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Regeneration of Cobalt from Catalyst Deactivated in Fischer-Tropsch Synthesis

Ahmadi, Ali Akbar | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40306 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Kazemeini, Mohammad; Rohani, Ali Asghar
  7. Abstract:
  8. In this work hydrometallurgical route for processing spent commercial catalysts (Co/Al2O3) are investigated for leaching the Cobalt component. The used catalysts were initially pre-oxidized at 500 °C and 5 h in order to eliminate coke and other volatile species present. Pre-oxidized catalysts were dissolved in solvents such as H2SO4, HNO3, HCl and H2O at 80-90 °C, and the remaining residues separated from the solution. These experiments were performed at different concentrations, presence and absence H2O2 solution. Also effect of reflux on leaching process investigated. The result show the yield of the pre-oxidized catalysts extracted with highly concentration of extractant is higher than non pre-oxidation catalysts and also H2O2 is not effective matter for leaching the cobalt. The reflux system is necessary for avoid from volatile solvent and for environmental and economical aspects. All result showed that H2SO4 is suitable solution for cobalt leaching from the used catalyst in commercial and economical aspects. Effect of leaching conditions such as concentration of extractant, leaching temperature and leaching time are investigated. With plot diagrams of quantity of cobalt extracted as a function of temperature and time leaching and concentration of extractant, best conditions of cobalt leaching was determined. Then, cobalt ions was precipitated by NaOH, Na2S, Na2CO3, (NH4)2CO3 and (NH4)2C2O4 in Co(OH)2, CoS, CoCO3 and CoC2O4 forms. Effect of temperature on precipitating process also was investigated. Used contents of each precipitator in each pH were given. In last, we obtained 97.86% cobalt extracted in leaching process and 97.84% cobalt precipitated in precipitating process in CoCO3 and CoS forms.
  9. Keywords:
  10. Fischer-Tropsch Synthesis ; Cobalt Catalyst ; Precipitation (Chemical) ; Leaching ; Extractant

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