摘要
采用“柠檬酸法”制备的W Fe MgO催化剂 ,在小型流化床反应器中分别以Ar和H2 为载气在 1 0 73～ 1 373K下催化甲烷分解制单壁碳纳米管 (SWCNTs) .实验结果表明 ,用H2 作载气制备SWCNTs的最佳温度为 1 373K ,在Fe∶Mg摩尔比≤ 1 0∶1 0 0时 ,催化剂上的碳产率随其W载量的增加而显著增大 ,产物中的SWCNTs含量也保持在较高水平 ,最高碳产率可达 5 5 %(相对于催化剂的质量分数 ) .而使用Ar载气时最佳反应温度为 1 0 73K ,用W∶Mg摩尔比为 1∶1 0 0的催化剂可制得SWCNTs含量较高的产物 ,而W∶Mg摩尔比超过 1∶1 0 0的催化剂上产物中的SWCNTs含量显著下降 .根据XRD和XPS实验结果推测了W Fe
The W Fe MgO catalyst was prepared by calcination of the mixture of Mg(NO 3) 2·6H 2O, Fe(NO 3) 3·9H 2O, ammonium tungstate and citric acid at 823 K and used to prepare single walled carbon nanotubes (SWCNTs) in a fluidized bed reactor with 25%CH 4 H 2 or 25%CH 4 Ar gas mixture at 1?073 ～ 1?373 K. The effects of reaction temperature, carrier gases and catalyst composition on the carbon production were investigated by Raman spectroscopy, transmission electron microscopy (TEM), X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). The results indicated that the optimal temperature of methane catalytic decomposition was 1?373 K using H 2 as carrier gas and 1?073 K using Ar as carrier gas. In H 2 atmosphere at 1?373 K, the carbon yield increased with the W content in the catalyst and the SWCNTs content in the products was constantly high; the highest carbon yield of SWCNTs could be up to 55% (based on the catalyst mass) on the catalyst with a W∶Fe∶Mg molar ratio of 3∶10∶100. In Ar atmosphere at 1?073 K, a high SWCNTs content product could be obtained on the catalyst with W∶Mg=1∶100, but with W∶Mg more than 1∶100 the SWCNTs content in the products dropped sharply. According to the results of XRD and XPS analysis, active phases for the SWCNTs growth is suggested.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2004年第7期561-570,共10页
基金
国家重点基础研究发展规划 (G2 0 0 0 0 775 0 3 )
国家自然科学基金 ( 2 0 2 73 0 0 3 )资助项目
关键词
钨
铁
氧化镁
负载型催化剂
单壁碳纳米管
甲烷
分解
流化床反应器
tungsten, iron, magnesium oxide, supported catalyst, single-walled carbon nanotube, methane, decomposition, fluidized bed reactor
