Preparation Of Coal Mesophase Pitch

Mesophase is an important precursor for preparation of carbon materials and its structures determins the properties of prepared carbon materials. The purpose of this research was to manufacture the mesophase pitch from coal pitch modified by hydrogenation and coal tar pitch. Ordered mesophase pitch was carried out in a temperature-programmed autoclave. The parameters of preparation of mesophase pitch as well as the mesophase properties were investigated. In order to determine the better raw materials that prepared high-quality mesophase pitch, the properties of raw meterials and mesophase pitch were characterized by elemental analysis, FT-IR, 1H-NMR and apparent viscometer.It is well known that temperature and time play important role on mesophase structure and morphology. First of all, it could affect the speed of carbonization;Secondly, it also affected the depth of carbonization and determined the distribution of molecular weight of mesophase pitch. The experimental results showed that orderly arranged mesophase was prepared by coal pitch modified by hydrogenation when the temperature range and holding time were 420~430℃, 300min;respectively. Excellent mesophase prepared by coal tar pitch when the temperature range and holding time were 440~450℃, 260min, respectively. The properties of mesophase pitch perpared from two raw metarils were also analyzed. The results revealed that the mesophase pitch perpared by coal pitch modified by hydrogenation was better. The content of soluble mesophase was 49% and the optical texture was developed from incomplete coalescence to flow domain.The crystallinity and graphitization of mesophe pitch were high due to good fluidity and lattice parameters that the distance between the two crystal layers was3.453×10-10m and stack height was2.680×10-9m. Due to a large number of alkyl side chain and naphthenic structure in coal pitch modified by hydrogenation, the regorous reaction was inhibited in carbonization stage and kept a lower viscosity for a longer time. More naphthenic structure in coal pitch modified by hydrogenation was the main reason that the high-quality mesophase pitch was generated.Compared to coal tar pitch, Carbonization of coal pitch modified by hydrogenation was studied to correlate the content of alkyl groups in the mesophase pitches with coefficient of thermal expansion (CTE) and anisotropic orientation.The anisotropic indices of average length of vectors parallel to the CTE axis and average length of anisotropic unit vectors were 2.70×10-5m, 2.77×10-5m, respectively, and CTE value which was 0.1×10-6 /℃was significantly higher. Due to the increasing content of alkyl groups, the lower viscosity of the carbonization system favored the development of flow texture and uniaxial orientation and the sufficient gas evolution of good timing in carbonization forced the uniaxial arrangement of bulk mesophase molecules at the solidification stage.