In this work, the catalytic performance of a synthesized dispersed Ni-based catalyst amorphous catalytic system of Ni(NO3)(OH) in the hydrothermal upgrading of high-sulfur Cuban extra-heavy oil at ...temperatures of 200 and 300 °C for a duration of 24 h was evaluated. The synthesized Ni-catalyst predominantly exhibits an amorphous structure, which is primarily attributed to nickel hydroxonitrate (Ni(OH)(NO3)), as verified through X-ray diffraction and thermogravimetric Fourier transform infrared analyses. The results show that the presence of the synthesized catalyst in the upgrading system improves the physical and chemical properties of the upgraded oil samples compared to non-catalytic aquathermolysis results. The application of the Ni-based catalyst resulted in a reduction of sulfur content by 9.0–17.4%, a decrease in viscosity by 11.4–11.7%, and a lowering of the heavy oil fraction by 6.8–8.3%. Additionally, there was an increment in the production of gases by 0.2–0.3% and an increase in the fraction of hydrocarbons with a carbon number of less than < C20 by 5.4–8.2%. The best upgrading performance was observed during catalytic aquathermolysis at 300 °C. Overall, the findings underscore the synthesized Ni-based catalyst’s potential to significantly enhance the in situ hydrothermal upgrading process of extra-heavy crude oil, offering a promising approach for the treatment of such challenging feedstocks.
This study aimed to evaluate the performance and effectiveness of two water-soluble transition metal salts, nickel acetate and iron oxalate, in upgrading extra-heavy crude oil from Cuba. The ...experiment involved treating Cuba oil with water and each catalyst in an autoclave reactor under reservoir conditions for 24 h at 300 °C. Various analyses were conducted to assess the catalyst performance in reducing the viscosity of the crude oil, including gas chromatography (GC) of evolved gases, viscosity, and SARA analysis, elemental analysis, and GC analysis of saturated hydrocarbons. The results showed that both catalysts were able to significantly reduce the Cuba oil’s viscosity, with nickel acetate exhibiting a higher reduction of 80% from 16 420 to 3630 mPa·S, compared to iron oxalate, which showed a reduction of 69% from 16 420 to 5200 mPa·S. A significant decrease in asphaltenes was observed after the upgrading process with nickel acetate, with the content decreasing from 20.86 to 12.85%. Furthermore, the study conducted transformation analyses on the catalysts, both before and after the upgrading process, utilizing TG-FTIR analysis, XRD analysis, Mössbauer studies, and SEM-EDX analysis. These analyses revealed that nickel acetate had the advantage of desulfurization through hydrodesulfurization reactions, indicating its capability of reducing the sulfur content of the oil. The SEM-EDX results showed that the sulfur content formed on the nickel metal after the reaction was 16.21%, while the sulfur content formed on the surface of the iron metal constituted only 2.33%. The XRD results also showed large quantities of α-NiS, β-NiS, and Ni3S4 crystals formed after the reaction, in contrast to iron oxalate, which after the reaction formed large quantities of Fe3O4 (magnetite). This finding underscores the importance of nickel acetate in achieving the objectives of the upgrading process. In summary, the study highlights the potential of water-soluble catalysts, such as nickel acetate and iron oxalate, in upgrading heavy crude oil and reducing its viscosity. Moreover, the study emphasizes the importance of understanding the properties of the catalysts and their transformations during the upgrading process.
