Preparation of CoMo/Al₂O₃, CoMo/CeO₂, CoMo/TiO₂ catalysts using ultrasonic spray pyrolysis for the hydro-desulfurization of 4, 6-dimethyldibenzothiophene for fuel cell applications

One of promising methods for removing the sulfur compounds from diesel fuel is hydrodesulfurization, in which the sulfur in diesel is hydrotreated by reaction with H₂ to liberate H₂S. In hydrodesulfurization, a highly efficient catalyst is required fuel cell applications because the level of sulfur compounds should be below 0.1 ppm to allow stable molten carbonate fuel cell operation. In this study, we prepared the CoMo/Al₂O₃, CoMo/CeO₂, CoMo/TiO₂ catalysts using ultrasonic spray pyrolysis and the activities of synthesized catalysts toward the hydrodesulfurization of 4, 6-dimethyldibenzothiophene were examined using a flow reactor. First, our measurement results using X-ray diffraction, scanning electron microscope, field emission gun electron probe micro analyzer and transmission electron microscope suggested that the Co and Mo particles are uniformly distributed on the supports (Al₂O₃, CeO₂, and TiO₂) we considered. Second, from the analysis of surface properties using via Raman spectroscopy, we identified the characteristic phases (such as Ce₂Mo₃O₁₃, MoO₃, and CoMoO₄) of each synthesized catalyst, which may significantly influence hydrodesulfurization reactivity. Finally, the evaluation of catalytic activity showed that the order of hydrodesulfurization activity is CoMo/CeO₂ > CoMo/Al₂O₃ > CoMo/TiO₂. In particular, a CoMo/CeO₂ catalyst exhibits the highest catalytic activity toward hydrodesulfurization, reducing the amount of 4, 6-dimethyldibenzothiophene from 10 ppm to about 0.1 ppm at 350 °C.