铜物种对Cu/Fe2O3水煤气变换反应催化剂性能的影响

采用共沉淀法制备了系列铜负载量不同的Cu/Fe₂O₃水煤气变换(WGS)催化剂,并考察了铜负载量对催化剂结构和水煤气变换反应性能的影响. 结果表明,Cu/Fe₂O₃催化剂呈现出良好的水煤气反应性能,当CuO质量分数为20%时,催化剂的WGS性能最优,250 ℃时CO转化率高达97.2%,同时热稳定性也最好. 运用X射线粉末衍射(XRD)、N₂物理吸脱附和H₂程序升温还原(H₂-TPR)等手段对Cu/Fe₂O₃催化剂的物相、织构特征及还原性能进行了表征,结果表明,CuFe₂O₄物种的存在极大地改善了催化剂的还原性能和WGS反应活性. 这是由于CuFe₂O₄特殊的尖晶石结构有利于Cu微晶的稳定;同时,CuFe₂O₄在低温下即被还原为单质铜,有利于促进催化剂体系中电子的转移. 此外,通过(NH₄)₂CO₃溶液处理,研究了独立相CuO对Cu/Fe₂O₃催化剂WGS反应性能的影响,结果发现,独立相CuO的存在,有利于H原子在各组分传递,从而促进催化剂的CuFe₂O₄的还原,改善Cu/Fe₂O₃催化剂的WGS反应性能.

Influence of Copper Species on Performance of Cu/Fe2O3 Catalysts for Water Gas Shift Reaction

A series of Cu/Fe₂O₃ catalysts with different Cu loadings were prepared using a co-precipitation method, and the relationship between their structures and catalytic activities for the water gas shift (WGS) reaction was carefully examined. It was found that the as-prepared Cu/Fe₂O₃ catalysts exhibit excellent WGS performances, in particular, the one containing 20% (w) CuO (CF-20) shows the best catalytic activity, with CO conversion of 97.2% at 250 ℃. Its catalytic stability is also outstanding during the temperature range of 250-400 ℃. X-ray diffraction (XRD), N₂ physisorption, and H₂ temperature program reduction (H₂-TPR) techniques were used to characterize the crystal phases, textures, and reduction properties of the Cu/Fe₂O₃ catalysts. The results show that the generation of CuFe₂O₄, which has a spinel structure in stabilizing Cu microcrystals and is easier to be reduced at low temperature, resulting in enhancing their reduction properties and facilitating electrons transfer between Cu and Fe₂O₃, thus greatly improving the catalytic performance. Furthermore, (NH₄)₂CO₃ solution treatment of the as-prepared catalysts was performed to study the effect of bulk CuO existed in the Cu/Fe₂O₃ catalysts. The result suggests that the bulk CuO is favor for H atom transfer between Cu and Fe₂O₃, thus promoting the reduction of CuFe₂O₄, finally improving the catalytic performance.