Development of Supported Metal Catalysts to Produce Carbon Nanotubes from Hydrocarbons under Mild conditions

我们一直致力于开发一种简便的方法，通过液相制备法来制备贵金属纳米颗粒。我们已经应用这种具有精确控制尺寸的金属纳米颗粒作为催化剂的活性物种来制备多壁碳纳米管（MWNT）。研究了Au/SiO_2-Al_2O_3和Pd/Al_2O_3催化剂上乙炔的分解反应，得到以下结果：1. Au催化剂（1）在Au/SiO_2-Al_2O_3催化剂上，在550℃的低温条件下制备了碳纳米管。没有报道出现在Au催化剂上形成MWNTs。（2）考察了催化剂载体对MWNTs制备的影响，发现SiO_2-Al_2O_3催化剂制备MWNTs的性能最好。(3)By随着温度的升高，制备出具有高度堆叠的层状和弯曲结构的MWNTs。（4）当Au负载量超过5wt%时，Au纳米粒子在SiO_2-Al_2O_3上发生烧结，抑制了MWNTs的形成。（5）当Au与载体之间的相互作用较强时，形成了开口端的MWNT，而当相互作用较弱时，Au颗粒被包覆在MWNT的封闭端。（2）碳纳米丝主要在低温下生成。在高温下制备了高度结晶的MWNT。

We have been developing facile method to produce noble metal nanoparticles by liquid preparation method. We have applied such metal nanoparticles with precisely controlled sizes as active species of catalysts to produce multi-walled carbon nanotubes (MWNT). Acetylene was decomposed over Au/SiO_2-Al_2O_3 or Pd/Al_2O_3 and following results are obtained :1.Au catalyst(1)MWNTs were formed at very low temperature of 550℃ over Au/SiO_2-Al_2O_3 catalyst. No report appeared for the formation of MWNTs over Au catalyst.(2)Effects of catalyst-support was investigated and SiO_2-Al_2O_3 showed the best performance to form MWNTs.(3)By an increase in temperature, MWNTs with highly stacked lamellae and bent structure was produced.(4)Supported amount of Au over 5wt% causes sintering of Au nanoparticles on SiO_2-Al_2O_3 and formation of MWNTs was inhibited.(5)When interaction between Au and support was strong, open-end MWNT was formed, while Au particle was encapsulated at the closed end of MWNT when the interaction was weak.2.Pd catalyst(1)Pd/Al_2O_3 with different Pd sizes produced MWNTs with different diameters depending on sizes of Pd at 700℃.(2)Carbon nanofilament was mainly produced at low temperature. Highly crystallized MWNT was produced at high temperature.