Study on catalytic aquathermolysis of heavy oil by simple synthesis of highly dispersed nickel-loaded nitrogen-doped carbon catalysts

•Highly dispersed Ni/NC catalysts with different Ni content were synthesized by one-pot method.•The Ni/NC-6.0 catalyst showed the most excellent catalytic performance on the viscosity reduction and upgrading of heavy oil.•The catalysts contributed to the breakage of the long side chains of resins and the reduction of the degree of asphaltenes branching. Faced with the increasing energy demand, the extraction of heavy oil is crucial. Efficient catalysts can reduce the viscosity and improve the quality of heavy oil. In this paper, the highly dispersed Ni/NC-6.0 catalyst was prepared by one-pot method and was utilized for the viscosity reduction and upgrading of heavy oil. The results of H2-TPD, SEM, TEM, and XPS demonstrate that the average size of Ni/NC-6.0 is about 200 nm, and the Ni atoms coordinated with N atoms are highly dispersed over the surface of carbon support. The experimental results of catalytic aquathermolysis reveal that highly dispersed Ni/NC-6.0 catalyst showed efficient catalytic performance in reducing the degree of asphaltenes branching and cracking the long chains of resin. It can reduce the viscosity by 82.21% and decrease the heavy components by 13.04% through the occurrence of hydrodesulfurization, hydrodenitrogenation, debranching, dealkylation of long-chain, depolymerization, and cracking. This work makes contributions to viscosity reduction and upgrading of heavy oil. [Display omitted]