Kinetic Study on Catalysis and Coordination Bonding of Cu Atoms in the Heavy Oil Aquathermolysis Catalyzed by CuSO₄ and CuSO₄/NaOH

The coordination bonding between Cu2+ and heteroatoms of heavy oil caused the viscosity increase during the upgrading reaction using CuSO4 as a catalyst. The previous work has proved that NaOH can inhibit coordination interaction to enhance the catalytic upgrading of CuSO4. This work developed a reaction kinetic model to describe the conversion of saturates, aromatics, resins, and asphaltenes (SARA) components and the migration of Cu atoms in heavy oil when CuSO4 and CuSO4/NaOH were used as catalysts. This model quantitatively characterizes the viscosity-increasing effect resulting from Cu2+ entering heavy oil and the catalytic effect, enabling an analysis of the impacts of reaction temperature and CuSO4 concentration. As the reaction temperature increased from 200 to 300 °C, the viscosity-increasing and catalytic effects were enhanced. Additionally, when CuSO4 concentration rose from 1.25 to 10 wt %, the viscosity-increasing effect strengthened, while the catalytic effect diminished. Compared with CuSO4, the addition of NaOH reduced the viscosity-increasing effect and enhanced the catalytic effect. These findings provide valuable insights into the mechanism of heavy oil catalytic upgrading and support the broader application of transition metal inorganic salt/alkali composite catalysts.