CuO助剂对铁铬系CO高温变换催化剂性能的影响

考察了CuO的不同前驱体对铁铬系CO高温变换催化剂反应性能的影响，研究发现，CuO助剂可改善催化剂的低温活性，以硝酸铜的加入形式效果较为显著。对样品进行了XRD、BET、H_2- TPR和XPS表征，结果表明， CuO助剂进入了Fe₃O₄的反尖晶石结构的八面体空隙，置换Fe²⁺与Fe₃O₄发生相互作用，改变了催化剂的还原特性，使^_Fe2O3还原为Fe₃O₄的还原温度降低了100 ℃左右。铜在催化剂的表面以Cu(OH)₂、CuO和Cu₂O三种形态存在，因Cu²⁺取代Fe²⁺的八面体配位单元，致使配位场稳定化能降低，催化剂表面容易产生O^2－缺位，所产生的新的活性中心极易吸附OH^－，使催化剂在低汽气比条件下参与CO变换反应，具有高活性且遏制烃类副产物的生成。

Influence of CuO promoter on catalytic properties of iron-chromium-based CO high-temperature shift (HTS) catalysts

The effects of different precursors for CuO on the catalytic properties of Fe-Cr-based CO high-temperature shift (HTS) catalyst were investigated. It was shown that CuO improved low-temperature activity of the catalyst and doping of CuO as copper nitrate was preferable. The catalysts were characterized by XRD, BET, H₂-TPR and XPS. The results showed that the incorporation of CuO improved reduction properties of the catalysts, resulting in lowering of the reduction temperature for Fe₂O₃ by about 100 ℃. Most copper species were dispersed in the form of Cu(OH)₂, CuO, Cu₂O on surface of the catalysts. Some Cu ions imbedded into interstice of the octahedron for Fe₃O₄ with reverse spinel structure and partly replaced Fe²⁺, leading to decrease of the octahedron ligand field stabilization energy. O₂-vacancies were hence formed more easily on surface of the catalysts, and the new active sites thus formed was liable to absorb OH^－, which contributed to their higher activity for water gas shift reaction (WGSR) under low stream/gas ratio and hindered formation of undesirable hydrocarbons.