Refinery Feedstock Flashcards
What is the density range of crude oils on the API gravity scale?
Crude oils have densities ranging from 0.80 to 1.00, equivalent to 45° to 10° on the API gravity scale.
What are the primary elements found in crude oils and their typical weight percentages?
Carbon (C): 83–87%
Hydrogen (H): 10–14%
Sulfur (S): 0.1–3% (rarely up to 7%)
Nitrogen (N): Mostly < 0.1% (occasionally as high as 2%)
Oxygen (O): Up to 1.5%
What are the major classes of hydrocarbons present in crude oil?
Paraffins (alkanes)
Naphthenes (cycloalkanes)
Aromatics
Cyclopentanes and cyclohexanes
What distinguishes paraffins from olefins structurally?
Paraffins: Contain single bonds only; general formula is
CnH2n+2
.
Olefins: Contain at least one double bond; general formula is
CnH2n
.
Why are olefins generally undesirable in finished petroleum products?
Olefins are reactive due to their double bonds and are prone to oxidation and polymerization.
What is the significance of sulfur content in crude oils?
- Low sulfur crudes: < 1% sulfur in residue
- Medium sulfur crudes: 1–3% sulfur in residue
- High sulfur crudes: > 3% sulfur in residue
Desulfurization is easier for distillates but difficult and expensive for residues.
How does wax content affect the pour point and handling of crude oil?
Crudes with high wax content (5–7%) have higher pour points, causing handling problems.
Such crudes may require heating or dilution with less waxy crudes during transport and storage.
What properties of crude oil indicate suitability for asphalt production?
- A residue with a Watson characterization factor < 11.8.
- API gravity below 35°.
- A difference between the characterization factors of the 750°F fractions of less than 0.15.
What are the common non-hydrocarbons found in crude oils?
Nitrogen compounds (e.g., pyridines, pyrroles).
Oxygen compounds (e.g., naphthenic acids, phenols).
Sulfur compounds (e.g., thiols, thiophenes).
Metals (e.g., vanadium, nickel).
