卟啉的研究现状及其应用

在前人研究资料及作者近年来的研究成果的基础上，综述了卟啉化合物地球化学研究的现状，包括金属卟啉的类型，卟啉的化学结构系列，高度脱链基卟啉和高碳数咔琳等及其它们在沉积物(如油页岩、煤和现代沉积物)中的分布特征和成因机理。指出了今后需要加强研究的领域，如沉积物中新的金属卟啉类型探讨和卟啉化学结构的确定等。文章还综述了卟啉化合物地球化学指标在地质勘探中的应用，如:评价生油岩质量，油源对比，油气运移研究，古沉积环境研究和有机质热成熟度研究等。     

Tetrapyrrole pigments in United States humic coals

Analyses of forty-two United States humic coals have revealed a striking divergence between chlorophyll diagenesis in coals when compared to the more widely studied marine sediments, shales, asphalts and petroleums. Porphyrins of humic coals have been found to be dominated by the ETIO-series, to lack members above C-32, and, in lower ranked samples (e.g. Sub-bituminous-B, high volatile C) to exhibit mass spectral envelopes with unique even-carbon number predominances. The weighted average mass, as well as the carbon number maximum (viz. mode), of these coal porphyrin homologies has been found to decrease as rank increases. The generation of porphyrins of the ETIO-series is suggested as occurring both during early coal formation, including oxidative scission of the isocyclic ring at the phorbide stage, and later during the catagenic alteration of surviving DPEP-series porphyrins. A preliminary study of chlorophyll diagenesis in a South Florida peat partially substantiates this suggestion and has further shown that the coal porphyrins can be derived from bacterial, as well as higher plant, chlorophylls.     

Iron porphyrins in the Permian Kupferschiefer of the lower Rhine Basin, N.W. Germany

Immature samples of the Permian Kupferschiefer from the Lower Rhine Basin in N.W. Germany were analysed for tetrapyrrole pigment type and abundance. The sediment, thought to have been deposited in a marine regime with enhanced salinity, was found to contain high concentrations of metalloporphyrins. The porphyrins are complexed to nickel (Ni) and oxovanadium (V=0), but high abundances of iron (Fe) porphyrins were also detected using UV/visible spectroscopy and mass spectrometry. The presence in the latter of series of aetioporphyrins, cycloalkanoporphyrins, di-cycloalkanoporphyrins and benz-cycloalkanoporphyrins was confirmed by accurate mass measurements; HPLC co-injection of deoxophylloerythroetioporphyrin (C₃₂ DPEP) with the demetallated iron porphyrins indicated its presence in the sediment as an iron complex. The study provides the first evidence for the occurrence of Fe porphyrins in geological samples other than coals and lignites, and reports the highest concentrations in sedimentary organic matter to date.     

Porphyrins in coal

The background to recent developments in investigations on coal porphyrins is reviewed. Essentially all the work of the past ten years has been with lignites and coals of the humic series. The concentrations of porphyrins and metalloporphyrins are low (0-ca. 10 μg g⁻¹), which makes for difficulties in isolation and analysis.The preferred methods of isolation and analysis are summarised. The coal porphyrins differ from the porphyrins from crude oil, oil shale and related deposits in a variety of ways which are discussed. The major differences are the predominance of the etio series over the cycloetio series (DPEP series), the presence of Fe and Ga porphyrins (rather than Ni and VO porphyrins), and the presence of mesoporphyrin IX in lignite.Recent results tend to support Treibs' original idea (1935) that, for the coal porphyrins, both chlorophyll and iron porphyrin (haem) sources are important. The application of a weighted mean molecular mass of the porphyrins present as a biological marker in determining coal rank (Porphyrin Index of Coalification) is illustrated. Current activity is directed to the isolation and identification of individual iron complexes, and here a combination of thin layer chromatography and paramagnetically shifted ¹H-NMR spectroscopy (of dicyanoferrihaems), together with direct comparison with authentic haems especially synthesised for the purpose, has been rewarding.     

Selection of coals of different maturities for CO2 Storage by modelling of CH4 and CO2 adsorption isotherms

CO₂ injection in unmineable coal seams could be one interesting option for both storage and methane recovery processes. The objective of this study is to compare and model pure gas sorption isotherms (CO₂ and CH₄) for well-characterised coals of different maturities to determine the most suitable coal for CO₂ storage. Carbon dioxide and methane adsorption on several coals have been investigated using a gravimetric adsorption method. The experiments were carried out using both CO₂ and CH₄ pure gases at 25 °C from 0.1 to 5 MPa (1 to 50 bar). The experimental results were fitted using Temkin's approach but also with the corrected Langmuir's and the corrected Tóth's equations. The two last approaches are more accurate from a thermodynamical point of view, and have the advantage of taking into account the fact that experimental data (isotherms) correspond to excess adsorption capacities. These approaches allow better quantification of the adsorbed gas. Determined CO₂ adsorption capacities are from 0.5 to 2 mmol/g of dry coal. Modelling provides also the affinity parameters of the two gases for the different coals. We have shown these parameters determined with adsorption models could be used for classification and first selection of coals for CO₂ storage. The affinity ratio ranges from a value close to 1 for immature coals to 41 for high rank coals like anthracites. This ratio allows selecting coals having high CO₂ adsorption capacities. In our case, the modelling study of a significant number of coals from various ranks shows that anthracites seem to have the highest CO₂ storage capacities. Our study provides high quality affinity parameters and values of CO₂ and CH₄ adsorption capacities on various coals for the future modelling of CO₂ injection in coal seams.     

Diversities in biomarker compositions of Carboniferous–Permian humic coals in the Ordos Basin,China

The molecular composition of Carboniferous–Permian coals in the maturity range from 0.66 to 1.63% vitrinite reflectance has been analysed using organic geochemistry to investigate the factors influencing the biomarker compositions of humic coals. The Carboniferous–Permian coal has a variable organofacies and is mainly humic-prone. There is a significant difference in the distribution of saturated and aromatic hydrocarbons in these coals, which can be divided into three types. The Group A coals have biomarker compositions typical of humic coal, characterised by high Pr/Ph ratios, a lower abundance of tricyclic terpanes with a decreasing distribution from C₁₉ tricyclic terpane to C₂₄ tricyclic terpane and a high number of terrigenous-related biomarkers, such as C₂₄ tetracyclic terpane and C₂₉ steranes. The biomarker composition of Group B coals, which were deposited in a suboxic environment, have a higher abundance of rearranged hopanes than observed in Group A coals. In contrast, in Group C coals, the Pr/Ph ratio is less than 1.0, and the sterane and terpane distributions are very different from those in groups A and B. Group C coals generally have abnormally abundant tricyclic terpanes with a normal distribution maximising at the C₂₃ peak; C₂₇ steranes predominates in the m/z 217 mass fragmentograms. The relationships between biomarker compositions, thermal maturity, Pr/Ph ratios and depositional environments, indicate that the biomarker compositions of Carboniferous–Permian coals in Ordos Basin are mainly related to their depositional environment. This leads to the conclusion that the biomarker compositions of groups A and B coals collected from Shanxi and Taiyuan formations in the northern Ordos Basin are mainly related to their marine–terrigenous transitional environment, whereas the biomarker compositions for the Group C coals from Carboniferous strata and Shanxi Formation in the eastern Ordos Basin are associated with marine incursions.     

The elemental and isotopic composition of sulfur and nitrogen in Chinese coals

Coal combustion is an important atmospheric pollution source in most Chinese cities, so systematic studies on sulfur and nitrogen in Chinese coals are needed. The sulfur contents in Chinese coals average 0.9 ± 1.0%, indicating that most Chinese coals are low in sulfur. A nearly constant mean δ³⁴S value is observed in low sulfur (TS < 1) Chinese coals of different ages (D, P₁, T₃ and J₃). High sulfur Chinese coals (OS > 0.8%), often found at late Carboniferous (C₃) and late Permian (P₂) in southern China, had two main sulfur sources (original plant sulfur and secondary sulfur). The wide variety of δ³⁴S values of Chinese coals (−15‰ to +50‰) is a result of a complex sulfur origin. The δ¹⁵N values of Chinese coals ranged from −6‰ to +4‰, showing a lack of correlation with coal ages, whereas nitrogen contents are higher in Paleozoic coals than in Mesozoic coals. This may be related to their original precursor plant species: high nitrogen pteridophytes for the Paleozoic coals and low nitrogen gymnosperms for the Mesozoic coals. Different to δ³⁴S values, Chinese coals showed higher δ¹⁵N values in marine environments than in freshwater environments.     

Contact angles in CO2-water-coal systems at elevated pressures

Injection of carbon dioxide into coal seams is considered to be a potential method for its sequestration away from the atmosphere. However, water present in coals may retard injection: especially if carbon dioxide does not wet the coal as well as water. Thus contact angles in the coal-water-CO₂ system were measured using CO₂ bubbles in water/coal systems at 40 °C and pressures up to 15 MPa using five bituminous coals. At low pressures, in this CO₂/water/coal system, receding contact angles for the coals ranged between 80° to 100°; except for one coal that had both high ash yield and low rank, with a contact angle of 115°, indicating that it was hydrophilic. With increasing pressure, the receding contact angles for the different coals decreased, indicating that they became more CO₂-wetting. The relationship between contact angle and pressure was approximately linear. For low ash or high rank coals, at high pressure the contact angle was reduced to 30-50°, indicating the coals became strongly CO₂-wetting; that is CO₂ fluids will spontaneously penetrate these wet coals. In the case of the coal that was both high ash and hydrophilic, the contact angle did not drop to 90° even at the highest pressures used. These results suggest that CO₂ will not be efficiently adsorbed by all wet coals equally well, even at high pressure. It was found that at high pressures (> 2 MPa) the rate of penetration of carbon dioxide into the coals increased rapidly with decreasing contact angle, independently of pressure. Injecting CO₂ into wet coals that have both low rank and high ash will not trap CO₂ as well as injecting it into high rank or low ash coals.     

Petrographic structure and composition of the Lower Carboniferous coal seams,western Donbas; their influence on chemical and technological properties of coals

The Lower Carboniferous coals which have been discovered and explored in the western Donbas since the war differ from those in the productive series of the old Donbas in age, petrographic composition and chemotechnological properties. From the Orel' river in the west to me Kal'mius river M the east the following have been recognized in the Lower Carboniferous: Visean coals of the sub-coal measures suite C² ₁(b), Viséan coals of the Samarsk suite C³ ₁ (c), and Namurian coals of suites C⁴ ₁ and C⁵ ₁ (d and c). The Lower Carboniferous coals over most of the western Donbas have (for a given rank) a higher yield of volatiles and primary tar, heat of combustion, sintering capacity, and hydrogen content. The rank increases to the northeast and produces a zonal disposition of coals of industrial type. The degree of coalification also increases with burial of the seams in the southwest limb of the Dneprovsk-Donets basin at depth. The basic aspect of metarnorphisrn is regional.' The petrographic structure and composition of the C³ ₁ suite coals in the western Donbas are responsible for their high chemical potential, whereby these coals are of great interest in the production of metallurgical coke. — C. E. Sears.     

Modes of occurrence of minerals in the Carboniferous coals from the Wuda Coalfield,northern China: with an emphasis on apatite formation

The mineralogical compositions of the Nos. 9 and 13 coals, which are medium-volatile bituminous coals in rank, from the Wuda Coalfield at the northwestern margin of the Ordos Basin in northern China, were investigated by optical microscopy, field emission-scanning electron microscopy in conjunction with energy-dispersive X-ray spectrometry (SEM-EDX), and X-ray powder diffraction techniques. The minerals in the Wuda coals are mainly represented by quartz, kaolinite, illite, pyrite, marcasite, apatite, dolomite, and ankerite, with trace amounts of anatase, calcite, boehmite, jarosite, gibbsite, anhydrite, and bassanite in some samples. The rod-like pyritized bacteria have been identified with SEM-EDX in Wuda coals. Moreover, the slightly reducing and alkaline environment in the original peat swamp favored bacterial action and propagation. The average concentrations of P₂O₅ in the Nos. 9 and 13 coals are 0.47 and 0.18 %, respectively. Phosphorus is not uniformly distributed within the Wuda coal seam. The maximum content of apatite in Wuda coals in certain horizon can reach up to 91.4 % (on an organic matter-free basis), corresponding to the fluorine and P₂O₅ concentrations of 2803 μg/g and 5.96 %. The high proportion of fluorine and P₂O₅ in the Wuda coals is mainly due to the authigenic apatite. The phosphorus in Wuda coals was probably derived mainly from phospho-proteins in the organic matter of the original peat deposits.     

Organic geochemical characteristics and depositional environments of the Jurassic coals in the eastern Taurus of Southern Turkey

In this study, organic matter content, type and maturity as well as some petrographic and physical characteristics of the Jurassic coals exposed in the eastern Taurus were investigated and their depositional environments were interpreted.The total organic carbon (TOC) contents of coals in the Feke–Akkaya, Kozan–Gedikli and Kozan–Kizilinc areas are 24.54, 66.78 and 49.15%, respectively. The Feke–Akkaya and Kozan–Kizilinc coals have low Hydrogen Index (HI) values while the Kozan–Gedikli coals show moderate HI values. All coal samples display very low Oxygen Index (OI) values. The Kozan–Gedikli coals contain Type II organic matter (OM), the Feke–Akkaya coals contain a mixture of type II and type III OM; and the Kozan–Kizilinc coals are composed of Type III OM. Sterane distribution was calculated as C₂₇ > C₂₉ > C₂₈ from the m/z 217 mass chromatogram for all coal samples.T_max values for the Feke–Akkaya, Kozan–Gedikli and Kozan–Kizilinc coals are 439, 412 and 427 °C. Vitrinite reflectance values (%R_o) for the Feke–Akkaya and Kozan–Kizilinc coal samples were measured as 0.65 and 0.51 and these values reveal that the Feke–Akkaya and Kozan–Kizilinc coals are at subbituminous A or high volatile C bituminous coal stage. On the basis of biomarker maturity parameters, these coals have a low maturity.The pristane/phytane (Pr/Ph) ratios for the Feke–Akkaya, Kozan–Gedikli and Kozan–Kizilinc coals are 1.53, 1.13 and 1.25, respectively. In addition, all coals show a homohopane distribution which is dominated by low carbon numbers, and C₃₅ homohopane index is very low for all coal samples. All these features may indicate that these coals were deposited in a suboxic environment.The high sterane/hopane ratios with high concentrations of steranes, low Pr/Ph ratios and C₂₅/C₂₆ tricyclic ratios > 1 may indicate that these coals formed in a swamp environment were temporarily influenced by marine conditions.     

Geochemical variations of major,trace, rare earth elements in some Gondwana and Eocene coals of India with a comparison of their germanium,lithium, and mercury content

The geochemistry of major, trace, rare earth elements (REEs), with special reference to Ge, Li, and Hg in selected Gondwana and Eocene coals, has been studied. Major oxide and trace element ratios have been utilised to compare the tectonic setting, provenance of source rocks, and paleoweathering conditions that prevailed the during formation of these coals. The Gondwana coals have a higher mean mercury and ash content (244.5 μg/kg and 17.2 %, respectively) than the Eocene coals (142.1 μg/kg, 8.9 % respectively). The major oxides, SiO₂, Fe₂O_3, and Al₂O_3, in Gondwana and Eocene coals, are enriched relative to the upper continental crust (UCC), Chinese and American coals. The UCC normalized trace element concentration coefficients of the Gondwana and Eocene coals show enrichment in Ge, Se, Th, Co, Mo, Sn, W, and Li. The mean Ge and Li concentrations (mg/kg) in Gondwana (106.7, 154.7) and Eocene (120.0, 252.6) exceed the corresponding values in world coal (2.2, and 12). The Rajmahal coals have the highest mean Ge concentration (168.8 mg/kg) among the Gondwana coals while Eocene coals from East Jaintia Hills have the highest mean value (343.7 mg/kg). The Gondwana coals have a higher mean As concentration (3.5 mg/kg) in comparison to the Eocene coals (1.9 mg/kg). The mean of the rare earth elements in Gondwana (24.1 mg/kg) is higher than that in Eocene coals (11.3 mg/kg) and these values are less than the World coals (68.5 mg/kg). Both the Gondwana and Eocene coals are enriched in light rare earth elements (LREEs). However, among the Eocene coals, the Meghalayan coals show REE enrichment in comparison to Assam coals. Both the Gondwana and Eocene coals were formed in warm and humid climates under oxic conditions with moderate weathering of the source rocks.     

Constraining the hydrocarbon expulsion history of the coals in Qinshui Basin, North China, from the analysis of fluid inclusions

From the comprehensive study on the homogenization temperatures and the occurrence of fluid inclusions in the framework minerals of the strata between or above the Carboniferous–Permian coals in the Qinshui basin, Shanxi, three stages are predicted of hydrocarbon expulsion from the coals. Combined with the known history of basin evolution, it is deduced that the expulsion of hydrocarbons happened during the J₁ (210–180 Ma), the early K₁ (150–130 Ma) and K₂E₁ (110–60 Ma). In the early stage, the coals produced and discharged coal-generated oils. The average GOI value of four sandstone samples is relatively high, as they have been exposed to high paleo-oil saturation in the strata between or above the coals. The biomarker compositions of oil-bearing fluid inclusions are similar to those of extracts from the coals, and so it is concluded that those oils were derived from the same family of the coals.     

Liquid hydrocarbon generation potential from Tertiary Nyalau Formation coals in the onshore Sarawak, Eastern Malaysia

Tertiary coals exposed in the north-central part of onshore Sarawak are evaluated, and their depositional environments are interpreted. Total organic carbon contents (TOC) of the coals range from 58.1 to 80.9 wt. % and yield hydrogen index values ranging from 282 to 510 mg HC/g TOC with low oxygen index values, consistent with Type II and mixed Type II–III kerogens. The coal samples have vitrinite reflectance values in the range of 0.47–0.67 Ro %, indicating immature to early mature (initial oil window). T _max values range from 428 to 436 °C, which are good in agreement with vitrinite reflectance data. The Tertiary coals are humic and generally dominated by vitrinite, with significant amounts of liptinite and low amounts of inertinite macerals. Good liquid hydrocarbons generation potential can be expected from the coals with rich liptinitic content (>35 %). This is supported by their high hydrogen index of up to 300 mg HC/g TOC and Py-GC (S ₂) pyrograms with n-alkane/alkene doublets extending beyond C₃₀. The Tertiary coals are characterised by dominant odd carbon numbered n-alkanes (n-C₂₃ to n-C₃₃), high Pr/Ph ratio (6–8), high T _m /T _s ratio (8–16), and predominant regular sterane C₂₉. All biomarkers parameters clearly indicate that the organic matter was derived from terrestrial inputs and the deposited under oxic condition.     

Processes controlling the composition of acid sulfate solutions evolved from coal

Leaching of a series of Appalachian coals by distilled water has been studied in laboratory reactors. From columns open to air at 25°C, leachates were produced containing typically about 0.2 M SO₄²⁻, 0.1 M total Fe and having pH < 2. Leachates contained high concentrations of toxic trace metals, including Be, Al, Cu and Cd. Concentrations of sulfate and Fe in leachates from different coals were similar and were not related to concentrations of total S in the coals. Saturation with respect to melanterite (FeSO₄·7H₂O) and a ferric oxyhydroxide phase was observed in most solutions. Leachates were undersaturated with respect to anhydrous ferric sulfate and Na-jarosite, but supersaturated with respect to K-jarosite, suggesting that none of these phases controlled solution composition. The ratio of total ferric Fe to total ferrous Fe normally exceeded unity. Accumulation of ferric Fe indicates either that its reaction with pyrite is inhibited in weathered coals, or that the coals contain pockets of oxidized pore fluid that are out of contact with pyrite. Release of Be correlated with release of Al, and release of Cu correlated with release of Fe. Reducing the temperature, lowering the partial pressure of oxygen or adding limestone retarded the release of pyrite oxidation products from the coals. Addition of limestone should be considered if it is necessary to control release of acid leachates from coal piles.     

Stable carbon isotopic fractionation of individual n-alkanes accompanying primary migration: Evidence from hydrocarbon generation–expulsion simulations of selected terrestrial source rocks

The effect of isotopic fractionation during primary migration of hydrocarbons from coals is rarely noticed because it overlaps with the isotopic effects of maturation. In this research, geological chromatography-like effects and possible physical isotopic fractionation effects on n-alkanes during primary migration from four coals and one mudstone were studied through two types of generation–expulsion simulations (generation–expulsion simulations I and II). In order to monitor the kinetic isotopic fractionation effect during primary migration and to differentiate the isotopic effects of primary migration from the isotopic effects of maturation, generation–expulsion simulation was upgraded in two aspects, source rock was separated into at least five layers, and deuterated n-C₁₅D₃₂ was added to the initial layer of the source rock (simulation II). The experimental results suggested that all terrestrial source rocks exhibit significant geological chromatography-like effects in generation–expulsion simulation. Expulsion efficiencies shown by vitrinite-rich coals are much lower than algal cannel, fusinite-rich coal and mudstone. There also exist significant physical isotopic fractionation effects in hydrocarbon primary migration processes from vitrinite-rich coals, but there is no significant isotopic fractionation effect from fusinite-rich brown coal and mudstone. Pore structure and specific surface area of source rock samples were measured by gas adsorption of both N₂ and CO₂. This indicated that vitrinite-rich coals have a higher proportion of microporosity. The differences in pore structure and adsorptive capacity of source rocks may be responsible for differences in expulsion efficiencies and isotopic fractionation effects in generation–expulsion simulations. The isotopic fractionation effect due to primary migration should be considered in making oil-source correlation when vitrinite-rich coals are concerned.     

Petrology, rank and evidence for petroleum generation, Upper Triassic to Middle Jurassic coals, Central Alborz Region, Northern Iran

Upper Triassic to Middle Jurassic coals from the Alborz region of northern Iran were analyzed by reflected light-fluorescence microscopy and Rock Eval 6® pyrolysis to evaluate their regional rank variation, degree of hydrothermal alteration, and petroleum generative potential. The coal ranks in the region range from a low of 0.69%Ro_R in the Glanddeh-Rud area to a high of 1.02%Ro_R in the Gajereh area. T_max (°C) values (Rock Eval 6 pyrolysis) also increase progressively with increasing vitrinite %Ro values, however T_max is suppressed lower than would be expected for each rank ranging from 428 °C for the Glandeeh coal to 438 °C for the Gajereh coal. T_max suppression may be caused by maceral composition and soluble organics within the coal. Moderately high hydrogen indices, persistent and oily exudations from the coals during UV exposure, and traces of hydrocarbon fluid inclusions suggest that liquid petroleum was likely generated within some of the coals.     

The occurrence of anthracites in an area characterized by lower rank coals in the Upper Silesian Coal Basin of Poland

The results of petrographical-geological and chemical examinations on anthracites, semianthracites and medium-low volatile bituminous coals from Jastrzebie in the Upper Silesian Coal Basin of Poland are presented. The coking coals mined in this region exhibit volatile matter V^daf = 18–26%, free swelling index FSI = 3–8 and reflectance R_m = 1.10–1.35% and are inertiniterich coals (I = 25–63%).Coal Seam 504 of the Anticlinal beds (Namurian B) has been affected by thermal metamorphism and contains both coking coals and coals of higher rank. According to the criterion of Polish Standards this coal seam varies from anthracite (V^daf <10%) to semianthracite (V^daf = 10–14%) in rank. The carbon content is slightly lower and the hydrogen content a little higher than those of typical anthracites and semianthracites. The reflectance values (R_m = 1.56–2.62%) are generally lower than the R_m values proposed by the International Committee for Coal Petrology as boundary values for anthracites and bituminous coal. The magnitude of anisotropy and microhardness were also examined. Examinations of optical properties prove that the metamorphism exhibited by the coals is the result of elevated temperature and variable pressure. The analyses of the maceral composition indicate that there is a decrease in the inertinite content in anthracites. Vitrinite exhibits the features of thermally altered coal. The micrinite content shows a little variation. In coking coals, a strongly fluorescing bituminous substance with the optical features of exsudatinite was found. The constructed geological section of Coal Seam 504 shows distinct regular changes in chemical and physical properties as well as the petrographic composition which may be caused by the heat flux of a magma intrusion, not localized so far.     

Role of coal type and rank on methane sorption characteristics of Bowen Basin, Australia coals

The effect of coal composition, particularly the organic fraction, upon gas sorption has been investigated for Bowen Basin and Sydney Basin, Australia coals. Maceral composition influences on gas retention and release were investigated using isorank pairs of hand-picked bright and dull coal in the rank range of high volatile bituminous (0.78% R_{o max}) to anthracite (3.01% R_{o max}). Adsorption isotherm results of dry coals indicated that Langmuir volume (V_L) for bright and dull coal types followed discrete, second-order polynomial trends with increasing rank. Bright coals had a minimum V_L at 1.72% R_{o max} and dull coals had a minimum V_L at 1.17% R_{o max}. At low rank, V_L was greater in bright coal by about 10 cm³/g, but as rank increased, the bright and dull trends converged and crossed at 1.65% R_{o max}. At ranks higher than 1.65% R_{o max}, both bright and dull coals followed similar trends. These competing trends mean that the importance of maceral composition on V_L varies according to rank. In high volatile bituminous coals, increases in vitrinite content are associated with increases in adsorption capacity. At ranks higher than medium to low volatile bituminous, changes in maceral composition may exert relatively little influence on adsorption capacity. The Langmuir pressure (P_L) showed a strong relationship of decreasing P_L with increasing rank, which was not related to coal type. It is suggested that the observed trend is related to a decrease in the heterogeneity of the pore surfaces, and subsequent increased coverage by the adsorbate, as coal rank increases. Desorption rate studies on crushed samples show that dull coals desorb more rapidly than bright coals and that desorption rate is also a function of rank. Coals of lower rank have higher effective diffusivities. Mineral matter was found to have no influence on desorption rate of these finely crushed samples. The evolution of the coal pore structure with changing rank is implicated in diffusion rate differences.     

Catagenesis of Jurassic-Cretaceous coals and rocks of the Bureya basin in the Russian Far East with respect to hydrocarbon generation

The catagenesis of the Jurassic-Cretaceous deposits and coals has been comprehensively examined based on a complex of features including the reflectance (R _o and R _a), the qualitative properties, and the petrochemical characteristics (the density and saturation porosity) of the host rocks. The catagenesis of the Jurassic-Cretaceous deposits was studied based on the structural zones in which the coal-bearing deposits occur at different depths ranging from ～ 10 to 300 m, down to 700m, and from 5 to 3460 m in the Western, Central, and Kyndal zones, accordingly. The following regularities of the changing of the coal’s catagenesis have been established: from group 3B to 1G, 2G, and GFL; from gradation PC₃ to MC₁-MC₂; and from MC₂ to MC₃-MC₄ with the changing of the composition of the coals from long-flame coal to gas and gasfat-lean coal. In the intrusive bodies distribution areas breaking through the coal-bearing deposits, the coal seams are metamorphosed to the marks of lean caking and lean coals. The data obtained have made possible the assessment of the hydrocarbon generation in the Jurassic-Lower Cretaceous deposits of the basin.