Chemical Structure Of Coal Research Articles

Structure and coalbed methane occurrence in tectonically deformed coals

Research on structure of tectonically deformed coals (TDC) is a key issue in coal and gas outburst prevention and coalbed methane (CBM) exploitation. This paper presents a summary on the research progress in TDC’s structural-genetic classification, tectonic strain influence on coal microstructure, coal porosity system, coal chemical structure and constituents, and their relationship with the excess coalbed methane. Previous studies suggested that tectonic deformation had significant influence on coal microstructure, coal super microstructure, and even chemical macromolecular structure. The main mechanisms of coal deformation are the tectonic stress degradation and polycondensation metamorphism (dynamical metamorphism). Besides, under different deformation mechanisms, the ultra- and micro-structure and chemical constituents of TDC presented distinct characteristics. Based on these achievements, we propose one possible evolutionary trend of TDC with different deformation mechanisms, and suggest that the coal and gas outburst in the TDC, especially in the mylonitic coals, may be not only controlled by geological structure, but also influenced by the tectonic stress degradation of ductile deformation. Therefore, further study on TDC should be focused on the controlling mechanism of deformation on structure and composition of coal, generation conditions and occurrence state of excess coalbed methane from deformation mechanism of coal.

Composition and Structure of Coal Organic Mass. 3. Dinamics of Coal Chemical Structure During Metamorphism

Dynamics of coal chemical structure during metamorphism has been evaluated using mathematical model of metamorphism kinetics attached to the time axis in accordance with artificial coalification data.

Study on Coal Spontaneous Combustion Characteristic Structures Affected by Ionic Liquids

According to modern coal chemical structure theory, the active chemical structure categories in coal spontaneous combustion process were summed up, which show that the coal spontaneous combustion characteristic structures are dynamic, such as methyl, methylene, hydroxyl, carbonyl and others in coal bridge bonds and side chains. The amount and activity of these structures play an important role in coal low temperature oxidation stage. Based on this, the article analyzed the effect of ionic liquids to coal spontaneous combustion characteristic structures, which indicates that the structure amount of coal affected by ionic liquids decreases obviously compared with raw coal.

Isotope Analysis for Understanding the Tar Formation in the Integrated Process of Coal Pyrolysis with CO2 Reforming of Methane

In our previous studies, a higher tar yield can be obtained from a novel integrated process of coal pyrolysis with CO2 reforming of methane (CRMP) than the traditional coal pyrolysis process. However, the tar formation mechanism in the CRMP process was not yet clear. In this work, deuterated methane (CD4) was used to investigate the formation mechanism of coal tar in the integrated process through analyzing the chemical compounds of coal tar with gas chromatography and mass spectrometry (GC/MS) analysis. The results showed that deuterium was detected in the main compounds of tar with the existing form of [•D] and [•CD3]. Deuterium in CD4 took part in the formation of coal tar compounds, indicating that the atmosphere took an important role in the formation of coal tar. When the formation process of certain compounds was analyzed, it can be deduced that the higher coal tar yield in the CRMP process can be attributed to the interaction of free radicals formed from the CO2 reforming of methane and from the cracking of the coal chemical structure in pyrolysis.

Solid-state C-13 CP/MAS NMR study of Baganuur coal, Mongolia: Oxygen-loss during coalification from lignite to subbituminous rank

Abstract The rank of Lower Cretaceous Baganuur coal from Mongolia ranges from lignite to subbituminous coal, indicating transition from biochemical to physico-chemical coalification stages. The changes in the chemical structure of coal were studied using solid-state C-13 CP/MAS NMR. The predominant change during the transition between the two coalification stages was the dramatic decrease in dihydric and/or methoxy phenols. Concurrently, protonated aromatic carbon positioned next to O-substituted carbon decreased drastically, while C-substituted aromatic carbon increased. These changes indicate that O-containing functional group was continuously replaced by C-substituent. In addition, the amount of carbonyl and oxygenated aliphatic carbons decreased. All these transformations were greatly intensified at the beginning of the physico-chemical stage. The results, based on the chemical structure of inertinite-rich coal, suggest that during the fusinitization path, small amounts of hydrogen and oxygen remained as H- and OH-substituents of condensed aromatic rings, while other functional groups were completely destroyed. During the coalification from lignite to subbituminous rank, oxygen is significantly changed compared with carbon and hydrogen due to the elimination of oxygen-containing functional groups especially from dihydric phenol, methoxyl, and carbonyl carbon.

ＥＳＲによる急速加熱炭の石炭構造解析

Coal was heat-treated up to the softening temperature under the 2 types of heating conditions (10°C/min, 104°C/min). Spin concentration by high temperature Iusitu ESR, and the saturation behavior of the ESR spectrum were measured. Based on that result, effect of rapid preheating on coal molecular structure was examined.(1) Because the change in coal chemical structure by the cracking reaction is taking place, spin concen-tration of slow preheated coal is higher than that of rapidly preheated coal and raw coal. At 300°C or more, the spin concentration of rapidly preheated coal is same profile as raw coal. In the case of rapid preheating, it is indicated that the degree of coal structure change by cracking reaction is small.(2) The following results were obtained as the saturation power of ESR was measured. At 250°C or more, the saturation power of slow preheated coal declines as the temperature rises. One side, it confirmed that the saturation power of rapidly preheated coal became large at 370°C. The increase in saturation power indicates that the relaxation of coal structure progressed about coal molecular structure part that can be observed with ESR.

Carbonization and demineralization of coals: A study by means of FT-IR spectroscopy

Coal basically consists of two parts—a crystalline, inorganic part, and an amorphous, organic part. Based on this, we intended to study the changes that occurred on the composition and on the chemical structure of coals after carbonization at 1000 or 900° C and demineralization treatments with hydrochloric and hydrofluoric acids. For this, four coals of different categories (or levels) were chosen: semianthracite (A-O) and high volatile bituminous coal (B-O), which are high level coals, and lignite (Li-O) and leonardite (Le-O), these being low level coals. The coals were first analysed in terms of their proximate and elemental compositions and then carbonized and demineralized. Also, the starting coals and the prepared samples were examined by infrared spectroscopy. In addition, a study of the optimization of the application of this technique for only A-O was carried out. For A-O and B-O, the spectra recorded intense absorption bands that are ascribable to vibration modes in mineral components as quartz and aluminosilicates, such as kaolinite. For Li-O and Le-O, the spectra displayed some other bands as well, also quite intense, which have been assigned to bond vibrations in functional groups and structures of their organic part. The carbonization of the coals resulted in significant changes in their inorganic part as the content of quartz increased and the content of aluminosilicates decreased. In addition, the thermal decomposition of mineral carbonates occurred. The carbonization greatly affects the organic part of the coals, especially in Li-O and Le-O, as most functional groups and structures are not thermally stable under heating conditions. With regard to demineralization, HF is a more effective agent than HCl, achieving products with higher organic content. The mass losses are higher in Li-O and Le-O than in A-O and B-O. So, the infrared spectroscopy allows the analysis of both inorganic and organic parts of the coals and of their carbonization and demineralization products. These processes facilitate subsequent analysis of the inorganic and organic parts of coals by infrared spectroscopy. In the application of this technique, both the coal: KBr ratio and the thickness for the disks should be controlled, owing to the influence on the infrared absorption.

Reactivity of Coal Activated by Mechanochemical Treatment

The paper presents new information on the transformation changes in the chemical structure of coal caused by mechanical activation using the GACL procedure. In the case of chemical treatment of Pittsburgh bituminous coal, the CAPTO method has confirmed a temperature Tmax shift for identification of carbonaceous and sulfur compounds (ΔTmax/Sorganic) − 50°C; ΔTmax/Corganic − 50°C). The temperature reduction of the thermal destruction maximum of carbonaceous and sulfur aromatic compounds is a result of activation of the coal structure of bituminous coals. The environmental effect of desulfurization (approx. 70%), detoxication, e.g., removal of arsenic (approx. 95%) and increase in the content of humic acids in the treated coal batch, have been proved by mechanical activation of Novaky brown coal using the GACL procedure. It is possible to improve the technological parameters of chemical treatment by optimization of the GACL procedure.

Basic Studies of Coal to Enhance Its Development as a Clean Fuel

Coal is the most abundant source of energy. However, there is a need to develop cleaner, and more efficient, economical, and convenient coal conversion technologies. It is important to understand the organic chemical structure of coal for achieving real breakthroughs in the development of such coal conversion technologies. A novel computer-assisted modeling technique based on the analysis of 13C NMR and gel permeation chromatography has been applied to predict the average molecular structure of the acetylated product of a depolymerized bituminous Indian coal. The proposed molecular structure may be of practical use in understanding the mechanism of coal conversions during the processes of liquefaction, gasification, combustion, and carbonization.

99/01760 How far does chemical structure of coals become apparent?: Nomura, M. Kagaku to Kogyo (Tokyo), 1998, 51, (10), 1579–1582. (In Japanese)

99/01760 How far does chemical structure of coals become apparent?: Nomura, M. Kagaku to Kogyo (Tokyo), 1998, 51, (10), 1579–1582. (In Japanese)

Characteristics of telemagmatic metamorphism of the Ceshui Formation coal in Lianyuan coal basin

The Ceshui Formation coal is mostly anthracite and its metamorphism has been less documented. By analyzing systematically the reflectance of vitrinite and the results of X-ray diffraction of the Ceshui Formation coal in the Lianyuan coal basin, the spatial variation characteristics of coal ranks, coal metamorphic regions, the extension of coal metamorphic belts, coal metamorphic gradients, coal chemical structure and the effect on the degree of metamorphism of heat-production and storage conditions, buried depth of the Indosinian-Yenshanian granites at the margins of the Lianyuan coal basin are discussed. The research results in conjunction of the features of regional hydrothermal alterations, endogenetic deposits with the Ceshui Formation coal measures, and the development of secondary vesicles indicate that the telemagmatic metamorphism is the main factor leading to the metamorphism of the Ceshui Formation coal in the region studied.

98/01058 Coal liquefaction characteristics and chemical structure of product oil: Endob, H. et al. Sekitan Kagaku Kaigi Happyo Ronbunshu, 1996, 33, 57–60. (in Japanese)

98/01058 Coal liquefaction characteristics and chemical structure of product oil: Endob, H. et al. Sekitan Kagaku Kaigi Happyo Ronbunshu, 1996, 33, 57–60. (in Japanese)

98/00207 Coal liquefaction characteristics and chemical structure of product oil

98/00207 Coal liquefaction characteristics and chemical structure of product oil

98/00018 Investigation of asphaltenes from bituminous coals to evaluate coal chemical structure

98/00018 Investigation of asphaltenes from bituminous coals to evaluate coal chemical structure

97/01510 Effect of calcium and calcium minerals in coal on its thermal analysis

In order to study the relationships between the chemical structures of coals, coal macerals and their precursors (plant tissues), eight coal macerals originating from the Yorkshire coal basin (U.K.) were studied by Curie point pyrolysis-gas chromatography and Curie point pyrolysis-gas chromatography-mass spectrometry. The samples were selected on the basis of a previous study of a large set of macerals. The macerals were studied in order to relate structural moieties of the macerals, as reflected by their pyrolysis products, to structural elements of their likely precursors, plant tissues.The maceral pyrolysates mainly consist of alkylbenzenes, alkylnaphthalenes, alkylphenols and series of straight-chain alk-l-enes and alkanes over a wide molecular weight range.The relative contribution of the (hydroxy)aromatic pyrolysis products and of the straight-chain alk-l-enes and alkanes to each maceral pyrolysate was calculated, although the internal distribution patterns of the alkyl derivatives of these pyrolysis products exhibited to a certain extent dissimilarities. Differences between the relative contributions of these pyrolysis products to the pyrolysates of different macerals with the same coal rank and to those of similar macerals with different coal rank depend on differences in precursor material and the chemical modification of these precursors upon increasing coalification.Multivariate data treatment by means of factor analysis was chosen to compare the pyrolysis data—represented by these histograms—with the petrographic data and the proximate and ultimate analysis values of the macerals. In addition, similar analyses was performed on the macerals using such a low Curie temperature (358°C), that from some of the macerals “thermal extracts” were obtained, containing a series of n-alkanes and some isoprenoids such as pristane and phytane. Although these thermal extracts represent only a low percentage by weight of the maceral samples, their existence probably will affect both the chemical and physical properties of the macerals, although they are in fact no pan of the coal structure itself.

固体ＮＭＲを用いた石炭構造研究に関する最近の動向

The present review is mainly concerned with the study on the coal structure using solid state NMR, especially for the relationship between relaxation times and coal dynamic structures.The reports on the measurement of T1H (spin-lattice relaxation time) and T2H (spin-spin relaxation time) of coal were mainly reviewed. These two parameters directly relate to the molecular mobility. Thus the measurement of these relaxation times could make an investigation for coal molecular mobility.The influence of water existing in coals and the swelling of coals derived by organic solvents to the relaxation time and the changes of the coal molecular mobility by heating were also studied.More information on the chemical structure of coal and the structural changes of coal during various reactions could be obtained in the basis of molecular mobility using solid state NMR.

96/00001 Application of computer chemistry to the study of coal chemical structure

96/00001 Application of computer chemistry to the study of coal chemical structure

95/03245 The chemical structure of coal in regard of microbiological degradation

95/03245 The chemical structure of coal in regard of microbiological degradation

95/01174 Studies on chemical structure of coal. II. Comparison of carbon distribution based on pyrolysis data with those from solid-state NMR data

95/01174 Studies on chemical structure of coal. II. Comparison of carbon distribution based on pyrolysis data with those from solid-state NMR data

95/02163 Scanning transmission X-ray microscopy: A new ‘looking glass’ into coal chemical structure

This paper reports the use of scanning transmission x-ray microscopy to spatially map the chemistry of aromatic and aliphatic carbon functionalities in coal to a resolution of less than 0.1 {mu}m. Localized x-ray absorption spectroscopy recorded at the carbon K absorption edge was also used to facilitate analysis of variations in fundamental chemistry at maceral interfaces and within maceral boundaries.