助催化剂对Fe_(1-x)O基氨合成催化剂还原性能的影响

THE EFFECT OF PROMOTERS ON REDUCTION PERFORMANCE OF Fe 1- x O BASED AMMONIA SYNTHESIS CATALYST

当助催化剂存在时，Ｆｅ１－ｘＯ基催化剂的还原性能明显优于Ｆｅ３Ｏ４基催化剂，其原因是铝、钾、钙的氧化物对催化剂母体相Ｆｅ１－ｘＯ和Ｆｅ３Ｏ４还原性能的影响不同．由于Ａｌ３＋大量地进入Ｆｅ３Ｏ４的晶格而强烈地阻止Ｆｅ３Ｏ４的还原，只有少量的Ａｌ３＋能进入Ｆｅ１－ｘＯ晶格，因此对Ｆｅ１－ｘＯ的还原影响很小；虽然大量的Ｃａ２＋进入了Ｆｅ１－ｘＯ的晶格，但没有阻碍Ｆｅ１－ｘＯ的还原；Ｋ２Ｏ的存在明显加速Ｆｅ１－ｘＯ的还原，但对Ｆｅ３Ｏ４的还原没有促进作用．

The reduction performance of fused iron catalyst for ammonia synthesis is closely related with the phase composition of its precursor. However, the main reason why reduction performance of Fe 1- x O based catalyst is superior to that of Fe 3O 4 based catalyst is the different effects of aluminum, potassium and calcium oxides on the reduction of Fe 1- x O and Fe 3O 4. Al 2O 3 strongly affects the reduction of Fe 3O 4 based catalyst owing to Al 3+ inserting into the crystal structure of Fe 3O 4, but it affects the reduction of Fe 1- x O based catalyst weakly because only a small amount of Al 3+ can insert into the crystal structure of Fe 1- x O. A large amount of Ca 2+ inserted into the crystal structure of Fe 1- x O does not hinder the reduction of Fe 1- x O based catalyst. When K 2O is added into the precursor of the catalysts, it accelerates the reduction of Fe 1- x O based catalyst, but not the reduction of Fe 3O 4 based catalyst.