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-Al2O3 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 Å) suitable for use as catalyst support were obtained by optimizing boehmite hydrothermal treatment conditions.

In the present study, both boehmite and γ-Al2O3 were obtained by reprocessing spent hydroprocessing catalysts and their textural properties were modified by hydrothermal treatment to obtain large surface area (>200 m2/g), pore volume (>0.7 ml/g), and desirable pore size distribution. The effect of hydrothermal treatment temperature on the total pore volume and pore size distribution of the recovered boehmite sample is presented graphically.Figure optionsDownload high-quality image (208 K)Download as PowerPoint slideHighlights
► Process for total recycling of spent hydroprocessing catalyst.
► Reclamation of all valuable metals (V, Mo and Ni) as high purity metal salts.
► A process for recovery of alumina as boehmite with controlled pore size from spent catalyst.