Asphaltene examples

Another encouraging feature is the use of SAFT-type models in industrial applications. In addition to the asphaltene example noted earlier,work has appeared relevant to refrigeration and catalytic polymerization processes. ... 

Nigam, A. Neurock, M. Klein, M. T., Reconciliation of Molecular Detail and Lumping An Asphaltene Thermolysis Example, In Kinetic and Thermodynamic Lumping of Multicomponent Mixtures, Astarita, G. Sandler, S. I. (Eds.), Elsevier Amsterdam, 1991. Klein, M. T. Neurock, M. Nigam, A. Libanati, C., Monte Carlo Modeling of Complex Reaction Systems An Asphaltene Example, In Chemical Reactions in Complex Mixtures, Sapre, A. V. Krambeck, F. J. (Eds.), Van Nostrand Reinhold N.Y., 1991. 

This technique is used to quantify one or more components in a mixture, i.e., extracting them from mixtures to facilitate their final analysis. An example is that for the asphaltenes, already described in the definition of these components in article 1,2.1. 

An important industrial example of W/O emulsions arises in water-in-crude-oil emulsions that form during production. These emulsions must be broken to aid transportation and refining [43]. These suspensions have been extensively studied by Sjoblom and co-workers [10, 13, 14] and Wasan and co-workers [44]. Stabilization arises from combinations of surface-active components, asphaltenes, polymers, and particles the composition depends on the source of the crude oil. Certain copolymers can mimic the emulsion stabilizing fractions of crude oil and have been studied in terms of their pressure-area behavior [45]. 

Many attempts have been made to characterize the stabiUty of the colloidal state of asphalt at ordinary temperature on the basis of chemical analysis in generic groups. For example, a colloidal instabiUty index has been defined as the ratio of the sum of the amounts in asphaltenes and flocculants (saturated oils) to the sum of the amounts in peptizers (resins) and solvents (aromatic oils) (66) ... 

Binuclear aromatic hydrocarbons are found in heavier fractions than naphtha. Trinuclear and polynuclear aromatic hydrocarbons, in combination with heterocyclic compounds, are major constituents of heavy crudes and crude residues. Asphaltenes are a complex mixture of aromatic and heterocyclic compounds. The nature and structure of some of these compounds have been investigated. The following are representative examples of some aromatic compounds found in crude oils ... 

Residues containing high levels of heavy metals are not suitable for catalytic cracking units. These feedstocks may be subjected to a demetallization process to reduce their metal contents. For example, the metal content of vacuum residues could be substantially reduced by using a selective organic solvent such as pentane or hexane, which separates the residue into an oil (with a low metal and asphaltene content) and asphalt (with high metal content). Demetallized oils could be processed by direct hydrocatalysis. 

Figure 1. An example of a hypotetical structure of asphaltene, among the many suggested, showing their aromatic character.

The precipitation number is often equated to the asphaltene content, but there are several issues that remain obvious in its rejection for this purpose. For example, the method to determine the precipitation number (ASTM D91) advocates the use of naphtha for use with black oil or lubricating oil, and the amount... 

Both XANES and XPS results give the same relative ranking for the thiophenic content of any sample, recognizing the currently established accuracy of 10%. For example, either method confirms that petroleum residuum sample 1 contains the most thiophenic sulfur of those studied, and sample 3 the least. Both methods show that thiophenic sulfur concentrates in the asphaltenes prepared from residua 1 and 3, but not in the asphaltenes from residuum 2. However, the quantitative values are different. 

It has been known for some time that the yields of desirable products from coal liquefaction can be enhanced by dispersing the hydrogenation catalyst into the coal. For example, in the liquefaction of a high volatile bituminous coal, the total conversion to tenzene-soluble material, the asphaltene (hexane-insoluble), and oil yields were all enhanced when the catalyst was impregnated into the coal rather than mixed with the coal as a dry powder (2). In that work, impregnated salts of iron. 

A significant portion of the sulfur- and nitrogen-containing species in crude oil can be found in heterocyclic form within the asphaltene, maltene, and resin compounds. Oxygen-containing heterocycles may also be present. Examples of high-molecular-weight aromatic, resinous, and polar compounds found in crude oil are provided in TABLE 3-1. 

Proton NMR spectra of coal derivatives generally give rise to either broad peaks or complicated multiplets which can be easily divided into band envelopes. For example, the H1 spectrum of a coal-hydrogenation asphaltene (4) consists of three peaks, two of which overlap. A broad peak at lowest field is caused by protons in aromatic and phenolic systems, whereas two higher field peaks are caused by protons bonded to carbons situated o to aromatic rings and those bonded to other nonaromatic carbons, respectively. The ratios of these spectral areas are the same as the ratios of the hydrogens in each of these three hydrogen classes. This accounts for one of the most important characteristics of proton NMR spectra—namely, no calibration data are necessary. 

The results of calculations as illustrated in Example 11-21 should be within 10 percent of laboratory measured values. Better accuracy will be obtained if the heptanes plus fraction is divided into several fractions and the parachor for each fraction obtained from Figure 11-18 according to the molecular weight of the fraction. This is the manner in which the data of Figure 11-18 were obtained. The deviation of the heavier fractions from the line on Figure 11-18 is attributed to the collection of asphaltenes in the heaviest fraction of the liquid.15 The correlation line obviously does not give good values of parachors for this fraction. 

Bitumen asphaltenes undergo a variety of simple chemical conversions. For example, asphaltenes can be oxidized, sulfonated, sulfomethylated, halogenated, and phosphoryl-ated. The net result is the introduction of functional entities into the asphaltene structure which confer interesting properties on the products for which a variety of uses are proposed. 

Halogenation. Halogenation of the asphaltenes—by addition of the halogen to a solution of the asphaltenes in refluxing carbon tetrachloride —occurs readily to afford the corresponding halo derivatives (10). The physical properties of the halogenated materials are markedly different from those of the parent asphaltenes. For example, the unreacted asphaltenes are dark brown, amorphous, and readily soluble in benzene, nitrobenzene, and carbon tetrachloride, but the products are black, shiny, and only sparingly soluble, if at all, in these solvents. 

Other chemical modifications pursued in our laboratories include metallation of the asphaltenes or halo-asphaltenes using metal or metallo-organics followed by, for example, carboxylation to the end product. Interaction of the asphaltenes with m-dinitrobenzene affords an oxygen-enriched material which, when treated with hydroxylamine or another amine yields materials containing extra nitrogen. Similarly, reaction of the asphaltenes with maleic anhydride and subsequent hydrolysis yields product bearing carboxylic acid functions. 

Yet the statement of Professor Brill s question indicates the importance of flow assurance, particularly related to hydrates, waxes, scale, corrosion, and asphaltenes, in decreasing order of importance. In the Gulf of Mexico, for example, hydrates are considered to be the largest problem by an order of magnitude relative to the others. 

Upgrading of heavy oils and residua can be designed in an optimal manner by performing selected evaluations of chemical and structural features of these heavy feedstocks (Schabron and Speight, 1996). The evaluation schemes do not need to be complex, but must focus on key parameters that affect processability. For example, the identification of the important features can be made with a saturates-aromatics-resins-asphaltene separation (Chapter 3). Subsequent analy-... 

For example, if the precipitation method (deasphalting) involves the use of a solvent and a residuum and is essentially a leaching of the heavy oil from the insoluble residue, this process may be referred to as extraction. However, under the prevailing conditions now in laboratory use, the term precipitation is perhaps more correct and descriptive of the method. Variation of solvent type also causes significant changes in asphaltene yield. The contact time between the... 

After removal of the asphaltene fraction, further fractionation of petroleum is also possible by variation of the hydrocarbon solvent. For example, liquehed gases, such as propane and butane, precipitate as much as 50% by weight of the residuum or bitumen. The precipitate is a black, tacky, semisolid material, in contrast to the pentane-precipitated asphaltenes, which are usually brown, amorphous solids. Treatment of the propane precipitate with pentane then yields the insoluble brown, amorphous asphaltenes and soluble, near-black, semisolid resins, which are, as near as can be determined, equivalent to the resins isolated by adsorption techniques. 

There is also the distinct possibility that there will be some reactions that occur almost immediately with the onset of heating. Such reactions will most certainly include the elimination of carbon dioxide from carboxylic fragments and, perhaps, even intermolecular coupling through phenolic moieties. There may even be inherent reactions that occur almost immediately. In other words, these are reactions that are an inevitable consequence of the nature of the asphaltene. An example of such reactions is the rapid aromatization of selected hydroaromatic rings to create a more aromatic asphaltene. 

An example of how feedstock composition can influence the variation in product distribution and quality comes from application of the ABC (asphaltene bottoms cracking) hydrocracking process to different feedstocks (Tables 6-18, 6-19, 6-20, and 6-21) (Takeuchi et al., 1986 Komatsu et al., 1986). A further example of variations in product distributions from different feedstocks comes from the Mild Resid Hydrocracking (MRH) process (Table 6-22 Figures 6-14 and 6-15) (Sadhukhan et al., 1986). In addition, different processes will produce variations in the product slate from any one particular feedstock (Figure 6-14) and the feedstock recycle option adds another dimension to variations in product slate (Tables 6-23 and 6-24) (Munoz et al., 1986). 

Figure 5. Proposed structures of alkylthiophene moieties in kerogens and asphaltenes and their presumed flash pyrolysis products. Examples are give for alkylthiophene moieties with (a) linear, (b) isoprenoid, (c) branched and (d) steroidal side-chain carbon skeletons. Carbon skeletons are indicated with bold lines.

Disclaimer As in all theoretical variable determinations, these equations presented for Du calculation are subject to field-test verification. Equations (4.14) and (4.16) are not presented as being infallible or able to predict accurately every case of particle size with a given medium viscosity. For example, a crude with a high asphaltene content should be field tested before a final design for construction is issued on the basis of these equations. Small asphaltene crude contents (less than 2%) were used in deriving Eq. (4.16). More tests are needed for foam-liquid separations. Readers and users of this criterion, can perhaps contribute more data, and I indeed solicit such contributions of better methods and data as you may discover. 

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