焙烧温度对Fe-Mn催化剂结构和F-T合成性能影响

The effects of calcination temperature on the textural properties, reduction behavior and structural change during reduction and reaction of the Fe-Mn Fischer-Tropsch synthesis catalyst were studied. The F-T performances of the catalysts calcinated at different temperatures were investigated in a fixed-bed reactor under the conditions of H2/CO=2.0, 260 oC, 2.5 MPa and 1000h-1. The results of XRD and TPR indicated that the increase of calcination temperature could increase the crystallite size of α-Fe2O3 and decrease the specific surface area of the catalysts. Mn3+ ion gradually incorporates into the crystal lattice of α-Fe2O3, and the reduction peak of α-Mn2O3 completely disappeares at 700 oC. This incorporation results in the formation of the stable Fe2O3-Mn2O3 solid solution phase, which restrains the reduction of the catalyst. It is found that the catalysts with different calcination temperatures show high initial activity, while the increase of calcination temperature could improve the stability of F-T activity and shift hydrocarbon products to higher molecular weight. The catalyst calcinated at 600 oC shows relatively higher F-T activity and stability during the whole 200 h on stream of F-T run, which also gives the reasonable distribution of hydrocarbon and high selectivity of olefin and middle distilled cut.