An experimental study on the evolution of aggregate structure in coals of different ranks by in situ X-ray diffractometry
An experimental study on the evolution of aggregate structure in coals of different ranks by in situ X-ray diffractometry
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DOI：
10.1039/c5ay01922b
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发表时间：
2015-10
影响因子：
3.1
通讯作者：
Wenyong Zhang;Shancheng Chen;Fenglin Han;D. Wu
中科院分区：
文献类型：
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作者：
Wenyong Zhang;Shancheng Chen;Fenglin Han;D. Wu
根据地质年代和地区选择不同等级的煤样，利用原位X射线衍射（XRD）光谱研究其骨料结构的热演化。样品在 25–900 °C 范围内以 10 °C min−1 的速率加热。煤样的 XRD 谱显示 20°（λ 波段）处的峰强度明显降低，这表明煤基质中的含氧官能团在较高温度下发生了分解。相比之下，26° 处的峰（所谓的 G 带）变得更尖锐，并移动到更高的角度，这表明随着加热温度的升高，煤的晶粒结构更加有序。值得注意的是，这两个谱带的整体衍射强度在400℃以上强烈减弱，这表明煤中碳质基体的解聚可能导致煤团聚结构松散。低阶煤的初次失重发生在300~500℃范围内，而高阶煤在500℃以上则发生明显的第二次热解反应。此外，这项研究表明，加热温度效应在晶体结构的层间距（d002）和芳香层高度（Lc）的演变中起着关键作用，而芳香层的直径（La）更依赖于煤阶而不是加热温度。
Coal samples of different ranks were selected based on geological ages and regions to investigate their thermal evolution in aggregate structure using in situ X-ray diffraction (XRD) spectroscopy. Samples were heated at a rate of 10 °C min−1 in the range of 25–900 °C. The XRD profiles of the coal samples displayed an evident decrease in intensity of peak at 20° (λ-band), which suggests the decomposition of oxygen-containing functional groups in the coal matrix at higher temperatures. In contrast, the peak at 26° (so-called G-band) became sharper and shifted to higher angles, which suggests a more ordered crystallite structure of coal with increasing heating temperature. Note that the integrally diffracted intensity of these two bands weakened intensely above 400 °C, which suggests that the coal aggregate structure may be loosened due to the depolymerization of the carbonaceous matrix in coal. The primary phase of weight loss for the low-rank coals took place in the range of 300–500 °C, but the high-rank coals had an obvious second pyrolysis reaction above 500 °C. Moreover, this study shows that the heating temperature effect plays a key role in the evolution of the interlayer spacing of the crystalline structure (d002) and height of the aromatic layers (Lc), whereas the diameter of the aromatic layers (La) is more dependent on coal ranks rather than heating temperature.