镍基催化剂上催化裂解甲烷生长碳纳米管

以共沉淀法制备的 Ni-Al、Ni-Cu-Al和 Ni-L a-Al为催化剂 ,甲烷为碳源 ,在 773～ 10 2 3 K制备碳纳米管 ( CNTs) ,并通过 TEM和 XRD表征了 CNTs的部分性质 ,讨论了催化剂、反应时间和反应温度对 CNTs形貌、结构和产率的影响。结果表明 ,不同催化剂在相同温度下制备的 CNTs的形貌和结构有很大差异。Ni-Al催化剂上生长的 CNTs倾向于碳纤维结构。Ni-Cu-Al催化剂上生长的 CNTs具有节状结构。Ni-La-Al催化剂上生长的 CNTs管腔较大、管径较均匀且石墨化程度最高。在 10 2 3 K下 ,各种催化剂的活性都是在反应初期较高 ,然后随反应时间降低。Ni-Al催化剂在 2 h后活性降低很快 ,在 5 h后完全失活。Ni-Cu-Al和 Ni-La-Al催化剂活性随时间降低较缓慢 ,最后分别在 10 h和 15 h后完全失活。各种催化剂上生长的CNTs的产率随反应温度变化而变化。Ni-Al、Ni-Cu-Al和 Ni-La-Al催化剂上制备的 CNTs分别在 92 3 K、973 K和高于 10 2 3K左右达到最高产率

Catalytic decomposition of methane over nickel-based catalysts to grow carbon nanotubes

Carbon nanotubes (CNTs) were synthesized from decomposition of methane at (773~1 023 K) over the catalysts of Ni-Al, Ni-Cu-Al and Ni-La-Al prepared by the co-precipitation method, and the obtained CNTs were characterized by TEM and XRD. The effects of the catalysts,the reaction time and the reaction temperature on the morphology, microstructures and yield of CNTs were investigated. TEM and XRD results show that the morphology and microstructures of CNTs produced on different catalysts at the same temperature were quite different. CNTs synthesized on the Ni-Al catalyst inclined to be carbon fibers. CNTs synthesized on the Ni-Cu-Al catalyst had joints in their hollow core. CNTs synthesized on the Ni-La-Al catalyst had large hollow core, uniform diameter and good graphitization. At 1023 K, the catalytic activities of the three kinds of catalyst were kept high at the initial period and then decreased with the increase of the reaction time. The catalytic activities of the Ni-Al catalyst declined quickly with time after 2 h and was deactivated completely at 5 h. The catalytic activities of Ni-Cu-Al and Ni-La-Al declined gradually with time and were deactivated completely at 10 h and 15 h, respectively. The yield of CNTs on the three kinds of catalyst varied with the reaction temperature. The reaction temperature at which the largest yield of CNTs was achieved was about 923 K on the Ni-Al catalyst, about 973 K on the Ni-Cu-Al catalyst, and a little higher than 1 023 K on the Ni-La-Al catalyst, respectively.