铁基超细粒子催化剂的F-T反应性能研究——Ⅰ.Fe-Mn催化剂的反应性能、活性相结构及锰的作用

STUDIES ON THE F-T PERFORMANCE OF IRON BASED ULTRAFINE CATALYSTS——Ⅰ. PERFORMANCE OF Fe-Mn CATALYST, ACTIVE PHASES AND ROLE OF Mn

由复合物控制降解法制得的Fe-Mn超细粒子催化剂同时具有高的CO转化率和较高的低碳烯烃选择性,并能一定程度地抑制甲烷和高沸点烃的生成。反应初期催化剂的活性相是在不断变化的,导致了F-T活性和选择性随反应时间的不断改变。类尖晶石相(Mn_xFe_(3-x)O_4)是高转化率条件下稳定的F-T活性相。在稳态条件下,Mn主要以MnCO_3形式存在,它与铁物相紧密接触可以显著提高低碳烯烃选择性和降低甲烷选择性。

The Fe -Mn ultrafine catalyst prepared from a special controlled degradation method of Fe - Mn oxalate can give high selectivity to light olefins while retaining high CO conversion, and depress the formation of methane and heavy hydrocarbons in certain extent. It is recognized that the active phases of Fe -Mn ultrafine catalyst are continously changed, from X- Fe_5C_2 or/and FeO - MnO at the beginning to Mn_xFe_(2-x)O_4 and MnCO_3 at steady stateof reaction, resulting in gradual alteration of F- T activity and selectivity during the conditioning period. Mn is mainly present as MnCO_3 at the steady state of reaction. It can improve the selectivity to light olefins and depress the formation of methane by intimately contacting or coordinating with iron- containing phase.