Relationship between Asphaltene Adsorption on the Surface of Nanoparticles and Asphaltene Precipitation Inhibition During Real Crude Oil Natural Depletion Tests

Using nanoparticles for adsorbing asphaltene is an efficient method for upgrading actual oil samples compared to other expensive mechanical treatments or even solvents, such as n-pentane and n-heptane, and surfactants. This study uses nickel–zeolite oxide nanoparticles for asphaltene adsorption and solving asphaltene precipitation problems. Although nickel–zeolite oxide nanoparticles have been used in previous studies as an asphaltene adsorbent, observing the relationship between asphaltene adsorption on their surface and asphaltene precipitation in the presence of nanoparticles during the actual process is not covered. For addressing this relation, we performed a series of experiments included Fourier-transform infrared spectroscopy (FTIR), CO۲–oil interfacial tension tests, Langmuir and Freundlich isotherm models, and natural depletion tests in the presence of nickel–zeolite oxide nanoparticles. The Langmuir model better fitted the adsorption data than the Freundlich model, which shows that the adsorption occurs on a homogeneous surface with monolayer coverage. Based on the CO۲–oil interfacial tension results, there are two different slope forms in interfacial tension readings as pressure increases from ۱۵۰ to ۱۶۵۰ psi. Due to asphaltene aggregation, the second slope (۹۰۰–۱۶۵۰ psi) is slower than the first one (۱۵۰–۹۰۰ psi). Three pressures of ۱۳۵۰, ۱۵۰۰, and ۱۶۵۰ psi and nickel–zeolite oxide nanoparticles at a concentration of ۳۰ ppm were selected for the natural depletion tests, and the basis of selection was high-efficiency adsorption at these points. As pressure decreased from ۱۶۵۰ to ۱۳۵۰ psi, asphaltene precipitation changed from ۸.۲۵ to ۱۰.۵۲ wt % in the base case, and it varied from ۵.۱۷ to ۷.۵۴ wt % in the presence of nickel–zeolite oxide at a concentration of ۳۰ ppm. Accordingly, nickel–zeolite oxide nanoparticles adsorbed asphaltene on their surface correctly, and the amount of asphaltene precipitation decreased in the presence of nickel–zeolite oxide nanoparticles.

Keywords:

Adsorption , Asphaltene , CO۲–oil interfacial tension tests , Isotherm models , Nickel–zeolite oxide nanoparticles