中煤级煤Micro-Raman结构对甲烷吸附的响应  

Micro-Raman characterization of the response of medium-rank coals structure to methane adsorption

作　　者：陈小珍 李美芬[1,2] 曾凡桂[1,2] CHEN Xiaozhen;LI Meifen;ZENG Fangui(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)

机构地区：[1]太原理工大学地球科学与工程系,山西太原030024 [2]太原理工大学煤与煤层气地质山西省重点实验室,山西太原030024

出　　处：《煤炭学报》2022年第7期2678-2686,共9页Journal of China Coal Society

基　　金：国家自然科学基金资助项目(U1910204,41772165,41973077)。

摘　　要：煤与甲烷、二氧化碳等流体作用后的体积膨胀及其机制一直是煤层气地质学和煤与瓦斯突出防治研究中的重要课题之一。以往的研究主要集中在宏观吸附膨胀及变形,并从力学的角度解释其膨胀机制。实际上,煤作为由大分子构成的分子体系,与甲烷、二氧化碳的相互作用是一种分子现象,其膨胀变形的本质应该是分子体系发生了变化,因此揭示煤大分子结构对煤体吸附膨胀的响应特征是认识其机制的基础。应用显微-拉曼光谱法对吸附甲烷前后的8个中煤级煤样(镜质组最大反射率R_(o)=1.08%~1.80%)进行了结构表征,并运用Origin 8.5软件对煤样吸附甲烷前后的拉曼光谱曲线进行了分峰拟合,在此基础上计算了煤样吸附前后的拉曼光谱结构参数。结果表明:原煤和吸附煤的G峰与D峰的峰位差d(G-D)随着煤级的增加有增大趋势,G峰半峰宽(FWHM-G)呈减小趋势,表明在反射率1.08%~1.80%阶段,煤结构有序度和微晶尺寸随煤级增加而逐渐增加;大芳香环(≥6)的相对含量(A_(D)/A_(G))出现先增加后减小的趋势,这是以较大芳香环的生成为主转为向石墨结构生成为主的结果;随着煤级增加,原煤的大芳香环结构中“杂质”(A_(S)/A_(D))及氢化芳环上的C—C的含量(A_(S)/A_(total))均有减小的趋势,反映出煤结构中sp^(2)-sp^(3)杂化烷基碳或氢化芳环逐渐减少,有序度逐渐增加;当R_(o)>1.3%时,吸附煤相对原煤的d(G-D)及A_(D)/A_(G)减少,小芳香环相对含量(A_(GR+VR+VL)/A_(D)),A_(S)/A_(D),A_(S)/A_(total)和FWHM-G增加,表明甲烷吸附变形引起环数较大的芳香环和微晶结构破裂形成较小的芳香环。这一结果对于认识煤大分子结构与甲烷的相互作用机制提供了理论依据。The volumetric expansion of coal with methane,carbon dioxide and other fluids and its mechanism is always one of the important topics in the research of coalbed methane geology and coal and gas outburst prevention.Previous studies focused on macroscopic adsorption expansion and deformation and its explaination from the perspective of mechanics.In fact,as a molecular system composed of macromolecules,the interaction between coal and methane and carbon dioxide is a molecular phenomenon,and the nature of expansion should owing to the change of molecular structure.Therefore,revealing the response characteristics of coal macromolecular structure to adsorption and expansion is the basis for understanding its mechanism.The chemical structure characteristics of 8 medium-rank coal samples(the maximum vitrinite reflectance R_(o)=1.08%-1.80%)before and after methane adsorption were studied by Micro-Raman spectroscopy,and structure parameters were calculated by using Origin 8.5 software before and after methane adsorption.The results show that the band position difference of D and G peak(d(G-D))of both raw and adsorbed coal increase and the full widths at half maximum of G band(FWHM-G)decrease with the increase of coal rank,indicating that the order degree and microcrystalline size of coal structure increases with the increase of coal rank with R o ranging from 1.08%to 1.80%.The relative amount of more ordered rings(A_(D)/A_(G))of coal samples increases first and then decreases,which is the result of the transition from the formation of more ordered aromatic rings(≥6)to the formation of graphite structure.With the increase of coal rank,the“impurity”among the large aromatic rings(A_(S)/A_(D))and the content of C—C structures on hydro-aromatic rings(A_(S)/A_(total))of raw coal have a decreasing trend,indicating that the sp^(2)-sp^(3)carbonaceous structures or C—H on aromatic rings decrease,and the order degree increases.When R_(o)is greater than 1.3%,compared with raw coals,d(G-D)and A_(D)/A_(G)of the adsorbed sample

关 键 词：MICRO-RAMAN 吸附变形 结构演化 中煤级煤 西山煤田 

分 类 号：TD712[矿业工程—矿井通风与安全]