Compound class distributions

McKay and Latham (1981) have also determined compound class distributions in the high-boiling distillates and the residua for four crude oils. As shown in Table VIII, the content of heteroatom compounds increases with increasing boiling point. The 675°C+ residuum may have nearly 10 times the acids, bases, or neutral Lewis (pyrrolic and amides unreactive to column resins) bases compared to the VGO portion (370-535°C). Grizzle et al. (1981) have also employed compound class separations and have observed similar trends. McKay and Latham (1981) calculated that each acid, base, or neutral nitrogen molecule in the <675°C residuum contains three to five heteroatoms. 

Fraction Compound Class Distribution Maxima Even/Odd Predominance Distribution Maxima Even/Odd Predominance ... 

Phenol IS both an important industrial chemical and the parent of a large class of compounds widely distributed as natural products Although ben zenol IS the systematic name for CgHsOH the lUPAC rules permit phe nol to be used instead Substituted derivatives are named on the basis of phenol as the parent compound... 

Fig. 4. Distribution of compound classes in cmde oils as a function of boiling point. Region A represents normal paraffins B, isoparaffins C, naphthenes ...

The primary product from Fischer-Tropsch synthesis is a complex multiphase mixture of hydrocarbons, oxygenates, and water. The composition of this mixture is dependent on the Fischer-Tropsch technology and considerable variation in carbon number distribution, as well as the relative abundance of different compound classes is possible. The primary Fischer-Tropsch product has to be refined to produce final products, and in this respect, it is comparable to crude oil. The primary product from Fischer-Tropsch synthesis can therefore be seen as a synthetic crude oil (syncrude). There are nevertheless significant differences between crude oil and Fischer-Tropsch syncrude, thus requiring a different refining approach.1... 

These features reflect the varying distribution of peaks in the lower and higher mass range and are capable to discriminate some compound classes (e.g., aliphatic and aromatic compounds). Typical mass ranges Ml to M2 are 33-50, 51-70, 71-100, 101-150. 

Dual Analytical-Bioassay. Many of the reports of polymer applications include dual analytical and bioassay features because these integrated studies help to focus attention on those compound classes and individual compounds that have the highest biological activity. These dual-purpose reports were counted in both categories to arrive at an application distribution of 85 analytical and 15 bioassay. The results given in these two report groups are discussed separately in the following sections. 

This section will review the nature of nickel and vanadium compounds present in petroleum oil, beginning with a detailed discussion of the metal compound categories and their molecular structure. The final section of this discussion will consider the manner in which these two classes of metal-bearing compounds are distributed or associated in the oil. 

Fractionation of petroleum in the refinery, to obtain streams with specific boiling ranges for various downstream processes, is performed by distillation in a crude unit. To determine how Ni and V compounds are distributed as a function of boiling point is, therefore, useful for evaluating their impact in the refinery. Petroleum may also be fractionated by solvent separation and chromatography to obtain more detailed information on the distribution of Ni and V compounds. This section will review the available literature on how metals are distributed in petroleum by boiling point and solubility class. It will also include some discussion of the structure of heavy oil in general and asphaltenes in particular. Vercier etal. (1981) have provided an excellent review of methods and procedures involved in petroleum fractionations. 

Field ionization mass spectrometry (FIMS) was applied to the different compound classes by Boduszynski et al. (1980). The FIMS molecular weight envelopes shown in Fig. 8 illustrate the similar but wide molecular weight distribution for each compound class. Furthermore, the FIMS molecular weight of about 1000 are considerably lower than those obtained by other methods in which intermolecular association may influence measured values. This is evident in Table IX by the comparison of VPO... 

Figure 14.15. Depth distribution of summed compound classes in soil profiles under Miscan-thus stands. L and Of describe organic litter layers mainly composed of the Miscanthus residues, Ah the humic mineral topsoil, and Bh an argillic subsoil horizon. Samples were taken in the years 1999 and 2000.

Several distinct maturity-related trends emerge through detailed examination of the traces (Figure 10). There are variations in both the relative abundance of different compound classes and within individual compound classes. The most marked trend is an increase in abundance of alkylbenzothiophenes relative to alkylthiophenes. This is clearly seen in Figure 11 where the ratio of these two compound classes is plotted with respect to depth. There is also an apparent shift in the internal carbon number distributions of both the alkylbenzothiophenes and alkylthiophenes. Specifically, there appears to be a preferential loss of short-chain alkylthiophenes and alkylbenzothiophenes (e.g. methylthiophenes decrease relative to dimethylthiophenes). The exception to this depth trend is the sample from 2480m which appears less mature (on the basis of sulfur compound distribution) than the adjacent sample of shallower depth (2020m). 

Figure 13.12 A SOM-based pharmacophore road map. Different sets of ligands were projected onto a SOM that was generated by using the complete COBRA library. Black areas indicate the characteristic distributions of the compounds. Crosses indicate empty neurons in the map, i.e., areas of pharmacophore space that are not populated by the respective compound class. All molecules were encoded by a topological pharmacophore descriptor (CATS) [4], Note that each map forms a torus.

The preceding reviews provide ranges and average total concentrations of the bound and free forms of amino acids and sugars in freshwaters. Very little information is provided about individual compounds within each compound class. The statistical summaries that are presented in this section describe not only the overall concentrations of the classes of compounds in freshwaters but also the relative proportions of individual compounds in each class of compounds. Moreover, the fuU distribution of results and summary statistics are presented for each individual compound. 

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