Study Of Cobalt Catalysts For Controlling The Products Distribution Of Fischer-Tropsch Synthesis

Fischer-Tropsch synthesis (FTS) is a process which converts a mixture of carbon monoxide and hydrogen into hydrocarbons and oxy-compound. The synthesis gas derived from natural gas, coal and biomass can obtain clean energy by FTS, so this progress has attracted much attention due to the increased oil prices. Because of the Anderson-Schulz-Flory (ASF) products distribution of Fischer-Tropsch synthesis, the products of FTS have a wide molecular distribution and improving the selectivity of certain products become the key of FTS’s study. In this study, we prepared different Co/MnOx (Co/MnO、o/MnO2、Co/Mn2O3、Co/Mn3O4) catalysts to investigate the effects of MnOx supports on selectivity of light olefins (C2=～C4=). The various catalyst were characterized by XRD, SEM, TEM, BET, TPR, DRIFTS and XPS. The experiment conditions and Zr promoter on the selectivity of C2=～C4= for Co/Mn3O4 were also studied. On the other hand, a novel Mn/Co3O4 catalyst was studied for forming light olefins in FTS reaction.MnO、MnO2、Mn2O3、Mn3O4 were prepared and the corresponding cobalt catalysts were developed by impregnation method. The results show that Co/MnO and CO/Mn3O4 has a better activity for more homogenous cobalt partical distribution and higher reduction degree of catalyst, and Co/Mn2O3 and Co/Mn3O4 has better selectivity of C2=～C4=.Reduction temperature, reaction temperature and pressure for FTS were investigated. Reduction temperature of 350℃、reaction temperature of 240℃ and reaction pressure of 1MPa gave the optimal FTS reaction performance, and the CO conversion was 30.4% and the selectivity of C2=～C4= was 48.51% and O/P was 3.79 for Co/Mn3O4 catalyst.The Co/ZrO2/Mn3O4 catalysts prepared by stepwise impregnation method were studied for the effects of Zr promoter on FTS performance. The results indicated that Zr proved the reduction of Co species, weakened the interaction between Co-Mn, and reduced the activity of WGS. The best O/P of Co/ZrO2/Mn3O4 catalyst is 3.0 (Co/10ZrO2/Mn3O4), but selectivity of C2=～C4= is only 26.09%.Co3O4 nanoparticles were prepared by hydrothermal method and phase composition and microstructure were confirmed by XRD and SEM. The FTS performance suggests that with the increase of Mn content, the CO conversion and selectivity of CH4 is suppressed, but WGS activity and light olefin selectivity increase. Consequently, the O/P is as high as 3.74 and the selectivity of C2=～C4= reached 48.44% for 10Mn/Co3O4.