Spent nickel–molybdenum–vanadium (Ni–Mo–V) sulfide catalysts are widely used in hydrotreating, hydrodesulfurization and residue-upgrading units across the global refining industry, producing large volumes of solid residues that are both hazardous waste and valuable secondary resources rich in strategic metals. The presence of sulfides, coke deposits, and toxic trace elements poses significant environmental and health risks if improperly managed, while conventional disposal or partial treatment often results in the irreversible loss of nickel, molybdenum, vanadium, and sulfur. This critical review examines current and emerging technologies for the recovery and recycling of spent Ni–Mo–V catalysts, covering pyrometallurgical, hydrometallurgical and hybrid processing routes, with particular emphasis on selective metal extraction and process integration. Special attention is given to sulfur management, which is often treated as an emission-control issue rather than as a recoverable resource, highlighting opportunities for elemental sulfur recovery through controlled oxidation, Claus-based systems and wet oxidation processes. Key technological limitations related to selectivity, emission control, process scalability and economic viability are identified, and the role of spent Ni–Mo–V catalyst recycling within circular-economy frameworks is critically assessed, emphasizing regulatory drivers and future research directions required to enable fully integrated and sustainable resource recovery strategies.
Ph.D. Antonio Clareti Pereira (Sat,) studied this question.