Structures and properties of medium-temperature and hightemperature coal tar pitches

For the medium-temperature coal tar pitch (CTPZ) from Mane Lake,Xinjiang and the high-temperature coal tar pitch (CTPG) from Yulin,Shaanxi,the elemental composition,thermal stability,microcrystalline structure,molecular structure characteristics were analyzed deeply,the pyrolysis activation energy was calculated by the FlynnWall-Ozawa method,and the toluene soluble components and toluene soluble components of sample after thermal polymerization were determined by GC-MS. Results show that the H / C and O/ C ratios are 1. 005 and 0. 510,and 0. 062 and 0. 015,the pyrolysis reaction of CTPZ is more intense,the light components escape faster,and the thermal stability is poor,the final carbon residue rate is 16. 03% and 38. 47% ,respectively,CTPZ is only 42% of CTPG,the average pyrolysis activation energy are 84. 24 kJ/ mol and 104. 47 kJ/ mol at 210 -390oC,respectively,the aromatic sheet spacings of CTPZ and CTPG are 0. 404 nm and 0. 356 nm,which are 18. 82% and 4. 71% higher than the graphite aromatic sheet spacing of 0. 340 nm,respectively,the former aromatic ring has more alkane side chains and non-planar cyclic alkanes,and the order between the aromatic rings is worse,CTPZ consists of normal long-chain alkanes,in which relative content of C20-C28 is more than 50 %,considering that the relative content of CTPZ n-alkanes exceeds 50% ,and the carbon chain length is within the requirements of paraffin oil,paraffin oil can be separated and prepared,whereas CTPG involves mainly aromatic hydrocarbons,in which the relative content exceeds 70% ,especially the relative content of fluoranthene is about 40% . After CTPG and CTPZ polymerize thermally for 0. 5h and 6 h,respectively,the former is well in agree with the first grade of modified coal tar pitch,it is suitable for modified asphalt raw materials,while QI,CV and SP of the latter are still far from the standard value. The GC-MS analysis results of the samples polymerized thermally show that the content of polycyclic aromatic hydrocarbon (PAHs) in CTPG increases,indicating that polycondensation reactions of aromatic hydrocarbons occur; whereas the content of chain alkanes in CTPZ increase,indicating pyrolysis reactions of part aromatic side chains take place.