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采用射频热等离子体制备了Ni含量为50 mol%的Ni-CeO_2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CeO_2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CeO_2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CH_4:O_2=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H_2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.
The Ni-CeO 2 catalyst with Ni content of 50 mol% was prepared by RF thermal plasma and its catalytic activity in partial oxidation of methane was investigated. In the process of catalyst preparation, a radio frequency plasma torch with a plate power of 52 kVA Ni (about 5 μm in diameter) and CeO 2 powder (about 200 nm in diameter) were simultaneously heated at a rate of about 120 g / h by powder X-ray powder diffraction and transmission electron microscopy. The results showed that the precursors formed a highly crystalline CeO 2 carrier, The particle size of Ni particles is smaller (<50 nm). The methane part of the prepared sample was investigated under normal pressure, over 500 ℃ and CH_4: O_2 = 2: 1 (molar ratio) The results showed that the conversion of methane was above 70% and the selectivity of CO and H 2 was over 90% at 550 oC for 24 h despite the high Ni content (~ 50 mol%) in the samples However, at 750 oC for 24 h, the surface of the catalyst formed filamentous carbon, and the methane conversion rate rose to more than 90%.