Three lignites were subjected to sequential thermal dissolution using cyclohexane, methanol, and ethanol as the solvent to acquire soluble fractions (SFs). Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC x GC/TOF MS) was used to separate and reveal complex molecular composition of SFs. Low polar compounds such as chain alkanes (CAs) and arenes were enriched by cyclohexane. Strong polar compounds like phenols were concentrated by methanol, and partial phenols and CAs were also detected in the ethanol extracts. Meanwhile, organic nitrogen compounds (ONCs) and organic sulfur compounds (OSCs) such as pyridines, quinolines and thiophenes were identified in SFs. In all SFs, pyridines have the highest relative abundance, followed by quinolines compared with other ONCs, and thiophenes were only detected in cyclohexane and methanol SFs. In addition, halogen-containing compounds reflecting the geochemical characteristics of lignite were also detected, and their total relative abundances were 0.544%, 1.591% and 5.101% in the SFs of Shengli (SL), Xiheishan (XHS), and Xiaolongtan (XLT), respectively, which provided evidence for the evolution of coal. Two unsupervised analysis methods, hierarchical cluster analysis and principal components analysis, were efficient in clustering components according to molecular characteristics, and visualized detailed similarities and differences among the compounds in SFs.

It is of great practical importance to study the composition of coal’s organic matter in order to develop new and improved technologies for processing solid fuel, with the production of liquid fractions, hydrocarbon gases, and carbon residues. In the present work, 20 Russian and Mongolian coals of six different grades, at different metamorphic stages, undergo technical, petrographic, and chemical analysis. Thermogravimetric analysis is used to study the decomposition of coal as a function of its properties and metamorphic development. Correlations between Russian and Mongolian coals are established in terms of their chemical and technological properties, thermal decomposition, and the liberation of volatile fractions.

Представлены результаты химического, технического и петрографического анализа образцов углей разной стадии углефикации, отобранных на различных месторождениях России и Монголии. С применением метода 13C ЯМР-спектроскопии в твердом теле с использованием техники кросс-поляризации и вращения образца под магическим углом (CP/MAS 13C ЯМР) изучены особенности молекулярного строения углеродного каркаса органической массы, установлены существенные различия в строении поликонденсированных ароматических структур, сделана оценка в соотношении пери- и катаконденсированных ароматических ядер в зависимости от степени углефикации. Выполнен корреляционный анализ, установлены взаимосвязи между различными химико-технологическими параметрами углей и показателями их молекулярного строения. Наиболее тесная связь существует между степенью ароматичности углей, долей периконденсированных структур, выходом летучих веществ и коэффициентом отражения витринита. Установленные особенности молекулярного строения органической массы углей и выявленные регрессионные зависимости могут служить физико-химической основой выбора углей для получения поликонденсированных ароматических веществ как сырья для производства углеродных материалов. The results of chemical, proximate and petrographic analysis of coal samples at different coalification stages from various deposits in Russia and Mongolia are presented. Features of the molecular structure of the carbon framework in the organic matter were studied by the solid-phase 13C NMR spectroscopy using the cross polarization with magic angle spinning (CP/MAS). Significant differences in the structure of polycondensed aromatic nuclei were revealed, and the ratio between the pericondensed and catacondensed cycles depending on the degree of coalification was assessed. Correlation analysis has been carried out and the relationships between various chemical technological parameters of coals and the indicators of their molecular structure were established. The strongest relationships have been revealed between the aromaticity factor of coals, the fraction of carbon in pericondensed structures, the yield of volatile substances and the reflectance of vitrinite. The identified features of the molecular structure of the organic coal matter and the obtained regression dependences can serve as the physicochemical basis when selecting coals for obtaining polycondensed aromatic substances for the production of carbon materials.

Three biomass (rice straw, rice husk and wheat straw) and three coal samples (lignite, subbituminous coal and bituminous coal) were extracted via a thermal dissolution (TD) process, and the TD extracts were treated by catalytic hydrogenation to obtain reaction products. To reveal the similarity in molecular information among the samples and elucidate their chemical reactivity, four machine learning algorithms were applied to analyze the Fourier transform infrared spectra of both TD extracts and catalytic hydrogenation products. Functional groups were used as variables and the difference in peak area can be treated as the basis for sample classification. Aromatic CH, COC, aliphatic CH2 or CH3 and aromatic CO or CC bonds were the main characteristic variables in principal component analysis algorithm to classify biomass- and coal-derivated samples. These samples were also grouped into four clusters by hierarchical clustering analysis algorithm according to the similarity and difference in the distribution of functional groups. For artificial neural network algorithm, aliphatic CH and OH bonds are the most important variables to classify these samples into four groups, and aromatic CH, OH, and COC groups are the main variables contributed to the classification trees in random forest algorithm. Machine learning algorithms will provide methodological guidance for the data mining of the spectra of complex organic systems.

The chemical composition, structural and plastometric properties of different-ranked coals from Mongolia deposits were studied. The non-isothermal iso-conversion Ozawa–Flynn–Wall and Friedman model-free methods were used to assess kinetic parameters and to differentiate decomposition steps. Key peculiarities of the pyrolysis kinetics of brown and bituminous coals were revealed and discussed in terms of the composition and plastometric properties. Brown coal was shown to undergo three decomposition steps with ever increasing activation energy as temperature increased because of the decomposition of thermally more and more stable molecular fragments. The pyrolysis of bituminous coals occurred in four steps, the activation energy having extreme mode of temperature dependence. An important new finding was that the temperature range of the second, major pyrolysis step well corresponded to that between the softening and re-solidification temperatures according to Gieseler plastometry. The yield and composition of the pyrolysis products obtained under isothermal conditions were also characterized depending on coal rank and temperature, and the ways for qualified utilizations were offered.

С применением комплекса методов - ИК-спектроскопии, рентгенофазового анализа, кинетики набухания в растворителях и сорбции молекулярного йода - определены особенности молекулярного и надмолекулярного строения бурых и каменных углей ряда метаморфизма. Установлены связи надмолекулярного строения углей с показателями молекулярного состава, рассмотрены эволюция структуры углей в ряду метаморфизма и механизмы транспорта молекул растворителей в объем органической массы различных углей. The features of the molecular and supramolecular structure of brown and bituminous coals at different metamorphisms stages have been determined using a complex of methods: IR spectroscopy, X-ray diffraction, the kinetics of swelling in solvents, and sorption of molecular iodine. The relations of the supramolecular structure of coals with the indicators of molecular composition are established, the evolution of coal structure in the series of metamorphism, the mechanisms of transport of solvent molecules into the volume of the organic mass of various coals are considered.

The features of the molecular and supramolecular structure of brown and bituminous coals at different metamorphisms stages have been determined using a complex of methods: IR spectroscopy, X-ray diffraction, the kinetics of swelling in solvents, and sorption of molecular iodine. The relations of the supramolecular structure of coals with the indicators of molecular composition are established, the evolution of coal structure in the series of metamorphism, the mechanisms of transport of solvent molecules into the volume of the organic mass of various coals are considered.

The molecular structure characteristics of brown and hard coals of the metamorphism series were determined using IR spectroscopy. Based on the data of X-ray diffraction analysis and the kinetics of swelling in solvents, their supramolecular structure and the mechanism of molecular diffusion in the organic mass of coals were studied. Relationships between the supramolecular structure and molecular composition indices were established, and the structure evolution in the series of coal metamorphism was considered. It was found that tetrahydrofuran and quinoline molecules penetrated into the bulk of the organic mass of most coals by molecular Fickian diffusion complicated by steric hindrances of the microporous structure.

The team has studied the relationship between the ability of the coals to be dissolved in crude anthracene oil and their composition. The coal samples taken from different deposits in Russia and Mongolia were characterized by different stages of metamorphism and tested by the Fourier transform infrared spectroscopy and Carbon-13 nuclear magnetic resonance. The data of a correlation analysis enabled us to find out that an amount of aromatic structures in coal macromolecules provided the main influence on the thermal dissolution of the coals. The middle-rank coals had the highest rates of coal organic matter transfer to liquid products. The data showed that the dissolution process was accompanied by destruction of weak bonds among aliphatic groups. The amount of methylene groups in the aliphatic part of coal macromolecules had a direct impact on conversion of the coal organic matter into soluble products.

Two coal samples in the same mine but different coal seams, soft coal and hard coal, were subjected to a parallel thermal dissolution process using two organic solvents to obtain four soluble portions (SPs). A preparative high performance liquid chromatography (prep-HPLC) with a fraction collector was introduced to obtain twenty-eight fractions from the SPs. Both gas chromatograph/mass spectrometry (GC/MS) and Orbitrap-MS with a collision cell were employed to elucidate the molecular structure of soluble species. Some heavy aromatic compounds in SPs not identified by GC/MS were detected in fractions, indicating that the off-line prep-HPLC is of perfect separation and enrichment ability, and can improve the reliability of analytical data. In addition, to preferably elucidate the difference in composition of compounds between the two coals, the possible fragmentation pathways in the collision cell were proposed. Such accurate identification will provide theoretical guidance for the efficient utilization of coals in the same mine but different coal seams, and the safety guidance to avoid mine accidents generated by the inconsistence in coal seams.

The dissolution of bituminous coal at mild temperature was studied using a variety of commercially available coal- and petroleum-derived hydrocarbon fractions, hydrorefined derivatives and blends as solvents. The chemical and molecular composition of the coal, solvents and extracts were characterized by chemical and group analyses, and by IRFT, 1H NMR, GC-MS and liquid chromatography. Low volatile solvents like highly aromatic coal tar (CT), its anthracene fraction (AFCT), petroleum-derived solvent (HGOCC) and binary blends were found to exhibit high performance for coal dissolution into quinoline solubles (to 79‒82%), and the yields of gases being no more than 0.5%. The extracts obtained using CT and AFCT solvents represented pitch-like matter consisting of rarely substituted aromatic molecules with 4‒5 condensed rings. HGOCC extract was much less aromatic, the aromatic rings being highly substituted with fairly large alkyl substituents. The blended solvents yielded more extracts, and their molecular indexes were average between those obtained with each solvent separately. A remarkable finding was that the extracts obtained were characterized by significantly lower content of benzo(a) pyrene (BaP) compared to solvents used, its content further decreased as the time of coal dissolution increased.

The production of many important carbon materials is currently based on the use of aromatic fractions of coal tar - a minor by-product in the production of metallurgical coke for the needs of ferrous metallurgy. Innovations to reduce the consumption of expensive metallurgical coke in blast furnace smelting and the priority development of the coke-free methods of steel production lead to a reduction in the output of coke-chemical products, which destabilizes the prospects for the production of important carbon materials, including those necessary for ferrous and non-ferrous metallurgy. The relevance of creating alternative methods for obtaining aromatic feedstock is substantiated. The potential of low-temperature coal processing by its thermosolvolysis with the production of concentrates of aromatic substances is shown. The possibility of their use as the raw material in the production of carbon anodes for the process of aluminum electrolysis is demonstrated.

The chemical composition, structural and plastometric properties of typical different-ranked coals from Mongolia deposits were studied. The non-isothermal iso-conversion Ozawa-Flynn-Wall method was used to assess kinetic parameters and to differentiate decomposition steps. Key peculiarities of the pyrolysis kinetics of brown and bituminous coals were revealed and discussed in terms of the composition and plastometric properties of coals. Brown coal was shown to undergo three decomposition steps with ever increasing activation energy as temperature increased because of the decomposition of thermally more and more stable molecular fragments. The pyrolysis of bituminous coals occurred in four steps, the activation energy having an extreme mode of temperature dependence. An important new finding was that the temperature range of the second, major pyrolysis step well corresponded to that between the softening and resolidification temperatures according to Gieseler plastometry, so that the decomposition of bituminous coals at the second step proceeded in a fluid-like medium, moreover, with constant activation energy. The yield and composition of the pyrolysis products obtained under isothermal conditions were also characterized depending on coal rank and temperature, and the ways for qualified utiliza tions were offered.

Co-Mo/γ-Al2O3 bimetallic catalyst was prepared by incipient wetness impregnation and the physicochemical properties were obtained by a series of characterization methods. The active components are mainly MoS2 and Co-Mo-S existing on γ-Al2O3, the support. Meanwhile, the activity of catalyst in hydroconversion of four coal-related model compounds (CRMCs), dibenzyl ether, furan, thiophene and quinoline, was investigated. Hydroconversion products were analyzed by gas chromatography/mass spectrometry (GC/MS) and the possible reaction pathways were proposed according to the GC/MS data. Oxygen was removed from dibenzyl ether via the direct cleavage of Calk-O bridge bond to produce benzylium cation followed by the combination with H− to generate toluene. The hydroconversion of furan can be realized by the direct cleavage of Car-O bond and direct hydrogenation, respectively. For thiophene, H+ directly transferred to sulfur atom, leading to the cleavage of Car-S bond to produce H2S and 1,3-butadiene, which abstracted active hydrogen to yield butane. Another indirect desulfurization pathway for thiophene is hydrogenating to form tetrahydrothiophene and C–S bond cracking to produce butane. Hydroconversion of quinoline started with either N-ring or benzene ring, and the first one was the main pathway.

The bituminous coal was extracted with different industrial solvents like coal tar (CT), heavy cycle oil (HCO) and with their blends to determine the influence of solvent type on the extract yield, composition, thermal behavior, properties such as solubility to toluene and quinoline. The extracts obtained at 380 °C represented pitch-like solid matter with the softening points of 72–127 °C depending on the solvent used. They were characterized using the elemental and group analysis, FTIR spectroscopy, TG-DTG thermogravimetry and liquid chromatography for benzo(a)pyrene concentration. Also, maltene fractions of some extracts were studied by GC–MS. The results showed coal dissolution and the properties of the extracts to differ greatly depending on the solvent used. Coal tar was more favorable solvent for coal dissolution than HCO. Good correlation between the extract aromaticity and the content of the toluene insolubles was observed. The maltene fractions of the extracts obtained with CT and CT blended with HCO consisted mainly of polycyclic aromatics, and that obtained with the HCO contained also large amount of aliphatic compounds. It was found that the amount of the carcinogenic benzo(a)pyrene (BaP) in the toluene soluble fractions of the extracts were different depending on the solvents used for extraction. The remarkable result was that the BaP concentrations in all extracts were much lower than in the solvents used.

•Structure parameters, δ and B, of 19 coals are calculated via simplified formulas.•Coals in the liquefaction zone exhibit high conversion rates and oil yields.•Coal structure-chemical index effectively predict the performance of liquefaction.

The efficiency of the dissolution of bituminous coal at moderate temperature to produce quinoline-soluble substances was studied using commercially available coal tar (CT), its anthracene fraction (AFCT), heavy coal semicoking tar (HCST), heavy gas oil from catalytic cracking of petroleum (HGOCC), their binary blends, as well as tetralin (for comparison) as solvents. The chemical and molecular compositions of the coal, solvents, and the extracts obtained were characterized in detail by chemical and group analyses, FTIR spectroscopy, liquid chromatography, analysis by means of gas chromatography-mass spectrometry. The highly aromatic CT, AFCT, low aromatic HGOCC solvents, binary blends of these solvents and hydrogen donor tetralin showed high performance for coal dissolution at 380 degrees C in the quinoline-soluble substances, the yields of gases being no more than 0.6 %. The extracts obtained with CT and AFCT solvents represented highly aromatic pitch-like matter with rarely substituted aromatic rings. The extract obtained with the HGOCC solvent was characterized by lower aromaticity, the aromatic nuclei being highly substituted with fairly large alkyl fragments. The blended solvents yielded more extracts whose structural parameters were intermediate between those obtained with each solvent separately. Heavy semi-coking HCST tar showed no dissolving ability because of the high content of phenolic hydroxyls. The concentration of benzo(a)pyrene (BaP) in the toluene-soluble fractions of the extracts obtained was much lower than that in the solvents used, and decreased as the coal dissolution time increased, thus indicating BaP conversion.

The thermolysis of Mongolian coals of different ranks was studied using thermal analysis (TG/DTG). The stepwise decomposition under conditions of programmed heating to 1000°C in an atmosphere of argon was found. The kinetic parameters of pyrolysis were determined based on thermogravimetric analysis with the use of model-fitting (Coats–Redfern) and model-free (Ozawa–Flynn–Wall) calculation methods. Changes in the activation energy with the degree of decomposition of the organic matter of coals of different ranks were established. A kinetic compensation effect was revealed, which was, probably due to the multicomponent composition of coals.

Russia, China and, Mongolia are among the countries having large reserves of coals which are traditionally utilized mainly as a fuel for energy generation.In the present paper, the solvolysis of a large series of differentranked coals from various deposits of Russia and Mongolia in anthracene oil as a solvent to produce soluble aromatic substances was studied.All the coal samples were well characterized by the data on the chemical composition and on the conventional classification industrial indexes.The correlations between the composition and properties of coals and their reactivity for pyrolysis and for solvolysis with anthracene oil into soluble products were analyzed.Well defined correlations were established between the coal conversion into quinoline solubles and the properties of coals such as vitrinite reflectance, the yield of volatile matter, carbon content, and temperature at which the main decomposition occurs during coal pyrolysis.The criteria for the properties of coals suitable for solvolytic conversion into soluble aromatic substances are suggested.The chemical and group composition and the characteristics of the molecular structure of the soluble products obtained were studied using chemical and 1 H and 13 C NMR techniques.The extract obtained can serve as an alternative source for aromatics, liquid fuels, and for the production of a substitute for coal-tar pitch binder and for other purposes.