Preparation,Purification Of Coal-based Carbon Nanomaterials And Their Catalytic Hydrogenation Propertiec

In the past decade novel carbon nanomaterials including carbon nanotubes and carbon nanoparticles with unusual structures and outstanding physical and chemical properties have generated great interest in the whole world. This interest has been driven chiefly by the potential applications of this new class of carbon materials, which lie in areas as diverse as electronic devices, tools in nanotechnology, catalyst supports and hydrogen storage. To date, production methods for carbon nanotubes are well established and allow their synthesis on a scale of grams per day, but these preparation methods or processes are still needed to be optimized in terms of efficiency and targeted carbon materials. With this in mind different raw materials or precursors such as high purity graphite and hydrocarbons are tested aiming to further improve the yield and purity of carbon nanotubes and to find new forms of carbon nanomaterials. In this paper, some Chinese coals with different properties are evaluated using a conventional arc discharge equipment with an aim of finding a suitable one for preparing novel carbon nanomaterials such as those fullerene-like nanoparticles with only a few carbon layers. The coal samples are first pretreated and carbonized to make coke rods which are conductive and self-supporting. The obtained coke rods are vaporized via arc discharge to prepare carbon nanomaterials that form as the inner soft core in a deposit on the cathode. The obtained nanotubes materials are pretreated by pyridine and purified using air or CO2. Catalysts based on carbon nanomaterials are prepared and their catalytic performance are investigated with the hydrogenation of nitrobenzene as a probe reaction and compared with other carbonaceous supports. The techniques including SEM -~ HRTEM -. JR~ GC and GC-MS etc are used in this paper when it is appropriate and necessary to characterize the materials or to analyze the reaction products in the related ill experiments. The main results are as follows 1. Nanomaterials including nanotubes can be prepared from all the coal samples tested. The yield and morphologies of the carbon nanomaterials are related to the pretreatment conditions of the coal samples and preparation process parameters. 2. The properties, constitutions and structures of coal samples have influences on the yields of the carbon nanomaterials, and on their structures and abundance as well. In some cases the carbon nanomaterials yield obtained from some coal samples is higher than that from high purity graphite under the same experimental conditions, which leads one to infer that the high yield must be closely related to the intrinsic chemical structures of coal precursors. 3. The arc discharge method yields an inhomogeneous raw product, consisting of nanotubes and other carbon species such as fullerenes, polyhedra and other graphitized carbon structures. Hence, in order to exploit the enormous potential for technical application, effective purification of this material becomes necessary. It is found that the coal-derived raw carbon nanomaterials could be effectively purified via pyridine pretreatment followed...