Selective recovery of Mo, Co and Al from spent Co/Mo/γ -Al₂O₃ catalyst: Effect of calcination temperature

Abstract

A combination of pyro and hydrometallurgical process has been proposed to selectively recover molubdenum, cobalt and aluminium from the spent catalyst containing 12.3% Mo; 31.8% Al; 2.38% Co; 9.5% S and 2.9% C. Before a two-stage alkali-acid leaching process to selectively target Mo, Co and Al from the uncrushed sample, the spent catalyst was calcined at different temperatures. Characterization of different calcined samples was carried out by different instrumental analysis like XRD, TG/DTA, IR and SEM in order to understand the structural changes and dissolution behavior of spent catalyst. It was found that calcination at 500°C preferred for spent catalyst roasting since the surface and pore structures obtained by roasting at this temperature facilitated dissolution of calcined spent catalyst in the leachant. Mo was selectively separated and recovered from the leach liquor by carbon adsorption method; whereas, Al and Co were separated by an organo-phosphinic-based extractant, Cyanex 272. In the whole process, 95.9% Mo, 89.6% Co and 39.8% Al was recovered from the spent catalyst. Finally, a complete process flowsheet has been presented.

Keywords:

• Spent catalyst
• calcination
• Na₂CO₃/H₂SO₄ leaching
• activated carbon adsorption
• Cyanex 272.

Acknowledgment

One of the authors, Debasish Mohapatra wish to thank the Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon for the award of a Post-Doctoral Fellowship and financial support.