Aromatic fractions, polar

In the manufacture of base oils, one of the refining operations is to extract with the aid of an appropriate solvent (furfural most often) the most aromatic fractions and the polar components. When free of solvent, the extracted aromatic fraction can eventually be refined, particularly to remove color or to thicken it, or still further, to fractionate it. The term, aromatic extract is used in every case. 

Gas oil fractions (204—565°C) from coal Hquefaction show even greater differences in composition compared to petroleum-derived counterparts than do the naphtha fractions (128). The coal-gas oils consist mostly of aromatics (60%), polar heteroaromatics (25%), asphaltenes (8—15%), and saturated... 

Another variation of the preceding method is to apply HPLC to fractionate the cleaned-up aliphatic-aromatic fraction from flash colurim separation of soluble organic matter as it is performed in the Chevron laboratory, for example, as described in Reference 2. A Waters HPLC system equipped with a preparative Whatman Partisil 10 silica column (9.4 X 500 mm), a HPLC pump, and two detectors for separation monitoring (a UV and refractive index detector) are used, giving three fractions of aliphatic hydrocarbons, mono-, di-, and triaromatics and polar compounds. The hrst two fractions are eluted with hexane, whereas polar compounds are eluted with... 

Each oil-dispersant combination shows a unique threshold or onset of dispersion [589]. A statistic analysis showed that the principal factors involved are the oil composition, dispersant formulation, sea surface turbulence, and dispersant quantity [588]. The composition of the oil is very important. The effectiveness of the dispersant formulation correlates strongly with the amount of the saturate components in the oil. The other components of the oil (i.e., asphaltenes, resins, or polar substances and aromatic fractions) show a negative correlation with the dispersant effectiveness. The viscosity of the oil is determined by the composition of the oil. Therefore viscosity and composition are responsible for the effectiveness of a dispersant. The dispersant composition is significant and interacts with the oil composition. Sea turbulence strongly affects dispersant effectiveness. The effectiveness rises with increasing turbulence to a maximal value. The effectiveness for commercial dispersants is a Gaussian distribution around a certain salinity value. 

Heavy fractions of Wilmington crude contained more aromatics and polars compared with a conventional HVGO. The conversion of the Wilmington fractions increased with boiling point range. The zeolitic contribution to the conversion decreased while the matrix contribution remained constant and the contribution from thermal cracking increased. 

Whereas the relative amount of aromatics remained fairly constant as sulfur conversion level was increased to 92-94%, the relative amount of sulfur in the aromatic fraction decreased markedly. This also is depicted in Figure 3. Polar aromatics are intermediate to the aromatics and asphaltenes in regard to this behavior. 

The region of the map below the pentane-insoluble boundary corresponds to pentane-deasphalted oil from the original residuum. The saturate, aromatic, and polar fractions were separated by adsorption of the deasphalted oil over clay. The saturate fraction shows a zero carbon residue and the aromatic fraction is only a little higher at 0.7%. The coke-forming constituents in the deasphaltened oil are the polar aromatics that have a carbon residue of 15.4. The carbon residue balance shown in the insert table shows that almost all of the coke-forming mate-... 

The results in Figure 1 can be interpreted in terms of general ring structures with the hydrocarbon classes. The peak for the polypolar aromatic fraction at 160° C probably is caused by polar-monocyclic compounds and the peak at 240° C is probably the result of polar dicyclic compounds. The broad curve in the monoaromatics centering at 275°C is probably mainly caused by alkyl-substituted tetralins while the peaks... 

Table IX shows a similar method of calculating the polar aromatics factor. The data for these calculations are derived from Table III. Table III indicates that the polar aromatic fractions from the three slurry oils have an aromaticity of approximately 0,75. The calculation shows that approximately 45.7% of the polar aromatic molecules remain in the slurry oil. Similar calculations with a number of reduced crudes and slurry oils derived from those reduced crudes has indicated that approximately 46% of the polar aromatic molecules remain in the slurry oil.

The gas chromatograms of the hydrocarbon fractions indicate that asphaltene consists of complex macromolecules that decompose to yield a wide distribution (from C10 to - Qjs) of molecules within each of the saturate, mono-, di-, and poly aromatic and polar classes. 

Separations. The asphaltene fractions were obtained by solvent extraction with benzene and subsequent precipitation with cyclohexane. The cyclo-hexane-soluble fractions were separated into saturate, aromatic, and polar aromatic fractions by the clay-gel technique, ASTM D-2007 (modified). This separation is also applicable to asphaltenes. 

Table I summarizes the analytical results for deasphaltened Athabasca bitumen (without prior distillation) on a series of columns used in the USBM-API 60 procedure, and those obtained by the simplified silica and alumina class separation scheme. As seen, the results are comparable provided that the polyaromatic and polar fractions are combined. The total analyses of the separated fractions obtained by the two methods listed in Table II are also in good agreement, with the exception that sulfur values from the simplified procedure are somewhat higher in all aromatic fractions except the polyaromatic/polar fraction.

Separation Techniques. The complexity of the organic composition of coal-derived liquids, shale oil, and their related effluents presents a formidable challenge to the analytical chemist. Our approach to this problem has been the classical separation technique based on acid-base-neutral polarity of the organic compounds. We further subdivide the neutral fraction into aromatic and non-aromatic fractions using dimethyl-sulfoxide (DMSO) extraction. DMSO effectively removes multiringed aromatic compounds with great eflBciency (85-95%) for these complex mixtures and thus allows a straightforward analysis for polynuclear... 

The oil shales were retorted to give oil yields, and the shale oils were analysed chromatographically to give gas chromatographic fingerprints. Bitumens were also extracted from the unretorted shales and analysed for their content of aliphatic, aromatic and polar compounds some of these fractions... 

Bitumens, were separated by chromatography, urea clathration and 5A molecular sieve occlusion before and after analyses of many of the aliphatic sub-fractions by GC and gas chromatography-mass spectrometry (GC-MS). Experimental details are noted in a previous publication (16) in which the distribution of cyclic alkanes in two lacustrine deposits of Devonian (N.E. Scotland) and Permian (Autun, France) age, (the D and C series samples) were discussed, Chromatographic separation into aliphatic, aromatic and polar compounds of the bitumens extracted from the shales gave the results shown in Table VI. Carbon Preference Indices and pristane/phytane ratios were measured in this work space limitations precluded... 

The vacuum distillate from Paraho shale oil crude was separated on silica gel into three fractions - saturate, aromatic, and polar. The carbon-13 NMR spectra indicated that these fractions contained 58, 15 and 36 percent,... 

The vacuum distillate was separated on silica gel into saturate, aromatic, and polar fractions by the procedure described earlier (4). The vacuum distillate comprised 33% of the crude shale oil and contained 1.82% (W/W) of nitrogen. The... 

Limited experiments with the aromatic fraction from the vacuum distillate indicated this material resembled the polar fraction much more than the saturate in pyrolysis behavior. This would be consistent with the carbon-13 nmr results,... 

A summary of the JF-5 yield data for all fractions stressed for various times at 450°C is presented in Table V, The saturate fraction affords the highest yield of JF-5 but the polar fraction also gives good yields. The maximum yields for these two fractions came at 60 minutes stress but the overall effect of time on yield was moderate. The results for the aromatic fraction were inconclusive because of limited amount of starting material. The general pattern of JP-5 yield for the vacuum... 

The potential n-alkane yield for the aromatic and polar fractions fell much below that of the saturates. This is consistent with the much lower wt,% unbranched alkyl group and average chain length data found by nmr. 

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