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1.
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.  相似文献   

2.
Iron porphyrins have been isolated from seven U.S. humic coals of various geological ages. Mass spectrometry shows that for the higher rank coals the porphyrins comprise an homologous series of alkyl derivatives (C27-C32). Mesoheme is detected in a Cretaceous lignite from Montana.  相似文献   

3.
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.  相似文献   

4.
The natural thermal evolution of type III coals (Humic origin) is expressed during diagenesis by a loss of oxygen as CO2 and H2O. Other phenomena such as oxidation can cause extensive geochemical modifications and may complicate the effects of simple maturation.Humic coals from the Jurassic in southeastern Utah were studied by elemental analysis, Rock-Eval pyrolysis and infrared spectroscopy. In a van Krevelen diagram (atomic H/C vs atomic O/C), the samples fall within the envelope defined by 860 reference humic coals covering the entire range of diagenesis. Nevertheless, various criteria (geochemical, petrographic, geological and microscopic) cast doubt upon the interpretation that such a distribution of coal composition results from thermal maturation.The same criteria indicate the intervention of redox phenomena. Comparison of our results with those from artificial and natural oxidation shows that these coals were subjected to an oxidation process different from ordinary late alteration. This process was probably due to circulation of highly oxidizing saline water causing oxygen fixation and the transformation of carboxyls into carboxylate anions. The cations that were fixed are oxygenated and certainly contain calcium, but also uranium and perhaps several other cations (V, Mo, Fe...). Emphasis is placed on possible mechanisms that cause such phenomena.  相似文献   

5.
The structural evolution of coals during coalification from peat to the end of the high volatile bituminous coal rank (VRr = 0.22–0.81%) has been studied using a natural maturity series from New Zealand. Samples were studied using a range of standard coal analyses, Rock–Eval analysis, infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and pyrolysis gas chromatography (Py-GC). The structural evolution of coal during diagenesis and moderate catagenesis is dominated by defunctionalisation reactions leading to the release of significant amounts of oxygen and thereby to an enrichment of aromatic as well as aliphatic structures within the residual organic matter. Based on the evolution of pyrolysis yields and elemental compositions with maturity it can be demonstrated that oxygen loss is the major cause for increasing Hydrogen Index values or hydrocarbon generating potentials of coals at such maturity levels. For the first time, the loss of oxygen in form of CO2 has been quantified. During maturation from peat to high volatile bituminous coal ranks ∼10–105 mg CO2/g TOC has been released. This is equivalent to 2.50E−4 to 1.25E−3 mg CO2 generated from every litre of sediment per year falling into the range of deep biosphere utilisation rates. Immature coals, here New Zealand coals, therefore manifest the potential to feed deep terrestrial microbial life, in contrast to more mature coals (VRr > ∼0.81%) for which defunctionalisation processes become less important.  相似文献   

6.
Three Australian brown coals have been separated into humin and humic acid fractions and studied by high resolution solid state 13C NMR spectroscopy and Fourier transform IR spectroscopy. The aromatic rings of the humic acids are highly substituted showing that extensive cross linking must have occurred during formation from wood lignin and tannin. However, the humins contain more aliphatic carbon and hydrogen than the corresponding humic acids. This shows that little cross linking has occurred with other components of the brown coal such as resins, waxes cutin and algal detritus, and cross linking has not rendered the aromatics alkali insoluble. The kinetics of extraction are complex and not simple first order. This is reflected in the chemical composition of the humic acid which is extraction temperature dependent. We also observed that there is a conversion of aromatic carbon to aliphatic carbon and gas during extraction, probably by alkaline oxidation, resulting in ring opening. A range of suitable model compounds have been studied to confirm this finding. Such a mechanism may account for the modification of lignin in oxidising environments such as those occurring in the initial stages of coalification (lignite or brown coal formation) and in soils.  相似文献   

7.
To determine the I distribution in Chinese coals, a nationwide survey was undertaken based on the distribution, periods of formation, rank and production yields of various coal deposits. A total of 305 coal samples were collected and their I contents were determined by catalytic spectrophotometry with pyrohydrolysis. The geochemistry of I during coalification (including both peat diagenesis and coal metamorphism) was assessed. It was found that the I contents of Chinese coals range from 0.04 mg kg–1 to 39.5 mg kg–1 and exhibit a lognormal distribution, with a geometric mean of 1.27 mg kg–1. Statistical correlation analysis and the observation that I contents increase with coal rank indicate that coal I is chalcophile in nature, and not generally organically bound. When peat developed into lignite through diagenesis, 95–99.9% of the original I was lost. The composition and structure of clay minerals present in the coal were controlled by the original depositional environment. The higher the I content of coals, the more likely the original sediments were affected by a marine environment. Iodine contents increased from lignite through sub-bituminous and bituminous coals to anthracite. This indicates that coal absorbed excess I from hydrothermal fluids during metamorphism (including geothermal metamorphism and telemagmatic metamorphism). The telemagmatic metamorphism was caused by magmatic activities that depended on the specific geological structure of the region. In China, most high-rank coals were formed by telemagmatic metamorphism.  相似文献   

8.
The soluble organic material present in a set of 12 coal samples representing three major episodes of coal deposition in Shanxi Province, North China, has been examined. Shanxi coals, like those from Gondwanaland, contain little liptinite and accordingly the material extracted by pyridine yields only small quantities of n-hexane soluble n-alkanes, steranes and hopanes identifiable by gas-chromatography/mass spectrometry. The distribution of the n-alkanes is characteristic of the environment from which each of the Shanxi coals was formed but the distribution of the branched alkanes is generally determined by the dia- and catagenesis each coal experienced. Aromatic compounds identified in the extracts typify the small molecules present within the vitrinite lattice. Technologically significant benzene-methanol extracts deriving from vitrinite-inertinite have been characterised by proton NMR spectroscopy and partially separated by HPLC.  相似文献   

9.
Elemental composition was used to calculate the amounts of compounds produced during the diagenetic evolution of a coal series from the Mahakam delta (Kalimantan, Indonesia). These calculations were based on the following hypotheses: organic nitrogen does not take part in reactions and remains unchanged in the residual organic matter, the only compounds produced are water, carbon dioxide and hydrocarbons.This approach shows that carbon loss during diagenesis is mainly as CO2, and hydrogen loss is mainly as H2O. Hydrocarbon production is negligible, in accordance with absence of bacterial methane accumulations in the Mahakam delta.The δ13C of coals in the sequence becomes about 2 per mil more positive over the diagenetic depth range of coal evolution. Accounting for the coal δ13C change in terms of CO2 loss requires that the CO2 given off have δ13C of about ?40%.. Such negative CO2 has not been observed in natural systems, except when CH4 is undergoing oxidation. Several plausible causes for this effect are discussed.  相似文献   

10.
This paper presents reviews of studies on properties of coal pertinent to carbon dioxide (CO2) sequestration in coal with specific reference to Victorian brown coals. The coal basins in Victoria, Australia have been identified as one of the largest brown coal resources in the world and so far few studies have been conducted on CO2 sequestration in this particular type of coals. The feasibility of CO2 sequestration depends on three main factors: (1) coal mass properties (chemical, physical and microscopic properties), (2) seam permeability, and (3) gas sorption properties of the coal. Firstly, the coal mass properties of Victorian brown coal are presented, and then the general variations of the coal mass properties with rank, for all types of coal, are discussed. Subsequently, coal gas permeability and gas sorption are considered, and the physical factors which affect them are examined. In addition, existing models for coal gas permeability and gas sorption in coal are reviewed and the possibilities of further development of these models are discussed. According to the previous studies, coal mass properties and permeability and gas sorption characteristics of coals are different for different ranks: lignite to medium volatile bituminous coals and medium volatile bituminous to anthracite coals. This is important for the development of mathematical models for gas permeability and sorption behavior. Furthermore, the models have to take into account volume effect which can be significant under high pressure and temperature conditions. Also, the viscosity and density of supercritical CO2 close to the critical point can undergo large and rapid changes. To date, few studies have been conducted on CO2 sequestration in Victorian brown coal, and for all types of coal, very few studies have been conducted on CO2 sequestration under high pressure and temperature conditions.  相似文献   

11.
Cyclic terpenoids present in the solvent extractable material of fossil woods, ambers and brown coals have been analyzed. The sample series chosen consisted of wood remains preserved in Holocene to Jurassic sediments and a set of of ambers from the Philippines (copalite), Israel, Canada and Dominican Republic. The brown coals selected were from the Fortuna Garsdorf Mine and Miocene formations on Fiji.The fossil wood extracts contained dominant diterpenoid or sesquiterpenoid skeletons, and aromatized species were present at high concentrations, with a major amount of two-ring aromatic compounds. Tricyclic diterpenoids were the predominant compounds in the ambers. Aromatized derivatives were the major components, consisting of one or two aromatic ring species with the abietane and occasionally pimarane skeletons. The saturated structures were comprised primarily of the abietane and pimarane skeletons having from three to five carbon (C1, C2, etc.) substituents. Kaurane and phyllocladane isomers were present in only minor amounts. Bicyclic sesquiterpenoids as saturated and partial or fully aromatized forms were also common in these samples, but only traces of sesterterpenoids and triterpenoid derivatives were found.The brown coal extracts were composed of major amounts of one- and two-ring aromatized terpenoids, with a greater proportion of triterpenoid derivatives than in the case of the woods and ambers. This was especially noticeable for the German coal, where the triterpenoids were predominant. Open C-ring aromatized structures were also present in this coal. Steroid compounds were not detectable, but some hopanes were found as minor components in the German brown coal.An overview of the skeletal structure classes identified in each sample, as well as the general mass spectrometric characteristics of the unknown compounds are included in the present paper. It can be concluded from these structural distributions that aromatization is the main process for the transformation of terrestrial cyclic terpenoids during diagenesis, constituting a general pathway for all terpenoids.  相似文献   

12.
This report extends our previous studies by investigating oxic and anoxic alteration of chlorophyll in 13 species of microalgae incubated between 3 and 10 years. The experiments were designed to investigate the alteration of chlorophyll as cells senescence, die and decompose. They mimic the initiation of diagenesis without the intervention of (non-microbial) grazing or photochemistry.Anoxic (dark) incubation provided two new observations and substantiated numerous other chlorophyll-a (CHLa) alteration reactions: (i) vinyl reduction, giving meso-CHLa and several derivatives, occurred, adding to observations on the phorbide/deoxophylloerythroetioporphyrin (DPEP) routes; (ii) room temperature anoxic incubation of a diatom (Navicula sp.) for 5.5 years resulted in production of purpurporphyrin-18 free acid (PurPorph-18-FA), a functionalized porphyrin and direct precursor of a specific C-30 β-H etioporphyrin. Oxic conditions typically led to high amounts of the allomers of CHLa, pheophorbide-a, and pheophytin-a, as well as to the appearance of purpurin-18 (PUR18) and/or its phytyl ester (PE). Mg-PUR18-PE, chlorin-p6-PE (the hydrolysis product of PUR18-PE) and two forms of chlorin-e6 (PE and free acid) were also often present.Such experiments have proved quite valuable for investigation of senescence/death induced alteration of the chlorophylls. In this manner, the processes can be better understood, vs. reactions occurring during grazing (heterotrophy) and early diagenesis in sediments. Various routes to specific ETIO series porphyrins from the chlorophyll-a nucleus are suggested on the basis of these data.  相似文献   

13.
The Mahakam delta (Kalimantan, Indonesia) coals represent all the evolution stages between freshly-deposited plant/peat material, lignites and bituminous coals. The geochemical techniques used to study this coal series included elemental analysis, extraction of humic compounds, infrared spectroscopy and 13C nuclear magnetic resonance of the total coal.The main mechanisms of early maturation in this series are loss of oxygenated compounds, aromatisation and condensation of the organic matter. These changes, which have already been suggested for other coal series and partially reported for sedimentary organic matter, were confirmed and described in more detail for the Mahakam coal series.  相似文献   

14.
It has been proposed that Victorian brown coal can be considered as a two-component structure — a lignocellulosic “host”, containing various amounts of weakly bound or entrapped “guest” material together with very small amounts of inorganic and/or mineral matter. The latter predominantly consists of wax esters and/or terpenoid material. In this paper we describe attempts to gain structural information regarding the more complex, “host” component of the coal. Our initial model compound has been humic acid that can be readily obtained from the coal by alkaline extraction. It has been found that “pure” humic acid, free from material associated with the “guest” components of the coal, can be obtained by a highly selective, low-yielding alkaline extraction. This humic acid has been studied by nmr spectroscopy and pyrolysis gas chromatography-mass spectroscopy (py-gc/ms). The products arising from py-gc/ms have been compared with those obtained from similar pyrolysis of whole coals. Alkylation of humic acids using alkyl halides in the presence of base has been successfully carried out and reactivity of the resulting materials compared with those of the parent coal and humic acid.  相似文献   

15.
A quantitative 13C-NMR technique was applied to humic acids, isolated from total solvent extracts obtained from coals, varying in rank from lignite to medium volatile bituminous. The results from elemental analysis and 13C-NMR structural ratios are interpreted in the form of three distinct structural phases in the maturation of coal humic acids. These phases reflect the rank of the parent coals. A decrease in polar functional group content and corresponding increase in aromaticity is observed with increasing maturation of humic acid chemical structure. Limits are postulated for the oxygen content and level of aromaticity for humic acids derived from higher rank coals.  相似文献   

16.
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.  相似文献   

17.
卟啉的研究现状及其应用   总被引：2，自引：0，他引：2  
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。  相似文献   

18.
A suite of samples from the Funan Mine, N.E. China, has allowed a comparison to be made between hydrocarbon-rich coals and coaly shales. These are immature coals and the known geological history suggests that they have experienced only a mild geothermal history. Analyses of the di- and sesquiterpenoid components show that compounds based on the kaurane skeleton are absent unlike Australian brown coals; and the diterpenes isopimarane, pimarane and 16α (H)-phyllocladane relate to a different community of higher plants such as Pinaceae and Taxodiaceae from those recognized in Australian brown coals. A consideration of geochimical parameters and biomarker composition leads to the conclusion that the geolipid concentrations in the sample suite are environmentally determined. It is concluded, therefore, that 22R-17β (H),21β (H)-bishomohopanoic acid and the 22R-17α (H),21β (H)-homohopane, both predominant components in their respective classes, are derived from different sources. Labdanic acids have been identified in these coals. They are likely to be derived from resin constituents of the coal and not from microbial biomass. They could potentially be developed as a maturation parameter. Cis and trans isomers of a triaromatic hydrocarbon based on the oleanane skeleton which has been previously identified in Victorian brown coal are present in the Funan coals. The more oxidizing the environment the less advanced is the isomerization of cis to trans and again the environment of deposition is the controlling factor. This study emphasizes the importance of understanding pathways of early diagenesis for the interpretation of data derived from more mature samples.  相似文献   

19.
Elevated polycyclic aromatic hydrocarbon (PAH) concentrations were determined in different Chinese coals, with the highest concentrations in bituminous coals. Phenanthrene (Phen) was chosen as the probe compound for PAHs to study the sorption behavior of coal. No native Phen was detected in desorption experiments indicating irreversible sorption–desorption behavior of PAHs in raw coal samples. Sorption mechanism was further studied under varying conditions of pH value and ionic strength. Different ranks of coal showed different sorption behavior under acidic, neutral, and alkaline conditions. Batch experiments were further processed for the selected coals at pH values from 3 to 11 at a constant aqueous concentration. Sorption capacities of all coals decreased with increased pH except for YJ coal. Furthermore, although DOC-associated Phen mass contributed little to the total Phen mass under different pH values, the significant negative correlations between M DOC and log K OC values were observed for all coal samples, indicating a significant role played by DOC in the coal sorption. In addition, sorption experiments under varying ionic strength showed that the ionic strength influence was more obvious in sorption isotherms for higher rank coals with increasing ionic strength, and this effect was most significant when ionic strength increased from 0 to 0.15 M, especially at relatively low aqueous concentrations.  相似文献   

20.
梅博文  刘厚仁 《沉积学报》1989,7(4):133-140
从华北西部和南部五个煤矿取得的石炭、二叠系腐殖煤的饱和烃馏分中,经GC和GC/MS分析，检测出了较丰富的二萜类生物标志物。根据质谱特征与卡瓦保留值，并对照文献谱图，确认其中包括五个具有贝壳松烷骨架的四环二萜烷(即ent-白叶烷、16α(H)-和16β(H)-扁枝烷、16α(H)-和16β(H)-贝壳松烷)，以及一个三环的异海松烷。一个完整的四环二萜烷系列在我国华北石炭、二叠系腐殖煤中的发现在北半球很可能属首次。这些二萜类内组成在时间和空间上的差异分布，可能反映古植物群演化与分布的变化。扁枝烷和贝壳松烷的立体化学构型，可提供重要的有机成熟度信息。  相似文献   

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