Vol.1 No.3 2009

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Research paper : Development of highly-active hydrodesulfurization catalyst for sulfur-free diesel production (Y. Yoshimura et al.)−165 Synthesiology - English edition Vol.1 No.3 (2009) research was confirmed to be correct. Through the joint research, we were able to directly learn the requirements for industrial production of catalysts and address them from an academic perspective at AIST. This is probably the foremost reason why it was possible to scale up from the laboratory scale relatively easily. 5 Research Results5.1 Performance of the Developed CatalystThe hydrodesulfurization performance of the NiMo/Al2O3 catalyst developed by AIST was evaluated under the normal hydrodesulfurization conditions of a refinery (reaction temperature: 340 °C, reaction pressure: 4.9 MPa, LHSV: 1.5 h-1, H2/Oil feed ratio: 250 Nl/l) using a high-pressure continuous-flow reactor. The evaluation showed that sulfur-free diesel (S < 10 ppm, N < 1 ppm) can be produced from straight-run gas oil (S: 1.11 wt%, N: 105 ppm). 5.2 Structural Characteristics of the Developed CatalystFigure 8 shows a TEM image of the developed NiMo/Al2O3 catalyst (sulfide). The average layer length of MoS2 particles is about 4.4 nm and the average number of stacked layers is about 1.7. The MoS2 particles observed by TEM have a smaller basal plane length than a conventional NiMo catalyst and are highly dispersed. The number of stacked layers of MoS2 particles is smaller than in the conventional NiMo catalyst. Thus, it was confirmed that as initially intended, MoS2 particles on the -Al2O3 support were highly dispersed and supported in a lower stacking of layers.Atomic-level analysis of the MoS2 phase was conducted through extended X-ray absorption fine structure (EXAFS) analysis of the developed NiMo/Al2O3 (sulfide). Figure 9 shows a Fourier transform of the Mo K-edge EXAFS spectra for the conventional NiMo/Al2O3 catalyst (conv.) and the developed NiMo/Al2O3 catalyst (lab.). The table at top right shows the coordination number, N, of the sulfur atom around the Mo atom of each catalyst and the interatomic distance, R, of the Mo-S bond, as well as the coordination number, N, of the Mo atom around the Mo atom and the interatomic distance, R, of the Mo-Mo bond, which were obtained by the curve-fitting method. In both catalysts, the interatomic distance of the Mo-S and Mo-Mo bonds was 2.41 and 3.17 Å, respectively, and comparable MoS2 nanostructures were obtained. In the developed catalyst, however, the coordination number of the Mo-Mo and Mo-S bonds increased. The increase in the former suggests an increased size of the highly crystallized domain in the (002) face of MoS2. The increase in the latter suggests that the unit cell of MoS2 is closer to the cell structure of single crystals. The TEM image in Fig. 8 shows that MoS2 particles have a smaller basal plane size in the developed catalyst than in the conventional catalyst. These findings suggest very high crystallinity (nanocrystal state) of the MoS2 sheet in the developed NiMo/Al2O3 (sulfide), despite the smaller MoS2 basal plane size. From the above, it was confirmed that as initially intended, MoS2 particles on the -Al2O3 support existed in a highly crystalline state.5.3 Performance of a New Desulfurization Catalyst, LX-NC1 A new hydrodesulfurization catalyst (product name: LX-NC1) was developed by the catalyst manufacturer, with the design concept of improving the functionality of the nanocrystal structure of this low-stacked-layer MoS2. Figure 10 [9] shows the performance of the developed LX-NC1 NiMo hydrodesulfurization catalyst. In order to produce sulfur-free diesel using existing facilities in refineries, a highly active catalyst with a reaction temperature about 10 °C lower is required rather than a hydrodesulfurization catalyst for producing diesel with a sulfur content below 50 ppm; e.g., CDS-LX6 hydrodesulfurization catalyst, produced by the joint research partner. It was confirmed that the developed LX-NC1 catalyst exhibits high activity at a reaction temperature nearly 17 °C lower, and that sulfur-free diesel can be easily produced.(11)−Fig. 8 TEM image of the developed NiMo/Al2O3 catalyst (sulfide) and dispersed state of MoS2 particles.Fig. 9 Local structure of MoS2 particles on the developed NiMo/Al2O3 catalyst.Fractions (% / nm)Fractions (% / number)

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