The composition of crude oil varies according to where it was obtained. This largely has to do with the type of ground in which the oil was formed, and what contaminants were present and in what relative concentrations. In addition to color variations, there are also various contaminant levels and various flowing properties. Variations aside, crude oil, on average, has the composition shown in Table 2 - 1, Crude Oil Composition (wt%).
Carbon (C) 84-87 Hydrogen (H) 11-14 Sulfur (S) 0.1-4.5+ Nitrogen (N) 0.01-0.8+ Metals 0.0-0.01 Crude oil is comprised of: - Paraffins
- Oleffins
- Naphthenes
- Aromatics
- Paraffins (Alkanes) are single bonded hydrocarbons
- Name ending in – ane
- Examples are propane, butane, iso-butane, and octane
- Chemical Symbols : CnH2n+2
- Ranging from C1 to C50+
Olefins are double bonded hydrocarbons. This double bond occurs between carbon atoms. It is weaker than a single bond, and is therefore subject to reactions that eliminate the double bond.
- The chemical symbol for olefins with one double bond is CnH2n.
- The chemical names for olefins end in –ene.
- An olefin is not a saturated molecule, in that it is lacking some hydrogen due to the double bond
- Symbol - CnH2n
- Ringed saturated hydrocarbons
- May have one ring or several combined
- May contain impurities such as Nitrogen (N) and Sulfur (S)
- Benzene precursors in catalytic reformer
- About 100% of cyclohexane and 50% of methylcyclopentane are converted to Benzene in the reformers.
Aromatics are widely used in the chemical industry. However, we need to minimize them in the gasoline pool. They are detrimental to distillate product properties.
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