采用射频热等离子体制备了Ni含量为50 mol%的Ni-CeO2催化剂，考察了其在甲烷部分氧化反应中的催化活性.在催化剂制备过程中，采用板功率为52 kVA的射频等离子体火炬将Ni(直径约5μm)和CeO2粉末(直径约200 nm)混合物同时加热，粉末添加速率约为120 g/h. X射线衍射和透射电镜表征结果表明，所用前驱体形成了高结晶的CeO2载体，其表面Ni颗粒的粒径较小(<50 nm).在常压、500 oC以上、反应物中CH4：O2=2：1(摩尔比)，并用Ar稀释的条件下考察了所制样品的甲烷部分氧化反应性能.结果表明，尽管所制样品中Ni含量较高(~50 mol%)，但在550 oC反应24 h后，甲烷转化率为70%以上， CO和H2选择性大于90%，有少量积碳.然而，在750 oC反应24 h时，催化剂表面形成了丝状碳，甲烷转化率升至90%以上.
Ni‐CeO2 catalysts with a nickel content of 50 mol%were prepared using RF thermal plasma, and their catalytic activities for methane partial oxidation were characterized. For the synthesis of Ni‐CeO2 catalysts, a precursor containing Ni (~5‐μm diameter) and CeO2 (~200‐nm diameter) powders were heated simultaneously using an RF plasma at a power level of~52 kVA and a powder feeding rate of~120 g/h. From the X‐ray diffraction data and transmission electron microscopy images, the precursor formed into high crystalline CeO2 supports with nanosized Ni particles (<50‐nm diameter) on their surfaces. The catalytic performance was evaluated under atmospheric pressure at>500 °C and a CH4:O2 molar ratio of 2:1 with Ar diluent. Although the Ni content was high (~50 mol%), the experimental results reveal a methane conversion rate of>70%, selectivities of CO and H2 greater than 90%and slight carbon coking during an on‐stream test at 550 °C for 24 h. However, at 750 °C, the on‐stream test revealed the formation of filament‐like carbons with an increased methane conversion rate over 90%.
参考文献
| [1] | P. Buchner;H. Schubert;J. Uhlenbusch;M. Weiss.Evaporation of zirconia powders in a thermal radio-frequency plasma[J].Journal of Thermal Spray Technology,20014(4):666-672. |
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