Influence Of The Preparation Method In The Catalytic Behavior For CO Hydrogenation

Fischer–Tropsch synthesis (FTS) has attracted increasing interest as an important route for indirect coal liquefaction.This dissertation investigated the influence of different preparation methods of cobalt and/or iron based catalysts for C1-C4 hydrocarbons synthesis, and SiO2,γ-Al2O3, AC and ZSM-5 zeolite (Si/Al =38) (20-40 mesh) were chosen as the supports, respectively. The characterizations as XRD, BET, SEM, and NH3-TPD were utilized to reveal the textural and structural properties, and the surface compositions of the catalysts etc.As Co-6Mn/SiO2 catalysts,the catalytic performance of the catalysts obtained by microwave were better than by conventional impregnation method while the reaction temperature was higher than 300 oC. The results of XRD, BET and SEM indicated that the dispersion of Co-based catalysts was enhanced with the existence of Mn promoters. At the same time, microwave irradiation leaded to an decrease in catalysts crystallize mean size, and an increase in active components dispersion as well as the formation of active centers.For the Fe/C catalysts prepared by microwave irradiation gave high C1-C4 yield under the temperatures of 360, 400 oC. The results of XRD and SEM indicated that the larger crystallite size of Fe3O4 formed in the Fe/C catalysts prepared from the decomposed Fe(CO)5 in the autoclave, and for the Fe/C catalysts prepared by microwave irradiation, it was found that a new phaseα-Fe2O3 formed may be attributed to high temperature in the preparation of the catalysts, while the surface area was larger and the crystallite size was small, which induce the activity increase for the Fe/C catalysts prepared by microwave irradiation.For the Co/?-Al2O3 catalysts, the catalysts prepared by microwave irridiation in the overall catalytic performence were superior to conventional catalyst prepared by impregnation. The results of XRD, BET and SEM indicated that the catalysts prepared by microwave irradiation leaded to a decrease in catalysts crystallize mean size, an increase in pore volume and mean pore diameter, which favored to the formation of C1-C4 hydrocarbons.For Co-Fe/ZSM-5 catalysts for CO hydrogenation, the Co-Fe/ZSM-5 catalysts prepared by microwave irridiation in the overall catalytic performence were also superior to the catalysts prepared by conventional impregnation. The results of XRD showed that iron exsited as amorpnous phase in Co-Fe/ZSM-5 catalysts. The results of BET showed that the surface area, pore volume and mean pore diameter of the catalysts prepared by microwave irradiation were lower than conventional impregnation. On the other hand, the NH3-TPD results indicated that a lower acidic amount to match the better catalytic performance.