A Study on the Characterization of Hydrodesulfurization Catalysts by Magnetic Properties of Co toward the Development of Highly Active Catalysts

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The salient findings in this research project are as follows:1. The Co sulfide species in the Co-Mo-S phase show an antiferromagnetic behavior. The magnetic susceptibility of the Co atoms was simulated by a theoretical equation assuming the formation of Co dimmer clusters with Co-S-Co bonding, in conformity with the NO adsorption, which shows the maximum NO adsorption capacity is NO/Co = 1/1 molar ratio. The proposed Co-Mo-S structure was supported by our recent XAFS analysis of CVD-Co/MoS_2 catalysts.2. The addition of boron to Co-Mo/Al_2O_3 was studied to improve the hydrodesulfurization activity. It was found that the addition of boron increases the TOF by 1.6 times, indicating the ace reactions, accordingly resulting in weaker interactions between Mo oxides and Al_2O_3 surface. The dispersion of MoS_2 was decreased by the addition of boron because of ence in the dispersion of MoS2 particles.3. The intrinsic activity of the Co-Mo-S structure was increased by sulfiding at a high temperatur-Mo-S structure showed a much less activity because of strong Mo-O-Al bonding. However, the addition of boron decreased the sulfidation temperature for the formation of Type II. The thermal stability of the Co-Mo-S phase was decreased by the addition of boron.4. Highly dispersed Co sulfide clusters were successfully prepared in zeolite pores using Co(CO)_3NO as a precursor. The structure depended on the type of the host zeolite. It was found that Co sulfide clusters react with zeolite protons to form Co2+ cations liberating H_2S. The hydrodesulfurization activity of the Co_sulfide clusters depended on the structure and residual OH groups.5. It is proposed that highly active hydrotreating catalysts are prepared by synthesizing highly dispersed Co-Mo-S Type II by modifying the interactions between MoS_2 particles and support surface. Simultaneous use of boron and chelating agents will be very effective for the developments of highly active ultra-deep hydrodesulfurization catalysts.