Recovery and Resource Utilization of Spent Hydrogenation Catalysts: A Review

In consequence of the escalating utilization of hydrogenation catalysts in petroleum, one of the world's three primary energy sources, there has been a concomitant increase in the quantity of deactivated spent catalysts. As a hazardous waste material that poses a threat to human health and environmental safety, the recovery of valuable metals from these catalysts presents an environmentally friendly approach that aligns with the principles of a circular economy. The present study focuses on the efficient utilization of spent hydrogenation catalysts. To this end, it summarizes pretreatment processes, leaching methods, separation and purification techniques, and high-value-added utilization strategies. By evaluating the recovery principles and efficiencies of various methods within each process, the advantages and disadvantages of different approaches are delineated. It is evident that solvent extraction demonstrates considerable promise in the context of pretreatment processes, owing to its simplicity, high efficiency in oil removal, and recyclability. The roasting-leaching method has been shown to achieve higher leaching rates during the leaching process. In the domains of separation and purification, solvent extraction offers distinct advantages, including its high selectivity and mild operating conditions. In comparison with metallurgical methods, the regeneration and reuse processes in high-value-added utilization are shorter and more economically beneficial, particularly when utilizing spent catalysts as raw materials for the production. This approach achieves a balance between economic and environmental considerations, although it should be noted that the technology is not yet fully mature. In addition to the aforementioned points, this paper proposes targeted strategies for the challenges faced in the recycling of spent hydrogenation catalysts. The aim of this paper is to provide a reference for the industrialization of spent catalyst recycling.