Study On Modification Of MWNTs And Their Application As Cobalt Catalyst Support

As new carbon material, carbon nanotubes (CNTs) have great potential value in such fields as nano-materials, nano-biology, nano-chemistry and so on, owing to their superior characteristics of mechanical, electromagnetic, optical properties and thermal stability.A large variety of theories and researches have shown that CNT is becoming one of the most promising catalyst supports. The active metal particles in CNTs supported catalyst can be effectively controlled in the diameter of nanometer scale, which can significantly improve the catalytic performance. However, CNTs'application have been restricted for the reason that CNT does not dissolve in most of solvents. So, how to improve the dispersion of CNTs in the solvents is critical for CNTs used as support.In this thesis, modification treatment of CNTs is investigated in different ways such as long time azeotropic reflux with nitric acid; reflux with sulfuric acid in N2 atmosphere; reflux with sodium hydroxide solution and immersion into hydrogen peroxide under ultrasonification environment. The modified CNTs were characterized by BET, TEM and IR and the results showed that CNTs treated by H2O2 or NaOH and followed by azeotropic reflux in wt.60% nitric acid had bigger specific surface area and ordered arrangement than as-purchased ones. The long tube was cut off showing open tips and functional groups like -OH, -COOH, etc. appreared on the surface to inrease its defect sites. So the solubility of the modified CNTs in different solvents is greatly improved and the functional groups on the surface defects provide more anchor sites for active metal loading on CNTs surface.Co-based catalysts supported on the modified CNTs were prepared and the effect of pH value and promoter La on the catalyst performance were investigated. The results showed that, La and ammonia could effectively avoid the aggregation of Co particles and increase the dispersion of Co on the surface of CNTs.