Al2O3改性CuO/Fe2O3催化剂水煤气变换反应性能

采用分步共沉淀法制备了不同Al₂O₃含量(0%-15% (w))的CuO/Fe₂O₃催化剂, 并进行水煤气变换反应(WGSR)评价测试. 制得的催化剂中含有复合物CuFe₂O₄, 其晶粒尺寸, 氧化还原性质和表面Cu分散通过相应表征手段加以研究. X 射线粉末衍射(XRD), 拉曼(Raman)光谱, N₂物理吸附, N₂O分解和CO₂程序升温脱附(CO₂-TPD)等表征技术说明适量Al₂O₃的加入可以促进尖晶石CuFe₂O₄发生由四方相向立方相的转变, 阻止催化剂中Cu烧结, 增大表面Cu分散, 增加弱碱性位点的数量. 此外, 采用H₂程序升温还原(H₂-TPR)技术探究改性的CuO/Fe₂O₃催化剂的还原性能. 关联结果发现, Al₂O₃掺杂在增大铜物种的耗氢量, 降低其还原温度方面起着重要的作用. 即Al₂O₃的添加促进CuO/Fe₂O₃催化剂中铜铁物种之间的协同作用. 结合活性测试和表征结果,适量的Al₂O₃ (10%(w))改性的催化剂具有较小的Cu颗粒尺寸、较大的Cu分散、较强的还原性能、较多数量的弱碱性位点, 因此具有更好的初始活性和热稳定性.

Performance of Al2O3-Modified CuO/Fe2O3 Catalysts in the Water-Gas Shift Reaction

The water-gas shift reaction (WGSR) has been carried out over CuO/Fe₂O₃ catalysts modified by different loadings of Al₂O₃ (0%-15% (w)), prepared by a stepwise co-precipitation method. Composite mixture CuFe₂O₄ was produced, and the crystalline size, redox property, and surface metallic Cu dispersion were manipulated. The appropriate introduction of Al₂O₃ can promote the phase transition of spinel CuFe₂O₄ from tetragonal to cubic, inhibit aggregation of Cu-crystallite, improve Cu dispersion, and increase the amount of weak basic sites, as confirmed using powder X-ray diffraction (XRD), Raman spectroscopy, N₂ physisorption, N₂O decomposition, and temperature-programmed desorption of carbon dioxide (CO₂-TPD) techniques. In addition, a temperature-programmed reduction of hydrogen (H₂-TPR) technique was used to investigate the reducibility of the modified CuO/Fe₂O₃ catalysts. It was found that the Al₂O₃-doping plays an important role in increasing the hydrogen consumption of the copper species, and decreasing reduction temperature. This means that the Al₂O₃ can promote a synergistic interaction between the copper and iron species in the CuO/Fe₂O₃ catalysts. Overall, the Al₂O₃-modified catalyst (10%(w)) has a smaller Cu particle size, better Cu dispersion, greater reducibility, and larger amount of weak basic sites, resulting in a much higher initial catalytic activity and better thermal stability.