viscosity. Moreover, the properties of the crude oil were investigated upon the utilization of CNS-TiO2/T80 nanofluid. It was found that this nanofluid led to a substantial reduction in sulfur content by 78.32% and a significant decrease in the percentage of heavier molecules, ranging from C12 to C35 and up to C36, with 47.76% and 97.98%, respectively.