FUEL 194 |
| Over the last few years, global ultra low sulfur diesel or gasoline regulations have induced a marked improvement in fuel transportation quality, it is expected that this trend continues until reaching sulfur level in the order of wppb (part per billion in weight). Such near zero sulfur emission legislation requires a high efficiency of the hydro(desulphurization) technology particularly for upgrading of heavy oils and residua. In order to achieve this goal a better understanding of the Ni and/or Co promoter effect on Mo and/or W is strongly required. Trimetallic (NiCoMo and NiCoW) and bimetallic (NiMo, NiW and CoMo) HDS catalyst precursors were prepared by urea-matrix combustion method. The oxidic and sulfided states of the HDS catalysts were characterized by laser Raman spectroscopy (LRS) and high resolution transmission electron microscopy (HRTEM). Catalyst performance was evaluated using a tubular fixed-bed reactor and the hydrodesulfurization of thiophene under normal pressure as model reaction. The addition of Co (or Ni) on Mo (or W) strongly improved the HDS behavior. However, the addition of Co-Ni on Mo and/or W hindered the HDS performance. This latter effect is attributed to the formation of Ni-Co-S rather than Ni(Co)-Mo(W)-S phase. Urea-matrix combustion method facilitates the formation of well-dispersed oxidic precursors on the alumina surface. This is reflected in a strong synergistic effect that markedly increases the C-S bond cleavage reaction whereas a less pronounced antagonistic effect affects the relative rate of hydrogen transfer reactions |
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Ultraclean Transportation Fuels
8:25 AM-12:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Rm. 238, Oral
Division of Fuel Chemistry |