Viscosity reduction of heavy oil based on rice husk char-based nanocatalysts of NiO/Fe2O3

In recent years, catalytic hydrothermal cracking has gained significant attention as an effective technology for reducing the viscosity of heavy oil in the field of heavy oil recovery. However, the current catalyst temperature window is relatively high, leading to high energy consumption in heavy oil extraction. The development of catalysts that can effectively reduce the viscosity of heavy oil at low temperatures is important to reduce energy consumption in the thermal recovery process of heavy oil. Biochar-based catalysts exhibit good low-temperature activity. Therefore, this study used modified rice husk char as a carrier to develop NiO-RHC, Fe₂O₃-RHC, and NiO/Fe₂O₃-RHC catalysts, and investigated their performance in low-temperature catalytic viscosity reduction. Various methods were used to characterize the physical and chemical properties of the catalysts, and the effects of catalyst type and addition amounts on the catalytic viscosity reduction reaction were examined. The results showed that the catalytic performance of the dual-active component catalyst was better than that of NiO-RHC and Fe₂O₃-RHC. Under the catalysis of NiO/Fe₂O₃-RHC, the viscosity of heavy oil decreased by 81.81 %. As the catalyst addition amounts increased, the viscosity reduction rate of heavy oil also increased. The optimal catalyst addition amount was 1.00 wt%, and the heavy component content in the oil sample was reduced by 4.14 % after the catalytic reaction. Finally, the mechanism of heavy oil viscosity reduction was analyzed. It was found that the breaking of C-S bonds was a significant factor in reducing heavy oil viscosity, and the S in H₂S mainly came from thioether and sulfoxide sulfur. This study provides valuable references for further research on low-temperature viscosity reduction in heavy oil.