还原方式及还原温度对甲烷部分氧化镍催化剂结构和反应性能的影响

Influence of reduction method (temperatureprogrammed reduction (TPR) and isothermal reduction) and reduction temperature on the structure and performance of nickelbased catalysts for methane partial oxidation was investigated by means of H2TPR, TEM and catalytic tests. Two catalysts were first prepared at different calcination temperatures (POM-1, calcined at 550℃; POM5, calcined at 950℃). For POM-1 catalyst, the isothermal reduction led to lower reduction degree and smaller nickel crystallites compared with TPR. However, the catalysts with different reduction methods had little difference in the catalytic activity. With increasing isothermal reduction temperature, the reduction degree of POM-1 catalyst decreased, and that of POM5 catalyst increased slightly. The size of nickel crystallites was smaller in POM-5 catalyst than that in POM1 catalyst. With increasing isothermal reduction temperature, there was no marked effect on the reactivity of POM-1, while the hotspot of POM-1 catalyst bed increased. However, the reactivity of POM-5 catalyst increased and the hotspot of POM-5 catalyst bed decreased, with increasing the reduction temperature. The hotspot of catalyst bed was related to the size of nickel crystallites. The larger the size of nickel crystallites was, the higher the hotspot temperature of the catalyst bed; this was perhaps due to the complete oxidation of methane promoted by large nickel crystallites.