Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Composition of asphaltenes

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. [Pg.446]

Table I. Elemental compositions of asphaltenes precipitated by different flocculants from various sources (16)... Table I. Elemental compositions of asphaltenes precipitated by different flocculants from various sources (16)...
Table I. Elemental Compositions of Asphaltene Fractions Precipitated by Different Solvents... Table I. Elemental Compositions of Asphaltene Fractions Precipitated by Different Solvents...
Table II. Composition of Asphaltenes from Different Crude Sources Venezuela... Table II. Composition of Asphaltenes from Different Crude Sources Venezuela...
Many hundreds of studies have reported on the chemical composition of asphaltenes (28—44) and excellent summaries exist. We will only attempt to summarize some key findings here as they relate to aggregation, solubility, and interfacial film formation. [Pg.709]

From Figures 4-6, we can easily observe significant differences for three different types of asphalts. Comparing Figures 7 to 9, all spectra for the three samples are similar, except for the tail part. This may indicate that the difference in the composition of asphaltenes in the three asphalt types is not significant. It is demonstrated that the compositions for the three different types of asphalt differ significantly due to the existing different compositions of asphaltenes which do not dissolve well in solvents. [Pg.46]

The elemental composition of asphaltenes varies in a ratio of C/H of 1.15 0.05%, however, values outside this range are sometimes found, according to Speight (1999 a). [Pg.10]

Table 2. Range and Typical Values of Elemental Composition of Asphaltenes. Table 2. Range and Typical Values of Elemental Composition of Asphaltenes.
However, for the past 30 years fractional separation has been the basis for most asphalt composition analysis (Fig. 10). The separation methods that have been used divide asphalt into operationally defined fractions. Four types of asphalt separation procedures are now in use ( /) chemical precipitation in which / -pentane separation of asphaltenes is foUowed by chemical precipitation of other fractions with sulfuric acid of increasing concentration (ASTM D2006) (2) solvent fractionation separation of an "asphaltene" fraction by the use of 1-butanol foUowed by dissolution of the 1-butanol solubles in... [Pg.366]

Asphaltenes seem to be relatively constant in composition in residual asphalts, despite the source, as deterrnined by elemental analysis (6). Deterrnination of asphaltenes is relatively standard, and the fractions are termed / -pentane, / -hexane, / -heptane, or naphtha-insoluble, depending upon the precipitant used (5,6,49). After the asphaltenes are removed, resinous fractions are removed from the maltenes-petrolenes usually by adsorption on activated gels or clays. Recovery of the resin fraction by desorbtion is usually nearly quantitative. [Pg.367]

Colloidal State. The principal outcome of many of the composition studies has been the delineation of the asphalt system as a colloidal system at ambient or normal service conditions. This particular concept was proposed in 1924 and described the system as an oil medium in which the asphaltene fraction was dispersed. The transition from a coUoid to a Newtonian Hquid is dependent on temperature, hardness, shear rate, chemical nature, etc. At normal service temperatures asphalt is viscoelastic, and viscous at higher temperatures. The disperse phase is a micelle composed of the molecular species that make up the asphaltenes and the higher molecular weight aromatic components of the petrolenes or the maltenes (ie, the nonasphaltene components). Complete peptization of the micelle seems probable if the system contains sufficient aromatic constituents, in relation to the concentration of asphaltenes, to allow the asphaltenes to remain in the dispersed phase. [Pg.367]

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. [Pg.305]

For crude oils C and D, some lighter hydrocarbons are formed during the cracking reactions but the composition of the 210 fraction is hardly modified. In particular, it can be noticed that the asphaltene contents of both of the recovered oils remain high. [Pg.422]

In part II of the present report the nature and molecular characteristics of asphaltene and wax deposits from petroleum crudes are discussed. The field experiences with asphaltene and wax deposition and their related problems are discussed in part III. In order to predict the phenomena of asphaltene deposition one has to consider the use of the molecular thermodynamics of fluid phase equilibria and the theory of colloidal suspensions. In part IV of this report predictive approaches of the behavior of reservoir fluids and asphaltene depositions are reviewed from a fundamental point of view. This includes correlation and prediction of the effects of temperature, pressure, composition and flow characteristics of the miscible gas and crude on (i) Onset of asphaltene deposition (ii) Mechanism of asphaltene flocculation. The in situ precipitation and flocculation of asphaltene is expected to be quite different from the controlled laboratory experiments. This is primarily due to the multiphase flow through the reservoir porous media, streaming potential effects in pipes and conduits, and the interactions of the precipitates and the other in situ material presnet. In part V of the present report the conclusions are stated and the requirements for the development of successful predictive models for the asphaltene deposition and flocculation are discussed. [Pg.446]

A most striking result from the work described above is that the composition of the bottoms product and residues from the dissolution reaction did not depend on the chemical structure of the original coal material only their relative quantities differed. This supports the view of a mechanism involving the stabilisation of reactive fragments rather than an asphaltene-intermediate mechanism. The formation of a carbon-rich condensed material as a residue of the reaction and the fact that hydrogen transfer occurred largely to specific parts of the coal further supports this view. [Pg.254]

Mansuy et al. [97] investigated the use of GC-C-IRMS as a complimentary correlation technique to GC and GC-MS, particularly for spilled crude oils and hydrocarbon samples that have undergone extensive weathering. In their study, a variety of oils and refined hydrocarbon products, weathered both artificially and naturally, were analyzed by GC, GC-MS, and GC-C-IRMS. The authors reported that in case of samples which have lost their more volatile n-alkanes as a result of weathering, the isotopic compositions of the individual compounds were not found to be extensively affected. Hence, GC-C-IRMS was shown to be useful for correlation of refined products dominated by n-alkanes in the C10-C20 region and containing none of the biomarkers more commonly used for source correlation purposes. For extensively weathered crude oils which have lost all of their n-alkanes,it has been demonstrated that isolation and pyrolysis of the asphaltenes followed by GC-C-IRMS of the individual pyrolysis products can be used for correlation purposes with their unaltered counterparts [97]. [Pg.87]

In addition, a method of petroleum classification based on other properties as well as the density of selective fractions has been developed. The method consists of a preliminary examination of the aromatic content of the fraction boiling up to 145°C (295°F), as well as that of the asphaltene content, followed by a more detailed examination of the chemical composition of the naphtha (bp < 200°C < 390°F). For this examination a graph is nsed that is a composite of cnrves expressing the relation among the percentage distillate from the naphtha. [Pg.14]

Petroleum is typically described in terms of its physical properties (such as density and pour point) and chemical composition (such as percent composition of various petroleum hydrocarbons, asphaltenes, and sulfur). Although very complex in makeup, crude can be broken down into four basic classes of petroleum hydrocarbons. Each class is distinguished on the basis of molecular composition. In addition, properties important for characterizing the behavior of petroleum and petroleum products when spilled into waterways or onto land and/or released into the air include flash point, density (read specific gravity and/or API gravity), viscosity, emulsion formation in waterways, and adhesion to soil. [Pg.40]

XANES of Petroleum Residua. On the left side of Figure 1 the sulfur K edge spectra for three different petroleum residua and the asphaltene samples prepared from them are shown. While the absorption spectra all appear to be similar, differences are revealed by examining the third derivatives of the spectra, which are shown on the right side of the figure. All the residua samples appear to contain sulfur bound in sulfidic and thiophenic forms, the amount of sulfidic sulfur increasing from sample 1 to sample 3. The asphaltene samples prepared from residua 2 and 3 also appear to contain both forms. Assuming that the composition of the sulfur... [Pg.128]

In Section II, the nature of the metal compounds in petroleum oils is discussed to establish a basic understanding of the targeted reactants. The chemical composition of the host petroleum and residuum is described, including a discussion of the two classes of metal compounds (1) metal-loporphyrins and (2) nonporphyrin metals. The troublesome asphaltenes will also be described. Comparison is made between the characteristics of vanadium and nickel complexes and their distribution in residua. [Pg.97]

The test methods of interest for the analysis of coal extracts include tests that measure chemical composition. The preeminent test methods are those that are applied to measurement of the asphaltene content. The issue with coal extracts is that the presence of asphaltene constituents in the extracts is solvent dependent. But assuming that a test is necessary to determine that whether asphaltene constituents are or are not present, several test are methods available. [Pg.191]

Product oils from SYNTHOIL runs carried out at 415° and 450° C and 2,000 and 4,000 psi H2 pressures were analyzed with respect to asphaltene and oil content, elementary compositions (C, E, S, N), ash and physical properties (specific gravity and viscosity). Asphaltenes exert a large effect on the viscosity of the product oil, the viscosity increasing exponentially with asphaltene content. Viscosity of product oil is not only dependent on the amount but also on the molecular weight of asphaltenes present. At 415° C, asphaltenes with a molecular weight of 670 are formed and at 450° C asphaltenes with a molecular weight of 460. [Pg.125]

The chemical composition of the heavier feedstocks is complex. Physical methods of fractionation usually indicate high proportions of asphaltenes and... [Pg.103]

The proton nmr spectrum of fraction 2 of the S02 solubles resembles that of asphaltenes as reported by other workers (1). The elemental composition and the GPC size distribution agrees with the values published for coal derived asphaltenes (1,3). Fractions 3 and 4 of the S02-solubles were separated and identified by GC-MS (see Figures 4 and 5). These fractions contain only a small amount of alkanes. The components are listed in Tables I and II. [Pg.244]

Pyrolysis of kerogens and asphaltenes has demonstrated the nature and logic of this conversion sequence (58.63-64). Relative to elemental composition, initial asphaltenes have a much lower atomic O/C ratio, a slightly lower atomic S/C ratio, and almost the same H/C and N/C ratios as their source kerogens (53). [Pg.22]


See other pages where Composition of asphaltenes is mentioned: [Pg.8]    [Pg.24]    [Pg.67]    [Pg.235]    [Pg.47]    [Pg.29]    [Pg.190]    [Pg.8]    [Pg.24]    [Pg.67]    [Pg.235]    [Pg.47]    [Pg.29]    [Pg.190]    [Pg.172]    [Pg.216]    [Pg.422]    [Pg.445]    [Pg.448]    [Pg.455]    [Pg.40]    [Pg.38]    [Pg.316]    [Pg.216]    [Pg.8]    [Pg.141]    [Pg.249]    [Pg.29]    [Pg.54]    [Pg.170]    [Pg.171]    [Pg.44]   
See also in sourсe #XX -- [ Pg.12 ]




SEARCH



Asphaltene

Asphaltenes

Elemental compositions of asphaltene

© 2024 chempedia.info