Loading...

Synthesis and Evaluation of Carbon based Catalyst for HDS Process of Refinery Products

Hajjar, Zeinab | 2016

841 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 48325 (48)
  4. University: Sharif University of Technology
  5. Department: Institute for Nanoscience and Nanotechnology
  6. Advisor(s): Kazemini, Mohammad; Rashidi, Alimorad; Bazmi, Mansour
  7. Abstract:
  8. One of the most important world issues is environmental constraints regarding the pollutants released by transportation fuels and refinery products, sulfur reduction being one of the most significant objectives. Deep hydrodesulfurization processes result in great sulfur reduction in refinery streams. However, such harsh process conditions increase undesired side reactions and facilitate coke formation as well as affecting the surfaces. More effective alternatives for hard process conditions are highly active and selective hydrodesulfurization catalysts, which enable the process to be performed at milder pressure and reaction conditions. Catalyst bases play a very important role in hydrogen desulfurization process.industrial catalyst for hydrodesulfurization is alumina based catalyst. Thus, considering its unique properties, graphene was selected as the catalyst base in this work. Graphene was synthesized by chemical exfoliation process followed by loading of the metal active phase by impregnation and hydrothermal methods. D-optimal experimental design was performed by investigation of the parameters including total loaded metal, cobalt to molybdenum weight ratio, citric acid to molybdenum molar ratio and loading method (impregnation or hydrothermal). The catalysts prepared were evaluated in hydrogen desulfurization from naphtha feed. The optimum catalyst was selected and evaluated for moderating process conditions. Moderation of process conditions was carried out using neural network modeling by investigation of such parameters as temperature, pressure, LHSV, and hydrogen to feed ratio and the results indicate that graphene based catalysts are more effective and can give higher conversions under milder operating conditions, compared with commercial catalysts. Catalyst activities as a function of time were also studied. Graphene sheets were then synthesized by chemical vapor deposition method using camphor and methane stating materials, functionalized, and loaded with the active phases. These catalysts were evaluated in hydrodesulfurization of naphtha feed and were shown to be more active(98-100%) in comparison with alumina catalysts(conversion is about 92%). In the next step, a novel, single step method was developed for the synthesis of grapheme oxide based molybdenum catalysts, which exhibit unique properties such as high acidity and surface area, making the catalyst very highly active. Ultimately, spray pyrolysis method was applied for the first time in loading of the active phase in the synthesis of grapheme oxide based molybdenum catalysts, which were used in hydrodesulfurization of naphtha feed. HDS tests were carried out using gasoil feed under two operation conditions for further investigation. The results showed that considering the unique properties of graphene, it is an excellent base compared with alumina and carbon based catalysts. This catalyst base causes surface activity of active phases due to its high surface area and physico-chemical properties in addition to activation and transfer of hydrogen to reactant molecules given its carbon nature and improves hydrogen desulfurization activity. Ultimately, all the synthesized catalysts for further performance evaluation were tested in HDS of diesel. Results showed that the catalyst made by spray pyrolysis method is the most active catalyst and could reduce the total sulfur of the diesel feed to 3ppm.Characterizations of catalysts were carried out using Transmission Electron Microscope , Field Emission Scanning Electron Microscope , Raman spectrometer, ICP , powder X-ray diffraction , specific surface area measurement equipment as well as; TPR and TPD mesurments
  9. Keywords:
  10. Graphene ; Hydrodesulfurization ; Naphtha ; Gas oil ; Chemical Vapor Deposition (CVD) ; Graphene Oxide ; Chemical Exfoliation ; Cobalt-Molybdenum Graphene Based Nanocatalyst

 Digital Object List

 Bookmark

No TOC