In this study, metallic nickel and alumina ultradispersed nanoparticles were prepared in-situ in heavy oil phases composed of vacuum residue, VR, and vacuum gas oil, VGO, by means of reduction or thermal decomposition of dispersed aqueous precursors of the metals. The catalytic activity of the nickel and the alumina nanoparticles towards hydrocracking and thermalcracking of the heavy oil was assessed. The thermal behavior of adsorbed materials onto the in-situ prepared as well as commercial Al2O3 nanoparticles was studied under an oxidizing atmosphere. Results suggested that commercial Al2O3 has more adsorption affinity towards hydrocarbons from the heavy oil. Accordingly, ultradispersed commercial Al2O3 nanoparticles were employed for the thermalcracking of an even heavier crude.
Results show that the Ni0 was converted to Ni3S2 during the hydrocracking experiment. The catalyst promoted hydrogenation and free radical reactions and resulted in 50% reduction in asphaltenes and 70% reduction in resins, while improving the aromatics and saturates fractions. Two fold increase in the gaseous fraction and around 47% conversion of the residue, conv545+oC, occurred in the presence of the ultradispersed Ni catalyst. Alumina nanoparticles, on the other hand, contributed to the adsorption and thermalcracking of the heavy hydrocarbons. Uptake values and thermal behavior of adsorbed species with and without heptane or DCM washing suggested different types of adsorbed hydrocarbons between the in-situ prepared and the commercial alumina particles. Significant reduction in the viscosity and increase in the oAPI gravity were reported for samples undergoing thermalcracking for 2 h while containing 10000 ppm of alumina nanoparticles under 400°C, 0 rpm in a batch system arrangement. These conditions also resulted in the highest resins to asphaltenes, R/A, ratio and, thus the most stable product.