Specific Features of the Structure of Various Coal Ranks at the Nano Level

Structural factors and functions of radial distribution of atoms of different coal ranks have been calculated by X-ray diffraction analysis. This made it possible to establish that the main structural component is the clusters with graphite-like packing of atoms. The predominant size of these clusters (calculated from the peaks of small-angle X-ray scattering at 5° in CoK_α-radiation) for coals with a carbon content of 83--95 % is within 2--3 nm. Fossil coal is an amorphous carbonaceous substance consisting of polymorphic modifications in the sp²- and sp³-states. According to the results obtained using Raman scattering spectroscopy, the physical properties of amorphous natural coals are strongly dependent on the ratio of sp²- and sp³-hybridization of atomic orbitals. Moreover, studies have shown that the carbon atoms of the coal matrix in the sp²-state are represented by both aromatic and aliphatic conjugated chain fragments. It was found that the degree of ordering in rank LF coals is higher than in coals of a higher stage of metamorphism. This is possible if the hydrocarbon matrix in rank LF coals can be represented as a polymer consisting of conjugated chains with periodicity. With an increase in the stage of coal metamorphism, starting with coal rank G, the transformation of the coal structure occurs with a violation of the periodicity of the conjugated fragments of the polymer matrix connecting graphite-like clusters, a decrease in their length, and an increase in randomness in their arrangement

Литература

[1] Franklin R.E. The interpretation of diffuse X-ray diagrams of carbon. Acta Cryst., 1950, no. 3, pp. 107--121. DOI: https://doi.org/10.1107/S0365110X50000264

[2] Hirch P.B. Structural model of coals. Proc. Res. Conf. on Science in Use of Coal, Sheffild, 1958, p. 29.

[3] Warren B.E. X-ray diffraction. Addison-Wesley Publishing Company, 1969, pp. 251--254.

[4] Kasatochkin V.I., Larina N.K. Stroenie i svoystva prirodnykh ugley [Composition and structure of natural coal]. Moscow, Nedra Publ., 1975.

[5] Malyshev Yu.N., Trubetskoy K.N., Ayruni A.T. Fundamental’no prikladnye metody resheniya problemy metana ugol’nykh plastov [Fundamental applied methods for solving coalbed methane problem]. Moscow, Akad. gornykh nauk Publ., 2000.

[6] Lu L., Sahajwalla V., Kong C., et al. Quantitative X-ray diffraction and its application to various coals. Carbon, 2001, vol. 39, iss. 12, pp. 1821--1833. DOI: https://doi.org/10.1016/S0008-6223(00)00318-3

[7] Takagi H., Maruyama K., Yoshizawa N., et al. XRD analysis of carbon stacking structure in coal during heat treatment. Fuel, 2004, vol. 83, iss. 17-18, pp. 2427--2433. DOI: https://doi.org/10.1016/j.fuel.2004.06.019

[8] Wertz D.L., Quin J.L. Wide angle X-ray scattering study of the layering in three of the Argonne premium coals. Fuel, 2000, vol. 79, no. 15, pp. 1981--1989. DOI: https://doi.org/10.1016/S0016-2361(00)00026-0

[9] Marsh H. A tribute to Philip L. Walker. Carbon, 1991, vol. 29, iss. 6, pp. 703--704. DOI: https://doi.org/10.1016/0008-6223(91)90004-3

[10] Marsh N., Rodrigues-Reinoso F. Activated carbon. Elsevier, 2006.

[11] Rus’yanova N.D. Uglekhimiya [Coal chemistry]. Moscow, Nauka Publ., 2003.

[12] Rus’yanova N.D., Popov V.K., Butakov V.I. [Parameters, characterizing changes in structure of coal main organic mass in metamorphism process]. Sb. nauch. tr. "Struktura i svoystva ugley v ryadu metamorfizma" [Coll. Sci. Works "Structure and Properties of Coals in Metamorphism"]. Kiev, Naukova dumka Publ., 1985, pp. 16--42 (in Russ.).

[13] Butakova V.I. Polyene model of coal structure. Coke Chem., 2015, vol. 58, no. 4, pp. 129--137. DOI: https://doi.org/10.3103/S1068364X15040055

[14] Alekseev A.D., Zelinskaya G.M., Il’nsky A.G., et al. Atomic structure of fossil coals. Physics and Technology of High Pressures, 2008, vol. 18, no. 3, pp. 35--54.

[15] Kitaygorodskiy A.I. Rentgenostrukturnyy analiz melkokristallicheskikh i amorf-nykh tel [X-ray diffraction analysis of fine-crystalline and amorphous bodies]. Mosсow, Leningrad, ITTL Publ., 1952.

[16] Skryshevskiy A.F. Rentgenografiya zhidkostey [Radiography of liquids]. Kiev, KGU Publ., 1966.

[17] Suggate R.P., Dickinson W.W. Carbon NMR of coals: the effects of coal type and rank. Int. J. Coal Geol., 2004, vol. 57, iss. 1, pp. 1--22. DOI: https://doi.org/10.1016/S0166-5162(03)00116-2

[18] Petersen T., Yarovsky I., Snook I., et al. Microstructure of an industrial char by diffraction techniques and Reverse Monte Carlo modelling. Carbon, 2004, vol. 42, iss. 12-13, pp. 2457--2469. DOI: https://doi.org/10.1016/j.carbon.2004.04.037

[19] Han Y., Wang J., Dong Y., et al. The role of structure defects in the deformation of anthracite and their influence on the macromolecular structure. Fuel, 2017, vol. 206, pp. 1--9. DOI: https://doi.org/10.1016/j.fuel.2017.05.085

[20] Zhang Z., Kang Q., Wei S., et al. Large scale molecular model construction of Xishan bituminous coal. Energy Fuels, 2017, vol. 31, iss. 2, pp. 1310--1317. DOI: https://doi.org/10.1021/acs.energyfuels.6b02623

[21] Friedel R.A., Carlson G.L. Difficult carbonaceous materials and their infra-red and Raman spectra. Reassignments for coal spectra. Fuel, 1972, vol. 51, iss. 3, pp. 194--198. DOI: https://doi.org/10.1016/0016-2361(72)90079-8

[22] Tuinstra F., Koenig J.L. Raman spectrum of graphite. J. Chem. Phys., 1970, vol. 53, iss. 3, pp. 1126--1130. DOI: https://doi.org/10.1063/1.1674108

[23] Xu J., Tang H., Su S., et al. A study of the relationships between coal structures and combustion characteristics: the insights from micro-Raman spectroscopy based on 32 kinds of Chinese coals. Appl. Energy, 2018, vol. 212, pp. 46--56. DOI: https://doi.org/10.1016/j.apenergy.2017.11.094

[24] Liu X., Song D., He X., et al. Coal macromolecular structural characteristic and its influence on coalbed methane adsorption. Fuel, 2018, vol. 222, pp. 687--694. DOI: https://doi.org/10.1016/j.fuel.2018.03.015

[25] Alekseev A.D., Ulyanova E.V., Trachevskiy V.V., et al Application of nuclear magnetic resonance and Raman scattering methods for studying genesis of natural carbon nanomaterials structure. Fizika i tekhnika vysokikh davleniy [High Pressure Physics and Technology], 2010, vol. 20, no. 3, pp. 126--139 (in Russ.).

[26] Ulyanova E.V., Molchanov A.N., Prokhorov I.Y., et al. Fine structure of Raman spectra in coals of different rank. Int. J. Coal Geol., 2014, vol. 121, pp. 37--43. DOI: https://doi.org/10.1016/j.coal.2013.10.014

[27] Ferrari A.C., Robertson J. Interpretation of Raman spectra of disordered and amorphous carbon. Phys. Rev. B, 2000, vol. 61, iss. 20, pp. 14095--14107. DOI: https://doi.org/10.1103/PhysRevB.61.14095