Cleaner recycling of spent Ni–Mo/γ-Al2O3 catalyst based on mineral phase reconstruction

Abstract

Hydrotreating catalysts are intensively used in petrol refining industry. Recovery of valuable metals from spent hydrotreating catalysts are essential due to the need for both environmental protection and natural resource saving. In this study, a spent catalyst recycling process featured by a mineral phase reconstruction conducted under inert/reductive atmosphere was proposed. In this process, soda roasting of Al2O3, carbothermic reduction of NiO, and carburization of MoO3 and V2O5, were performed simultaneously. The valuable metal elements (Al, Ni, Mo and V) were converted into alkaline-soluble NaAlO2, acid-soluble metallic Ni, and acid-alkaline-resistant carbides (Mo2C and V8C7), respectively. In the consequent steps, more than 98% of Al was selectively dissolved into leaching solution by NaOH solution under room temperature. Then, 0.5 mol/L H2SO4 solution was introduced to separate Ni from residues, obtaining an enriched Ni solution and undissolved Mo & V concentrated residue. Compared with traditional processes for spent hydrotreating catalysts, valuable metals are stepwisely extracted with much higher efficiency and selectivity due to the introduction of mineral phase reconstruction approach. This work offers a novel, clean and sustainable approach for recycling of spent hydrotreating catalysts.