Alumina from reprocessing of spent hydroprocessing catalyst

Spent hydroprocessing catalysts that are discarded as solid wastes from the petroleum refining industries contain high concentrations of valuable metals (e.g. Mo, V, Ni, Co) and Al₂O₃. Increasing emphasis has been placed in recent years on developing processes for their recycling and utilization. In the present work, experiments were designed and conducted to extract >99% of all valuable metals as well as to recover the alumina present in the spent catalyst in the form of high purity boehmite. Caustic digestion and hydrothermal treatment methods were used to recover alumina in the form of boehmite as well as to modify its textural properties. γ-Al ₂O₃ was prepared from the boehmite by heating at 500 °C. Factors controlling the textural properties of boehmite and γ-Al₂O₃ derived from the recovered boehmite were also investigated as part of the study. The treated samples were characterized by X-ray diffraction, surface area, pore volume, and pore size distribution measurements. Both boehmite and γ-Al₂O₃ with desirable textural properties (i.e. surface area >200 m²/g; pore volume >0.7 ml/g; mean pore diameter 100-120 ) suitable for use as catalyst support were obtained by optimizing boehmite hydrothermal treatment conditions.