摘要：运用脉冲激光光解鄄激光诱导荧光(PLP鄄LIF)的方法研究了C 2 (a 3 装 u)自由基与若干不饱和碳氢化合物(C 2 H 4 (k 1),C 2 H 2 (k 2),C 3 H 6 (k 3)和2鄄C 4 H 8 (k 4))气相反应的温度效应. 在 298-673K的温度范围内, 获得了这些反应的双分 子反应速率常数. 获得的速率常数可以用 Arrhenius 公式表达如下: k 1 (T)=(4.53依0.05)伊10-11 exp[(196.41依5.20)/T], k 2 (T)=(3.94依0.04)伊10-11 exp[(143.04依4.28)/T], k 3 (T)=(7.96依0.17)伊10-11 exp[(185.10依8.86)/T], k 4 (T)=(1.04依0.02)伊10-10

Key indicatorsSingle-crystal X-ray study T = 293 K Mean '(C±C) = 0.005 A Ê Disorder in main residue R factor = 0.046 wR factor = 0.101 Data-to-parameter ratio = 15.5For details of how these key indicators were automatically derived from the article, see

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.

Key indicatorsSingle-crystal X-ray study T = 293 K Mean (C-C) = 0.009 Å R factor = 0.061 wR factor = 0.184 Data-to-parameter ratio = 18.9For details of how these key indicators were automatically derived from the article, see