Organic sulphur in the hard coal of the stratigraphic layers of the Upper Silesian coal basin

The paper presents the results of investigation of organic sulphur occurrence in the coal of Upper Silesian coal basin. Six hundred coal samples from 52 mines were tested. It has been found that the content of organic sulphur in the coal depends on the stratigraphic layer, coalification grade and geographic location in the Upper Silesia region. The highest mean content of organic sulphur has been found in the most recent (ca. 0.85%) and in the oldest (ca. 0.5%) strata. The lowest mean contents of organic sulphur have been found in the intermediate strata. In the case of the most recent coals, the content of organic sulphur decreases with increasing of coalification grade. When the carbon content (C^daf) exceeds 82%, the increase of coalification grade causes no further decrease of the mean content of organic sulphur. The share of organic sulphur in the total sulphur is lower in the case of more recent (<50%) and higher in the case of older coals (>50%).     

煤化度对煤层气成藏特性影响规律的研究

综述了煤层气的成因类型和成气过程的研究现状,说明生物成因和热成因是煤层气的2种主要成因类型,且煤层气生成过程以热成因为主,生物成因为辅。通过分析不同煤化度煤层气的生成过程,说明在整个煤化作用过程中煤层气的生成大致经历了4个阶段,即由植物遗体转化为泥炭阶段、褐煤转型阶段、长焰煤～瘦煤转化阶段以及贫煤～无烟煤阶段。从煤化度角度阐述了不同煤化度煤层气的贮藏特性,即不同煤化度煤层气存在较大差异,特别是不同煤层气吸附、解吸特征的差异影响了其吸附成藏、解吸、渗流及产出的整个过程;煤吸附CH4的能力随着煤化度的增加呈现先急剧增加后缓慢减小的趋势。最后分析了不同煤化度煤层气存在成藏差异的原因,说明煤化学结构、煤物理结构以及成煤过程中地质条件的差异是导致不同煤化度煤层气富集成藏差异性的主要原因。     

Coalification model

A series of low-rank materials, ranging from biomass waste to subbituminous coal, were subjected to hydrothermal coalification, i.e. heat treatment in an autoclave with water. The results, together with relevant literature data, cover a wide range of reaction conditions: temperatures from 120° to 390° and residence periods from 1 min to 6 months. Using overall kinetics, the progress of hydrothermal coalification in terms of the evolution of carbon dioxide as a function of the conditions has been expressed in a simple model. Low-rank materials can be described in terms of properties that can be gathered into general relations which hold over wide ranges. Over the range from biomass to subbituminous coal, where coalification mainly implies the evolution of water and carbon dioxide, the conversion model allows the prediction of the enrichment of a material on the basis of feedstock properties and the conditions applied.     

Nitrogen-enriched bituminous coal-based active carbons as materials for supercapacitors

The paper presents the results of a study on obtaining N-enriched active carbons from bituminous coal and on testing its use as an electrode material in supercapacitors. The coal was carbonised, activated with KOH and ammoxidised by a mixture of ammonia and air at the ratio 1:3 at 300 °C or 350 °C, at different stages of the production, that is, at those of precursor, carbonisate, and active carbon. The products were microporous N-enriched active carbon samples of well-developed surface area reaching from 1577 to 2510 m²/g and containing 1.0 to 8.5 wt% of nitrogen. The XPS measurements have shown that in the active carbons enriched in nitrogen at the stage of precursor and at the stage of carbonisate, the dominant nitrogen species are the N-5 groups, while in the samples ammoxidised at the last stage of the treatment the dominant nitrogen species are the surface groups of imines and/or nitriles, probably accompanied by amines and amides. The paper reports the results of a comprehensive study of the effect of the structure and chemical composition of a series of active carbon samples of different properties on their capacity performance in water solutions of H₂SO₄ or KOH, with the behaviour of positive and negative electrodes analysed separately.     

Trapped organic compounds and aromatic units in coals

Some insight into the chemical nature of coals and the coalification process was obtained by detailed analyses of the organic constituents of three coals — a lignite, a bituminous, and an anthracite coal. Organic compounds trapped in the coal matrix, residuals and products of the original coalification process, were isolated by vacuum distillation and solvent extraction. The macromolecular material which constitutes the bulk of coals was degraded by a series of selective oxidations to smaller units which could be identified and measured. The essential aromatic character of coals was demonstrated, with condensation of aromatic rings increasing with increasing rank.     

A newly proposed view on coal molecular structure integrating two concepts: Two phase and uniphase models

Concept of coal molecular structure was reexamined on the basis of detailed information concerning aliphatic moieties of coal and the reactions occurred during coalification process. Based on the observed similarity of the distribution of chain length between alkylene bridge bonds and alkyl pendant groups on coal aromatic cluster, the authors have already proposed [Nomura, M., Murata, S., Kidena, K. 2004a. Some view on the solubilities of coals toward solvents. Proceedings of 21st Annual International Pittsburgh Coal Conference, No. 12-4.] the presence of common intermediates in the coalification process which results in uniphase structure under reductive conditions and two phase structure under oxidative conditions, respectively. The present paper proposes, the concept that the reactivity of the coal aromatic moieties for common intermediates and/or the stability of common intermediates govern the reactions leading to a two phase structure or uniphase structure in more rationalized way as coalification is believed to proceed under reductive conditions, especially at its late stage. Brown and subbituminous coals have relatively many oxygen-containing functionalities on aromatic moieties so that their aromatic rings are activated for radical reactions. Common intermediate radicals, aryl alkyl radicals, from cleavage of alkyl pendant groups on aromatic rings and alkylene bridge bonds attack neighboring aromatics to form entanglement-like structure in an easy way. These structures are less soluble to organic solvents due to its entanglement character. Bituminous coals with high solubility toward CS₂/NMP solvents tend to have carbon contents from 85 to 87% (daf. basis), their aromatic moieties being so stable that intermediate radicals cited above can attack more selectively the neighboring aromatic moieties: they have less tendency to make such bridge bonds to form cross linked structures, the resulting coal molecules being not entangled like uniphase. In the case of coals having more carbon than 87% or bituminous coals with less carbon than 85%, the resulting coal molecules become less soluble toward organic solvents: In the higher rank coals, the aromatic rings are so large and so stable that their solubility toward solvent are intrinsically low. In addition to this, it is supposed that bridge bonds are cleaved to make the structure with less cross linking. Their stacking tendency should be also considered as other reason for low solubility to solvent. On the other hand, less solubility of the lower ranked bituminous coals can be rationalized partly, in an analogy with the behavior that the brown and subbituminous coals show, despite of their relatively large aromatic clusters.     

Comparative behaviour of coal and maceral concentrates during artificial coalification

A series of experiments were performed in cold-seal autoclaves (confined-pyrolysis) to characterize the behaviour of individual macerais (vitrinite, inertinite, exinite) extracted from the same Lorraine Basin coal during artificial coalification. Rock-Eval pyrolysis, elemental analysis and weight loss determination provided the simple maturation indexes required. Emphasis was laid on the timing of hydrocarbon generation and on the possible similarities existing between inertinite and vitrinite of higher rank. Hydrocarbon potential and hydrocarbon yield were found to increase from inertinite to vitrinite and exinite, but similar mechanisms were involved during the thermal degradation of both inertinite and vitrinite.     

Characterization and classification of Rocky Mountain coals by Curie-point pyrolysis mass spectrometry

A set of 102 coal samples from the Rocky Mountain coal province, selected from the Penn State Coal Sample Bank, was analysed by Curie-point pyrolysis mass spectrometry in combination with computerized pattern recognition techniques. The spectra obtained were shown to be quite representative for the coal seams with characteristic differences often present between different seams, fields or regions within the Rocky Mountain Coal province. In general, the spectra were found to be dominated by homologous ion series, e.g., representing dihydroxybenzenes, phenols, naphthalenes, benzenes, alkenes, dienes, alkyl fragments and sulphur compounds with varying degrees of alkyl substitution. The relative abundances of dihydroxybenzenes and naphthalenes were shown to correlate closely with differences in rank, whereas those of phenols, aliphatic hydrocarbons and sulphur compounds appeared to correlate more closely with differences in depositional environment. Different spectra -dominated by aliphatic compound series -were obtained from several samples of a boghead coal (Cannel King seam). Moreover, spectra of two of these boghead coal samples, known to be severely weathered, showed markedly increased CO₂⁺ and C₆H₆⁺ signals, indicating the presence of benzenecarboxylic acids. Factor analysis of pyrolysis m.s. data revealed the two main underlying chemical tendencies to be a shift from heteroatomic compounds to hydrocarbon series with increasing rank and a difference in degree of aromaticity corresponding primarily to differences in depositional environment. The dominant rank-related factor exhibited a clear coalification break between the ASTM hvC bituminous and hvB bituminous ranks and appears to represent a significant shift in coalification mechanisms. It was demonstrated that rank-dependent differences in the pyrolysis mass spectra enable correct classification of the spectra into four ASTM rank classes (subbituminous, hvC, hvB and hvA bituminous) in 90% of all cases. Moreover, the discovery of a marked aliphaticity/aromaticity factor in the data could be useful for the direct measurement of aromaticity (f_a) from pyrolysis mass spectra of whole coals.     

Structural parameters of Donetsk and Lvov-Volynsk coal

The parameters ??, B, f _a , and cA calculated from the elementary composition of Donetsk and Lvov-Volynsk coal of different metamorphic stages characterize not so much the structure of the organic mass as the relative rates of chemical reactions determining the carbon, hydrogen, and oxygen content in two successive coalification periods: specifically, the rate of decarboxylation in the first period; and the rates of dehydrogenation and dehydration in the second.     

Dependence of carbon dioxide sorption on the petrographic composition of bituminous coals from the Czech part of the Upper Silesian Basin, Czech Republic

The effect of the rank and of the maceral composition of bituminous coal on carbon dioxide sorption capacity was studied on the basis of samples from two coal mines (Darkov, ?SM) from the Czech part of the Upper Silesian Basin. The samples from the two mines cover a small but very significant section of coalification within the transition zone between high-volatile bituminous A coal and medium-volatile bituminous coal, where porosity and sorption properties pass through their minima. The coal porous system was characterized by the micropore volume evaluated using the sorption isotherm of carbon dioxide and the volumes of meso-, macro- and coarse pores were determined by high-pressure mercury porosimetry. The micropore fraction in the coal porous system ranged between 53% and 75%. It was particularly high in coals with high vitrinite content, namely collotelinite, and also in coals with high inertinite content. The carbon dioxide sorption capacity was determined from the carbon dioxide sorption isotherms measured using a gravimetric sorption analyzer at 298 K until a relative pressure of 0.015 p/p_s, and was interpreted by characteristic parameters of the Dubinin and Langmuir equations. It was found that the adsorbed amount of CO₂ in the ?SM coal increases with the content of vitrinite and collotelinite, whereas no increase or only a slight increase was observed for the Darkov coal. The tendency of adsorption capacity to depend on maceral composition, and also to some extent on coalification, observed for the ?SM coal, may be related to higher microporosity due to the coalification process or oxidative processes leading to the formation of pseudovitrinite.     

Influence of cultural conditions on coal solubilization by Penicillium simplicissimum

Sub-bituminous coal, preoxidized with nitric acid and treated with sodium hydroxide solutions to obtain a water-soluble extract, was used for the study of coal degradation by Penicillium simplicissimum. The influence of different carbon and nitrogen sources was examined in connection with growth and production of acid-precipitable coal polymers. The yield was increased after the addition of maltose, lactose and cellobiose while glucose, fructose and xylose had little effect. An organic nitrogen source, yeast extract, was an improved source of nitrogen compared with ammonium chloride. The coal-degrading system appeared before the depletion of the carbon or nitrogen source. In addition, the effects of initial pH of the culture medium demonstrated an increase in the yield of coal polymers up to a pH of 7.5. Above this pH, non-biological catalysis increased gradually. However Ca²⁺ and Mn²⁺ increased the yield of coal polymers over a 14-day period, but yield was unaffected by Cu²⁺, Al³⁺ and Fe²⁺.     

XPS study and physico-chemical properties of nitrogen-enriched microporous activated carbon from high volatile bituminous coal

N-enriched microporous active carbons of different physico-chemical parameters have been obtained from high volatile bituminous coal subjected to the processes of ammoxidation, carbonisation and activation in different sequences. Ammoxidation was performed by a mixture of ammonia and air at the ratio 1:3 (flow ratio 250 ml/min:750 ml/min) at 350 °C, at each stage of production i.e. that of precursor, carbonisate and active carbon. Ammoxidation performed at the stage of demineralised coal or carbonisate has been shown to lead to a significant nitrogen enrichment and to have beneficial effect on the porous structure of the carbon during activation, allowing obtaining samples of the surface area of 2600-2800 m²/g and pore volume 1.29-1.60 cm³/g to be obtained with the yield of about 50%. The amount of nitrogen introduced into the carbon structure was found to depend on the sequence of the processes applied. The greatest amount of nitrogen was introduced for the processes in the sequence carbonisation → activation → ammoxidation. The introduction of nitrogen at the stage of active carbon leads to a reduction in the surface area and lowering of its sorption capacity. From the XPS study, ammoxidation introduces nitrogen mainly in the form of imines, amines, amides, N-5 and N-6, irrespective of the processing stage at which it is applied.     

Structural evolution of a sedimentologically homogeneous coal series as a function of carbon content by solid state 13C n.m.r.

The cross polarization technique combined with magic-angle spinning has been applied to obtain ¹³C n.m.r. spectra of a sedimentologically homogeneous series of peat, lignite and bituminous coal derived from higher plants. Despite some uncertainties on the quantitative aspects of the method, the structural information obtained was corelated with data from elemental analysis. Structural average parameters were also calculated by using the structural basic unit concept and relating it to the maturation stage of the organic matter.     

煤结构演化煤化度指标

通过对不同煤化程度煤样的镜质组反射率测定和X衍射等实验,引入煤化度p的概念,对煤的化学成分及微晶结构进行分析,发现煤化度p随煤化程度的升高呈阶段性演化特征,并能规律地反映煤演化过程中成分结构的变化,表明煤化度是表征烟煤阶段煤化程度的可靠指标;在中低煤化程度阶段,煤岩组分是影响煤化度的主要因素:丝炭具有一定的微晶结构,镜煤微晶化程度较低,而树脂煤结构不能用煤化度来描述.     

Char morphology and behaviour of Australian vitrinites of various ranks pyrolysed at various heating rates

This study concerns the relative importance of rank and heating rate on the development of plasticity during pyrolysis of several Australian vitrinites. Dispersed vitrinite particles, 100 μm in diameter, were heated to 1000 °C in nitrogen at linear heating rates ranging from 10^?1 to 10⁴ °Cs^?1 in a special electrical strip furnace. When pyrolysed at 10⁴ °C s^?1 all vitrinites became plastic and vesiculated except for vitrinite from anthracite, and gelinite from brown coal. The greatest plasticity developed in bituminous-rank vitrinite. Brown coal textinite and the lower-rank sample of the two subbituminous-rank vitrinites behaved similarly, whereas the behaviour of the higher-rank subbituminous coal resembled that of the semi-anthracite sample. At heating rates of 10^?1 °C s^?1 all the vitrinites retained their original morphologies. Cenospheres began to form in the vitrinites within the heating rate range of 1 °C s^?1 (for bituminous rank) to 10² °C s^?1 (for brown coal and semi-anthracite ranks). During pyrolysis, the differences in plastic behaviour attributable to rank could largely be eliminated by changing the heating rate by two orders of magnitude. The effects attributable to plasticity related to increasing heating rates reach a limit within five orders of magnitude of heating rate (for the conditions used in this study).     

Origin of methane in coal beds in the initial and intermediate stages of coalification

In the initial stages of coalification, there is no dehydrogenation, and therefore the organic mass of coal cannot be the source of hydrogen for methane formation. It is possible that an explosive mixture of methane and oxygen may be formed from carbon dioxide and moisture in the coal bed as a result of bacterial activity.     

Micrinite and exudatinite in some Australian coals,and their relation to the generation of petroleum

The occurrence and microscopic features of micrinite and exudatinite in some Australian coals are reported. The origin of these macerals and also the significance of their occurrence are discussed in connection with hydrocarbon genesis. In Australia, micrinite occurs in bituminous and sub-bituminous coals which are very rich in inertinite, and also in brown coal rich in inertinite. One of the possible progenitors of micrinite is oxidized porigelinite. There is little reason to conclude that micrinite was formed from resinite and other macerals at an early stage of coalification and that liquid hydrocarbons were formed during this process. Exudatinite occurs in sub-bituminous and high-volatile bituminous coals in the Gippsland Basin. There is no positive evidence of a genetic relation between liquid hydrocarbons, exudatinite, micrinite and liptinite macerals. The formation of liquid hydrocarbons from solid liptinite etc. may take place just before and during Teichmüller's so-called ‘2nd coalification jump’.     

Voltammetry and electrolysis of coal slurries and H-coal liquids

The voltammetric and electrolytic behaviour of several coal slurries and H-coal liquids was examined in both aqueous and organic solvents. Most aqueous coal samples yielded anodic currents starting a approximately + 0.4 V versus SCE while current was observed only at more positive potentials in dimethylsulphoxide and acetonitrile. The electroactive species always appeared to consist largely of material extracted from the coal matrix. The extract from the aqueous coal slurries contained significant amounts of iron, and the oxidation of Fe²⁺ to Fe³⁺ was found to be largely responsible for the anodic currents at + 0.4 V. Constant potential electrolysis of the aqueous coal slurries indicated that the onset of coal oxidation occurred at an applied potential difference of approximately 1.0 V and again appeared to be related directly to the oxidation of Fe²⁺ leached from the coals.     

Fourier transform infra-red studies of coal

The application of Fourier transform infra-red (FT-i.r.) spectroscopy to the elucidation of coal structure is discussed. Hydroxyl determination by a combination of acetylation and FT-i.r. for a rank range of British coal indicates that, during coalification through the bituminous range, the proportion of oxygen as hydroxyl groups increased and deoxygenation is primarily associated with the loss of carbonyl and ether groups. However, during coalification of bituminous coal to anthracite loss of oxygen is primarily associated with dehydroxylation. The use of FT-i.r. to study changes in the oxidation of a single bituminous coal, Horden, shows that the loss of aliphatic CH groups is a prominent feature at low temperatures of oxidation. Cross-linked structures only develop at higher oxidation temperatures, at which carboxylic acids are also a major product.     

Heats (enthalpies) of formation of coals and the thermodynamic evaluation of the coal formation process

An approach to the calculation of the quantity of heat consumed in the process of coal formation is presented. The variability of this parameter in a coalification series is analyzed using coals from the Kuznetsk and Tunguska Basins as an example.