Study On FeMo Hydrodesulfurization Catalyst For The Coke Oven Gas

Coke oven gas is of great value to the resources because of contains a lot of H2 and CH4. Coke oven gas desulfurization is a major problem on its recycling process, Hydrotreating process and FeMo/Al2O3 hydrodesulfurization(HDS) catalyst is widely applied for coke oven gas desulfurization in industry, but alumina-supported FeMo catalyst has low HDS activity and required to improve.In this paper, FeMo/Al2O3 catalysts with different Fe, Mo loading and preparation method were evaluated in the HDS reaction of thiophene, active phase structure of catalyst was analyzed, the HDS reaction mechanism of catalyst was discussed. First transition metals or composite support were introduced to improve HDS activity of FeMo catalyst, the doping and support modification effect mechanism was also discussed.1.First, HDS activity of different MoO3 loading, Fe/Mo atomic molar ratio catalysts prepared by mix-kneading method was measured, active phase structure of catalyst was analyzed. The results showed that Mo is the main active component, the HDS activity is higher with the increasing of the dispersion of Mo on the support surface, synergistic effect between Fe and Mo can enhance the HDS activity of catalyst. The catalyst with Fe/Mo=0.6 display the highest activity, thiophene conversion rate was 38.6% when the reaction temperature is 350℃.2.With optimum Fe/Mo proportion, HDS activity of catalysts prepared by impregnation, mix-kneading and coprecipitation method was compared, the impregnation method has more advantage, thiophene conversion rate of catalyst made by two-step impregnation (first dipping Fe) was 55.1% at 350℃. XRD analysis showed that impregnation method and added citric acid to impregnating solution improved the dispersion of active components.3.Catalysts doped with first transition metals showed different HDS activity, Mn, Zn, Co, Ni can improved the HDS activity of FeMo/γ-Al2O3 catalyst, but V, Cr, Cu doped decreased catalytic activity. the roles of Mn, Zn play in the desulfurization reaction may be adsorption of H2S, thus promoted chemical equilibrium shift of the thiophene hydrogenation reaction, while Co as the promoter of Mo catalyst, strong synergistic effect among them increase the HDS activity much more. On the other hand, the XRD result of sulfide catalysts suggested that Co doped promoted FeS transform to FeS2, which has better hydrogenation activity.4. Performance and effect mechanism of FeMo catalyst with modified support was studied, the results showed that FeMo/MgO-A2O3 has a poor performance in activity evaluation, the charaeterization of IR and XRD suggested MgO increased support basicity, enhanced formation of MgMoO4. SiO2 and TiO2 modified FeMo catalyst improve the HDS activity more or less, because they increased acid sites of support surface, weaken the effect between Mo and support, improved the surface dispersion of Mo, FeS2 phase was observed in the sulfide catalysts.5.Catalytic performance in simulated coke oven gas was investigated. under, the organic sulfur conversion rate of Fe-CoMo/TiO2-Al2O3 catalyst is higher than 99.9% at 350℃, thiophene content in the tail gas is less than 0.02 mg/m3, but Co doped catalyst increased the activity of methanation also, the methanation content in the tail gas rose to 0.87%.