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Synthesis of MoS2 Nanoparticles and Their Application as Nanocatalyst for Hydrodesulfurization Process

Parviz, Dorsa | 2008

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39102 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Kazemeini, Mohammad; Rashidi, Alimorad
  7. Abstract:
  8. Highly active unsupported MoO3 and (Co) MoO3 catalysts were synthesized utilizing the solution combustion method where the Ammonium molybdate powder and an organic additive were used as precursors. Different organic materials including Ethylene Diamin Tetra-acetic acid (EDTA), Polyethylene Glycol 200 (PEG 200), Sorbitol and Urea were used as additive in order to investigate the effect of additive structure on morphology and particle size of products. Also various reaction parameters such as the additive/Mo molar ratio, concentration of metal ion in solution, pH of the reaction and temperature of the synthesis media were changed to study effects on product morphology and size. Outcomes were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction and Transmission Electron Microscopy (TEM) techniques. Results suggested that utilizing each additive produce a particular morphology of MoO3.various products including MoO3 nanoparticles, nanorods, microrods and microsheets may be obtained through this method whose length varies from a few nanometers to several microns. Addition of cobalt promoter decreased the surface area and increased the pore size of catalysts. Also XRD and TEM results showed that crystal growth was restricted after cobalt incorporation. The catalytic activity of samples was evaluated in hydrodesulfurizaton reaction of naphta. The product was analyzed by XRF to determine the sulfur content of feed after reaction. Nanostructure and promoted catalysts had higher activity than microstructure samples. Optimizing the reaction condition was found to produce more active molybdenum oxide nanoparticles using urea and PEG200. The conversion over the samples prepared by urea and PEG200 was more than CoMo/Al2O3 commercial catalyst. The reaction over urea-prepared promoted catalyst decreased the sulfur content of naphta to 24 ppm which is considerably lower than sulfur content of commercial catalyst product. Single wall carbon nanotubes were used to produce CoMo/CNT supported catalysts. Urea, PEG200 and EDTA were used as chelating agents in order to reduce the particle size of MoO3 and increase the dispersion of active site on the surface of CNT support. A considerable increase in surface area was observed for supported catalysts. These supported catalysts had higher activity than unsupported microstructure MoO3 catalysts. But they showed lower activity than unsupported nanostructure and promoted catalysts. This result substantiate that high activity of unsupported nanostructure catalysts is not only due to the presence of more active metal in catalysts structure, but it is a consequence of optimizing the synthesis condition and particle size reduction. All CoMo/CNT catalysts had higher activities than commercial catalysts. It was concluded that carbon nanotubes have superior performance as catalyst support in comparison with alumina
  9. Keywords:
  10. Molybdenum Oxide ; Carbon Nanotubes ; Nanoparticles ; Hydrodesulfurization ; Nano Catalyst ; Promoter

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