钠作助剂的Ni／Al_2O_3上的CO_2加氢反应

用稳定态活性测试法研究了一系列不同载钠量Ｎｉ／Ａｌ_２Ｏ_３催化剂上的ＣＯ_２加氢甲烷化行为，并对它们进行了ＸＲＤ和程序升温还原表征。实验结果表明，在所用钠量范围内，于Ｎｉ／Ａｌ_２Ｏ_３上的ＣＯ_２加氢生成甲烷的活性随Ｎａ加入量的改变而变化，这与催化剂上Ｎｉ物种的分配有关，６７３Ｋ附近还原出的Ｎｉ物种可能是良好的ＣＯ_２加氢甲烷化活性中心。Ｎａ助剂的作用主要是改变Ｎｉ物种的分配。通过Ｎａ助剂的加入，可获得在化学剂量ＣＯ_２／Ｈ_２比下使ＣＯ_２几乎完全转化为甲烷的低镍催化剂。

CO_2 hydrogenation over Na promoted Ni/Al_2O_3 catalysts

Using a method of steady state activity test,hydrogenating methanation of CO2 was investigated over a series of Fi/Al2O3 catalysts promoted by Na of various addition amounts,and characterization of the catalysts were also carried out by XRD and temperature-programmed reduction. The results show that activity of Ni/Al2O3 over which CO2 is hydrogenated to methane changes with Na added within range,which is considered relative to the distributions of Ni species on the catalyst.It is found that the reduced Ni species near 673 K could be good active sites for hydrogenation of CO2 to methane. Substantially,Na promoter plays a role of changing distributions of Ni species on the catalyst. Adding Na, a catalyst with a lower content of niceki is obtained over which CO2 can be almost completely converted to methane at stoichiometric CO2 /H2.