层剥离高岭土改性煤沥青的结构与热稳定性

Delaminated Kaolinite Modified Structure and Thermal Stability of Coal Tar Pitch

摘要:

在超声波作用下，以二甲基亚砜（DMSO）插层处理高岭土，通过熔融复合的方法改性煤沥青。采用X射线衍射、红外光谱、电镜、热分析表征了插层高岭土的层间距、层间相互作用、层分散形态以及改性煤沥青的热稳定性。结果表明，DMSO削弱了层间铝羟基与硅氧键之间的氢键作用，插层高岭土的层间距由0.716 nm增加至1.124 nm，插层率达到98.57%；熔融复合后，高岭土发生层剥离，(001)衍射峰消失，以薄层形态分散于煤沥青中。薄层形态的高岭土通过延缓空气传输速率的方式改善了煤沥青的热稳定性，插层高岭土改性煤沥青的最大失重速率温度为650 ℃，对应的失重率为78.04%，而原煤沥青失重率是85.41%。原煤沥青失重50%时的温度为490 ℃，而改性煤沥青达到550 ℃。未掺加高岭土时，煤沥青软化点为42.3 ℃，当高岭土质量分数为6%时，软化点增加到45.4 ℃，继续增加高岭土，软化点上升幅度减小。

Abstract:

Raw kaolinite was first intercalated with dimethyl sulfoxide (DMSO) under ultrasonic field, and then composited to modify coal tar pitch through melt process. The interlayer spacing, interlayer interaction, dispersion morphology and thermal stability of modified coal tar pitch were characterized by X-ray diffraction, FTIR spectrum, electron microscope and thermal analysis. The results show that the hydrogen bonds between aluminum hydroxyl and silicon oxygen bond are weakened because of DMSO intercalation, the interlayer space of kaolinite expands from 0.716 nm to 1.124 nm and the intercalation rate reaches 98.57%. After melt composition, the (001) diffraction peak disappears which means the kaolinite is delaminated by coal tar pitch molecules and the kaolinite layers are dispersed in the form of thin layers in coal tar pitch. At the maximum weight-loss-rate temperature of 650 ℃for intercalated kaolinite modified coal tar pitch, the weight loss is 78.04%, while raw coal tar pitch (RCTP) is high as 85.41%. For RCTP, the accumulative weight loss value of 50% appears at 490 ℃, whereas modified pitch rises to 550 ℃. Compared to RCTP, the softening point of modified pitch with 6 wt% intercalated kaolinite improves from 42.3 ℃ to 45.4 ℃, but the increasing extent of softening point decreases with more kaolinite dosage. Therefore, these dispersed layers improve the thermal stability of coal tar pitch obviously, which may be caused by ways of delaying air transmission.