碳氧定向反应Fe／C系催化剂中助剂的作用

EFFECT OF PROMOTER K AND Cr ON Fe/C CATALYST IN DIRECTIONAL CARBON-OXYGEN REACTION

本文采用微反－色谱，穆斯堡尔谱及ＸＰＳ等分析手段，研究了碳氧定向反应生成ＣＯ的Ｆｅ／Ｃ系催化剂中助剂Ｋ，Ｃｒ的作用。结果表明，助剂能大大提高定向氧化反应活性，并能稳定主活性组分的价态和提高其分散度。复合催化剂Ｆｅ－Ｋ－Ｃｒ／Ｃ无论在催化活性，稳定性及抗烧结性能方面都优于单组分催化剂。

The Fe/C catalyst prepared by heat treatment at 350℃ in Ar favours CO_2 formation but shows low selectivity of CO in carbon-oxygen reaction. It must be treated at700℃in Ar to predominantly produce CO.Adding the promoter K and Cr can further increase activity and stability of CO formationn and get the value of CO/(CO+CO_2)(%)inproduct approach or up to thermodynamics equilibrium value at high temperature. From thedata of Mossbauer spectra,it can be found out that iron species change greatly after thetreatment of catalyst at different temperature,a-Fe_2O_3 is the only composition when treatedat 350℃;while the catalyst is mainly composed of a-Fe and Fe_3C at 700℃. It is obviousthat the chemical state of iron is key-point for the selectivity of CO formation. Iron in re-duced state will gradually be oxidated again in oxidation reaction. The promoter K and Crcan keep the valence of iron in reducted state stable in oxidation atmosphere,therefore,canimprove its selectivity and stability of CO formation,The XPS measurement shows that Kpromotes activited Fe component moving to small pores of activited carbon,therefore it canexpane the area of activited Fe. Thus,the catalyst of Fe-K-Cr/C is more stable and resis-tant to sintering.