Recycling and recovery routes for spent hydroprocessing catalyst waste

This study investigates the recovery of Mo, V, and Ni metals from the industrial spent hydroprocessing catalyst. These catalysts are not viable to regenerate mainly due to the metal deposition. The study was carried out on industrial spent residue hydroprocessing (ARDS) catalysts that contained high levels of metals. In the extraction process, metals were recovered through pyrometallurgical and hydrometallurgical routes. The possibility of recycling of total spent catalyst (TSC) was studied using various steps such as deoiling, drying, grinding, sieving, and decoking. In the subsequent steps, the digested spent catalysts were treated with acid-base reactions in order to separate the various components of the spent catalyst. Using various leaching reaction conditions such as acid-base concentration, reaction pH in aqueous as well as organic mediums was studied. The metals were leached out in the solution while the alumina support was recovered as bulk solid in the form of boehmite. The recovered alumina is further treated hydrothermally and recovered as boehmite. Samples were characterized by surface area, pore volume, and pore size distribution measurements. Hence, recovery of valuable metals from the spent catalysts is an attractive option for their recycling and utilization. Therefore, TSC recovery is not only important from an environmental point of view but also very vital from an economic viewpoint.