Nanotechnology has many successful applications in different fields but recently its application for oil and gas industries has increased because of their exceptional physical and chemical properties. Despite of the great deal of interest in the use of nanoparticles as adsorbents and catalysts for enhancing heavy oil upgrading and recovery, still the effect of nanoparticle size on their adsorption and catalytic behaviour towards visbroken heavy hydrocarbons remain unclear. This study focuses on the effect of NiO nanoparticle size (ranging from 5-80 nm) on adsorption and post-adsorption catalytic oxidation of n-C5 vis-broken asphaltenes. The nanoparticles are prepared by thermal dehydroxylation of Ni(OH)2 following the hydrothermal technique. Using batch adsorption equilibrium measurements of n-C5 vis-broken asphaltenes dissolved in toluene coupled with thermogravimetric analysis, we studied the adsorptive and catalytic behavior of NiO with several nanosizes towards asphaltenes. Adsorption isotherms were described by the Solid-Liquid-Equilibrium model (SLE), and the catalytic behavior of the nanoparticles were compared on the basis of the effective activation energies trends using the isoconversional method. Supplementary, computational modeling was demonstrated to investigate the chemistry behind the changes on adsorption capability and catalytic activity of the different sizes of NiO nanoparticles.
This study confirms that nanosize plays vital roles in selective adsorption and subsequent catalytic decomposition of polar heavy hydrocarbons. The study opened up a whole new train of thoughts and widens our general understanding of the surface functionality and chemical activity of nanoparticles.