Nitrogen content asphalt

The composition of crude oil may vary with the location and age of an oil field, and may even be depth dependent within an individual well or reservoir. Crudes are commonly classified according to their respective distillation residue, which reflects the relative contents of three basic hydrocarbon structural types paraffins, naphthenes, and aromatics. About 85% of all crude oils can be classified as either asphalt based, paraffin based, or mixed based. Asphalt-based crudes contain little paraffin wax and an asphaltic residue (predominantly condensed aromatics). Sulfur, oxygen, and nitrogen contents are often relatively higher in asphalt-based crude in comparison with paraffin-based crudes, which contain little to no asphaltic materials. Mixed-based crude contains considerable amounts of both wax and asphalt. Representative crude oils and their respective composition in respect to paraffins, naphthenes, and aromatics are shown in Figure 4.1. 

In the more localized context of the Athabasca deposit, inconsistencies arise presumably because of the lack of mobility of the bitumen at formation temperature (approximately 4°C, 39°F). For example, the proportion of bitumen in the tar sand increases with depth within the formation. Furthermore, the proportion of the nonvolatile asphaltenes or the nonvolatile asphaltic fraction (asphaltenes plus resins) in the bitumen also increases with depth within the formation that leads to reduced yields of distillate from the bitumen obtained from deeper parts of the formation. In keeping with the concept of higher proportions of asphaltic fraction (asphaltenes plus resins), variations (horizontal and vertical) in bitumen properties have been noted previously, as have variations in sulfur content, nitrogen content, and metals content. Obviously, the richer tar sand deposits occur toward the base of the formation, but the bitumen is generally of poorer quality. 

Exponential correlations (E). These correlations have the general form of Equations 12.5 and 12.6. Ng (1997) established various exponential correlations to predict variations of total sulfur, metals (Ni + V), CCR, and nitrogen contents in deasphalted oils (DAO) as a function of the asphalt content (defined by the author as the sum of resins and asphaltenes). The correlation for sulfur (Equation 12.21) shows a moderate value (0.6328), while the Equations 12.22 through 12.24 for metals, CCR, and nitrogen have between 0.8819 and 0.9389. 

All crudes are a variation of the hydrocarbon base CH2. The ultimate composition shows 84 to 86% carbon, 10 to 14% hydrogen, and small percentages of sulfur (0.06 to 2%), nitrogen (2 %), and oxygen (0.1 to 2%). The sulfur content is usually below 1.0% but may be as high as 5.0%. Physically crude oil may be water-white, clear yellowish, green, brown, or black, heavy and thick like tar or asphalt. 

Table II shows the results obtained by extracting several Uinta Basin, Utah outcrops with successive organic solvents. All outcrop samples are fairly low in sulfur, most are quite high in nitrogen, and all have low ratios of vanadium to nickel. Only the Raven Ridge sample, which was collected in a creek bed, has a very large fraction of organic material that is not soluble in heptane Benzene-methanol (1 1) and pyridine did not extract much material from any of these samples, so analytical data from these materials are not included in the table. The asphaltenes extracted from P. R. Spring and Southeast Asphalt Ridge tar sands are quite rich in nickel (5/jtmol/g), and nickel porphyrins are found in the heptane-soluble fractions of these tar sands as well as is the heptane-soluble fraction of Whiterocks tar sands. Crudes derived from nonmarine sources are usually much higher in nickel content than in vanadium content, and the Uinta Basin tar sands deposits are all of lacrustine origin and are of tertiary age.

Generally, most asphalt is 79-88% w/w carbon, 7-13% w/w hydrogen, trace-8% w/w sulfur, 2-8% w/w oxygen, and trace-3% w/w nitrogen.Trace metals such as iron, nickel, vanadium, calcium, titanium, magnesium, sodium, cobalt, copper, tin, and zinc occur in crude oils. Vanadium and nickel are bound in organic complexes and, by virtue of the concentration (distillation) process by which asphalt is manufactured, are also found in asphalt. The catalytic behavior of vanadium has prompted studies of the relation between vanadium content and an asphalt s sensitivity to oxidation (viscosity ratio).The significance of metals in the behavior of asphalts is not yet well understood or defined. 

The inter-molecular interactions are primarily the weak van der Waal s and aromatic 7T bonding dipole-dipole interactions. Flydrogen bonding and acid-base interactions are only prevalent in the heavier materials such as redidual (asphaltic) materials where the nitrogen and oxygen content is high. Processed material has... 

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