Influence of Preparation Methods on Catalytic Performance of Fe/NCNTs Fischer-Tropsch Catalysts

Abstract

Fischer-Tropsch synthesis (FTS) is a classical topic of great significance because of the approach of post-petroleum times. Recently we found that, taking the advantage of the anchoring effect and intrinsic basicity of nitrogen-doped carbon nanotubes (NCNTs), iron nanoparticles could be conveniently immobilized on the NCNTs without surface pre-modification. The so-constructed Fe/NCNTs catalyst presents the superb catalytic performance in FTS with high selectivity as well as high catalytic activity and stability. In this study, three Fe/NCNTs catalysts were prepared by incipient wetness impregnation method, colloidal method and deposition-precipitation method, denoted as Fe/NCNTs-IWP, Fe/NCNTs-C, and Fe/NCNTs-DP, respectively. The influence of preparation methods on the particle size distribution and morphology, reduction and carbonization of the active species, as well as the FTS catalytic performance were systematically examined. The results indicate that the incipient impregnation method could achieve high dispersion, smaller particles and narrower size distribution [(8±4) nm], leading to the easier reduction and carbonization of the iron nanoparticles compared with those prepared by the other two methods. The FTS catalytic performance of the Fe/NCNTs-IWP catalyst is much better than those of the Fe/NCNTs-C and the Fe/NCNTs-DP catalysts in terms of the high lower olefins selectivity, high catalytic activity and stability. Colloid method got the different morphologies of iron particles with the average size of (13±7) nm. The active iron species was susceptible to oxidation during the reaction, which cause poor catalytic activity and stability. The deposition-precipitation method got the largest particles of (19±11) nm which were difficult to be reduced and carbonized, leading to the sharp decline of the catalytic activity and stability after 15 h reaction. The size-dependence of the catalytic performance for the Fe/NCNTs catalysts in this study are generally in consistent with those in literatures for the iron catalysts supported on carbon nanotubes. These results should be suggestive for exploring the advanced FTS catalysts with the abundant N-doped carbon nanostructures.

Ruthenium Nanoparticles Anchored on Nitrogen-Doped Carbon Nanocages for Fischer-Tropsch Synthesis

“…催化剂性能(催化活性、目标产物选择性 和稳定性)可通过调节催化剂组成和结构 [8][9] 、载体 [10][11][12] 和助剂 [13] 等进行调控, 其中, 载体的比表面积、孔道结 构以及与活性组分的相互作用等可显著影响活性组分 的分散度、反应物和产物的吸/脱附特性、催化活性、产 物选择性和催化稳定性 [14] . 碳材料具有形态结构丰富、 比表面积高、表面性质易掺杂调控及稳定性好等优点, 是广泛使用的催化剂载体 [1,[15][16][17][18] . 近年来, 碳载费托合 成催化剂展现出优异性能.…”

Effect of Shell Thickness on Skeletal Fe@HZSM-5 Core-Shell Catalysts for Fischer-Tropsch Synthesis

“…Tsubaki 课题 组 [13][14] 首次报道了采用包覆法制备的用于 FTS 反应的 Co/SiO 2 @HZSM-5 核壳催化剂, 反应结果显示, 中等链 长的支链烷烃选择性显著提高, 催化剂的活性和选择性 在 100 h 评价中均能保持稳定, 显示了核壳型双功能催 化剂在 FTS 反应中的优越性. 铁的链增长能力虽然不及 钴, 但是具有操作温度宽、水煤气变换(WGS)活性高、 时空收率高、价格低廉等优点 [3,[15][16][17] . 且与钴相比, 铁的 FTS 活性温度与分子筛的裂解、异构化活性温度更为接 近 [18][19] , 因此, 铁基核壳型双功能 FTS 催化剂具有良好 的研究价值.…”