Raman Spectroscopy for the characterization of the macromolecular structure of Highveld coals (South Africa)

IF 5.6 2区 工程技术 Q2 ENERGY & FUELS
Itumeleng V. Matlala , Ofentse M. Moroeng , Stavros Kalaitzidis , Nicola J. Wagner
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引用次数: 0

Abstract

Industrial applications of coal rely on understanding its macromolecular structure, which is primarily controlled by coal type and rank. The present study assessed five (5) samples from different collieries extracting coal from the No. 4 Seam of the Highveld Coalfield and their float products, produced at relative densities (RD) of 1.7 and 1.9 g/cm3. The aim was to assess changes in maceral composition and coal quality following the density fractionation, and to use Raman Spectroscopy to compare differences in macromolecular structures between the parent samples and the float products. Raman parameters were also determined for specific macerals, i.e., semifusinite and collotelinite. Mean random vitrinite reflectance (%RoV) values for the studied coals range between 0.57 and 0.60% (medium rank D/C bituminous) and the parent coals are inertinite-rich (70.3 to 88.7 vol% mmf), enriched in semifusinite and inertodetrinite. Following density fractionation, reactive macerals (a combination of liptinite, vitrinite, and reactive semifusinite) are enriched in the float products (designated by “F”), specifically in the products obtained at the 1.7 RD. In comparison, the proportion of inert macerals is higher in the F1.9 samples. These differences in maceral composition are reflected in the Raman spectra and parameters. Although the G and D1 bands for the parent coals and F1.9 samples are similar, these bands are narrower than for the F1.7 samples, indicative of greater aromaticity. The G FWHM values for the F1.9 samples are comparable to those for the parent coal samples, and lower than for the F1.7 samples. This reflects larger differences in maceral composition between the parent coals and the F1.7 samples. In contrast, the D1 FWHM values for the float products, particularly the F1.7 samples, are slightly higher than the parent coals, reflecting a disordered aromatic character mainly related to the presence of aliphatic chains. The Raman spectra for the F1.7 samples are more like that for collotelinite. In contrast, the Raman spectra and parameters (G and D1 FWHM) for the F1.9 samples are more comparable to semifusinite. Thus, the increased aliphaticity for the F1.7 samples is attributed to the relative enrichment of reactive macerals, whereas higher aromaticity for the F1.9 samples reflects a larger proportion of inert macerals. Raman spectroscopy expanded on the petrographic data by interrogating the macromolecular structure of the isorank Highveld coals and their float products. This may assist in predicting the behaviour of the coals during industrial applications (i.e., liquefaction, gasification, combustion, and carbon fibre production).

Abstract Image

Abstract Image

利用拉曼光谱表征高维尔德煤(南非)的大分子结构
煤炭的工业应用依赖于对其大分子结构的了解,而大分子结构主要受煤炭类型和等级的控制。本研究评估了来自不同煤矿的五 (5) 个煤样,这些煤样采自 Highveld 煤田的 4 号煤层,以及在相对密度 (RD) 为 1.7 和 1.9 g/cm3 时生产的浮选产品。目的是评估密度分馏后大分子成分和煤炭质量的变化,并使用拉曼光谱比较母体样本和浮选产品之间大分子结构的差异。此外,还测定了特定大分子物质(即半浮石和胶凝石)的拉曼参数。所研究煤炭的平均随机玻璃光泽反射率(%RoV)值介于 0.57 和 0.60% 之间(中级 D/C 烟煤),母煤富含惰性石灰岩(70.3 至 88.7 vol% mmf),富含半富集石和惰性铁石棉。经过密度分馏后,浮选产物(用 "F "表示)中富含活性大分子(锂辉石、矾石和活性半锂辉石的组合),特别是在 1.7 RD 条件下获得的产物中。相比之下,F1.9 样品中惰性巨矿的比例较高。拉曼光谱和参数反映了这些大分子成分的差异。虽然母煤和 F1.9 样品的 G 和 D1 波段相似,但这些波段比 F1.7 样品窄,表明芳香度更高。F1.9 样品的 G FWHM 值与母煤样品相当,低于 F1.7 样品。这反映出母本煤和 F1.7 样品之间的宏观成分差异较大。相比之下,浮游产物(尤其是 F1.7 样品)的 D1 FWHM 值略高于母煤,这反映了主要与脂肪族链的存在有关的无序芳香特性。F1.7 样品的拉曼光谱更接近于胶石的拉曼光谱。相比之下,F1.9 样品的拉曼光谱和参数(G 和 D1 FWHM)更接近半透明石。因此,F1.7 样品脂肪族含量的增加是由于活性巨矿物的相对富集,而 F1.9 样品芳香族含量的增加则反映了惰性巨矿物比例的增加。拉曼光谱通过研究异侧翼高维尔德煤及其浮游产物的大分子结构,扩展了岩石学数据。这可能有助于预测煤炭在工业应用(即液化、气化、燃烧和碳纤维生产)过程中的行为。
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来源期刊
International Journal of Coal Geology
International Journal of Coal Geology 工程技术-地球科学综合
CiteScore
11.00
自引率
14.30%
发文量
145
审稿时长
38 days
期刊介绍: The International Journal of Coal Geology deals with fundamental and applied aspects of the geology and petrology of coal, oil/gas source rocks and shale gas resources. The journal aims to advance the exploration, exploitation and utilization of these resources, and to stimulate environmental awareness as well as advancement of engineering for effective resource management.
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