The Carbonization Behavior Research Of Polycyclic Aromatic Hydrocarbons

Autogenic pressure method is used to carbonize different types of polycyclic aromatic hydrocarbons (PAHs) and derivatives. The morphology, structure and performance of products with different preparation conditions are investigated. The main work is as follows: Naphthalene, anthracene, pyrene, tetralin and PAHs derivatives derived from mesophase carbon microbeads (MCMB) are used to be carbon sources. The C4H14NiO8, C4H14CoO8, boric acid are used as catalysts with a certain proportion of carbon sources. In order to study the crystal structure and morphology changing of products, the experiments focus on the PAHs’ carbonization behavior with different carbonization temperature, catalyst content, heating rate and other conditions. Then, the electrochemical properties of final products as lithium ion secondary battery electrode material and the performance with low and large (0.3mA and2C) current charge/discharge characteristics are studied. In contrast, graphitized needle coke and MCMB are also studied. The main conclusions are summarized as follows:1. PAHs with Alkyl side chains are obtained by mixed MCMB and dodecene. The mixture is heated at400℃under its autogenic pressure. The relative molecular mass is from374to412. The results show that PAHs with good solubility could be obtained by alkylating insoluble and infusible MCMB.2. Naphthalene, anthracene, MCMB-PAH and pyrene are used as carbon sources to investigate the morphology and structure changing through autogenic reactions at900℃. Carbon spheres with5-10μm are obtained by carbonization of naphthalene and anthracene, and carbon spheres with1-5μm are obtained from MCMB-PAH. Bulk carbon are obtained by carbonization of pyrene. With the increase of aromatic rings, the graphite degree enhances obviously. The main process changes from gas carbonization to liquid carbonization. The pyrolysis of aliphatic hydrocarbons in the carbon precursor has the effect on the crystallinity of final product.3. The influence of catalysts and carbonization temperature on products are studied. The various carbon structures are obtained with the existence of catalysts. The best crystallinity of57.1%is obtained at the ratio of3:l(naphthalene/C4H14NiO8) with autogenic pressure. The product prepared by naphthalene contains abundant carbon nanotubes with30nm diameters, and better than that of tetralin. The crystallinity and yield could not change with the catalyst.4. The carbon nanotubes could not be obtained by low heating rate carbonization. The high heating rate leads to formation of carbon nanotubes, and the best temperature is900℃. The degree of graphitization is57.1%and53.6%respectively by carbonization of naphthalene and tetralin.5. The products prepared from naphthalene, anthracene, pyrene and MCMB-PAH are used as Li-ion battery electrode materials to study its electrochemical performance. The reversible capacity of MCMB-PAH is268.2mAh/g with low current, which is best in4pyrolysis samples, but lower than2graphitized samples. The products prepared by PAHs which carbonized at900℃have better2C charge/discharge performance than needle coke and MCMB. The capacity of the four samples can maintain64.8%at least, and the highest is87.4%. The2C charge/discharge capacity of sample MCMB-PAH arrived227mAh/g, which is57.3%more than needle coke and91.1%more than MCMB.