Effects of resin I on the catalytic oxidation of n-C7 asphaltenes in the presence of silica-based nanoparticles

Abstract

This study aims to evaluate the effects of resin I on the n-C₇ asphaltene thermal decomposition under an oxidative atmosphere in the presence of hybrid nanoparticles (SNi1Pd1) of NiO and PdO supported over fumed silica nanoparticles. Resin I and n-C₇ asphaltenes were characterized by elemental analyses, thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The adsorption of resin I and n-C₇ asphaltenes was evaluated using heavy oil model solutions through a combined method of thermogravimetric analysis and softening point measurements. Adsorption isotherms were measured for individual resin I and n-C₇ asphaltene samples as well as for different n-C₇ asphaltene to resin I ratios of 7 : 3, 1 : 1 and 7 : 3. For the first time, competitive adsorption of n-C₇ asphaltene and resin I on functionalized nanoparticles with NiO and PdO is assessed. The oxidation tests were carried out in an air atmosphere for a specific n-C₇ asphaltene loading in each sample (ca. 0.20 ± 0.02 mg m⁻²). In this order, for samples adsorbed from different A : R ratios of 7 : 3, 1 : 1 and 3 : 7, the amounts of resin I adsorbed were 0.06, 0.10 and 0.20 ± 0.01 mg m⁻², respectively. Hence, the A : R ratios in the adsorbed phase were 10 : 3, 2 : 1 and 1 : 1. The catalytic effect was measured through thermogravimetric analysis coupled to Fourier transform infrared spectroscopy, which evaluated the effluent gases of the catalytic oxidation process. The adsorption isotherms were modeled using the solid-liquid-equilibrium (SLE) model, and the effective activation energies for the oxidation process of the adsorbate were calculated through the non-linear integral method of Vyazovkin (NLN). As a result, it was observed that the temperature of n-C₇ asphaltene decomposition did not vary significantly with the inclusion of resin I in the system. Rate of mass loss curves showed that the main peak temperatures of n-C₇ asphaltenes and resin I decreased drastically from approximately 500 °C to 250, 260 and 270 °C for resin I loadings over SNi1Pd1 nanoparticles of 0.20, 0.10 and 0.06 mg m⁻², respectively. However, the catalytic effect of the nanoparticles was indeed affected, as revealed by the increase in the estimated effective activation energy as the amount of resin I in the system increased. It is expected that this work opens a better outlook about the use of catalytic nanoparticles in the oil and gas industry, mainly in improved (IOR) or enhanced oil recovery (EOR) processes for heavy and extra-heavy oil upgrading.