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Differences in the pore and fracture systems of four marcolithotypes (bright，semi‐bright, semi‐dull and dull) in coal reservoirs affect the quality of coalbed methane (CBM) and constrain exploration and development of CBM. In this paper, vitrinite reflectance (RO), maceral composition, proximate analysis, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), low‐field nuclear magnetic resonance (NMR) and high‐pressure isothermal adsorption experiments and the mathematical method of fractal dimension were carried out on high‐rank coal samples of different marcolithotypes from the Weizhou mining area in the western margin of Ordos Basin. The results show that from bright coal to dull coal, the RO and vitrinite content gradually decrease, while the mineral content and Aad gradually increase. SEM images show that the bright and semi‐bright coals develop open fractures, whereas semi‐dull and dull coals develop closed fractures. According to pore size distribution established by MIP and NMR, the proportion of seepage pores gradually increased from bright coal to dull coal, and MIP fractal dimension of seepage pores (DM2; 2.3352, 2.3532, 2.3755 and 2.4727, respectively) and NMR fractal dimension of seepage pores (DN2; 2.8767, 2.9142, 2.9297 and 2.9981, respectively) show that the structure of the seepage pore is progressively more complex from bright coal to dull coal. In addition, percentage of NMR adsorption pores progressively increases from bright coal to dull coal (64.96%, 76.64%, 82.04% and 89.67%, respectively), but total porosity of bright coal (6.74%) is much greater than that of dull coal (1.34%), which results in that bright coal also has the strongest CH4 adsorption capability (Langmuir volume is 22.898 cm3/g). [ABSTRACT FROM AUTHOR]

Efficient enrichment of macerals improves the liquefaction efficiency of low-rank coal. The paper studied the characteristics of Shendong low-rank coal, including proximate and ultimate analyses, size and density compositions, and petrographic analysis, as well as the migration regularity of narrow particle size of low-rank coal macerals in the enhanced gravity field. On this basis, a novel classification separation process for low-rank coal macerals using Krebs hydrocyclone and enhanced gravity separator was proposed. The classification size was determined to be 0.074 mm and Krebs hydrocyclone achieved a satisfactory classification effect with a classification efficiency of 84.72%. Based on the enhanced gravity separation results of macerals from hydrocyclone underflow and overflow, the optimal sorting solutions for underflow and overflow were obtained through response surface analysis, respectively. Through the novel classification separation process, the vitrinite content of clean coal has been increased from 46.60% to 61.33% with an outstanding recovery of 77.40%. The novel classification separation process using hydrocyclone and enhanced gravity separator develops an excellent enrichment effect for low-rank coal macerals, which also provides a prospective approach for the cleaner utilization of low-rank coal. [ABSTRACT FROM AUTHOR]

The Carboniferous-Permian coal measure strata in the Qinshui Basin exhibit highly lithium (Li) enrichment, with substantial exploitation potential. To further explore the enrichment mechanism of lithium in coal measure strata, the No. 15 coal of the Taiyuan Formation from the Gaoping mine is taken as the research object, and its mineralogical and geochemistry characteristics are evaluated using optical microscopy, X-ray diffraction, scanning electron microscopy, inductively coupled plasma mass spectrometry, X-ray fluorescence, and infrared spectral. The results show that the No. 15 coal is semi-anthracite coal with low moisture, low ash, low volatility, and high sulfur. Organic macerals are primarily vitrinite, followed by inertinite, and liptinite is rare; the inorganic macerals (ash) are dominated by clay minerals (predominantly kaolinite, cookeite, illite, and NH4-illite), calcite, pyrite, quartz, siderite, gypsum, and zircon. The average Li content in the coal is 66.59 μg/g, with higher content in the coal parting (566.00 μg/g) and floor (396.00 μg/g). Lithium in coal occurs primarily in kaolinite, illite, cookeite, and is closely related to titanium-bearing minerals. In addition, Li in organic maceral may occur in liptinite. The No. 15 coal was formed in the coastal depositional system, and the deposition palaeoenvironment is primarily a wet–shallow water covered environment in open swamp facies; the plant tissue preservation index is poor, and aquatic or herbaceous plants dominate the plant type. The reducing environment with more terrestrial detritus, an arid climate, and strong hydrodynamic effects is favorable for Li enrichment in coal. The results have important theoretical significance for exploring the enrichment and metallogenic mechanisms of Li in coal. [ABSTRACT FROM AUTHOR]

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The application of the hydrodynamic method has enhanced the extraction of coal bed methane (CBM). In this method, fracturing fluid rapidly penetrates the coal reservoir, altering its intrinsic pore structure and microscopic mechanical properties. These changes impact the properties of the coal reservoir and CBM depletion. It is, therefore, crucial to explore how these micro-characteristics evolve following water invasion. In this context, using nanoindentation tests, the microscopic characteristics of three coal samples were measured under dry conditions and at water saturations corresponding to 44% and 75% relative humidity. The influence of water immersion on the pore structure was also assessed using mercury injection experiments. Moreover, cluster analysis was used to categorize the extensive measured data into three sub-components: fractures (large pores), inertinite, and vitrinite, to investigate the impact of water saturation on microscopic properties. The findings indicate that cluster analysis is well-suited to these data, showing excellent agreement with porosity and maceral tests. The relationship between the elastic modulus and hardness of dry and wet coal samples varies across the sub-components. There is a notable dependency in the case of vitrinite, whereas water content tends to reduce this dependency. It is also found that water content negatively affects elastic modulus and hardness and reduces the anisotropy ratio. The mechanical properties of inertinite are highly responsive to water immersion, whereas vitrinite exhibits lesser sensitivity. The softening mechanisms of coal when immersed in water, such as calcite phase dissolution, swelling stress fracturing, and weakening of macerals, are identified. This study offers new perspectives on the impact of moisture on the alteration of micromechanical properties in coal. [ABSTRACT FROM AUTHOR]

Cambrian shales in China and elsewhere contain abundant oil and gas resources. However, due to its deep burial and limited outcrop, there has been relatively little research conducted on it. The Cambrian shale of the Tadong low uplift in the Tarim Basin of western China, specifically the Xidashan–Xishanbulake Formation (Fm.) and overlying Moheershan Fm. provide a case study through the use of organic petrology, mineralogy, organic and elemental geochemistry, with the aim of analyzing and exploring the hydrocarbon generation potential (PG) and organic matter (OM) enrichment mechanisms within these shale formations. The results indicate that: (1) the Cambrian shale of the Tadong low uplift exhibits relatively dispersed OM that consists of vitrinite‐like macerals and solid bitumen. These formations have a higher content of quartz and are primarily composed of silica‐based lithology; (2) shale samples from the Xidashan–Xishanbulake and Moheershan formations demonstrate high total organic carbon (TOC) and low S2 content. The OM is predominantly type I and type II kerogens, indicating a high level of maturation in the wet gas period. These shales have undergone extensive hydrocarbon generation, showing characteristics of relatively poor PG; (3) the sedimentary environments of the Xidashan–Xishanbulake and Moheershan formations in the Tadong low uplift are similar. They were deposited in warm and humid climatic conditions, in oxygen‐deficient environments, with stable terrigenous inputs, high paleoproductivity, high paleosalinity, weak water‐holding capacity, and no significant hydrothermal activity; and (4) the relationship between TOC and the paleoproductivity parameter (P/Ti) is most significant in the Lower Cambrian Xidashan–Xishanbulake Fm., whereas correlation with other indicators is not evident. This suggests a productivity‐driven OM enrichment model, where input of land‐derived material was relatively small during the Middle Cambrian, and the ancient water exhibited lower salinity. A comprehensive pattern was formed under the combined control of paleoproductivity and preservation conditions. This study provides valuable guidance for oil and gas exploration in the Tarim Basin. [ABSTRACT FROM AUTHOR]

The hydrocarbon generation potential of the Campano-Maastrichtian to Paleogene shales from the Benin Flank (located in SW Nigeria) of the Anambra Basin, has been previously investigated mostly by studying outcrops and by relatively few subsurface data-based studies. Thus, it is expedient undertaking an assessment of the hydrocarbon generation potential of this frontier area from subsurface samples. Campano-Maastrichtian to Paleogene shale samples obtained from Egoli-1 borehole in the Benin Flank of the Anambra Basin are studied by means of HAWK programmed pyrolysis, organic petrography, and mineralogy (XRD), with the aim to explore the petroleum-generating potential and the thermal maturity. The obtained results display a significant variation of the TOC content ranging from very low (<0.5%) to significant (>5%), indicating poor to excellent oil potential based on S2 values under the condition, of course, the studied formations reached the oil window. The shales of the Nsukka and Imo Formations display lower petroleum-generating potential than these of the Mamu Formation. All the studied samples are dominated by gas-prone (type III) and inert (type IV) kerogens, with few displaying mixed II/III (oil- and gas-prone). The organic-petrography observations support partly the results of the HAWK programmed pyrolysis, as they reveal an organic-richer Mamu Formation in comparison to the Nsukka and Imo Formations; huminite/vitrinite particles (both indigenous and recycled) along with variable contents of liptinite (mostly alginite and bituminite) and inertinite macerals (mostly inertodetrinite) are hosted in the shales. The latter display a typical composition for fine-grained clastic sediments; mostly kaolinite, illite/montmorillonite, quartz, and subordinately, anatase. In terms of thermal maturity, huminite/vitrinite reflectance data points to immature stage; however, the occurrence of solid bitumens, displaying equivalent vitrinite reflectance values within the oil window, points to an active petroleum system in sequences deeper than the examined ones. [ABSTRACT FROM AUTHOR]

Geochemical analysis was performed on the Cretaceous sequence of the Azhar‐A‐2 well in the West Beni Suef Basin (WBSB), Western Desert, Egypt, utilizing data on total organic carbon (TOC), kerogen composition, vitrinite reflectance (Ro%) and Rock‐Eval pyrolysis. In addition, a 1D basin model was built to investigate the burial and temperature history of the study area. The most important Cretaceous source rocks are predominantly reported within the Albian Kharita Formation and Late Cenomanian‐Santonian Abu Roash (AR) Formation. Based on visual kerogen tests and Rock‐Eval pyrolysis, AR Formation (A, E, F, and G) are mixed oil‐ and gas‐prone source rocks with kerogens ranging from type II to type III, where A/R 'A and F' Members show dominant oil‐prone kerogen with the highest generative potential, while A/R 'E and G' Members are more gas‐prone kerogen. Most samples of the lower Kh Formation were interpreted as gas‐prone kerogen type III with low generative potential. On the other hand, the high amount of liptinite in the visual kerogen macerals is a strong indicator that the lower Petroleum Formation is an oil‐prone rather than gas‐prone source rock. The thermal maturity of the studied members increases consistently with depth, ranging from immature at the top of the AR Formation to the main/peak oil window at the base of the Lower Kharita Formation, which served as an active source rock for the hydrocarbons generated in the WBSB. The high value of the heat flow in the Beni Suef Basin (57 and 60 mW/m2) is a good indicator for the shallowing of the active source rock depth limit depth. From the study of the basin modeling, the main mature zone reached between 9811 and 11,090 ft in the middle of the Late Cretaceous (84.3–82.5 Ma) is through the L. Kharita Formation with three phases of hydrocarbon generation according to transformation ratio, where the second phase is the main stage in which TR is 5%–50%, showing the beginning of oil expulsion (Ro: 0.73%–0.78%, possibly 0.81%). [ABSTRACT FROM AUTHOR]

The consumption of coals without coking properties in coal blends for coke production is a challenge, precisely because of their lack of coking properties, and in some cases, high contents of macerals from the inertinite group, which are known to contribute to a reduction in the mechanical strength of coke when present in high size dimensions. With the constant search for the use of non-coking coal in the coal blends, the main objective of the study was to investigate the effect of increase inertinite-rich coal content in multi-component coal blends. To achieve this, selective crushing was performed to obtain 1.5 mm as the critical inertinite size for the coke’s mechanical strength, decreasing the amount of microcracks at the boundary between reactive maceral-derived components (RMDC) and inert maceral-derived components (IMDC). The microstructural characterization for the industrial metallurgical coke was studied using optical microscopy associated with image analysis (ImageJ software). It was established that a 25 % content of inertinite-rich coal addition in the blend caused systematic changes in the coke’s microstructural features, decreasing the mechanical strength. Additionally, the segmentation between RMDC and IMDC was studied to achieve better correlation from the coke’s microstructural parameters, predicting mechanical strength (DI150/15). A new equation was proposed describing both microstructural features from reactive and inert components. [ABSTRACT FROM AUTHOR]

The Bozburun coalfield hosts a late Miocene 1.1 m thick coal seam. This study aims to determine coal quality, mineralogy, petrography and geochemistry, and controlling factors of elemental enrichments. The coals are generally black and greyish black in colour, and the low part of the seam commonly includes fossil shell remains. The ash yield displays a decreasing trend towards the upper part of the seam; in turn, gross calorific and total C values increase upwards. The total S content being generally higher than 5% (on dry basis), displays an increasing trend towards the upper part. In the entire seam, huminite is the most common maceral group, while inertinite and liptinite display variable proportions. The identified minerals by XRD are mainly quartz, clay minerals, calcite, pyrite, and aragonite (in fossil shell remains-bearing samples), whereas feldspars and marcasite determined in a few samples. Furthermore, in the coal samples, celestine and barite were identified by SEM-EDX. This study indicates that precipitation of celestine and Sr-bearing barite grains during diagenetic stage and Sr-uptake by mollusc within the palaeomire caused Sr enrichment in the entire seam. Overall, the water influx and redox conditions controlled the mineralogical and the elemental compositions of the coal seam.

Salinized lacustrine shale (SLS) represents a frontier in the global quest for unconventional hydrocarbon resources. The impact of terrigenous input, which includes terrigenous organic matter (OM) and detrital matter, on the deposition and hydrocarbon potential of SLS is still controversial. Here, we examine this issue using the newly discovered SLS within the Paleogene Biyang Depression, employing a combination of organic petrographic and geochemical analyses. A high influx of terrigenous input (terrigenous OM and detrital matter) promotes the formation of SLS. On the one hand, terrigenous higher plants emerge as the primary source of OM in the SLS, as indicated by the dominance of terrigenous macerals (e.g., terrigenous liptinite) and the abundance of plant-derived biomarkers (e.g., tricyclic terpanes). Additionally, a portion of the OM may originate from bacteria. On the other hand, the rapid input of detrital matter improves the preservation of OM, resulting in the deposition of SLS with high total organic carbon (TOC) contents and low hydrogen index (HI) values. The findings of this study contribute to a deeper understanding of SLS deposition and provide guidance for regional hydrocarbon exploration. [ABSTRACT FROM AUTHOR]

Two hundred and fifty single first-order Arrhenius reactions are simulated to generate S2 pyrograms at three heating rates 25, 15, and 5 °C·min−1. The activation energy (E) and pre-exponential factor (A) of the reactions simulated follow a long-established trend of those variable values displayed by shales and kerogens. The characteristics of the transformation fraction (TF) profiles (product generation window temperatures) of the simulated single reactions are compared to the TF profiles of recorded shale pyrograms generated by multiple reactions with different E-A values lying near the defined E-A trend. Important similarities and differences are observed between the TF profile values of the two datasets. The similarities support the spread of E-A values involved in shale pyrogram best fits. The differences are most likely explained by the complexity of the multiple kerogen first-order and second-order reactions contributing to the recorded shale pyrograms versus the simplicity and crispness of the single first-order reactions simulated. The results also justify the validity of using the previously described "variable E-A pyrogram-fitting method" of multi-heating-rate shale pyrograms enabling optimizers to choose multiple reactions from an unlimited range of E-A values. In contrast, further doubt is cast on the validity of the constant-A pyrogram-fitting method used by the Easy%Ro technique, in that a distribution of reactions with a single A value is unlikely to represent the complex variety of kerogen macerals observed in shale formations. TF profiles generated by the variable E-A pyrogram-fitting method lie close to the established E-A trend and are likely to provide more realistic TF generation window temperatures than TF profiles generated by the constant-A pyrogram-fitting method. [ABSTRACT FROM AUTHOR]

There is a lack of published literature on coal deposits in Madagascar. The Imaloto Basin is a sub-basin of the Morondava Basin, Southwestern Madagascar, and hosts the Sakoa Coal Measures. The aim of this study was to increase our understanding of the petrography, geochemistry, and mineralogy of coal deposits hosted in the Imaloto Basin. Three coal seams (from the bottom: Main Seam, Upper Seam, and Top Seam) were intersected during a drilling program conducted by the Lemur Holdings in 2019. Coal samples were characterized using organic petrography (type and rank determination); the ash chemistry was assessed (XRF), and the mineralogy was considered using X-ray diffraction. The depositional environment at the time of peat accumulation was considered. The Main Seam samples are of better quality compared to the Upper Seam and Top Seam samples in terms of calorific value (CV) and ash yield. The coals are borderline Sub-bituminous Low Rank A to Bituminous Medium Rank D. An abundance of inertinite macerals was determined in the Main Seam, while the Upper and Top Seams are more vitrinite-rich. An unusual mineral, possibly albite or analcime, was determined in samples with a high Na content. The Imaloto coal samples show varied depositional settings (dry forest swamp, wet forest swamp, and piedmont plain), which influences coal quality. [ABSTRACT FROM AUTHOR]

The porosity characteristics of coal seams serve as a pivotal factor in assessing the development potential of coalbed methane (CBM) resources, significantly influencing the adsorption and permeability capabilities of coal reservoirs, as well as the accumulation, entrapment, and preservation of CBM. In this study, we focused on the coal seams of the Xishanyao Formation in the western part of the southern Junggar Basin (NW China). By leveraging the complementarity of nuclear magnetic resonance (NMR), low-temperature liquid nitrogen experiments, and high-pressure mercury intrusion porosimetry (MIP) in spatial exploration range and precision, we conducted a comprehensive analysis to achieve a fine description of porosity characteristics. Furthermore, we explored the coal petrology factors controlling the pore characteristics of the Xishanyao Formation, aiming to provide geological evidence for the selection of favorable areas and the development potential evaluation of CBM in the study area. The results indicate the following: (1) The total pore volume of the coal samples is 6.318 × 10−3 cm3/g on average, and the micropore volume accounts for a relatively high proportion (averaging 44.17%), followed by the fine pores (averaging 39.41%). The average porosity is approximately 3.87%, indicating good gas storage and connectivity of the coal seams, albeit with some heterogeneity. The coal reservoir is dominated by micropores and fine pores with diameters less than 100 nm, and the pore structure is characterized by low pore volume and high pore area. (2) The pore structure is influenced by both the coalification degree and the coal maceral. Within the range of low coalification, porosity increases with the increase in coalification degree. Building upon this, an increase in the vitrinite content promotes the development of micropores and fine pores, while an increase in the inertinite content promotes the development of meso–macropores. The clay mineral content exhibits a negative correlation with the adsorption pore volume ratio and a positive correlation with the seepage pore volume ratio. [ABSTRACT FROM AUTHOR]

This study investigates the paleodepositional conditions of the No. 6 Seam of the Madzaringwe Formation in Makhado and Voorburg south area of the Soutpansberg Coalfield (Limpopo Province, South Africa) utilizing organic petrography and inorganic geochemical proxies. The coals are predominantly high-volatile bituminous B-A rank with high ash yields (avg. 36.1 wt%), characterized by high-vitrinite (~ 41.5 vol%), moderate-to-high inertinite (9.8 vol%–33.7 vol%) and low liptinite (~ 2.3 vol%). The distribution of inertinite varies among different coal horizons (from bottom-lower to middle-upper), suggesting differential oxidation conditions and/or paleofire occurrence. Vitrinite-to-inertinite (V/I) ratio, tissue preservation–gelification index (TPI–GI), and groundwater–vegetation index (GWI–VI) plots, indicate that the peat-forming forest-swamp vegetation accumulated under mesotrophic-to-rheotrophic hydrological conditions. The presence of structured macerals (i.e., telinite, collotelinite, fusinite, and semifusinite) suggests well-preserved plant tissues, whereas framboidal pyrite and sulphur content (0.24 wt%–2.16 wt%) point to brackish-water influence at the peat stage. The coals contain quartz, kaolinite, siderite, muscovite, dolomite, calcite, and pyrite minerals, most of which were likely sourced from felsic igneous rocks. The Al/(Al+Fe+Mn) and (Fe+Mn)/Ti ratios for the studied samples range between 0.24–0.97 and 0.57–70.10, respectively. The ratios, Al–Fe–Mn plot, and presence of massive botryoidal-type pyrite imply some influence of meteoric waters or fluids from hydrothermal activity post-deposition. Moreover, the chemical index of alteration (CIA: 98.25–99.67), chemical index of weathering (CIW: 92.04–97.66), and A–CN–K ternary diagram suggest inorganic matter suffered strong chemical weathering, indicating warm paleoclimatic conditions during the coal formation. [ABSTRACT FROM AUTHOR]

This study investigated the differences and correlation between the occurrence characteristics of alkali and alkaline earth metals (AAEMs) among different maceral groups in high-alkali, high-inertinite coal, and provides scientific guidance for the co-separation of AAEMs and inertinite groups in Xinjiang coal. The total AAEMs of inertinite-enriched samples were significantly higher than those in raw coals and vitrinite-enriched samples. Five-step sequential extraction showed that Na mainly occurs as water-soluble sodium (Na-Water) in raw coal and inertinite-enriched samples, accounting for about 53% of the total content, while it exists as organic sodium (Na-NH4Cl and Na-EDTA) in vitrinite-enriched samples, accounting for about 52% of the total content. Ca and Mg are both mainly present in organic form (Ca/Mg-NH4Cl and Ca/Mg-EDTA) in all the samples, with slightly higher proportions present in vitrinite-enriched samples. The contents of K are low in all the samples, which exist in an insoluble state (K-I). Combined microscopy and SEM-EDS analyses have revealed that the localized enrichment of Na in raw coal and inertinite-enriched samples occurs in the inertinite cell cavity, which primarily exists as NaHCO3 combined with quartz crystals, with a maximum content of up to 5.85 wt%. In this study, although EDS spectra could not directly characterize organic Ca and Mg, dolomite and calcite minerals were repeatedly found in the inertinite cell cavity. Moreover, the contents of Ca and Mg in the vitrinite-enriched samples were significantly lower than those in the other samples, which suggests that Ca and Mg are enriched with the inertinite groups. The localized enrichment of AAEMs could not be detected in any of the vitrinite-enriched samples. In summary, though there are significant differences between the occurrence modes of AAEMs in different maceral groups of high-alkali coal, AAEMs have a strong affinity with inertinite, which may be due to the inertinite's abundant pore structures. [ABSTRACT FROM AUTHOR]

The comprehensive quality enhancement and grading of coal are crucial methods for unlocking the high value-added and low-carbon utilization of coal resources. In this work, the influence of oily bubbles on the flotation of Shendong Jurassic vitrinite-rich coal and inertinite-rich coal was studied via flotation tests, Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle detection, and induction time measurements. FT-IR and XPS analyses demonstrated that the surface of inertinite-rich coal contains more hydrophilic oxygen-containing functional groups. Contact angle and induction time measurements showed that the vitrinite-rich coal is more hydrophobic than inertinite-rich coal, and that for both air and oily bubbles, the induction time on the surface of vitrinite-rich coal is shorter than that on the surface of inertinite-rich coal. In addition, rather remarkably, the induction times for both vitrinite-rich coal and inertinite-rich coal are significantly reduced by oily bubbles. Finally, a better flotation performance for oily bubble flotation of vitrinite-rich coal and inertinite-rich coal was found. It appears that oily bubble flotation is an efficient method for enhancing the recovery of vitrinite-rich coal and inertinite-rich coal. [ABSTRACT FROM AUTHOR]

Coal is a solid combustible mineral, and coal-bearing strata have important hydrocarbon generation potential and contribute to more than 12% of the global hydrocarbon resources. However, the deposition and hydrocarbon evolution process of ancient coal-bearing strata is characterized by multiple geological times, leading to obvious distinctions in their hydrocarbon generation potential, geological processes, and production, which affect the evaluation and exploration of hydrocarbon resources derived from coaly source rocks worldwide. This study aimed to identify the differences on oil-generated parent macerals and the production of oil generated from different coaly source rocks and through different oil generation processes. Integrating with the analysis of previous tectonic burial history and hydrocarbon generation history, high-temperature and high-pressure thermal simulation experiments, organic geochemistry, and organic petrology were performed on the Carboniferous-Permian (CeP) coaly source rocks in the Huanghua Depression, Bohai Bay Basin. The oil-generated parent macerals of coal's secondary oil generation process (SOGP) were mainly hydrogen-rich collotelinite, collodetrinite, sporinite, and cutinite, while the oil-generated parent macerals of tertiary oil generation process (TOGP) were the remaining small amount of hydrogen-rich collotelinite, sporinite, and cutinite, as well as dispersed soluble organic matter and unexhausted residual hydrocarbons. Compared with coal, the oil-generated parent macerals of coaly shale SOGP were mostly sporinite and cutinite. And part of hydrogen-poor vitrinite, lacking hydrocarbon-rich macerals, and macerals of the TOGP, in addition to some remaining cutinite and a small amount of crude oil and bitumen from SOGP contributed to the oil yield. The results indicated that the changes in oil yield had a good junction between SOGP and TOGP, both coal and coaly shale had higher SOGP aborted oil yield than TOGP starting yield, and coaly shale TOGP peak oil yield was lower than SOGP peak oil yield. There were significant differences in saturated hydrocarbon and aromatic parameters in coal and coaly shale. Coal SOGP was characterized by a lower Ts/Tm and C31-homohopane22S/ (22Sþ22R) and a higher Pr/nC17 compared to coal TOGP, while the aromatic parameter methyl dibenzothiophene ratio (MDR) exhibited coaly shale TOGP was higher than coaly shale SOGP than coaly TOGP than coaly SOGP, and coal trimethylnaphthalene ratio (TNR) was lower than coaly shale TNR. Thus, we established oil generation processes and discriminative plates. In this way, we distinguished the differences between oil generation parent maceral, oil generation time, and oil production of coaly source rocks, and therefore, we provided important support for the evaluation, prediction, and exploration of oil resources from global ancient coaly source rocks. [ABSTRACT FROM AUTHOR]

The Middle Jurassic Walloon Subgroup coals in Australia's Surat Basin are extremely rich in low-medium rank coal seam gas (CSG) resources, making it one of the world's most productive CSG development basins. The desorption, diffusion and seepage behaviors of CSG are remarkably influenced by the pore–fracture structure characteristics of coals; therefore, their detailed characterizations are greatly significant for CSG exploration and development. There are, however, currently few researches on the pore–fracture structure characteristics of Surat Basin coals. Thus, 12 low-medium rank coals ( R ¯ r: 0.42–0.60%) from the Walloon subgroup of Eastern Surat Basin were obtained for this study, and then coal petrology analyses, field emission scanning electron microscopy and nuclear magnetic resonance (NMR) experiments were performed on these samples. The results show that the organic macerals of Surat coals are dominated by vitrinite, followed by liptinite, and the inertinite is generally rare. The average porosity, movable porosity and movable water saturation of the coal samples were 5.08%, 1.01% and 22.47%, respectively. The coal samples' pore–fracture structure was characterized by an overwhelming predominance of MIT (micropores and transition pore) and relatively less developed ME (mesopore) and MAF (macropore and fracture), with average volume proportions of 74.58%, 14.06% and 11.36%, respectively. The movable porosities of different pore–fracture structure types were obtained, and the average values were presented as MAF > ME > MIT. The NMR experiments showed that the average movable spaces in the MIT, ME and MAF of the coal samples were 6.6%, 41.8% and 97.9%, respectively. The pore–fracture structure of the sampled coals was influenced by coal maturity, as well as the coal macerals. The coal facies have some impacts on the porosities of coal samples, and the coals with higher texture preservation index and vegetation index, and lower gelation index overall have higher porosities. [ABSTRACT FROM AUTHOR]

The hydrocarbon generation potential of the Campano-Maastrichtian to Paleogene shales from the Benin Flank (located in SW Nigeria) of the Anambra Basin, has been previously investigated mostly by studying outcrops and by relatively few subsurface data-based studies. Thus, it is expedient undertaking an assessment of the hydrocarbon generation potential of this frontier area from subsurface samples. Campano-Maastrichtian to Paleogene shale samples obtained from Egoli-1 borehole in the Benin Flank of the Anambra Basin are studied by means of HAWK programmed pyrolysis, organic petrography, and mineralogy (XRD), with the aim to explore the petroleum-generating potential and the thermal maturity. The obtained results display a significant variation of the TOC content ranging from very low (5%), indicating poor to excellent oil potential based on S2 values under the condition, of course, the studied formations reached the oil window. The shales of the Nsukka and Imo Formations display lower petroleum-generating potential than these of the Mamu Formation. All the studied samples are dominated by gas-prone (type III) and inert (type IV) kerogens, with few displaying mixed II/III (oil- and gas-prone). The organic-petrography observations support partly the results of the HAWK programmed pyrolysis, as they reveal an organic-richer Mamu Formation in comparison to the Nsukka and Imo Formations; huminite/vitrinite particles (both indigenous and recycled) along with variable contents of liptinite (mostly alginite and bituminite) and inertinite macerals (mostly inertodetrinite) are hosted in the shales. The latter display a typical composition for fine-grained clastic sediments; mostly kaolinite, illite/montmorillonite, quartz, and subordinately, anatase. In terms of thermal maturity, huminite/vitrinite reflectance data points to immature stage; however, the occurrence of solid bitumens, displaying equivalent vitrinite reflectance values within the oil window, points to an active petroleum system in sequences deeper than the examined ones.

To investigate the influence of organic matter conversion on the evolution of organic matter pores, fractional conversion (TRHI) and loss of TOC (TOCL) from the organic matter conversion of Middle Jurassic Dameigou Formation shale samples were calculated using petrographic analysis. The TRHI of organic matter varies from 0.30 to 0.88 and TOCL content ranges from 0.62% and 4.09%. Relative to samples of Type III organic matter in shales, type II samples exhibit higher TRHI and TOCL values. Petrographic calculations of TRHI reveal that the fractional conversion of different kerogens differs for the same thermal maturity level. The specific surface area (SBET) ranges between 1.25 and 6.63 m2/g and micropore surface area (Smic) ranges between 4.16 and 21.27 m2/g. Correlations between pore structure parameters and TOCL content are higher than those between pore structure parameters and TOC content. The original TOC content decreases with increasing maturity level owing to hydrocarbon generation from organic matter conversion. The development of organic matter pores depends mainly on organic matter conversion, which is influenced by the richness, organic maceral compositions, and thermal maturity of the organic matter. The contents of kaolinite, illite, and mixed-layer illite/smectite (I/S) in the studied shales are 17.83%–37.05%, 5.36%–11.31%, and 5.27%–14.36%, respectively. Pore structure parameters (SBET and Smic) exhibit moderate positive correlations with illite content and I/S content, and moderate negative correlations with kaolinite content, indicating that different clay minerals have differential effects on pore structure. [ABSTRACT FROM AUTHOR]

Opencast coal mining produces trash of soil and rock containing various minerals, that are usually dumped nearby the abandoned sites which causes severe environmental concern including the production of acid mine drainage (AMD) through oxidation pyrite minerals. The current study entailed assessing the potential production of AMD from an opencast coal mining region in Northeast part of India. In order to have a comprehensive overview of the AMD problem in Makum coalfield, the physico-chemical, geochemical, and petrological characteristics of the coal and overburden (OB) samples collected from the Makum coalfield (Northeast India) were thoroughly investigated. The maceral compositions reveal that coal features all three groups of macerals (liptinite, vitrinite, and inertinite), with a high concentration of liptinite indicating the coal of perhydrous, thereby rendering it more reactive. Pyrite (FeS2) oxidation kinetics were studied by conducting the aqueous leaching experiments of coal and (OB) samples to interpret the chemical weathering under controlled laboratory conditions of various temperature and time periods, and to replicate the actual mine site leaching. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was operated to detect the disposal of some precarious elements from coal and OB samples to the leachates during our controlled leaching experiment. The Rare earth element (REE) enrichment in the samples shows the anthropogenic incorporation of the REE in the coal and OB. These experiments reveal the change in conductivity, acid producing tendency, total dissolved solid(TDS), total Iron(Fe) and dissolved Sulfate(SO42−) ions on progress of the leaching experiments. Moreover, the discharge of FeS2 via atmospheric oxidation in laboratory condition undergoes a significant growth with the rise of temperature of the reaction systems in the environment and follows pseudo first order kinetics. A bio-remediative strategies is also reported in this paper to mitigate AMD water by employing size-segregated powdered limestone and water hyacinth plant in an indigenously developed site-specific prototype station. Apart from neutralisation of AMD water, this eco-friendly AMD remediation strategy demonstrates a reduction in PHEs concentrations in the treated AMD water. [ABSTRACT FROM AUTHOR]

The energy demand increased dramatically owing to the evolution of industrial and domestic requirements and the associated decrease in oil and gas resources. This study aims to evaluate El-Maghara coal (with about 52 MT reserve) as a potential hydrocarbon source. The collect samples were subjected to petrographic, chemical analyses and Rock–Eval pyrolysis to investigate the detailed characteristics of this coal. Chemically, this coal is high volatile bituminous coal with high H and S content. The high H/C ratio indicates the high extraction yield of coal. The main maceral group in the studied samples is vitrinite (62.8%) followed by liptinite (31.3%) and inertinite (5.8%). The content of liptinite indicates the capability of this coal for petroleum production. Based on Rock–Eval Pyrolysis results and TOC content, the coal has excellent petroleum potential. The hydrogen index (HI) and H/C atomic ratio indicate the II kerogen type (oil prone) of this coal. This coal has Tmax and vitrinite reflectance values around 415.8 °C and 0.37%, respectively, indicating the immature stage of kerogen. The high reactive maceral content (94.2%), oil-yield (65.5%) and conversion from coal to oil (95.4%), indicated that this coal has a hydrocarbon generation potential for oil. [ABSTRACT FROM AUTHOR]

The open-pit exploitation of the Maritsa Iztok lignite field (Bulgaria) generated sedimentary waste rocks of low organic matter content that were deposited in internal dumps. Immediately after deposition the re-deposited sediments underwent weathering, including organic matter oxidation leading in some cases to self-heating. The aims of the research were to study the impact of weathering and self-heating on the maceral alterations in the dump site associated with the sediment re-deposition, and organic compounds identification and distribution. The 27 samples collected from Troyanovo-3 Mine internal dump differed in degree of alteration. The first group contained unaltered macerals and showed normal distribution of n-alkanes, phenols were absent and Rock-Eval Tmax ranged from 420 to 430 °C. The second group contained macerals with irregular cracks, paler oxidation rims, higher reflectance, Gaussian distribution of n-alkanes, high concentration of phenols and PAHs, and lowered Tmax values (below 400 °C). The samples contained elevated amount of pyrite which oxidation might contribute to self-hating. [ABSTRACT FROM AUTHOR]

A comprehensive petrographic and biomarker study has been performed to evaluate sources, paleoenvironment and maturity of organic matter (OM) in coal samples taken from the borehole BD-4 in the Dubrava block (Aleksinac Basin, Serbia). Studied samples are dominated by vitrinite group macerals, with variable content of liptinite and very low amount of inertinite. The measured random vitrinite reflectance, Rock Eval data and biomarker assemblages confirmed subbituminous rank of coal. The OM is at the late diagenetic and early catagenetic stage. Contents of total organic carbon and mineral matter vary in wide range, indicating frequent changes of depositional settings. Content of sulphur is moderate to very high. The main sources of OM in Aleksinac coal were angiosperms, ferns and aquatic macrophytes, with subordinate contribution of conifer paleovegetation. Diagenetic alteration of OM was governed by methanotrophic bacteria and chemoautotrophic bacteria. Deposition of OM occurred in a low-lying mire environment, showing decreasing concentration of sulphate ions upward the borehole BD-4. The coal deposition was terminated by rise of water level, which led to drowning of the mire and transition to lacustrine environment. [ABSTRACT FROM AUTHOR]

The petrographic composition of samples from Suhostrel and Bobov Dol coal deposits was studied using optical microscopy. The maceral contents were further used to calculate maceral ratios which were interpreted in terms of environmental condition during peat deposition. Petrographic data of Suhostrel coal is compatible with its organic geochemical characteristics and indicate peat formation under inundated topogenous, meso- to rheotropic, sparsely forested marsh- or fen-type environment. Coal facies diagrams for Bobov Dol coal, however, provide contradictory depositional settings and therefore cannot be used alone for environmental reconstruction. [ABSTRACT FROM AUTHOR]

Fifty-four coal clast samples in the siliciclastic rocks (e.g., sandstone and conglomerate) were collected from cores of two-deep research wells (K20H and K20K) drilled at the Kozlu coalfield in Zonguldak Basin, and for the first time, they were evaluated using mineralogy by XRD and SEMEDX and random vitrinite reflectance (%Rr) measurements in order to find out their origin and timing. Petrographic observations on polish surfaces show that the coal clasts are either entirely xylitic/vitrinitic particles or coals including a broader range of macerals. The detected minerals in the samples are mostly derived from the parental coal seams and, to a lesser extent, precipitated from penetrated pore-water in the cleats/fractures of clasts. The %Rr values of coal clasts in Carboniferous sediments are generally relatively higher than those measured in the coal seams due to weak oxidation during transportation. Furthermore, similar mineralogical and maceral compositions between coal clasts and coal seams imply that these clasts were mainly eroded during the peatification and/or early coalification of parental seams and display similar coalification patterns. The close %Rr value of a coal clast sample in the Early Aptian Zonguldak Formation and Carboniferous coal seams could suggest that this coal clast sample is presumably derived from the coal seams eroded during Early Aptian. [ABSTRACT FROM AUTHOR]

The Bozburun coalfield hosts a late Miocene 1.1 m thick coal seam. This study aims to determine coal quality, mineralogy, petrography and geochemistry, and controlling factors of elemental enrichments. The coals are generally black and greyish black in colour, and the low part of the seam commonly includes fossil shell remains. The ash yield displays a decreasing trend towards the upper part of the seam; in turn, gross calorific and total C values increase upwards. The total S content being generally higher than 5% (on dry basis), displays an increasing trend towards the upper part. In the entire seam, huminite is the most common maceral group, while inertinite and liptinite display variable proportions. The identified minerals by XRD are mainly quartz, clay minerals, calcite, pyrite, and aragonite (in fossil shell remains-bearing samples), whereas feldspars and marcasite determined in a few samples. Furthermore, in the coal samples, celestine and barite were identified by SEM-EDX. This study indicates that precipitation of celestine and Sr-bearing barite grains during diagenetic stage and Sr-uptake by mollusc within the palaeomire caused Sr enrichment in the entire seam. Overall, the water influx and redox conditions controlled the mineralogical and the elemental compositions of the coal seam. [ABSTRACT FROM AUTHOR]

Macerals are the basic constituents of coal that can be distinguished and identified under the microscope. Depending on the difference in optical properties, the macerals are divided into four maceral groups, including liptinite, vitrinite, huminite and inertinite. These maceral groups not only affect coal mining and utilization but also play different roles in coal beneficiation. According to the different properties of maceral groups, they can be separated (or enriched) to provide high-quality raw materials for the coal industry. This review briefly introduces the international maceral classification system and reviews in detail the role of maceral groups in coal beneficiation combined with their properties. [ABSTRACT FROM AUTHOR]

The Fu 2 Member of the Paleocene Funing Formation in the Gaoyou Depression, Subei Basin is an organic matter-rich formation, and has a high potential for shale oil exploration and exploitation. Total organic carbon (TOC), organic petrography, Rock-Eval pyrolysis, chloroform bitumen “A” extraction, and SARA (saturates/aromatics/resins/asphaltenes) composition analyses of shale samples from one drill core in the studied area spanning a thickness of 257 m were conducted to study the organic matter (OM) richness, kerogen type, maceral composition, hydrocarbon generation potential, and oil content of the Fu 2 Member. Results show that the Fu 2 Member shales in the study area have a Ro of 0.87%, in the peak oil window, suggesting a high potential for hydrocarbon generation. The studied OM in shales mainly belongs to kerogen Type II, with a minor portion of Type I and Type III. Under microscopic observation, macerals in the studied shales are mainly composed of vitrinite, inertinite, alginite, and solid bitumen. The studied shales have an average TOC content of 1.41 wt%, indicating good petroleum potential. The variations of maceral compositions could affect the reliability when the Tmax is used as an indicator of thermal maturity. The lower Shale 4 and upper Shale 5 interval (3650–3700 m), with high TOC and high oil saturation index, is identified as the sweet-spot interval of the Fu 2 Member for shale oil exploration.

The Orzesze-1 exploratory well with a depth of 3708 m (TVD) was drilled in 2019–2020 in the depocentre of the Upper Silesian Coal Basin (USCB). The methane content in the coal seams has been tested to a depth of 2840 m and the sorption capacity of the coal to a depth of 2576 m. These are the deepest measurements in the USCB so far. The vertical distribution of methane content in the borehole shows two depth zones of interest, the first at a depth 883 m to about 1300 m (maximum methane content about 12 m3/t coaldaf) and another in the range of 1500–2840 m, that is, to the maximum measurement depth, so the actual lower boundary depth of this zone is unknown. The maximum methane content here exceeds 18 m3/t coaldaf at a depth of >2800 m. Both zones are separated by an interval of reduced methane content of about 5 m3/t coaldaf at a depth of approximately 1400 m. The gas composition is dominated by methane (∼90%), and the content of carbon dioxide increases to approximately 15% at a depth of >2300 m. The methane-bearing zone at ∼900–1300 m corresponds to the zone of high- and medium-volatile bituminous coal (second coalification jump), while the highest methane content at a depth of >2800 m was determined in anthracite. The methane sorption capacity of the coal seams oscillates between 16 and 40 m3/t coaldaf with a maximum in anthracite at a depth of >2800 m, where the temperature of the rock approaches 100 °C and the deposit pressure exceeds 28 MPa. The highest sorption capacity in anthracite results from its inner structure characterised by the predominance of ordered aromatic lamellas and the dominance of vitrinite macerals (>70%), which contain coal micropores accumulating adsorbed methane. The comparison of the sorption capacity of the tested coal and the measured methane content displays undersaturation of 11–59%, however, due to significant gas content in the deep zone (depth > 1500 m), the drilling area can be considered as a prospect for further exploration and development of coalbed methane (CBM). • A vertically extensive zone of maximum gas contents was found in the USCB depocentre. • Anthracite has the highest methane content and sorption capacity. • Methane is the main gas component, but the CO 2 content reaches >15% at a depth of >2500 m. • Coal is characterised by significant methane undersaturation and low permeability. • Work on deep CBM mining technology should be continued due to the promising gas-bearing potential of the area. [ABSTRACT FROM AUTHOR]

• Carboxylate salts decrease tar yield but increase carbon conversion and gas yield. • Understanding mode of occurrence of mineral matter is vital for efficient carbon conversion. • H+ transfer by Ca/Mg/Fe-acetate composite promotes the formation of CH 4 and H 2. • Sulphur capturing was facilitated by carboxylate salts. The role of mineral-matter in coal significantly influences pyrolysis, yet there is no consensus on the behavior of inherent-minerals and carboxylate salts during coal or fine-coal reject (FCR) pyrolysis. This study investigates the effects of carboxylate salts (Ca(C 2 H 3 O 2) 2 , Mg(CH 3 COO) 2 ·4H 2 O, and Fe(C 2 H 3 O 2) 2 composite (CSC) on FCR, demineralized FCR (FCRD), and demineralized > 1.9 g/cm3 FCR sink fraction (SI1.9D) in a Fischer-assay double retort set-up under the following pyrolysis conditions: 500 °C and heating rate of 5 °C/min for 3 hours in nitrogen. Analytical techniques identified kaolinite, quartz, dolomite, siderite and calcite, and characterized tar precursors, functional groups, carbon associations, and species evolution in FCR, FCR+CSC, FCRD+CSC, SI1.9D, SI1.9D+CSC and their chars. FCR+CSC exhibited the fastest decomposition rate due to extraneous-minerals and CSC interactions. FCRD+CSC and FCR+CSC achieved the highest carbon conversion, tar yield and gas yield, and the lowest char yield compared to SI1.9D and SI1.9D+CSC. The CSC addition increased the S proportion in FCRD+CSC and SI1.9D+CSC chars due to the H 2 S in-situ capturing to form nano-sulfides and S-bearing amorphous phases. Also, the SI1.9D+CSC blend released a higher CO 2 via inherent nano-carbonates reacted with H 3 O+ from kaolinite/illite transformation, the HF/HCl aqueous solution and acetate decomposition. Tar yield, polycyclic aromatics, alkylated phenolics, and naphthalene compounds decreased due to hydrogen transfer by CSC, inhibiting secondary cracking of intermediate vapors. These results highlight the catalytic potential of carboxylate salts, dependent on inherent-minerals and dominating maceral groups during coal pyrolysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • FTIR analysis to quantity the molecular structure of liptinite-rich coals. • Molecular structure of liptinite-rich coals is compared with pure amber. • Molecular structure is affected by maceral composition, coal-forming plants and maturity. • FTIR parameter can characterize the molecular structure of liptinite-rich coals. As one of the important components in low-rank coals, liptinite plays an indispensable role in the formation and utilization of coal, thus, understanding the occurrence and structures of liptinite-rich coals provides a theoretical basis for the origin and clean utilization of coals. In this study, the occurrence of liptinite and the functional groups and molecular structure of different liptinite-rich coals were quantitatively characterized by using optical microscope and Fourier transform infrared spectroscopy (FTIR), respectively. The results showed that the sample JS-7 from Yunnan Province mainly enriched sporinite and bituminite, the sample JS-15 from Yunnan Province is rich in dispersed resin and the amber-rich coal from Liaoning Province mainly contains bulk resin. The FTIR results indicated that the amber-rich coal, the sample JS-7 and pure amber (Liaoning Province) consist mainly of trisubstituted benzene. The sample JS-7 has the highest content of trisubstituted benzene (63.4%) due to the high content of sporinite and bituminite. The sample JS-15 is mainly composed of tetrasubstituted and pentasubstituted benzene, which may be relevant to the cyclization of aliphatic chains and the decarboxylation reaction of benzene rings. The C C group has not been detected in the sample JS-7 and pure amber. The FTIR structural parameters indicate that the pure amber has the lowest maturity, the lowest degree of aromatization, but the highest hydrocarbon generation potential. The highest CH 2 /CH 3 group value (14.69) and the lowest A factor value (0.36) of the sample JS-15 indicate a well-developed aliphatic chain structure and lowest hydrocarbon generation potential, respectively, which probably caused by the low content of C O group. [ABSTRACT FROM AUTHOR]

Liquid CO 2 has similar properties to non-polar hydrocarbon oils and can be used to achieve hydrophobic aggregation separation of coal macerals. To reveal the influence of the water-liquid CO 2 treatment on the interfacial properties of vitrinite and inertinite, the effects of the water-liquid CO 2 system on the interfacial properties of vitrinite and inertinite were investigated by SEM, BET, FTIR, and XPS. The results showed that the content of oxygen-containing functional groups on the coal macerals were reduced more significant than the hydrocarbons due to the physical adsorption and chemical extraction of liquid CO 2 , which led to an increase in the hydrophobicity of vitrinite and inertinite. The higher porosity and specific surface area of inertinite causing the decrease in the content of oxygen-containing functional groups in inertinite was greater than that in vitrinite. This study provides theoretical support for the separation of coal macerals using liquid CO 2 hydrophobic agglomerates. [Display omitted] • Water-liquid CO 2 treatment increases the hydrophilicity of vitrinite and inertinite. • Liquid CO 2 has a more significant hydrophobic modification effect on inertinite. • Water-liquid CO 2 treatment increases the zeta potential of vitrinite and inertinite. • Liquid CO 2 is more effective in extracting oxygen-containing functional groups. [ABSTRACT FROM AUTHOR]

The Upper Carboniferous organic-rich sediments record the depositional transition from terrestrial to marine environment across the Shiqiantan Formation-Batamayineishan Formation boundary. The geochemical characteristics of source rocks deposited in such terrestrial-marine transitional environments are not clear. The Late Carboniferous palaeovegetation, palaeoclimate and palaeoredox conditions are comprehensively reconstructed by combining organic petrology, molecular biomarkers, stable carbon isotopes and elemental composition. The molecular composition characteristics and stable carbon isotope compositions suggest a major terrestrial organic matter input with a lesser contribution of algae. Oxic to suboxic conditions for the Late Carboniferous sediments can be inferred from the elemental composition and biomarker proxies. A wet, cool, and seasonal dry climate during the Late Carboniferous can be deduced based on biomarkers, macerals, and spore and pollen records. The Late Carboniferous period is characterized by the enhanced burial of terrestrial organic carbon, coinciding approximately with the intensification of the Late Paleozoic Ice Age. The expansion of terrestrial floras in the Late Carboniferous is likely associated with the Late Paleozoic Ice Age. • Pteridosperm and conifers played a key role in the palaeovegetation evolution in the late Carboniferous. • Phyllocladane and kauranes can also be biomarkers for the pteridophytes. • The terrestrial-marine transitional sediments were mainly deposited under unstable oxic-suboxic conditions. • The expansion of terrestrial floras in the Late Carboniferous was likely associated with the LPIA. [ABSTRACT FROM AUTHOR]

The significance of the Lark Formation is underscored by the variations in regional depositional environments and climatic conditions that characterized the late Cenozoic sedimentary flux into the Danish North Sea basin. This study marks the first systematic investigation of sedimentary organic matter in the Lark Formation. A total of 391 drill cuttings from 7 wells in the Danish North Sea were collected and analyzed. All 391 samples were analyzed by pyrolysis geochemistry, and thirty-eight were examined petrographically using reflected light to document maceral composition. This allowed the investigation into spatial and temporal variations in the distribution and properties of organic matter within the Danish North Sea Basin from the latest Eocene to the Middle Miocene. The results reveal that the organic matter comprises primarily Type III kerogen and is thermally immature, as indicated by thermal indicators (T max < 430 °C, mean HRo = 0.3%, mean R/G = 0.51). The kerogen is predominantly composed of huminite (abundant), liptinite (less abundant), and inertinite (trace quantity) macerals. The increasing trend in total organic carbon (TOC) commenced mainly in the northeastern part of the basin (F-1 well) in the late Oligocene. From the late Oligocene to the Early and Middle Miocene, there was a progressive clockwise shift in this increasing trend of sedimentary organic carbon content towards the southernmost part of the Danish North Sea basin (Adda-3, E-1, Dany-1X and Jens-1 wells). The results of the analysis further demonstrate that this rise in sedimentary organic carbon is primarily driven by the increased content of huminite and inertinite. Given the immaturity of the organic matter and its consistent preservation conditions, the spatial and temporal increase in the abundance of huminite and inertinite is attributed to the influx of allochthonous organic matter from terrestrial sources. This influx was primarily influenced by climatic changes and subsequent alterations in runoff. Lower runoff during cooler and drier climates from the latest Eocene to the late Oligocene resulted in a low influx of allochthonous organic matter. Conversely, higher runoff during warmer and more humid conditions in the Early Miocene and earliest Middle Miocene markedly increased its influx. The distribution of allochthonous organic matter in the study area depended on the positioning of basin entrances and depocenters, which respectively determined the supply routes and accumulation sites. This further contributed to the relatively higher abundance of allochthonous organic matter in the areas near the corresponding stratum depocenters. • The first systematic investigation into the organic matter within the Lark Formation. • 391 drill cuttings were obtained for organic petrography and pyrolysis analysis. • The spatial and temporal changes in Total Organic Carbon. • The late Cenozoic allochthonous organic matter flux into the Danish North Sea basin. • The climatic fluctuations and subsequent runoff variations. [ABSTRACT FROM AUTHOR]

We present a case study of high-resolution screening and integration of palynological and organic geochemical methodologies in the TSW-21 well in the Abu Gharadig Basin, north Western Desert of Egypt. A total of 84 cores and cuttings samples were analyzed for TOC wt%, Rock–Eval pyrolysis, molecular geochemistry, vitrinite reflectance (Ro%), and palynology. The categorization of dispersed organic matter in palynological macerals shows that it differs not only in palynofacies properties but also in distinct palynomorph characteristics (mainly abundance, diversity, marine versus non-marine, and preservation). The work highlights the value of integrating optical and geochemical methods in screening hydrocarbon source rock potential, and the implications for kerogen examination and the reconstruction of depositional environments. In the present study, data indicate a marine, near-shore depositional environment of the middle Cretaceous Bahariya Formation, and more open-marine conditions for the overlying strata of the Upper Cretaceous Abu Roash Formation. A variety of kerogen types (II/III, II, III, and IV) is predominant in the Bahariya Formation and is mainly gas-prone (highly phytoclastic and rich in amorphous organic matter [AOM]). In contrast, the Abu Raoash Formation yielded highly oil-prone Type II > I kerogen (AOM-rich). Thermal maturity proxies including Rock–Eval pyrolysis (Tmax), Ro%, and Spore Coloration Index (SCI) reveal that the Bahariya and Abu Raoash formations are immature.Graphical Abstract: We present a case study of high-resolution screening and integration of palynological and organic geochemical methodologies in the TSW-21 well in the Abu Gharadig Basin, north Western Desert of Egypt. A total of 84 cores and cuttings samples were analyzed for TOC wt%, Rock–Eval pyrolysis, molecular geochemistry, vitrinite reflectance (Ro%), and palynology. The categorization of dispersed organic matter in palynological macerals shows that it differs not only in palynofacies properties but also in distinct palynomorph characteristics (mainly abundance, diversity, marine versus non-marine, and preservation). The work highlights the value of integrating optical and geochemical methods in screening hydrocarbon source rock potential, and the implications for kerogen examination and the reconstruction of depositional environments. In the present study, data indicate a marine, near-shore depositional environment of the middle Cretaceous Bahariya Formation, and more open-marine conditions for the overlying strata of the Upper Cretaceous Abu Roash Formation. A variety of kerogen types (II/III, II, III, and IV) is predominant in the Bahariya Formation and is mainly gas-prone (highly phytoclastic and rich in amorphous organic matter [AOM]). In contrast, the Abu Raoash Formation yielded highly oil-prone Type II > I kerogen (AOM-rich). Thermal maturity proxies including Rock–Eval pyrolysis (Tmax), Ro%, and Spore Coloration Index (SCI) reveal that the Bahariya and Abu Raoash formations are immature. [ABSTRACT FROM AUTHOR]

Igneous intrusions induce alterations in coal and minerals. Alteration degree depends upon the in-situ coal rank and maceral composition, the intrusion temperature, heat source proximity, and intrusion size. In the Permo-Carboniferous Fengfeng coalfield, coal rank increases over some 50 km distance south to north from high volatile bituminous coal to anthracite. The coal seams were commonly intruded, and the regional elevation of rank was augmented by Jurassic-Cretaceous igneous intrusions, not just burial coalification. The petrographic examination of a semianthracite from the Dashucun mine in the north of the Fengfeng coalfield shows development of coke microstructure and increased reflectance approaching the dike in the No. 2 Seam. Based on 11 samples at 50-cm horizontal intervals, random vitrinite reflectance value (R r) declines from 5.41% at the contact to the background value of 2.05% at 5-m distance from the contact. Towards the dike, vitrinite anisotropy increases and the microtexture shows development of circular, coarse mosaic, and ribbon anisotropic coke textures and devolatilization vacuoles. Natural coke textures respond to an estimated temperature > 570 °C at the intrusion/coal contact. However, the occurrence of coke structures within a semianthracite reveals a local and regional thermal evolution. Coke textures suggest that coal rank was high volatile A bituminous coal at the time of intrusion. This has implications for burial history, heating, and subsidence rates. Assuming a paleogeothermal gradient of 40 °C/km, high volatile A bituminous coal (1% R r) would have been buried to 3 km at the time of the Jurassic intrusion. The intrusion metamorphosed high volatile bituminous coal to natural coke and subsequent larger-scale regional metamorphism then metamorphosed the coal to semianthracite. [ABSTRACT FROM AUTHOR]

This study investigates the geochemical and petrological characteristics of solid bitumen in the DBH15/73 core from the Furongian (upper Cambrian) and Miaolingian (middle Cambrian) Alum Shale in Billingen, south central Sweden. At Billingen a > 30 m thick Permian diabase (dolerite sill) intruded approximately 100 m above the Alum Shale that promoting the formation of solid bitumen in the uppermost half of the Alum Shale due to enhanced heat flow. The bitumen has been classified into bituminite/diagenetic solid bitumen (DSB), initial-oil solid bitumen (IOSB), and primary-oil solid bitumen (POSB) based on their genesis, morphology and random solid bitumen reflectance (BR o). The Miaolingian shale, constituting the lower part of the Alum Shale, is immature and contains solely bituminite and DSB, with measured BR o ranging from 0.40% to 0.48%. In contrast, the Furongian shale exhibits enrichment in IOSB and POSB and range from marginally mature to peak oil generation with towards the top of the section. Characteristics of uneven heating is seen in the IOSB (BR o : 0.97–1.08%) including oxidation rims and abnormally high maturity surrounding fractures. The POSB (BR o : 0.63–2.01%) is present not only in the Alum Shale but also in the overlying Ordovician Latorp limestone and the underlying Kakeled Limestone Bed, and shows flow structures which is further evidence for migration. The abundance of POSB and IOSB is determined through maceral point counting, revealing POSB as the dominant bitumen type (1.54–7.13 vol%), while IOSB constitutes the minority (0.05–0.31 vol%) within the Furongian shale. This distribution suggests rapid thermal evolution of organic matter within the oil generation window. Additionally, a reduction in free hydrocarbons (Rock-Eval S1), potential hydrocarbons (Rock-Eval S2), and unexpectedly low T max was observed in the Furongian shale. Results indicate that hydrocarbon generation resulting from thermal intrusion contributes to the relatively low S2. Migration of POSB and generated oil to adjacent layers leads to the loss of S1, while the reduced Tmax may be attributed to high uranium content which weakens carbon chain bond energy. These anomalies result in an underestimation when evaluating thermal maturity and kerogen type conversion based on Rock Eval data alone. • Introduce multiphases of solid bitumen in Alum Shale from central Sweden. • Report the solid bitumen migration and its implication on geochemical parameters. • Propose a genetic model describing the genesis of solid bitumen that exposed to heat of diabase intrusion. [ABSTRACT FROM AUTHOR]

Generalizing the rules from complex processes such as catalytic pyrolysis to guide their process control is always a difficult but attractive task. The influences of ion-exchange of metal ions (Na+, K+, Ca2+, Mg2+, Co2+ and Ni2+) on the pyrolysis behavior of vitrinite and inertinite from Shendong coal were investigated by thermogravimetric analyzer-Fourier transform infrared spectrometer (TG-FTIR), fixed-bed reactor (FBR), gas chromatograph-mass spectrometer (GC-MS) and X-ray diffractometer (XRD). A set of machine learning models was successfully constructed based on random forest, support vector machine, and Gaussian process regression, to quantify the relationships between pyrolysis behaviors and the properties of metals and macerals. The leave-one-out-cross validation showed that there are considerable determination coefficients (R2 > 0.9) between predicted and experimental values for most responses (17 out of 29). By combining genetic programming-based symbolic regression with the black-box algorithm, 23 symbolic regression expressions with high confidence were successfully constructed. This work is a pioneering attempt of optimization in small-scale experiments. By utilizing the highly interpretable models, a demand-orientated (multi-)optimization coal pyrolysis can be achieved. The bi-objective optimization was conducted on the yield of tar and the content of light aromatics in tar, and the results show that Co is the optimal loading metal. [Display omitted] • In-situ catalytic pyrolysis of metal ion-exchanged coal macerals was studied. • The pyrolysis behavior of samples was analyzed by TG-FTIR, FBR, GC-MS, XRD etc. • Ion-exchange metal ions reduce char yield and transition metals increase tar yield. • Combine white- and black-box algorithms provides high credible expressions. • Final expressions facilitate the mechanism study and multi-objective optimization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Shendong coal macerals is swelled by acetic acid, ethanol and acetone, respectively. • Based on the coal structure and Py-GC/MS, pathways of phenols formation are proposed. • The reaction energy of phenols generation pathway is carried out by using DFT. • The PCXC yield derived from VD-AT and ID-EA is 43.63 g/kg and 34.19 g/kg, separately. • Among seven pathways of VD-AT, Path 3 exhibits the lowest energy of −148.38 kJ/mol. Phenols are the important high value-added chemical product of coal tar, and exploring the release behavior of phenols is crucial for clarifying the coal pyrolysis mechanism and regulating the product distribution. The aim of this paper is to investigate the effects of swelling on the pyrolytic properties of de-ashed vitrinite (VD) and de-ashed inertinite (ID). VD and ID prepared by Shendong coal were characterized by 13C NMR, XPS and FTIR to explore physicochemical properties. Acetic acid (AA), ethanol (EA) and acetone (AT) were employed to prepare the swelled VD (VD-AA, VD-EA and VD-AT) and swelled ID (ID-AA, ID-EA and ID-AT). Kinetic analysis was carried out using thermogravimetry, the pyrolysis characteristics and distribution of pyrolysis products were analyzed by fast pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) and fast pyrolysis fixed bed. Combining with density functional theory (DFT), the possible pyrolysis pathways of phenols generation were proposed. As a result, the macromolecular structures of VD and ID are constructed. TG and kinetic analysis exhibit that swelling promotes the pyrolysis of VD and ID, and the activation energy of the second stage is VD > VD-EA > VD-AT > VD-AA and ID > ID-EA > ID-AT > ID-AA, respectively. Py-GC/MS analysis exhibits that the selectivity of phenol, cresol, xylenol and catechol decreases to 17.53 % (VD-AA) and 12.18 % (ID-AT). By analyzing and comparing the distribution of the full component of Py-GC/MS, seven possible pathways of cresol generation are proposed. DFT calculation exhibits that Path 3 of VD-AT, which produces cresol via sequential decarboxylation, ether bond cleavage, decarbonylation, aliphatic side chain removal and dehydroxylation, demonstrates the lowest reaction energy of −148.38 kJ/mol. [ABSTRACT FROM AUTHOR]

The organic geochemistry and coal petrology of Palaeogene coals from northeast Greenland (Thyra Ø Island and Kronprins Christian Land) and central Spitsbergen (Longyearbyen and Grumantbyen) were studied using Rock–Eval and gas chromatography–mass spectrometry, as well as microphotometry and maceral group analyses. Bulk data and biomarker distributions of the coals demonstrate a low coal rank for both, but a lower coalification degree of coals from Greenland (0.49–0.55% VRr) compared to those from Svalbard (0.68–0.75% VRr). Maceral group analyses revealed relatively similar distributions with a strong predominance of vitrinite. The generally high abundance of hopanoids (hopanes/hopenes and hopanoic acids) implies a strong bacterial reworking of the organic matter, whereas sulphur occurrences indicate a marine influence after organic matter deposition. A great variety of higher plant biomarkers was detected in all coals. Distinctive compounds recorded in the coals are aliphatic and aromatic diterpenoids as well as partly hydrogenated picenes, suggesting strong input of conifers and angiosperms. Pristane/phytane ratios indicate that the organic matter in the ancient swamps was deposited in an oxic, fluvio-deltaic setting at both sites. This study provides a detailed geochemical investigation of understudied coals from northeast Greenland. Moreover, it enhances our understanding of probably interrelated Palaeogene depositional settings from Greenland and Spitsbergen in terms of their palaeoecology, primary input into coal swamps, and individual thermal history.Relative abundances of GC-MS amenable compound classes in the coal extracts (% of the TOEs). Numbers above the columns give the summed absolute concentrations (in μg/g TOC)Relative abundances of GC-MS amenable compound classes in the coal extracts (% of the TOEs). Numbers above the columns give the summed absolute concentrations (in μg/g TOC)Graphical abstract: The organic geochemistry and coal petrology of Palaeogene coals from northeast Greenland (Thyra Ø Island and Kronprins Christian Land) and central Spitsbergen (Longyearbyen and Grumantbyen) were studied using Rock–Eval and gas chromatography–mass spectrometry, as well as microphotometry and maceral group analyses. Bulk data and biomarker distributions of the coals demonstrate a low coal rank for both, but a lower coalification degree of coals from Greenland (0.49–0.55% VRr) compared to those from Svalbard (0.68–0.75% VRr). Maceral group analyses revealed relatively similar distributions with a strong predominance of vitrinite. The generally high abundance of hopanoids (hopanes/hopenes and hopanoic acids) implies a strong bacterial reworking of the organic matter, whereas sulphur occurrences indicate a marine influence after organic matter deposition. A great variety of higher plant biomarkers was detected in all coals. Distinctive compounds recorded in the coals are aliphatic and aromatic diterpenoids as well as partly hydrogenated picenes, suggesting strong input of conifers and angiosperms. Pristane/phytane ratios indicate that the organic matter in the ancient swamps was deposited in an oxic, fluvio-deltaic setting at both sites. This study provides a detailed geochemical investigation of understudied coals from northeast Greenland. Moreover, it enhances our understanding of probably interrelated Palaeogene depositional settings from Greenland and Spitsbergen in terms of their palaeoecology, primary input into coal swamps, and individual thermal history.Relative abundances of GC-MS amenable compound classes in the coal extracts (% of the TOEs). Numbers above the columns give the summed absolute concentrations (in μg/g TOC)Relative abundances of GC-MS amenable compound classes in the coal extracts (% of the TOEs). Numbers above the columns give the summed absolute concentrations (in μg/g TOC) [ABSTRACT FROM AUTHOR]

• A DGC method is used to enrich the exinite and vitrinite in the exinite-rich coal. • A matrix computation is proposed to represent the exinite-rich coal bonding structure model. • Interaction between exinite and vitrinite in DCL inhibits radical's condensation. • Two stages with different linearity in X c and Y oil with Q H increased is studied. • The optimum temperature for exinite-rich coal in DCL should not exceed 440 °C. The contents of maceral components in coal are one of the key factors influencing the coal conversion in direct liquefaction. The relatively low exinite content in coal has led to a lack of study in the literature regarding its liquefaction behavior. In this study, an isopycnic density gradient centrifugation (DGC) technique was used to obtain four components of an exinite-rich coal. Eight covalent bonds concentrations of the raw coal and four components were calculated based on the results of 13C NMR, elemental analysis, and FTIR, and a matrix computation was proposed to represent the bonding structure model of exinite-rich coal. Based on the typical bonding structure model of exinite-rich coal, the liquefaction of exinite and vitrinite components was studied in a hydrogen donor solvent medium, and the interaction between exinite and vitrinite in direct liquefaction was also explored. The effect of interaction on products composition and hydrogen donation quantity were studied by comparing the experimental and theoretical values. The average aromatic ring of exinite-rich coal is three rings with approximately a quarter of substitutive degree, and the oxygen-containing functional groups in substituents are more than carbon-containing functional groups. The content of weak bonds in exinite-rich coal is 42.5 %, and with an increase in the exinite content, the alkyl side-chain and methylene bridge-chain become longer. Although the interaction between exinite and vitrinite inhibits the condensation reaction during direct liquefaction, it also occurs significantly at 455 °C, so the optimum temperature for direct liquefaction of exinite-rich coal can reach up to 440 °C. The interaction between exinite and vitrinite promotes coal conversion, reduces hydrogen consumption, and increases hydrocarbon gases, such as CH 4 and C 2 -C 3 hydrocarbons, as well as inorganic gases, such as CO and CO 2. [ABSTRACT FROM AUTHOR]

The original structural units of the coal can be deduced from the oxygen-containing macromolecules dropped in the low-temperature region during the multi-step pyrolysis of the de-ashed Shendong coal and its macerals by weak bonding, and their possible pyrolysis pathways were analyzed by DFT. [Display omitted] • The pyrolysis behavior of coal was investigated by TG, Py-GC/MS, and DFT analysis. • Low temperature pyrolysis can preserve the original O-containing structural units. • A strategy for building coal structure based on assembled O-compound. • The generated phenols energy of RD can be as low as −2167.4 kJ/mol. • Only VD (−2155.2 kJ/mol) and ID (−1670.79 kJ/mol) can generate phthalic anhydride. Most of the existing structural models of coal macromolecules are based on indirect characterization, which cannot reflect the real product structure of coal pyrolysis. This study focuses on the construction of the real structural units of de-ashed Shendong coal (RD) and its vitrinite (VD) and inertinite (ID). Two pyrolysis modes of fast pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS), Thermogravimetry (TG), Fourier transform infrared (FTIR) as well as rapid infrared heating (RIH) were used to obtain the pyrolysis properties and product composition distributions of each coal. A strategy for structural unit construction of coal, termed "Molecular Reorganization", is introduced to ensure that the original structure of the coal can be reproduced. Macromolecules produced by multi-step pyrolysis in the low-temperature region were used to assemble the real structural units of coal. The pyrolysis pathways of the oxygenated compounds in the constructed molecular unit models of RD-C 70 H 50 O 9 N, ID-C 101 H 62 O 13 N 2 , and VD-C 71 H 43 O 9 N were analyzed by density functional theory (DFT). The results showed that the reaction energy for the pyrolysis of ID fragments to phenol was higher, with fragments 1 and 2 being −4212.98 kJ/mol and −2190.83 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]

An investigation of the soils developed on ultramafic rocks in the State Line Serpentinite Belt in southeastern Pennsylvania demonstrated that the mineral assemblages are dominated by quartz, with lesser amounts of the serpentine group minerals lizardite and antigorite, and clinochlore, among other minerals. The samples have up to 39.91% MgO, 22,500 μg/g Cr, and 3300 μg/g Ni (ash basis). The light rare earth elements have a significant correlation to MgO/(MgO + SiO 2) while the distribution of Cr is random. The organic matter in the soil bears a strong similarity to lignite and subbituminous macerals. Wood-derived macerals showed variations from relatively pristine wood to degraded and attrital forms with evidence of fungal and faunal activity. Macrinite ranged from coprolitic forms to amorphous masses with little or no recognizable structure. The pollen assemblages were dominated by Pinus sp., Quercus sp., and Ribes sp. Analysis of the fungal assemblages and guild structures suggests that the Goat Hill Barrens assemblage differed from the New Texas Barrens and Nottingham Barrens assemblages and that the guild structures encountered are both similar to those encountered in peatlands while also very different, especially in the proportion of arbuscular mycorrhizal fungal remains. • Serpentine barrens in south-central Pennsylvania host endemic and invasive plants. • Minerals include quartz, lizardite, antigorite, and clinochlore. • Major elements are enriched in MgO (up to 40%; ash basis). • Minor elements are enriched in Cr (up to 17,600 ppm) and Ni (up to 3300 ppm) (both on ash basis). • Macerals in the soils resemble lignite and subbituminous forms. [ABSTRACT FROM AUTHOR]

The Claromecó foreland Basin (Carboniferous–Permian; southern Buenos Aires province, Argentina) is key to understanding the paleotectonic evolution of the southwestern Gondwana margin and is relevant to energy resource exploration. This study reconstructs the thermal and burial history of the Claromecó Basin by integrating geochemical data, organic petrology, and thermal modeling techniques. Cores samples of the Tunas Formation (Pillahuincó Group, Early Permian) were studied. A 1D thermal model was constructed, calibrated with vitrinite reflectance measurements (VRo %), and corroborated with fluid inclusion and apatite fission track data from previous studies. Rock-Eval pyrolysis results show TOC% values ranging from 0.13 to 60.35 wt%. The Hydrogen index (HI < 50 mg HC/g TOC) and Oxygen index (OI < 50 mg CO 2 /g TOC) indicate the dominance of Type III and Type IV kerogens, most likely resulting from the thermal maturation of an original Type III kerogen. Petrologic observations confirm the presence of macerals from the inertinite group, as well as minor amounts of vitrinite and liptinite. The Tmax displays a temperature range mostly from 460 to 610 °C. The VRo % values range from 1.5 to 2.0%. Geochemical data combined with VRo % measurements confirm a late catagenesis to metagenesis stage within the wet to dry gas window for coals and organic-rich strata. In order to constrain the thermal evolution of the basin infill, different scenarios were tested by varying the heat flow and the missing section thickness associated with the uplift and erosion of the basin (Permian–Cenozoic unconformity). The best calibration results were obtained with an erosion thickness of 3000 up to 4200 m and paleo heat flow peaks of either 60 or 80 mW/m2 during the Lower Permian–Lower Cretaceous. The Tunas Formation was deposited and buried during the Permian–Triassic (Gondwanides Orogeny phase), reaching a maximum temperature of 180 °C. The results obtained by combining geochemical analysis, organic petrology, and thermal modeling techniques indicate that the coal beds of the Tunas Formation could have a current potential as gas-prone source rocks. Despite that, the hydrocarbon generation capacity of coal levels is currently low due to the high percentage of residual (Type IV) kerogen. Further research could help clarify if the hydrocarbons potentially expelled by these source rocks have been lost due to migration or could be trapped somewhere in the basin. • Thermal and burial history of the Claromecó Basin were reconstructed. • 1D thermal model was built, calibrated with vitrinite reflectance measurements (VRo %). • Late catagenesis to metagenesis stage within the wet to dry gas window was defined for coal deposits. • Calibration of the thermal model was achieved considering an erosion of at least 3000 m and paleo heat flow peaks of 60 to 80 mW/m2. • A maximum paleotemperature of 180 °C was reached by the Tunas Formation during the Permian–Triassic foreland stage. [ABSTRACT FROM AUTHOR]

Industrial applications of coal rely on understanding its macromolecular structure, which is primarily controlled by coal type and rank. The present study assessed five (5) samples from different collieries extracting coal from the No. 4 Seam of the Highveld Coalfield and their float products, produced at relative densities (RD) of 1.7 and 1.9 g/cm3. The aim was to assess changes in maceral composition and coal quality following the density fractionation, and to use Raman Spectroscopy to compare differences in macromolecular structures between the parent samples and the float products. Raman parameters were also determined for specific macerals, i.e., semifusinite and collotelinite. Mean random vitrinite reflectance (%RoV) values for the studied coals range between 0.57 and 0.60% (medium rank D/C bituminous) and the parent coals are inertinite-rich (70.3 to 88.7 vol% mmf), enriched in semifusinite and inertodetrinite. Following density fractionation, reactive macerals (a combination of liptinite, vitrinite, and reactive semifusinite) are enriched in the float products (designated by "F"), specifically in the products obtained at the 1.7 RD. In comparison, the proportion of inert macerals is higher in the F1.9 samples. These differences in maceral composition are reflected in the Raman spectra and parameters. Although the G and D1 bands for the parent coals and F1.9 samples are similar, these bands are narrower than for the F1.7 samples, indicative of greater aromaticity. The G FWHM values for the F1.9 samples are comparable to those for the parent coal samples, and lower than for the F1.7 samples. This reflects larger differences in maceral composition between the parent coals and the F1.7 samples. In contrast, the D1 FWHM values for the float products, particularly the F1.7 samples, are slightly higher than the parent coals, reflecting a disordered aromatic character mainly related to the presence of aliphatic chains. The Raman spectra for the F1.7 samples are more like that for collotelinite. In contrast, the Raman spectra and parameters (G and D1 FWHM) for the F1.9 samples are more comparable to semifusinite. Thus, the increased aliphaticity for the F1.7 samples is attributed to the relative enrichment of reactive macerals, whereas higher aromaticity for the F1.9 samples reflects a larger proportion of inert macerals. Raman spectroscopy expanded on the petrographic data by interrogating the macromolecular structure of the isorank Highveld coals and their float products. This may assist in predicting the behaviour of the coals during industrial applications (i.e., liquefaction, gasification, combustion, and carbon fibre production). [Display omitted] [ABSTRACT FROM AUTHOR]

The difference between vitrinite and inertinite in coal has been regarded as the starting point, and the vitrinite and inertinite stripped from a coal sample were conducted by high-temperature (600 °C and 900 °C) and high-pressure (1.0, 1.5, and 2.0 GPa) experiments. The samples' molecular structure was examined with element analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction. The results reveal that pressure has an inhibitory effect on the evolution of molecular structure at 600 °C, and the vitrinite shows a lower molecular structure evolution degree than inertinite. For the two macerals at 900 °C, with increasing pressure, the molecular structure parameters exhibit opposite regularities to those at 600 °C, and the vitrinite shows a higher molecular structure evolution degree than inertinite. The evolution rate of molecular structures caused by pressure in vitrinite remains consistent under different temperature conditions, whereas that in inertinite exhibits jumping changes. There must be a transition interval between 600 °C and 900 °C that can change the pressure from inhibiting coalification to promoting coalification. When the temperature exceeds the transition interval, pressure can accelerate the molecular structure evolution in vitrinite, causing it to catch up with and surpass the evolution degree of inertinite's molecular structure. • High-pressure experiment has been conducted on a single maceral. • Pressure effect on vitrinite is different from that on inertinite. • Temperature restrains the pressure effects on molecular structure evolution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Non-graphitic carbon prepared from lignite-based huminite concentrate. • Optimized carbon phase distribution with increased pseudo-graphitic carbon content. • An increment of 367 S m−1 in electrical conductivity value. • Higher plateau and lower sloping capacities with better rate and cycling properties. • Remarkably improved energy density of full cell with NaFe 1/3 Ni 1/3 Mn 1/3 O 2 cathode. Herein, huminite concentrate is obtained from lignite with high yield of 68.9 % by density gradient separation, subsequently converted to non-graphitic carbon (HM-H) by carbonization at 1400 °C for 2 h. Huminite concentrate possesses relatively high oxygen content and considerable amount of aromatic component, with modest yield of volatile matter during pyrolysis, resulting in optimized carbon phase distribution and enhanced electrical conductivity of HM-H. Compared with HM prepared by direct carbonization of lignite, HM-H has slightly higher contents of pseudo-graphitic and graphite-like carbons, and lower content of highly disordered one. Notably, HM-H exhibits remarkably improved electrical conductivity (1773 S m−1) than HM (1406 S m−1). Compared with HM anode for SIBs, HM-H one delivers higher plateau capacity (170.1 mAh g−1) meanwhile lower sloping capacity (91.8 mAh g−1), with significantly improved rate and cycling performances. Full cell assorted with NaFe 1/3 Ni 1/3 Mn 1/3 O 2 cathode and HM-H anode demonstrates higher energy density of 210.5 Wh kg−1 than its counterpart (193.8 Wh kg−1) at 20 mA g−1, with superior rate performance (208.6 mAh g−1 at 200 mA g−1) and a capacity retention ratio of 89.7 % after 100 cycles. This work provides a facile and effective strategy for preparing non-graphitic carbon as high-performance anode materials for SIBs. [ABSTRACT FROM AUTHOR]