焙烧温度对Fe-Mn催化剂结构和F-T合成性能影响

研究了焙烧温度对Fischer-Tropsch(F-T)合成Fe-Mn催化剂的织构性质、还原行为以及在还原和反应过程中结构变化的影响；在H2/CO=2.0、260 ℃、2.5 MPa和1 000 h－1条件下在固定床反应器上考察了焙烧温度对Fe-Mn催化剂F-T合成反应活性、烃产物选择性和运行稳定性的影响。XRD和TPR结果表明，随着焙烧温度的升高，催化剂中α-Fe2O3晶粒增大，催化剂比表面积降低，促进Mn3+渗入α-Fe2O3晶格中，形成了铁锰固溶体物相，使得催化剂难于还原，当焙烧温度升高到700 ℃时，催化剂中的α-Mn2O3相完全消失。催化剂F-T合成反应评价表明，在不降低催化剂活性的同时，焙烧温度的升高可显著地提高催化剂的反应运行稳定性，并促使烃产物分布向高碳数方向偏移；600 ℃焙烧的Fe-Mn催化剂运行200 h，总体活性高，失活速率较低，对低碳烯烃和中间馏分油段产物选择性好。

Effect of calcination temperature on the structure and Fischer-Tropsch performance of Fe-Mn catalyst

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.