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Characterization of V2O5 Spent Catalyst & Feasibility Study of its Regeneration

Soltani Nejad, Mohammad | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49650 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Sadrnezhaad, Khatiboleslam; Farzami, Faezeh
  7. Abstract:
  8. In this study, at first the V2O5 spent catalysts were characterized. The aim was to identifying whether these catalyst may be regenerated. Then, for feasibility study of them, three methods were applied: washing, diffusion and milling the spent catalysts for their subsequent reproduction. A variety of techniques such as XRD, XRF, AAS, TPR and TPO were applied in order to identify factors contributing in vanadium pentoxide catalysts deactivation. The results showed that approximately all of pollutants caused their performance deterioration, while they still have some active phases. Then, the polluted catalysts were washed (their yield increased from 43% to 72.2%). In the underside of the catalyst bed, the following compounds of Vanadium & Potassium had formed: NaV(SO4)2, Na3V(SO4)3, KV(SO4)2, CsV(SO4)2, Na2VO(SO4)2, Na3(VO)2(SO4)4, K4(VO)3(SO4)5, K3(VO)2(SO4)4, Cs2(VO)2(SO4)3, β-VOSO4 and VOSO4(SO2SO3)x . Thus, the concentration of active elements in the catalysts had decreased and catalysts had deactivated (yield 50.3%). The result of XRD tests on the upper catalysts revealed that the main element of catalyst had reacted with polluting substances. Oxidation and reduction intensity of the row materials by temperature programed reaction was as follows: Fresh catalyst > spent catalyst > V2O5 powder > Diatomaceous earth By washing, pollution in the surface of spent catalysts were removed and their yield was increased. H2SO4 is the best solution for removal of surface pollutants (Yeild: 71.1%). But the sample that was washed with H2O2 (10%) had the best yield (72.2%). Diffusion of vanadium and potassium to spent catalysts was a good procedure. So, vanadium and potassium substances diffused into the catalyst. Regeneration of the used catalysts by KOH adhesive agents, sulfuric acid and addition of vanadium pentoxide plus potassium hydroxide powders increased their activity up to 72.5%. It is also worth mentioning that the reactivity of catalysts which were regenerated from sintered ones increased to maximum yield of 72.4% by application of H2O2 adhesive agents and sulfuric acid in conjunction with addition of potassium hydroxide and vanadium pentoxide
  9. Keywords:
  10. Vanadium Pentoxide Catalyst ; Spent Catalyst ; Characterization ; Washing Process ; Milling ; Diffusion ; Feasibility Study

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