Preparation And Properties Analysis Of Mesophase Pitch Of Low ASH Content

Due to its high carbon yield and good rheological performance, mesophase pitch can be the precursor of many kinds of carbon materials (such as pitch based carbon fiber, high power electrode needle coke, carbon-carbon composite materials), and it has been a hot research field of carbon materials recent years. At present, researchers prefer to explore the molecular structure of the pitch, and they use different methods to prepare mesophase pitches. As a result, the structure and properties of the mesophase pitches can be designed. In this paper, the catalytic method and co-carbonization method were used to prepare the mesophase pitches.The mesophase pitches were prepared from naphthalene using AlCl3as the catalyst by two steps. The heat treatment parameters (including heat treatment temperature and holding time) were investigated to contrast the effects on the ash content and yield of the naphthalene oligomers at the first step. The200℃holding5hours was chosen as the best heat treatment condition. The ash content of the oligomer was0.18%and the yield was83.6%. The XPS spectra of the oligomer showed that the catalyst AlCl3had translated into Al(OH)3or Al2O3after the first step heat treatment. Increasing the temperature of the heat treatment would lead more and more AlCl3translating into Al(OH)3. The naphthalene oligomers were characterized by elemental analysis, MS and GPC test. As a result, the average molecular type of naphthalene oligomer was calculated. According to the NMR spectrum, the average molecular structure model of the naphthalene oligomers was calculated. Then, the naphthalene oligomers were heat treated by the second step at a higher temperature. The360℃holding8hours was chosen as the best heat treatment condition. The mesophase content of the pitch was100%. The softening point was295℃, and the PI content of the mesophase pitch was66.7%.The coal tar oil based mesophase pitch was prepared by the method of co-carbonization using decahydronaphthalene as the co-carbonization agent. The affection of the mixing ratio of the pyridine and the coal tar oil on the ash content of the coal tar pitch was explored. The mixing ratio of the pyridine and the coal tar oil was determined as1:1. The ash content of the coal tar pitch was0.017%. The SEM images and EDS spectrum of the ash showed that the most content of the ash was iron oxides. The coal tar pitches were characterized by elemental analysis, MS and GPC test. As a result, the average molecular type of coal tar pitch was calculated. According to the NMR spectrum, the average molecular structure model of the coal tar pitch was calculated. The heat treatment process parameters (including the addition of the decahydronaphthalene, heat treatment temperature and holding time) were investigated to contrast the effects on the mesophase content of the pitch. The addition amount of the decahydronaphthalene was chosen as10%. The400℃holding10hours was chosen as the best heat treatment condition. The mesophase content of the pitch was100%. The yield of the mesophase pitch was48.4%,and the softening point was265℃. The H/C was0.49, and the PI content of the mesophase pitch was51.7%.