Carbon number distribution patterns

Figure 9. Variation in the carbon number distribution pattern of the tricyclic sulfides in a Cerro Negro sample as shown by the mh = 251 fragmentogram from the SIR-GG/MS experiment. Note the intensity distribution of the peaks. Minima occur at C17, C23 and C28. (Reproduced with permission from Ref. 10. Copyright 1986, Pergamon Journals Ltd.)...

Figure 8. Carbon number distribution patterns (C15-C4q) of the midchain 2,5-dialkylthiophenes of the Jurf ed Darawish oil shale samples indicated.

Alkylthiophene(s), distribution in deep-sea sediments, 627-628,629f Alkylthiophene(s) as sensitive indicators of palaeoenvironmental changes carbon number distribution patterns of isoprenoid carbon skeleton alkylthiophenes, 465,47Qf carbon number distribution patterns of linear carbon skeleton alkylthiophenes, 461,463/ composition of subfractions, 449,450 depth profiles of alkylthiophenes,... 

The carbon number distribution of technical secondary alkanesulfonates determined by pyrolysis gas chromatography and mass spectrometry (GC-MS) is shown in Fig. 13 together with the corresponding carbon number pattern of the raw material paraffins obtained by GC [16]. Pyrolysis was performed in a crucible-modified SGE pyrojector after covering the mixture with quartz wool. The presence of up to 10 wt % of disulfonates in technical alkanesulfonates is demonstrated by fast atom bombardment and mass spectrometry (FAB-MS) (Fig. 14) [24],... 

Within the VGO saturates, distribution of paraffins, isoparaffins, and naphthenes is highly dependent on the petroleum source. The naphthenes account for roughly 60% of the saturates in a normal cmde oil. However, samples can be found having paraffins from <20 to >80%. In most samples, the / -paraffins from C2Q—are still present in sufficient quantity to be detected as distinct peaks in gc analyses. Some cmde oils show a nearly symmetric pattern of peaks such that each carbon number is present in regular progression up to a maximum around C -j. Other cmde oils show a similar distribution, but have preference for odd-numbered alkanes. Both the distribution and the selectivity toward odd-numbered hydrocarbons are considered to reflect differences in petrogenesis of the cmde oils. Although / -paraffins are distinct in the gc, these usually account for only a few percent of the saturates measured by gc. 

Spin-Spin Splitting. The splitting of a signal into two, three, four, or more peaks which show a binomial distribution pattern is an indication of the number of hydrogen atoms on neighboring carbon atoms which change the effective magnetic environment of the proton under observation by small but predictable amounts. 

A number of selected molecular parameters obtained from analysis of immature crude oils and sediment extracts are evaluated as indicators of palaeosalinity. The nature of these parameters is discussed taking into account the role of intermolecular and intramolecular incorporation of sulfur into specific functionalized lipids. Specific distribution patterns of methylated chromans and C20 isoprenoid thiophenes and the relative abundance of gammacerane are excellent indicators for palaeosalinity, whilst other parameters such as 14< (H),17a(H)/140(H),170(H) -sterane ratios, the pristane/phytane ratio, the even-over-odd carbon number predominance of n-alkanes and the relative abundance of C35 hopanes and/or hopenes may indicate palaeohypersalinity but are affected by environmental factors other than hypersalinity and by diagenesis. 

A more critical evaluation of the above mentioned ratios and phenomena reveals the usefulness of the various palaeosalinity indicators. Distribution patterns of methylated chromans and the relative abundance of gammacerane are not influenced by sulfur incorporation reactions and may directly reflect species distributions in the palaeoenvironment. To some extent this holds for 14a(H),17a(H)/140(H),170(H)-steraneratios as well, although incorporation of sulfur may influence this ratio and original A7/A5-sterol ratios do not always correlate with hypersaline environments. The isoprenoid thiophene ratio is highly useful as a palaeosalinity indicator since the distribution of the C20 isoprenoid thiophenes directly reflects the distribution of their substrates. The other parameters (pristane/phytane ratio, odd-over-even carbon number predominance of n-alkanes, relative abundance of C35 hopanes and/or hopenes) should be used with caution because they obviously depend on the quenching by sulfur of specific lipids, a process which is not restricted to hypersaline environments. 

The successive reactions of the olefins over these three catalysts may cause the different dependences of the product distribution on the conversion of carbon monoxide. Two reaction paths of olefins, which influence differently the conversion dependence of the distribution, may be of importance, that is, the hydrogenation and the chain growth. If the hydrogenation predominantly occurs, the distribution of carbon number is not affected by conversion. On the other hand, the chain growth may cause the conversion dependence of the distribution and the deviation from the S-F distribution pattern. 

One has seen that the number of individual components in a hydrocarbon cut increases rapidly with its boiling point. It is thereby out of the question to resolve such a cut to its individual components instead of the analysis by family given by mass spectrometry, one may prefer a distribution by type of carbon. This can be done by infrared absorption spectrometry which also has other applications in the petroleum industry. Another distribution is possible which describes a cut in tei ns of a set of structural patterns using nuclear magnetic resonance of hydrogen (or carbon) this can thus describe the average molecule in the fraction under study. 

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