采用射频热等离子体合成Ni-CeO_2催化剂用于甲烷部分氧化(英文)

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.

Synthesis of Ni-CeO2 catalyst for the partial oxidation of methane using RF thermal plasma

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%.