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Synthesis and Evaluation of A Catalyst for Selective Oxidation of H2S to Elemental Sulfur as A Desulfurization Method for Gaseous Streams

Alemi, Faezeh | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56126 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Hamzehlouyan, Tayebeh; Rashidi, Alimorad; Zamani, Yahya
  7. Abstract:
  8. The selective oxidation of H2S into elemental sulfur is a complementary desulfurization method for reducing H2S emissions from gas streams. Several studies have been conducted in recent years to develop active, selective, and stable catalysts. The purpose of this research is to develop a catalyst with high activity and selectivity that is suitable for the gas output of one of the country's refineries. For this purpose, three supports of mixed metal oxide (solid solution), Ce-Al, Ce-Si, and Ce-Zr with a molar ratio of 1:2 (ceria: metal) were made by the co-precipitation method. In the following, three samples named 10V-CeAl, 10V-CeSi, and 10V-CeZr were prepared by impregnating 10% wt vanadium by the two-stage incipient wetness impregnation method. The properties of the catalyst and the formation of the active phase of vanadium on the support was investigated. Characterization tests including XRD, BET, XRF, H2-TPR, FESEM, ICP-OES, EDX, and elemental mapping were performed to evaluate the physical and chemical properties of the samples. Then the performance of the catalysts was evaluated in a fixed bed reactor under atmospheric pressure at 12 different temperatures. The feed compostion included H2S 0.66 % vol., O2 0.33 % vol., CO 16.4 % vol., H2 1.33 % vol., CO2 51.84 % vol., and N2 41.66 % vol.. Performance results show that the 10V-CeAl catalyst was able to achieve the best sulfur yield (i.e. 100%) among other catalysts at low temperature (i.e. 140℃). This performance is due to the strong interaction of vanadium metal with Ce-Al support and the formation of CeVO4 species on the surface, which increases the oxygen vacancies, improves the redox property and ability of oxygen mobility in the lattice and on the surface. The selectivity for all three catalysts is almost above 95%. For all the three catalysts, conversion at high temperatures shows a decreasing trend, which can be due to the presence of other reactants in the feed gas and the progress of side reactions competing with H2S oxidation. Finally, the apparent activation energy of the reaction was obtained according to the Arrhenius correlation and showed that the 10V-CeAl sample, represetnting the highest conversion and selectivity at lower temperatures, has the lowest activation energy. The low values of the apparent activation energy suggested that intra and extra-particle mass transfer limitations (due to low space velocity) could affect the oxidation process
  9. Keywords:
  10. Apparent Activation Energy ; Promoter ; Selective Oxidation ; Mixed Metal Oxide ; Desulfurizing

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