Recovery and regeneration of Al₂O₃ with a high specific surface area from spent hydrodesulfurization catalyst CoMo/Al₂O₃

Aluminum recovery is a key issue for the overall recycling of valuable metals from spent catalysts. This paper focuses on the recovery and regeneration of alumina with high additional value from the spent hydrodesulfurization catalyst CoMo/Al₂O₃. The results indicate that 98.13% alumina is successfully leached from the treated spent catalysts by an alkaline leaching process under the conditions of 5 mol·L⁻¹ sodium hydroxide, a liquid/solid ratio of 20 ml·g⁻¹, a temperature of 160 °C and a reaction time of 4 h. In the leaching residue, no difficult leaching compound is found and cobalt and nickel are enriched, both of which are conducive to the subsequent metal recovery step. The reaction order of aluminum leaching is 0.99. This reaction fits well with the interfacial chemical reaction model, and its apparent activation energy is calculated as 45.50 kJ·mol⁻¹. Subsequently, γ-Al₂O₃ with a high specific surface area of 278.3 m²·g⁻¹, a mean size of 2.2 μm and an average pore size of 3.10 nm is then regenerated from the lixivium, indicating its suitability for use as a catalyst carrier. The recovery and regeneration of alumina from spent catalysts can not only significantly contribute to the total recycling of such hazardous spent catalysts but also provide a new approach for the preparation of γ-Al₂O₃ with a high specific surface area using spent catalysts as the aluminum sources.