Aliphatic Hydrocarbon Fractions Research Articles

Diterpenoid hydrocarbons in sediments from an offshore (Labrador) well

Aliphatic hydrocarbon fractions isolated from sediments ( R 0 = 0.4%) of Eocene/Palaeocene age, taken between 2860 and 3055 m in an offshore (Labrador) well, were shown to be dominated by a number of compounds with Kovats Retention Indices in the range 1875–1975. Analyses of these hydrocarbons by gas chromatography and computerized gas chromatography-mass spectrometry suggested that they were tricyclic diterpenoids: interpretation of the mass spectra allowed structures to be assigned to some of the compounds and to be proposed for others. They appear to belong to the primarane, abietane and kaurane classes of hydrocarbons. The diterpanes have been used to detect cavings in the deeper sediments between 3055 and 3270 m. These compounds are either absent, or trace components only, of the DST-1 condensate (3212–3256 m) or oil impregnating a sandstone core (3250 m) and are only abundant in the cuttings from the same depth interval. This occurrence of diterpanes in cuttings from the reservoir interval is due mostly to cavings: resin-like materials, from which diterpanes are derived, have not contributed significantly to the genesis of the condensate.

Transformation of Syrian hamster embryo cells by synfuel mixtures

Existing Syrian hamster embryo (SHE) cell-transformation assay methods were modified to allow the assay of complex synfuel mixtures. A shale oil, high-molecular-weight, high-boiling distillates from two different solvent-refined coal (SRC) processes, and two crude petroleum samples caused transformation of SHE cells. Chemical fractionation of SRC-II heavy distillate and assay of resultant fractions allowed detection of significant transforming activity in chemical fractions, where such activity had not previously been observed. The polyaromatic-hydrocarbon-enriched fraction, neutral aliphatic hydrocarbon fraction, and neutral tar fraction all showed a positive response in the SHE assay. In addition, we confirmed earlier data showing that both the tar fractions (basic and neutral) and the soluble basic fractions from both SRC processes and shale oil contained genetically active materials.

Correlation of crude oils from the San Jorges Basin, Argentina

The aliphatic hydrocarbon fractions of sixty oils from the San Jorges Basin, Argentina have been analysed by computerized-gas chromatography-mass spectrometry. The initial aim of this study was the correlation of the oils using sterane and triterpane biomarkers. The oils could be divided into four groups which were distinguished by the relative proportions of regular to demethylated hopanes. Although it has been previously suggested that the demethylated hopanes found in oils could have resulted from biotransformation of the oils in the reservoir, in this basin the possibility that these compounds originated directly from the source beds cannot be entirely eliminated since the oils do not appear to be extensively biodegraded on the basis of their aliphatic hydrocarbon distributions. An alternative theory for the hydrocarbon distributions observed in these oils, is initially biodegradation of the oils in the reservoir followed by addition of non-degraded oil to produce a mixture of degraded and non-degraded oil.

Detection of aliphatic hydrocarbons derived by recent “bio-conversion” from fossil fuel oil in North Sea waters

The higher boiling point range of saturated aliphatic hydrocarbon fractions extracted from North Sea water have been re-investigated in detail with improved high resolution glass capillary columns suitable for high temperature gas-chromatography. The resulting chromatograms reveal hydrocarbon patterns, most of which have the same common feature: a smooth distribution of the long-chain n-alkanes combined with a lack of the branched alkanes normally expected for fossil fuel oil. Instead, two homologous series of iso- and anteiso-alkanes could be detected. Since this finding is always associated with traces of present or past fossil fuel oil contamination of the upper water column, these environmental n-, iso and anteisoalkanes are considered to be recently ‘bio-converted’ from fossil fuel oil hydrocarbons. They form a third group beside recent biogenic and fossil petrogenic hydrocarbons in the marine environment. Oil pollution records of the marine environment will have to take into account this group of microbial hydrocarbons.

Biogenic and pollutant aliphatic hydrocarbons in Mytilus edulis from the North Sea

Capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) have been used to examine the aliphatic hydrocarbon fraction of specimens of the mussel, Mytilus edulis, collected from the legs of a North Sea oil-production platform. In addition to an unresolved complex mixture (UCM) of fossil fuel pollutant hydrocarbons ( ca. 64 μg g −1 dry weight average), the fraction was dominated by large amounts ( ca. 21 μgg −1 dry weight) of C 31 and C 33 n-alkenes with 2, 3 and 4 double bonds. These alkenes have also been identified in the ubiquitous marine alga, Emiliania huxleyi, and in some species of fish taken from the North Sea. The close correspondence in the composition data suggest that, in the mussel, these alkenes arise from a biogenic dietary source, most probably from Emiliania huxleyi. This contention is supported by the identification in the mussel of unusual C 37, C 38 and C 39 unsaturated straight-chain ketones which have recently been shown to be biosynthesised by Emiliania.

Chromatographic separation of diasteriomeric isoprenoids for the identification of fossil oil contamination

In aliphatic hydrocarbon fractions of crude oils eight acyclic isoprenoid alkanes were separated from accompanying n-alkanes and iso-alkanes by high-performance glasscapillary gas chromatography. Four of these: 2,6,10-trimethyltetradecane (V), norpristane (IV), pristane (III), and phytane (II) could be resolved further to reveal a doublet produced by the different diastereoisomers. In these doublets the front peak represents stereoisomers formed during maturation of crude oil while the rear peak indicates the respective hydrocarbons carrying the original biogenic precursor configuration. This appearance of doublets demonstrates the loss of stereospecificity in hydrocarbons derived from phytol (I). By using the front peaks as diagenetic ‘maturity markers’ attributable to fossil fuels, hydrocarbon mixtures extracted from sea water samples contaminated with fossil oil could be investigated in detail. The quantitative relationship between recent biogenic and fossil fuel hydrocarbons could be determined in extracts in the lower boiling point range.

A preliminary organic geochemical investigation of the Kimmeridgian oil shales

The Kimmeridge oil shales have assumed renewed significance because of their role as the prime source-rock for North Sea oil, and because of the need to assess their potential as a possible future supply of shale oil. This paper presents the results of a preliminary investigation of selected Kimmeridge oil shales. The immature shales are rich in organic matter with a dominantly marine type II kerogen showing evidence of algal contributions and a general sparsity of land-derived, higher plant detritus. Column chromatographic and capillary column gas chromatographic examinations of bitumens, pyrolysates and pyrolysis gas chromatograms of kerogen isolates show a predominance of aromatics in the hydrocarbon fractions, with bitumen n -alkane gas chromatograms showing evidence of algal-derived organic matter with n -alkane maxima in the n -C 17 region. Possible contributions from lower land plants are indicated by a second n -alkane maximum at n -C 23 , whilst higher land plant detritus makes only a limited contribution. Reflected light microscopic examination of the shales also shows a general sparsity of recognizable land-derived woody or herbaceous material. Shale oil compositions reflect their pyrolytic origin, with unsaturates forming a large part of the aliphatic hydrocarbon fraction, together with significant amounts of isoprenoid alkanes; organic sulphur compounds are also prominent in the hydrocarbon fractions. Finally, considerable amounts of sterane and pentacyclic triterpane hydrocarbons have been found in the bitumen aliphatic hydrocarbon fractions, their distributions allowing Blackstone samples to be differentiated from those of lower stratigraphic levels.

Characterization of polynuclear aromatic and aliphatic hydrocarbon fractions of solvent-refined coal by glass capillary gas chromatography/mass spectrometry

Separation and identification of the polynuclear aromatic and aliphatic fractions of solvent-refined coal and its recycle oil were performed using a combination of solvent partition and Chromatographic fractionation procedures with glass-capillary gas chromatography (g.c.)/mass spectrometry (m.s.). Chromatographic profiles were generated for each fraction, and some semiquantitative data were also obtained. In total, 146 polynuclear aromatic components of SRC were tentatively identified by their molecular weights, as indicated by the mass spectra of the g.c. peaks. In addition, whereever possible specific isomers have been indicated, based on comparison of spectral characteristics and retention data.

Aliphatic hydrocarbons in sediments of Lake Washington1

The distribution of aliphatic hydrocarbons in sediments from several locations in Lake Washington have been determined by gas chromatographic, radiocarbon, and stable carbon isotope analyses. Most surface sediments contain an average of about 1,400 µg g‒1 dry wt total aliphatic hydrocarbons, of which about 10 µg g‒1 are n‐paraffins. Gas chromatograms of these hydrocarbons and radiocarbon ages of about 18,000 years B.P. for the aliphatic hydrocarbon fraction suggest the presence of a large component of petroleum hydrocarbons. By contrast, sediments at depth in the sediment column and deposited before about 1880 contain only about 30 µg g‒1 total aliphatics and about 5 µg g‒1 n‐paraffins. These hydrocarbon levels are believed to represent the aged natural background concentrations in Lake Washington. A number of cores analyzed in detail show an increase in hydrocarbon levels after 1880, which corresponds to the start of a period of growth for the adjacent metropolitan area.

Organic compounds in meteorites—I. Aliphatic hydrocarbons

The benzene-methanol extracts of thirty meteorites (carbonaceous chondrites, noncarbonaceous chondrites and graphite-troilite or troilite nodules from iron meteorites) were fractionated by silica gel chromatography and the aliphatic (n-heptane eluate) hydrocarbon fractions were analyzed by gas chromatography and gas chromatography-mass spectrometry. A study of the chromatograms from the n-heptane eluates permits the following conclusions: (1) Aliphatic hydrocarbons (predominantly paraffinic) were found in varying amounts in all the meteorites studied. The hydrocarbons ranged from 0.1 to 25.8 ppm for Type I, 8.3 to 150 ppm for Type II, 8.2 to 415 ppm for Type III, 0.1 to 3.2 ppm for the non-carbonaceous chondrites, and 2.8 to 15.5 ppm for the graphitic nodules. (2) Peaks corresponding to norpristane, pristane and phytane (in addition to normal and isomeric alkanes) were observed in practically all of the meteorites. Mass spectrometric evidence for the latter two isoprenoids was obtained in at least five different carbonaceous chondrites and one graphitic-troilitic nodule. Relatively low levels of pristane and phytane were found in the Type I carbonaceous chondrites and the non-carbonaceous chondrites. (3) No general predominance of odd over even carbon-number alkanes in the range analyzed was observed except for one sample of Orgueil in the n-C 22-n-C 27 range. An examination of the lower molecular weight alkanes in a few meteorite samples (Orgueil and Mokoia) showed a predominance of normal pentadecane over normal hexadecane. The hydrocarbons in three meteorites (Ivuna, Alais and Warrenton) had bimodal distributions indicating two syntheses or sources for the hydrocarbons. (4) Analysis of inside samples and samples from different sources showed the distribution of aliphatic hydrocarbons in Orgueil to be heterogeneous qualitatively and quantitatively. (5) Identical patterns were not observed within, or between, Wiik Types I and II. However, most of the meteorites of Type II were similar qualitatively in the n-C 15-n-C 21 range. In addition, a few Type III meteorites were similar qualitatively, in this range, to the meteorites of Type II. (6) The majority of the hydrocarbon patterns of the meteorites analyzed were similar, in the low molecular weight range, to chromatographic patterns of ancient sediments, crude oil, terrestrial graphite and other terrestrial samples. (7) The chromatographic patterns of the aliphatic hydrocarbons from the graphitic-troilitic nodules of iron meteorites were similar to those of Type II and some of Type I (Orgueil) carbonaceous chondrites. The external part of the nodules was found to contain 5 times more hydrocarbons than the inside suggesting either an external source of the hydrocarbons or that the hydrocarbons originally inside were partially destroyed or consumed.