铜、铁、铈、镁的氧化物对镍还原性能的影响

采用热导程序升温还原法(TC-TPR),结合x射线衍射分析法(XRD),研究了铜、铁、铈和镁等氧化物对镍的还原性能的影响以及作用机理。结果表明,铜是通过它自身还原后的解离吸附氢以促进镍还原的。铁则是通过使载体惰性化,削弱载体与氧化镍的作用而促进镍还原的。氧化镁由于分子结构与氧化镍相似,易生成镍镁氧化物固溶体,使镍的还原难度显著增加,而氧化铈由于本身需要在1200K以上才能被还原,故对镍的还原性能没有明显影响。我们还对实验结果进行了动力学处理,求出相应的还原活化能。

The effect of CuO,Fe_2O_3, CeO_2 and MgO on reducibleness of nickel catalysts

The effect of CuO, Fe_2O_3, CeO_2 and MgO on reducibleness of nickel catalysts was investigated by TPR and XRD.The results showed as follows: CuO can promote nickel oxide reduced since it is first reduced to metal copper on which atomic absorption hydrogen may be produced by dissociative chemisorption of hydrogen and overspills to the surface of NiO. Under certain condition Fe_2O_3 can also promote nickel oxide reduced as the Fe~(+++) ions may be diffused into the lattice of Al_2O_3 to form solid solution which inhibits the interaction between NiO and support. MgO pronoucedly makes the reduction tempcrature of NiO increased because MgO and NiO form a solid solution (Ni_xMg_(1-x)O) which is more difficult to be reduced than NiO. Owing to the fact that CeO_2 reacts neither with NiO nor the support under the experimental condition, it does not affect the reduction of NiO.