Preparation And Properties Of Naphthalene-based Mesophase Pitch

In this paper, a two-step process is applied to the preparation of mesophase pitch by using naphthalene as raw material and HF/BF3 as catalyst. The influence of catalytic polymerization temperature or catalytic polymerization time on the structure and properties of the synthesized naphthalene pitch was investigated by elemental analysis (EA), infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy ('H-NMR) and mass spectrometry (MS) analyses. the opitical texture of the prepared meophase pitch and its performance were characterized by polarized light microscopy(POM), thermal analysis(TG-DSC), thermogravimetry-mass spectrometry (TG-MS) and X-ray diffraction (XRD).the thermodynamic mechanism of the formation of naphthalene pitch by a thermopolymerization process was discused.Catalytic thermpolymerization temperature and time are the key factors of the formation of naphthalene pitch. The softening point(SP), coking value and toluene insoluble(TI) content of naphthalene pitch increase but the aromatic hydrogen content reduces with the increases of catalytic polymerization temperature and the holding time.The main product of polymerizationat 100? and 140? are mainly composed of dimer,trimer and their dehydrogenation products,as well as tetramer and pentamer or their derivative,respectively. The main products of catalytic polymerization at 140 ? for 3h are composed of naphthalene dimer and trimer,and transfer to oligomers and derivatives witch higer molecular weight with the thermpolymerization time increase ti 7h. An amount of aliphatic side chain and naphthenic structures existing mainly in the form of methyl and ethyl was found in molecular structure of naphthalene pitch prepared by Catalytic thermopolymerization.The anisotropic mesophase pitch component content, QI component content and the softening point increase with the increse of thermopolimerization condensation temperature and the time. Firstly,the content of soluble mesophase increases.and then decreases with the increase of thermopolimerization temperature.The optimized conditions are thermopolymerization at 400? for about 2h. The opitical texture of the formed mesophase pitch showes an anisotropy flow domain and the mesophase pitch possesses a yield of 77.5%,softening point of 248? and QI content of 35.8wt%.The pyrolysed gases of naphthalene pitch carbonization process mainly consist of H2, CH4, C2H4(C2H6, etc. H2 releasing temperature range is in 300?430?, CH4, C2H4 and C2H6 begin to release at above 430?, indicating that H2 releasing is mainly due to the dehydrogenation condensation reaction,and the release of CH4, C2H4 and C2H6 can be assigned to the pyrolysis reaction. After carbonization treatment,the carbon yield of meophsae pitch prepared at 400? for 2h was 81%, while the yield of naphthalene pitchwas 61%. Compared to naphthalene pitch,carbon prepared from mesophase pitch is easier to be graphitized and has a higher graphitization degree and larger grain size.