Ring distribution, aromatic

In case of distributed aromatic rings, the position of substituents has to be defined by numbering around the ring, in such a way that the substituents are positioned at the lowest numbers possible, for example, the structure is 1,3-dichlorobenzene and not 1,5-dichlorobenzene ... 

Component mol fractions in each heavy naphtha cut are then determined by solution of a set of equations. The equations include aromatic and cycloparaffin ring balances as well as empirical equations relating ring distribution... 

The CCB-distillate fraction contains no ash or asphaltenes (n-Heptane insolubles at reflux). It has a low and narrow molecular weight distribution (Mn 290), and contains a very narrow aromatic ring distribution (3, 4, 5, and 6 rings). Table I gives the... 

CCB was fractionated into six asphaltene-free distillate fractions of varying boiling ranges and an asphaltene-rich non-distillable residue. Characterization of the distillate and the non-distillable fractions indicate significant differences in the asphaltene, ash, aromaticity, molecular weight and aromatic ring distributions. 

Three distillable fractions (Numbers 4, 5, and 6, in Table I) were thermally-treated at the same conditions (430°C for 3 hours) to investigate the effect of the aromatic ring distribution of the fraction on the pitch yield and composition. We found that increasing the number of 4, 5, and 6 aromatic rings results in increasing the pitch yield and the rate of toluene insolubles formation. The yield and composition of pitches prepared from distillate fractions, Numbers 4, 5, and 6 are given in Table V. 

The aromatic ring distribution determined for the major classes of compounds is shown in Table III. Four and five ring types are the most abundant. Hydrocarbons show higher average condensation than the heterocompounds however, most of the latter contain additional functional groups such as hydroxy groups and furanic rings. 

Table III. Aromatic Ring Distribution in Major Classes Found in EDS Asphaltenes...

The number of naphthenic rings in aromatic compounds is determined by the assignment of Z values, where every naphthenic ring indicates a deficiency of two hydrogens. The distribution of compound types indicates that monoaromatic compounds consist largely of mono-. 

This method gives the distribution by family (paraffins, isoparaffins, naphthenes with one or more rings, etc., aromatics) and by number of carbon atoms (up to a maximum of C33 for saturated compounds and up to C22 for aromatic compounds). 

The major part of the sulfur contained in crude petroleum is distributed between the heavy cuts and residues (Table 8.10) in the form of sulfur compounds of the naphthenophenanthrene or naphthenoanthracene type, or in the form of benzothiophenes, that is, molecules having one or several naphthenic and aromatic rings that usually contain a single sulfur atom. 

Electrophilic Aromatic Substitution. The Tt-excessive character of the pyrrole ring makes the indole ring susceptible to electrophilic attack. The reactivity is greater at the 3-position than at the 2-position. This reactivity pattern is suggested both by electron density distributions calculated by molecular orbital methods and by the relative energies of the intermediates for electrophilic substitution, as represented by the protonated stmctures (7a) and (7b). Stmcture (7b) is more favorable than (7a) because it retains the ben2enoid character of the carbocycHc ring (12). 

The alpha-olefin sulfonates (AOS) have been found to possess good salt tolerance and chemical stabiUty at elevated temperatures. AOS surfactants exhibit good oil solubilization and low iaterfacial tension over a wide range of temperatures (219,231), whereas less salt tolerant alkylaromatic sulfonates exhibit excellent chemical stabiUty. The nature of the alkyl group, the aryl group, and the aromatic ring isomer distribution can be adjusted to improve surfactant performance under a given set of reservoir conditions (232,233). 

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