用MES及XRD研究FT合成催化剂的活性结构

MES AND XRD STUDY OF CO-PRECIPITATED Fe/Mn CATALYSTS FOR FT SYNTHESIS

采用穆斯堡尔谱及Ｘ光衍射法研究了共沉淀法制备的不同Ｆｅ／Ｍｎ比催化剂在焙烧、合成气还原及ＦＴ反应后体相结构的变化。结果表明：锰助剂的加入使催化剂体相由铁磁性逐渐转化为超顺磁性，相应使催化剂还原逐渐变难，Ｍｎ助剂促进了ＦＴ合成反应进行。反应性能与Ｆｅ／Ｍｎ尖晶石（Ｆｅ（１－ｙ）Ｍｎｙ）_３Ｏ_４组成含量及式中ｙ大小密切相关，与ＭｎＣＯ_３及ＭｎＯ的存在也有一定关系。富铁催化剂中Ｍｎ主要起电子助剂作用，而富锰催化剂中Ｍｎ不仅起电子调变作用，还直接作为结构助剂，从而在ＦＴ反应中有更加不均匀和复杂的物相出现，进行着氧化、还原及碳化等多种反应的竞争。

The structure of Fe/Mn catalysts after calcination,reduction and FT synthesis were investigated by means of MES and XRD.With the increase of the Mn content,the iron phase of the catalysts gradually changed from magnetic to superparamagnetic state.Therefore,the reduction of catalysts were retarded.FT performance may be related to the composition of spinel(Fe(1-y)Mny)3O4 and the value of y,and the presence of MnCO3 and MnO could also favour the FT synthesis.In the iron-rich catalysts,Mn mainly acted as an electronic promoter,while in the manganese-rich catalysts,it acted as structural promoter besides its electronic behavior.Therefore,more complex phases were presented and more competitive reactions were present during the FT synthesis.