Pentane insolubles

In modern terms, asphaltene is conceptually defined as the normal-pentane-insoluble and benzene-soluble fraction whether it is derived from coal or from petroleum. The generalized concept has been extended to fractions derived from other carbonaceous sources, such as coal and oil shale (8,9). With this extension there has been much effort to define asphaltenes in terms of chemical structure and elemental analysis as well as by the carbonaceous source. It was demonstrated that the elemental compositions of asphaltene fractions precipitated by different solvents from various sources of petroleum vary considerably (see Table I). Figure 1 presents hypothetical structures for asphaltenes derived from oils produced in different regions of the world. Other investigators (10,11) based on a number of analytical methods, such as NMR, GPC, etc., have suggested the hypothetical structure shown in Figure 2. 

Activity kg(mol of catalyst) xh 1atm 1 b Data of pentane insoluble fraction. 

In another test method (ASTM D4055), pentane-insoluble materials above 0.8 xm in size can be determined. In the test method, a sample of oil is mixed with pentane in a volumetric flask, and the oil solution is Altered through a 0.8- xm membrane filter. The flask, funnel, and filter are washed with pentane to transfer the particulates completely onto the filter, which is then dried and weighed to give the yield of pentane-insoluble materials. 

The final solvent to be tried was pentane. In the normal insolubles test, the pentane insolubles is normally over 25 % for the filtered extract solution. In the runs that were carried out with pentane, there were many operational problems, mainly associated with the large quantities of material precipitated. The filtrates produced contained very low levels of trace elements, but it was considered that the large amounts of material precipitated, most of which was difficult to remove from the autoclave, ruled this out as a potential solvent. 

From the results in Table 10 it can be seen that for the filtrate obtained after precipitation with toluene, that the fraction boiling to 150°C decreases. This is contraiy to what was e q>ected, in that the fluidity of the filtrate would indicate some retention of toluene, but the distillation shows otherwise. The fraction from 200>300"C shows an increase after precipitation, which again is difficult to explain in terms of a simple precipitation of high molecular weight species. In a difrerent set of experiments, a larger quantity (about 4 1) of material was prepared by precipitation of insolubles from filtered extract solution using toluene. To characterise the product, it was tested for pentane, toluene and THF insolubles. Following this, the material was stored in a vessel for about 2-3 weeks at 150°C prior to use. It was found that some of the material had evaporated and the extract was less fluid. The insolubles content was retested and it was found that the pentane insolubles had increased from 26 to 32 % the toluene insolubles from 8.5 to 9.8 % and the THF insolubles decreased from 2.0 to 1.8 %. It would thus appear that... 

The material boiling above 470°F is separated into oils, resins, and n-pentane insoluble residue. The residue is separated into asphaltenes and benzene insolubles by extraction with benzene while the oils are separated into aromatics and saturates. The saturates can be further separated into n-paraffins and non-n-paraffins with 5 A molecular sieves... 

ASTM D-4055-04. Standard Test Method for Pentane Insolubles by Membrane Filtration. 

The distinguishing features of resid feedstocks are (1) the presence of asphaltenes or pentane-insolubles, (2) high carbon residues, (3) the presence of metals, mainly nickel and vanadium, and (4) unknown endpoints insofar as boiling range is concerned. 

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-... 

Asphaltenes, wt% Pentane insolubles Flexane insolubles Fleptane insolubles 4.4 7.6 1.8 4.3... 

Used oil analysis. Used oil samples were analyzed for the following properties (Annual Book ASTM, 1985) viscosity ASTM D445, total base number ASTM D2896, total acid number ASTM D664, pentane insolubles ASTM D896, mass % zinc ASTM D811, mass % iron ASTM D811), "Active" zinc (differential infrared), carbonyl absorbance (differential infra-red). Over 250 samples were analyzed. 

Sulfur , vanadium A. nickel C, carbon residue nitrogen , pentane insolubles. 

In addition, the use of heptane as the precipitating medium yields a product that is substantially different from the pentane-insoluble material (Table I). For example, the H/C ratios of the heptane precipitate are markedly lower than those of the pentane precipitate, indicating a higher degree of aromaticity in the heptane precipitate. N/C, O/C, and S/C ratios are usually higher in the heptane precipitate, indicating higher proportions of the heteroelements in this material (13, 14). 

In modern terms, asphaltene is conceptually defined as the n-pentane-insoluble and benzene-soluble fraction whether it is derived from coal or from petroleum. There are a number of procedures used to isolate asphaltene (2-7), all of which appear to be reproducible (8) but do not necessarily provide equivalent end-products. The similarity between coal- and petroleum-derived asphaltenes begins and ends at the definition of the separation procedure. Puzinauskas and Corbett s (9) comments on asphalt may be paraphrased and applied to asphaltene. They state that the broad solvent classification is unfortunate it leads to misconceptions that petroleum and coal materials are alike, or at least similar. However, these two classes of materials differ not only in their origin, mode of manufacture and uses, but also in their chemical composition and physical behavior. 

Recently, petroleum residua have been studied extensively (I, 2) because of the increasing importance of heavier fuels. Both the asphaltene (pentane-insoluble) and maltene (pentane-soluble) components of residua are of interest, and since their properties overlap, a complete study of petroleum residua must consider both asphaltenes and maltenes. One area that has received considerable attention has been the size characterization of asphaltenes and maltenes (3, 4, 5). Size distribution data are useful both in understanding the fundamental chemistry of asphaltenes and maltenes and in observing the effects of various processes on residua sizes. 

The high viscosity at ambient temperature of coal liquids derived from hydrogenation processes has been related to the asphaltene (toluene-soluble, pentane-insoluble) and preasphaltene (toluene-insoluble, pyridine-soluble) fractions (1-5). Although the effect of preasphaltene concentration on the viscosity of coal liquids is dramatic, the increase caused by asphaltene materials has been attributed to hydrogen-bonding (6) and acid-base salt... 

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