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

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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.