Studies On Preparation Of The Transition-metal Nanocatalysts And Activity Of Carbon Deposits Of Their Catalyzing Decomposition Of Methane

The transition metal nanocatalysts (TMN) play an important role in the preparation of the advanced carbon nano-materials, such as carbon nanotubes (CNTs) by the catalytic decomposition of hydrocarbons. The studies on TMN and their application in the preparation of carbon nano-materials have been payed much attention in recent years.In this dissertation, the TMN was prepared by the modified sol-gel and sedimentation methods. The effects of the amount of ammonia added, grinding, the amount of organic phase added, the amount of support added and the temperature of calcination on the yield of TMN, percentage and morphology of carbon deposits were investigated.The experimental results presented that when the amount of organic phase added was 0 ml, adding an appropriate amount (120ml) of ammonia could improve the yield of TMN, and excessive amount of ammonia added (200ml) could reduce the yield sharply; the percentages of carbon deposits increased with the increase of amount of ammonia added, and when the amount of ammonia was more than 160ml, this trend became weak; the quantity of CNTs also increased. The percentage of carbon deposits and the quantity of CNTs were improved by grinding the samples before and after the heat treated.When the amount of ammonia added was 165ml, the yield of TMN was falling gradually with the increase of organic phase added; the particles of TMN smaller than 100nm became fewer; the percentages of carbon deposits, which were still more than the percentage when the amount of ammonia added was 0 ml, fell also; the quantity of CNTs in carbon deposits were fewer. When the amount of ammonia added is 165ml and the organic phase added was not 0 ml, calcination of catalysts at 1200℃for 2h led to the particles smaller than 100nm more and improved the percentage of carbon deposits and the quantity of CNTs.When the amount of ammonia added was 165ml and the organic phase added is 10.8ml, the yield of TMN increased gradually with the increase of the support added; the percentages of carbon deposits and the quantity of CNTs fell, when the support added was 15.5g, there was only several CNTs. When the support was added, calcinations of catalysts at 1200℃for 2h led to the particles smaller than 100nm less and carbon deposits mainly being big particles. The effect of concentration of transitional metal solution in water on the morphology of carbon deposits catalyzed by the TMN had been investigated. The experimental results presented that the TMN on quartz slice has some activity of carbon deposits. Villiform, particles, columniform, and some wirelike carbon deposits were obtained, and the morphology of carbon deposits was translated from villiform to particles gradually with the increase of the concentration of solution.