摘要
发生在中煤阶阶段的第二次煤化作用跃变导致煤的许多物理化学性质出现了转折性变化,而聚集态结构变化可能是导致这种转折性变化的根本原因。为详尽研究中煤阶煤结构演化特征及其与第二次煤化作用跃变的关系,选取了6个跨越第二次煤化作用跃变的中煤阶煤样(R_(o,max)=1.10%~1.63%),应用拉曼光谱法(Raman)对其进行结构表征,并利用分峰拟合软件分别对其一级模和二级模光谱曲线进行分峰拟合,在此基础上计算了相关结构参数。结果表明:Raman结构参数随R_(o,max)的演化不是线性的,反映煤结构演化的复杂性,据Raman结构参数的演化特征,可以将R_(o,max)=1.10%~1.63%阶段的煤化作用分为3个阶段,转折点分别位于R_(o,max)=1.30%和R_(o,max)=1.50%附近,正好与前人发现的第2次和第3次煤化作用跃变发生的位置相当,说明Raman结构参数可以反映煤化作用跃变的发生,同时也表明Raman光谱是一种研究煤结构的有效手段。第1阶段为R_(o,max)=1.10%~1.30%,以长链脂肪族结构裂解生成液相物质为主,同时断裂后的较短链的脂肪烃及芳环上的脂肪族取代基会形成脂肪环结构,煤结构的支链化程度增加,阻碍了芳香体系之间的定向排列,芳香体系排列有序度达到最差,表现为WG最小(G峰位置),FG/D最大(F为两峰半高宽比),A_(D)/A_(G)最小(A为峰面积),AS/A1增加,A_((2G)R)/A_(2)大幅减小;第2阶段为R_(o,max)=1.30%~1.50%,上一阶段形成的脂肪环发生芳香化作用,导致芳香C—H结构含量增加,无定形碳含量达到最少,芳香化程度及芳香结构有序度均增加,表现为A_((GR+VL+VR))/A_(D)、A_((GR+VL+VR))/A_(G)和FG/D大幅减小,A_(D)/A_(G)增加,WG及d(G-D)快速增加;第3阶段为R_(o,max)=1.50%~1.63%,一方面,第二阶段形成的芳香环之间发生缩聚反应,导致A_((2G)R)/A_(2)减小,另一方面,芳香环体系间的各种桥键继续断裂,导致一些小尺寸芳香结构的生成,表现为A_((2G)R)/A_(2)减小,WG小幅减小,A_((GR+VL+VR))/A_(D)和A_((GR+VL+VR))/A_(G)增加。这些结果是深入理解煤化作用跃变机制及煤化作用机制的基础。
The second coalification jump which occurred during the middle-rank led to abrupt changes of many physical and chemical properties of coal,and the change of the aggregate structure may be the fundamental reason.In order to investigate the structural evolution characteristics of middle-rank coal and its relation with the second coalification jump in detail,the structure characteristics of six middlerank coals(R_(o,max)=1.10%-1.63%)that across the second coalification jump were studied by Raman spectroscopy,and the structural parameters were calculated by fitting the first-order and second-order Raman spectrum using the fitting software.The results indicated that the evolution of Raman structural parameters with R_(o,max) is not linear,reflecting the complexity of the structural evolution of coal.According to the evolution characteristics of Raman structural parameters,the coalification during the stage of R_(o,max)=1.10%-1.63%can be divided into three stages.The turning points are located near R_(o,max)=1.30%and R_(o,max)=1.50%,respectively,which are exactly equivalent to the positions of the second and the third coalification jump discovered in previous research.It indicated that the Raman structural parameters can reflect the occurrence of the coalification jump,moreover,Raman spectroscopy is an effective method to study the coal structure.The first stage is R_(o,max)=1.10%-1.30%,the long-chain aliphatic structures cracked and the remained shorter-chain aliphatic hydrocarbons and aliphatic substituted structures on the aromatic rings will form new alicyclic structures,which caused the branched degree increases and hindered the alignment of aromatic systems in coal.The order degree of aromatic system is thus reached the least near R_(o,max)=1.30%,with the smallest WG,the largest FG/D,the smallest A_(D)/A_(G),the increase of AS/A1,and the significant decrease of A_((2G)R)/A_(2).In the second stage of R_(o,max)=1.30%-1.50%,the aromatization of the alicyclic structures formed in the previous stage resulted in an increase in the content of aromatic C—H structure and the least of amorphous carbon structure.Besides,the degree of aromatization and aromatic structural both increased,which showed that A_((GR+VL+VR))/A_(D),A_((GR+VL+VR))/A_(G) and FG/D decreased significantly,A_(D)/A_(G) increased,WG and d(G-D)increased quickly.The last stage is R_(o,max)=1.50%-1.63%,the condensation reaction occurred between the aromatic rings formed in the second stage,leading to the reduction of A_((2G)R)/A_(2).Meanwhile,the various bridging bonds between aromatic ring systems continued to break,resulting in the formation of some small-scale aromatic structures,as evidenced by a decrease in A_((2G)R)/A_(2),a small decrease in WG,and an increase in A_((GR+VL+VR))/A_(D) and A_((GR+VL+VR))/A_(G).These results are the basis for deeply understanding the mechanism of coalification jump and coalification.
作者
邵燕
陈小珍
李晔熙
左家琦
崔曦
蒋恒宇
李美芬
SHAO Yan;CHEN Xiaozhen;LI Yexi;ZUO Jiaqi;CUI Xi;JIANG Hengyu;LI Meifen(Department of Earth Science and Engineering,Taiyuan University of Technology,Taiyuan 030024,China;Shanxi Key Laboratory of Coal and Coal Measure Gas Geology,Taiyuan University of Technology,Taiyuan 030024,China)
出处
《煤炭科学技术》
EI
CAS
CSCD
北大核心
2023年第8期295-303,共9页
Coal Science and Technology
基金
国家自然科学基金资助项目(U1910204,41772165,41572144)。
关键词
中煤阶煤
RAMAN光谱
结构演化
聚集态结构
煤化作用跃变
middle-rank coal
Raman spectroscopy
structural evolution
aggregate structure
coalification jump
