变质程度高、碳含量高的无烟煤是生产活性炭的主要煤种。无烟煤的结构特征在其材料方向开发利用中起着决定性作用,可以通过化学氧化的方法对煤的结构进行定向优化。以云南昭通地区天然高碳低灰无烟煤为原料,采用硝酸/硫酸酸浸氧化法制备了氧化无烟煤。使用X射线衍射(XRD)、拉曼光谱(Raman)和衰减全反射红外光谱(ATR-FTIR)对产物进行结构和谱学特征研究。结果表明,无烟煤具有介于石墨和无定形碳之间的类石墨微晶结构;相较于烟煤和褐煤,无烟煤微晶堆叠高度(Lc)、微晶直径(La)较大,结构有序度介于低变质煤和石墨之间。无烟煤的氧化经过两个主要过程,微晶片层边缘被氧化卷曲破坏引起片层平均直径La减小。新的C=O键在片层边缘生成,硫酸与硝酸进入片层边缘层间域。H_2SO_4和HNO_3作为插层剂进入无烟煤微晶碳中,层间距d(002)由原煤的0.351nm增长到了0.361nm。原有的微晶片层被剥离开,微晶片层的堆叠层数,由6下降到4.5,Raman光谱中ID1/IG相较于原煤增大(1.9→2.0),G峰的半峰宽(FWHM)升高(63→68),D2峰的强度提高(10.26→13.78)。大量新的—C—O—,C=O和—NO_2键生成,富氧程度参数大幅提高(0.11→0.42)。经过混酸处理的氧化无烟煤,芳香度fa提高,结构有序度降低,新增了大量反应活性点,在无烟煤基多孔炭材料开发等领域具有很大潜力。
With high degree of metamorphism and carbon content,anthracite is commonly used for activated carbon.The structural properties of anthracite play a decisive role in its materialization,while with chemical oxidation,anthracite structure can be purposefully improved.The anthracite oxide was prepared via acid leaching and oxidizing,using high carbon content and low ash content anthracite from Zhaotong,Yunnan Province,China.The structural and spectroscopy characteristics of anthracite and anthracite oxide were acquired with X-ray diffraction(XRD),Raman spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy(ATR-FTIR).The results show that crystallites in anthracite have intermediate structures between graphite and amorphous.Compared with bitumite and lignite,its structure order degree lies between graphite and low metamorphic coals with relatively high average diameter of coal crystallites(La)and average height of coal crystallites(Lc).The process of anthracite oxidation can be modeled in two steps,the edge of crystal was curled and destroyed with strong oxidation,with the generationof C=O groupandintercalation ofHNO_3/H_2SO_4 into the edge layers,leading to the reducing of lateral sizes;HNO_3/H_2SO_4 were continually intercalated into crystals,resulted in the increase of interlayer spacing(d(002))from 0.351to0.361 nm,and the number of stacked layers dropped to 4.5from 6due to exfoliate.ID1/IGin Raman spectroscopy increased from 1.9to 2.0,with full width at half maximum(FWHM)of G bond and intensity of D2 bond increasing from 63 to 68and10.26 to 13.78.Numbers of new —C—O—, C =O,—NO_2 groups generated,leading to the decrease of oxygen-containing functional groups content from 0.11 to 0.42.After HNO_3/H_2SO_4 oxidation,the aromaticity(fa)of anthracite oxide increases,with the decrease of structure order degree and more-over a lot of active reaction sites generates in the process.The oxidation of anthracite enables anthracite has great potential in