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1.
Structural studies of a sulphur-rich kerogen and macromolecular oil fractions from the Monterey Formation were performed by selective sequential chemical degradation. The method provides low-molecular weight compounds as former building blocks of the network which allow detailed analyses on a molecular level. The degradation sequence is based on three subsequently performed reactions—a selective cleavage of sulphur bonds in the first step carried out with Ni(0)cene/LiAlD4, an ether and ester bond cleavage (BCl3), and an oxidation of aromatic entities by ruthenium tetroxide as a final step. Each step of this sequence afforded a considerable amount of low-molecular weight material which was separated chromatographically and studied by GC and GC/MS, while the high-molecular weight or insoluble fractions were subjected to the next reaction step.The chemical degradation products—hydrocarbons and carboxylic acids—are discussed in terms of incorporation into the macromolecular structure, distribution of heteroatomic bridges and the genetic relationships between the different macromolecular crude oil fractions and kerogen.Labelling experiments with deuterium provided evidence for a simultaneous linkage by oxygen and sulphur functionalities or by aromatic units and sulphur bonds of cross-linking macromolecular network constituents.The determination of sulphur positions in the macromolecule suggests early diagenetic sulphur incorporation into the biological precursor compounds and subsequent formation of a cross-linked network.  相似文献   

2.
Substantial amounts of alcohols occur in the desulfurization products of sulfur-rich nonpolar macromolecular fractions (NPMF) isolated from two crude oils and a sediment extract. These macromolecularly bound oxygenated compounds have been investigated in detail. Released straight chain components may have a hydroxy functionality at any position of the carbon skeleton and without any isomer predominance. Furthermore, the carbon-number distributions are very similar for the different alcohol isomers in each case and resemble those of the aliphatic hydrocarbons released by desulfurization. Thus, released hydrocarbons and alcohols likely originate from common functionalized precursors, most probably from polyunsaturated lipids of biological origin. Furthermore, they may derive from polyunsaturated components formed by elimination reactions on functionalized precursors which incorporated oxygen in free or already bound form at an early stage of diagenesis. The presence of hydroxyl functionalities at every position in the carbon skeleton suggests that double bond isomerization probably occurred in linear components prior to oxygen incorporation. Similarly, 2-hydroxy stanols released by desulfurization most likely result from oxygen uptake into Δ2-sterenes during diagenesis. The presence of mid-chain hydroxylated phytanols in the degradation products with OH-group mainly at the tertiary positions indicates that they result (at least partially) from oxygen incorporation into unsaturated phytane skeletons. Additional functionalities in the oxygenated substances, such as double bonds, aldehydes or allylic alcohols, may have served as substrates for reactions with sulfur species, resulting in sulfur-rich cross-linked macromolecular structures.The type of oxygen groups present in the macromolecules could be partially assigned by sequential chemical degradation experiments. The results indicate that free OH-functions are not abundant. Part of the oxygen is present as carboxylic acid, ester and ketone functions. However, the nature of a substantial part of the oxygen species remains unclear.  相似文献   

3.
Stepwise chemical degradation involving cleavage of ester bonds (KOH/MeOH), sulfide and remaining ester bonds (Li/EtNH2), ether bonds (HI/LiAlH4) and sub-units linked to aromatic moieties (RuO4) has been carried out on the kerogens of two immature sulfur-rich marls (IV-1.4 and 1.8, TOC ca. 1.5%) from evaporitic cycle IV of the Gesosso-solfifera Formation (Messinian, Vena del Gesso, Italy). Up to 80% of the organic matter was converted to solvent-soluble material, with the greatest proportion released by Li/EtNH2. The majority by far of the extracts comprises polar macromolecular material which is thought to correspond to high molecular weight sub-units of the kerogen. Quantification of the small amounts (<1%) of the released GC-amenable components indicates that diagenetic sulfurization was more important in the case of kerogen IV-1.4 but that the extent of oxygen sequestration was similar in both cases; the distributions of biomarkers released by ether cleavage of the desulfurized residue and polar fraction showed differences which reveal heterogeneity in the building blocks making up different macromolecular fractions.  相似文献   

4.
Pyrolysis with and without tetramethylammonium hydroxide (TMAH), vacuum pyrolysis, and solid state 15N nuclear magnetic resonance (NMR) were used to examine the macromolecular insoluble organic matter (IOM) from the Orgueil and Murchison meteorites. Conventional pyrolysis reveals a set of poorly functionalized aromatic compounds, ranging from one to four rings and with random methyl substitutions. These compounds are in agreement with spectroscopic and pyrolytic results previously reported. For the first time, TMAH thermochemolysis was used to study extraterrestrial material. The detection of aromatics bearing methyl esters and methoxy groups reveals the occurrence of ester and ether bridges between aromatic units in the macromolecular network.No nitrogen-containing compounds were detected with TMAH thermochemolysis, although they are a common feature in terrestrial samples. Along with vacuum pyrolysis results, thermochemolysis shows that nitrogen is probably sequestered in condensed structures like heterocyclic aromatic rings, unlike oxygen, which is mainly located within linkages between aromatic units. This is confirmed by solid state 15N NMR performed on IOM from Orgueil, showing that nitrogen is present in pyrrole, indole, and carbazole moieties.These data show that amino acids are neither derived from the hydrolysis of IOM nor from a common precursor. In order to reconcile the literature isotopic data and the present molecular results, it is proposed that aldehydes and ketones (1) originated during irradiation of ice in space and (2) were then mobilized during the planetesimal hydrothermalism, yielding the formation of amino acids. If correct, prebiotic molecules are the products of the subsurface chemistry of planetesimals and are thus undetectable through astronomical probes.  相似文献   

5.
Hopanoids bound into the insoluble organic matter (kerogen) of Recent sediments from a freshwater lake (Priest Pot) and an anoxic sulphidic fjord (Framvaren) were released by hydropyrolysis and examined by gas chromatography-mass spectrometry. Bound hopanoids are present in high concentration (190-1400 μg/g TOC) and represent 22 to 86% of the total analysable hopanoids (i.e., bound and solvent-soluble), this proportion increasing with depth in Framvaren Fjord. The hopanes generated by hydropyrolysis contain higher amounts of the C35, C32, and C30 homologues, reflecting the carbon number distribution of the bound hopanoids and indicating that both biohopanoids (C30 and C35) and their diagenetic products (dominated by C32) are incorporated into the kerogen on a timescale of only 0 to 350 years. Sequential (multiple temperature) hydropyrolysis experiments gave an indication of the relative strengths of bonds being cleaved in association with hopane generation: The hopanoids of a sediment from Priest Pot are almost entirely bound by strong covalent bonds, interpreted to be mainly ether linkages, whilst a Framvaren sediment contains hopanoids that are bound by a mixture of weak di-/polysulphide linkages and stronger ether bonds. Labelling with deuterium indicated that the strong covalent linkages dominate, even for the Framvaren sediment.  相似文献   

6.
An immature sulfur-rich marl from the Gessosso-solfifera Formation of the Vena del Gesso Basin (Messinian, Italy) has been subjected to hydrous pyrolysis (160 to 330°C) to simulate maturation under natural conditions. The kerogen of the unheated and heated samples was isolated and the hydrocarbons released by selective chemical degradation (Li/EtNH2 and HI/LiAlH4) were analysed to allow a study of the fate of sulfur- and oxygen-bound species with increasing temperature. The residues from the chemical treatments were also subjected to pyrolysis–GC to follow structural changes in the kerogens. In general, with increasing hydrous pyrolysis temperature, the amounts of sulfide- and ether-bound components in the kerogen decreased significantly. At the temperature at which the generation of expelled oil began (260°C), almost all of the bound components initially present in the unheated sample were released from the kerogen. Comparison with an earlier study of the extractable organic matter using a similar approach and the same samples provides molecular evidence that, with increasing maturation, solvent-soluble macromolecular material was initially released from the kerogen, notably as a result of thermal cleavage of weak carbon–heteroatom bonds (sulfide, ester, ether) even at temperatures as low as 220°C. This solvent-soluble macromolecular material then underwent thermal cleavage to generate hydrocarbons at higher temperatures. This early generation of bitumen may explain the presence of unusually high amounts of extractable organic matter of macromolecular nature in very immature S-rich sediments.  相似文献   

7.
为了构建内蒙古扎鲁特地区无烟煤的分子结构模型,采用工业分析、元素分析、核磁共振碳谱、高分辨率透射电镜和X射线光电子能谱等测试方法对该地区无烟煤的分子结构进行研究。结果表明无烟煤分子结构中以芳香碳为主,脂肪碳以短烷基侧链和环烷烃为主。煤分子结构中氧原子主要以酚羟基和醚氧基的形式存在,氮原子主要以吡咯型氮和吡啶型氮的形式存在,硫原子主要的赋存形态是硫醇硫酚。结合由核磁共振碳谱测得的煤结构参数和由高分辨率透射电镜测得的芳香环尺寸和含量,构建了无烟煤大分子平均结构模型。对构建的模型进行了结构优化与能量分析,发现煤分子结构的芳香片层趋于平行排列,非键结势能中的范德华力是保持煤结构稳定的主要因素。本研究为采用分子动力学模拟从分子尺度研究扎鲁特地区无烟煤在石墨化过程中,其芳香碳层的拼叠过程及其反应路径提供了模型基础。   相似文献   

8.
Hydrogenolysis with rhodium-on-charcoal was found to be an effective method for degrading different types of macromolecular material of geological origin. Between 6 and 70% of coals, kerogens and humic substances were transferred into low-molecular-weight soluble materials. The reaction products contained a series of monomeric and dimeric lignin-derived compounds which strongly suggest intact fossil lignin as their source. The substitutional patterns of the released phenols reflect the type and amount of terrestrial organic matter input and diagenetic alterations.In addition to the lignin constituents, a complete suite of hydrocarbons differing from those of the low-molecular-weight fraction was obtained after hydrogenolysis of the sample material. Hydrocarbons released by the hydrogenolytic degradation technique were attached to the polymeric matrix as monoor polyethers. Deuterium was used in the degradation experiment to evaluate the sites of chemical bonds by which 4-methylsteranes and hopanes are attached to the kerogen matrix. These experiments suggested a linkage of the released molecules with ring A and the side-chain, respectively.  相似文献   

9.
Ether functionalities form an important cross-linking structure within the macromolecular organic matrix of lignites and coals. To obtain a deeper insight into the complex internal structure of such macromolecules and the maturation related changes of the ether compounds within the network structure, boron tribromide (BBr3) ether cleavage was applied to a series of lignite and coal samples of different maturity (R0 0.27-0.80%) obtained from coal mines and natural outcrops from the North and South Island of New Zealand. Terminal ether-bound alcohols rapidly decrease during diagenesis and occur only in low amounts during the catagenetic stage. Comparison between ester- and ether-bound terminal alcohols indicates a parallel decreasing trend during the diagenetic stage, suggesting that the stability differences between both linkages are not large enough to be observed in maturation processes over geological time scales. Polyether compounds were detected with chain length up to five carbon atoms. After a small decrease during the diagenetic phase these compounds occur in relatively high concentrations, even in the main catagenetic stage. This suggests that these linkage structures represent important cross-linking substructures within the macromolecular matrix of lignites and coals being sterically protected within the macromolecular network during the maturation process. Additional cross-linking substructures were (poly)ether aromatics, esters and ketones.  相似文献   

10.
The major organic component of carbonaceous chondrites is a solvent-insoluble, high molecular weight macromolecular material that constitutes at least 70% of the total organic content in these meteorites. Analytical pyrolysis is often used to thermally decompose macromolecular organic matter in an inert atmosphere into lower molecular weight fragments that are more amenable to conventional organic analytical techniques. Hydropyrolysis refers to pyrolysis assisted by high hydrogen gas pressures and a dispersed catalytically-active molybdenum sulfide phase. Hydropyrolysis of meteorites has not been attempted previously although it is ideally suited to such studies due to its relatively high yields. Hydropyrolysis of the Murchison macromolecular material successfully releases significant amounts of high molecular weight PAH including phenanthrene, carbazole, fluoranthene, pyrene, chrysene, perylene, benzoperylene and coronene units with varying degrees of alklyation. Analysis of both the products and residue from hydropyrolysis reveals that the meteoritic organic network contains both labile (pyrolysable) and refractory (nonpyrolysable) fractions. Comparisons of hydropyrolysis yields of Murchison macromolecular materials with those from terrestrial coals indicate that the refractory component probably consists of a network dominated by at least five- or six-ring PAH units cross-linked together.  相似文献   

11.
Chemical degradations of coal resins, coal asphaltenes and coal residues have been performed with selective, non-oxidative reagents. The coal comprise samples a rank interval 0.30–1.21 %Rm. Degraded low-molecular-weight compounds were analyzed by GC-MS. The distributions of pentacyclic terpanes, isoprenoids, n-alkanes, acids and alcohols obtained as degradation products illustrate a considerable variability between the macromolecular coal fractions. A structural study on the molecular level of the degraded compounds from coal resins and coal asphaltenes show their potential to generate hydrocarbons during coalification process.  相似文献   

12.
A series of hydropyrolysis (HyPy) experiments have been conducted on a small suite of authentic polycyclic aromatic hydrocarbons (PAHs: coronene, pyrene and perylene) to investigate the HyPy behaviour of these PAHs. This information may help in the interpretation of the structural significance of aromatic HyPy products, often detected in high abundance, from high maturity kerogens. The PAHs were separately treated by HyPy and were all susceptible to some extent of hydrogenation. Perylene also decomposed into low molecular weight aromatics (e.g. methylbiphenyls). Structurally, perylene is much less stable than the more condensed PAHs coronene and pyrene. The total product concentrations (wt% of starting PAH) from all HyPy experiments were consistently less than 100 wt%, probably due to either the condensation of semi-volatile products on walls of the transfer line prior to reaching the HyPy trap or the inefficient cold trapping of highly volatile products. Hydrogenation of PAHs was prevalent and was found to be significantly influenced by the addition of a Mo-S based catalyst and potentially the C/Mo ratio, but largely independent of the two final temperatures used (520 °C and 550 °C). The fully aromatised and hydrogenated products for any stable ring system may provide a general indication of the size distribution of aromatic units within the kerogen structure.  相似文献   

13.
Polycyclic aromatic hydrocarbons (PAH) in sediment cores from Lake Lucerne, Lake Zürich, and Greifensee, Switzerland, and Lake Washington, northwest U.S.A., have been isolated, identified and quantified by glass capillary gas chromatography and gas chromatography/mass spectrometry. Surface sediment layers are greatly enriched in PAH—up to 40 times—compared to deeper layers. In addition, concentration increases in upper sediments generally correspond to increasing industrialization and urbanization in the catchment basins of the lakes. Few PAH could be detected in pre-industrial revolution sediments, indicating that background levels for most PAH in aquatic sediments are extremely low.These results are consistent with an anthropogenic source for most of the aromatic hydrocarbons present in the modern sediments. A comparison of PAH distributions in the sediments and in possible source materials shows that urban runoff of street dust may be the most important PAH input to these lacustrine sediments. There is evidence that a significant contribution to the PAH content of street dust comes from material associated with asphalt.  相似文献   

14.
Pyrolysates of high-molecular-weight sedimentary fractions of the Duvernay Formation (Western Canada Basin) are dominated by 1,2,3,4- and 1,2,3,5-tetramethylbenzene, which, generated via beta-cleavage, indicate the presence of diaromatic carotenoids in the macromolecular aggregates. This was substantiated by desulphurization of sulphur-rich aggregates of the polar fraction, which released (partly) hydrogenated carotenoids. Furthermore, these components were important constituents of the aromatic hydrocarbon fractions and related oils. Apart from renieratane and isorenieratane, 1H NMR analysis established the aromatic substitution pattern of the most abundant component present, which was identified as a diaromatic compound with an unprecedented 2,3,6-/3,4,5-trimethyl aromatic substitution pattern. Molecular and isotopic analyses of both soluble and insoluble fractions of organic matter revealed relationships between diagenetically-derived carotenoids found in bitumen and related oils and their precursors incorporated into high-molecular-weight fractions. Aryl isoprenoids, important components in extracts and oils, were apparently derived from thermal cracking of bound diaromatic carotenoids rather than cleavage of free carotenoids as previously suggested. Furthermore, products derived from diaromatic carotenoids were substantially enriched in 13C relative to n-alkanes of algal origin. Together with the characteristic carotenoids, this isotopic enrichment provides evidence of significant contributions from photosynthetic green sulphur bacteria (Chlorobiaceae), which fix carbon via the reversed tricarboxylic acid (TCA) cycle. In spite of the prominence of these molecular signals, the overall isotopic composition of the organic matter indicated that only a very small portion of the preserved organic carbon was derived from the biomass of photosynthetic green sulphur bacteria.  相似文献   

15.
《Applied Geochemistry》1997,12(3):327-332
This paper describes an investigation carried out in 1990 by the Geological Survey of Norway into the contamination of soils and groundwater at a former industrial site. The site covers an area of 0.5 ha and was used for a small plant generating gas for lighting purposes and from the middle of the last century for a small electrochemical facility (The Nidelven Brass and Iron Co. Est. 1843). The site is located immediately adjacent to the Nidelva river, in the central area of the city of Trondheim (pop. 150,000), Norway. Soil samples were obtained from 10 boreholes drilled to approximately 4 m depth. Analysis of the heavy metal content of these soil samples was subsequently undertaken. A subset of the samples was analysed for tar, including polycyclic aromatic hydrocarbons (PAH). The concentrations of Cd, Co, Cr, Hg, Ni and PAH in the soils are all below the maximum permissible levels recommended by the authorities. In certain localities, however, the concentrations of Cu, Pb and Zn are higher than the action levels at which remediation is required. It is estimated that approximately 4400 m3 of soil are contaminated, but that the contaminants are bound so tightly to the soil that the risk of dispersion of the pollutants is negligible.Groundwater samples were also collected from 4 monitoring wells installed at the site. Analysis of these groundwaters indicated the presence of only slightly contaminated groundwater. With the exception of 1 sample with a slightly higher concentration of Cu, the concentrations of PAH and the trace metals Co, Cr, Cu, Hg, Ni and Zn in the groundwater were below natural background values. This confirms the results from the soil analyses in which it was concluded that the dispersion of contaminants is negligible. A TCLP-extraction of 5 soil samples with high concentrations of Cu, Pb and Zn showed that only Zn was released in amounts exceeding the water guidance levels requiring monitoring.This study therefore indicates that the contaminants found in the ground at the site are strongly bound to the soil and are unlikely to be mobilised. This, combined with a slow base-flow, causes an insignificant contamination contribution to the waters in the River Nidelv. It should be noted, however, that the leaching experiments were not undertaken on the samples containing the highest Cu, Pb and Zn concentrations.  相似文献   

16.
 Surface sediments, suspended particulate matter and fluffy-layer material, collected in the Arkona Basin and the Pomeranian Bay during 1995–1997, as well as air particulate matter, collected on the island of Rügen during August 1995, were analysed for total organic carbon content, saturated and polycyclic aromatic hydrocarbons (PAH). The resulting concentrations and distributions of these compounds and molecular PAH ratios are discussed in terms of matrix, origin of the organic matter and seasonal variations. The data show that the Oder river can be identified as a major source for PAH transported into the southern part of the Arkona Basin. A strong atmospheric input of PAH is noted for the central and northern part of the basin. In general, anthropogenic and bacterially degraded hydrocarbons bound to organic carbon-rich and small particles are mainly deposited in the basin center, whereas their natural counterparts accumulate mainly on the basin flanks covered by coarser grained sediments. Received: 2 March 1999 · Accepted: 8 June 1999  相似文献   

17.
Flame coal (Janina Mine, Poland) was an object of geochemical analyses for changes caused by the process of microbial desulphurisation. Ash content, beryllium, chromium, zinc, cobalt, lithium, manganese, copper, molybdenum, nickel, lead and vanadium concentrations were investigated in coal extracts, its macromolecular part, semi-coke and polar compound fractions of extracts and pyrolysates of crude and biodesulphurised coal density fractions. The macromolecular part of extracted density fractions was pyrolysed giving semi-coke and pyrolysate. These were separated into aliphatic hydrocarbons, aromatic and polar compounds by thin layer chromatography (TLC). Distributions of aliphatic and aromatic hydrocarbons in pyrolysates of the crude and desulphurised coal density fractions were compared by gas chromatography-mass spectrometry (GC-MS). Extracts, extracted density fractions, semi-coke and polar compound fractions were analysed for concentrations of trace elements. In the crude coal their concentrations in the macromolecular part are related only to coke. However, in the desulphurised coal the participation of the particular trace element increases in pyrolysate polar compound fractions. Its values are in the range from 1% (Mn) to 100% (Cr and Mo). These changes are the best seen in the 1.80-2.30×103 kg/m3 density fraction. Very high concentrations of trace elements were found in pyrolysate of desulphurised coal density fraction. This can be explained by the partial decomposition of coal macromolecule resulting from desulphurisation. Significant side-cleavage of peripheral groups and lighter aromatic hydrocarbons is possible. The effects of bacterial influence were manifested by the increase of polar compounds contents both in pyrolysates and extracts of the desulphurised coal and changes in distribution of aliphatic and aromatic hydrocarbon as pyrolytical products. These effects increase with mineral substance contents. Moreover, the increase of trace element concentration in coal organic matter occurs. It is reflected by the increase of participation of coal pyrolysate polar fraction in the total concentration of analysed elements in the macromolecular part of a given density fraction. The presented results are a part of the larger research aimed to find an influence of desulphurisation on chemical and technological properties of coal.  相似文献   

18.
Ruthenium tetroxide oxidation was used to examine the macromolecular insoluble organic matter (IOM) from the Orgueil and Murchison meteorites and especially to characterize the aliphatic linkages. Already applied to various terrestrial samples, ruthenium tetroxide is a selective oxidant which destroys aromatic units, converting them into CO2, and yields aliphatic and aromatic acids. In our experiment on chondritic IOM, it produces mainly short aliphatic diacids and polycarboxylic aromatic acids. Some short hydroxyacids are also detected.Aliphatic diacids are interpreted as aliphatic bridges between aromatic units in the chemical structure, and polycarboxylic aromatic acids are the result of the fusion of polyaromatic units. The product distribution shows that aliphatic links are short with numerous substitutions. No indigenous monocarboxylic acid was detected, showing that free aliphatic chains must be very short (less than three carbon atoms). The hydroxyacids are related to the occurrence of ester and ether functional groups within the aliphatic bridges between the aromatic units. This technique thus allows us to characterize in detail the aliphatic linkages of the IOMs, and the derived conclusions are in agreement with spectroscopic, pyrolytic, and degradative results previously reported.Compared to terrestrial samples, the aliphatic part of chondritic IOM is shorter and highly substituted. Aromatic units are smaller and more cross-linked than in coals, as already proposed from NMR data. Orgueil and Murchison IOM exhibit some tiny differences, especially in the length of aliphatic chains.  相似文献   

19.
Lipids directly extracted by organic solvents from sediment of a small eutrophic lake (Crose Mere) comprise free hydrocarbons, alcohols, sterols and monocarboxylic acids together with an esterified component yielding additional amounts of alcohols, sterols and monocarboxylic acids on saponification. The carbon-number distributions of the free lipid compound classes indicate a major contribution from allochthonous sources whereas the distributions within compound classes released on saponification are attributable to autochthonous sources. The more advanced state of decomposition of terrestrial biota relative to aquatic biota and the composition of the source organisms are postulated to be factors leading to the differences in distribution of corresponding free and esterified lipid classes. Acid hydrolysis of solvent-extracted sediment liberates additional lipid constituents belonging to the above compound classes. Of these bound lipids, the n-alkanes and branched/cyclic alkanoic acids show a more significant bacterial contribution than do the corresponding components obtained by solvent extraction alone.  相似文献   

20.
Exchange of carbon bound hydrogen has been observed when alkenes, saturated and aromatic hydrocarbons are heated at moderate temperatures on carbonaceous surfaces (activated carbon and coal). Isomerisation of alkenes and the formation of hydrogenated/dehydrogenated products from the saturated and aromatic reactants resulted. A suite of crude oils from the Carnarvon Basin (Western Australia) have been analysed with a view to comparing their relative abundances of structurally similar hydrocarbons. The consistent relationships between hydrocarbons in crude oils that are chemically related via hydrogenation/dehydrogenation reactions suggest that a hydrogen exchange process similar to that demonstrated in laboratory experiments occurs during crude oil formation in sedimentary rocks.  相似文献   

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