Efficient recovery of nickel from spent FCC catalysts by sulfation roasting-leaching

The combination of pyrometallurgical and hydrometallurgical nickel recovery processes has been proposed, performing sulfation roasting on spent FCC catalysts, followed by leaching and precipitating to obtain an enriched crude nickel compound. The results show that the nickel in spent FCC catalysts can be converted and recycled in mild conditions compared with conventional high temperature reduction (over 800 °C) and processes. Under the optimal process conditions: add 98 % concentrated sulfuric acid at a solid-liquid ratio of 1:1, roast at 450 °C for 30 min, and leach in water at 90 °C for 60 min, repeat the water leaching process once the leaching rate of nickel can reach 99.99 %. After preliminary impurity removal, nickel is recovered in the form of Ni(OH)₂, the content of nickel in the crude product obtained is 24.99 %, which is 19 times higher than that of spent FCC catalyst raw materials, the overall nickel recovery rate reaches over 99 % with negligible losses, achieving the preliminary concentration and recovery of nickel in the spent FCC catalyst. Theoretical calculations and analysis were conducted on the kinetics and thermodynamics involved in the sulfation roasting-leaching process, which is consistent with the results above.