Recent advances in the recovery of transition metals from spent hydrodesulfurization catalysts

Hydrodesulfurization (HDS) catalysts are widely used in petrochemical industries, playing a crucial role in desulfurization process to get high-quality oil. The generation of Al-based spent HDS catalyst is estimated to be 1.2×105 tons per year around the world. The spent HDS catalysts have been regarded as an important secondary resource due to their abundant output, considerable metal value, and regeneration potential; however, if improperly handled, it would severely pollute the environment due to high content of heavy metals. Thus, the recovery of valuable metals from spent HDS catalysts is of great importance from both resource utilization and environmental protection points of view. In this work, recent advances in the spent HDS catalyst treatment technologies have been reviewed, focusing on the recovery of valuable transition metals and environmental impacts. Finally, typical commercial processes have been discussed, providing in-depth information for peer researchers to facilitate their future research work in designing more effective and environmentally friendly recycling processes.