低中煤级煤结构演化的拉曼光谱表征

Raman characterization of structural evolution in the low-middle rank coals

  • 摘要: 对28个最大镜质组反射率为0.30%2.05%镜煤样品的Raman谱图进行拟合,获得拉曼结构参数。随着煤样镜质组最大反射率增大,拉曼结构参数发生有规律变化,显示出煤结构演变的复杂性。结果表明:D1和G的位置、峰位差(G-D1)及G的半峰宽与反射率存在良好的相关关系,D1与G半峰宽的比值(ID1/IG)随反射率的增大也呈现出明显的分段性。在此基础上得到煤的结构演化分为3个阶段,分别是镜质组反射率0.3%0.8%,0.8%1.6%和1.6%2.0%。在镜质组反射率0.3%0.8%阶段,D1向低波数移动,而G向高波数移动,G的半峰宽呈现递减趋势,表明煤结构朝有序结构演化,同时,D1的半峰宽无明显规律,ID1/IG的变化不明显,反映芳香体系的形成比较缓慢;在镜质组反射率0.8%1.6%阶段,煤中D1和G的位置、峰位差和G半峰宽出现极值,响应了第2次煤化跃变;在1.6%2.0%的阶段,各参数逐步稳定,表明煤中微晶结构基本稳定,G峰半峰宽继续减小显示芳香结构的增大过程。

     

    Abstract: In this study,the structural parameters of 28 vitrain samples with the maximum vitrinite reflectance (Ro,max ) ranging between 0. 30% -2. 05% were obtained from Raman spectra. The results show that the regular changing trend is found for the structural parameters of Raman spectra with the increasing Ro,max ,which further indicates the complexi- ty of coal structural evolution. Specifically,well correlation exists between the position of D1 and G,the difference of peak position and peak width at half height (PWHM) of G and Ro,max . The PWHM ratio of D1 to G designated as ID1 /IG also changes sectionally with Ro,max . Accordingly,the coal structural evolution process can be divided into three sta- ges,i. e. ,0. 3% -0. 8% ,0. 8% -1. 6% and 1. 6% -2. 0% . For the stage of Ro,max range of 0. 3% -0. 8% ,D1 shifts to- ward lower wavenumber,while G shifts to higher wavenumber. The decreasing trend is found in the PWHM of G with Ro,max . The aforementioned analyses confirm that the coal structure becomes ordered. There is no clear change found for the PWHM of D1 and ID1 / IG,indicating the slow formation process of the aromatic structure. For the vitrain samples of Ro,max range of 0. 8% -1. 6% ,the extreme point appears in the position of D1 and G,the difference of peak position and PWHM of G,which can be considered as the index of the mutation of the second coalification process. The related pa- rameters change slightly for the Ro,max of 1. 6% -2. 0% ,which shows that the microcrystal structure of coal become stable,and the decreasing PWHM of G indicates the growing stage of the aromatic structure.

     

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