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Preparation of a Monolithic Nanocatalyst Utilizing Carbon Nanotubes for HDS Process

Soghrati, Elmira | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42875 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Kazemeini, Mohammad; Rashidi, Alimorad
  7. Abstract:
  8. Monolithic nanocatalysts for naphta hydrodesulfurization process have been prepared and evaluated. Commercial cordierite monolith was used as a ceramic substrate. Initially, the monoliths were pretreated with nitric acid solution in order to increase specific surface area. After that, carbon nanotubes were grown through catalytic decomposition of methane over prepared monoliths. Finally, the CNT-coated monoliths were oxidized with ozone and an aqueous solution of H2O2. For the preparation of HDS Co-Mo nanocatalysts, the metal content of aqueous solution including cobalt nitrate, ammonium heptamolybdate were then impregnated onto the prepared supports. Next, samples of prepared supports and nanocatalysts were characterized by the specific surface area measurements (BET), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), inductively coupled plasma mass spectrometry (ICP-MS) and Field Emission Scanning Electron Microscopy (FESEM) techniques and adhesion measurements. Finally, these synthesized nanocatalysts were evaluated in naphtha HDS reaction. For the preparation of Co-Mo-S active phases; the nanocatalysts were sulfided in the reactor. After this activation step, the catalytic performances were evaluated using naphtha cut with total sulfur content of 0.267wt% as feed. The sulfur content of products was analyzed by the X-Ray Fluorescence (XRF) technique. Results revealed that the CNTs-cordierite monolith was a stable and effective nanocatalyst support possessing desirable specific surface area, suitable pore-size distribution and good attachment of the CNTs onto the substrate. Moreover, a considerable increase in surface area was observed for pretreated monolithic support. CNT-coated cordierite monolithic nanocatalysts had higher activity than pretreated monolithic samples. The reaction over oxidized CNT supported catalyst with 10 wt% total active metals decreased the sulfur content of naphta to 13 ppm (99.53 %) which is considerably lower than sulfur content of other catalyst product. Ultimately, HDS monolithic nanocatalysts with the same significance as the powder nanocatalysts were successfully prepared. The effect of changing the temperature, operating pressure, liquid hour space velocity (LHSV) and loading of active metals on the activity was investigated
  9. Keywords:
  10. Carbon Nanotubes ; Hydrodesulfurization ; Monolithic Nanocatalyst

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