Molecular Characterization of Henan Anthracite Coal

Abstract

A type of Chinese anthracite coal was analyzed by several analytical techniques such as Fourier transform infrared spectrum (FTIR), X-ray photoelectron spectroscopy (XPS), solid-state 13C nuclear magnetic resonance spectrum (NMR), and high-resolution transmission electron microscopy (HRTEM). Combining the experimental data, a reasonable macromolecular model of anthracite coal (C258H172O12N4S) was proposed. HRTEM results showed that the anthracite coal mainly contained aromatic laminates with different lattice sizes, with the length distribution characterized as 35.0% (<5.5 Å), 17.5% (5.5–7.4 Å), 22.5% (7.5–11.4 Å), and 10% (11.5–14.4 Å). The FTIR analysis suggested that ether, hydroxyl, and carbonyl groups were the main oxygenated functionalities. The ratio of these groups was approximately 4:3:3, which was consistent with the results of the XPS. On the basis of the rich analytical data, a three-dimensional molecular representation of the anthracite coal was constructed. Then, the properties of the model like NMR were simulated and exhibited a good agreement with the experimental spectrum in peak ranges and composition. The molecular model obtained in this work is useful for further studying the reaction mechanisms during the anthracite utilization processes, and the methodology adopted here can be extrapolated to other coal representations.

Physiochemical structure of semicoke derived from co‐carbonization of coal and sawdust blends

“…There are four types of sulfur on the surface of semicokes including sulfides (163.3 eV), thiophenes (164.1 eV), sulfoxides (166.0 eV), and sulphonic acids and sulfates (169.0 eV). The sulfides and sulfates are the dominant sulfur species in the semicokes, which are consistent with the results obtained by Liu et al 25 The content of the sulfides and sulfoxides in the semicoke slightly decreases, while the contents of thiophenes and sulfates in the semicokes slightly increase as the blending coal replaced by sawdust is increased from 0 to 20 wt%. However, four types of sulfur on the surface of semicokes derived from sawdust are not detected due to its lower sulfur content in sawdust since the sulfur content in sawdust is only 0.32 wt% on dry basis.…”

“…Ortho-oxyaromatic protonated carbon, ortho-oxyaromatic branched carbon, aromatic protonated carbon, aromatic carbon linked to CH 3 group in the α position, aromatic carbon bridging two aromatic rings, and quaternary aromatic carbon in the α position to oxygen atom are detected in the range of 93 to 171 ppm. 25 The fractions of the aromatic carbons in SBC-0, SBC-10, SBC-20, and SD semicoke are in sequence as 91.26%, 88.02%, 67.09%, and 55.93%. The spectra show that the aliphatic carbons, such as aliphatic carbon in the α position to OH and aliphatic carbon (CH 3 type) in the α position to aromatic ring, corresponding to the peaks at approximately 70 and 19.8 ppm, are increased, 49 while the aliphatic carbon that appears at 36 ppm in these semicoke decrease as the SD increase in these sawdust/…”

“…The bands at 2260 and 2230 cm −1 are respectively assigned to alkyne and CO 2. 25,37 The band at 1980 cm −1 belongs to alkene. 38 The band at 1720 cm −1 is ascribed to the stretching vibration of C O, which is mainly derived from the carbonyl ( C O) and carboxyl functional groups ( COOH).…”

“…The NMR spectrum can be divided into three major regions: aliphatic carbons (0-93 ppm, Cali), aromatic carbons (93-171 ppm, Car), and carbons linked to oxygen (171-220 ppm). 25,45,48 The semicokes are dominated by aromatic carbon peak that is assigned to the orthooxyaromatic branched carbon and aromatic protonated carbon in the semicoke. Ortho-oxyaromatic protonated carbon, ortho-oxyaromatic branched carbon, aromatic protonated carbon, aromatic carbon linked to CH 3 group in the α position, aromatic carbon bridging two aromatic rings, and quaternary aromatic carbon in the α position to oxygen atom are detected in the range of 93 to 171 ppm.…”

“…It was reported that carbon originated from biomass may adhere to the surface of coal, and inhibited the evolution of volatile matter, and then promoteed the mesophase formation 22 ; Hydrogen in biomass may act as the fluidity enhancers to promote the formation of coal plasticity, and favored for developing an optical anisotropic mosaic 14,18,23 ; Higher content of oxygen in biomass not only inhibits the formation of mesophase, but also prevents the development of the anisotropic structure. 19,[24][25][26] The microporosity of the semicoke derived from biomass/coals co-coking was also increased by the catalytic activity of the alkali and alkaline earth metal (AAEMs). 27,28 The incorporation of biomass into the blending coal may also significantly affect the physiochemical structure of the semicoke derived from co-carbonization of biomass/coal blends such as the functional groups, carbon structure, surface morphologies, and optical texture.…”