Study of Bitumoids Extracted from O-Alkylated Brown Coal

Journal of Physics: Conference Series

PAPER • OPEN ACCESS Study of bitumoids extracted from O-alkylated brown coal

To cite this article: K. M. Shpakodraev et al 2021 J. Phys.: Conf. Ser. 1749 012029

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This content was downloaded from IP address 170.106.35.76 on 24/09/2021 at 16:39 IX-IRKSCCEK 2020 IOP Publishing Journal of Physics: Conference Series 1749 (2021) 012029 doi:10.1088/1742-6596/1749/1/012029

Study of bitumoids extracted from O-alkylated brown coal

K. M. Shpakodraev, S. I. Zherebtsov, N. V. Malyshenko and Z. R. Ismagilov

Federal Research Center of Coal and Coal Chemistry, Siberian Branch of Russian Academy of Science,

18 Sovetskiy Ave., 650000, Kemerovo, Russia

E-mail: [email protected]

Abstract. The component composition of bitumen obtained from brown coal of grade 1B of the Tyulganskoye deposit of the South Ural basin was investigated using destructive O- alkylation with n-butanol. The positive effect of alkylating treatment on the bitumen yield is shown. A number of individual compounds were identified by gas chromatography-mass spectrometry in the composition of the studied bitumoids: n-Tetracosanol-1, Docosanoic acid, Tricosanoic acid, Podocarpa-5,8,11,13-tetraen-7-one, 13-hydroxy-14-isopropyl, etc. Among the identified substances, biologically active substances are present in significant concentrations: β-Sitosterol, gamma-Tocopherol, Sugiol, Behenic alcohol, etc.

1. Introduction The rational use of solid fossil fuels is one of the most important problems of our time. One of the most significant positions in solving this problem is occupied by the issue of processing brown coals, which, to the extent of their specific properties, are unprofitable for use in the power industry. However, such a processing method as extraction makes it possible to extract a number of valuable products from brown coals: humic substances, bitumen (mountain wax). Bitumen (raw mountain wax), in turn, consists of a wax and resin part. The wax part is a strategically important product with high demand and value in the world market. With further processing of raw mountain wax by means of resinification and refining, its cost increases significantly. Currently, raw mountain wax and its products are widely used in various industries - from metallurgy to medicine. The resinous component of bitumen, at the moment, is considered a waste product [1-4]. An important aspect of extraction processing is the high bituminous content of brown coals - from 5 to 33%. The bitumen yield depends on a number of factors: the chemical nature of the solvent used; duration of the process; pressure; size of coal fraction; the degree of metamorphism of coal raw materials, etc. The mild conditions of the extraction process make it possible to extract natural components from the coal substance that retain the structural features of the original organic material, and the obtained information on the composition of the extracts is an important element in the development of ideas about the chemical structure and properties of TGI [5, 6]. In addition to such a valuable product as wax, attention is drawn to various biologically active substances contained in significant concentrations, both in the wax itself and in its resinous component [1, 7]. In this regard, a special place is occupied by studies aimed at studying the group and component composition of bitumoids, as well as ways to increase their yield. To date, the most effective way to increase the yield of bitumen, as well as the rock wax itself, is the method of destructive O-alkylation of the organic mass of TGI. Its application allows, while maintaining the same mild conditions, to extract bitumen from brown coal with a yield 2-3 times higher than the yield of bitumen during conventional extraction [8, 9]. In this work, a study of the component composition of bitumen extracted from brown coal (1B) of the Tyulganskoye deposit of the South Ural Basin (TBC) is carried out. This coal, in view of its high bituminous content, is a promising raw material for its extraction processing. The results of technical and elemental analysis of the original coal are shown in Table 1.

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IX-IRKSCCEK 2020 IOP Publishing Journal of Physics: Conference Series 1749 (2021) 012029 doi:10.1088/1742-6596/1749/1/012029

Table 1. Technical and elemental analysis of brown coal,% a d daf daf daf Sample W A V C H H/Catomic (O+N+S), as difference TBC 9.1 21.5 65.9 57.3 6.3 1.3 36.4 Wa – analytical moisture; Ad – ash content per daf; Vdaf – yield of volatile substances; Cdaf – carbon content; C, H, O, N, S – content of carbon, hydrogen, oxygen, nitrogen and sulfur; Hdaf – hydrogen content; daf – dry ash-free state.

2. Methods Alkylation of coal samples (5 g) was performed with n-butanol in the presence of n-heptane (V = 3 100 mL) and orthophosphoric acid H3PO4 (w = 79.9%, ρ = 1.626 g/cm ) at a boiling point of the mixture of 98-103 °C. The process was carried out in a glass flask, with a reflux condenser, with stirring and heating. Parameters of the O-alkylation process: coal - 5 g, n-butanol - 25 mL, orthophosphoric acid 9% in the mixture, process duration 30 min. After O-alkylation residual resins were recovered from coal by means of extraction for 5 h with ethanol-benzene (1 : 1) according to the Gref method. The total yield of bitumoids was 35.7% per daf, which is 21.3% higher than in the extraction with the same solvents under conditions without O-alkylation. Subsequently, according to the method [6, 10], bitumoids were separated into a fraction of waxes and resins (Table 2). Figure 1 shows a scheme for obtaining bitumoids by O-alkylation with fractionation into wax and resins..

Figure 1. Scheme of obtaining bitumoids by O-alkylation to obtain their wax and resin fractions.

IX-IRKSCCEK 2020 IOP Publishing Journal of Physics: Conference Series 1749 (2021) 012029 doi:10.1088/1742-6596/1749/1/012029

Table 2. The yield of extracts from O-alkylated coal,% per daf Process conditions No. Butanol, mL Н3PO4, Duration, h Wax Resins Sum of Eav % in wax and mixture resins О-alkylation 1 16.6 19.2 35.8 2 25 9 0.5 16.5 19.0 35.6 35.7 3 16.7 19.2 35.9 Without Н3PO4 4 11.8 2.8 14.6 5 100 0 3.0 11.3 2.6 14.0 14.4 6 11.5 2.9 14.5

Further studies of bitumen samples were carried out using IR spectroscopy and gas chromatography-mass spectrometry (CMS) methods. The IR spectra were recorded on an Infralum-FT 801 IR Fourier spectrophotometer at a resolution of 4 cm–1 with the accumulation of 16 scans in the range 4000–550 cm–1 in dry KBr. The study of the samples by chromatography-mass spectrometry (CMS) was carried out on an Agilent 6890N instrument with an Agilent 5973 mass-selective detector under the following conditions: capillary column HP-5ms; evaporator temperature - 290 °C; solvent removal - 4 min; split flow – 50:1; helium carrier gas velocity - 1 mL/min; sample volume for analysis - 5.0 μL; programmable increase in the column temperature from 50 °C, with a holding time of 3 min to 280 °C, at a rate of 5 °C min; exposure at 280 °C - 60 min. The content of individual compounds was recorded by the total ionic current. The identification of the component composition of the samples under study was carried out using the NIST-11 and Wiley spectra libraries.

3. Results and discussion From the obtained data of the IR spectroscopic study, it can be seen that all the samples under study are represented by complex multicomponent mixtures of substances that have a similar group composition. Figure 2 shows the IR spectrum of bitumoids obtained by destructive O-alkylation of the organic matter of Tyul'gan brown coal (1B). The assignment of absorption bands was carried out according to the literature data [11-13]. In the spectral data of the sample of the initial bitumen and its resin fraction (Fig. 3) in the region of 3650-3200 cm-1 there are absorption bands characteristic of the stretching vibrations of the OH groups of alcohols and phenols; in the spectrum of the sample of the wax fraction (Fig. 4) these bands are not visible. The absorption bands present in the spectra of the -1 samples in the region of 3000-2800 cm that are stretching vibrations of the CH2 and CH3 groups, in the spectral data of the sample of the wax fraction have the highest intensity, in the data obtained for the resin fraction in the region of ≈ 2850 cm-1 there is a transition of the peak to the shoulder. Absorption bands observed in the 1736 cm-1 region - stretching vibrations of the C = O group in saturated esters and absorption bands observed in the 1730-1710 cm-1 region characteristic of stretching vibrations of C = O groups of aliphatic esters of carboxylic acids, have the highest intensity in the spectral data of the resin fraction. The absorption bands in the range of 1475-1450 cm-1 are related to bending vibrations of CH2 groups, they are clearly visible in the spectra of the initial bitumoid and its wax fraction, but are not observed in the spectra of the resin fraction. Along with this, in the IR spectra of the sample of the resin fraction, absorption bands in the region of 1400-1440 cm-1 are clearly observed, which are characteristic of the bending vibrations of the CH2 group in -CH2-CO- alkane chains. In the range of 1275-1150 cm-1 in the spectrum of the resin fraction, there are absorption bands characteristic of the stretching vibrations of the C-O group of alcohols and phenols; in the spectra of the initial bitumoids and their wax fraction, these bands are not visible. Bands in the

IX-IRKSCCEK 2020 IOP Publishing Journal of Physics: Conference Series 1749 (2021) 012029 doi:10.1088/1742-6596/1749/1/012029

range of 1175-1125 cm-1 are characteristic of plane bending vibrations of 1-, 1,3-, 1,2,3-, 1,3,5- aromatic compounds. They are clearly visible in the spectra of bitumoids and their wax fraction, in the data obtained for the resin fraction, the shoulder is observed. The bands at 717 and 719 cm-1 observed in the spectra of the initial bitumoids and their wax fraction, but absent in the spectrum of the resin fraction sample, are characteristic of pendulum vibrations of methylene groups of long alkane chains.

Figure 2. IR spectrum of a sample of the obtained bitumoids.

Figure 3. IR spectrum of the resin fraction of the obtained bitumoids.

IX-IRKSCCEK 2020 IOP Publishing Journal of Physics: Conference Series 1749 (2021) 012029 doi:10.1088/1742-6596/1749/1/012029

Figure 4. IR spectrum of the wax fraction of the obtained bitumoids.

Subsequently, the obtained samples were studied by gas chromatography-mass spectrometry. As a result of the analysis of bitumoids in their composition, a number of substances were identified, some of which are presented in Table 3.

Table 3. Compounds identified in the composition of bitumoids, with a coincidence in the NIST database of more than 70% Sample Wax Resins Compound name * The relative coincidence Compound name * The coincidence [14] content in the in the NIST [14] relative in the NIST fraction, % database, % content in database, % the fraction, % Dodecenoic acid 1.87 99 Nonanedioic acid 1.84 93 Totarol 2.28 99 n-Heptadecanol-1 0.74 91 Hexadecenoic acid 6.01 99 Hexadecanoic acid 0.82 98 Podocarpa-8,11,13- triene-7β,13-diol, 14- Behenic alcohol 2.45 95 isopropyl- 6.65 99 Phenol, 2-(4- diethylaminophenylim Sugiol 0.82 99 inomethyl)- 1.27 74 n-Tetracosanol-1 8.10 94 1-Heptacosanol 1.39 93 Docosanoic acid 2.03 99 Sugiol 4.96 99 Tricosanoic acid 0.71 99 Behenic alcohol 4.18 90 Podocarpa-5,8,11,13- tetraen-7-one, 13- Tetracosanoic acid 8.89 99 hydroxy-14-isopropyl- 2.55 99

IX-IRKSCCEK 2020 IOP Publishing Journal of Physics: Conference Series 1749 (2021) 012029 doi:10.1088/1742-6596/1749/1/012029

Pentacosanoic acid 1.77 99 17-Pentatriacontene 2.16 99 2-Nonacosanone 0.56 91 Tetracosanoic acid 5.70 99 Hexacosanoic acid 10.10 99 gamma-Tocopherol 1.76 94 1-Hexacosanol 1.19 94 alpha-Tocopherol 1.07 96 β-Sitosterol 1.11 99 Octacosanoic acid 6.75 99 * Carbonic acids are presented in the form of butyl esters.

Particular attention in the composition of bitumoids is attracted by biologically active substances (BAS) [14, 15], among which: Hexacosanoic acid, Ferruginol, γ-Sitosterol, Betulin, Tetracosanoic acid, etc. The total mass yield of biologically active substances after the destructive O-alkylation of coal increased. So, in the resin fraction obtained from the original bitumen, the relative content of Behenic alcohol is 2.28%, and in the resin fraction obtained after O-alkylation is 4.18%; Vitamin E in initial resins 0.31%, in resins after alkylation 1.07%; Behenic alcohol in the wax fraction of the original bitumen 1.89%, in the wax fraction after alkylation 2.45%; Sugiol in initial resins is 0.54%, in resins after alkylation 4.96%. Since the studied bitumoids are a complex multicomponent mixture of various substances, this causes difficulties in the study of the composition of the wax and resin fractions by the CMS method, therefore, a number of unidentified compounds are present in the results of the CMS analysis. In this regard, in the future, the resulting bitumoids and their components will be additionally separated by column liquid chromatography into narrower fractions, which will be investigated by the CMS method.

4. Conclusion The obtained bitumoids are a complex multicomponent mixture of substances, consisting of esters, carboxylic acids, alcohols, aromatic substances, etc. The application of the method of destructive O- alkylation of the organic mass of solid fuels made it possible to significantly increase the yield of bitumen from Tyul'gan brown coal - the yield increased by 21.3%, in comparison with the average bitumen yield under conditions without O-alkylation and amounted to 35.7%. Chromatography-mass spectrometry of the studied samples made it possible to identify a number of individual compounds in their composition: Dodecenoic acid, Totarol, Hexadecenoic acid, Behenic alcohol, Sugiol, Nonanedioic acid, n-Heptadecanol-1, Hexadecanoic acid, alpha-Tocopherol, and others. In the studied samples of bitumoids and their wax and resin fractions, BAS were identified: Hexacosanoic acid, Ferruginol, γ-Sitosterol, Betulin, Tetracosanoic acid, etc. The total mass yield of biologically active substances after the destructive O-alkylation of coal increased. So, in the resin fraction obtained from the original bitumen, the relative content of Behenic alcohol is 2.28%, and in the resin fraction obtained after O-alkylation is 4.18%; Vitamin E in initial resins 0.31%, in resins after alkylation 1.07%; Behenic alcohol in the wax fraction of the original bitumen 1.89%, in the wax fraction after alkylation 2.45%; Sugiol in initial resins 0.54%, in resins after alkylation 4.96%.

Acknowledgments The work was carried out using the equipment of the Center for Collective Use of the Federal Research Center of Coal and Coal Chemistry, Siberian Branch of Russian Academy of Science. Funding: The reported study was funded by RFBR, project number 19-33-90079, and within the framework of the state assignment of ICCMS FRC CCC SB RAS (project АААА-А17- 117041910148-9).

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IX-IRKSCCEK 2020 IOP Publishing Journal of Physics: Conference Series 1749 (2021) 012029 doi:10.1088/1742-6596/1749/1/012029

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