Lasers in organic petrology and organic geochemistry, II. In-situ laser micropyrolysis-GCMS of coal macerals

The development and preliminary results of a novel laser micropyrolysis-gas chromatography, mass spectrometry (LMPy-GCMS) system are described. Short exposures of near-infra red (IR) laser radiation focused through a microscope's optics onto a specific, targeted maceral within a polymaceralic organic-rich shale or coal are used to release the thermal evaporation and pyrolysis products from the maceral. The products from multiple exposures on a single maceral type are collectively analyzed online using GCMS. This technique is intended to provide a means of chemically characterizing individual, microscopic organic entities (> 25 μm) in coals and shales without the need to physically separate them from each other (e.g. density gradient centrifugation) or from their mineral matrix (e.g. bulk analysis of kerogen concentrates). Molecular characterization of individual macerals is important in predicting the technological properties of coal and the petroleum generation potential of petroleum source rocks.Different macerals respond differently when exposed to focused near-IR laser radiation due to differences in their heat capacity and heat conduction. The thermal products released during irradiation of macerals (ulminite, alginite, sporinite and fusinite) representing the huminite, liptinite and inertinite maceral groups are presented. Under the appropriate heating, collecting, and trapping conditions, the thermal products liberated are considered representative of the macromolecular structure of the macerals. Structural elucidation of macerals in coals and shales could significantly benefit from concerted efforts of this and other in-situ micro-analytical techniques.     

不同沉积环境成因煤显微组分的有机硫分布

运用扫描电镜能谱微区测试对不同沉积环境成因煤的有机显微组分进行有机硫含量的系统测定，结果表明在不同类型的煤中某一类显微组分的有机硫含量存在明显差异；同一煤中不同亚显微组分的有机硫含量也不同。综合分析发现煤显微组分有机硫含量主要受聚煤环境、组分凝胶化程度、氧化程度的影响，而聚煤环境为主导影响因素。     

鄂尔多斯盆地延安组煤有机岩石学研究

鄂尔多斯盆地侏罗纪延安组煤系地层可否成为该盆地另一套油源岩的问题,历来存有争议。系统的煤岩和有机岩石学分析表明:煤中倾油性的壳质组分含量低,基质镜质体的类型也不利于生油,因此,延安组煤系有机质不大可能形成具有工业价值的煤成油藏     

Effect of maceral subtypes and mineral matrix on measured reflectance of subbituminous coals and dispersed organic matter

The variability in reflectance of huminite (texto-ulminite, eu-ulminite A and B, different types of corpohuminite) and liptinite groups of macerals in subbituminous coals was examined using reflected light microscopy. All macerals were selected from coal and interbedded carbonaceous shale and carbonate sediment samples from the 515-m-thick coal deposit No. 2 located in the Hat Creek valley of south-central British Columbia. The measurements obtained reveal that, in addition to burial depth, reflectance distribution depends on maceral subtypes and associated mineral matrix.Huminite in the coals and sediments (kerogen) consists mainly of humotelinite, with eu-ulminite B being the dominant maceral sub-type. Reflectance values determined on huminite in coals and Type IIIb kerogen increase from eu-ulminite A and phlobaphinite type 1 through eu-ulminite B and phlobaphinite type 2 to gelinite. The reflectance of all five huminite maceral subtypes studied increases with depth. However, the increase of phlobaphinite type 1 and gelinite reflectance with depth is irregular.A comparison of the reflectance values obtained for the same maceral subtype (eu-ulminite B) from the interbedded coal, shale and carbonate samples records consistent differences, implying some dependence of the reflectance (and perhaps rate of organic maturation) on the mineral matrix. Generally, the highest eu-ulminite B reflectance was recorded from carbonate rocks and the lowest from shale, whereas coal matrix produced intermediate values.At present, it is not known whether differences in reflectance of eu-ulminite found in the above lithologies are due to differential retention, efficiency of reaction products removal, thermal conductivity of the lithologies, or existence of a calcium carbonate catalyst.     

Predicted CO2 emissions from maceral concentrates of high volatile bituminous Kentucky and Illinois coals

A large collection of well-characterized coals, documented in the Center for Applied Energy Research's (CAER) database, was used to estimate the CO₂ content of maceral concentrates from Kentucky and Illinois high volatile bituminous coals. The data showed no correlation between CO₂ versus coal ranks and between CO₂ versus maceral content. Subsequently, eight sets of low-ash density-gradient centrifugation (DGC) maceral concentrates from five coal beds were examined, spanning in the high volatile rank range. Heating value was not determined on the concentrates, but instead was calculated using the Mott–Spooner formula. There was a good correlation between predicted CO₂ and maceral content for the individual iso-rank (based on vitrinite reflectance, analyzed on whole (parent) coal) sets. In general, the predicted CO₂ increases from liptinite-rich through vitrinite-rich to inertinite-rich concentrates (note: no “concentrates” are absolutely monomaceral).     

The petrology of greek brown coals

Results are given in the petrography of Greek coals collected from most of the major coal-bearing basins in Greece.Rank was determined by measuring reflectances on the maceral varieties eu-ulminite A and eu-ulminite B and on the maceral textinite. Reflectances obtained from these components indicate a coalification stage of brown coal for all samples. Within this group of samples there is, however, a fairly wide scatter of reflectance values indicating for some of them the transition zone from peat to brown coal and for others a coalification stage close to the transition into bituminous coals. Reflectances obtained from eu-ulminite A and eu-ulminite B were found to correlate well with chemical rank parameters such as volatile matter and calorific value.Composition was determined by maceral analysis. The coals are in general characterized by low amounts of macerals of the inertinite group, low to intermediate amounts of macerals of the liptinite group and high amounts of macerals of the huminite group. Within the latter group densinite, attrinite, eu-ulminite and textinite make up the bulk of the samples.Typical macerals observed in the coals are illustrated by two black and white and three colour plates.Cluster analysis based on maceral distribution, mineral matter and reflectance indicates that the samples studied can be divided into three major groups. The first one is dominated by eu-ulminite and densinite with relatively high reflectances. The second is dominated by attrinite, textinite and texto-ulminite with somewhat lower reflectances. The third is represented by a single sample in which textinite and resinite are the most abundant macerals. This sample also has the lowest reflectance.     

Study of petrological characteristics of coal deposits from Marki-Jhari-Jamni area,Wardha valley coalfield,Maharashtra

A detailed study of maceral composition and vitrinite reflectance of the coal deposits from Marki-Jhari-Jamni area, situated in the northwestern extremity of Wardha valley coalfield, Yeotmal district, Maharashtra has been carried out with special reference to their depositional set up. These coals have two distinct types of maceral organization, one having significantly high distribution of the vitrinite group of macerals (35–41%) and the other containing the dominance of inertinite (26–49%). Liptinite maceral group is recorded between 14 and 24%, barring a few coal bands having liptinite maceral group as high as 33–37%. The vitrinite reflectivity ranges from 0.38–0.43%. Thus, they have attained sub-bituminous C rank. Mineral matter in these coals varies between 15 and 22%. The present study suggests that the basin primarily experienced cold climate having intermittent brackish water influx with alternating dry oxidizing spells.     

Study of petrological characteristics of coal deposits from Marki-Jhari-Jamni area, Wardha valley coalfield, Maharashtra

A detailed study of maceral composition and vitrinite reflectance of the coal deposits from Marki-Jhari-Jamni area, situated in the northwestern extremity of Wardha valley coalfield, Yeotmal district, Maharashtra has been carried out with special reference to their depositional set up. These coals have two distinct types of maceral organization, one having significantly high distribution of the vitrinite group of macerals (35–41%) and the other containing the dominance of inertinite (26–49%). Liptinite maceral group is recorded between 14 and 24%, barring a few coal bands having liptinite maceral group as high as 33–37%. The vitrinite reflectivity ranges from 0.38–0.43%. Thus, they have attained sub-bituminous C rank. Mineral matter in these coals varies between 15 and 22%. The present study suggests that the basin primarily experienced cold climate having intermittent brackish water influx with alternating dry oxidizing spells.     

Carbon-13 NMR spectra of macerals separated from individual coals

The density gradient centrifugation technique has recently been applied to the separation of macerals from whole coals. Sufficient quantities have been separated to permit examination of pure exinite, vitrinite and inertinite fractions by combined cross polarization and magic angle sample spinning (CP/MASS) carbon-13 NMR techniques. The similarities and differences observed in the maceral groups of two coals are discussed. Diversity in precursors or in differential chemical maturation or a combination of both of these factors can be used to account for subtle spectral differences in the two coals and macerals studied even though the gross spectral features are very similar for a given maceral type. The data show that CP/MASS is a technique that can address such interesting geochemical questions.     

霍林河褐煤显微组分加氢液化性状的研究

对宏观煤岩类型和显微组分组成各不相同的5个褐煤煤样,进行了加氢液化和活化两组试验,通过对其转化率差别的分析,以及将活化后的残渣在普通显微镜、荧光显微镜和扫描电镜下的观察,了解了不同显微组分组和腐植组中的不同显微组分/亚组分/种的加氢液化特性和差别。这种差异表明显微组分组成不同的褐煤在加氢液化时的转化率不同,同时也显示了显微组分基本由腐植组组成的煤样转化率有差异。      

Facies control on the petrographic composition of inertitic coals

The petrography of lignitic, subbituminous and bituminous inertinitic coals (i.e. coals containing > 30 modal percent inertinite on a mineral-matter-free basis) derived from limnic and paralic facies in the Upper Silesian coal basin of Poland was investigated. Paralic coals were observed to contain small amounts of telinite and abundant pyrofusinite compared to limnic coals. The ratio of oxysemifusinite and oxyfusinite to pyrosemifusinite and pyrofusinite is lower in paralic coals as compared to limnic coals. The statistical analysis of the reflectances of the inertinite group macerals and of vitrinite shows that paralic coals are more heterogeneous than limnic coals. This greater degree of heterogeneity may explain the differences in reactivity among coals that otherwise have the same rank and elemental and petrographic composition.     

从各向异性壳质组的发现论壳质组在煤化过程中的光性演变

通过对我国几个典型煤田300多块煤光片的详细煤岩研究,发现煤中存在一种高反射具强烈各向异性的有机显微组分,有些保存了完好的壳质组外形和结构.可称之为各向异性壳质组,它广泛分布于长焰煤以上各煤级煤中,它的发现进一步说明了壳质组的煤化历程是复杂的。有些在煤化过程中几乎全部裂解为烃类而消失,绝大多数光性与共生镜质组同化,还有一少部分转变成了各向异性壳质组。     

Petrographical and thermo-chemical investigation of some North East Indian high sulphur coals

The Tertiary North East Indian coals, classified as sub-bituminous rank, have found less industrial application owing to their physico-chemical attributes. These coals are characterized by low ash (<15%), high volatile matter (>35%) and high sulphur (2.9-4.46%). Majority of the sulphur occurs in organic form affixed to the coal matrix owing to marine influence, is difficult to remove. The coal maceral analysis shows the dominance of vitrinite (>75%) with lesser amounts of liptinite and inertinite. Reflectance measurements (Rmax) of these sub-bituminous coals fall in the range of 0.57 to 0.65. In this study, the petrographical (maceral), thermal and other physico-chemical analyses of some low rank Tertiary sub-bituminous coals from north-east India were carried out to assess their potential for combustion, liquefaction and coal bed methane formation. The petrofactor, conversion (%) and oil yield (%), combustion efficiency of the coal samples were determined. The respective linear correlations of conversion (%) of the coals with their vitrinite contents, petrofactor and oil yield values have been discussed. The relative combustion efficiency of the coals was measured from the thermo gravimetric analysis (TGA) of coals. The influence of maceral composition upon gas adsorption characteristics of these high volatile coals showed the increase in methane adsorption with vitrinite enrichment. Both the maceral and mineral matter contents were observed to have important influence on the gas adsorption characteristics.     

Comparison of elemental composition of macerals determined by electron microprobe to whole-coal ultimate analysis data

The elemental composition of the individual macerals in a suite of Australian coals has been determined in polished sections using light-element electron microprobe techniques. The analyses of the individual macerals in each coal were combined with data on maceral abundance to produce an inferred chemical composition for the organic matter of the respective whole-coal samples, and this was compared, for each sample, to the respective whole-coal ultimate analysis data, corrected to a dry, ash-free (daf) basis. Except for slightly lower values in some lower-rank coals, the inferred percentages of whole-coal C estimated from the microprobe data were found to be very close to the respective whole-coal C percentages as determined by conventional ultimate analysis. The proportion of O in the coals indicated by the microprobe study, however, appears to be as much as 2% higher than that derived from the ultimate analysis data, especially in the lower-rank coal samples. The difference it may represent errors in calculating the O percentages in ultimate analysis, errors in the microprobe analysis due to difficulties in calibration or measurement, or increased proportions of O in the coals due to factors such as take-up with storage of the polished sections. The percentages of whole-coal N calculated from the microprobe data are up to 0.5% (absolute) below the proportion of N determined directly by whole-coal ultimate analysis. This may reflect the inherent difficulty of dealing with a light element at low concentrations by the microprobe technique, or it may indicate that some of the N occurs in the coals in mineral form. The percentages of whole-coal (organic) S calculated from the microprobe study are close to the percentages of organic S determined for each sample by more conventional techniques. With the exception of (organic) O, which may be affected by other factors, and also possibly of N, the electron microprobe technique appears from the study to provide results that are consistent with ultimate analysis over a wide rank range.     

中国西北侏罗纪煤系显微组分热解油生物标志物特征及其意义

从西北地区侏罗纪煤中分离出来的不同显微组分热解油生物标志物总体上比较相似,但在一些特殊生物标志物的分布上存在明显差异。藻类体、孢子体、角质体热解油Pr/Ph比值一般在1.5～2.0之间,镜质体和基质镜质体热解油Pr/Ph比值在3～4之间,但均只有相应原煤抽提物Pr/Ph比值的一半。在常规生物标志物甾烷和萜烷组成中,藻类体和孢子体含有相对丰富的C27甾烷,角质体其次,镜质体和基质镜质体C27甾烷含量很低或者基本不含C27甾烷;藻类体和角质体含有较高的伽马蜡烷,而与藻类体来自相同原煤的孢子体伽马蜡烷含量很低;镜质体和基质镜质体基本上不含伽马蜡烷;分离显微组分的原煤伽马蜡烷含量均很低。由此可见,伽马蜡烷的含量不仅与有机质沉积水体的盐度有关,与母源的成分也有关系。显微组分热解油与煤系原油生物标志物组成特征对比表明,煤系原油是藻类体、孢子体、角质体等富氢组分和相对贫氢的镜质组生成产物的混合物。不同油气藏中的原油,每一类显微组分的贡献可能不尽相同,有些原油可能主要来源于藻类体和孢子体等富氢显微组分,而有些原油除了富氢显微组分有贡献外,镜质组对其也有一定的贡献,但富氢显微组分应该是煤系含油气盆地中主要的生油显微组分。     

乌达矿区煤中显微组分有机硫的赋存分布

应用带能谱的扫描电镜微区测试对乌达矿区煤中不向显微组分的有机硫进行了系统测定，结果表明在不同的显微组分中其有机硫的含量有明显的差异，向一煤样中不同的亚组分中其有机硫的含量不相同，并且同一煤样同一显微亚组分其有机硫的含量亦有不同程度的差异。综合分析发现煤显微组分有机硫含量主要受煤的聚积环境、凝胶化程度、氧化程度等因素的影响。     

PHYSICAL AND CHEMICAL PROPERTIES OF BITUMINOUS COAL CONSTITUENTS (MACERALS)

Investigation of bituminous-coal macerals, accomplished through the Institut für Brennstoff Chemie (Fuel Chemistry Institute) of Aachen, is summarized here. Coal from five Ruhr coal beds was processed to obtain pure macerals in quantities sufficient to study their individual structure and chemical composition. Vitrinite, micrinite and exinite were recovered accordingly, and their chemical and physical properties studied; detailed, graphical interpretation of these data has been included. Chemical composition is derived for vitrinite, exinite, micrinite, and fusinite individually. Chemical structure of the macerals is discussed in relation to aromatically bound carbon content. It has been possible thus far, to determine maceral properties with respect to coalification rank as well as to indicate differentiation of these properties in macerals from the same coal bed. --D. D. Fisher.     

Changes of semifusinite and fusinite surface roughness during heat treatment determined by atomic force microscopy

This study describes changes of surface roughness of semifusinite and fusinite as an indicator of structural alteration resulting from heat treatment at 400–1200 °C. Surface roughness has been investigated by atomic force microscopy of inertinite concentrates from coking coals (vitrinite reflectance R_r = 1.07%–1.41%) from the Upper Silesian Coal Basin of Poland (Namurian C — Westphalian A). Unheated fusinite has a higher surface roughness than semifusinite from the same coal. The average surface roughness of semifusinite decreases with the Swelling Index of the parent coal. Heating increases the surface roughness of semifusinite and fusinite. Increase in the average surface roughness is stronger for semifusinite than fusinite and correlates to increasing reflectance of these macerals. The surface roughness of semifusinite correlates to the relative mass loss of the inertinite concentrates during heating. After heating to 1200 °C fusinite has a lower average surface roughness than semifusinite from the same coal. Consequently, average surface roughness can be used as a measure of structural alteration of inertinite group macerals during heat treatment.     

黄陇煤田煤中显微组分与孢粉类型的相关趋势

对陕西黄陇煤田中下侏罗世延安组４号煤进行了煤岩学和孢粉学的详细定量分析，并用计算机对显微组分与孢粉类型之间的的关系作了相关分析，结果表明，煤中显微组分与孢粉类型之间在在相关关采、这种相关关系反映了显微组分的形成与成煤植物之间存在着成因上的联系，即煤中基质状和碎屑状显微组分主要由草本植物和材蕨植物形成，而其细胞结构和条带状的显微组分主要由木本裸子植物形成，，这两种类型显微组分的比值可以反映成煤植被特征。     

Some chemical structural features of coals of differing maceral distributions and stratigraphy

Six North American bituminous coals (four Carboniferous and two Cretaceous) and eight maceral concentrates from Carboniferous British seams have been heated with tetralin and hydrogen to 400°C. The hexane-soluble parts of the products were separated by column chromatography and the fractions were then analyzed by gas chromatography/mass spectrometry. In all cases the aromatic hydrocarbon fraction was a very complex mixture containing a number of alkylated biphenyls, diphenylmethanes and -ethanes, and polycyclic compounds. However single ioncchromatography (m/z = 142) showed that, in addition to these, the products from five of the six American coals contained homologous series of long chain n-alkylnapththalenes with alkyl groups extending to C₁₆. In other fractions from the American coals, homologous series of n-alkylfurans and alkylphenols were found to be major components, as also were many alkylcyclohexenones related to isophorone. Extensive homologous series of n-alkyl aromatics were not detected in products from any of six vitrinites from British seams, though series of n- and iso-alkylphenols were found in the products from two sporinite concentrates. A number of polycyclic ketones apparently related to sterols were found in the products from the British vitrinites but not from any American coals. Reasons for what appear to be systematic structural differences between the American and British coals are discussed. Differences in stratigraphy are noted and it seems not impossible that differences in source vegetation are significant.