Microwave-Assisted Heavy-Oil Treatment Using an Fe3O4–Graphene Oxide Nanohybrid: Thermal Response, Post-Cooling Viscosity, and Characterization of the Recovered Asphaltene-Rich Fraction

Microwave-assisted treatment has potential for improving the handling of heavy crude oil, but direct microwave heating can be limited by the weak microwave response of the oil phase. In this study, an Fe3O4–graphene oxide (Fe3O4–GO) nanohybrid was evaluated as a microwave-responsive additive to enhance heating and improve the postcooling rheological response of heavy crude oil. The nanohybrid was prepared from Fe3O4 nanoparticles and oxygen-functionalized GO and characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and vibrating-sample magnetometry (VSM). Heavy-oil dispersions containing 0.05 and 0.10 wt % Fe3O4–GO were exposed to microwave irradiation for 1–5 min at two power settings, and viscosity was measured after cooling all samples to 25 °C. The greatest heating enhancement was recorded for the oil containing 0.10 wt % Fe3O4–GO at 80% microwave power, where the temperature reached 81.7 °C after 5 min and the average heating rate was 11.56 °C/min. The lowest mean postcooling apparent viscosity among the tested conditions, 301 cP, was obtained after 3 min, corresponding to a 28.84% reduction relative to the initial viscosity of the same formulation. This lowest-mean-viscosity condition among those tested occurred before the highest final temperature was reached, indicating that longer irradiation did not necessarily produce the greatest viscosity reduction. The treatment also increased the apparent n-heptane-insoluble content and produced comparative differences in FTIR and nuclear magnetic resonance (NMR) spectra, scanning electron microscopy (SEM) images, and energy-dispersive X-ray spectroscopy (EDS) results of the recovered asphaltene-rich fractions. Overall, Fe3O4–GO-assisted microwave treatment shows laboratory-scale potential for enhancing heavy-oil heating and reducing postcooling viscosity.